Pulse or digital communications – Repeaters – Testing
Patent
1989-05-24
1990-08-07
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
375 99, 455256, H04L 2706
Patent
active
049474090
ABSTRACT:
Apparatus for correcting the frequency in a coherent receiver associated with a radio communication installation, e.g. a mobile telephone installation for transmitting digital information in time-division multiplex. The receiver includes a controllable local oscillator (7) for generating a mixing signal for converting the frequency of a received signal, and unit (4,8,9) for calculating a frequency error and generating a control signal (f") to the oscillator (7). Each new value of the control signal (f") is dependent on a previous value and on the calculated frequency error, and is utilized for correcting the frequency of said mixing signal. At least the major part of a frequency error in the receiver is thus eliminated. A possibly remaining part of a required frequency correction is carried out by a frequency change in the baseband. This is achieved with the aid of a unit (11) included in the receiver, and adapted to perform regularly repeated phase shifts of a signal (I,Q) in the baseband by a value (V.sub.r), which is changed for each received modulation symbol, e.g. a data bit, and which is responsive to said remaining part of the required frequency correction.
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Marsan et al., "Time-Domain Simulation of a Telecommunication Distress System"; Proceedings of an International Symposium by University of Bologna; Bologna, Italy, Sep. 19-21, ESA Nov. 1-16, 1979.
Hedberg Bo G.
Raith Alex K.
Stiernvall Jan-Erik
Chin Stephen
Safourek Benedict V.
Telefonaktiebolaget L M Ericsson
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