1. A combiner circuit for use with a spread-spectrum rake receiver having a plurality of rake receiver fingers providing de-spread symbol data from respective corresponding signal components of a received spread-spectrum multi-path signal, the combiner circuit comprising:
a tap-delay line having a sequence of registers cyclically addressed according to a counter index; and
a summation circuit having inputs adapted to receive de-spread symbol data from a plurality of rake receiver fingers by way of gating circuitry controlled in accordance with correlation between said counter index and a respective predetermined de-skew index corresponding to each rake receiver finger;
wherein for each of plural index values of the counter index the summation circuit is operative to sum the data contents of the addressed tap-delay line register with the de-spread symbol data from each rake receiver finger having a matching de-skew index, the summation result being stored in said addressed tap-delay line register.
2. A combiner circuit as claimed in claim 1 wherein the number of registers in the tap-delay line sequence is equal to a delay spread of the received spread-spectrum multi-path signal in terms of de-spread symbol durations.
3. A combiner circuit as claimed in claim 1 wherein said gating circuitry includes, for each rake receiver finger, a de-skew index register stored with a de-skew index, a comparator for comparing said de-skew index and said counter index, and a pass gate controlled by an output of the comparator and having an input coupled to an output of the rake receiver finger and an output coupled to an input of the summation circuit.
4. A combiner circuit as claimed in claim 1 wherein the de-skew index corresponding to a particular rake receiver finger is determined on the basis of a path delay of the signal component for that rake receiver finger.
5. A combiner circuit as claimed in claim 1 wherein following each cycle of index values of the counter index the data contents of the tap-delay line are shifted by one register location in the sequence.
6. A rake receiver for spread-spectrum multi-path signals, comprising:
a plurality of rake receiver fingers for generating de-spread symbol data from respective corresponding signal components of a received spread-spectrum multi-path signal; and
a combiner including a sequence of registers cyclically addressed according to index values of a counter index, and a correlator coupled to the take receiver fingers and the register sequence for summing data from an addressed register in said sequence with selected de-spread symbol data from at least one of said rake receiver fingers in accordance with a predetermined correlation between said rake receiver fingers and said index values of said counter index.
7. A rake receiver as claimed in claim 6, wherein the correlator includes an adder having inputs coupled to receive de-spread symbol data from respective said rake receiver fingers by way of gates controlled in accordance with correlation between said counter index and a respective predetermined de-skew index corresponding to each rake receiver finger.
8. A rake receiver as claimed in claim 7 wherein for each index value of said counter index the adder is operative to sum the data contents of the addressed register in said register sequence with the de-spread symbol data from each rake receiver finger having a de-skew index matching the counter index, the summation result being stored in said addressed register.
9. A rake receiver as claimed in claim 8 wherein the number of registers in the register sequence is determined by a delay spread of the received multi-path signal in terns of de-spread symbol durations.
10. A rake receiver as claimed in claim 8 wherein, for each rake receiver finger, said gate includes a de-skew index register stored with a de-skew index, a comparator for comparing said de-skew index and said counter index, and a pass gate circuit controlled by an output of the comparator and having an input coupled to an output of the rake receiver finger and an output coupled to an input of the adder.
11. A rake receiver as claimed in claim 10 wherein the de-skew index corresponding to a particular rake receiver finger is determined on the basis of the path delay of the signal component for that rake receiver finger.
12. A rake receiver as claimed in claim 6 wherein following each cycle of counter indices the data contents of the register sequence are shifted by one register location in the sequence.
13. A method for combining de-spread symbol data generated by a plurality of rake receiver fingers from respective corresponding signal components of a received spread-spectrum multi-path signal, including:
establishing a sequence of registers;
determining a de-skew index for each rake receiver finger;
addressing the registers in the sequence according to a counter index cycle of counter index values; and
when the counter index value matches the de-skew index for a particular rake receiver finger, summing de-spread symbol data from that rake receiver finger with the contents of the addressed register in the sequence and storing the summation result in the addressed register.
14. A method as claimed in claim 13 wherein the number of registers in the register sequence is determined by a delay spread of the received multi-path signal in terms of de-spread symbol durations.
15. A method as claimed in claim 13 wherein the de-skew index corresponding to a particular rake receiver finger is determined on the basis of a path delay of the signal component for that rake receiver finger.
16. A method as claimed in claim 13 wherein following each cycle of counter index values the data contents of the register sequence are shifted by one register location in the sequence.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for processing OFDMA signals, the method comprising:
receiving at a filter, a calibration signal which is generated from conversion of a digital input signal comprising N samples to an analog signal, wherein said digital input signal comprises one (1) full scale sample and N-1 zero samples and N is an integer; and
in response to said receiving of said calibration signal, generating an output analog signal at said filter, wherein:
said output analog signal is converted to an output digital signal; and
a transfer function of said filter is determined via a Fast Fourier transformation of said output digital signal.
2. The method according to claim 1, wherein said OFDM system is compliant with one or more wireless standards comprising UMTS EUTRA (LTE), WiMAX(IEEE 802.16), and WLAN (IEEE 802.11).
3. The method according to claim 1, comprising measuring a transfer function of an in-phase branch filter andor a quadrature branch filter.
4. The method according to claim 1, wherein said filter is an in-phase branch filter or a quadrature branch filter.
5. The method according to claim 1, wherein said transfer function comprises a magnitude andor phase response.
6. The method according to claim 5, wherein said magnitude andor phase response mismatch is a function of frequency.
7. The method according to claim 1, wherein a number of said samples N is chosen arbitrarily.
8. The method according to claim 1, wherein said calibration signal approximates an impulse signal.
9. The method according to claim 1, comprising performing said Fast Fourier transform with an arbitrary number of coefficients.
10. The method according to claim 1, comprising sampling output of said filter in response to said receiving of said calibration signal.
11. A system for processing signals in an OFDM system, the system comprising:
one or more circuits comprising a filter, wherein said one or more circuits enable:
reception of a calibration signal at said filter, wherein said calibration signal is generated from conversion of a digital input signal comprising N samples to an analog signal, wherein said digital input signal comprises one (1) full scale sample and N-1 zero samples and N is an integer; and
generation of an output analog signal at said filter in response to said reception of said calibration signal, wherein:
said output analog signal is converted to an output digital signal; and
a transfer function of said filter is determined via a Fast Fourier transformation of said output digital signal.
12. The system according to claim 11, wherein said OFDM system is compliant with one or more wireless standards comprising UMTS EUTRA (LTE), WiMAX(IEEE 802.16), and WLAN (IEEE 802.11).
13. The system according to claim 11, wherein said one or more circuits measure a transfer function of an in-phase branch filter andor a quadrature branch filter.
14. The system according to claim 11, wherein said filter is an in-phase branch filter or a quadrature branch filter.
15. The system according to claim 11, wherein said transfer function comprises a magnitude andor phase response.
16. The system according to claim 15, wherein said magnitude andor phase response mismatch is a function of frequency.
17. The system according to claim 11, wherein a number of said samples N is chosen arbitrarily.
18. The system according to claim 11, wherein said calibration signal approximates an impulse signal.
19. The system according to claim 11, wherein said one or more circuits perform said Fast Fourier transform with an arbitrary number of coefficients.
20. The system according to claim 11, wherein said one or more circuits are operable to sample said output of said filter in response to said receiving of said calibration signal.