CA1089028A - Filter and demodulation arrangement - Google Patents
Filter and demodulation arrangementInfo
- Publication number
- CA1089028A CA1089028A CA279,169A CA279169A CA1089028A CA 1089028 A CA1089028 A CA 1089028A CA 279169 A CA279169 A CA 279169A CA 1089028 A CA1089028 A CA 1089028A
- Authority
- CA
- Canada
- Prior art keywords
- digital
- signals
- frequency
- passband
- filter
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
- H04L27/06—Demodulator circuits; Receiver circuits
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
- H03D3/007—Demodulation of angle-, frequency- or phase- modulated oscillations by converting the oscillations into two quadrature related signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D5/00—Circuits for demodulating amplitude-modulated or angle-modulated oscillations at will
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
- H03D2200/0041—Functional aspects of demodulators
- H03D2200/0047—Offset of DC voltage or frequency
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
- H03D2200/0041—Functional aspects of demodulators
- H03D2200/0054—Digital filters
- H03D2200/0056—Digital filters including a digital decimation filter
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
- H03D2200/0041—Functional aspects of demodulators
- H03D2200/006—Signal sampling
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
- H03D2200/0041—Functional aspects of demodulators
- H03D2200/0082—Quadrature arrangements
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
- H03D7/16—Multiple-frequency-changing
- H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
Abstract
ABSTRACT:
A digital filter and demodulation arrange-ment for passband signals, whose corresponding baseband signal has a bandwidth limited to a given maximum fre-quency. The passband signals are filtered according to two bandpass characteristics which, apart from their asymmetrical distortion relative to their central fre-quency, are versions from one another shifted 90° in phase. The filtered passband signals are demodulated with an in-phase carrier and a quadrature carrier and the demodulated signals are combined to a baseband signal. In the digital filtering process the sampling frequency is reduced from a value higher than twice the highest frequency in the passband signals to a value which is not higher than twice said maximum frequency in the baseband signal and in the digital demodulation and combination processes the reduced sampling frequency is also used so that a considerable reduction in the inter-nal processing speed is obtained.
A digital filter and demodulation arrange-ment for passband signals, whose corresponding baseband signal has a bandwidth limited to a given maximum fre-quency. The passband signals are filtered according to two bandpass characteristics which, apart from their asymmetrical distortion relative to their central fre-quency, are versions from one another shifted 90° in phase. The filtered passband signals are demodulated with an in-phase carrier and a quadrature carrier and the demodulated signals are combined to a baseband signal. In the digital filtering process the sampling frequency is reduced from a value higher than twice the highest frequency in the passband signals to a value which is not higher than twice said maximum frequency in the baseband signal and in the digital demodulation and combination processes the reduced sampling frequency is also used so that a considerable reduction in the inter-nal processing speed is obtained.
Description
`~
/
PHN. 8411~.
LSTR/WJM.
25-3-1977.
:.
~'~ilter and demodulation arrangemen-t".
; (A~ Back~round of the invention.
` (1) Fleld of the invention.
The invention relates to filtering and de-modulating passband signals~obtained by modulating a carrier in accordance wlth an information-carrying base-band signal whose band-width is limited to a given maxi-mum frequency.
` ~:` : ~
In the transmission of information by electromagnetic means modulation of a carrier is often used at the transmitter end for obtaining a passband sig-nal which is properly adapted to the properties of the 10~ transmis~slon path. At~the reoeivlng end the signal de-rived from the transmission path is demodulated after ,, ~
unwanted signal components originating from the trans-mission path have been suppressed by means o~ a bandpass filter (the so-called premodulation filter). Unwanted ~ ;slgnal~components whloh;~are produced in the demodulation process are often suppressed by means of a low-pass filter (th~e so-called post modulation filter).
The invention results from lnvestigations in~thè~;fleld~of s;2400~Band AM-modeni for data slgnal 20~ transmission;~but~ls~not~limit2d thereto as the same princlples~can~be~used~for other~data rates, for ln-formation-~carrying~signals of ano-ther kind and for other Z~
PHN. 8414. ' "
modulation methods such as VSB, PSK and Q~M. Although this 2400 Baud AM~modem will be discussed hereinaftRr this should not be interpreted as a limi ation of the ~
range of application of the principles acoording to ' the i~vention.
~2) Description'of'the prior art.
.
United States Patent Specification 3,753,115 P.J. vo Gbrwen et al - August 14, 1973 discloses an arrangement for filtering and demodulating passband sig-nals obtained by mDdulating a carrier in accordance with a baseband signal whose ban~width is limited to a given '~
m~xim~m frequency, which arrangement is provided with means for filtering the passband signals according to a first and a second passband characteristic for generating first and second filtered passband signals, which passband characteristics, apart from their asymmetrical distortion '~
relative to their central ~re3ulnoy, are versions from one another, shifted 90 in phase, means for demodulating the first and second filtered passband signals with an in-phase -carrier and a quadrature carrier respectively for generat- ' ' ing first and second demodulated'signals, and means for oombining the first and th~'second demodulated signals.
In particular, the use of two-transversal premodulation filters and t~o analog mDdulators eliminates the influence of that dist~rtion in the'transfer characteristic of this premodulation filters which is caused by a ' :.
. -,:
' ':::
~ 3 ~
:
PHN. 8414.
':
llmitation of the duration of the impulse response of these filters and which is asymmetrical relative to the central frequency of these filters; in addition it ac-; complishes that no post-modulatlon filter is required.
5 -- ` The structure of this prior art arrange- ;
ment is of a hybid nature, that is to say that in the transversal filters use is indeed made of digital delay elements but that otherwise analog circuit components `; are used, such as resistors, for the weighting networks wherein the filter coefficients are fixed, and analog modulators. A dxawback of this hybrid structure is the ; fact that once such an arrangement is fully integrated in one semiconductor body it is difficult to modify .
given paramete~s, such as filter characterlstics, so that S ~ the~arrangement i~s;~not programmable. Another drawback Or~ this hybrld structur0 is the fact that for a proper correotion of the influence of the asymmetrical distor-tion in the transfer characteristic of the premodulation filter high requirements are imposed on the modulators as regards d.c.- oEEset and other imperfections which : , ~ : : : . -are difficult to~ avoid in analog circuits whereas it i8 not possible to U9e digital modulators behind the filters without additional ADC circuits. ~ -B)_Summarv of the lnvention.
25~ It~is an object of the in~entîon to pro~ide a fully digital~implementation of a ~ilter and demodulat- -:, , : ~ . .. .. . .. , - . . - . . ..
~39~2~
.
PHN. 8414.
25-3-1977.
' : ion arrangemerlt of the type mentioned, ~herein the influence of asymmetrical distortion in the transfer characteristic of the premodulation filter owing to limitation of the duration of its impulse response is .-- eliminated and no post-modulation filter is required and wherein, furthermore, a lowest possible internal processing speed is realized.
: The filter and demodulation arrangement according to the invention is characterized in that . ~ 10 ~ all means for filtering, demodulating and combining are ~:
digital means, the digital filter means are, further-., . :
more, provided with means for sampling frequency reduct-ion for converting signal samples of the passband sig-nals oocurring;with a firs-t sampling frequency which is : higher than twice the highest ~requency in the passband ~: , : signals~ into signal~samples of the first and second : . filtered passband signals occurring with a second sampl-:~ : ing frequency which is not higher than twice said maximum frequency of the baseband signal, and the digital means 20~ ~ for demodulating and combining are arranged for pro-~ cessing signal samples occurring with the same second ;~ : . sampling frequency.
..
:In this manner a digital filter and demodu-lati.on arrangement:ls obtained~which~is very sultable :25:~ or ~ull int:egration in~one semiconductor body. On the :.:
other hand, by performing the storage of the filter z~3 .
PHN. 8414.
coefficients separately an arrangement can be easily obtained which is programmable, that is to say that after integration given parameters can be modified in a manner which is known ~ se. Furthermore, the draw-backs which are associated with analog demodulators are obviated by the digital implementation of the de-modulation mèans.
(C) Short descri~tion of the drawing.
The invention and its advantages will be `
further explained with reference to the drawlng, in which:
~ig. 1 is a block diagram of a filter and demodulation arrangement accordlng to the above-mentioned prior art;
, 15 ~ ; ~ Fig. 2 is a block diagram of a digital fil-ter and demodulation arrangement according to the in-vention.
.
(D ~References.
~,Bellanger et aI.~ "Digital filtering of ; ~ 20~ ~ bandlimited~ signals: Interpolation, extrapolation and distortions~due: to;varlous truncations. Reduction of compUtation speed in digital filters". IEEE - ICC June :
13, 1973, pages 32-11 to 23-15.
L.~R. Rablner~st al.,~ "Terminology in dlgital
/
PHN. 8411~.
LSTR/WJM.
25-3-1977.
:.
~'~ilter and demodulation arrangemen-t".
; (A~ Back~round of the invention.
` (1) Fleld of the invention.
The invention relates to filtering and de-modulating passband signals~obtained by modulating a carrier in accordance wlth an information-carrying base-band signal whose band-width is limited to a given maxi-mum frequency.
` ~:` : ~
In the transmission of information by electromagnetic means modulation of a carrier is often used at the transmitter end for obtaining a passband sig-nal which is properly adapted to the properties of the 10~ transmis~slon path. At~the reoeivlng end the signal de-rived from the transmission path is demodulated after ,, ~
unwanted signal components originating from the trans-mission path have been suppressed by means o~ a bandpass filter (the so-called premodulation filter). Unwanted ~ ;slgnal~components whloh;~are produced in the demodulation process are often suppressed by means of a low-pass filter (th~e so-called post modulation filter).
The invention results from lnvestigations in~thè~;fleld~of s;2400~Band AM-modeni for data slgnal 20~ transmission;~but~ls~not~limit2d thereto as the same princlples~can~be~used~for other~data rates, for ln-formation-~carrying~signals of ano-ther kind and for other Z~
PHN. 8414. ' "
modulation methods such as VSB, PSK and Q~M. Although this 2400 Baud AM~modem will be discussed hereinaftRr this should not be interpreted as a limi ation of the ~
range of application of the principles acoording to ' the i~vention.
~2) Description'of'the prior art.
.
United States Patent Specification 3,753,115 P.J. vo Gbrwen et al - August 14, 1973 discloses an arrangement for filtering and demodulating passband sig-nals obtained by mDdulating a carrier in accordance with a baseband signal whose ban~width is limited to a given '~
m~xim~m frequency, which arrangement is provided with means for filtering the passband signals according to a first and a second passband characteristic for generating first and second filtered passband signals, which passband characteristics, apart from their asymmetrical distortion '~
relative to their central ~re3ulnoy, are versions from one another, shifted 90 in phase, means for demodulating the first and second filtered passband signals with an in-phase -carrier and a quadrature carrier respectively for generat- ' ' ing first and second demodulated'signals, and means for oombining the first and th~'second demodulated signals.
In particular, the use of two-transversal premodulation filters and t~o analog mDdulators eliminates the influence of that dist~rtion in the'transfer characteristic of this premodulation filters which is caused by a ' :.
. -,:
' ':::
~ 3 ~
:
PHN. 8414.
':
llmitation of the duration of the impulse response of these filters and which is asymmetrical relative to the central frequency of these filters; in addition it ac-; complishes that no post-modulatlon filter is required.
5 -- ` The structure of this prior art arrange- ;
ment is of a hybid nature, that is to say that in the transversal filters use is indeed made of digital delay elements but that otherwise analog circuit components `; are used, such as resistors, for the weighting networks wherein the filter coefficients are fixed, and analog modulators. A dxawback of this hybrid structure is the ; fact that once such an arrangement is fully integrated in one semiconductor body it is difficult to modify .
given paramete~s, such as filter characterlstics, so that S ~ the~arrangement i~s;~not programmable. Another drawback Or~ this hybrld structur0 is the fact that for a proper correotion of the influence of the asymmetrical distor-tion in the transfer characteristic of the premodulation filter high requirements are imposed on the modulators as regards d.c.- oEEset and other imperfections which : , ~ : : : . -are difficult to~ avoid in analog circuits whereas it i8 not possible to U9e digital modulators behind the filters without additional ADC circuits. ~ -B)_Summarv of the lnvention.
25~ It~is an object of the in~entîon to pro~ide a fully digital~implementation of a ~ilter and demodulat- -:, , : ~ . .. .. . .. , - . . - . . ..
~39~2~
.
PHN. 8414.
25-3-1977.
' : ion arrangemerlt of the type mentioned, ~herein the influence of asymmetrical distortion in the transfer characteristic of the premodulation filter owing to limitation of the duration of its impulse response is .-- eliminated and no post-modulation filter is required and wherein, furthermore, a lowest possible internal processing speed is realized.
: The filter and demodulation arrangement according to the invention is characterized in that . ~ 10 ~ all means for filtering, demodulating and combining are ~:
digital means, the digital filter means are, further-., . :
more, provided with means for sampling frequency reduct-ion for converting signal samples of the passband sig-nals oocurring;with a firs-t sampling frequency which is : higher than twice the highest ~requency in the passband ~: , : signals~ into signal~samples of the first and second : . filtered passband signals occurring with a second sampl-:~ : ing frequency which is not higher than twice said maximum frequency of the baseband signal, and the digital means 20~ ~ for demodulating and combining are arranged for pro-~ cessing signal samples occurring with the same second ;~ : . sampling frequency.
..
:In this manner a digital filter and demodu-lati.on arrangement:ls obtained~which~is very sultable :25:~ or ~ull int:egration in~one semiconductor body. On the :.:
other hand, by performing the storage of the filter z~3 .
PHN. 8414.
coefficients separately an arrangement can be easily obtained which is programmable, that is to say that after integration given parameters can be modified in a manner which is known ~ se. Furthermore, the draw-backs which are associated with analog demodulators are obviated by the digital implementation of the de-modulation mèans.
(C) Short descri~tion of the drawing.
The invention and its advantages will be `
further explained with reference to the drawlng, in which:
~ig. 1 is a block diagram of a filter and demodulation arrangement accordlng to the above-mentioned prior art;
, 15 ~ ; ~ Fig. 2 is a block diagram of a digital fil-ter and demodulation arrangement according to the in-vention.
.
(D ~References.
~,Bellanger et aI.~ "Digital filtering of ; ~ 20~ ~ bandlimited~ signals: Interpolation, extrapolation and distortions~due: to;varlous truncations. Reduction of compUtation speed in digital filters". IEEE - ICC June :
13, 1973, pages 32-11 to 23-15.
L.~R. Rablner~st al.,~ "Terminology in dlgital
2~5;~ ~ signal processing," IEEE~Trans. Audio Electroacoust, Yol~ AU-20, No. 5~ December 1972~ pages 322-337.
~ow~z~
PHN. 8414.
25-3-1977~
:
; ' R.W.Schafer et al., "A digital signal pro-cessing approach to interpolation", Proc. IEEE, Vol. 61, No.6, June 1973, pages 692-702.
(EL List of abbreviations.
AM - "amplitude modulation"
' A~C- "analog-to-digital conversion"
~ DAC- ~'digital-to-analog conversion'9 i ~ PSK- ~phase shift keying"
QAM-~"quadrature amplitude modulation~' VSB- ~'vestigial sideband~
(F) Descrlption of the èmbodiments.
(1) General descripti_n.
' ' Fig. 1 shows the block diagram of a prior art arrangement~ for~filtering and coherently demodulat-5~ ing a~passb;and signal whlch i~s transmitted via a~trans-~ mission path.- The ~signal derived from a transmission path m;'~ appears at a~oommon input 1;o~ two bandpass filters 2 and ; 3. The fllt'sred passband signal at the output of filter 2 is demodulated ln modulator 4 by means of an in-phase ,,20, ~ oarrier whioh isavailable at an output 71 of a local ;oarrier~source 7~ Likewise the filt;ersd passband~signal ~ ~, at~the ~output~of~filter; 3 is demodulated in modulat~or~5 by me~ns of;a quadrature~carrier which is available,at `an~,output; 72'o~ carrier source 7. The demodulated~signa~s 25~ at~the~output~o~ modulat~o~rs ~4 and~5 are added ln,a llnesr co ina~tl~on~;ci~rou~i~t~8.~
;
PHN. 8414.
United States Patent Specification 3,753,115 proves that, by means of a special relation between the transfer characteristics of filters 2 and 3, at output 9 of combination circuit 8 that filtered information-carrying baseband signal is immediately available that v.
has been used at the transmitter end of the transmission path for modulating an in-phase carrier for obtaining the passband signal. In that case no post modulation filter is required to suppress unwanted frequency com-ponents~and, in addition, the influence of that distort-on in the amplitude characteristi.c AB(W ) of ~ilter 2 is eliminated that is caused by limitation of the dura-., .
; tion of the impuls response of filter 2 and that is asymmetrical relative to the central frequency ~m f ;15 ~ fllter 2, as the amplitude characteristic ~B(~J) of filt~r
~ow~z~
PHN. 8414.
25-3-1977~
:
; ' R.W.Schafer et al., "A digital signal pro-cessing approach to interpolation", Proc. IEEE, Vol. 61, No.6, June 1973, pages 692-702.
(EL List of abbreviations.
AM - "amplitude modulation"
' A~C- "analog-to-digital conversion"
~ DAC- ~'digital-to-analog conversion'9 i ~ PSK- ~phase shift keying"
QAM-~"quadrature amplitude modulation~' VSB- ~'vestigial sideband~
(F) Descrlption of the èmbodiments.
(1) General descripti_n.
' ' Fig. 1 shows the block diagram of a prior art arrangement~ for~filtering and coherently demodulat-5~ ing a~passb;and signal whlch i~s transmitted via a~trans-~ mission path.- The ~signal derived from a transmission path m;'~ appears at a~oommon input 1;o~ two bandpass filters 2 and ; 3. The fllt'sred passband signal at the output of filter 2 is demodulated ln modulator 4 by means of an in-phase ,,20, ~ oarrier whioh isavailable at an output 71 of a local ;oarrier~source 7~ Likewise the filt;ersd passband~signal ~ ~, at~the ~output~of~filter; 3 is demodulated in modulat~or~5 by me~ns of;a quadrature~carrier which is available,at `an~,output; 72'o~ carrier source 7. The demodulated~signa~s 25~ at~the~output~o~ modulat~o~rs ~4 and~5 are added ln,a llnesr co ina~tl~on~;ci~rou~i~t~8.~
;
PHN. 8414.
United States Patent Specification 3,753,115 proves that, by means of a special relation between the transfer characteristics of filters 2 and 3, at output 9 of combination circuit 8 that filtered information-carrying baseband signal is immediately available that v.
has been used at the transmitter end of the transmission path for modulating an in-phase carrier for obtaining the passband signal. In that case no post modulation filter is required to suppress unwanted frequency com-ponents~and, in addition, the influence of that distort-on in the amplitude characteristi.c AB(W ) of ~ilter 2 is eliminated that is caused by limitation of the dura-., .
; tion of the impuls response of filter 2 and that is asymmetrical relative to the central frequency ~m f ;15 ~ fllter 2, as the amplitude characteristic ~B(~J) of filt~r
3 has an opposite asymmetrical distortion. ~rom the mathe-.
.~ matical explanation given in said Patent Specification it follows that the desired relation is automaticall~
, .
obtained.when the impulse responses h2(t) and h3(t) of 20~ bandpass fllters~2~and 3 satisfy the equations:
(t) - hL(t) cos ~ t (1) ; h3(t? = hL(t) 5in W m ; (2) wherein hL(tj is the impulse response of a given band-pass~filter.
;; 25~ It is~slmple to prove mathematically that a~passband~signal which~ls 0btained at the transmitter :~89~2E~
PHN. 8414.
, end by modulating a quadrature carrier in accordance with an information-carrying baseband signal, can be ~iltered and demodulated at the receiver end by means of the arrangement of Fig. 1 by feeding modulator 4 ~` 5 with the quadrature carrier at output 72 of carrier source 7 and by feeding modulator 5 with the in-phase carrier at output 71 of carrier source 7 and by further-more subtracting the output signals of modulators 4 and 5 from one another in combination circuit 8.
With QAM signals the ampli-tudes of an in-~ phase carrier and a quadrature carrier of the same fre-; quency are simultaneously modulated at the receiver end.
,~, ; By making a double version of the arrangement of ~ig. 1 wherein filters 2 and 3 are used jointly, both the base-band signal~ carrled by the in-phase carrier and the base-band signal carried by the quadrature carrier can be re-oovere~d in the manner explained above.
A disadvantage of an analog implementation of the arrangement of Fig. 1 is the fact that the elimi-. .
nation of asymmetrical distortions in the transfer ch~-; ~ racteristics of ~ilters 2 and 3 are based on a compensa-tion technique and, consequently, imposes high require-ments on modulators 4 and 5 as regards dc-offset and other imper~ectlons whioh are dlfficult to avoid in 2~ analog circuits. A further disadvantage~ also with a hybrid construction according to the abo~e-mentioned : .: . ~ : - : : ~ :
., . . ~ , . . .. . ..
,5 .
PHN, 8414, ~ Patent Specification is the fact that, once such an - arrangement is i~plemented completely integrated in one or more semiconductor bodies, certain parameters such as filter characteristics are hard to ~odify so that , ~ 5 the arrangement can not be programmed These drawbacks l can be obviated by a *igital implementation of the ar-, .
rangement of Flg ` A first digital embodiment can be obtained I ~ ~ by connectlng in Fig 1 before input 1 an ADC circuit and after output 9 a DAC circuit and by furthermore re-placing the component parts such as filters 2 and 3, modulators 4 and 5, carrier source 7 and linear combi-~:. :: ; ' i~ nation circuit 8 by their digital equivalents which are ¦ ~ ~ ; known per se This direct translation from analog-to-I ~ !
~ 15 ~ dlgital implementation would, however, lead to a digital f:~ arrangement in which all component parts process signal f ~ samples occurring with a sampling frequency which, in ~1 accordancq with the known sampling theorem is equal to at least twlce the highest frequency in the signals 'I ' : . ' ' to be proce~sed, which, in this case, would mean twice the highest frequency in the signal applied to input 1 The number~of processing operations per unit of time and, consequently, the required computation speed of the digital arrangement~directly depends on the sampling ; 2~5 ~ ~ frequ~ency;of the~signal samples ~or realizing the ar-r~nge.~nt as a~ tegraLed oircult in one or more semi-~8~
PHN. 8414 .
conductor bodies or for the realization by means of a so-called micro~processor it is of the utmost import-ance that the required computation speed is reduced to the lowest possible values. In the digital embodiment of the filter and demodulation arrangement, whose block diagram is shown in Fig. 2, a considerable reduction in the internal processing speed in comparison with the first digital embodiment above explained is obtained by using the measures according to the invention.
- 10 ~ In Fig. 2 the ADC circuit at the input and the DAC circuit at the output are not shown because the arrangement is also suitable for applications in which the passband signal is alread~r available in digital , form or in which the recovered baseband signal is requir-15~ ed in digital form. In prevailing cases these circuits may be added in known manner.
: : ' To a digital input 10 of the arrangement in Fig. 2 a digital signal is appl:ied having a sampling , frequency f~I = 1/TH which is equal to at least twice the highest frequency in the equivalent analog signal which~ls derived~from the transmission path. Input 10 ls conneoted to two interpolating digital filters 2~
and 30 whlch are oontrolled by a control circuit 60. ~ -Thls control circuit 60 has an output 610 at which a 25; ~ control~signal having a frequency fH lS available and an output 620 at which~a control signal having a ~ , . , ~8~
, PHN. 8414.
25-3_1977.
frequency fL is available, wherein fL = 1/TL is equal to at least twice the hlghest frequency in the equi~a-lent analog baseband signal. There is a rational pro-portion between the frequencies fH and fL. Digital filters 20 and 30 are bandpass filters and have digi$al impulse ~sponses h20 (nTH) an~ h30(nTH) whiCh are given by the equations: ' ' -h20(nTH) = hL(nTH) coS(n~mTH) (3) , h30(~TH) = hL(nT~I) sin(n ~ m H) ' (1~) wherein hL(nTH) is the impulse response of a given digi-tal low-pas~ filter and ~m the central frequency of filters 20 and 30. The digital output signal of filter 20 is multiplied in a digital modulator 40 by a digital- -in-phase~ carrier which is available at an output 71 of a~ digital carrier source 70. Likewise the digital-output signal of filter 30 is multiplied in a digital, modulator 5~ by a digital quadrature carrier which is available at an output 720 o~ digital carrier source 70.
Carrler source 70 is controlled by control circuit 60.
The digital output signals of modulators 40 and 50 are added~in:~a:digital linear:combination circuit 80 so that at an output 90 o~ combination circuit 80 a filtered and :.
demodulatsd di;gital signal is obtained whose equi~alent L
analog A-gnaI~corrsspond~tc~ ths rsquired baseband sig-na .
~1~8~Z~
PHN. 8414.
; (2) Operation of the arran~ement_in_Fi~. 2.
For the description of the operation o~
the arrangement in ~ig. 2 it is now assumed by way of example that from the transmission path an analog signal is derived which is formed by a passband signal in the frequency band from 200 to 3200 Hz and by noise or other kinds of lnterferences whose fre~uency spectrum is li-mited to a frequency band from O to 7200 Hz by means of , ~ a simple analog filter, not further shown. This pass-1 10 band signal may, for example, bè derived from a trans-i;~ mltter wherein the amplitude of an inphase carrier~ having a frequenc~ of 1700 Hz is moclulated by a 2400 ¦ Baud data signal whose frequency spectrum is first` limited to a maximum frequency of 1500 Hz. By means of the fllter and demodulation arrangement this baseband data signal should be recovered from the passband signal and noise and other kinds of interferences in the fre-quency bands from O to 200 Hz and from 3200 to 7200 Hz ~ ~ , ~ ~ should be auppressed as much as possible. The highest ¦ 20 frequency in the analog signal derived ~rom the trans.
misslon~path amounts to 7200 Hz so that on the basis ~; of the sampling theorem this signal can be unambiguously .
converted into a digital signal having a sampling fre-quency f =~14.4~kHz br ~means of an ADC circuit. This H ~ ~
25~ ~ digltal~ signal is applied to both digital filters 20 - and 30~which have a passband from 200 to 3200 Hz. By , ~ , . ;
. .
PHN. 8414.
Z5-3-1977.
. .
means of equations (3) and (4) the lmpulse responses of these filters can be derived from the impulse res-: ponse`hL(nTH) of a digital low-pass filter having a bandwidth of 1500 Hz by choosing ~ m/2~r equal to 1700 Hz.
- 5 After the digital filter and demodulation processing .
. operations the baseband data signal is available in - ~ digital form at ou-tput 90.
- . As known this 2400 Baud data signal can be ; unambiguously represented by a digital signal having a sampling frequency fL = 2.4 kHz. This means that in com-. bination circuit 80 an addition of the signal samples .
~ at the output of digital modulators 40 and 50 need be ;
. performed every 1/2400 sec. only. As the output signals of these modulators at any sampling instant only depend ;15 ~ on the lnput slgnals avail~able at that instant because the modulators have no memory properties, both digital modulators 40, 50 and thoir digital carrier source 70 can be arranged for processing digital signals having a . sampling frequency ~L ~ 2.4 ~Hz instead o~ a sampling 2d ~ requenoy ~N = 14-4 kHz, To this end modulators 40~ 50 and carrier:source 70~ are connected to output 620 of : control circuit 60 instead of to output 610. This means a saving in the~number of computational~processes per unlt of;time:and~consequently a reduotlon in the lnternal 2:5 ~ processing~rate,~although this reduction, considered relatlve~ s~not; er~ large beoause the largest part ~8~
PHN. 8414.
` 25 3-1977-of the computational processes per unit of time takes place in digital filters 20 and 30.
A considerably more important saving in the number of computational processes per unit of time is obtained because this sampling frequency reduction can be extended to the inner part of both digital filters - 20 and 30 because these filters now onl~ need supply signal samples ha~ing a sampling frequency fL = 2.4 kHz to the two digital modulators 40 and 50. To this end these digital filters 20 and 30 are constructed as inter-polatine digital filters having an input sampling fre-quency fH = 14.4 kHz and an output sampling frequency fL = 2.4 kHz. Such filters are known per se and it may suffice here to refer to the references listed under (D).
An attractive implementation of an interpolating digital filter is described in Dutch Patent Application 74.1222 which has been laid open to public inspection, to which re~erenoe is made here also. This implementation enables ;the realization of any interpolating digital filter with ;20 a rational interpolation factor fH/fL. The use of inter-~ polating digital filters in the arrangement of Fig. 2 .
causes a considerably greater reduction in the internal processlng speed than the samping frequency reduction in the d~gital modulators because in the filters a con-~ siderably greater number~of computational processes takesplac~ye. unlt o- tl-e th~n in the modulators.
PHN. 8414-25-3- 1 977 ~
: Owing to the reduction accomp7ished in the inte~nal processing speed in the digital filter and , demodulation.arrangement th~ possibility i5 created to perform all multiplication processes which are required . 5 ~or filtering and demodulation by means o~ only one .
I : digital multiplier. All multiplications which are re- .
.
quired for computing a given signal sample at the out-put of the arrangement are successively performed by . this single digital multiplier in a manner known to . : 10 those skilled in the art.
.. -: :~: ~: ~: , . :
~:,: , ~: : , ::
.~ matical explanation given in said Patent Specification it follows that the desired relation is automaticall~
, .
obtained.when the impulse responses h2(t) and h3(t) of 20~ bandpass fllters~2~and 3 satisfy the equations:
(t) - hL(t) cos ~ t (1) ; h3(t? = hL(t) 5in W m ; (2) wherein hL(tj is the impulse response of a given band-pass~filter.
;; 25~ It is~slmple to prove mathematically that a~passband~signal which~ls 0btained at the transmitter :~89~2E~
PHN. 8414.
, end by modulating a quadrature carrier in accordance with an information-carrying baseband signal, can be ~iltered and demodulated at the receiver end by means of the arrangement of Fig. 1 by feeding modulator 4 ~` 5 with the quadrature carrier at output 72 of carrier source 7 and by feeding modulator 5 with the in-phase carrier at output 71 of carrier source 7 and by further-more subtracting the output signals of modulators 4 and 5 from one another in combination circuit 8.
With QAM signals the ampli-tudes of an in-~ phase carrier and a quadrature carrier of the same fre-; quency are simultaneously modulated at the receiver end.
,~, ; By making a double version of the arrangement of ~ig. 1 wherein filters 2 and 3 are used jointly, both the base-band signal~ carrled by the in-phase carrier and the base-band signal carried by the quadrature carrier can be re-oovere~d in the manner explained above.
A disadvantage of an analog implementation of the arrangement of Fig. 1 is the fact that the elimi-. .
nation of asymmetrical distortions in the transfer ch~-; ~ racteristics of ~ilters 2 and 3 are based on a compensa-tion technique and, consequently, imposes high require-ments on modulators 4 and 5 as regards dc-offset and other imper~ectlons whioh are dlfficult to avoid in 2~ analog circuits. A further disadvantage~ also with a hybrid construction according to the abo~e-mentioned : .: . ~ : - : : ~ :
., . . ~ , . . .. . ..
,5 .
PHN, 8414, ~ Patent Specification is the fact that, once such an - arrangement is i~plemented completely integrated in one or more semiconductor bodies, certain parameters such as filter characteristics are hard to ~odify so that , ~ 5 the arrangement can not be programmed These drawbacks l can be obviated by a *igital implementation of the ar-, .
rangement of Flg ` A first digital embodiment can be obtained I ~ ~ by connectlng in Fig 1 before input 1 an ADC circuit and after output 9 a DAC circuit and by furthermore re-placing the component parts such as filters 2 and 3, modulators 4 and 5, carrier source 7 and linear combi-~:. :: ; ' i~ nation circuit 8 by their digital equivalents which are ¦ ~ ~ ; known per se This direct translation from analog-to-I ~ !
~ 15 ~ dlgital implementation would, however, lead to a digital f:~ arrangement in which all component parts process signal f ~ samples occurring with a sampling frequency which, in ~1 accordancq with the known sampling theorem is equal to at least twlce the highest frequency in the signals 'I ' : . ' ' to be proce~sed, which, in this case, would mean twice the highest frequency in the signal applied to input 1 The number~of processing operations per unit of time and, consequently, the required computation speed of the digital arrangement~directly depends on the sampling ; 2~5 ~ ~ frequ~ency;of the~signal samples ~or realizing the ar-r~nge.~nt as a~ tegraLed oircult in one or more semi-~8~
PHN. 8414 .
conductor bodies or for the realization by means of a so-called micro~processor it is of the utmost import-ance that the required computation speed is reduced to the lowest possible values. In the digital embodiment of the filter and demodulation arrangement, whose block diagram is shown in Fig. 2, a considerable reduction in the internal processing speed in comparison with the first digital embodiment above explained is obtained by using the measures according to the invention.
- 10 ~ In Fig. 2 the ADC circuit at the input and the DAC circuit at the output are not shown because the arrangement is also suitable for applications in which the passband signal is alread~r available in digital , form or in which the recovered baseband signal is requir-15~ ed in digital form. In prevailing cases these circuits may be added in known manner.
: : ' To a digital input 10 of the arrangement in Fig. 2 a digital signal is appl:ied having a sampling , frequency f~I = 1/TH which is equal to at least twice the highest frequency in the equivalent analog signal which~ls derived~from the transmission path. Input 10 ls conneoted to two interpolating digital filters 2~
and 30 whlch are oontrolled by a control circuit 60. ~ -Thls control circuit 60 has an output 610 at which a 25; ~ control~signal having a frequency fH lS available and an output 620 at which~a control signal having a ~ , . , ~8~
, PHN. 8414.
25-3_1977.
frequency fL is available, wherein fL = 1/TL is equal to at least twice the hlghest frequency in the equi~a-lent analog baseband signal. There is a rational pro-portion between the frequencies fH and fL. Digital filters 20 and 30 are bandpass filters and have digi$al impulse ~sponses h20 (nTH) an~ h30(nTH) whiCh are given by the equations: ' ' -h20(nTH) = hL(nTH) coS(n~mTH) (3) , h30(~TH) = hL(nT~I) sin(n ~ m H) ' (1~) wherein hL(nTH) is the impulse response of a given digi-tal low-pas~ filter and ~m the central frequency of filters 20 and 30. The digital output signal of filter 20 is multiplied in a digital modulator 40 by a digital- -in-phase~ carrier which is available at an output 71 of a~ digital carrier source 70. Likewise the digital-output signal of filter 30 is multiplied in a digital, modulator 5~ by a digital quadrature carrier which is available at an output 720 o~ digital carrier source 70.
Carrler source 70 is controlled by control circuit 60.
The digital output signals of modulators 40 and 50 are added~in:~a:digital linear:combination circuit 80 so that at an output 90 o~ combination circuit 80 a filtered and :.
demodulatsd di;gital signal is obtained whose equi~alent L
analog A-gnaI~corrsspond~tc~ ths rsquired baseband sig-na .
~1~8~Z~
PHN. 8414.
; (2) Operation of the arran~ement_in_Fi~. 2.
For the description of the operation o~
the arrangement in ~ig. 2 it is now assumed by way of example that from the transmission path an analog signal is derived which is formed by a passband signal in the frequency band from 200 to 3200 Hz and by noise or other kinds of lnterferences whose fre~uency spectrum is li-mited to a frequency band from O to 7200 Hz by means of , ~ a simple analog filter, not further shown. This pass-1 10 band signal may, for example, bè derived from a trans-i;~ mltter wherein the amplitude of an inphase carrier~ having a frequenc~ of 1700 Hz is moclulated by a 2400 ¦ Baud data signal whose frequency spectrum is first` limited to a maximum frequency of 1500 Hz. By means of the fllter and demodulation arrangement this baseband data signal should be recovered from the passband signal and noise and other kinds of interferences in the fre-quency bands from O to 200 Hz and from 3200 to 7200 Hz ~ ~ , ~ ~ should be auppressed as much as possible. The highest ¦ 20 frequency in the analog signal derived ~rom the trans.
misslon~path amounts to 7200 Hz so that on the basis ~; of the sampling theorem this signal can be unambiguously .
converted into a digital signal having a sampling fre-quency f =~14.4~kHz br ~means of an ADC circuit. This H ~ ~
25~ ~ digltal~ signal is applied to both digital filters 20 - and 30~which have a passband from 200 to 3200 Hz. By , ~ , . ;
. .
PHN. 8414.
Z5-3-1977.
. .
means of equations (3) and (4) the lmpulse responses of these filters can be derived from the impulse res-: ponse`hL(nTH) of a digital low-pass filter having a bandwidth of 1500 Hz by choosing ~ m/2~r equal to 1700 Hz.
- 5 After the digital filter and demodulation processing .
. operations the baseband data signal is available in - ~ digital form at ou-tput 90.
- . As known this 2400 Baud data signal can be ; unambiguously represented by a digital signal having a sampling frequency fL = 2.4 kHz. This means that in com-. bination circuit 80 an addition of the signal samples .
~ at the output of digital modulators 40 and 50 need be ;
. performed every 1/2400 sec. only. As the output signals of these modulators at any sampling instant only depend ;15 ~ on the lnput slgnals avail~able at that instant because the modulators have no memory properties, both digital modulators 40, 50 and thoir digital carrier source 70 can be arranged for processing digital signals having a . sampling frequency ~L ~ 2.4 ~Hz instead o~ a sampling 2d ~ requenoy ~N = 14-4 kHz, To this end modulators 40~ 50 and carrier:source 70~ are connected to output 620 of : control circuit 60 instead of to output 610. This means a saving in the~number of computational~processes per unlt of;time:and~consequently a reduotlon in the lnternal 2:5 ~ processing~rate,~although this reduction, considered relatlve~ s~not; er~ large beoause the largest part ~8~
PHN. 8414.
` 25 3-1977-of the computational processes per unit of time takes place in digital filters 20 and 30.
A considerably more important saving in the number of computational processes per unit of time is obtained because this sampling frequency reduction can be extended to the inner part of both digital filters - 20 and 30 because these filters now onl~ need supply signal samples ha~ing a sampling frequency fL = 2.4 kHz to the two digital modulators 40 and 50. To this end these digital filters 20 and 30 are constructed as inter-polatine digital filters having an input sampling fre-quency fH = 14.4 kHz and an output sampling frequency fL = 2.4 kHz. Such filters are known per se and it may suffice here to refer to the references listed under (D).
An attractive implementation of an interpolating digital filter is described in Dutch Patent Application 74.1222 which has been laid open to public inspection, to which re~erenoe is made here also. This implementation enables ;the realization of any interpolating digital filter with ;20 a rational interpolation factor fH/fL. The use of inter-~ polating digital filters in the arrangement of Fig. 2 .
causes a considerably greater reduction in the internal processlng speed than the samping frequency reduction in the d~gital modulators because in the filters a con-~ siderably greater number~of computational processes takesplac~ye. unlt o- tl-e th~n in the modulators.
PHN. 8414-25-3- 1 977 ~
: Owing to the reduction accomp7ished in the inte~nal processing speed in the digital filter and , demodulation.arrangement th~ possibility i5 created to perform all multiplication processes which are required . 5 ~or filtering and demodulation by means o~ only one .
I : digital multiplier. All multiplications which are re- .
.
quired for computing a given signal sample at the out-put of the arrangement are successively performed by . this single digital multiplier in a manner known to . : 10 those skilled in the art.
.. -: :~: ~: ~: , . :
~:,: , ~: : , ::
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;
An arrangement for filtering and demodulat-ing passband signals which are obtained by modulating a carrier in accordance with a baseband signal whose bandwidth is limited to a given maximum frequency, which arrangement is provided with means for filtering the passband signals according to a first and a second bandpass characteristic for generating first and second filtered passband signals, which bandpass characteris-tics, apart from the asymmetrical distortion relative to their central frequency, are versions from one an-other shifted 90° in phase, means for demodulating the first and second filtered passband signals with an in-phase carrier and a quadrature carrier respectively for generating first and second demodulated signals, and means for combining the first and second demodulated signals, characterized in that all said means for filter-ing, demodulating and combining are digital means, the digital filter means are furthermore provided with means for sampling frequency reduction for converting signal samples of the passband signals occurring with a first sampling frequency which is higher than twice the highest frequency in the passband signals, into signal samples of the first and second filtered pass-band signals occurring with a second sampling frequency which is not higher than twice said maximum frequency of the baseband signal, and the digital means for demodulating and combining are arranged for processing signal samples occurring with the same second sampling frequency.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;
An arrangement for filtering and demodulat-ing passband signals which are obtained by modulating a carrier in accordance with a baseband signal whose bandwidth is limited to a given maximum frequency, which arrangement is provided with means for filtering the passband signals according to a first and a second bandpass characteristic for generating first and second filtered passband signals, which bandpass characteris-tics, apart from the asymmetrical distortion relative to their central frequency, are versions from one an-other shifted 90° in phase, means for demodulating the first and second filtered passband signals with an in-phase carrier and a quadrature carrier respectively for generating first and second demodulated signals, and means for combining the first and second demodulated signals, characterized in that all said means for filter-ing, demodulating and combining are digital means, the digital filter means are furthermore provided with means for sampling frequency reduction for converting signal samples of the passband signals occurring with a first sampling frequency which is higher than twice the highest frequency in the passband signals, into signal samples of the first and second filtered pass-band signals occurring with a second sampling frequency which is not higher than twice said maximum frequency of the baseband signal, and the digital means for demodulating and combining are arranged for processing signal samples occurring with the same second sampling frequency.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7605726 | 1976-05-28 | ||
| NLAANVRAGE7605726,A NL175575C (en) | 1976-05-28 | 1976-05-28 | FILTER AND DEMODULATION DEVICE. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1089028A true CA1089028A (en) | 1980-11-04 |
Family
ID=19826272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA279,169A Expired CA1089028A (en) | 1976-05-28 | 1977-05-26 | Filter and demodulation arrangement |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4130806A (en) |
| JP (1) | JPS52146156A (en) |
| AU (1) | AU514328B2 (en) |
| BE (1) | BE855101A (en) |
| CA (1) | CA1089028A (en) |
| DE (1) | DE2721850C2 (en) |
| FR (1) | FR2361772A1 (en) |
| GB (1) | GB1529544A (en) |
| NL (1) | NL175575C (en) |
| SE (1) | SE413273B (en) |
Families Citing this family (56)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5821466B2 (en) * | 1979-02-13 | 1983-04-30 | 日本電信電話株式会社 | Digital signal reception method |
| US4309772A (en) * | 1980-01-24 | 1982-01-05 | Motorola, Inc. | Soft quantizer for FM radio binary digital signaling |
| US4415918A (en) * | 1981-08-31 | 1983-11-15 | Rca Corporation | Digital color television signal demodulator |
| DE3174147D1 (en) * | 1981-11-30 | 1986-04-24 | Ibm | Method for receiving a data signal with double side-band quadrature carrier modulation |
| US4592074A (en) * | 1984-06-01 | 1986-05-27 | Rockwell International Corporation | Simplified hardware implementation of a digital IF translator |
| FR2568074B1 (en) * | 1984-07-17 | 1992-01-10 | Lignes Telegraph Telephon | DEMODULATOR OF ELECTRIC SIGNALS WITH MULTIPLE AMPLITUDE AND PHASE STATES FOR DATA TRANSMISSION EQUIPMENT. |
| US4893316A (en) * | 1985-04-04 | 1990-01-09 | Motorola, Inc. | Digital radio frequency receiver |
| DE3688170T2 (en) * | 1985-04-04 | 1993-07-08 | Motorola Inc | DIGITAL ZERO-MF SELECTIVE LEVEL. |
| NL8700244A (en) * | 1987-02-02 | 1988-09-01 | Philips Nv | MODULATOR WITH A COMB FILTER. |
| US4811362A (en) * | 1987-06-15 | 1989-03-07 | Motorola, Inc. | Low power digital receiver |
| US4910752A (en) * | 1987-06-15 | 1990-03-20 | Motorola, Inc. | Low power digital receiver |
| DE4021226A1 (en) * | 1990-07-04 | 1992-01-16 | Thomson Ind Technology Ass S A | Voltage - controlled filter circuit - uses filter network with two filters receiving common control voltage and difference amplifier |
| US5212817A (en) * | 1990-09-14 | 1993-05-18 | Atkinson Noel D | Ultra high speed scan system |
| DE4132907A1 (en) * | 1991-10-04 | 1993-04-08 | Thomson Brandt Gmbh | FILTER ARRANGEMENT |
| DE69431223T2 (en) * | 1993-06-29 | 2006-03-02 | Sony Corp. | Apparatus and method for sound transmission |
| 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 |
| US6061551A (en) | 1998-10-21 | 2000-05-09 | Parkervision, Inc. | Method and system for down-converting electromagnetic signals |
| US6694128B1 (en) | 1998-08-18 | 2004-02-17 | Parkervision, Inc. | Frequency synthesizer using universal frequency translation technology |
| 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 |
| US7027786B1 (en) | 1998-10-21 | 2006-04-11 | Parkervision, Inc. | Carrier and clock recovery using universal frequency translation |
| US7295826B1 (en) | 1998-10-21 | 2007-11-13 | Parkervision, Inc. | Integrated frequency translation and selectivity with gain control functionality, and applications thereof |
| US6542722B1 (en) | 1998-10-21 | 2003-04-01 | Parkervision, Inc. | Method and system for frequency up-conversion with variety of transmitter configurations |
| US6061555A (en) * | 1998-10-21 | 2000-05-09 | Parkervision, Inc. | Method and system for ensuring reception of a communications signal |
| US6049706A (en) * | 1998-10-21 | 2000-04-11 | Parkervision, Inc. | Integrated frequency translation and selectivity |
| US6370371B1 (en) | 1998-10-21 | 2002-04-09 | Parkervision, Inc. | Applications of universal frequency translation |
| 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 |
| US7236754B2 (en) | 1999-08-23 | 2007-06-26 | Parkervision, Inc. | Method and system for frequency up-conversion |
| 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 |
| US7006805B1 (en) | 1999-01-22 | 2006-02-28 | Parker Vision, Inc. | Aliasing communication system with multi-mode and multi-band functionality and embodiments thereof, such as the family radio service |
| US6879817B1 (en) | 1999-04-16 | 2005-04-12 | Parkervision, Inc. | DC offset, re-radiation, and I/Q solutions using universal frequency translation technology |
| US6873836B1 (en) | 1999-03-03 | 2005-03-29 | Parkervision, Inc. | Universal platform module and methods and apparatuses relating thereto enabled by universal frequency translation technology |
| 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 |
| US7110435B1 (en) | 1999-03-15 | 2006-09-19 | Parkervision, Inc. | Spread spectrum applications of universal frequency translation |
| US7693230B2 (en) | 1999-04-16 | 2010-04-06 | Parkervision, Inc. | Apparatus and method of differential IQ frequency up-conversion |
| 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 |
| US7065162B1 (en) | 1999-04-16 | 2006-06-20 | Parkervision, Inc. | Method and system for down-converting an electromagnetic signal, and transforms for same |
| US7054296B1 (en) | 1999-08-04 | 2006-05-30 | Parkervision, Inc. | Wireless local area network (WLAN) technology and applications including techniques of universal frequency translation |
| US7072390B1 (en) | 1999-08-04 | 2006-07-04 | Parkervision, Inc. | Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments |
| US8295406B1 (en) | 1999-08-04 | 2012-10-23 | Parkervision, Inc. | Universal platform module for a plurality of communication protocols |
| US7082171B1 (en) | 1999-11-24 | 2006-07-25 | Parkervision, Inc. | Phase shifting applications of universal frequency translation |
| US6963734B2 (en) | 1999-12-22 | 2005-11-08 | Parkervision, Inc. | Differential frequency down-conversion using techniques of universal frequency translation technology |
| US7292835B2 (en) | 2000-01-28 | 2007-11-06 | Parkervision, Inc. | Wireless and wired cable modem applications of universal frequency translation technology |
| US7010286B2 (en) | 2000-04-14 | 2006-03-07 | Parkervision, Inc. | Apparatus, system, and method for down-converting and up-converting electromagnetic signals |
| GB2362279B (en) * | 2000-05-12 | 2004-12-29 | Global Silicon Ltd | Radio receiver |
| US7554508B2 (en) | 2000-06-09 | 2009-06-30 | Parker Vision, Inc. | Phased array antenna applications on universal frequency translation |
| US7010559B2 (en) | 2000-11-14 | 2006-03-07 | Parkervision, Inc. | Method and apparatus for a parallel correlator and applications thereof |
| US7454453B2 (en) | 2000-11-14 | 2008-11-18 | Parkervision, Inc. | Methods, systems, and computer program products for parallel correlation and applications thereof |
| US7085335B2 (en) | 2001-11-09 | 2006-08-01 | Parkervision, Inc. | Method and apparatus for reducing DC offsets in a communication system |
| US7072427B2 (en) | 2001-11-09 | 2006-07-04 | Parkervision, Inc. | Method and apparatus for reducing DC offsets in a communication system |
| US6975848B2 (en) | 2002-06-04 | 2005-12-13 | Parkervision, Inc. | Method and apparatus for DC offset removal in a radio frequency communication channel |
| US7321640B2 (en) | 2002-06-07 | 2008-01-22 | Parkervision, Inc. | Active polyphase inverter filter for quadrature signal generation |
| 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 |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3493876A (en) * | 1966-06-28 | 1970-02-03 | Us Army | Stable coherent filter for sampled bandpass signals |
| US3525541A (en) * | 1969-03-24 | 1970-08-25 | Clifford H Snyder Jr | Quick disconnect coupling for flanged conduits |
| NL7101037A (en) * | 1971-01-27 | 1972-07-31 | Philips Nv | |
| US3971996A (en) * | 1973-01-18 | 1976-07-27 | Hycom Incorporated | Phase tracking network |
| US3943448A (en) * | 1974-09-11 | 1976-03-09 | Hycom Incorporated | Apparatus and method for synchronizing a digital modem using a random multilevel data signal |
| NL168669C (en) * | 1974-09-16 | 1982-04-16 | Philips Nv | INTERPOLING DIGITAL FILTER WITH INPUT BUFFER. |
-
1976
- 1976-05-28 NL NLAANVRAGE7605726,A patent/NL175575C/en not_active IP Right Cessation
-
1977
- 1977-05-14 DE DE2721850A patent/DE2721850C2/en not_active Expired
- 1977-05-23 US US05/799,884 patent/US4130806A/en not_active Expired - Lifetime
- 1977-05-25 AU AU25485/77A patent/AU514328B2/en not_active Expired
- 1977-05-25 JP JP6001177A patent/JPS52146156A/en active Pending
- 1977-05-25 FR FR7715898A patent/FR2361772A1/en active Granted
- 1977-05-25 SE SE7706093A patent/SE413273B/en not_active IP Right Cessation
- 1977-05-25 GB GB22042/77A patent/GB1529544A/en not_active Expired
- 1977-05-26 BE BE177963A patent/BE855101A/en unknown
- 1977-05-26 CA CA279,169A patent/CA1089028A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2361772A1 (en) | 1978-03-10 |
| BE855101A (en) | 1977-11-28 |
| SE413273B (en) | 1980-05-12 |
| NL175575B (en) | 1984-06-18 |
| AU514328B2 (en) | 1981-02-05 |
| DE2721850C2 (en) | 1983-06-09 |
| AU2548577A (en) | 1978-11-30 |
| JPS52146156A (en) | 1977-12-05 |
| US4130806A (en) | 1978-12-19 |
| NL175575C (en) | 1984-11-16 |
| DE2721850A1 (en) | 1977-12-08 |
| GB1529544A (en) | 1978-10-25 |
| NL7605726A (en) | 1977-11-30 |
| SE7706093L (en) | 1977-11-29 |
| FR2361772B1 (en) | 1981-08-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |