US5778310A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Co-channel interference reduction
Assignee: Microsoft Technology Licensing LLC
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Filing: 1995-11-30
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Granted: 1998-07-07
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Expires: 2015-11-30
Abstract
Abstract Co-channel interference of a frequency modulated signal represented by complex signal samples is reduced by amplitude limiting each sample and non-linearly filtering the limited samples. The non-linear filter low pass filters the limited samples, multiplies the filtered samples by their complex conjugates, and high pass filters the products to produce resultant signal samples. It also squares the filtered samples, low pass filters the squared samples, multiplies the filtered squared signals by the complex conjugates of the filtered samples, combines the result with said resultant signal samples and the filtered samples, and low pass filters the combined signal to produce samples having reduced co-channel interference. The limiter and non-linear filter can be constituted by a digital signal processor.
Inventors
- 👤 Wen Tong
- 👤 Rui Wang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:51
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/06; H04B1/10; H04B1/12; H04B1/123
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
134 words
A method of reducing co-channel interference of a frequency modulated received signal, having a predetermined signal bandwidth, represented by a complex signal having samples x(k) where k is an integer, comprising the steps of: amplitude limiting each sample to produce a limited sample substantially equal to x(k)/|x(k)|; and non-linearly filtering the limited samples to enhance cancellation of co-channel interference, the step of non-linearly filtering comprising the steps of: producing different derivatives of the limited samples, the different derivatives including a derivative of at least one second or higher order power of the limited samples; combining the different derivatives in a manner to enhance the cancellation of co-channel interference in the combination; and low pass filtering at least one of the derivatives, the limited samples, and the combination in accordance with the predetermined signal bandwidth.
Claim 2
Independent Claim
134 words
A method of reducing co-channel interference of a frequency modulated received signal, having a predetermined signal bandwidth, represented by a complex signal having samples x(k) where k is an integer, comprising the steps of: amplitude limiting each sample to produce a limited sample substantially equal to x(k)/|x(k)|; and non-linearly filtering the limited samples to enhance cancellation of co-channel interference, the step of non-linearly filtering comprising the steps of: producing different derivatives of the limited samples, the different derivatives including a derivative of at least one second or higher order power of the limited samples; combining the different derivatives in a manner to enhance the cancellation of co-channel interference in the combination; and low pass filtering at least one of the derivatives, the limited samples, and the combination in accordance with the predetermined signal bandwidth.
Claim 3
Dependent Claim
36 words
A method as claimed in claim 1 wherein the limited samples are low pass filtered in accordance with the predetermined signal bandwidth to produce filtered samples, and the different derivatives are produced from the filtered samples.
Claim 4
Dependent Claim
22 words
A method as claimed in claim 2 wherein the step of producing different derivatives includes the step of producing squared filtered samples.
Claim 5
Dependent Claim
26 words
A method as claimed in claim 3 wherein the step of producing different derivatives further includes the step of low pass filtering the squared filtered samples.
Claim 6
Dependent Claim
40 words
A method as claimed in claim 4 wherein the steps of producing and combining the different derivatives include the step of forming a product of the low pass filtered, squared filtered samples with a complex conjugate of the filtered samples.
Claim 7
Dependent Claim
49 words
A method as claimed in claim 5 wherein the steps of producing and combining the different derivatives further include the steps of producing a product of the filtered samples with a complex conjugate of the filtered samples and removing d.c. components from the product to produce a resultant signal.
Claim 8
Dependent Claim
81 words
A method as claimed in claim 6 wherein the steps of producing and combining the different derivatives further include the steps of producing a product of the filtered samples, a constant 3, and said resultant signal, forming a difference between this product and a sum of the filtered samples and said product of the low pass filtered, squared filtered samples with the complex conjugate of the filtered samples, and low pass filtering the difference in accordance with the predetermined signal bandwidth.
Claim 9
Dependent Claim
39 words
A method as claimed in claim 7 wherein the step of low ass filtering the squared filtered samples comprises the sequential steps of up-sampling by a factor of 2, low pass filtering, and down-sampling by a factor of 2.
Claim 10
Dependent Claim
22 words
A method as claimed in claim 1 wherein the step of producing different derivatives includes the step of producing squared filtered samples.
Claim 11
Dependent Claim
141 words
A non-linear filter for reducing co-channel interference of a frequency modulated signal having a predetermined signal bandwidth and represented by amplitude limited complex signal samples, the non-linear filter comprising: a first signal path including complex signal processing units arranged to multiply the complex signal samples by their complex conjugates and to high pass filter the products to produce resultant signal samples from which d.c. components are removed; a second signal path including complex signal processing units arranged to produce derivative signal samples of at least one second or higher order power of the complex signal samples; and complex signal combining units arranged to combine the resultant signal samples of the first signal path, the derivative signal samples of the second signal path, and the complex signal samples to produce combined signal samples having less co-channel interference than the complex signal samples.
Claim 12
Dependent Claim
141 words
A non-linear filter for reducing co-channel interference of a frequency modulated signal having a predetermined signal bandwidth and represented by amplitude limited complex signal samples, the non-linear filter comprising: a first signal path including complex signal processing units arranged to multiply the complex signal samples by their complex conjugates and to high pass filter the products to produce resultant signal samples from which d.c. components are removed; a second signal path including complex signal processing units arranged to produce derivative signal samples of at least one second or higher order power of the complex signal samples; and complex signal combining units arranged to combine the resultant signal samples of the first signal path, the derivative signal samples of the second signal path, and the complex signal samples to produce combined signal samples having less co-channel interference than the complex signal samples.
Claim 13
Dependent Claim
32 words
A non-linear filter as claimed in claim 10 and including a low pass filter, having a pass band corresponding to the predetermined signal bandwidth, via which the complex signal samples are supplied.
Claim 14
Dependent Claim
40 words
A non-linear filter as claimed in claim 11 and including a low pass filter, having a pass band corresponding to the predetermined signal bandwidth, arranged to filter the combined signal samples to produce output signal samples of the non-linear filter.
Claim 15
Dependent Claim
64 words
A nonlinear filter as claimed in claim 12 wherein the complex signal processing units of the second signal path include a multiplier arranged to square the complex signal samples, a low pass filter arranged to filter the squared samples, and a multiplier arranged to multiply the filtered squared signals by the complex conjugates of the complex signal samples to produce the derivative signal samples.
Claim 16
Dependent Claim
38 words
A non-linear filter as claimed in claim 13 wherein the complex signal processing units of the second signal path further include a two-times up-sampler preceding the low pass filter and a two-times down-sampler following the low pass filter.
Claim 17
Dependent Claim
40 words
A non-linear filter as claimed in claim 10 and including a low pass filter, having a pass band corresponding to the predetermined signal bandwidth, arranged to filter the combined signal samples to produce output signal samples of the non-linear filter.
Claim 18
Dependent Claim
64 words
A non-linear filter as claimed in claim 10 wherein the complex signal processing units of the second signal path include a multiplier arranged to square the complex signal samples, a low pass filter arranged to filter the squared samples, and a multiplier arranged to multiply the filtered squared signals by the complex conjugates of the complex signal samples to produce the derivative signal samples.
Claim 19
Dependent Claim
38 words
A non-linear filter as claimed in claim 16 wherein the complex signal processing units of the second signal path further include a two-times up-sampler preceding the low pass filter and a two-times down-sampler following the low pass filter.
Claim 20
Dependent Claim
25 words
A non-linear filter as claimed in claim 10 wherein the complex signal processing and combining units are provided as functions of a digital signal processor.
Claim 21
Dependent Claim
71 words
Apparatus for reducing co-channel interference of a frequency modulated received signal, having a predetermined signal bandwidth, represented by a complex signal having samples x(k) where k is an integer, the apparatus comprising: a complex signal limiter arranged to limit each sample to produce a limited sample substantially equal to x(k)/|x(k)|; and a non-linear filter as claimed in claim 11 to which the limited samples are supplied as said complex signal samples.
Claim 22
Dependent Claim
71 words
Apparatus for reducing co-channel interference of a frequency modulated received signal, having a predetermined signal bandwidth, represented by a complex signal having samples x(k) where k is an integer, the apparatus comprising: a complex signal limiter arranged to limit each sample to produce a limited sample substantially equal to x(k)/|x(k)|; and a non-linear filter as claimed in claim 13 to which the limited samples are supplied as said complex signal samples.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-07-06 | 2002-01-05 | 2002-07-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-07-06 | 2006-01-05 | 2006-07-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-07-06 | 2010-01-05 | 2010-07-07 | $7700.00 | Window Closed / Lapsed |