Note: Descriptions are shown in the official language in which they were submitted.
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3~_XGROUND OF THE I~IVENTION
This invention is directed to a parametric
amplifier and in particular to a parametric amplifier ha~ g
a balanced pair of varactor diodes.
Parametric amplifiers having three-frequency paramp
action are usually single diode devices. However these
devices normally operate at low input frequency and narrow
bandwidth. Recently, double-diode parametric amplifiers have
been developed to overcome these limitations to a certain
degree. Such devices include two diodes connected in a
~ack-to-back arrangement or in a parallel arrangement as
described in the following references: "A Broadband
Parametric Amplifier" - J.F. Gittins et al, Int. J. Electron, ;
1968, vol. 24, pp. 333-351; "A Broadband Balanced Idler
Circuit for Parametric Amplifiers" - J. D. Pearson et al,
Radio and Electronic Eng., vol. 27, 1964, p. 331;
I'Bandwidth of a Balanced Micropill-Diode Parametric Amplifier" -
C.S. Aitchison et al, IEEE Trans. MTT, January 1968, pp. 46-47;
"Active Reactance Compensation of Parametric Amplifier"
~20 C. S. Aitchison et al, Electron Letter, April 1968, vol. 5,
no. 7~ pp. 139-140; United States Patent 3,596,197, issued
July 27, 1971 to P. Chorney; United States Patent 3,833,857
:issued September 3, 1974 to J. C. Fletcher; United States
Patent 3,842,359 issued October 15, 1974 to L.E. Dickens; and
United States Patent 3,842,360 issued October 15, 1974 to
L. E. Dickens. ;
SV~IMARY OF T~IE INVENTION
It is therefore an object of this invention to
provide a paxametric amplifier for high frequenc~ input
signals ha~.7ing good bandwldth performance.
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It is another object of this invention to provide
a parametric amplifier which is economic to construct using
MIC technology.
It is a further object of this invention to provide
a parametric amplifier in which idler resonance-frequency of
the diode's assembly may be pretested.
It is another object of this invention to provide
a double-diode parametric amplifier in which each diode may
be independently biased.
It is a further object of this invention to provide
a double-diode parametric amplifier fcr input signals in
the order of 12 giga-hertz. ;
These and other objects are achieved in a parametric
amplifier which structurally includes a conductive base having
a pedestal protruding from the top surface of the base, a non-
conductive ring positioned on the top surface of the base to
form a cavity about the pedestal such that the pedestal is
located to one side o the cavity, a first and second terminal
leading out of the ring wall, and a non-conductive cap
positioned over the ring to enclose the cavity. The para-
metric amplifier circuit includes a first and a second varactor
diode and a capacitor, the first diode, the capacitor and the
second diode being serially connected through the package's
pedestal. A first lead connects the first terminal to
one side of the capacitor and a second lead connects the
second terminal to -the other side of the capacitor.
Structurally the parametric amplifier circuit may
also include a non-conductive stand-off positioned on the
conductive pedestal with the first varactor diode and the
3~ capacitor being located thereon.
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In order to rnake the col~nections between the diodes,
the capacitor and the leads, first and second parallel
conductive tracks are located on the non-conductive stan~-ofr.
The capacitor is connected between these tracks, the firs-
lead is connected to the first track and the second lead is
connected to the second track. The first diode is located on
the first track such that a first diode terminal is connected
directly to the first track, and the second terminal of the
first diode is connected to a third lead which in turn is
connected to the pedestal. The second diode is located on the
base such that a first diode terminal is connected directly
to the base, and the second diode terminal is connected to
a fourth lead which in turn is connected to the second
track. The circuit may further be arranged such that the ~
first diode terminal of the first and second diodes is the '
anode of the diode and the second terminal of the first and
second diode is the cathode of the diode.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings~
Figure 1 is ~ simplified schematic circuit
diagram of the parametric amplifier;
Figure 2 is a top view of the parametric amplifier
structure; and
Figure 3 is a side view of the parametric amplifier
structure.
DESCR rPTION OE' THE PREFERRED EMBODIMF.NT
Figure 1 schematically illustrates the circuit
diagram of the parametric amplifier in accordance with the
present invention. The idler circuit consists of a pair
of varactor diodes 1 and 2 connected back to back with the
anode of diode 1 connectecl to ground via a lead inductance
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3 and the cathode of diode 2 connected directly to ground.
To complete the idler circuit, the cathode of diode 1 is
connected to capacitor 4 which in turn is connected to the
anode o~ diode 2 through a lead inductance 5. The para- ,!
~netric amplifier further includes two inp~t leads represented
by inductors 6 and 7 to which the signal frequency to be
amplified and the pump frequency are applied as indicated
by arrows 8. These same leads 6 and 7 are also used to
obtain the amplified output signal from the amplifier as
lQ indicated by arrows 9. In addition, leads 6 and 7 are used
to couple back-biasing voltages Vl and V2 respectively to
the diodes 1 and 2. .~ .;
The structure of the parametric amplifier is shown
in detail in figure 2 which is a top-view of the amplifier
arrangement and in figure 3 which is a side-view of the
amplifier arrangement with a section of the outer ring cut
away for clarity. Corresponding components in figures 2 and
3 carry identical reference numbers which are the same as the
reference numbers for corresponding components in figure 1.
The amplifier structure is packaged on a unitary :
metal base (pedestal) 10 having a threaded stud 11
projecting from the bottom and a flat surfaced mounting
section 12 on which the components of the amplifier
are fixed. ~rhe mounting section 12 is circular in shape
as seen in figure 2 and further inclv.des a pedestal 13
rising above the mounting sec-tion 12. The metal base may
be made from Kovar and gold plated to assure good
conductivity as the ground terminal. A ceramic ring i4
; is fixed to the base 10 so as to be hermetically sea~ed
~0 and forms an enclosure about the mounting section 12. The
ring 1~ includes two parallel metal strip terminals 15 and 16
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which also may be gold plated Kovar, fixed within recesses
in the ceramic riny 14. The amplifier is hermetically
enclosed by a ceramic cap 17 shown in cross secti~n in
figure 3. The cap 17 has a recess 18 of diameter simila~
to the inside diameter of ring 14 and has further small
recesses 19 and 20 above terminals 15 and 16 to provide
space for connecting leads. A quartz stand-off 21 is located
on the mounting section 12 at the center of the enclosure and
two metallized tracks 22 and 23 are located on the stand-off
1~ 21 substantially parallel to the side of the pedestal 13.
As described with respect to figure 1, the idler
circuit consists of a pair of balanced diodes 1 and 2, a
capacitor 4 and lead inductances 3 and 5. The cathode of ~-
diode 1 is fixed to track 22 and its anode is connected
to grounded pedestal 13 by a lead 3. The cathode of diode 2
is fixed to the mounting surface 12 and its anode is
connected to track 23 by a lead 5. A capacitor 4 is coupled
across tracks 22 and 23 to complete the idler circuit. The
idler circuit is connected to terminals 15 and 16 by leads
6 and 7 which do not form part of the idler circuit.
The diodes 1 and 2 may be GaAs diffused mesa
varactor chips or quasi-planar Schottky varactors. It is
preferred that the diodes be perfectly balanced, however
since they are independently biased, any unbalance may be
adjusted by applying voltages Vl and V2 having a slight
difference in amplitude.
For capacitor 4, a MOS or MNS capacitor chip may
be used, however such a capacitor ~lould have the proble~
of undesirable inductance involved in the contact strip. It
~0 ~ould thus be preferrable to use a thin film parallel-plate
capacltor fabricated as an inte~ral part of the ~uartz
stand-off 21, and rî.etallized tracks 22 and 23.
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The pump frequency, the input signal and the
bias voltage are applied to terminal tabs 15 and 16 in
any conventional manner. The pump frequency and the
input signal are equally apnlied to the terminals lS
and 16 while appropriate bias voltages are applied
independently to terminals 15 and 16.
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