Combined satellite radio receiver
View Patent ↗A satellite digital radio receiver for receiving first and second radio services. The first and second radio services are broadcast in first and second respective different radio frequency bands. At least one radio programme is broadcast substantially simultaneously on both radio services and one of the frequency bands can produce interference in the other frequency band.
1. A satellite digital radio receiver for receiving first and second radio services, broadcast in first and second respective different radio frequency bands,
wherein at least one radio programme is broadcast substantially simultaneously on both radio services, and
wherein one of the frequency bands can produce interference in the other frequency band,
the receiver comprising:
a shared mixer circuit, configured to receive and down-convert signals in a bandwidth comprising both of the frequency bands to signals of lower frequency;
a first processing circuit, coupled to the output of the mixer circuit and configured to demodulate the first radio service;
a second processing circuit, coupled to the output of the mixer circuit and configured to demodulate the second radio service; and
a control circuit, connected to the first and second processing circuit and adapted to selectively couple the output of either the first or the second processing circuit to an output of the receiver,
wherein when interference in the first frequency band, caused by the second radio service, interferes with demodulation of the first radio service by the first processing circuit, the control circuit couples the output of the second processing circuit to the output, whereby the at least one radio programme can be received from the second radio service.
2. The receiver of claim 1 , wherein each frequency band comprises a first portion reserved for a signal broadcast by a satellite and a second portion reserved for a signal broadcast by a terrestrial repeater.
3. The receiver of claim 2 , wherein the second portion of the second frequency band, used by a terrestrial repeater of the second radio service, creates interference in the first portion of the first frequency band, used by a satellite of the first radio service.
4. The receiver of claim 1 , wherein the frequency bands are adjacent in frequency.
5. The receiver of claim 4 , wherein:
the first frequency band is about 2320 MHz to about 2332.5 MHz; and
the second frequency band is about 2332.5 MHz to about 2345 MHz.
6. The receiver of claim 1 , wherein the first radio service is the Sirius Satellite Radio service and the second radio service is the XM Satellite Radio service.
7. The receiver of claim 1 , wherein the shared mixer circuit is configured to down-convert the signals to an intermediate frequency, IF, signal.
8. The receiver of claim 7 , wherein each of the first and second processing circuits comprises:
a Surface Acoustic Wave, SAW, device, coupled to the output of the mixer circuit, for filtering the IF signal;
a down-conversion stage, coupled to the output of the SAW device; and
a poly-phase filter, coupled to the output of the down-conversion stage, for generating a filtered base-band signal.
9. The receiver of claim 8 , wherein each SAW device has a pass-band bandwidth of 12.5 MHz.
10. The receiver of claim 1 , wherein the shared mixer circuit is configured to down-convert the signals directly to the base-band.
11. The receiver of claim 1 , further comprising:
a decoder, selectively connectable to the output of the first processing circuit or the second processing circuit and operable to decode the at least one radio programme,
wherein when interference in the first frequency band, caused by the second radio service, interferes with demodulation of the first radio service by the first processing circuit, the control circuit connects the decoder to the output of the second processing circuit, whereby the at least one radio programme can be decoded from the second radio service.
12. The receiver of claim 1 , wherein each of the first and second processing circuits comprises a decoder, operable to decode the at least one radio programme.
13. The receiver of claim 1 , wherein the control circuit comprises a synchronisation circuit, for aligning the audio signal of the at least one radio programme broadcast on the first service with the audio signal of the at least one radio programme broadcast on the second service.
14. The receiver of claim 13 , wherein the control circuit comprises a memory for buffering one of the audio signals, in order to align it with the other audio signal.
15. A method of receiving a radio programme being broadcast substantially simultaneously on two satellite digital radio services, the digital radio services being broadcast in first and second respective different radio frequency bands,
wherein one of the frequency bands can produce interference in the other frequency band,
the method comprising:
mixing a received signal with a locally-generated carrier signal, to down-convert signals in a bandwidth comprising both of the frequency bands to signals of lower frequency;
demodulating the first radio service from the lower frequency signals;
demodulating the second radio service from the lower frequency signals; and
selectively providing the demodulated first radio service or the demodulated second radio service to an output,
wherein when interference in the first frequency band, caused by the second radio service, interferes with demodulation of the first radio service, the demodulated second radio service is coupled to the output, whereby the at least one radio programme can be received from the second radio service.