TEMPERATURE COMPENSATED AUTOMATIC OUTPUT CONTROL CIRCUITRY FOR RF SIGNAL POWER AMPLIFIERS WITH WIDE DYNAMIC RANGE

CIRCUIT DE COMMANDE DE SORTIE AUTOMATIQUE AVEC COMPENSATION DES EFFETS DUS A LA TEMPERATURE POUR AMPLIFICATEUR DE PUISSANCE RF A GRANDE DYNAMIQUE

English Abstract

Abstract

Improved temperature compensated, automatic output
control (AOC) circuitry for RF signal power amplifiers is
described that maintains the output power within one-half
dB of a selected one of eight power levels varying from
nine milliwatts to five watts, a dynamic range of
twenty-eight dB. The amplification of the RF signal
amplifier is proportional to a drive current signal
provided by a current amplifier. A half-wave rectifier
is coupled to the output of final amplifiers for
generating an output power signal that has a magnitude
proportional to the output power. The half-wave
rectifier is temperature compensated for and biased by a
diode coupled to the rectifier by one resistor and
coupled to supply voltage by another resistor. The
output power voltage is further coupled to an amplifier
having an amplification factor selected by level control
signals. The amplified output power signal is coupled to
a comparator which varies the drive current provided by
the current amplifier in response to the voltage
difference between the amplified output power signal and
a reference voltage.

Claims

Claims

1. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal amp-
lifier at one of a plurality of levels selected by level
control signals from a signal source, the amplification
of the RF signal amplifier being proportional to a drive
current signal provided by current amplifying means, and
the current amplifying means varying the magnitude of the
drive current signal in response to a current control
signal, said control circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is proportional to the magnitude of the RF signal from
the RF signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature;
means coupled to the level control signals for
selecting one of a plurality of amplification factors in
response to the level control signals;
means coupled to the generating means for
amplifying the output power signal by the selected
amplification factor; and
means coupled to the amplifying means for
varying the magnitude of the current control signal in
response to the difference between the magnitude of the
amplified output power signal and a predetermined
magnitude.









2. The control circuitry according to claim 1,
wherein said amplifying means has a preselected amplifica-
tion factor and said selecting means further includes
means coupled to the generating means for attenuating the
output power signal in response to the level control
signals for selecting one of the amplification factors.

3. The control circuitry according to claim 1,
wherein said amplifying means includes first and second
impedance means for determining the amplification factor
of the amplifying means, and wherein said selecting means
further includes means for varying one of the first or
second impedance means in response to the level control
signals for selecting the amplification factor of the
amplifying means.

4. The control circuitry according to claim 1,
wherein said generating means includes means for
half-wave rectifying the RF signal from the RF signal
amplifier to produce the output power signal.

5. The control circuitry according to claim 4,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal and an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of the first diode
means and signal ground; and wherein the compensating
means includes first resistive means having a first
terminal and a second terminal coupled to the anode of
the first diode means, second diode means having an anode
terminal coupled to the first terminal of the first
resistive means and a cathode terminal coupled to signal
ground, and second resistive means having a first
terminal coupled to the first terminal of the first
resistive means and a second terminal coupled to a
voltage signal from a voltage source.






6. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is proportional to the magnitude of the RF signal from
the RF signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature;
means coupled to the generating means and level
control signals for attenuating the output power signal
by an attenuation factor selected by the level control
signals;
means coupled to the attenuating means for
amplifying the attenuated output power signal by a
predetermined amplification factor; and
means coupled to the amplifying means for
varying the magnitude of the current control signal in
response to the difference between the magnitude of the
amplified output power signal and a predetermined
magnitude.







7. The control circuitry according to claim 6,
wherein said attenuating means includes resistive divider
means including series resistor means coupled between the
generating means and amplifying means and a plurality
shunt resistor means each coupled to the intercoupled
series resistive means and the amplifying means and
selectively coupled to signal ground in response to the
level control signals,

8. The control circuitry according to claim 6,
wherein said amplifying means includes first and second
impedance means for determining the amplification factor
of the amplifying means, and said amplifying means
further includes means for varying one of the first or
second impedance means in response to the level control
signals for selecting the amplification factor of the
amplifying means.

9. The control circuitry according to claim 6,
wherein said generating means includes means for
half-wave rectifying the RF signal from the RF signal
amplifier to produce the output power signal.

10. The control circuitry according to claim 9,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal and an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of he first diode
means and signal ground; and wherein the compensating
means includes first resistive means having a first
terminal and a second terminal coupled to the anode of
the first diode means, second diode means having an anode
terminal coupled to the first terminal of the first
resistive means and a cathode terminal coupled to signal
ground, and second resistive means having a first
terminal coupled to the first terminal of the first

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resistive means and a second terminal coupled to a
voltage signal from a voltage source.



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11. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature and coupled to the level control signals for
adjusting the output power signal by an adjustment factor
selected in response to the level control signals; and
means responsive to the magnitude of the
compensated and adjusted output power signal for
producing the current control signal.




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12. The control circuitry according to claim 11,
wherein said compensating and adjusting means includes
means responsive to the level control signals for
selecting one of a plurality of adjustment factors.

13. The control circuitry according to claim 11,
wherein said compensating and adjusting means includes
means for attenuating the output power signal in response
to the selected adjustment factor.

14. The control circuitry according to claim 13,
wherein said attenuating means includes resistive divider
means including series resistive means and a plurality of
shunt resistive means each coupled to the series
resistive means and selectively coupled to signal ground
in response to the level control signals.

15. The control circuitry according to claim 11,
further including amplifying means for amplifying the
compensated and adjusted output power signal by a
predetermined amplification factor.

16. The control circuitry according to claim 15,
wherein said amplifying means includes variable impedance
means for determining the amplification factor thereof,
and wherein said control circuitry further includes means
for varying said impedance means in response to the
selected adjustment factor.

17. The control circuitry according to claim 11,
wherein said producing means includes means for varying
the current control signal in response to the difference
between the magnitude of the compensated and adjusted
output power signal and a predetermined magnitude.



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18. The control circuitry according to claim 11,
wherein said generating means includes means for
half wave rectifying the RF signal from the RF signal
amplifier to produce the output power signal.

19. The control circuitry according to claim 18,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal and having an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of the first diode
means and signal ground; and said compensating and
adjusting means further includes first resistive means
having a first terminal and having a second terminal
coupled to the anode of the first diode means, second
diode means having an anode terminal coupled to the first
terminal of the first resistive means and a cathode
terminal coupled to signal ground, and second resistive
means having a first terminal coupled to the first
terminal of the first resistive means and a second
terminal coupled to a voltage signal from a voltage
source.







20. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
cur rent amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature and coupled to the level control signals for
attenuating the output power signal by an attenuation
factor selected by the level control signals; and
means responsive to the magnitude of the
compensated and attenuated output power signal for
producing the current control signal.



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21. The control circuitry according to claimm 20,
wherein said compensating and attenuating means includes
means responsive to the level control signals for
selecting one of a plurality of attenuation factors.

22. The control circuitry according to claim 20,
wherein said compensating and attenuating means includes
resistive divider means including series resistive means
and a plurality of shunt resistive means each coupled to
the series resistive means and selectively coupled to
signal ground in response to the level control signals.

23. The control circuitry according to claim 20,
further including amplifying means for amplifying the
compensated and attenuated output power signal by a
predetermined amplification factor.

24. The control circuitry according to claim 23,
wherein said amplifying means includes variable impedance
means for determining the amplification factor thereof,
and said control circuitry further includes means for
varying said impedance means in response to the selected
attenuation factor.

25. The control circuitry according to claim 20,
wherein said producing means includes means for varying
the current control signal in response to the difference
between the magnitude of the compensated and attenuated
output power signal and the predetermined magnitude.

26. The control circuitry according to claim 20,
wherein said generating means includes means for
half-wave rectifying the RF signal from the RF signal
amplifier to produce the output power signal.


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27. The control circuitry according to claim 26,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal having and an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of the first diode
means and signal ground; and said compensating and
attenuating means further includes first resistive means
having a first terminal and having a second terminal
coupled to the anode of the first diode means, second
diode means having an anode terminal coupled to the first
terminal of the first resistive means and a cathode
terminal coupled to signal ground, and second resistive
means having a first terminal coupled to the first
terminal of the first resistive means and a second
terminal coupled to a voltage signal from a voltage
source.



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28. Amplifying circuitry for producing a plurality
of levels of a radio frequency (RF) signal selected by
level control signals from a signal source, said
amplifying circuitry comprising:
means responsive to a current control signal for
amplifying the RF signal;
means coupled to the amplifying means for
generating an output power signal having a magnitude that
is related to the magnitude of the amplified RF signal
therefrom;
means coupled to the generating means for
compensating the output power signal for variations in
temperature and coupled to the level control signals for
adjusting the output power signal by an adjustment factor
selected by the level control signals; and
means responsive to the magnitude of the
compensated and adjusted output power signal for
producing the current control signal.



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29. The control circuitry according to claim 28,
wherein said compensating and adjusting means includes
means responsive to the level control signals for
selecting one of a plurality of adjustment factors.

30. The control circuitry according to claim 28,
wherein said compensating and adjusting means includes
means for attenuating the output power signal in response
to the selected adjustment factor.

31. The control circuitry according to claim 30,
wherein said attenuating means includes resistive divider
means including series resistive means and a plurality of
shunt resistive means each coupled to the series
resistive means and selectively coupled to signal ground
in response to the level control signals.

32. The control circuitry according to claim 28,
further including amplifying means for amplifying the
compensated and adjusted output power signal by a
predetermined amplification factor.

33. The control circuitry according to claim 32,
wherein said amplifying means includes variable impedance
means for determining the amplification factor thereof,
and wherein said control circuitry further includes means
for varying said impedance means in response to the
selected adjustment factor.

34. The control circuitry according to claim 28,
wherein said producing means includes means for varying
the current control signal in response to the difference
between the magnitude of the compensated and adjusted
output power signal and a predetermined magnitude.








35. The control circuitry according to claim 28,
wherein said generating means includes means for
half-wave rectifying the RF signal from the amplifying
means to produce the output power signal.

36. The control circuitry according to claim 35,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal and having an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of the first diode
means and signal ground; and said compensating and
adjusting means further includes first resistive means
having a first terminal and having a second terminal
coupled to the anode of the first diode means, second
diode means having an anode terminal coupled to the first
terminal of the first resistive means and a cathode
terminal coupled to signal ground, and second resistive
means having a first terminal coupled to the first
terminal of the first resistive means and a second
terminal coupled to a voltage signal from a voltage
source.


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37. Circuitry for controlling the magnitude of a
radio frequency (RF) signal in response to control
signals, comprising:
means, having variable output, for amplifying
the RF signal to an output magnitude;
means for generating an output power signal
having a magnitude related to said RF signal output
magnitude;
means for compensating said output power signal
magnitude for variations in temperature and adjusting
said output power signal by an adjustment factor selected
by the control signals; and
means, responsive to said compensated and
adjusted output power signal, for varying said RF signal
amplifying means output to produce a corresponding
magnitude of the RF signal.




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38. The control circuitry according to claim 37,
wherein said compensating and adjusting means includes
means responsive to the level control signals for
selecting one of a plurality of adjustment factors.

39. The control circuitry according to claim 37,
wherein said compensating and adjusting means includes
means for attenuating the output power signal in response
to the selected adjustment factor,

40. The control circuitry according to claim 39,
wherein said attenuating means includes resistive divider
means including series resistive means and a plurality of
shunt resistive means each coupled to the series
resistive means and selectively coupled to signal ground
in response to the level control signals.

41. The control circuitry according to claim 37,
further including amplifying means for amplifying the
compensated and adjusted output power signal by a
predetermined amplification factor.

42. The control circuitry according to claim 41,
wherein said amplifying means includes variable impedance
means for determining the amplification factor thereof,
and wherein said control circuitry further includes means
for varying said impedance means in response to the
selected adjustment factor.

43. The control circuitry according to claim 37,
wherein said producing means includes means for varying
the current control signal in response to the difference
between the magnitude of the compensated and adjusted
output power signal and a predetermined magnitude.

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44. The control circuitry according to claim 37,
wherein said generating means includes means for
half-wave rectifying the RF signal from the RF amplifying
means to produce the output power signal.

45. The control circuitry according to claim 44,
wherein said half-wave rectifying means includes first
diode means having a cathode terminal and having an anode
terminal coupled to the RF signal, and capacitive means
coupled between the cathode terminal of the first diode
means and signal ground, and said compensating and
adjusting means further includes first resistive means
having a first terminal and having a second terminal
coupled to the anode of the first diode means, second
diode means having an anode terminal coupled to the first
terminal of the first resistive means and a cathode
terminal coupled to signal ground, and second resistive
means having a first terminal coupled to the first
terminal of the first resistive means and a second
terminal coupled to a voltage signal from a voltage
source.



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46. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising.
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature;
means coupled to the level control signals for
adjusting the compensated output power signal by an
adjustment factor selected in response to the level
control signals; and
means responsive to the magnitude of the
adjusted output power signal for producing the current
control signal.







47. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature;
means coupled to the level control signals for
attenuating the compensated output power signal by an
attenuation factor selected by the level control signals;
and
means responsive to the magnitude of the
attenuated output power signal for producing the
current control signal.


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48. Amplifying circuitry for producing a plurality
of levels of a radio frequency (RF) signal selected by
level control signals from a signal source, said
amplifying circuitry comprising:
means responsive to a current control signal for
amplifying the RF signal;
means coupled to the amplifying means for
generating an output power signal having a magnitude that
is related to the magnitude of the amplified RF signal
therefrom;
means coupled to the generating means for
compensating the output power signal for variations in
temperature;
means coupled to the level control signals for
adjusting the compensated output power signal by an
adjustment factor selected by the level control signals;
and
means responsive to the magnitude of the
adjusted output power signal for producing the
current control signal.



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49. Circuitry for controlling the magnitude of a
radio frequency (RF) signal in response to control
signals, comprising:
means, having variable output, for amplifying
the RF signal to an output magnitude;
means for generating an output power signal
having a magnitude related to said RF signal output
magnitude;
means for compensating said output power signal
magnitude for variations in temperature;
means for adjusting said compensated output power
signal by an adjustment factor selected by the control
signals; and
means, responsive to said adjusted output power
signal, for varying said output of said RF signal
amplifying means to produce a corresponding output
magnitude of the RF signal.


28




50. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier and compensating the output power signal
for variations in temperature;
means coupled to the level control signals for
selecting one of a plurality of amplification factors in
response to the level control signals;
means coupled to the generating and compensating
means for amplifying the output power signal by the
selected amplification factor; and
means coupled to the amplifying means for
varying the magnitude of the current control signal in
response to the difference between the magnitude of the
amplified output power signal and a predetermined
magnitude.


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51. The control circuitry according to claim 50,
wherein said amplifying means has a preselected
amplification factor and said selecting means further
includes means coupled to the generating means for
attenuating the output power signal in response to the
level control signals for selecting one of the
amplification factors.

52. The control circuitry according to claim 50,
wherein said amplifying means includes first and second
impedance means for determining the amplification factor
of the amplifying means, and wherein said selecting means
further includes means for varying one of the first or
second impedance means in response to the level control
signals for selecting the amplification factor of the
amplifying means.

53. The control circuitry according to claim 50,
wherein said generating means includes means for
rectifying the RF signal from the RF signal amplifier to
produce the output power signal.

54. The control circuitry according

to claim 53,
wherein said rectifying means includes first diode means
having a cathode terminal and an anode terminal coupled
to the RF signal, and capacitive means coupled between
the cathode terminal of the first diode means and signal
ground; and first resistive means having a first terminal
and a second terminal coupled to the anode of the first
diode means, second diode means having an anode terminal
coupled to the first terminal of the first resistive
means and a cathode terminal coupled to signal ground,
and second resistive means having a first terminal
coupled to the second terminal of the first resistive
means and a second terminal coupled to a voltage signal


from a voltage source thereby supplying a bias for said
first diode means.

55. Control circuitry for maintaining the
magnitude of a radio frequency (RF) signal from an RF
signal amplifier at one of a plurality of levels
selected by level control signals from a signal source,
the amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current
signal in response to a current control signal, said
control circuitry comprising:
means coupled to the RF signal amplifier for generat-
ing an output power signal having a magnitude that
is related to the magnitude of the RF signal from the
RF signal amplifier, and compensating the output power
signal for variations in temperature;
means coupled to the generating and compensating
means for attenuating the output power signal by an
attenuation factor selected by the level control signals;
means coupled to the attenuating means for amplify-
ing the attenuated output power signal by a predeter-
mined amplification factor; and
means coupled to the amplifying means for varying
the magnitude of the current control signal in response
to the difference between the magnitude of the amplified
output power signal and a predetermined magnitude.



31




56. The control circuitry according to claim 55,
wherein said attenuating means includes resistive divider
means including series resistor means coupled between the
generating means and amplifying means and a plurality
shunt resistor means selectively coupled among said
series resistor means, amplifying means, and signal
ground in response to the level control signals.

57. The control circuitry according to claim 56,
wherein said amplifying means includes first and second
impedance means for determining the amplification factor
of the amplifying means, and said amplifying means
further includes means for varying one of the first or
second impedance means in response to the level control
signals for selecting the amplification factor of the
amplifying means.

58. The control circuitry according to claim 55,
wherein said generations means includes means for
rectifying the of signal from the RF signal amplifier to
produce the output power signal.

59. The control circuitry according to claim 58,
wherein said rectifying means includes first diode means
having a cathode terminal and an anode terminal coupled
to the RF signal, and capacitive means coupled between
the cathode terminal of the first diode means and signal
ground; and first resistive means having a first terminal
and a second terminal coupled to the anode of the first
diode means, second diode means having an anode terminal
coupled to the first terminal of the first resistive
means and a cathode terminal coupled to signal ground,
and second resistive means having a first terminal
coupled to the second terminal of the first resistive
means and a second terminal coupled to a voltage signal

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from a voltage source thereby supplying a bias for said
first diode means.



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60. Amplifying circuitry for producing a plurality
of levels of a radio frequency (RF) signal selected by
level control signals from a signal source, said
amplifying circuitry comprising:
means responsive to a current control signal for
amplifying the RF signal;
means coupled to the RF amplifying means for
generating an output power signal having a magnitude that
is related to the magnitude of the amplified RF signal
therefrom and compensating the output power signal for
variations in temperature;
means coupled to the level control signals for
adjusting the output power signal by an adjustment
factor selected by the level control signals;
means coupled to the adjusting means for
amplifying the adjusted output power signal; and
means responsive to the magnitude of the
amplified output power signal for producing the
current control signal.



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61. Circuitry for controlling the magnitude of a
radio frequency (RF) signal in response to control
signal, comprising:
means, having variable output, for amplifying the
RF signal to an output magnitude;
means for generating an output power signal
having a magnitude related to said RF signal output
magnitude and compensating the output power signal for
variations in temperature;
means for adjusting said output power signal by
an adjustment factor selected by the control signals;
means coupled to the adjusting means for
amplifying the adjusted output power signal; and
means, responsive to said amplified output power
signal, for varying said output of said RF signal
amplifying means to produce a corresponding output
magnitude of the RF signal.






62. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from a signal source, the
amplification of the RF signal amplifier being
proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
compensating the output power signal for variations in
temperature; and
means responsive to the magnitude of the output
power signal and the level control signals for producing
the current control signal.


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63. Control circuitry in accordance with claim 62
wherein the control circuitry further comprises means
for amplifying said output power signal.

64. Control circuitry in accordance with claim 62
wherein said means for generating an output power signal
is a first diode rectifier.

65. Control circuitry in accordance with claim 64
wherein said means for compensating the output power
signal further comprises a second diode resistively
coupled to said first diode and a direct current power
source whereby temperature variations in said first diode
are compensated by direct current bias from said second
diode.

66. Control circuitry in accordance with claim 62
wherein said means for producing the current control
signal further comprises means for selecting one of a
plurality of resistance values in an attenuation network
whereby the current control signal is responsive to the
level control signals.

67. Control circuitry in accordance with claim 62
wherein said means for producing the current control
signal further comprises comparing means responsive to
the output power signal for generating the current con-
trol signal.




68. Amplifying circuitry for producing and main-
taining one of a plurality of predetermined levels of
a ratio frequency (RF) signal selected by level control
signals from a signal source, said amplifying circuitry
comprising:
means responsive to a current control signal
for amplifying the RF signal;
means coupled to the amplifying means for
generating an output power signal having a magnitude
that is related to the magnitude of the amplified RF
signal therefrom;
means coupled to the generating means for
compensating the output power signal for variations in
temperature; and
means responsive to the magnitude of the
output power signal and the level control signals for
producing the current control signal.



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69. Amplifying circuitry in accordance with claim
68 wherein the amplifying circuitry further comprises:
means for amplifying said output power signal;
first diode means for rectifying the RF
signal;
second diode means resistively coupled to said
first diode means whereby temperature variations in said
first diode means are compensated by bias from said
second diode means;
means for selecting one of a plurality of
resistance values in an attenuation network whereby the
current control signal is responsive to the level control
signals; and
means for comparing the output power signal to
predetermined magnitude and generating the current
control signal.


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70. Control circuitry for maintaining the magnitude
of a radio frequency (RF) signal from an RF signal
amplifier at one of a plurality of levels selected by
level control signals from signal source, the
amplification of the RF signal amplifier being
propositional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output signal having a magnitude that
is related to the level control signals and the magnitude
of the RF signal form the RF signal amplifier;
means coupled to said generating means for
compensating said said for variations in
temperature; and
means responsive to the magnitude of the output
signal for producing the current control signal.






71. Control circuitry in accordance with claim 70
wherein the control circuitry further comprises means for
amplifying said output signal.

72. Control circuitry in accordance with claim 70
wherein said means for generating an output signal
further comprises a first diode m and rectifier.

73. Control circuitry in accordance with claim 72
wherein said means for compensating said output signal
signal further comprises a second diode means coupled to
said f first diode means
whereby temperature variations in said first diode means
are compensated by direct current bias from said second
diode means.

74. Control circuitry in accordance with claim 70
wherein said means for generating an output signal
further comprises means, responsive to the level control
signals, for selecting one of a plurality of resistance
values in an attenuation network.


41







75. Amplifying circuitry for producing and main-
taining one of a plurality of predetermined levels of
a radio frequency (RF) signal selected by level control
signals from a signal source, said amplifying circuitry
comprising:
means responsive to a current control signal
for amplifying the RF signal;
means coupled to the amplifying means for
generating an output signal having a magnitude that is
related to the level control signals and the magnitude
of the RF signal from the RF signal amplifying means;
means coupled to the generating means for
compensating the output signal for variations in
temperature; and
means responsive to the magnitude of the
compensated output signal for producing the current
control signal.

76. Amplifying circuitry in accordance with
claim 75 wherein the amplifying circuitry further
comprises:
means for amplifying said output signal;
first diode means for rectifying the RF
signal;
second diode means resistively coupled to
said first diode means whereby temperature variations in
said first diode means are compensated by bias from
said second diode means; and
means, responsive to the level control
signals, for selecting one of a plurality of resistance
values in an attenuation network.


42



77. Control circuitry for establishing the
magnitude of a radio frequency (RF) signal from an RF
signal amplifier at one of a plurality of contiguous
levels selected by level control signals from a signal
source, the amplification of the RF signal amplifier
being proportional to a drive current signal provided by
current amplifying means, and the current amplifying
means varying the magnitude of the drive current signal
in response to a current control signal, said control
circuitry comprising:
means coupled to the RF signal amplifier for
generating an output power signal having a magnitude that
is related to the magnitude of the RF signal from the RF
signal amplifier;
means coupled to the generating means for
maintaining the output power signal at a magnitude such
that the RF signal magnitude is held at the selected
level within a predetermined window of accuracy over
variations in temperature; and
means responsive to the magnitude of the output
power signal and the level control signals for producing
the current control signal.


43


78. Control circuitry in accordance with claim 77
wherein the control circuitry further comprises means for
amplifying said output power signal.

79. Control circuitry in accordance with claim 77
wherein said output power signal generating means is a
first diode rectifier.

80. Control circuitry in accordance with claim 77
wherein said means for maintaining the RF signal
magnitude further comprises a second diode resistively
coupled to said first diode and a direct current power
source thereby compensating temperature variations in
said first diode by direct current bias from said second
diode and maintaining the RF signal magnitude at -the
selected level.

81. Control circuitry in accordance with claim 77
wherein said means for producing the current control
signal further comprises means for selecting one of a
plurality of resistors in an attenuation network whereby
the current control signal is responsive to the level
control signal.

82. Control circuitry in accordance with claim 77
wherein said means for producing the current control
signal further comprises means for comparing the output
power signal to a predetermined magnitude and producing
the current control signal.


44

83. Amplifying circuitry for producing a plurality
of contiguous levels of a radio frequency (RF) signal
selected by level control signals from a signal source,
said amplifying circuitry comprising:
an RF amplifier responsive to a current control
signal for amplifying the RF signal;
a rectifier, coupled to said RF amplifier, for
generating an output power signal having a magnitude that
is related to the magnitude of the amplified RF signal;
a thermally variable element, coupled to the
rectifier, for maintaining the output power signal at a
magnitude such that the RF signal magnitude is held at
the selected level within a predetermined window of
accuracy;
an output power signal amplifier, couple to
said half wave rectifier for amplifying and comparing the
output power signal to a reference magnitude to produce
said current control signal; and
an attenuator, coupled to said output power
signal amplifier, for adjusting said current control
signal in accordance with the level control signals.







84. Amplifying circuitry in accordance with claim
83 wherein said thermally variable element further com-
prises a diode resistively coupled to said half wave
rectifier and a direct current power source whereby
temperature variations in said half wave rectifier are
compensated by direct current bias from the diode.

85. Amplifying circuitry in accordance with claim
83 wherein said attenuator further comprises an analog
multiplexer for selecting one of a plurality of
resistance values in response to the level control
signals.



46

Description

~7:~;




TEMPERATURE COMPENSATED AUTOMATIC OUTPUT
CONTROL CIRCUITRY FOR RF SIGNAL POWER AMPLIFIERS
WITH WIDE DYNAMIC RANGE




Background of the Invention

The present invention is related generally to
control circuits or RF signal power amplifiers, and more
particularly to improved, temperature compensated,
automatic output control circuitry for RF signal power
amplifier3.
Prior art power amplifiers typically only have one
output power level. Such power amplifiers were adjusted
during manufacture to the desired output power level. In
some applications, it was desirable to have two power
settingsr a low and a high setting. The RF signal power
amplifier for such applications would ~ave one settin~
for the high power level and another for the low power
level.
More recently, it has become advantageous to reuse
radio channels in some radio communications systems.
Therefore, in order to avoid interference between two RF
signal power amplifiers using the same frequency, it is
desirable to have many different selectable output power
levels. For example, four different power levels are
provided for in the RF signal power amplifier in the
mobile radiotelephone described in Motorola Instruction
Manual No. 68P81039E25, entitled '~Advanced Mobile Phone
System'l, and published by Motorola Service Publications,
'' ~

~%~

-- 2 --

1301 E. Algonquin Road, Schaumburg, IL, 1979. The four
power levels are produced by varying a reference voltage
which is applied to automatic output control circuitry.
However, such automatic output control circuitry cannot
accurately maintain a wide range of power settings in RF
signal power amplifiers operable at several different RF
signal frequencies and subjected to a wide range of
temperatures.

Objects and Summary of the Invention

Accordingly, it is an object of the present
invention to provide, improved temperature compensated,
automatic output control circuitry for RF signal power
amplifiers that accurately maintains over a wide range of
RY signal frequencies and temperatures output power
levels selected from a wide range of power settings.
Brie~ly described; the present invention encompasses
control circuitry ~or maintaining the magnitude of an RF
signal from an RF signal amplifier at one of a plurality
of levels selected by l~vel control signals from a signal
source~ The amplification of the RF signal amplifier is
proportional to a drive current signal provided by a
current amplifier. The current amplifier varies the
magnitude of the drive current signal in response to a
current control signal. The control circuitry further
includes circuitry for generating an output power signal
that has a magnitude proportional to the magnitude of the
RF signal from the RF signal ampli~ier; circuitry for
compensating the output power signal for variations in
temperature; circuitry for selecting one of a plurality
of amplification factors in response to the level control
signals; circuitry for amplifying the output power signal
by the selected amplification factor; and circ~itry for
varying the magnitude of the current control signal in
response to the difference between the ma~nitude of the

~oo~:


amplified output power signal and a predetermined
magnitude.

Brief Descriptions of the Drawings

Figure 1 is a block diagram of an RF signal
amplifier including the automatic output control
circuitry of the present invention.
Figure 2 is a detailed circuit diagram of the
automatic output control circuitry in Figure 1~

Detailed Description of the Preferred Embodiment

Referring to Figure 1, there is illustrated an RF
signal power amplifier that may advantageously utilize
automatic output control (AOC) circuitry embodying the
present invention. An RF signal power amplifier is
typically part of a radio, such as that described in the
aforementioned instruction manual numb~r 68P81039E25,
that includes an RF signal power ~mplifier for amplifying
a modulated RF signal which is radiated by an antenna.
The RF signal power amplifier in Figure 1 includes two
cascaded stages of amplification, drivers 102 and final
amplifiers 104. The output of final amplifier 104 is
coupled by way of isolator 106 and filter 108 to antenna
110. The final amplifiers 104 typically boost the output
power level from approximately one-four~h watt to five or
more watts. The output power level developed by final
amplifiers 104 is proportional to the drive current
applied thereto by AOC circuitry 112.
AOC circuitry 112 in Figure 1 detects the magnitude
of the RF signal from final amplifiers 104 and varies the
drive current applied to final amplifiers 104 for main-
taining the magnitude of the final amplifier output at
one of several predetermined magnitudes selected by a
plurality of AOC signals~ In the preferre~ embodiment,

~2~7~l'


three AOC signals are used to select one of eight differ-
ent output power levels ranging from nine milliwatts to
five watts, a dynamic range of twenty eight dB. The AOC
circuitry of the present invention maintains the output
power level to within plus and minus one-half dB of the
selected level over temperature. Furthermore, the output
power level is also accurately controlled by the unique
AOC circuitry over a wide range of RF signal
frequencies.
Referring to Figure 2, there is illustrated a
detailed circuit diagram of AOC circuitry 112 in Figure
1. Three AOC signals are coupled to analog multiplexer
202 which applies signal ground to one of eight different
resistors 222 and 226 depending on the binary state of
each of the AOC signals. The AOC signals can be provided
by a signal source, such as the radio control circuitry
described in the aforementioned instruction manual number
68P81039E25.
The output from final drivers 104 in Figure 2 is
coupled by capacitor 204 to a half wave rectifier formed
by diode 206 and capacitor 208. The voltage at the anode
of diode 20~ is biased to a predetermined voltage by
means of resistor 210, diode 212 and resistor 214.
According to a feature of the present invention~ diode
212 also compensates for variations in the forward
voltage drop across diode 206 due to temperature.
Furthermore, forward biasing diode 206 allows for a lower
value resistor 215, resulting in improved performance in
high humidity environments. The voltage produced by the
rectifier formed by diode 206 and capacitor 208 varies
from a minimum of one-half volt when the final drivers
104 are operating at the lowest power setting to
approximately fifteen volts when final drivers 104 are
operating at the highest power setting.
The output power voltage from capacitor 208 in
Figure 2 is applied to the plus input of amplifier 220 by



way of resistors 216 and 218. The gain of amplifier 220
is varied by grounding one of the eight resistors 222 and
226 selected by the A~C signals. When resistors 222 are
selected, the gain of amplifier 220 is two, and the
output power voltage is attenuated. When resistors 226
are selected, the yain of amplifier 220 is varied, and
the output power voltage is not attenuated. Analog
multiplexer 202 applies ground to one o~ eight resistors
222 and 226 in response to one of eight binary states
provided by the three AOC signals. Analog multiplexer
202 may be a Motorola type MC14051 CMOS integrated
circuit. The values of resistors 222 and 226 are chosen
so that the output of amplifier 220 will have
substantially the same magnitude for each of the eight
power level settings corresponding to output power
voltages ranging from one-half volt to fifteen volts.
Since the operating voltage of AOC circuitry 112 is eiyht
volts in the preferred embodiment, high output power
voltaqes from approximately two to fifteen volts
corresponding to high power settings are selected by
selectively grounding resistors 222. The attenuation is
provided by a voltage divider formed by resistor 218 and
the grounded resistor 222. Conversely, output power
voltages from approximately one-half to two volts
corresponding to low power settings are selected by
selectively grounding resistors 226. The gain of
amplifier 220 is determined by the feedback resistance
provided by resistor 224 and the parallel resistance of
resistor 228 and the grounded resistor 226. Although the
gain of amplifier 220 has been varied by grounding
resistors 222 and 226, the gain of amplifier 220 could
also be varied by varying the resistance of resistors 224
and 228. Thus, according to an important feature of the
present invention, amplifier 220 either attenuates or
amplifies the output power voltage depending on which of
resistors 222 and 226 is groundedO

~a2~

-- 6 --

The output of amplifier 220 in Figure 2 is applied
to the minus input of comparator 2300 Comparator 230
controls current amplifier ~34 by way of base drive
transistor 235. The drive current signal from current
amplifier 234 is coupled to final amplifiers 104 for
varying the power output of final amplifiers 104. The
power output of final amplifiers 104 is increased as the
drive current signal increases, and vice versa.
The positive input of comparator 230 in Figure 2 is
a reference voltage 232 provided by two resistors and a
potentiometer 238. During manufacture of the RF signal
amplifier, potentiometer 238 is varied to produce the
desired power output from final amplifiers for the
highest power level setting. In the preferred
embodiment, the electrical circuit component values were
selected so that the reference voltage 232 is
approximately four volts. In operation, comparator 230
varies the drive current signal from current amplifier
234 to maintain the magnitude of the output of amplifier
220 substantially the same as the magnitude of the
reference voltage 238.
The loop response time o AOC circuitry 112 is on
the order of one millisecond. The loop turn-on time is
primaril~ determined by the circuitry coupled to the base
of transistor 2360 Power level switching time is
primarily determined by the series-coupled resistor and
capacitor 239 coupled to the negative input of amplifier
230. Thus~ AOC circuitry 112 has both a fast turn-on
time and a fast power level switching time.
In summary, improved AOC circuitry for RF signal
power amplifiers has been described that provides a wide
range of output power settings by varyiny amplification
factors in developing the drive current signal applied to
the amplifier. Furthermore, the AOC circuitry is
temperature compensated so that the selected output power

~2~


level is maintained over a wide range of temperatures.
The improved AOC circuitry of the present invention can
be advantageously utilized in any suitable application
where it is desired to accurately maintain over
temperature and frequency variations the output of an RF
signal power amplifier at a selected one of several
output power levels,