Equalizer with decision feedback frequency tracking and bit decoding for spread spectrum communications

• US 20050100081A1
• Filed: 10/01/2003
• Published: 05/12/2005
• Est. Priority Date: 10/01/2003
• Status: Active Grant

• Current Assignee: Recon Dynamics LLC (Tricon Sales LLC)
• Original Assignee: Spectrum5, Inc.
• Inventors: Prestwich, Sy, Bevan, Scott, Ostermiller, Dirk, Dobson, W. Kurt
• Granted Patent: US 7,236,510 B2
• Time in Patent Office: Days
• US Class Current: 375/143
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04J 13/0077 Multicode, e.g. multiple codes assigned to one user
• CPC Class Codes: H04L 25/03114 non-adaptive, i.e. not adjustable, manually adjustable, or adjustable only during the reception of special signals

Abstract

A spread spectrum communications system adapted to receive simultaneous signals from multiple transmitters, separates frequency error and equalizes and decodes continuous streams of data sets from a plurality of matched filters with frequency correction and which sorts through data and successfully decodes data bits.

Claims

1. A spread spectrum communications system, comprising:

(A) a transmitter, said transmitter further comprising;

(1) a data source;

(2) a first mixer spreading data from said data source with a first pseudo noise source (PNA);

(3) a second mixer spreading data from said first mixer with a second pseudo noise source (PNB);

(4) an RF transmitter;

(b) a receiver, said receiver further comprising;

(1) an RF receiver;

(2) a plurality of frequency shifters, receiving a signal from said RF receiver;

(3) a plurality of PNB matched filters receiving signals from said RF receiver and said plurality of frequency shifters;

(4) a plurality of frequency shifters, receiving a signal from said plurality of PNB matched filters;

(5) a plurality of PNA matched filters receiving data from said plurality of PNB matched filters and said plurality of frequency shifters; and

(6) an equalizer/decoder receiving signals from said plurality of PNA matched filters.

2. A spread spectrum communications system, as recited in claim 1, wherein said PNA pseudo noise source provides a variable length code sequence.

3. A spread spectrum communications system, as recited in claim 1, wherein said PNB pseudo noise source provides a fixed length code sequence.

4. A spread spectrum communications system, as recited in claim 1, wherein said first mixer/multiplier spreads said data from said data source with a variable PN code PNA.

5. A spread spectrum communications system, as recited in claim 1, wherein said second mixer/multiplier spreads said data from said first mixer with a fixed length PN code PNB.

6. A spread spectrum communications system, as recited in claim 1, wherein said PNB matched filter further comprises a set of coefficients correlated to said PNB pseudo noise source.

7. A spread spectrum communications system, as recited in claim 1, wherein said plurality of frequency shifters are offset from each other by one or more degrees.

8. A spread spectrum communications system, as recited in claim 1, wherein said PNA matched filters are correlated to said PNA pseudo noise source.

9. A spread spectrum communications system, as recited in claim 1, wherein said PNB matched filters are correlated to said PNB pseudo noise source.

10. A spread spectrum communications system, as recited in claim 1, wherein said equalizer/decoder selects an advantageous signal from said received signals from said plurality of PNA matched filters.

11. A spread spectrum communications system, as recited in claim 1, wherein said equalizer/decoder performs the steps consisting of:

(A) initializing an update magnitude;

(B) forming a complex equalization point;

(C) scaling and rotating said equalization point into position;

(D) forming a decision boundary to decode bits;

(E) generating an output bit along with and error vector normalized to the origin; and

(F) updating angle and magnitude parameters for the next bit.