Receiver with AFC function for operating in soft handover
A receiver having Automatic Frequency Control (“AFC”) is described having at least one input signal terminal and an offset frequency estimation means for estimating each offset frequency of at least two predetermined input signals inputted at the same time at the input signal terminal. The access to the receiver of each input signal is respectively modulated and identified by a distinct code, and in addition an AFC means is included to perform automatic frequency control of a voltage control oscillator serving as a frequency reference of the receiver. The AFC means described in the present invention is operative to provide a unique compensation command defined as a function of a combination of at least two analytical terms, each term respectively depending on the estimated offset frequency of the corresponding input signal.
1. A receiver with Automatic Frequency Control (“AFC”), said receiver comprising:
at least one input signal terminal;
an offset frequency estimation means for estimating each offset frequency of at least two predetermined input signals inputted at the same time at the input signal terminal, access to the receiver of each input signal being respectively modulated and identified by a distinct code, wherein the offset frequency estimation means includes a plurality of frequency estimators; and
AFC means distinct from and coupled to the offset frequency estimation means to perform automatic frequency control of a voltage control oscillator serving as a frequency reference of the receiver, characterized in that the AFC means are able to provide a unique compensation command defined as a function of a combination of at least two analytical terms, wherein the AFC means includes a plurality of power estimators for estimating the power for each of the at least two predetermined input signals, and wherein each analytical term is respectively generated by multiplying the estimated offset frequency with the estimated power of the corresponding input signal.
2. The receiver of claim 1 , further comprising normalized power estimation means for estimating the power of each input signal for selecting a set of at least two input signals and normalizing each power estimation of the selected input signals over the total power of the selected signals.
3. The receiver of claim 1 , wherein the value of each analytical term is real.
4. The receiver of claim 3 , wherein the compensation command is a linear combination of real valued terms.
5. The receiver of claim 1 , wherein the value of each analytical term is unitary complex.
6. The receiver of claim 1 , wherein the command is the angular polar coordinate of a linear combination of complex valued term.
7. The receiver of claim 1 , wherein the input signal terminal is unique.
8. The receiver of claim 1 , wherein each signal is CDMA modulated.
9. The receiver of claim 1 , wherein a different frequency carrier is assigned to each signal.
10. The receiver of claim 1 , wherein the receiver is used during a soft handover procedure in a UMTS or 3G radio mobile system.
11. The receiver of claim 1 , wherein the offset frequency estimation means further comprises a plurality of despreaders coupled to the plurality of frequency estimators.
12. The receiver of claim 1 , wherein the offset frequency estimation means further comprises a multiplexer coupled to the plurality of frequency estimators.
13. The receiver of claim 1 , wherein the AFC means further comprises a frequency combiner coupled to the plurality of power estimators.
14. The receiver of claim 13 , wherein the frequency combiner comprises a normalizer.
15. A method to perform Automatic Frequency Control (“AFC”) on a receiver receiving at least two predetermined input signals inputted at the same time at an input signal terminal, the access to the receiver of each input signal being respectively modulated and identified by a distinct code, the said method comprising:
providing a receiver having an offset frequency estimator portion including a plurality of frequency estimators and an AFC portion including a plurality of power estimators, wherein the offset frequency estimator portion and the AFC portion are distinct from each other and coupled together;
estimating each power of the at least two predetermined input signals by the plurality of power estimators;
estimating each offset frequency of the at least two predetermined input signals by the plurality of frequency estimators; and
executing a compensation command to control a voltage oscillator serving as a frequency reference of the receiver, wherein the compensation command is unique and determined as a function of a combination of at least two analytical terms, and each analytical term is respectively generated by multiplying the estimated offset frequency with the estimated power of the corresponding input signal.
16. The method of claim 15 , further comprising:
estimating the power of each input signal;
selecting a set of at least two input signals; and
normalizing each power estimation of the selected input signals over the total power of the selected signals.
17. The method of claim 15 , wherein the offset frequency estimation portion further comprises a plurality of despreaders coupled to the plurality of frequency estimators.
18. The method of claim 15 , wherein the offset frequency estimation portion further comprises a multiplexer coupled to the plurality of frequency estimators.
19. The method of claim 15 , wherein the AFC portion further comprises a frequency combiner coupled to the plurality of power estimators.
20. The receiver of claim 19 , wherein the frequency combiner comprises a normalizer.