Receiver with offset compensation
Receiver for receiving a received signal with a carrier frequency loop ( 18 ) which generates a carrier frequency deviation detection signal (TF) for detecting a carrier frequency of the received signal in a first carrier frequency capture range; a carrier phase loop ( 32 ) which generates a carrier phase deviation detection signal (TP) for detecting a carrier phase of the received signal, and settles when the carrier frequency deviation detection signal (TF) is within a second carrier frequency capture range; and with an offset control circuit ( 29 ) which changes the carrier frequency deviation detection signal (TF) and/or changes the second carrier frequency capture range by means of an offset control signal until a carrier phase lock detection circuit ( 21 ) indicates to the offset control circuit that the carrier phase offset of the received signal is less than an adjustable threshold value.
1. Receiver for receiving a received signal with:
a) a carrier frequency loop which generates a carrier frequency deviation detection signal for detecting a carrier frequency of the received signal in a first carrier frequency capture range;
b) a carrier phase loop which generates a carrier phase deviation detection signal for detecting a carrier phase of the received signal in a second carrier frequency capture range, and with
c) an offset control circuit which changes the carrier frequency deviation detection signal and/or changes the second carrier frequency capture range by means of an offset control signal until a carrier phase lock detection circuit indicates to the offset control circuit that a carrier phase offset of the received signal is less than an adjustable threshold value.
2. Receiver according to claim 1 , wherein the second carrier frequency capture range is narrower than the first carrier frequency capture range.
3. Receiver according to claim 1 , wherein the receiver is a QAM receiver.
4. Receiver according to claim 1 , wherein the carrier frequency loop has a carrier frequency detector, a first digital loop filter, a first controlled oscillator and a first mixing stage.
5. Receiver according to claim 1 , wherein the carrier phase loop has a carrier phase detector, a second digital loop filter, a second controlled oscillator and a second mixing stage.
6. Receiver according to claim 1 , wherein a first matched filter for the in-phase signal component of a received QAM signal and a second matched filter for the quadrature signal component of the received QAM signal are provided between a first mixing stage of the carrier frequency loop and a second mixing stage of the carrier phase loop.
7. Receiver according to claim 6 , wherein the second mixing stage is followed by the carrier phase lock detection circuit.
8. Receiver according to claim 5 , wherein the offset control circuit generates a carrier phase offset signal which is added to the carrier phase deviation detection signal, filtered by the second digital loop filter of the carrier phase loop, by an adder for shifting the frequency of the second carrier frequency capture range of the carrier phase loop.
9. Receiver according to claim 1 , wherein the offset control circuit generates a carrier frequency offset signal which is added to the carrier frequency deviation detection signal, generated by the carrier frequency loop, by an adder for compensating for a frequency offset of the received signal.