Abstract: A digital radio receiver adapted to receive radio signals modulated using continuous phase frequency shift keying, CPFSK. The receiver comprises means for receiving a radio signal (2), a correlator (8) arranged to estimate a frequency offset between the carrier frequency of the received radio signal and a nominal carrier frequency, means for correcting said frequency offset (4) and outputting a frequency-corrected radio signal (6), and a matched filter bank, MFB, which comprises a plurality of filters (20,22), each of which corresponds to a different bit pattern, for determining a bit sequence (36) from the frequency-corrected radio signal (6).

Abstract: Radio transmission apparatus is configured to transmit binary message data in variable-length radio data packets. Each data packet comprises (i) a variable-length data unit and (ii) an error-detecting code for the data unit. The length of the error-detecting code varies between data packets according to a property of each data packet, such as the length of the data unit of the data packet, or a field in the data packet that specifies the length of the error-detecting code.

Abstract: A digital radio receiver comprises: a first section arranged to receive an analog radio signal and to generate therefrom digital intermediate frequency I and Q channel samples, a second section arranged to convert said I and Q channel samples to a lower, baseband frequency, said second section comprising: a first coordinate rotation digital computer module arranged to perform a complex rotation of the I channel samples; a second coordinate rotation digital computer module arranged to perform a complex rotation of the Q channel samples; a phase accumulator arranged to provide an output signal representing a complex rotation to be applied to each of the I and Q channel samples, wherein the second section is arranged such that the phase accumulator output signal is modified by a phase offset signal prior to being supplied to one of the first and second coordinate rotation digital computers.

Abstract: A digital radio receiver comprises: a first section arranged to receive an analogue radio signal and to generate therefrom digital intermediate frequency I and Q channel samples, a second section arranged to convert said I and Q channel samples to a lower, baseband frequency, said second section comprising: a first coordinate rotation digital computer module arranged to perform a complex rotation of the I channel samples; a second coordinate rotation digital computer module arranged to perform a complex rotation of the Q channel samples; a phase accumulator arranged to provide an output signal representing a complex rotation to be applied to each of the I and Q channel samples, wherein the second section is arranged such that the phase accumulator output signal is modified by a phase offset signal prior to being supplied to one of the first and second coordinate rotation digital computers.