Sample rate adaption in signal processing
View Patent ↗The mixed signal chip ( 10 ) takes analogue signals received at, for example, a mobile telephone and converts them to the digital domain for subsequent processing. Through use of sample rate adaption and adjustable filtering, the mixed signal chip can work on radio signals formatted according to different standards.
1. Apparatus for preparing a signal, which is one of the UMTS and GSM signal, and has been received at a wireless communications device, to be processed by a receiver which will attempt to recover information conveyed by the signal, the apparatus comprising:
a filter to filter the signal in a digital form having samples appearing at a sample rate; and
an adjuster to adjust the sample rate,
wherein the filter filters the signal in both a first manner which is required when the receiver is a UMTS receiver and a second manner which is required when the receiver is a GSM receiver,
wherein the adjuster performs adjustments to the sample rate when the receiver is the GSM receiver and the adjustments comprise altering the sample rate before the signal is filtered to permit the filter to perform filtering in the second manner and altering, using a combination of an interpolator followed by a decimator, the sample rate after the signal has been filtered to provide the signal with a sample rate required by the GSM receiver, whereas the filter performs filtering in the first manner without the adjustments to the sample rate when the receiver is the UMTS receiver,
wherein the filter comprises an FIR filter with adjustable tap coefficients which can be adjusted to allow the filter to perform filtering in the first manner and in the second manner.
2. Apparatus according to claim 1 , wherein the adjuster is adapted to change to said sample rate by a fractional factor.
3. Apparatus according to claim 1 , wherein the filter is adapted to correct errors introduced by the adjuster.
4. Apparatus according to claim 1 , wherein the UMTS receiver comprises a rake receiver for operating on the signal and the GSM receiver comprises an equaliser for operating on the signal.
5. A participant for a wireless communications network, the participant comprising the apparatus of claim 1 .
6. A method of preparing a signal, which is one of the UMTS signal and GSM signal, and has been received at a wireless-communications device, to be processed by a receiver which will attempt to recover information conveyed by the signal, the method comprising:
filtering the signal in a digital form having samples appearing at a sample rate using a filter to filter the signal in both a first manner when the receiver is a UMTS receiver and a second manner when the receiver is a GSM receiver and making sample rate adjustments to the signal when filtering is to be performed in the second manner but no sample rate adjustments to the signal when filtering is to be performed in the first manner,
wherein said adjustments comprise adjusting the sample rate before the signal is filtered to permit the filter to perform filtering in the second manner and adjusting the sample rate after the signal has been filtered to provide the signal with a sample rate required by the GSM receiver,
wherein adjusting the sample rate after the signal has been filtered comprises adding samples using an interpolator and then removing samples using a decimator, and
wherein the filter comprises an FIR filter with adjustable tap coefficients which can be adjusted to allow the filter to perform filtering in the first manner and in the second manner.
7. A method according to claim 6 , wherein said adjustments are arranged to change to said sample rate by a fractional factor.
8. A method according to claim 6 , wherein the UMTS receiver comprises a rake receiver for operating on the signal and the GSM receiver comprises an equaliser for operating on the signal.
9. A mixed signal section for a participant for a wireless communications network, the mixed signal section comprising the apparatus of claim 1 .
10. In a wireless receiver an apparatus for processing a signal which is one of the UMTS signal and GSM signal in form of digital samples appearing at a sample rate, the apparatus comprising:
a decimator for bypassing the signal when the wireless receiver is a UMTS receiver and altering the sample rate of the signal when the wireless receiver is a GSM receiver;
a filter for filtering the bypassed signal when the wireless receiver is the UMTS receiver and filtering the decimated signal when the wireless receiver is the GSM receiver; and
an adaptor for altering the sample rate of the filtered signal when the wireless receiver is the GSM receiver, the adaptor adjusting the sample rate of the signal before the filter and adjusting the sample rate of the filtered signal after the filter,
wherein the adaptor for adjusting the sample rate of the filtered signal after the filter comprises a combination of an interpolator followed by a decimator, and
wherein the filter comprises an FIR filter with adjustable tap coefficients which can be adjusted to allow the filter to perform filtering in the first manner and in the second manner.
11. The apparatus according to claim 10 , wherein the adaptor comprises:
an interpolation unit for increasing the sample rate of the filtered signal; and
another decimator for decreasing the sample rate of the filtered signal.
12. The apparatus according to claim 10 , wherein the filter is adapted to correct errors introduced by the decimator.
13. The apparatus according to claim 10 , further comprising a switch electrically connected with the decimator for selecting the signal received from one of the UMTS receiver and the GSM receiver.
14. The apparatus according to claim 13 , further comprising another switch electrically connected with the decimator for bypassing the signal.
15. Apparatus according to claim 10 , wherein the UMTS receiver comprises a rake receiver for operating on the signal and the GSM receiver comprises an equaliser for operating on the signal.
16. In a wireless receiver a method for processing a signal which is one of the UMTS signal and GSM signal in form of digital samples appearing at a sample rate, the method comprising:
receiving the signal which is one of the UMTS signal and GSM signal;
bypassing the received signal when the wireless receiver is a UMTS receiver and altering the sample rate of the received signal when the wireless receiver is a GSM receiver;
filtering the bypassed signal when the wireless receiver is the UMTS receiver and filtering a resulting decimated signal when the wireless receiver is the GSM receiver; and
altering the sample rate of both the signal before filtering and the filtered signal after filtering when the wireless receiver is the GSM receiver,
wherein altering the sample rate after filtering comprises adding samples using an interpolator and then removing samples using a decimator.
17. A method according to claim 16 , wherein the UMTS receiver comprises a rake receiver for operating on the signal and the GSM receiver comprises an equaliser for operating on the signal.
18. A mixed signal section for a participant for a wireless communications network, the mixed signal section comprising the apparatus of claim 10 .
19. Apparatus according to claim 1 , wherein the filter is programmed to compensate for frequency distortions introduced by a receiver of which the apparatus is a part.
20. The method of claim 6 , further comprising programming the filter to compensate for frequency distortions introduced by a receiver within the wireless-communications device.
21. The apparatus according to claim 10 , wherein the filter is programmed to compensate for frequency distortions introduced by a receiver of which the apparatus is a part.