Efficient polyphase quadrature digital tuner

• US 6,049,573 A
• Filed: 12/11/1997
• Issued: 04/11/2000
• Est. Priority Date: 12/11/1997
• Status: Expired due to Term

• Current Assignee: Ctrc Research Foundation, Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Song, William S.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US08/989,219
• Time in Patent Office: 852 Days
• Field of Search: 375/316, 375/235, 375/340, 375/350, 375/261, 375/349, 348/398, 329/304, 329/306, 329/345, 329/346
• US Class Current: 375/316
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03H 17/0275 comprising non-recursive filters

Abstract

A polyphase quadrature digital tuner system which converts input signals to baseband inphase and quadrature signal components. The system includes a signal receiver which receives the input signals having a frequency centered around a predetermined carrier frequency. A signal processor continuously samples the input signals and multiplies selected portions of the input signals by a value of 1 or -1 to produce discrete sequences of N input samples, where N is an integer. An inphase signal channel includes a first set of N filters in a first filter stage each having respective filter coefficients, the first set of filters arranged to receive the discrete sequences, and a first signal summer which sums the outputs of the first set of N filters to produce the inphase signal component. A quadrature signal channel includes a second set of N filters in the first filter stage each having respective filter coefficients, the second set of filters arranged to receive the discrete sequences, and a second signal summer which sums the outputs of the second set of N filters to produce the quadrature signal component. The input samples are provided to the inphase and quadrature signal channels so that each filter of both channels receives one input sample of each sequence.

Claims

1. A polyphase quadrature digital tuner system which converts input signals to baseband inphase and quadrature signal components, said system comprising:

a signal receiver which receives said input signals having a frequency centered around a predetermined carrier frequency;

a signal processor which continuously samples said input signals and multiplies selected portions of said input signals by a value of 1 or -1 to produce discrete sequences of N input samples, where N is an integer;

an inphase signal channel including a first set of N filters in a first filter stage each having respective filter coefficients, said first set of filters arranged to receive said discrete sequences, and a first signal summer which sums the outputs of said first set of N filters to produce said inphase signal component;

a quadrature signal channel including a second set of N filters in said first filter stage each having respective filter coefficients, said second set of filters arranged to receive said discrete sequences, and a second signal summer which sums the outputs of said second set of N filters to produce said quadrature signal component; and

means for providing said input samples to said inphase and quadrature signal channels so that each filter of both channels receives one input sample of each sequence.

2. The system of claim 1, wherein said signal processor comprises an analog-to-digital converter which generates digital input samples.

3. The system of claim 1, wherein said signal processor continuously samples said input signal at a sampling frequency of 2N/L of said carrier frequency, where L is an integer.

4. The system of claim 1, wherein each of said filters comprise M taps, where M is an integer.

5. The system of claim 1, wherein said providing means operates to simultaneously switch said input samples of each sequence between each filter in said inphase and quadrature signal channels.

6. The system of claim 1 further comprising at least a second filter stage having at least one filter in each channel which performs filtering and decimation of the outputs of said first and second signal summers.

7. The system of claim 6 further comprising a plurality of successive filter stages each providing at least one filter in each channel which performs filtering and decimation of the outputs of previous filter stages.

8. The system of claim 1 further comprising:

a third set of P filters in a second filter stage of said inphase signal channel, said third set of P filters arranged to receive said discrete sequences from said first signal summer, and a third signal summer which sums the outputs of said third set of P filters to produce said inphase signal component;

a fourth set of P filters in said second filter stage of said quadrature signal channel, said fourth set of P filters arranged to receive said discrete sequences from said second signal summer, and a fourth signal summer which sums the outputs of said fourth set of P filters to produce said quadrature signal component; and

means for providing said discrete sequences from said first and second signal summers to said third and fourth set of P filters so that each filter of both channels receives one input sample of each sequence.

9. The system of claim 8 further comprising a plurality of successive filter stages each providing sets of R filters in each channel which performs filtering and decimation of the outputs previous filter stages.

10. The system of claim 1, wherein said signal processor continuously samples said input signals and alternately multiplies selected portions of said input signals by a value of 1 and -1 to produce discrete sequences of N input samples.

11. The system of claim 1, wherein the coefficients of each filter in each filter stage is multiplied by a value of 1 or -1 for each new sample provided to the filters.

12. The system of claim 1, wherein the partial products of coefficients and input values are multiplied by a value of 1 or -1 prior to further filter processing.

13. The system of claim 1, wherein said filters comprise FIR filters.

14. The system of claim 1, wherein said filters comprise IIR filters.

15. A method of polyphase quadrature tuning by converting input signals to baseband inphase and quadrature signal components, said method comprising:

receiving said input signal having a frequency centered around a predetermined carrier frequency;

continuously sampling said input signals;

multiplying selected portions of said input signals by a value of 1 or -1 to produce discrete sequences of N input samples, where N is an integer;

applying said discrete sequences to an inphase signal channel including a first set of N filters each having respective filter coefficients, said first set of filters arranged to receive said discrete sequences;

summing the outputs of said first set of N filters to produce said inphase signal component;

applying said discrete sequences to a quadrature signal channel including a second set of N filters each having respective filter coefficients, said second set of filters arranged to receive said discrete sequences;

summing the outputs of said second set of N filters to produce said quadrature signal component; and

simultaneously providing said input samples of each sequence between each filter of said inphase and quadrature signal channels so that each filter receives one input sample of each sequence.

16. The method of claim 15 further comprising generating digital input samples.

17. The method of claim 15 further comprising continuously samples said input signal at a sampling frequency of 2N/L of said carrier frequency, where L is an integer.

18. The method of claim 15 further comprising simultaneously switch said input samples of each sequence between each filter in said inphase and quadrature signal channels.

19. The method of claim 15 further comprising filtering and decimation of the outputs of said first and second signal summers with at least a second filter stage having at least one filter in each channel.

20. The method of claim 19 further comprising filtering and decimation of the outputs of previous filter stages with a plurality of successive filter stages each providing at least one filter in each channel.

21. The method of claim 15 further comprising:

receiving said discrete sequences from said first signal summer with a third set of P filters in a second filter stage of said inphase signal channel, and summing the outputs of said third set of P filters to produce said inphase signal component;

receiving said discrete sequences from said second signal summer with a fourth set of P filters in said second filter stage of said quadrature signal channel, and summing the outputs of said fourth set of P filters to produce said quadrature signal component; and

providing the summed discrete sequences to said third and fourth set of P filters so that each filter of both channels receives one input sample of each sequence.

22. The method of claim 21 further comprising filtering and decimation of the outputs previous filter stages with a plurality of successive filter stages each providing sets of R filters in each channel.

23. The method of claim 15 further comprising continuously samples said input signals and alternately multiplying selected portions of said input signals by a value of 1 and -1 to produce discrete sequences of N input samples.

24. The method of claim 15, wherein the coefficients of each filter in each filter stage is alternately multiplied by a value of 1 and -1 for each new sample provided to the filters.

25. The method of claim 15, wherein the partial products of coefficients and input values are multiplied by a value of 1 or -1 prior to further filter processing.

26. A method of polyphase quadrature tuning by converting input signals to baseband inphase and quadrature signal components, said method comprising:

receiving said input signal having a frequency centered around a predetermined carrier frequency;

continuously sampling said input signals;

multiplying selected portions of said input signals by a value of 1 or -1 to produce discrete sequences of N input samples, where N is an integer;

applying said discrete sequences to an inphase filtering sequence including a first set of N filters each having respective filter coefficients, said first set of filters arranged to receive said discrete sequences;

summing the outputs of said first set of N filters to produce said inphase signal component;

applying said discrete sequences to a quadrature filtering sequence including a second set of N filters each having respective filter coefficients, said second set of filters arranged to receive said discrete sequences;

summing the outputs of said second set of N filters to produce said quadrature signal component; and

simultaneously providing said input samples of each sequence between each filter of said inphase and quadrature filtering sequence so that each filter receives one input sample of each sequence.