Pulse or digital communications – Receivers – Interference or noise reduction
Patent
1997-08-18
1999-12-28
Chin, Stephen
Pulse or digital communications
Receivers
Interference or noise reduction
375349, 455133, H04L 102, H04B 110, H04B 1702
Patent
active
060091304
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to communication system, and more particular to wideband transceivers for use in communication systems.
BACKGROUND OF THE INVENTION
Transmitters and receivers for communication systems generally are designed such that they are tuned to transmit and receive one of a multiplicity of signals having widely varying bandwidths and which may fall within a particular frequency range. It will be appreciated by those skilled in the art that these transmitters and receivers radiate or intercept, respectively, electromagnetic radiation within a desired frequency band. The electromagnetic radiation can be output from or input to the transmitter or receiver, respectively, by several types of devices including an antenna, a wave guide, a coaxial cable and an optical fiber.
These communication system transmitters and receivers may be capable of transmitting and receiving a multiplicity of signals; however, such transmitters and receivers generally utilize circuitry which is duplicated for each respective signal to be transmitted or received which has a different frequency or bandwidth. This circuitry duplication is not an optimal multi-channel communication unit design architecture, because of the added cost and complexity associated with building complete independent transmitters and/or receivers for each communication channel.
An alternative transmitter and receiver architecture is possible which would be capable of transmitting and receiving signals having a desired multi-channel wide bandwidth. This alternative transmitter and receiver may utilize a digitizer (e.g., an analog-to-digital converter) which operates at a sufficiently high sampling rate to ensure that the signal of the desired bandwidth can be digitized in accordance with the Nyquist criteria (e.g., digitizing at a sampling rate equal to at least twice the bandwidth to be digitized). Subsequently, the digitized signal preferably is pre- or post- processed using digital signal processing techniques to differentiate between the multiple channels within the digitized bandwidth.
With reference to FIG. 1, a prior wideband transceiver 100 is shown. Radio frequency (RF) signals are received at antenna 102 processed through RF converter 104 and digitized by analog-to-digital converter 106. The digitized signals are processed through a discrete fourier transform (DFT) 108, a channel processor 110 and from channel processors 110 to a cellular network and a public switched telephone network (PSTN). In a transmit mode, signals received from the cellular network are processed through channel processors 110, inverse discrete fourier transform (IDFT) 114 and digital-to-analog converter 116. Analog signals from digital-to-analog converter 116 are then up converted in RF up converter 118 and radiated from antenna 120.
A disadvantage of this alternative type of communication unit is that the digital processing portion of the communication unit must have a sufficiently high sampling rate to ensure that the Nyquist criteria is met for the maximum bandwidth of the received electromagnetic radiation which is equal to the sum of the individual communication channels which form the composite received electromagnetic radiation bandwidth. If the composite bandwidth signal is sufficiently wide, the digital processing portion of the communication unit is very costly and consumes a considerable amount of power. Additionally, the channels produced by a DFT or IDFT filtering technique must typically be adjacent to each other.
A need exists for a transmitter and a receiver, like the one which is described above, which is capable of transmitting and receiving a multiplicity of signals within corresponding channels with the same transmitter or receiver circuitry. However, this transmitter and receiver circuitry preferably should reduce communication unit design constraints associated with the above transceiver architecture. If such a transmitter and receiver architecture could be developed, then it would be ideally suited for cellula
REFERENCES:
patent: 5579341 (1996-11-01), Smith et al.
patent: 5621770 (1997-04-01), Zastera
patent: 5668836 (1997-09-01), Smith et al.
patent: 5854813 (1998-12-01), Rottinghaus et al.
Bailey Donald E.
Elder Robert C.
Kobrinetz Anthony
Laird Kevin M.
Lurey Daniel M.
Chin Stephen
Haas Kenneth A.
Motorola Inc.
Park Albert
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