IQ ERROR CORRECTION

CORRECTION D'ERREUR DES SIGNAUX I ET Q

English Abstract

In a radio receiver having first and second mixers that mix a received communication signal to produce quadrature I and Q signals, measuring an output value of the I and Q signals. At a programmed processor: evaluating symmetry in the I and Q signals by calculating a symmetry test value; iteratively testing gain and phase shift correction values by applying the gain and phase shift correction values to the I and Q signals to identify a pair of gain and phase shift correction values that produces an improved symmetry test value; selecting the pair of gain and phase shift correction values; and applying the selected pair of gain and phase shift correction values to the I and Q signals from the first and second mixers. This abstract is not to be considered limiting.

French Abstract

Un récepteur radio comportant un premier et un deuxième mélangeurs qui mélangent un signal de communication reçu en vue de produire des signaux I et Q en quadrature, en mesurant une valeur de sortie des signaux I et Q. Le processeur programmé effectue l'évaluation de la symétrie dans les signaux I et Q en calculant un valeur test de symétrie; teste de manière itérative les valeurs de correction de gain et de changement de phase en appliquant les valeurs de gain et de changement de phase aux signaux I et Q en vue d'identifier une paire de valeurs de correction de gain et de changement de phase qui produit une valeur test de symétrie améliorée; la sélection de la paire de valeurs de correction de gain et de changement de phase et l'application de la paire sélectionnée de valeurs de correction de gain et de changement de phase aux signaux I et Q des premier et deuxième mélangeurs. Le résumé ne doit pas être considéré comme limitatif.

Claims

What is claimed is:
1. A method, comprising:
in a radio receiver having first and second mixers that mix a received
communication signal to produce quadrature I and Q signals, measuring an
output
value of the I and Q signals;
at a programmed processor:
evaluating symmetry in the I and Q signals by calculating a symmetry
test value;
iteratively testing gain and phase shift correction values by applying
the gain and phase shift correction values to the I and Q signals to identify
a
pair of gain and phase shift correction values of the gain and phase shift
correction values that produces an improved symmetry test value;
selecting the pair of gain and phase shift correction values; and
applying the pair of gain and phase shift correction values to the I and
Q signals from the first and second mixers to generate a reduced amplitude
and phase error in the output value of the I and Q signals.
2. The method according to claim 1, where the symmetry test value is equal
to
or proportional to:
<IMG>
where < > means average values.
3. The method according to claim 1, where the symmetry test value is equal
to
or proportional to:
Symmetry test value = <I>2-<Q>2
14

where < > means average values.
4. The method according to claim 1, where the symmetry test value is equal
to
or proportional to:
Symmetry_phase = <I*Q>
where < > means average values.
5. The method according to claim 1, where the gain and phase shift
correction
values are stored state variables that are tested to identify the selected
pair of gain
and phase shift correction values.
6. The method according to claim 1, where the pair of gain and phase shift
correction values are represented in a first matrix and the outputs of the
first and
second mixers are represented by a second matrix, and where gain and phase
shift
correction values are applied to the output values from the first and second
mixers
by performing a matrix multiplication of the first matrix with the second
matrix.
7. A method, comprising:
in a radio receiver having first and second mixers that mix a received
communication signal to produce quadrature I and Q signals, measuring an
output
value of the I and Q signals;
at a programmed processor:
evaluating symmetry in the I and Q signals by calculating a symmetry
test value, where the symmetry test value is equal to or proportional to:
<IMG>
where < > means average values;

iteratively testing gain and phase shift correction values by applying the
gain
and phase shift correction values to the I and Q signals to identify a pair of
gain
and phase shift correction values of the gain and phase shift correction
values that
produces an improved symmetry test value;
selecting the pair of gain and phase shift correction values, where the gain
and phase shift correction values are stored state variables that are tested
to
identify the selected pair of gain and phase shift correction values; and
applying the selected pair of gain and phase shift correction values to the I
and Q signals from the first and second mixers to generate a reduced amplitude
and phase error in the output value of the I and Q signals.
8. The method according to claim 7, where the pair of gain and phase shift
correction values are represented in a first matrix and the outputs of the
first and
second mixers are represented by a second matrix, and where gain and phase
shift
correction values are applied to the output values from the first and second
mixers
by performing a matrix multiplication of the first matrix with the second
matrix.
9. A radio device, comprising:
a radio receiver having first and second mixers that mix a received
communication signal to produce quadrature I and Q signals, the radio receiver
operable to measure an output value of the I and Q signals;
a programmed processor that is programmed to:
evaluate symmetry in the I and Q signals by calculating a symmetry
test value;
iteratively test gain and phase shift correction values by applying the
gain and phase shift correction values to the I and Q signals to identify a
pair
of gain and phase shift correction values of the gain and phase shift
correction values that produces an improved symmetry test value;
select the pair of gain and phase shift correction values for reduced
amplitude and phase error in the output I and Q signals; and
16

apply the selected pair of gain and phase shift correction values to the
I and Q signals from the first and second mixers to generate a reduced
amplitude and phase error in the output value of the I and Q signals.
10. The radio device according to claim 9, where the symmetry test value is
equal to or proportional to:
<IMG>
where < > means average values.
11. The radio device according to claim 9, where the symmetry test value is
equal to or proportional to:
Symmetry_test_value = <I>2 - <Q>2
where < > means average values.
12. The radio device according to claim 9, where the symmetry test value is
equal to or proportional to:
Symmetry_phase = <I*Q>
where < > means average values.
13. The radio device according to claim 9, where the gain and phase shift
correction values are stored state variables that are tested to identify the
selected
pair of gain and phase shift correction values.
14. The radio device according to claim 9, where the pair of gain and phase
shift
correction values are represented in a first matrix and the outputs of the
first and
second mixers are represented by a second matrix, and where gain and phase
shift
17

correction values are applied to the output values from the first and second
mixers
by performing a matrix multiplication of the first matrix with the second
matrix.
15. The radio device according to claim 10, where the gain and phase shift
correction values are stored state variables that are tested to identify the
selected
pair of gain and phase shift correction values.
16. The radio device according to claim 10, where the pair of gain and
phase
shift correction values are represented in a first matrix and the outputs of
the first
and second mixers are represented by a second matrix, and where gain and phase
shift correction values are applied to the output values from the first and
second
mixers by performing a matrix multiplication of the first matrix with the
second
matrix.
17. The radio device according to claim 11, where the gain and phase shift
correction values are stored state variables that are tested to identify the
selected
pair of gain and phase shift correction values.
18. The radio device according to claim 11, where the pair of gain and
phase
shift correction values are represented in a first matrix and the outputs of
the first
and second mixers are represented by a second matrix, and where gain and phase
shift correction values are applied to the output values from the first and
second
mixers by performing a matrix multiplication of the first matrix with the
second
matrix.
19. The radio device according to claim 12, where the gain and phase shift
correction values are stored state variables that are tested to identify the
selected
pair of gain and phase shift correction values.
20. The radio device according to claim 12, where the pair of gain and
phase
shift correction values are represented in a first matrix and the outputs of
the first
18

and second mixers are represented by a second matrix, and where gain and phase
shift correction values are applied to the output values from the first and
second
mixers by performing a matrix multiplication of the first matrix with the
second
matrix.
19

Description

CA 02844218 2014-02-27
IQ ERROR CORRECTION
BACKGROUND
[0001] In radio receivers, IQ errors (or IQ imbalance) can cause the radio
to exhibit a poor signal-to-noise ratio or exhibit errors. As modulation
schemes become more complex utilizing larger numbers of constellation
symbols, the radios become less tolerant of IQ errors. Hence, conventional
techniques that set the radio's operational parameters at the time of
manufacture or at the time of power up are inadequate to achieve adequate
signal-to-noise ratio (SNR) in more complex modulation schemes.
[0002] BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Example embodiments of the present disclosure will be described
below with reference to the included drawings such that like reference
numerals refer to like elements and in which:
[0004] FIG. 1 is block diagram of an example radio transceiver consistent
with certain embodiments.
[0005] FIG. 2 is block diagram of an example of a portion of the radio
receiver of radio 104.
[0006] FIG. 3, which is made up of FIG. 3a and FIG. 3b depicts phase
and gain distortion in the I/Q space.
[0007] FIG. 4 is a depiction of gain and phase error in I/Q space from
which symmetry calculations can be derived.
[0008] FIG. 5 is an example block diagram depicting a mixer model
consistent with the present discussion.
[0009] FIG. 6 is an example block diagram depicting an I/Q correction
matrix.
[0010] FIG. 7 is block diagram of a mixer correction implemented in a

CA 02844218 2014-02-27
radio device in a manner consistent with the present discussion.
[0011] FIG 8 is a flow chart of an example process consistent with the
present teachings.
[0012] DETAILED DESCRIPTION
[0013] For simplicity and clarity of illustration, reference numerals may be
repeated among the figures to indicate corresponding or analogous elements.
Numerous details are set forth to provide an understanding of the
embodiments described herein. The embodiments may be practiced without
these details. In other instances, well-known methods, procedures, and
components have not been described in detail to avoid obscuring the
embodiments described. The invention is not to be considered as limited to
the scope of the embodiments described herein.
[0014] The terms "a" or "an", as used herein, are defined as one or more
than one. The term "plurality", as used herein, is defined as two or more
than two. The term "another", as used herein, is defined as at least a second
or more. The terms "including" and/or "having", as used herein, are defined
as comprising (i.e., open language). The term "coupled", as used herein, is
defined as connected, although not necessarily directly, and not necessarily
mechanically. The term "program" or "computer program" or "application" or
similar terms, as used herein, is defined as a sequence of instructions
designed for execution on a computer system. A "program", or "computer
program", may include a subroutine, a function, a procedure, an object
method, an object implementation, in an executable application, an applet, a
servlet, a source code, an object code, a shared library / dynamic load
library
and/or other sequence of instructions designed for execution on a computer
system. The term "processor", "controller", "CPU", "Computer" and the like as
used herein encompasses both hard programmed, special purpose, general
purpose and programmable devices and may encompass a plurality of such
devices or a single device in either a distributed or centralized
configuration
without limitation.
[0015] Reference throughout this document to "one embodiment", "certain
embodiments", "an embodiment", "an example", "an implementation", "an
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CA 02844218 2014-02-27
example" or similar terms means that a particular feature, structure, or
characteristic described in connection with the embodiment, example or
implementation is included in at least one embodiment, example or
implementation of the present invention. Thus, the appearances of such
phrases or in various places throughout this specification are not necessarily
all referring to the same embodiment, example or implementation.
Furthermore, the particular features, structures, or characteristics may be
combined in any suitable manner in one or more embodiments, examples or
implementations without limitation.
[0016] The term "or" as used herein is to be interpreted as an inclusive or
meaning any one or any combination. Therefore, "A, B or C" means "any of
the following: A; B; C; A and B; A and C; B and C; A, B and C". An exception
to this definition will occur only when a combination of elements, functions,
steps or acts are in some way inherently mutually exclusive.
[0017] This discussion addresses the problem of IQ imbalance (or errors)
within radios. These IQ errors in a transceiver effectively contribute to the
overall error vector magnitude (EVM) and SNR of a transceiver. IQ errors are
usually primarily due to mismatches in the I and Q path in a transceiver and
are generally a function of temperature, gain, and frequency bands/channels.
[0018] As noted above IQ errors (or IQ imbalance) in radio receivers can
cause the radio to exhibit a poor signal-to-noise ratio or exhibit errors. As
modulation schemes become more complex utilizing larger numbers of
constellation symbols, the radios become less tolerant of IQ errors. Hence,
conventional techniques that set the radio's operational parameters at the
time of manufacture or at the time of power up are inadequate to achieve
adequate signal-to-noise ratio (SNR). This problem is most evident when a
particular modulation scheme dictates need for a SNR of greater than about
29 dB.
[0019] This problem is addressed in accord with the present teachings by
changing the phase and gain error in the field in real time using
communication signals rather than artificial test signals. The subset is
measured for the level of radio performance in real time. In this case, the
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CA 02844218 2014-02-27
radio's performance can be a measure of the symmetry of the IQ plot. It
should be noted that ideally all IQ plots are symmetrical about the I and Q -
axis. The level of radio performance can thus be measured in of IQ
symmetry.
[0020] Therefore, in accordance with certain aspects of the present
disclosure, there is provided a method in which a radio receiver having first
and second mixers that mix a received communication signal to produce
quadrature I and Q signals, measuring an output value of the I and Q signals,
a programmed processor is configured to carry out: evaluating symmetry in
the I and Q signals by calculating a symmetry test value; iteratively testing
gain and phase shift correction values by applying the gain and phase shift
correction values to the I and Q signals to identify a pair of gain and phase
shift correction values of the gain and phase shift correction values that
produces an improved symmetry test value; selecting the pair of gain and
phase shift correction values; and applying the pair of gain and phase shift
correction values to the I and Q signals from the first and second mixers to
generate a reduced amplitude and phase error in the output I and Q signals.
[0021] In certain implementations, the symmetry test value is equal to or
abs((.11)¨(QQ))+ abs((IQ)) , where <>
proportional to: Symmetry _test _value =
((II) + (QQ))
means average values. In certain implementations, the symmetry test value
is equal to or proportional to: Symmetry test value = <I>2-<Q>2, where <>
means average values. In certain implementations, the symmetry test value
is equal to or proportional to: Symmetry phase = <I*Q> where <> means
average values. In certain implementations, the gain and phase shift values
are stored state variables that are tested to identify a pair of selected gain
and phase shift correction values of the gain and phase shift correction
values. In certain implementations, the gain and phase shift values are
applied to signals from the first and second mixers by processing with a
matrix multiplication with the selected pair of gain and phase shift
correction
values.
[0022] In another method, there is provided a radio receiver having first
and second mixers that mix a received communication signal to produce
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CA 02844218 2014-02-27
quadrature I and Q signals, measuring an output value of the I and Q signals.
A programmed processor is configured to carry out evaluating symmetry in
the I and Q signals by calculating a symmetry test value, where the
symmetry test value is equal to or proportional to:
abs((11)¨ __________________ WO+ abs((10)
Symmetry _test _value = ,
where <> means average
((11)+(QQ))
values; iteratively testing gain and phase shift correction values by applying
the gain and phase shift values to the I and Q signals to identify a pair of
gain and phase shift correction values of the gain and phase shift correction
values that produces an improved symmetry test value; selecting the
pair of gain and phase shift correction values, where the gain and phase shift
values are stored state variables that are tested to identify the selected
pair
of gain and phase shift correction values; and applying the selected pair of
gain and phase shift correction values to the I and Q signals from the first
and second mixers.
[0023] In certain implementations, the gain and phase shift correction
values are applied to signals from the first and second mixers by processing
with a matrix multiplication with the gain and phase shift errors (pair of
selected gain and phase shift correction values).
[0024] An example radio device has a radio receiver having first and
second mixers that mix a received communication signal to produce
quadrature I and Q signals, measuring an output value of the I and Q signals.
A programmed processor is programmed to: evaluate symmetry in the I and
Q signals by calculating a symmetry test value; iteratively test gain and
phase shift correction values by applying the gain and phase shift values to
the I and Q signals to identify a pair of gain and phase shift correction
values
of the gain and phase shift correction values that produces an improved
symmetry test value; select the pair of gain and phase shift correction
values; and apply the selected pair of gain and phase shift correction values
to the I and Q signals from the first and second mixers to generate a reduced
amplitude and phase error in the output value of the I and Q signals.

CA 02844218 2014-02-27
[0025] In certain implementations, the symmetry test value is equal to or
abs((H)¨ WO+ abs(M)
proportional to: Symmetry _test _value = ((//)-F ,
where <>
means average values. In certain implementations, the symmetry test value
is equal to or proportional to: Symmetry test value = <I>2-<Q>2, where <>
means average values. In certain implementations, the symmetry test value
is equal to or proportional to: Symmetry phase = <I*Q>, where <> means
average values. In certain implementations, the gain and phase shift values
are stored state variables that are tested to identify the selected gain and
phase shift correction values. In certain implementations, the gain and
phase shift values are applied to signals from the first and second mixers by
processing with a matrix multiplication with the identified and selected gain
and phase shift errors. In certain implementations, the gain and phase shift
values are stored state variables that are testedto identify selected gain and
phase shift values. In certain implementations, the gain and phase shift
values are applied to signals from the first and second mixers by processing
with a matrix multiplication with the identified and selected gain and phase
shift errors. In certain implementations, the gain and phase shift values are
stored state variables that are tested to identify the selected gain and phase
shift values. In certain implementations, the gain and phase shift values are
applied to signals from the first and second mixers by processing with a
matrix multiplication with the identified and selected gain and phase shift
errors. In certain implementations, the gain and phase shift values are
stored state variables that are tested to identify the selected gain and phase
shift correction values. In certain implementations, the gain and phase shift
values are applied to signals from the first and second mixers by processing
with a matrix multiplication with the identified and selected gain and phase
shift errors.
[0026] FIG. 1 is an illustration of an example block diagram of a radio
transceiver 104 example. This block diagram is simplified for clarity. In this
example, radio transceiver 104 has a transmitter 150 and a receiver 154 that
are operatively coupled to an antenna 158 for transmission and reception.
Transmitter 150 and receiver 154 are controlled by one or more processors
170 that control operation of the radio and selection of the various state
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CA 02844218 2014-02-27
variables used to define operation of the various circuit elements making up
transmitter 150 and receiver 154. Processor 170 utilizes memory 174 of any
suitable type that stores state variable data 178 as well as various sets of
instructions for control of the transceiver. One example set of instructions
184 implements functions that adjust the state variables used by the radio in
the manner discussed herein in order to improve IQ symmetry.
[0027] With reference to FIG. 2, a block diagram of a portion of the
receiver 154 is depicted. In the embodiment discussed herein, the radio
receiver 154 has a pair of mixers 210 and 214 that produce outputs by
mixing their input signal 218 with local oscillator signals 222 and 226 (which
are 90 degrees out of phase) in order to produce quadrature I and Q output
signals coming from the pair of mixers. These I and Q output signals are a
product of mixing local oscillator signals with the input signal at 218 at
mixers 210 and 214 to translate the I and Q signals down to baseband in a
single conversion and are the signals that are decoded after filtering at low
pass filters 238 and 242. At outputs 230 and 234 the output quadrature
signals are designated I and in
order to indicate that this signal has
magnitude and/or phase errors. While this discussion presumes a single
conversion radio receiver, the present techniques are equally applicable to
multiple conversion receivers.
[0028] In accord with certain implementations, the mixers 210 and 214
may have controllable parameters that can be adjusted directly or indirectly
by a processor 170. Such controllable parameters can have an effect on the
amount of errors in I and Q produced at the output of the mixers and hence
at the output of the filters. Processor 170 operates based on instructions
stored in a memory 174 that includes instructions 184 that estimate the I
and Q errors and helps to minimize such errors. Hence, a method can be
provided to estimate/measure the I and Q errors in the presence of a wanted
signal during operation of the transceiver in the field. By
taking this
measurement, the IQ signal errors as measured by asymmetry of the IQ
signals can be minimized using a closed loop approach.
[0029] In the example transceiver of FIG. 2 it would be desirable for the
signal 230 and the (2 signal 234 to be processed in the radio transceiver in
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CA 02844218 2014-02-27
order to carry out reception of a transmitted communication. Distortions
created within the mixers and filters can cause the magnitude and phase of
the I and .0 signals to deviate from ideal thus reducing the SNR (signal to
noise ratio). As noted above, one measure of this error often shows up as an
error in IQ symmetry.
[0030] In an ideal receiver, the I and Q signals are symmetrical. This is
illustrated in FIG. 3a and Fig. 3b by an ideal IQ plot for a four symbol
system in which the solid dots such as 250 represent ideal locations of the
four symbols in IQ space lying in a perfect circle. When there is gain error,
as depicted in FIG. 3a, the magnitude of the symbols is shifted horizontally
or vertically or both. In this case, this is represented by open dots such as
260 in which the gain in the Q direction is too large in magnitude and the
gain in the I direction is too small in magnitude. In FIG. 3b, the phase error
effects result in a shifting out of some symbols relative to the origin and
shifting in of others. This causes the constellation to again be asymmetrical.
[0031] One method to define Symmetry is as follows, making reference to
FIG. 4:
[0032] Qa=average(Q); % effectively the DC offset of the Q-data over a
number of samples;
[0033] Ia=average(I); % effectively the DC offset of the I-data over a
number of samples;
[0034] Qmaxi+=maxI+(Q)-Qa/2; % ;
[0035] ImaxQ+=maxQ+(i)-Ia/2; % ;
[0036] Qmini+-minI+(Q)-Qa/2; % ;
[0037] IminQ+=minQ+(i)-I12; % ;
[0038] QmõI_=maxI-(Q)-Qa/2; % ;
[0039] ImõQ_=maxQ-(I)-I12; % ;
[0040] Qmini-=minI-(Q)-QaR; % ;
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[0041] IrninQ_=minQ-(I)-Ia/2; % ;
[0042] Norm=max(0
-,..max1-1-/QmaxI-)2+Min(QminI+/QminI-)2+MaX(ImaxQl-,ImaxQ_)2+
Min (Iminc2+/IminQ-)2; % this is normalized maximum ;
[0043] Symmetry_test = (I(0
maxx ,maxI-/QmaxI+) I-Imin(0
-s.minl-/QminI+) 1)2
( I Min(QmaxI-/QmaxI+) I-Imax(0 ( I MaX(ImaxQ-/ImaxQ+)
1-1Min(iminQ-
,IminQ+)()2 (f Min(ImaxQ-rimaxQ+)1 MaX(IminQ-timinQ+) 1)2+ (max(0
-urnaxI-/QmaxI+)-
max(ImaxQ+,ImaxQ-))2;
[0044] Symmetry test= 100*Symmetry_test/Norm; % the units are in
the percentage. Ideally Symmetry_test = 0% .
[0045] Generally speaking, the I and Q data will have an average value
(i.e. the DC offset) and a spread. The standard deviation (or rms values) of
the Q and I data should be equal if the data is symmetrical. This could also
be used as a measure of symmetry; i.e.:
[0046] Symmetry gain = (c02-(002 = <II>-<QQ>
[0047] = <I>2_<Q>2. EQUATION 1
[0048] Where (0)2-(o-Q)2 is the difference in the average value of I and Q
squared.
[0049] Furthermore, ideally the I and Q data should not be correlated.
Therefore another measure of symmetry is given by:
[0050] Symmetry phase = <I*Q> . EQUATION 2
[0051] In each case, the symmetry measurement is fully optimized
(assuming no other distortions) when symmetry_gain and symmetry_phase
are equal to zero.
[0052] Therefore, a complete measure of symmetry (both gain and phase)
is given by (expressed as a percentage):
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abs((I1)¨ WO+ abs((1Q))
[0053] Symmetry _test = ______________________ x100
((II) + (QQ))I 2
[0054] and hence,
abs((11)¨ (QQ))+ abs((IQ))
[0055] Symmetry _test oc EQUATION 3
[0056] Where zero is again the optimum symmetry.
[0057] Hence, in accord with examples consistent with the present
teachings, any of EQUATIONS 1, 2 or 3 can be utilized as a test for
symmetry which can be minimized by variation of state variables to achieve
improvement in IQ error distortion, with EQUATION 3 being the most
comprehensive of the three tests.
[0058] Referring now to FIG,. 5, the IQ imbalance can be modeled as a
gain error E and a phase error that is induced by mismatches in the I and Q
paths of the receiver. In this model, the mixers 210 and 214 are modeled by
ideal mixers with gain stages 212 and 216 having gains 2(1-E/2) and 2(1-
E/2) respectively. The phase shift is modeled in the oscillators as:
[0059] sin(toRF t ¨ 0/2) and
[0060] cos (cot + 0/2).
[0061] The input signal RX is modeled as:
[0062] RX = 1(t) cos to RFt + Q(t) sin (o1õ,,t
[0063] resulting in output signals:
[0064] i = /[1+]¨ Q [1+ -11 g-2 ¨ Q1; and
[0065] (-) = Q[1 ¨ / [1 ¨ '2=2 Q ¨ [Q + 1 Efl .

CA 02844218 2014-02-27
[0066] Knowing this, and referring to FIG. 6, one can devise a signal
processing arrangement 290 in which the error containing I and 0 signals in
the receiver can be corrected. At the output of the mixers (and possibly
filters) the I and 0 signals are processed by the processor 170 to implement
a signal processor with transfer function in the form of a matrix
multiplication
A-1 which is derived from:
47) (/.
[0067] = A ) .
EQUATION 4
Q)
[0068] This can be implemented as shown in FIG. 7 using one or more
programmed processors 170 in which a collection of symbols is analyzed and
the value of one of the symmetry test equations above is tested to ascertain
which stored or derived set of state variables produces a lowest or an
adequately low level of I/Q distortion by virtue of reducing or minimizing the
asymmetry of the I/Q data. This set of state variables E and 0 are then
established for use in processing the I and -0 signals in processor 170 to
implement a signal processor with transfer function in the form of a matrix
multiplication A-1 so as to correct the I and -0 signals to be closer to I and
Q.
As the values of state variables E and 0 are incremented by processor 170,
the value of a symmetry_value is evaluated to determine a minimum value or
a value that is adequately low. The same real time communication signals
and -0 signals can be used repeatedly by processor 170 in doing this
evaluation if desired, or different real time communication signals can be
used for each iteration.
[0069] The example process just described can be expressed in an
example flow chart of a process consistent with certain implementations
shown as process 300 of FIG. 8. Starting at 302, the I and Q values are
evaluated using the currently installed gain and phase shift parameters for
the radio at 306. Then, for a selection of gain and phase values (e.g., all of
the stored possible values, or a subset thereof surrounding the current
values) at 310, a recursive process of evaluation of the symmetry of the I
and Q data at 314 is carried out followed by modification of the gain and
phase again at 318 until the selection of various gain and phase values is
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completed at 322. The same set of I and Q data can be used in each set of
tests if desired when optimizing the symmetry.
[0070] Once the recursive test is completed, the gain and phase values are
selected for improvement in IQ distortion at 326. Correction is then applied
at 330 using the signal processing of 290 as discussed previously. The
process ends at 334, but can be repeated at a later time or at periodic
intervals to assure that IQ error remains acceptable.
[0071] The order in which the operations represented in FIG. 8 may vary
in any operative order. Thus, while the blocks comprising the methods are
shown as occurring in a particular order, it will be appreciated by those
skilled in the art that many of the blocks may be interchangeable and can
occur in different orders than that shown without materially affecting the end
results of the methods.
[0072] The implementations of the present disclosure described above are
intended to be examples only. Those of skill in the art can effect
alterations,
modifications and variations to the particular example embodiments herein
without departing from the intended scope of the present disclosure.
Moreover, selected features from one or more of the above-described
example embodiments can be combined to create alternative example
embodiments not explicitly described herein.
[0073] It will be appreciated that any module or component disclosed
herein that executes instructions may include or otherwise have access to
non-transitory and tangible computer readable media such as storage media,
computer storage media, or data storage devices (removable or non-
removable) such as, for example, magnetic disks, optical disks, or tape data
storage, where the term "non-transitory" is intended only to exclude
propagating waves and signals and does not exclude volatile memory or
memory that can be rewritten. Computer storage media may include volatile
and non-volatile, removable and non-removable media implemented in any
method or technology for storage of information, such as computer readable
instructions, data structures, program modules, or other data. Examples of
computer storage media include RAM, ROM, EEPROM, flash memory or other
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CA 02844218 2014-02-27
memory technology, CD-ROM, digital versatile disks (DVD) or other optical
storage, magnetic cassettes, magnetic tape, magnetic disk storage or other
magnetic storage devices, or any other medium which can be used to store
the desired information and which can be accessed by an application,
module, or both. Any such computer storage media may be part of the
server, any component of or related to the network, backend, etc., or
accessible or connectable thereto. Any
application or module herein
described may be implemented using computer readable/executable
instructions that may be stored or otherwise held by such computer readable
media.
[0074] The present disclosure may be embodied in other specific forms
without departing from its spirit or essential characteristics. The described
embodiments are to be considered in all respects only as illustrative and not
restrictive. The scope of the disclosure is, therefore, indicated by the
appended claims rather than by the foregoing description. All changes that
come within the meaning and range of equivalency of the claims are to be
embraced within their scope.
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Representative Drawing