CA2125468C - Method of selectively reducing spectral components in a wideband radio frequency signal - Google Patents
Method of selectively reducing spectral components in a wideband radio frequency signalInfo
- Publication number
- CA2125468C CA2125468C CA002125468A CA2125468A CA2125468C CA 2125468 C CA2125468 C CA 2125468C CA 002125468 A CA002125468 A CA 002125468A CA 2125468 A CA2125468 A CA 2125468A CA 2125468 C CA2125468 C CA 2125468C
- Authority
- CA
- Canada
- Prior art keywords
- threshold value
- spectral peaks
- notch filter
- notch
- spectral
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000003595 spectral effect Effects 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract 28
- 238000001914 filtration Methods 0.000 claims abstract description 6
- 238000001228 spectrum Methods 0.000 claims description 12
- 239000000969 carrier Substances 0.000 claims description 11
- 230000001413 cellular effect Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- SVTBMSDMJJWYQN-UHFFFAOYSA-N 2-methylpentane-2,4-diol Chemical compound CC(O)CC(C)(C)O SVTBMSDMJJWYQN-UHFFFAOYSA-N 0.000 description 1
- BSFODEXXVBBYOC-UHFFFAOYSA-N 8-[4-(dimethylamino)butan-2-ylamino]quinolin-6-ol Chemical compound C1=CN=C2C(NC(CCN(C)C)C)=CC(O)=CC2=C1 BSFODEXXVBBYOC-UHFFFAOYSA-N 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
- H04B1/1036—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H17/00—Networks using digital techniques
- H03H17/02—Frequency selective networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
- H04B2001/1063—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal using a notch filter
Abstract
A method of selectively reducing a magnitude of spectral components of a wideband analog radio frequency (RF) signal at an input to an analog-to-digital (A/D) converter is provided. The method includes the steps of digitizing the input to the A/D converter, analyzing the digitized inputs for relatively large spectral peaks, and notch filtering the relatively large peaks to a threshold value.
Description
212546~
: .. . .
MElHOD OF SELECTIVELY REDUCING SPEGTRAL COMPONENTS ~ i IN A WIDEBAND RADIO FREQUENCY SIGNAL
Field of the Invention The field of the invention relate-~ to communication systems and in particular to digital communication 1 0 systems.
Background of the Invention Digital recaivera of radio frequency (RF) signals are known. Such ~caivers, typically, recaive a signal under a analog format, frequency l.d, slale the signal to a ~ -b~seb~d using a Iccal oscillator, filter out unwanted -~
signals using a band~,ass filter (BPF), and convert to a digital format using a analog-to-digital (A~D) converter. ~ ~-2 0 Signal reco~, ~. y following conversion into a digital format typically occurs within a digital signal p-ucessor (DSP) i such as the Motorola 56000 DSP.
Where a group of signals on ~ ~enl ch~nnels are to ' ~' be recov~r~ within a wideband .ecaiver (e.g., within a cellular base station) a local oscillator frequency is chosen to lldnsldt~ the channel group to a low enough frequency range to be uti' ~9~1 by the following stages and a BPF chosen of sufficient bandwidth to pass a spe~ld containing the channel group. Conversion of most or all of the channel group to a digital format typically occurs - ~-within a single A/D with channel sep,.ralion and recovery ' after convera;on prucae-l;ng, after further prûcessin~
under a parallel format in separale DSPs.
While the ,eco~.ery of channel groups using a single -A/D comrerler works well, and at a significant cost advantag~, difficul~ies are often expe- ienced relative to the dynamic range pru-,rWe~ by AlDs over an input signal range. The limited dynamic range of the best of today's 212~468 AJD converters is insufficient to accommodate the largest possible input signals that may occur, without limiting, while simultaneously accomodating the smallest usable input signals in a real system. Where the 5 magnitude of one or more signals of a signal group is significantly larger than others in the group, the larger signal may act to ~blind~ the AID to the lower level signals within the group. Where gain control is utilized to reduce limiting, the re~ltlced gain also decreases a signal 10 to noise ratio of lower level signals. Re~use of the importance of digital communication systems, a need exists for a means of accG~ daling signal groups having large dynamic ranges without limiting the A/D converter or reducing the signal to noise ratio of lower level signals Summary of the Invention A IllelllGJ of selectively reducing a l-.agr,ilude of spe~t,al c~,--ponerl~ of a w:debafid analog radio frequency (RF) signal at an input to an analog-to-digital (AJD) converter is proJideJ. The IlleUIGd includes the steps of digitizing the input to the A/D com~e t~.r, analyLing the digitized inputs for relatively large spect.al peaks, and ~ -notch filtering the relatively large peaks to a threshold -;
25 value.
:
Brief Description of the Drl~ ings FIG. 1 is a block diagram of a digital receiver in accordance with the invention.
FIG. 2 is a block diagram of an A/D and notch filter assembly in accordance with the invention.
FIG. 3 is a graphical re~cresenldliGI- of four radio frequency channels in the time d~,.,ain after a fast fourier transformation.
: .~
: :
2125468 :-FIG. 4 is a graphical ~epresenlalion of a carrier to be notch filtered in accordance with the invention. -; - ~-~
-Detailed Desc,iption of the Preferred Embodiment The solution to the problem of accGI-.,..GLlling signal groups having large dynamic ranges within a radio 10 frequency bros~band recaivar and A/D converter lies, conceptually, in i~JE. lif~ing and notch ~illerin~ the larger signals without ~re-,1ing the lower level signals.
Iden~iIication of larger signals may be accG~Iplish~d by - ; ~
converting an output signal of an A/D converter from the - ~- -time domain to the frequency cl~.. ,ain (e.g., by fast fourier -~
trans~r.. ,aliGn) and comparison with a lhreshold Areas -of the frequency d~ ain lopresentation of the output - ---~
signal id6llti~i6d as exceeding the lhle~hold are then used ~ r to notch filter a cor-esporidi,)g spectra within the frequency domain. A control voltage of the notch filter may then be swept through the kJentiri6d sp~1-a to fine tune the notch filter.
FIG. 1 is a brosl~l,antl recaivor 10 for simultaneous ~ceptiGn of a number of radio frequency channels (e.g., ~ ~ -within a cellular base station). Within the ~ceiver 10 a signal feceivod by an antenna 11 is mixed with an output of a local osc;"~tor, unwanted frequencies are filbred out in a banJpass filter (BPF) 13 and the output applied to an AID convert~r 14. Individual chann~ls are then isol~t~J
30 for t-dns---ission to a subscribar in parallel digital si~nal p(ocessGra (DSPs) (e.g., a Motorola 56000 DSP) or other similar hardware~
FIG. 2 is a block diagram of the A/D converter and notch filter 14 in accordance with an embocli~ent of the 35 invention. Include~ within the AID converter and notch filter 14 is an optional automatic gain control 20, notch filter 21, A/D ~, D/A 23, and DSP 24 (e.g., a Motorola ~
56000 DSP). The optional AGC may be included within the ''~'J
' ~4~ 2125468 A/D converter and notch filter 14 to maintain an input signal level below a maximum level allowable by the A/D
22.
Upon application of a Lro&Jl,and signal from the BPF
13 to the AJD converter and notch filter 14 the A/D 22 samples and converts the b~o~L.and signal to digital samples for application to DSPs 15, 16, and 24. Within -~
DSP 24 the sampled signal is converted from the frequency domain to the time domain using a fast fourier -1 0 transform.
Shown in FIG. 3 is an FFT yfaphical represenlalion of a bru~Land signal applied to the A/D converter and notch -~
filter 14. Include~ within the gr~phical rep~esenlalion of the bro~lbar..J signal are four radio frequency signals 30 1 5 31, 32 and 33 of four radio channels to be decG-Jed by the ~cei~rer 10. Under the im~anlion the amplitude of the signals 30, 31 32 and 33 is cG.-"~ar~l with a threshold -value 35 for a determination of whether the signal 30 31 32, or 33 is to be notch filtered. -- -Under one e--~bod;,--enl of the invention the ll--esh~ld -value 35 (FIG. 4) is determined to be 90~/O of the AID 22 full scale input. Upon determination that a signal 40 has ~xcesded the threshold the DSP 24 doter---ines the location and sp c~.al width of the offending carrier based upon the results of the FFT. Based upon the spectral width, loc~iion and magnitude of the offending carrier the DSP 24 lf~nsFe,s notch filter control para,-,6ters to the notch filter 21. The peak attenuation of the notch fflter is determined by the DSP 24 to be at least the Jifforance between the II.reshold value and the peak of the offending -carrier 40 at a frequency fO.
The bandwidth of the notch (BWfo) with a center -~
frequency fO is ~eler."ined by the spectral width of the --sideband noise around the offending carrier. The bandwidth of the notch is sGl~ct~J to insure that the attenuation outside the offending carrier bandwidth is less than the difference in dB of the s;deb~n.J noise around the ofF6nJing carrier and the thermal noise floor (NF) that ' - 5 is present ahead of the notch filter and A/D. By selecting the notch bandwidth (and therefore its frequency response) in this way, the signal to noise ratio of the other carriers is not degraded beyor,J the value that is 5 inherenl due to the sideband noise of the offendin~
carrier. The peak attenuation and bandwidth are sele~to~
to satisfy the response given in the equalities below, where atten (fl is the attenuation of the notch fitter at a frequency (f), A(f) is the amplitude response of the 10 offending carrier at the frequency (f) and NF is a noise floor (FIG. 4).
Fqu~ffon #1:
atten (f) 2 A(f) - Thresl-old;
for fo-(BWfo/2)~f<fo 1 (BWfo/2) :' F~u~tion #2:
2 0 atten (f) .A(f)-NF;
for fefo-(BWfo/2) or f~fo+(BWfo/2), and --One of the fundamenbl d;sli"guishing factors of the invention is that the notch filter response can be s~lecte~l -to obtain physically realizable values while not causing signiticant signal to noise degrddaiion to the other carriers. A critical factor to accG.nplish this is that the filter response s;~ti~lies F~ tions #1 and 2.
Upon entry of the notch filter parameters into the notch filbr 21, the DSP 24 then begins fine tuning the notch filter 21 by application of a control volt~e through the D/A 23. The control voltage through D/A 23 causes the center point of the notch to change in frequency based upon the magnitude of the control voltage. To fine tune the notch filter 21 to a center fre~uency of the oftdnding carrier 40, the DSP 24 causes the voltage to sweep through an area around the centar point of the oflenJ;ny , :: :
~ -6- 2125~68 carrier 40 while comparing the FFT output of the A/D 22 with the threshold. Deter,.,in~tion of an optimal control point is determined by the DSP 24 to be a point where the or~er,ding carrier amplitude is below the threshold and the 5 notch filter response salisi~es Equation 2.
. ~ . .
; . ., .
: - ~
. ~ ... . .. .... . - . ~ . . .. .
: .. . .
MElHOD OF SELECTIVELY REDUCING SPEGTRAL COMPONENTS ~ i IN A WIDEBAND RADIO FREQUENCY SIGNAL
Field of the Invention The field of the invention relate-~ to communication systems and in particular to digital communication 1 0 systems.
Background of the Invention Digital recaivera of radio frequency (RF) signals are known. Such ~caivers, typically, recaive a signal under a analog format, frequency l.d, slale the signal to a ~ -b~seb~d using a Iccal oscillator, filter out unwanted -~
signals using a band~,ass filter (BPF), and convert to a digital format using a analog-to-digital (A~D) converter. ~ ~-2 0 Signal reco~, ~. y following conversion into a digital format typically occurs within a digital signal p-ucessor (DSP) i such as the Motorola 56000 DSP.
Where a group of signals on ~ ~enl ch~nnels are to ' ~' be recov~r~ within a wideband .ecaiver (e.g., within a cellular base station) a local oscillator frequency is chosen to lldnsldt~ the channel group to a low enough frequency range to be uti' ~9~1 by the following stages and a BPF chosen of sufficient bandwidth to pass a spe~ld containing the channel group. Conversion of most or all of the channel group to a digital format typically occurs - ~-within a single A/D with channel sep,.ralion and recovery ' after convera;on prucae-l;ng, after further prûcessin~
under a parallel format in separale DSPs.
While the ,eco~.ery of channel groups using a single -A/D comrerler works well, and at a significant cost advantag~, difficul~ies are often expe- ienced relative to the dynamic range pru-,rWe~ by AlDs over an input signal range. The limited dynamic range of the best of today's 212~468 AJD converters is insufficient to accommodate the largest possible input signals that may occur, without limiting, while simultaneously accomodating the smallest usable input signals in a real system. Where the 5 magnitude of one or more signals of a signal group is significantly larger than others in the group, the larger signal may act to ~blind~ the AID to the lower level signals within the group. Where gain control is utilized to reduce limiting, the re~ltlced gain also decreases a signal 10 to noise ratio of lower level signals. Re~use of the importance of digital communication systems, a need exists for a means of accG~ daling signal groups having large dynamic ranges without limiting the A/D converter or reducing the signal to noise ratio of lower level signals Summary of the Invention A IllelllGJ of selectively reducing a l-.agr,ilude of spe~t,al c~,--ponerl~ of a w:debafid analog radio frequency (RF) signal at an input to an analog-to-digital (AJD) converter is proJideJ. The IlleUIGd includes the steps of digitizing the input to the A/D com~e t~.r, analyLing the digitized inputs for relatively large spect.al peaks, and ~ -notch filtering the relatively large peaks to a threshold -;
25 value.
:
Brief Description of the Drl~ ings FIG. 1 is a block diagram of a digital receiver in accordance with the invention.
FIG. 2 is a block diagram of an A/D and notch filter assembly in accordance with the invention.
FIG. 3 is a graphical re~cresenldliGI- of four radio frequency channels in the time d~,.,ain after a fast fourier transformation.
: .~
: :
2125468 :-FIG. 4 is a graphical ~epresenlalion of a carrier to be notch filtered in accordance with the invention. -; - ~-~
-Detailed Desc,iption of the Preferred Embodiment The solution to the problem of accGI-.,..GLlling signal groups having large dynamic ranges within a radio 10 frequency bros~band recaivar and A/D converter lies, conceptually, in i~JE. lif~ing and notch ~illerin~ the larger signals without ~re-,1ing the lower level signals.
Iden~iIication of larger signals may be accG~Iplish~d by - ; ~
converting an output signal of an A/D converter from the - ~- -time domain to the frequency cl~.. ,ain (e.g., by fast fourier -~
trans~r.. ,aliGn) and comparison with a lhreshold Areas -of the frequency d~ ain lopresentation of the output - ---~
signal id6llti~i6d as exceeding the lhle~hold are then used ~ r to notch filter a cor-esporidi,)g spectra within the frequency domain. A control voltage of the notch filter may then be swept through the kJentiri6d sp~1-a to fine tune the notch filter.
FIG. 1 is a brosl~l,antl recaivor 10 for simultaneous ~ceptiGn of a number of radio frequency channels (e.g., ~ ~ -within a cellular base station). Within the ~ceiver 10 a signal feceivod by an antenna 11 is mixed with an output of a local osc;"~tor, unwanted frequencies are filbred out in a banJpass filter (BPF) 13 and the output applied to an AID convert~r 14. Individual chann~ls are then isol~t~J
30 for t-dns---ission to a subscribar in parallel digital si~nal p(ocessGra (DSPs) (e.g., a Motorola 56000 DSP) or other similar hardware~
FIG. 2 is a block diagram of the A/D converter and notch filter 14 in accordance with an embocli~ent of the 35 invention. Include~ within the AID converter and notch filter 14 is an optional automatic gain control 20, notch filter 21, A/D ~, D/A 23, and DSP 24 (e.g., a Motorola ~
56000 DSP). The optional AGC may be included within the ''~'J
' ~4~ 2125468 A/D converter and notch filter 14 to maintain an input signal level below a maximum level allowable by the A/D
22.
Upon application of a Lro&Jl,and signal from the BPF
13 to the AJD converter and notch filter 14 the A/D 22 samples and converts the b~o~L.and signal to digital samples for application to DSPs 15, 16, and 24. Within -~
DSP 24 the sampled signal is converted from the frequency domain to the time domain using a fast fourier -1 0 transform.
Shown in FIG. 3 is an FFT yfaphical represenlalion of a bru~Land signal applied to the A/D converter and notch -~
filter 14. Include~ within the gr~phical rep~esenlalion of the bro~lbar..J signal are four radio frequency signals 30 1 5 31, 32 and 33 of four radio channels to be decG-Jed by the ~cei~rer 10. Under the im~anlion the amplitude of the signals 30, 31 32 and 33 is cG.-"~ar~l with a threshold -value 35 for a determination of whether the signal 30 31 32, or 33 is to be notch filtered. -- -Under one e--~bod;,--enl of the invention the ll--esh~ld -value 35 (FIG. 4) is determined to be 90~/O of the AID 22 full scale input. Upon determination that a signal 40 has ~xcesded the threshold the DSP 24 doter---ines the location and sp c~.al width of the offending carrier based upon the results of the FFT. Based upon the spectral width, loc~iion and magnitude of the offending carrier the DSP 24 lf~nsFe,s notch filter control para,-,6ters to the notch filter 21. The peak attenuation of the notch fflter is determined by the DSP 24 to be at least the Jifforance between the II.reshold value and the peak of the offending -carrier 40 at a frequency fO.
The bandwidth of the notch (BWfo) with a center -~
frequency fO is ~eler."ined by the spectral width of the --sideband noise around the offending carrier. The bandwidth of the notch is sGl~ct~J to insure that the attenuation outside the offending carrier bandwidth is less than the difference in dB of the s;deb~n.J noise around the ofF6nJing carrier and the thermal noise floor (NF) that ' - 5 is present ahead of the notch filter and A/D. By selecting the notch bandwidth (and therefore its frequency response) in this way, the signal to noise ratio of the other carriers is not degraded beyor,J the value that is 5 inherenl due to the sideband noise of the offendin~
carrier. The peak attenuation and bandwidth are sele~to~
to satisfy the response given in the equalities below, where atten (fl is the attenuation of the notch fitter at a frequency (f), A(f) is the amplitude response of the 10 offending carrier at the frequency (f) and NF is a noise floor (FIG. 4).
Fqu~ffon #1:
atten (f) 2 A(f) - Thresl-old;
for fo-(BWfo/2)~f<fo 1 (BWfo/2) :' F~u~tion #2:
2 0 atten (f) .A(f)-NF;
for fefo-(BWfo/2) or f~fo+(BWfo/2), and --One of the fundamenbl d;sli"guishing factors of the invention is that the notch filter response can be s~lecte~l -to obtain physically realizable values while not causing signiticant signal to noise degrddaiion to the other carriers. A critical factor to accG.nplish this is that the filter response s;~ti~lies F~ tions #1 and 2.
Upon entry of the notch filter parameters into the notch filbr 21, the DSP 24 then begins fine tuning the notch filter 21 by application of a control volt~e through the D/A 23. The control voltage through D/A 23 causes the center point of the notch to change in frequency based upon the magnitude of the control voltage. To fine tune the notch filter 21 to a center fre~uency of the oftdnding carrier 40, the DSP 24 causes the voltage to sweep through an area around the centar point of the oflenJ;ny , :: :
~ -6- 2125~68 carrier 40 while comparing the FFT output of the A/D 22 with the threshold. Deter,.,in~tion of an optimal control point is determined by the DSP 24 to be a point where the or~er,ding carrier amplitude is below the threshold and the 5 notch filter response salisi~es Equation 2.
. ~ . .
; . ., .
: - ~
. ~ ... . .. .... . - . ~ . . .. .
Claims (21)
1. A method of selectively reducing a bandwidth of spectral components of a wideband multi-carrier analog radio frequency (RF) signal at an input to an analog-to-digital (A/D) converter having digitized samples as an output, such method comprising the steps of:
analyzing the digital samples of the carriers for relatively large spectral peaks; and applying a notch filter to the input of the analog-to-digital (A/D) converter to reduce the relatively large spectral peaks to a threshold value, whereby the notch filter is applied to selected carrier having large spectral peaks exceeding the threshold value and not to carriers having spectral peaks below the threshold value.
analyzing the digital samples of the carriers for relatively large spectral peaks; and applying a notch filter to the input of the analog-to-digital (A/D) converter to reduce the relatively large spectral peaks to a threshold value, whereby the notch filter is applied to selected carrier having large spectral peaks exceeding the threshold value and not to carriers having spectral peaks below the threshold value.
2. The method as in claim 1 wherein the step of applying the notch filter to reduce the spectral peaks to a threshold value further includes the step of limiting a bandwidth of the notch filter to a spectral area related to where an amplitude response of the spectral peaks exceeds a noise floor.
3. The method as in claim 1 wherein the step of analyzing the digital samples further comprising the step of converting the digitized inputs from a time domain to a frequency domain format using a fast fourier transform (FFT) to produce a FFT output.
4. The method as in claim 3 further comprising the step of comparing the FFT output with the threshold value and identifying spectra exceeding the threshold value.
5. The method as in claim 4 further comprising the step of calculating a notch depth and bandwidth based, in part, upon the FFT output and identified spectra.
6. The method as in claim 4 further comprising the step of generating at least one set of notch filter coefficients for the identified spectra.
7. A method of selectively reducing a magnitude of spectral components of a wideband multi-carrier analog radio frequency (RF) signal at an input to an analog-to-digital (A/D) converter having digitized samples as an output, such method comprising the steps of:
a) analyzing the digital samples of the carriers for relatively large spectral peaks;
b) calculating a notch depth and bandwidth required to reduce the relatively large spectral peaks to at least a threshold value;
c) selecting notch filter coefficients, based on the calculated notch depth and bandwidth;
d) applying a notch filter, based on the selected notch filter coefficients, to the carriers analyzed to have relatively large spectral peaks to reduce the relatively large spectral peaks to at least the threshold value; and e) repeating steps (a) through (d).
a) analyzing the digital samples of the carriers for relatively large spectral peaks;
b) calculating a notch depth and bandwidth required to reduce the relatively large spectral peaks to at least a threshold value;
c) selecting notch filter coefficients, based on the calculated notch depth and bandwidth;
d) applying a notch filter, based on the selected notch filter coefficients, to the carriers analyzed to have relatively large spectral peaks to reduce the relatively large spectral peaks to at least the threshold value; and e) repeating steps (a) through (d).
8. The method as in claim 7 wherein the step of applying a notch filter to the carriers analyzed to have relatively large spectral peaks further includes the step of limiting a bandwidth of the notch filter to a spectral area related to where an amplitude response of the spectral peaks exceeds a noise floor.
9. The method as in claim 7 wherein the step of analyzing the digital samples further comprising the step of converting the digitized inputs from a time domain to a frequency domain format using a fast fourier transform (FFT) to produce a FFT output.
10. The method as in claim 9 further comprising the step of comparing the FFT output with the threshold value and identifying spectra exceeding the threshold value.
11. The method as in claim 10 further comprising the step of calculating a notch depth and bandwidth based, in part, upon the FFT output and identified spectra.
12. The method as in claim 10 further comprising the step of generating at least one set of notch filter coefficients for the identified spectra.
13. A method of selectively reducing a magnitude of spectral components of a wideband multi-carrier analog signal at an input to an analog-to-digital (A/D)converter having digitized samples as an output, such method comprising the steps of:
a) characterizing the digital samples using a fast fourier transform (FFT);
b) comparing the characterized digital samples with a threshold to identify spectra of the carriers having a magnitude of a spectral peak exceedinga threshold;
c) calculating a notch depth and bandwidth to reduce the identified spectral peak to at least the threshold;
d) selectively notch filtering the spectral peaks to at least the threshold, whereby notch filtering is applied to the spectral peaks identified as having a magnitude exceeding the threshold; and e) repeating steps (a) through (d).
a) characterizing the digital samples using a fast fourier transform (FFT);
b) comparing the characterized digital samples with a threshold to identify spectra of the carriers having a magnitude of a spectral peak exceedinga threshold;
c) calculating a notch depth and bandwidth to reduce the identified spectral peak to at least the threshold;
d) selectively notch filtering the spectral peaks to at least the threshold, whereby notch filtering is applied to the spectral peaks identified as having a magnitude exceeding the threshold; and e) repeating steps (a) through (d).
14. The method as in claim 13 further comprising the step of generating at least one set of notch filter coefficients for the identified spectra.
15. The method as in claim 13 wherein the step of notch filtering the spectral peaks to a threshold value further includes the step of limiting a bandwidth of the notch filter to a spectral area related to where an amplitude response of the spectral peaks exceeds a noise floor.
16. A method of selectively reducing a magnitude of spectral components of a wideband multi-carrier analog radio frequency (RF) signal at an input to an analog-to-digital (A/D) converter of a cellular base station, the A/D converter having digitized samples as an output, such method comprising the steps of:
analyzing the digital samples of the carriers for relatively large spectral peaks; and applying a notch filter to the input of the analog-to-digital (A/D) converter to reduce the relatively large spectral peaks to a threshold value, whereby the notch filter is applied to selected carriers having large spectral peaks exceeding the threshold value and not to carriers having spectral peaks below the threshold value.
analyzing the digital samples of the carriers for relatively large spectral peaks; and applying a notch filter to the input of the analog-to-digital (A/D) converter to reduce the relatively large spectral peaks to a threshold value, whereby the notch filter is applied to selected carriers having large spectral peaks exceeding the threshold value and not to carriers having spectral peaks below the threshold value.
17. The method as in claim 16 wherein the step of notch filtering the relatively large spectral peaks to a threshold value further includes the step of limiting a bandwidth of the notch filter to a spectral area related to where an amplitude response of the spectral peaks exceeds a noise floor.
18. The method as in claim 16 wherein the step of analyzing the digitized inputs further comprising the step of converting the digitized inputs from a time domain to a frequency domain format using a fast fourier transform (FFT) to produce a FFT output.
19. The method as in claim 18 further comprising the step of comparing the FFT output with the threshold value and identifying spectra exceeding the threshold value.
20. The method as in claim 19 further comprising the step of calculating a notch depth and bandwidth based, in part, upon the FFT output and identified spectra.
21. The method as in claim 19 further comprising the step of generating at least one set of notch filter coefficients for the identified spectra.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US8263193A | 1993-06-28 | 1993-06-28 | |
| US08/082,631 | 1993-06-28 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2125468A1 CA2125468A1 (en) | 1994-12-29 |
| CA2125468C true CA2125468C (en) | 1998-04-21 |
Family
ID=22172372
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002125468A Expired - Fee Related CA2125468C (en) | 1993-06-28 | 1994-06-08 | Method of selectively reducing spectral components in a wideband radio frequency signal |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5519890A (en) |
| CA (1) | CA2125468C (en) |
| SE (1) | SE9402246L (en) |
Families Citing this family (50)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08265205A (en) * | 1995-03-27 | 1996-10-11 | Toshiba Corp | Double super tuner |
| US5758275A (en) * | 1995-09-29 | 1998-05-26 | Motorola, Inc. | Method and apparatus for scheduling adaptation for a notch filter |
| JPH1013260A (en) * | 1996-06-25 | 1998-01-16 | Matsushita Electric Ind Co Ltd | Signal processing circuit |
| US5963856A (en) * | 1997-01-03 | 1999-10-05 | Lucent Technologies Inc | Wireless receiver including tunable RF bandpass filter |
| US6091940A (en) | 1998-10-21 | 2000-07-18 | Parkervision, Inc. | Method and system for frequency up-conversion |
| US7515896B1 (en) | 1998-10-21 | 2009-04-07 | Parkervision, Inc. | Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships |
| US6694128B1 (en) | 1998-08-18 | 2004-02-17 | Parkervision, Inc. | Frequency synthesizer using universal frequency translation technology |
| US6061551A (en) | 1998-10-21 | 2000-05-09 | Parkervision, Inc. | Method and system for down-converting electromagnetic signals |
| US6370371B1 (en) | 1998-10-21 | 2002-04-09 | Parkervision, Inc. | Applications of universal frequency translation |
| US6049706A (en) | 1998-10-21 | 2000-04-11 | Parkervision, Inc. | Integrated frequency translation and selectivity |
| US7236754B2 (en) | 1999-08-23 | 2007-06-26 | Parkervision, Inc. | Method and system for frequency up-conversion |
| US6061555A (en) | 1998-10-21 | 2000-05-09 | Parkervision, Inc. | Method and system for ensuring reception of a communications signal |
| US7039372B1 (en) | 1998-10-21 | 2006-05-02 | Parkervision, Inc. | Method and system for frequency up-conversion with modulation embodiments |
| US6560301B1 (en) | 1998-10-21 | 2003-05-06 | Parkervision, Inc. | Integrated frequency translation and selectivity with a variety of filter embodiments |
| US6813485B2 (en) | 1998-10-21 | 2004-11-02 | Parkervision, Inc. | Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same |
| US6542722B1 (en) | 1998-10-21 | 2003-04-01 | Parkervision, Inc. | Method and system for frequency up-conversion with variety of transmitter configurations |
| US6704549B1 (en) | 1999-03-03 | 2004-03-09 | Parkvision, Inc. | Multi-mode, multi-band communication system |
| US6704558B1 (en) | 1999-01-22 | 2004-03-09 | Parkervision, Inc. | Image-reject down-converter and embodiments thereof, such as the family radio service |
| US6853690B1 (en) | 1999-04-16 | 2005-02-08 | Parkervision, Inc. | Method, system and apparatus for balanced frequency up-conversion of a baseband signal and 4-phase receiver and transceiver embodiments |
| US6879817B1 (en) | 1999-04-16 | 2005-04-12 | Parkervision, Inc. | DC offset, re-radiation, and I/Q solutions using universal frequency translation technology |
| US7065162B1 (en) | 1999-04-16 | 2006-06-20 | Parkervision, Inc. | Method and system for down-converting an electromagnetic signal, and transforms for same |
| US7110444B1 (en) | 1999-08-04 | 2006-09-19 | Parkervision, Inc. | Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments and circuit implementations |
| US7693230B2 (en) | 1999-04-16 | 2010-04-06 | Parkervision, Inc. | Apparatus and method of differential IQ frequency up-conversion |
| US6654427B1 (en) * | 1999-07-28 | 2003-11-25 | Lucent Technologies Inc. | Signal notching system for limiting signal peaks |
| US8295406B1 (en) | 1999-08-04 | 2012-10-23 | Parkervision, Inc. | Universal platform module for a plurality of communication protocols |
| US6373909B2 (en) * | 1999-10-22 | 2002-04-16 | Telefonaktiebolaget Lm Ericsson (Publ) | Communications terminal having a receiver and method for removing known interferers from a digitized intermediate frequency signal |
| DE19962028A1 (en) * | 1999-12-22 | 2001-06-28 | Philips Corp Intellectual Pty | Filter arrangement |
| US7010286B2 (en) | 2000-04-14 | 2006-03-07 | Parkervision, Inc. | Apparatus, system, and method for down-converting and up-converting electromagnetic signals |
| US7454453B2 (en) | 2000-11-14 | 2008-11-18 | Parkervision, Inc. | Methods, systems, and computer program products for parallel correlation and applications thereof |
| US6480709B2 (en) * | 2001-01-19 | 2002-11-12 | Motorola, Inc. | Method for reducing scan time in a radio receiver |
| DE10122748A1 (en) * | 2001-05-10 | 2002-11-14 | Philips Corp Intellectual Pty | Anti-demodulator circuit, filter device and demodulator circuit |
| US7072427B2 (en) | 2001-11-09 | 2006-07-04 | Parkervision, Inc. | Method and apparatus for reducing DC offsets in a communication system |
| US7379883B2 (en) | 2002-07-18 | 2008-05-27 | Parkervision, Inc. | Networking methods and systems |
| US7460584B2 (en) | 2002-07-18 | 2008-12-02 | Parkervision, Inc. | Networking methods and systems |
| WO2004047323A1 (en) * | 2002-11-18 | 2004-06-03 | Koninklijke Philips Electronics N.V. | Automatic gain control using signal and interference power to obtain extended blocking performance |
| US7035614B2 (en) * | 2002-12-13 | 2006-04-25 | Microtune (Texas), L.P. | System and method for discovering frequency related spurs in a multi-conversion tuner |
| US6990327B2 (en) * | 2003-04-30 | 2006-01-24 | Agency For Science Technology And Research | Wideband monolithic tunable high-Q notch filter for image rejection in RF application |
| CN1799203B (en) * | 2003-06-04 | 2010-12-01 | Nxp股份有限公司 | Adaptive intermodulation distortion filter for zero-IF receivers |
| US7783259B2 (en) * | 2004-09-28 | 2010-08-24 | Microtune (Texas), L.P. | System and method of eliminating or minimizing LO-related interference from tuners |
| US7904024B2 (en) * | 2004-09-28 | 2011-03-08 | Zoran Corporation | System and method of eliminating or minimizing Lo-Related interference from tuners |
| US7738610B2 (en) * | 2005-08-31 | 2010-06-15 | Honeywell International Inc. | Method and apparatus for automatic alignment of notch filters |
| US20080117959A1 (en) * | 2006-11-22 | 2008-05-22 | Qualcomm Incorporated | False alarm reduction in detection of a synchronization signal |
| US7986922B2 (en) * | 2006-12-15 | 2011-07-26 | Qualcomm Incorporated | Jammer detection and suppression for wireless communication |
| US20080146184A1 (en) * | 2006-12-19 | 2008-06-19 | Microtune (Texas), L.P. | Suppression of lo-related interference from tuners |
| US7876869B1 (en) | 2007-05-23 | 2011-01-25 | Hypers, Inc. | Wideband digital spectrometer |
| DE102008031643A1 (en) * | 2008-07-04 | 2010-01-07 | Continental Automotive Gmbh | Receiver arrangement, in particular for use in motor vehicles |
| US9008249B2 (en) | 2012-02-10 | 2015-04-14 | Qualcomm Incorporated | Detection and filtering of an undesired narrowband signal contribution in a wireless signal receiver |
| US9065686B2 (en) * | 2012-11-21 | 2015-06-23 | Qualcomm Incorporated | Spur detection, cancellation and tracking in a wireless signal receiver |
| US9319029B1 (en) * | 2015-06-19 | 2016-04-19 | Clover Network, Inc. | System and method for automatic filter tuning |
| US9887787B1 (en) | 2016-12-15 | 2018-02-06 | The Nielsen Company (Us), Llc | Verification of radio station watermarking with software defined radios |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9008613D0 (en) * | 1990-04-17 | 1990-06-13 | Marconi Gec Ltd | Reducing interference in r.f.signals |
| FR2669489B1 (en) * | 1990-11-16 | 1994-09-09 | Thomson Csf | METHOD AND DEVICE FOR RECOGNIZING MODULATIONS. |
| US5321847A (en) * | 1991-07-26 | 1994-06-14 | Motorola, Inc. | Apparatus and method for detecting intermodulation distortion in a radio frequency receiver |
| US5307517A (en) * | 1991-10-17 | 1994-04-26 | Rich David A | Adaptive notch filter for FM interference cancellation |
| US5282023A (en) * | 1992-05-14 | 1994-01-25 | Hitachi America, Ltd. | Apparatus for NTSC signal interference cancellation through the use of digital recursive notch filters |
-
1994
- 1994-06-08 CA CA002125468A patent/CA2125468C/en not_active Expired - Fee Related
- 1994-06-27 SE SE9402246A patent/SE9402246L/en not_active Application Discontinuation
-
1995
- 1995-08-22 US US08/518,127 patent/US5519890A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2125468A1 (en) | 1994-12-29 |
| SE9402246L (en) | 1994-12-29 |
| US5519890A (en) | 1996-05-21 |
| SE9402246D0 (en) | 1994-06-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2125468C (en) | Method of selectively reducing spectral components in a wideband radio frequency signal | |
| CA2117797C (en) | Method and apparatus for receiving electromagnetic radiation within a frequency band | |
| KR100592631B1 (en) | Receiving spread spectrum signals with narrowband interference | |
| US5263048A (en) | Narrow band interference frequency excision method and means | |
| Dardari | Joint clip and quantization effects characterization in OFDM receivers | |
| KR100329673B1 (en) | Method and apparatus for DC offset clearing and automatic gain control in quadrature receivers | |
| US5574750A (en) | Methods and apparatus for detecting a cellular digital packet data (CDPD) carrier | |
| CA2258009C (en) | Dsp implementation of a cellular base station receiver | |
| US7522556B2 (en) | Signal recognition in an on-frequency repeater | |
| US20020197970A1 (en) | Reducing the peak-to-average power ratio of a communication signal | |
| GB2442571A (en) | Spectrum-sensing algorithms and methods | |
| CN1163516A (en) | Automatic gain control circuit for radio receiver | |
| CN1327637A (en) | A device and method for reducing the amplitude of signal | |
| RU2157044C2 (en) | Device and method for enlarging dynamic range of receiver | |
| US6959170B2 (en) | Communications receivers and methods therefor | |
| US6370133B1 (en) | CDMA receiver and method of operation | |
| US6006083A (en) | Tone detection | |
| US20030081706A1 (en) | Noise reduction filtering in a wireless communication system | |
| US6192226B1 (en) | Carrier squelch processing system and apparatus | |
| JP6915525B2 (en) | Channel estimation device and channel estimation method for broadband wireless communication systems | |
| KR20000048583A (en) | Homodyne cellular base station | |
| US8254864B1 (en) | Decreasing user equipment measurement time | |
| US6021156A (en) | Apparatus and method for improving signal-to-jamming ratio in a spread spectrum receiver | |
| US7885355B2 (en) | Multi-dynamic multi-envelope receiver | |
| US7453951B2 (en) | System and method for the transmission of an audio or speech signal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |