GB2161344A - Transmission of digital data - Google Patents

Transmission of digital data Download PDF

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Publication number
GB2161344A
GB2161344A GB08417283A GB8417283A GB2161344A GB 2161344 A GB2161344 A GB 2161344A GB 08417283 A GB08417283 A GB 08417283A GB 8417283 A GB8417283 A GB 8417283A GB 2161344 A GB2161344 A GB 2161344A
Authority
GB
United Kingdom
Prior art keywords
sub
channel
system
digital data
channels
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.)
Withdrawn
Application number
GB08417283A
Inventor
Timothy James Moulsley
Peter John Mabey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Electronics UK Ltd
Original Assignee
Philips Electronics UK Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Philips Electronics UK Ltd filed Critical Philips Electronics UK Ltd
Priority to GB08417283A priority Critical patent/GB2161344A/en
Publication of GB2161344A publication Critical patent/GB2161344A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/12Frequency diversity
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/02Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/04Arrangements for detecting or preventing errors in the information received by diversity reception using frequency diversity

Abstract

The transmission of digital data over a data link, particularly an H.F. radio link, can be corrupted by narrow-band, high level interference signals randomly distributed in frequency. The uncorrupted transmission of data can be made more possible by a frequency diversity digital data transmission system in which a signal channel is divided into a plurality of lesser bandwidth sub-channels, each of which is modulated across substantially its entire bandwidth by a multi-level, spectrally efficient modulation scheme, for example 8PSK, 16QAM, 64QAM. In a receiver the sub-channels are examined for narrow-band interference and the data signal is demodulated using a decision algorithm based on the sub-channel outputs, and an assessment of sub-channel reliability. <IMAGE>

Description

SPECIFICATION Transmission of digital data The present invention relates to the transmission of digital data in the presence of narrow-band interference, A problem when transmitting digital information over a data link, which may be an H.F. radio link, is that the information becomes corrupted in transmission by narrow-band, high level interference signals randomly distributed in frequency. Known systems for combating such interference involve reducing the data rate in a given bandwidth or, conversely, increasing the bandwidth for the same data rate.

An object of the present invention is to reduce the effects of narrow-band interference when transmitting digital information at a high data rate over a data link of a predetermined bandwidth.

According to the present invention there is provided a digital data transmission system in which a transmission channel of defined bandwidth is divided into a plurality of lesser bandwidth subchannels, digital data informatin to be transmitted is modulated over substantially the entire bandwidth of each of the said sub-channels using a multi-level modulation scheme and at the receiver the digital data is recovered from at least one of the subchannels.

By using a combination of frequency diversity and a spectrally efficient, multi-level modulation sheme, the chance of at least one of the frequency diversity sub-channels being received uncorrupted is much greater than the chance of the complete channel being interference free. A further improvement can e gained by making use of all the received subchannels.

Suitable multi-level modulation schemes may comprise for example, 8PSK (8 phase shift keying), 16QAM (16 quadrature amplitude modulation) or 640AM.

At the receiver, the sub-channels are dmodulated and either steps are taken to select the best subchannel at any instance or the data is recovered by making a decision using all the sub-channel outputs.

The present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure lisa graph of an example of H.F.

interference, and Figures 2 and 3 are block schematic circuit diagrams of a transmitter and a receiver, respectively, suitable for use with the data transmission system in accordance with the present invention.

Referring to Figure 1, there is shown a graph of power Pin 10dB per division against frequency F in 1kHz per division and illustrates typical H.F. interference. Part of the interference consists of a background of noise-like signals, but another part, the large amplitude peaks in Figure 1, consists of narrow-band interference. In many cases the narrow-band interference is the dominant cause of errors at the output of the receiver.

Thus, taking as an example a transmission channel of 5.0kHz occupied by a signal with a data rate of 2.4k bits/sec., if the channel is badly corrupted by narrow-band interference then the entire signal is unusable. Since as is shown in Figure 1 the narrowband noise is not distributed uniformly across the frequency band, then adopting frequency diversity using several, for example 5, sub-channels within an overall channel it is likely that at any instant in time at least one of the sub-channels is free from narrow-band interference and the data is received uncorrupted. Because all the message information is transmitted in each sub-channel, then the transmitted data can be recovered even if one or more sub-channels are unusable.This frequency diversity can be achieved without reduction in data rate if a spectrally efficient multi-level modulation scheme is used so that each sub-channel of for example 1 kHz bandwidth is sending data at 2.4k bits/sec. Such multi-level modulation schemes may comprise, for exm ple, 8PSK, 160AM or 640AM. At a receiver all the sub-channels are received and demodulated and either digital data is recovered from one of the sub-channels, that is the one having least interference, or the data value is recovered by making a decision vased on all the sub-channel outputs.

For example, considering single data bits, the following algorithm could be used to obtain the recovered data value (D): <img class="EMIRef" id="027197334-00010001" />

where Di is the output of the 1-th sub-chanel and wi is the a weighting factor applied to the i-th sub-channel output. The decision alogorithm can take various forms. For example, if the weights are all unity then it is equivlent to majority decision decoding. If all the weights are zero except one then this amounts to selection of a single sub-channel. If the weights are chosen according to the estimated reliability of the associated sub-channels then this is a weighted combining scheme. The reliability of each subchannel could be determined, for example, by the signal-to-noise ratio in that sub-channel.The data reliability can be estimated either on a bit by bit basis or using a short term average. A new set of weights could be determined for each received bit, or alternatively, less frequently.

Figure 2 shows a transmitter system which comprises a 2.4k bits/second digital data encoder 10 which is coupled to five multi-level modulators 12, 14, 16, 18 and 20 which may comprise 8PSK, 16QAM or 640AM modulator. The five sub-carriers f1 to (f1 +4kHz) spaced one from another by 1 kHz are are generated by oscillators 22, 24, 26, 28 and 30, respectively and are modulated according to the predetermined multilevel modulation scheme to form a frequency diversity signal. This signal is applied to a transmitter 32 which could be conventional single sideband (SSB) transmitter accepting a 5kHz bandwidth signal. The transmitter output is applied to an antenna 34.

The reciever system shown in Figure 3 comprises a receiver 38 which could be a conventional SSB receiver which is connected to an antenna 36 and has an output bandwidth of 5kHz. Each of the sub-channels of the frequency diversity signal is applied to a respective demodulator 40,42,44,46 and 48 which has its own sub-carrierfrequency generator. The detected signals from the demodulators 40 to 48 are applied to a decision unit 52 which makes a decision based on a decision algorithm as to the correct output data value, based on the sub-channel outputs and the assessment of subchannel reliability made by a reliability measurement unit 50. The decision making process will usually be continuous because the occurrence of narrow-band interference cannot be predicted. The output of the decision unit 52 is supplied to a data decoder 54.

Various ways may be used for determining the degree to which each of the sub-channels is corrupted by H.F. narrow-band interference. For example, a comparison can be made between the amplitude of the signal in each of the respective subchannels and the mean amplitude for all the subchannels. It is then reasonable to assume that any sub-channel with an amplitude much larger than the mean is corrupted by interference. The phase jitter on each of the sub-carriers could also be used as an indication of interference. Another method would be for the encoder 10 to insert error detection or correction coding into the encoded signal and for this coding to be used in the receiver to determine which sub-channels are corrupted by interference.

The digital information bits applied to each of the modulators 12 to 20 in Figure 2 need not necessarily be transmitted on all the sub-channels simul taneously. For example, the sub-channel signals could each be delayed in time by a different amount resulting in both time and frequency diversity.

However, the complete message would still be transmitted down each sub-channel. At the receiver corresponding time delays would be required after demodulation to enable correct combining of the sub-channel signals.

Not shown in Figure 3, the sub-channel signal combination with appropriate weighting factors could be carried out before demodulation. In this case the sub-carriers should be phase locked to each other. This phase locking would also be desirable in minimising the peak-to-mean power ratio of the transmitted signal.

Although not shown, instead of using a single receiver one could use five separate receivers each one assigned to a different channel.

The modems 12 to 20 and 40 to 48 may be serial modems with or without adaptive equalisers or parallel modems, although the latter are more complicated technically and have a peak power limitation.

The transmission system in accordance with the present invention is particularly applicable to groundwave communication over distances of up to about 150 km, but could be used over longer ranges with adaptive equalisation.

Claims (12)

1. A digital data transmission system in which a transmission channel of defined bandwidth is divided into a plurality of lesser bandwidth subchannels, digital data information to be transmitted is modulated over substantially the entire bandwidth of each of the said sub-channels using a multi-level modulation scheme and at the receiverthe digital data is recovered from at least one of the subchannels.
2. Atransmission system as claimed in Claim 1, wherein the receiver includes means for examining each of the sub-channels and for selecting a subchannel having the minimum of narrow-band noise for further processing.
3. Atransmission system as claimed in Claim 2, wherein in encoding the digital data an error detection code is applied and in the receiver, said means detects the number of errors in each sub-channel signal.
4. Atransmission system as claimed in Claim 2, wherein said means compares the digital data signals in each of said sub-channels and a majority voting system is used to recover the transmitted data.
5. Atransmission system as claimed in Claim 2, wherein said means compares the amplitude of the signal in each sub-channel with an expected amplitude and determines which sub-channel(s) at any one time is (or are) deemed to be interference free.
6. Atransmission system as claimed in claim 1, wherein the receiver includes means for combining the signals on the respective sub-channels and providing an output digital signal for further processing.
7. Atransmission system as claimed in Claim 6, wherein the receiver includes means for estimating the reliability of each of the sub-channel data signals and using this information in an algorithm to combine the sub-channel signals.
8. Atransmission system as claimed in any one of Claims 1 to 7, wherein the multi-level modulation scheme is 16QAM (quadrature amplitude modulation).
9. Atransmission system as claimed in any one of Claims 1 to 7, wherein the multi-level modulation scheme is 640AM
10. Atransmission system as claimed in any one of Claims 1 to 7, wherein the multi-level modulation scheme is 8PSK (phase shift keying).
11. Atransmission system as claimed in any one of Claims 1 to 10, wherein the digital signals used to modulate each of the sub-carriers are delayed in time by different amounts.
12. A digital data transmission system substantially as hereinbefore described with reference to the accompanying drawings.
GB08417283A 1984-07-06 1984-07-06 Transmission of digital data Withdrawn GB2161344A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08417283A GB2161344A (en) 1984-07-06 1984-07-06 Transmission of digital data

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08417283A GB2161344A (en) 1984-07-06 1984-07-06 Transmission of digital data

Publications (1)

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GB2161344A true GB2161344A (en) 1986-01-08

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Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238813A2 (en) * 1986-02-27 1987-09-30 Datawatt BV Method for transmitting data over mains lines
EP0283299A2 (en) * 1987-03-20 1988-09-21 Nippon Telegraph And Telephone Corporation Radio receiver
GB2208985A (en) * 1987-08-24 1989-04-19 Kokusai Denshin Denwa Co Ltd A radio communication system
WO1991018458A1 (en) * 1990-05-11 1991-11-28 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland A high frequency multichannel diversity differential phase shift (dpsk) communications system
WO1992004783A1 (en) * 1990-09-07 1992-03-19 Telefunken Systemtechnik Gmbh Method of determining the frequency deviation in digital communications transmissions
WO1993009618A1 (en) * 1991-10-31 1993-05-13 Massachusetts Institute Of Technology Communication system utilizing self-similar signals
FR2755460A1 (en) * 1996-11-07 1998-05-07 Kiekert Ag motor vehicle with a locking system centralizes a control device remote
US6049706A (en) 1998-10-21 2000-04-11 Parkervision, Inc. Integrated frequency translation and selectivity
WO2000020712A1 (en) * 1998-10-05 2000-04-13 Lear Automotive Dearborn, Inc. Multiple channel remote keyless entry system
WO2000024120A1 (en) * 1998-10-21 2000-04-27 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6061555A (en) 1998-10-21 2000-05-09 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6061551A (en) 1998-10-21 2000-05-09 Parkervision, Inc. Method and system for down-converting electromagnetic signals
US6091940A (en) 1998-10-21 2000-07-18 Parkervision, Inc. Method and system for frequency up-conversion
GB2349544A (en) * 1989-05-30 2000-11-01 Secr Defence Covert communication system
US6370371B1 (en) 1998-10-21 2002-04-09 Parkervision, Inc. Applications of universal frequency translation
US6542722B1 (en) 1998-10-21 2003-04-01 Parkervision, Inc. Method and system for frequency up-conversion with variety of transmitter configurations
US6560301B1 (en) 1998-10-21 2003-05-06 Parkervision, Inc. Integrated frequency translation and selectivity with a variety of filter embodiments
US6694128B1 (en) 1998-08-18 2004-02-17 Parkervision, Inc. Frequency synthesizer using universal frequency translation technology
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
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
EP1551127A1 (en) * 2001-12-21 2005-07-06 Mitsubishi Denki Kabushiki Kaisha Radio communication system and transmitter for implementing frequency diversity
WO2006120319A1 (en) * 2005-05-10 2006-11-16 Societe Stantec Device and method for receiving binary data radio frequency
US7519400B2 (en) 2005-05-27 2009-04-14 Dei Headquarters, Inc. Multi-modulation remote control communication system
US7653158B2 (en) 2001-11-09 2010-01-26 Parkervision, Inc. Gain control in a communication channel
US7693230B2 (en) 1999-04-16 2010-04-06 Parkervision, Inc. Apparatus and method of differential IQ frequency up-conversion
US7724845B2 (en) 1999-04-16 2010-05-25 Parkervision, Inc. Method and system for down-converting and electromagnetic signal, and transforms for same
US7773688B2 (en) 1999-04-16 2010-08-10 Parkervision, Inc. Method, system, and apparatus for balanced frequency up-conversion, including circuitry to directly couple the outputs of multiple transistors
US7822401B2 (en) 2000-04-14 2010-10-26 Parkervision, Inc. Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US7865177B2 (en) 1998-10-21 2011-01-04 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US7894789B2 (en) 1999-04-16 2011-02-22 Parkervision, Inc. Down-conversion of an electromagnetic signal with feedback control
US7929638B2 (en) 1999-04-16 2011-04-19 Parkervision, Inc. Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US7991815B2 (en) 2000-11-14 2011-08-02 Parkervision, Inc. Methods, systems, and computer program products for parallel correlation and applications thereof
US8019291B2 (en) 1998-10-21 2011-09-13 Parkervision, Inc. Method and system for frequency down-conversion and frequency up-conversion
US8160196B2 (en) 2002-07-18 2012-04-17 Parkervision, Inc. Networking methods and systems
US8233855B2 (en) 1998-10-21 2012-07-31 Parkervision, Inc. Up-conversion based on gated information signal
US8295406B1 (en) 1999-08-04 2012-10-23 Parkervision, Inc. Universal platform module for a plurality of communication protocols
US8407061B2 (en) 2002-07-18 2013-03-26 Parkervision, Inc. Networking methods and systems

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2023971A (en) * 1978-05-10 1980-01-03 Nippon Telegraph & Telephone Digital signal transmission system
GB2092415A (en) * 1981-01-29 1982-08-11 Secr Defence Digital communications system
EP0065764B1 (en) * 1981-05-27 1986-03-26 Siemens Aktiengesellschaft Digital radio system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2023971A (en) * 1978-05-10 1980-01-03 Nippon Telegraph & Telephone Digital signal transmission system
GB2092415A (en) * 1981-01-29 1982-08-11 Secr Defence Digital communications system
EP0065764B1 (en) * 1981-05-27 1986-03-26 Siemens Aktiengesellschaft Digital radio system

Cited By (73)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238813A2 (en) * 1986-02-27 1987-09-30 Datawatt BV Method for transmitting data over mains lines
EP0238813A3 (en) * 1986-02-27 1989-05-10 Bbc Brown Boveri Ag Method for transmitting data over mains lines
EP0283299A2 (en) * 1987-03-20 1988-09-21 Nippon Telegraph And Telephone Corporation Radio receiver
EP0283299A3 (en) * 1987-03-20 1991-03-13 Nippon Telegraph And Telephone Corporation Radio receiver
GB2208985A (en) * 1987-08-24 1989-04-19 Kokusai Denshin Denwa Co Ltd A radio communication system
GB2208985B (en) * 1987-08-24 1991-07-31 Kokusai Denshin Denwa Co Ltd A radio communication system
GB2349544A (en) * 1989-05-30 2000-11-01 Secr Defence Covert communication system
GB2349544B (en) * 1989-05-30 2001-04-04 Secr Defence A wideband high frequency covert communications system
GB2259228A (en) * 1990-05-11 1993-03-03 Secr Defence A high frequency multichannel diversity differential phase shift (DPSK) communications system
WO1991018458A1 (en) * 1990-05-11 1991-11-28 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland A high frequency multichannel diversity differential phase shift (dpsk) communications system
AU637703B2 (en) * 1990-05-11 1993-06-03 Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland, The A high frequency multichannel diversity differential phase shift (dpsk) communications system
GB2259228B (en) * 1990-05-11 1994-06-01 Secr Defence A high frequency multichannel diversity differential phase shift (DPSK) communications system
WO1992004783A1 (en) * 1990-09-07 1992-03-19 Telefunken Systemtechnik Gmbh Method of determining the frequency deviation in digital communications transmissions
US5305347A (en) * 1990-09-07 1994-04-19 Deutsche Aerospace Ag Method of detecting the frequency deviation in digital communication transmissions
WO1993009618A1 (en) * 1991-10-31 1993-05-13 Massachusetts Institute Of Technology Communication system utilizing self-similar signals
FR2755460A1 (en) * 1996-11-07 1998-05-07 Kiekert Ag motor vehicle with a locking system centralizes a control device remote
US6694128B1 (en) 1998-08-18 2004-02-17 Parkervision, Inc. Frequency synthesizer using universal frequency translation technology
WO2000020712A1 (en) * 1998-10-05 2000-04-13 Lear Automotive Dearborn, Inc. Multiple channel remote keyless entry system
US6353735B1 (en) 1998-10-21 2002-03-05 Parkervision, Inc. MDG method for output signal generation
US6091940A (en) 1998-10-21 2000-07-18 Parkervision, Inc. Method and system for frequency up-conversion
US6061551A (en) 1998-10-21 2000-05-09 Parkervision, Inc. Method and system for down-converting electromagnetic signals
US6061555A (en) 1998-10-21 2000-05-09 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6266518B1 (en) 1998-10-21 2001-07-24 Parkervision, Inc. Method and system for down-converting electromagnetic signals by sampling and integrating over apertures
WO2000024120A1 (en) * 1998-10-21 2000-04-27 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6370371B1 (en) 1998-10-21 2002-04-09 Parkervision, Inc. Applications of universal frequency translation
US6421534B1 (en) 1998-10-21 2002-07-16 Parkervision, Inc. Integrated frequency translation and selectivity
US6542722B1 (en) 1998-10-21 2003-04-01 Parkervision, Inc. Method and system for frequency up-conversion with variety of transmitter configurations
US6560301B1 (en) 1998-10-21 2003-05-06 Parkervision, Inc. Integrated frequency translation and selectivity with a variety of filter embodiments
US6580902B1 (en) 1998-10-21 2003-06-17 Parkervision, Inc. Frequency translation using optimized switch structures
US6647250B1 (en) 1998-10-21 2003-11-11 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6687493B1 (en) 1998-10-21 2004-02-03 Parkervision, Inc. Method and circuit for down-converting a signal using a complementary FET structure for improved dynamic range
US6049706A (en) 1998-10-21 2000-04-11 Parkervision, Inc. Integrated frequency translation and selectivity
US8340618B2 (en) 1998-10-21 2012-12-25 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US8233855B2 (en) 1998-10-21 2012-07-31 Parkervision, Inc. Up-conversion based on gated information signal
US6798351B1 (en) 1998-10-21 2004-09-28 Parkervision, Inc. Automated meter reader applications of universal frequency translation
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
US7826817B2 (en) 1998-10-21 2010-11-02 Parker Vision, Inc. Applications of universal frequency translation
US7936022B2 (en) 1998-10-21 2011-05-03 Parkervision, Inc. Method and circuit for down-converting a signal
US8190116B2 (en) 1998-10-21 2012-05-29 Parker Vision, Inc. Methods and systems for down-converting a signal using a complementary transistor structure
US8190108B2 (en) 1998-10-21 2012-05-29 Parkervision, Inc. Method and system for frequency up-conversion
US8160534B2 (en) 1998-10-21 2012-04-17 Parkervision, Inc. Applications of universal frequency translation
US8019291B2 (en) 1998-10-21 2011-09-13 Parkervision, Inc. Method and system for frequency down-conversion and frequency up-conversion
US7937059B2 (en) 1998-10-21 2011-05-03 Parkervision, Inc. Converting an electromagnetic signal via sub-sampling
US7865177B2 (en) 1998-10-21 2011-01-04 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US7693502B2 (en) 1998-10-21 2010-04-06 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, transforms for same, and aperture relationships
US7697916B2 (en) 1998-10-21 2010-04-13 Parkervision, Inc. Applications of universal frequency translation
US6836650B2 (en) 1998-10-21 2004-12-28 Parkervision, Inc. Methods and systems for down-converting electromagnetic signals, and applications thereof
US6704558B1 (en) 1999-01-22 2004-03-09 Parkervision, Inc. Image-reject down-converter and embodiments thereof, such as the family radio service
US6704549B1 (en) 1999-03-03 2004-03-09 Parkvision, Inc. Multi-mode, multi-band communication system
US7724845B2 (en) 1999-04-16 2010-05-25 Parkervision, Inc. Method and system for down-converting and electromagnetic signal, and transforms for same
US7693230B2 (en) 1999-04-16 2010-04-06 Parkervision, Inc. Apparatus and method of differential IQ frequency up-conversion
US7894789B2 (en) 1999-04-16 2011-02-22 Parkervision, Inc. Down-conversion of an electromagnetic signal with feedback control
US7929638B2 (en) 1999-04-16 2011-04-19 Parkervision, Inc. Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US7773688B2 (en) 1999-04-16 2010-08-10 Parkervision, Inc. Method, system, and apparatus for balanced frequency up-conversion, including circuitry to directly couple the outputs of multiple transistors
US8594228B2 (en) 1999-04-16 2013-11-26 Parkervision, Inc. Apparatus and method of differential IQ frequency up-conversion
US8229023B2 (en) 1999-04-16 2012-07-24 Parkervision, Inc. Wireless local area network (WLAN) using universal frequency translation technology including multi-phase embodiments
US8224281B2 (en) 1999-04-16 2012-07-17 Parkervision, Inc. Down-conversion of an electromagnetic signal with feedback control
US8036304B2 (en) 1999-04-16 2011-10-11 Parkervision, Inc. Apparatus and method of differential IQ frequency up-conversion
US8077797B2 (en) 1999-04-16 2011-12-13 Parkervision, Inc. Method, system, and apparatus for balanced frequency up-conversion of a baseband signal
US8223898B2 (en) 1999-04-16 2012-07-17 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, and transforms for same
US8295406B1 (en) 1999-08-04 2012-10-23 Parkervision, Inc. Universal platform module for a plurality of communication protocols
US8295800B2 (en) 2000-04-14 2012-10-23 Parkervision, Inc. Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US7822401B2 (en) 2000-04-14 2010-10-26 Parkervision, Inc. Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US7991815B2 (en) 2000-11-14 2011-08-02 Parkervision, Inc. Methods, systems, and computer program products for parallel correlation and applications thereof
US8446994B2 (en) 2001-11-09 2013-05-21 Parkervision, Inc. Gain control in a communication channel
US7653158B2 (en) 2001-11-09 2010-01-26 Parkervision, Inc. Gain control in a communication channel
EP1551127A1 (en) * 2001-12-21 2005-07-06 Mitsubishi Denki Kabushiki Kaisha Radio communication system and transmitter for implementing frequency diversity
US7502357B2 (en) 2001-12-21 2009-03-10 Mitsubishi Denki Kabushiki Kaisha Radio communication system and transmitter
US8407061B2 (en) 2002-07-18 2013-03-26 Parkervision, Inc. Networking methods and systems
US8160196B2 (en) 2002-07-18 2012-04-17 Parkervision, Inc. Networking methods and systems
WO2006120319A1 (en) * 2005-05-10 2006-11-16 Societe Stantec Device and method for receiving binary data radio frequency
FR2885751A1 (en) * 2005-05-10 2006-11-17 Univ Joseph Fourier Etablissem Device and method for receiving radiofrequency binary data
US7519400B2 (en) 2005-05-27 2009-04-14 Dei Headquarters, Inc. Multi-modulation remote control communication system

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