Rake receiver with individual finger compensator(s)
View Patent ↗Rake receivers in code division multiple access (CDMA) telecommunication comprise fingers ( 1,2,3 ) with each finger processing signal components for a particular transmission path to be able to better synchronize with a RF signal received via different paths, and a combiner ( 4 ) for combining the results originating from said fingers, and a compensator in the form of a controlled oscillator in a feedback loop. By locating a finger compensator ( 20 - 25 ) in a finger, said finger can handle complex situations, like Doppler shifts under high-speed conditions. Preferably, most or all fingers each comprise such a finger compensator, in which case said feedback loop can be avoided. Such a finger compensator can be hardware, software or a mixture of both when comprising a filter ( 21 ) plus an amplitude normalizer ( 22 ) between two arithmetical modules ( 20,25 ) for multiplying an input symbol signal with a conjugated previous input symbol signal and an output symbol signal with a previous output symbol signal.
1. Rake receiver for receiving information symbols, comprising at least two fingers and a combiner coupled to said fingers, wherein each of the at least two fingers comprises a finger compensator that compensates for frequency shift at the symbol level, wherein said finger compensator comprises:
a filter and an amplitude normalizes coupled serially configured to receive an input symbol signal and configured to generate an output symbol signal; and
a first arithmetical module configured to multiply said input symbol signal with a conjugated previous input symbol signal and a second arithmetical module configured to multiply said output symbol signal with a previous output symbol signal,
wherein at least one finger comprises:
a pilot channel correlator and a traffic channel correlator, with an output of said finger compensator being coupled to first inputs of a third and fourth arithmetical module, of which second inputs are coupled to outputs of said correlators; and
an averaging unit, of which an input is coupled to an output of said third arithmetical module and of which an output is coupled to a first input of a fifth arithmetical module, of which a second input is coupled to an output of said fourth arithmetical module.
2. Rake Receiver according to claim 1 , wherein all fingers each comprise a finger compensator, with all finger compensators together forming said compensator.
3. Rake receiver according to claim 2 , wherein said rake receiver comprises a mixer configured to convert intermediate frequency signals into baseband signals, which mixer comprises an oscillator input coupled to a stable oscillator.
4. The Rake receiver according to claim 1 , wherein said at least one finger further comprises a plurality of delay paths.
5. A system comprising at least one portable unit and at least one network unit capable of radio communication, with at least one unit comprising at least one rake receiver configured to receive information symbols, the at least one rake receiver comprising at least two fingers, and a combiner coupled to said fingers, wherein the at least two fingers each comprises a first arithmetical module configured to multiply an input symbol signal with a conjugated previous input symbol signal and a finger compensator that compensates for frequency shift at the symbol level, wherein the finger compensator is coupled to inputs of at least two arithmetical modules in a first set of arithmetical modules and at least one finger comprises an averaging unit coupled between at least two arithmetical modules in a second set of arithmetical modules, and wherein at least one arithmetical module is common to the first and second sets of arithmetical modules.
6. The system according to claim 5 , wherein said finger compensator comprises a filter and an amplitude normalizer coupled serially configured to receive the input symbol signal and configured to generate an output symbol signal.
7. The system according to claim 6 , wherein said finger compensator further comprises a second arithmetical module configured to multiply said output symbol signal with a previous output symbol signal.
8. The system according to claim 7 , wherein at least one finger comprises a pilot channel correlator and a traffic channel correlator, with an output of said finger compensator being coupled to first inputs of a third and fourth arithmetical module, of which second inputs are coupled to outputs of said correlators.
9. The system according to claim 8 , wherein said at least one finger comprises said averaging unit, of which an input is coupled to an output of said third arithmetical module and of which an output is coupled to a first input of a fifth arithmetical module, of which a second input is coupled to an output of said fourth arithmetical module.
10. The system according to claim 5 , wherein all fingers each comprise a finger compensator, with all finger compensators together forming said compensator.
11. The system according to claim 10 , wherein said rake receiver comprises a mixer configured to convert intermediate frequency signals into baseband signals, which mixer comprises an oscillator input coupled to a stable oscillator.
12. The system according to claim 5 , wherein said finger compensator further comprises a plurality of delay paths.
13. Portable unit comprising at least one rake receiver configured to receive information symbols, the at least one rake receiver comprising at least two fingers and a combiner coupled to said fingers, wherein the at least two fingers each comprises a pilot channel correlator, a traffic channel correlator, and a finger compensator that compensates for frequency shift at the symbol level, wherein the finger compensator is coupled to inputs of at least two arithmetical modules in a first set of arithmetical modules and at least one finger comprises an averaging unit coupled between at least two arithmetical modules in a second set of arithmetical modules, and wherein at least one arithmetical module is common to the first and second sets of arithmetical modules.
14. The unit according to claim 13 , wherein said finger compensator comprises a filter and an amplitude normalizer coupled serially configured to receive an input symbol signal and configured to generate an output symbol signal.
15. The unit according to claim 14 , wherein said finger compensator further comprises a first arithmetical module configured to multiply said input symbol signal with a conjugated previous input symbol signal and a second arithmetical module configured to multiply said output symbol signal with a previous output symbol signal.
16. The unit according to claim 15 , wherein with an output of said finger compensator being coupled to first inputs of a third and fourth arithmetical module, of which second inputs are coupled to outputs of said correlators.
17. The unit according to claim 16 , wherein said at least one finger comprises said averaging unit, of which an input is coupled to an output of said third arithmetical module and of which an output is coupled to a first input of a fifth arithmetical module, of which a second input is coupled to an output of said fourth arithmetical module.
18. The unit according to claim 13 , wherein all fingers each comprise a finger compensator, with all finger compensators together forming said compensator.
19. The unit according to claim 18 , wherein said rake receiver comprises a mixer configured to convert intermediate frequency signals into baseband signals, which mixer comprises an oscillator input coupled to a stable oscillator.
20. Network unit comprising at least one rake receiver configured to receive information symbols, the at least one rake receiver comprising at least two fingers and a combiner coupled to said fingers, wherein the at least two fingers each comprises a first arithmetical module configured to multiply an input symbol signal with a conjugated previous input symbol signal and a finger compensator that compensates for frequency shift at the symbol level, wherein the finger compensator is coupled to inputs of at least two arithmetical modules in a first set of arithmetical modules and at least one finger comprises an averaging unit coupled between at least two arithmetical modules in a second set of arithmetical modules, and wherein at least one arithmetical module is common to the first and second sets of arithmetical modules.