Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS2472798 A
Publication typeGrant
Publication date14 Jun 1949
Filing date29 Nov 1943
Priority date29 Nov 1943
Publication numberUS 2472798 A, US 2472798A, US-A-2472798, US2472798 A, US2472798A
InventorsFredendall Gordon L
Original AssigneeRca Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Low-pass filter system
US 2472798 A
Abstract  available in
Images(1)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Patented June 14, 1949 'time LOW-PASS FILTER SYSTEM Gordon L. Fredendall, Feasterville, to Radio Corporation of America,

of Delaware Pa., assignor a corporation Application November 29, 1943, Serial No. 512,115

(Cl. ri-44) 13 Claims.

This invention relates generally to wave transmission networks and more particularly to adjustable low-pass networks employing a plurality of fixed lter circuits.

l Heretofore, adjustable low-pass filters having a continuously variable cut-off frequency have included a plurality of individually adjustable reactive filter components. Adjustable reactive elements, suitable for low-pass networks, are costly and cumbersome. It also is costly and inconvenient to gang a large number of adjustable reactive elements for convenient unitary adjust-V ment of the cut-off frequency.

The instant invention contemplates broadly converting the currents of one frequency into currents of a higher frequency. The higher frequency currents are applied to a low-pass network employing only two fixed reactive filter networks in combination with two fixed modulators and two adjustable carrier frequency sources such as, for example, thermionic tube oscillators. The two fixed filter networks have frequency band pass characteristics at frequencies related to but appreciably higher than the desired low-pass cutoff frequency. The conversion to higher frequencies reduces the physical size and cost of the filter components.

The signal frequency currents which are to be attenuated are applied to a first carrier frequency from one of the oscillator circuits to provide two equal side bands. The two side bands and the rst carrier frequency are applied to the first filter network to attenuate only the upper side band to the desired low-pass band width. The unequally attenuated side bands and the first carrier are then applied to the second carrier frequency which is selected to be substantially higher than the first carrier frequency. The second fixed filter network has a pass band which attenuates the lower part of the upper band side band to a value substantially equal to the upper part of the upper band side band, thereby providinga high frequency carrier having two side bands each having widths equivalent to the desired low-pass hand. The high frequency modulated carrier is applied to a demodulator or envelope detector to derive the low-pass frequency band desired.

, Among the objects of the invention are to provide an improved method of and means for transmitting a predetermined low-pass frequency band. Another object of the invention is to provide an improved low-pass transmission network employing relatively high frequency band-pass filter netlator will include a works. An additional object of the invention is to provide an improved adjustable low-pass transmission network employing a plurality of fixed band-pass filter networks.

A further object of the invention is to provide an improved adjustable low-pass transmission network employing in combination a plurality of xed filter networks, a plurality of adjustable carrier frequency sources and means for modulating the signal frequencies with the carrier frequency sources to provide the desired low-pass frequency transmission band.

The invention will be further described by reference to the accompanying drawing of which Figure 1 is a schematic circuit block diagram of a preferred embodiment, Figure 2 is a family of graphs indicating the operation of the circuit of Figure 1, Figure 3 is a schematic circuit diagram of a typical fixed band-pass filter network forming one of the elements of the circuit of Figure 1 and Figure 4 is a graph illustrative of the frequency band-pass characteristics of filter networks of the type described in Figure 3. Similar reference characters are applied to similar elements throughout the drawing.

Referring to Figure l of the drawing, a source of signals occupying a frequency band from zero to a frequency f1 is applied to the input circuit of a first thermionic tube modulator 3. A source of carrier frequency currents such as, for example, a thermionic tube oscillator 5 also is connected to the input circuit of the first modulator 3 to provide modulated carrier currents in the output circuit of the modulator 3. if the frequency ,fcl of the first carrier frequency oscillator 5 is appreciably higher than the highest signal frequency f1, the currents derived from the first moducarrier and sidebands covering a frequency spectrum from (fcl-fD to (fcl-i-fl).

This frequency spectrum is applied to the input of a fixed band-pass filter network having a pass band (fc1-,1-A) to (icl-H2). It will be seen that the lower sideband (fel-f1) will not be attenuated by the band-pass filter l while the upper sideband (fel-H1) will be attenuated to a value (icl-H2) The currents derived from the first band-pass filter 'l are applied to the input circuit of a second thermionic tube modulator 9. The output of a second carrier frequency source such as, for example, a thermionic tube oscillator ll having a carrier frequency fc2, is also applied to the input of the second modulator Si. The modulated carrier derived from the second modulator 9 will include carrier and sidebands covering the spectra (fcZ-fcl) f2 to (fc2-fc1) +f1 and (fc2+fc1) -fl to (fc2-{-fc1)f-f2. These two sidebands and the second carrier frequency fc2 are applied to the input of a second bandpass lterl network having a pass band covering the spec; trum fc2+fc41-f2 to f2+f1+f2+nf It will be seen that the second band-pass filter will at` tenuate the lower portion of the upper sideband to a band width equivalent to f2, and will not affect the transmission of the upper portion of the upper sideband which already has a band width of f2. Therefore, the output of the second bandpass filter I3 will comprise'ff'requencies covering4 the spectrum (fc2-l-fc1) -f2 to (fc2-l-fc1) -l-f2 or, in other words, a carrier (jez-Hol) having equal upper and lower sidebands f2;

The output of the second band-pass filter I3. is applied to a demodulator I5 such as, for example, a diode thermionic. tubi-' ,eto,derive` currents covering; thefrequencygspectrum from zero to f2, which isthe, desired'lo'w frequency spectrum4 from z'er'o'to f2, which'is the diesiredlow frequency pass baud yIf`it isA desired to lc lerivea`v` pass band from zero to a.frequencyf3.;fwh'ee f3 f2: f1, it merely is necessary"to'increase'the frequency of the rst Crlier frquencv'fci to ,ayalue (fc1-l-f2*f3) and s1' ,n1'i`J.lta Iitliya5indifaledbyV the dash line 33 of Fig; 1, tofdecfraserthesecondcarrier frequency f'c2 toA`[fc2-'-2f(f2'-f3 l. Similarly, if it is desired toincrease` thepass band, the .rst carrier fcl `will lie/decreased in'frequencyand the second carrier f`c 2`,`w il1flbe increasedgin 'frequency in the same manner 'asdescribed heretofore.

Inrtigurez. eraphaindieates the. Original, Signal frequency,,bandy '0tol `)"land the desired low-pass bandlj to f2. The rstcarrierfrequency isindicatdb'y, thedasljifline fol andthe output currents derivedlfrom therst modulator are indicated by thefrequeney spptrunr (fai-fai) to fc1+f1 Graph'bindicates' the parie-pass characteristics of the Afirst and second 'band-pass lters.- Graph c'indicat'es'th'e output-currents derived from the rst lter networkfshowing theattenuation of the upper 4sideband v(fcl-l-Jl) 5to a value f2.

Graph d'illustrates thesecond carrier frequency, indicatedfby thedash line fc2, and the upper and lower sidebands provided-byA the modulation of `the second carrier bywthe modulated. rst carrier..V Graph fe .illustratestheattenuation: of `the lower portion .offthe `upper..sideband and t -e..lack. of attenuation; olii-the .upper -portionmof the upper sidebandwhereby two equall sidebands having a band widthfZ and-acarried (fc2-l-fcl) are .obtained .frnmmhesecondflten network.L As; explained heretofore., the `currents illustrated, by the graph. e are applied :to ,the .demodulatorl5 to, derive the desired low frequencypass band.

The fixed band-pass lter networks I,- I3 -may beof any conventionaligtype known `inf the art which. Willygprevide ftheLdeSirei-.fliequeeey bendf, passrspectra and permissible phase. distortion. A4 typical bandeplass filter Vneetvvork Iis illustrated schematically. inFigure andv includes a first resonant. `circuit I 1 -Y comprising a .parallel-con,- nected .inductor.,`V I 9,.,an1l cai'oacitor 2L. coupled throughcou'pling .capacitors 4v23, -25 to a second resonant .circitfll comprising a `parallel-con,-v nected in'ductor 29and ,capacitor 3|., Theparallel. resonant circuits 4| 1, .Z'Lmay bevtuned to the same orislighltly diierentrespnant frequencies, and, if desired, the.,inclluctorsl ,I9, 29, may be inductively aswell Aas icapacitively coupled. Likewise, the

coupling between'th'e resonant circuits I'I, 21 may" 75 be entirelyy inductive and the coupling capacitors 23, 25 omitted.

Figure 4 illustrates a typical response curve for a band-pass filter of the type described in Figure 3 wherein substantially uniform lattenuation is provided at all frequencies except those within a predetermined frequency band wherein extremely low attenuation; i. e., good-transmission is provided for the desired 'applied signal currents.

It should be understood that any other known types of band-pass lte'r networks may be substituted for the type described in Figure 3J and that phase distortion of the signal may be minimized to. any desired extent by applying Bodes theory tothe design of linear phase shift filters in each of the band-pass filter networks. The advantages ofthe low-pass network thus described areV particularly outstanding if an adjustable network providing low phase distortion of the signal is desired. Adjustable low-pass filters, having a variable cut=oit frequency, designed according tojBodes theory; would require'the gauging of numerous variable capacitorsand inductors;

Thus the invention described'compris'es van im# proved means for and method of securing low band-pass -1 transmission of* signal" frequency' cur'i rentsby' conversions of* low frequencies l to higher frequencies-and-byemployingrelativelyhigh"fre= quencyvband-'pass filters infcombination' withV conventionalL th'ermionicf tubemodulators and adjustable'fthermionic tube oscillatorsl After the required frequency-conversions andattenuations,v the original signal frequencies; lessfthe'undesired frequencies, are obtainedly by' demodl'lltion.` In the; described vsystem `relatively simple frequency ChangeSbring; about @thea desired tb'and-'pass' lcharacteristics instead'4 of :changing Ythe freactive' char'- acteristic of band-pass filters; which reactive changes yarezusually accompaniedK withuundesired 40 phase/shifts.

I `claim ,as-my: invention:

1'.4 Apparatuszfor providinglombandpass transmission` vofgfsgnal, `frequency fcurrents z including means,... forpderiving; from'` said;A signal .1 currents second-' currents having aa;v carrier andstwol side bands; one` Ofatsaidfsidebands. having .the desired. frequency band width, means for derivingifrom; said-j secondi currents g thirdncurrents.V having a, second,-gcarrier -andfzztwo equals-second 'sidebands each having the zdesiredifrequencyzband:.widthi and detectionrand tilterrmeans forlde'modulating; said third currentsz'to denve-Afourtl'ilcurrents hav#- irigsubstantiallyonlyrfrequencieszfwithimsaid 'dei sired lowpassbandn.

2:, Apparatusonprovidingfadi ustableiow band pass transmissionnoffsignalj.frequency? currents including .fmeans .Ii-fori.'- derivingqfrom i: said 1 signal currents-second .currents having ,a'fcarrier l and two lsidebandS.-.-,onepf saidsidebands havingthe desired f ,frequency band width; .means for deriv.- ingfr.omfsaid secondcurrentsthird currents hav-1 ingya ,second carrierand two=equali second-.sida bandseach -hayingathe desiredafrequency :bandwidth,fme'ans for,.adj ustinglfthe- .carriei` frequency upon A which each of -said:sidebandsdepend, and

detection and -Ilterz-,means fondemodulating sa-id' third currents... td derive fourth.. currentsehaving. substantially only frequencies Withinfsaiddesired 1ow.pass,.band.

3..,A low..ban d ;pass,.network forma .source fof. signal .l frequency. I currents.. including. ..a pair-.0L modulators, a pairofcarrier current sources hav ingidierent carrienfrequencies, .a pair. of. filter.` networkseach capable.of,..transmitting.,a Iband` of frequencies including a different one of said'M having substantially only e carrier frequencies-means including `one of said modulators responsive to said signal source and to one of said carrier current sources for deriving from one of said filter networks said one carrier and two sidebands, one of said sidebands having the desired ylow pass band width, means including said other modulator and said other filter network responsive to said frequencies derived from said one lter and said other carrier sourcefor yderiving currents of said other carrier and two equal second sidebands each having said desired low pass band width, and means for detectingsaid last mentioned equal sidebands to derive currents frequencies within said desired low pass band. f

4. An adjustable low band pass network for a source of signal frequency currents including a pair of modulators, a pair of carrier current sources having adjustabie different carrier frequencies, a pair of filter networks each capable of transmitting a band of frequencies including a different one of said carrier frequencies, means including one of said modulators responsive to said signal source and to one of said carrier current sources for deriving from one of said filter networks said one carrier and two sidebands, one of said sidebands having the desired low pass band width, means including said other modulator and said other filter network responsive to said frequencies derived from said one filter and said other carrier source for deriving currents of said other carrier and two equal second sidebands each having said desired low pass band width, means for adjusting the frequencies of said carrier current sources, and means for detecting said last mentioned equal sidebands to derive currents having. substantially only Afrefquencies within said desired low pass band.

5. An adjustable. low band pass network for a source of signal frequency currents including a pair of modulators, a pair of carrier current sources having adjustable ldifferent carrier frequencies, a pair of filter networks each capable of transmitting a band of frequencies including a different one of said carrier frequencies, means including one of said modulators responsive to said signal source and to one of said carriercurrent sources for deriving from one of said filter networks said one carrier and twor sidebands,

one of said sidebands having the desired low pass'v band width, means including said other modulator and said other filter network responsive to said frequencies derived from said one filter and said other` carrier source for deriving currents of said other carrier and two equal second sidebands each having said desired low pass band width, means for adjusting simultaneously the frequencies of said carrier current sources, and means for detecting said last mentioned equal sidebands to derive currents having substantially only frequencies within said desired low pass band.

6. A low band pass network for a source of signal frequency currents including a first modulator, a first carrier frequency current source, a

-`first band pass filter network, means for applying rcurrents including currents of frequencies to be transmitted and said first carrier currents to said first modulator to derive said first carrier and equal sideband currents, means for applying said equal sideband currents to said first filter to pass said first carrier, a complete one of said sidebands and only the desired low frequency portion of the other of said sidebands, a second carrier frequency current source, a second modulator,

having Asubstantially only lator to derive said second carrier :means for applying said second carrier currents and said first carrier and sideband currents derived from said first filter to said second modulator to derive said second carrier and second equal second sideband currents, a second band pass filter network, means for applying said second carrier and said second equal sideband currents to said second filter to derive two equal sidebands each having widths corresponding to said desired low frequency portion of said other of said first sidebands, and means for detecting said last mentioned equal sidebands to derive currents frequencies within the desired low pass band.

'7. An adjustable low band pass network for a, source of signal frequency currents including a .nrst modulator, a first adjustable carrier frequency current source, a first band pass filter network, means for applying currents including currents of frequencies to be transmitted and said first carrier ,currents to said first modulator to derive said first carrier and equal sideband currents, means for'applying said equal sideband currents to said first filter to pass said first carrier, a complete one of said sidebands and only the desired low frequency portion of the other of said sidebands, a second adjustable carrier frequency current source, a second modulator, means for applying said second carrier currents and said first carrier and sideband currents derived from said first filter to said second moduand second equal sideband currents, a secondhand pass filter network, means for applying said second carrier and second equal sideband currents to said second filter to derive two equal sidebands each having widths corresponding to said desired low frequency portion of said other of said first sidebands, means for adjusting the frequencies of said'carrier current sources, and means for detecting said last mentioned equal sidebands to derive currents having substantially only frequencies within the desired low pass band.

8. An adjustablelow band pass network for a source'of signal frequency currents including a first modulator, a first adjustable' carrier frev quency current source, a first band pass filter network, means for applying currents including currents of frequencies to be transmitted and 'said first carrier currents to said first modulator to derive said first carrier and equal sideband currents, means for applying said equal sideband currents to said first filter to pass said first carrier, a complete one of said sidebands and only the desired low frequency portion of the other of said sidebands, a second adjustable carrier frequency current source, a vsecond modulator. means for applying said second carrier currents and said first carrier and sideband currents derived from sald rst filter to said second modulator to derive said second carrier and second equal sideband currents, a second band pass filter network, means for applying said second carrier and second equal sideband currents to said second filter to derive two equal sidebands each having widths corresponding to said desired low frequency portion of said other of said first sidebands, means for adjusting simultaneously the frequencies of said carrier current sources, and means for detecting said last mentioned equal sidebands to derive currents having substantially only frequencies within the desired low pass band.

9. The method of providing low band pass transmission of signal frequency currents comprising generating first carrier currents, moda-e '.-t-lating said 'mrst carrier .currents by. applying artheretoisaidfsignal. currents, selecting apredetervi'.rn'iinedsirequency. portiomincludingfthe'carrier and eatrleastportions*ofsbothzsidebandsrof saidzmodu- `dated-carrier currents; generatngseconmcarrier `currents. of.a lfrequency.-liiflerent fthamsaid .':rst .carrier4 currents; emodulating `saidsecond carrier .gcurrents =byfapp1ying theretosaidlselectedimodu- 1 lated .nari-ier currents, .selecting fa a predetermined portion of said last mentionewmodulated carrier f @currents .and 4'detecting.zsaidfselected :portioni of fthe:last-mentioned. carrier. currents fto. derive :'Sg-

1f nal vcurrents zhaving substantially .only frequencies Within said desiredlow.passfband filmt-The method .-of. providing .adjustable lowt band .pass .transmissionvof::signal zfrequencynurl,rents comprising generatingfiirstfcarriencurrents, :emodulating asaid Afirst carrier. currents byfpply- AfingJtheretosaid signal fcurrents; selecting@ epredetermined-:frequency .portion including `rt-heicar- .4

:v1-ier and fatleast portions t of .both :sidebands of Vsaid .modulatec-fcarrier currents, generating esec- .ondscarrier currents oitaifrequency` diierent'than usaid riirstcarrier; currents, modulating said. second carrier currents byapplying .thereto saidiselected,v

modulated carrier. currents,.selecting a.predeter 'mined portion ofsaid-.lastwmentioned .carrier cur- .'rents, adjusting 'the frequencies of .said :,rst and pfaid `second carrier currents, and :detecting-@said fselected portion =of said :last mentioned..` carrier- .:currents' Ato .-derive signal .currents lhaving sub- ..stantially vonly ,frequencies .withinl said desired I dow .passband 111.*51hemethod. .of -providingadjustablezdow `t lband f pass transmissionl of signal'ffrequency .cur-` irentscomprising.generatlngbrst carrierfcurrents, 'f modulating-said :first Acarrier currentsbysaidsig- .nallcurrents, selecting a-predetermined frequency portion including the. carrierand.atrleastvportions rof -both .sidebands .of said modulated vcarrier/currents, generating second-.carrier currentsofadre- `quency different :than said :iirstncarrier currents, modulating. said second 'carrier cum-ents'by said .selected modulated lcarrier .-currentsf selecting a,

. :predetermined portion of :said last'mentioned-.curr

rents, .adjusting simultaneously the"=frequencies ofssaid rst and said secondcarrier currentseand detecting said selected :portion offsaid-ilast-amenl:tioned ycarrier currents .to .derivelsignal currents having substantially only :frequencies withingsaid-'f :desired V:low pass band.

L2. mheiimethodl offnproviding:adjustable low gmnd-I pass Li-,ransmissien ofisignal {frequency-.eur- ,z-rentszcomprisinafgeneratinglirst carrier, currents. f-.,modu1atingadrst fcarriemcurxents bassa-insig- 5 mal.:currents;selecting@predetermined:frequency mortionincluding fthe carrierlandiat leastmortions .cffbotnsidebands nffsaidmcdulated eurxentsfsen- L-.ferating secondV carrierncurrents of a :htenuency sminerent ithan-gsaid lrstvcarrier currents, modulozzlatinerfsaid l:secondmarriemcurrents :by saidfsa- .lectedmodulatedzcarrierlcurrents, rselesting;affpre :'detenninedn pontionzof said. last .mentoned..m1rfgrents, adjusting4 the -:frequency` j f `said {n1- st @earfrier; currents andfsaidxsecond 4carrier. currents. in 15 opposite senses, and detectingvsaid selected @por- :tion 1,oszaiidilast inelritionecarrier: currents .to de- Lrire-signalcurrents havingsubstantially only:;fre '-,;-quencies mithin :.said desired :low mass band.

13; The-method of :providing vadjustable:new .-ph .nd pass transmissionmf signal -frequencmcurfrrents comprising4 generating rstlcarrier currents, `.:siriodulatine:.said rstcarrier. currents by-said sig- 1 nal-,currentsfselecting-a predetennnedirequency fzportonfincluding :the carrier and. at least'ponticns 1 f Jof: bothsidebands of said'modulatedv currentsleneerating: Asecond f carrier currents :nf a Y .frequency :.different :than said rst zcarrier fcurrents, fmodulating'said second 'carriencurrents byfsaid selected modulated carriercurrents,` :selecting a predetermined portion of said .lastcmeritioned currents, -'.-adll1ting the frequency! .0f saidxfrst Icarrier. currents and said second carrierfcurrentsginf opposite :'senses andain different-:proportionateamounts.and detecting-.,.-saidselected:portion ofrsaid last-men- .,xtionedfcarrier; .currents to s derive. signal currents r havingsubstantially'lonlyfrequencies -within vsaid fidesired low rpassaband.

1 GQRDQN IL. 'FREDENDALL.

:BEEERENCES :CITfED UNITED, :STATES .PATENTS 4are of -record in the 45, iNumber Nam-e Date :1,861,488 Osborne Dec. 7, A19120 11;830j896 Wintringham gNov.` 10; i931 Lf1,905;714 Horton ;.Aprli25g r1933 w .'l-=;2;339,'633 Gilman .Ian2'18,*1944

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1361488 *31 Mar 19207 Dec 1920American Telephone & TelegraphPlural modulation system
US1830896 *19 Jan 192810 Nov 1931American Telephone & TelegraphAdjustable electric filter system
US1905714 *10 Apr 193125 Apr 1933Bell Telephone Labor IncSignaling system
US2339633 *23 Mar 194218 Jan 1944Bell Telephone Labor IncVariable selective system
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2635143 *4 Jan 194914 Apr 1953Marconi S Wireless Telegrpah CVariable electrical filter
US2923887 *29 Nov 19552 Feb 1960Ross Radio CorpElectronic circuit arrangement for the controlled amplification of a desired signal
US2951206 *15 Nov 195730 Aug 1960Rca CorpVariable delay line
US3505607 *14 Nov 19677 Apr 1970Philips CorpArrangement for selecting in a correct phase relationship a characteristic component from a frequency spectrum
US6049706 *21 Oct 199811 Apr 2000Parkervision, Inc.Integrated frequency translation and selectivity
US6061551 *21 Oct 19989 May 2000Parkervision, Inc.Method and system for down-converting electromagnetic signals
US6061555 *21 Oct 19989 May 2000Parkervision, Inc.Method and system for ensuring reception of a communications signal
US6091940 *21 Oct 199818 Jul 2000Parkervision, Inc.Method and system for frequency up-conversion
US626651818 Aug 199924 Jul 2001Parkervision, Inc.Method and system for down-converting electromagnetic signals by sampling and integrating over apertures
US635373523 Aug 19995 Mar 2002Parkervision, Inc.MDG method for output signal generation
US63703713 Mar 19999 Apr 2002Parkervision, Inc.Applications of universal frequency translation
US642153418 Aug 199916 Jul 2002Parkervision, Inc.Integrated frequency translation and selectivity
US654272216 Apr 19991 Apr 2003Parkervision, Inc.Method and system for frequency up-conversion with variety of transmitter configurations
US656030116 Apr 19996 May 2003Parkervision, Inc.Integrated frequency translation and selectivity with a variety of filter embodiments
US658090216 Apr 199917 Jun 2003Parkervision, Inc.Frequency translation using optimized switch structures
US664725018 Aug 199911 Nov 2003Parkervision, Inc.Method and system for ensuring reception of a communications signal
US668749316 Apr 19993 Feb 2004Parkervision, Inc.Method and circuit for down-converting a signal using a complementary FET structure for improved dynamic range
US669412810 May 200017 Feb 2004Parkervision, Inc.Frequency synthesizer using universal frequency translation technology
US67045493 Jan 20009 Mar 2004Parkvision, Inc.Multi-mode, multi-band communication system
US67045583 Jan 20009 Mar 2004Parkervision, Inc.Image-reject down-converter and embodiments thereof, such as the family radio service
US67983515 Apr 200028 Sep 2004Parkervision, Inc.Automated meter reader applications of universal frequency translation
US681348520 Apr 20012 Nov 2004Parkervision, Inc.Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same
US683665030 Dec 200228 Dec 2004Parkervision, Inc.Methods and systems for down-converting electromagnetic signals, and applications thereof
US687383610 May 200029 Mar 2005Parkervision, Inc.Universal platform module and methods and apparatuses relating thereto enabled by universal frequency translation technology
US687981714 Mar 200012 Apr 2005Parkervision, Inc.DC offset, re-radiation, and I/Q solutions using universal frequency translation technology
US696373412 Dec 20028 Nov 2005Parkervision, Inc.Differential frequency down-conversion using techniques of universal frequency translation technology
US69758488 Nov 200213 Dec 2005Parkervision, Inc.Method and apparatus for DC offset removal in a radio frequency communication channel
US70068053 Jan 200028 Feb 2006Parker Vision, Inc.Aliasing communication system with multi-mode and multi-band functionality and embodiments thereof, such as the family radio service
US701028616 May 20017 Mar 2006Parkervision, Inc.Apparatus, system, and method for down-converting and up-converting electromagnetic signals
US701055913 Nov 20017 Mar 2006Parkervision, Inc.Method and apparatus for a parallel correlator and applications thereof
US70166634 Mar 200221 Mar 2006Parkervision, Inc.Applications of universal frequency translation
US702778610 May 200011 Apr 2006Parkervision, Inc.Carrier and clock recovery using universal frequency translation
US703937213 Apr 20002 May 2006Parkervision, Inc.Method and system for frequency up-conversion with modulation embodiments
US705050818 Jul 200223 May 2006Parkervision, Inc.Method and system for frequency up-conversion with a variety of transmitter configurations
US70542964 Aug 200030 May 2006Parkervision, Inc.Wireless local area network (WLAN) technology and applications including techniques of universal frequency translation
US70723904 Aug 20004 Jul 2006Parkervision, Inc.Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US70724277 Nov 20024 Jul 2006Parkervision, Inc.Method and apparatus for reducing DC offsets in a communication system
US70760117 Feb 200311 Jul 2006Parkervision, Inc.Integrated frequency translation and selectivity
US70821719 Jun 200025 Jul 2006Parkervision, Inc.Phase shifting applications of universal frequency translation
US70853359 Nov 20011 Aug 2006Parkervision, Inc.Method and apparatus for reducing DC offsets in a communication system
US710702812 Oct 200412 Sep 2006Parkervision, Inc.Apparatus, system, and method for up converting electromagnetic signals
US71104444 Aug 200019 Sep 2006Parkervision, Inc.Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments and circuit implementations
US719094112 Dec 200213 Mar 2007Parkervision, Inc.Method and apparatus for reducing DC offsets in communication systems using universal frequency translation technology
US721889912 Oct 200415 May 2007Parkervision, Inc.Apparatus, system, and method for up-converting electromagnetic signals
US72189075 Jul 200515 May 2007Parkervision, Inc.Method and circuit for down-converting a signal
US722474913 Dec 200229 May 2007Parkervision, Inc.Method and apparatus for reducing re-radiation using techniques of universal frequency translation technology
US723396918 Apr 200519 Jun 2007Parkervision, Inc.Method and apparatus for a parallel correlator and applications thereof
US72367544 Mar 200226 Jun 2007Parkervision, Inc.Method and system for frequency up-conversion
US72458863 Feb 200517 Jul 2007Parkervision, Inc.Method and system for frequency up-conversion with modulation embodiments
US727216410 Dec 200218 Sep 2007Parkervision, Inc.Reducing DC offsets using spectral spreading
US729283529 Jan 20016 Nov 2007Parkervision, Inc.Wireless and wired cable modem applications of universal frequency translation technology
US72958265 May 200013 Nov 2007Parkervision, Inc.Integrated frequency translation and selectivity with gain control functionality, and applications thereof
US730824210 Aug 200411 Dec 2007Parkervision, Inc.Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same
US73216404 Jun 200322 Jan 2008Parkervision, Inc.Active polyphase inverter filter for quadrature signal generation
US732173510 May 200022 Jan 2008Parkervision, Inc.Optical down-converter using universal frequency translation technology
US737641016 Feb 200620 May 2008Parkervision, Inc.Methods and systems for down-converting a signal using a complementary transistor structure
US73795152 Mar 200127 May 2008Parkervision, Inc.Phased array antenna applications of universal frequency translation
US737988318 Jul 200227 May 2008Parkervision, Inc.Networking methods and systems
US738629225 Oct 200410 Jun 2008Parkervision, Inc.Apparatus, system, and method for down-converting and up-converting electromagnetic signals
US738910024 Mar 200317 Jun 2008Parkervision, Inc.Method and circuit for down-converting a signal
US743391018 Apr 20057 Oct 2008Parkervision, Inc.Method and apparatus for the parallel correlator and applications thereof
US745445324 Nov 200318 Nov 2008Parkervision, Inc.Methods, systems, and computer program products for parallel correlation and applications thereof
US746058418 Jul 20022 Dec 2008Parkervision, Inc.Networking methods and systems
US748368627 Oct 200427 Jan 2009Parkervision, Inc.Universal platform module and methods and apparatuses relating thereto enabled by universal frequency translation technology
US749634225 Oct 200424 Feb 2009Parkervision, Inc.Down-converting electromagnetic signals, including controlled discharge of capacitors
US751589614 Apr 20007 Apr 2009Parkervision, Inc.Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US752952218 Oct 20065 May 2009Parkervision, Inc.Apparatus and method for communicating an input signal in polar representation
US753947417 Feb 200526 May 2009Parkervision, Inc.DC offset, re-radiation, and I/Q solutions using universal frequency translation technology
US754609622 May 20079 Jun 2009Parkervision, Inc.Frequency up-conversion using a harmonic generation and extraction module
US755450815 Jan 200830 Jun 2009Parker Vision, Inc.Phased array antenna applications on universal frequency translation
US759942117 Apr 20066 Oct 2009Parkervision, Inc.Spread spectrum applications of universal frequency translation
US762037816 Jul 200717 Nov 2009Parkervision, Inc.Method and system for frequency up-conversion with modulation embodiments
US765314525 Jan 200526 Jan 2010Parkervision, Inc.Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments and circuit implementations
US765315817 Feb 200626 Jan 2010Parkervision, Inc.Gain control in a communication channel
US769323022 Feb 20066 Apr 2010Parkervision, Inc.Apparatus and method of differential IQ frequency up-conversion
US76935022 May 20086 Apr 2010Parkervision, Inc.Method and system for down-converting an electromagnetic signal, transforms for same, and aperture relationships
US769791621 Sep 200513 Apr 2010Parkervision, Inc.Applications of universal frequency translation
US772484528 Mar 200625 May 2010Parkervision, Inc.Method and system for down-converting and electromagnetic signal, and transforms for same
US777368820 Dec 200410 Aug 2010Parkervision, Inc.Method, system, and apparatus for balanced frequency up-conversion, including circuitry to directly couple the outputs of multiple transistors
US782240112 Oct 200426 Oct 2010Parkervision, Inc.Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US782681720 Mar 20092 Nov 2010Parker Vision, Inc.Applications of universal frequency translation
US78651777 Jan 20094 Jan 2011Parkervision, Inc.Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US78947897 Apr 200922 Feb 2011Parkervision, Inc.Down-conversion of an electromagnetic signal with feedback control
US792963814 Jan 201019 Apr 2011Parkervision, Inc.Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US79360229 Jan 20083 May 2011Parkervision, Inc.Method and circuit for down-converting a signal
US793705931 Mar 20083 May 2011Parkervision, Inc.Converting an electromagnetic signal via sub-sampling
US799181524 Jan 20082 Aug 2011Parkervision, Inc.Methods, systems, and computer program products for parallel correlation and applications thereof
US80192915 May 200913 Sep 2011Parkervision, Inc.Method and system for frequency down-conversion and frequency up-conversion
US80363045 Apr 201011 Oct 2011Parkervision, Inc.Apparatus and method of differential IQ frequency up-conversion
US807779724 Jun 201013 Dec 2011Parkervision, Inc.Method, system, and apparatus for balanced frequency up-conversion of a baseband signal
US816019631 Oct 200617 Apr 2012Parkervision, Inc.Networking methods and systems
US816053414 Sep 201017 Apr 2012Parkervision, Inc.Applications of universal frequency translation
US819010826 Apr 201129 May 2012Parkervision, Inc.Method and system for frequency up-conversion
US81901164 Mar 201129 May 2012Parker Vision, Inc.Methods and systems for down-converting a signal using a complementary transistor structure
US82238987 May 201017 Jul 2012Parkervision, Inc.Method and system for down-converting an electromagnetic signal, and transforms for same
US822428122 Dec 201017 Jul 2012Parkervision, Inc.Down-conversion of an electromagnetic signal with feedback control
US822902319 Apr 201124 Jul 2012Parkervision, Inc.Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US823385510 Nov 200931 Jul 2012Parkervision, Inc.Up-conversion based on gated information signal
US829540610 May 200023 Oct 2012Parkervision, Inc.Universal platform module for a plurality of communication protocols
US82958007 Sep 201023 Oct 2012Parkervision, Inc.Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US834061822 Dec 201025 Dec 2012Parkervision, Inc.Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US84070619 May 200826 Mar 2013Parkervision, Inc.Networking methods and systems
US84469949 Dec 200921 May 2013Parkervision, Inc.Gain control in a communication channel
US859422813 Sep 201126 Nov 2013Parkervision, Inc.Apparatus and method of differential IQ frequency up-conversion
US20010027561 *29 May 20014 Oct 2001Microsoft CorporationVideo on demand methods and systems
US20030128776 *7 Nov 200210 Jul 2003Parkervision, IncMethod and apparatus for reducing DC off sets in a communication system
US20050009494 *10 Aug 200413 Jan 2005Parkervision, Inc.Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same
US20090221257 *7 Jan 20093 Sep 2009Parkervision, Inc.Method and System For Down-Converting An Electromagnetic Signal, And Transforms For Same, And Aperture Relationships
Classifications
U.S. Classification455/102, 455/108, 332/151
International ClassificationH03H7/01, H04J1/04, H04J1/00
Cooperative ClassificationH04J1/045, H03H7/1775, H03H7/0115
European ClassificationH03H7/17R4, H04J1/04B, H03H7/01B