Noise shaping technique for spread spectrum communications

• US 6,654,407 B2
• Filed: 12/21/2001
• Issued: 11/25/2003
• Est. Priority Date: 11/02/1993
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Moore, Timothy F. III
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US10/029,707
• Publication Number:
  US 20020048314A1
• Time in Patent Office: 704 Days
• Field of Search: 375/219, 375/265, 375/220, 375/222, 375/259, 375/130, 375/141, 375/133, 375/137, 455/39, 455/73, 455/42, 455/77, 370/320, 370/335, 370/342, 370/441
• US Class Current: 375/141
• CPC Class Codes: H04B 1/68 for wholly or partially suppressing the carrier or one side band
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04L 27/02 Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation H04L27/32 takes precedence

Abstract

A spread spectrum noise shaper uses a modulation technique to achieve a greater signal-to-noise or signal-to-interference ratio (SNR or SIR). The technique doubles the system SIR, in principle. This doubling yields a doubling in system capacity. SNR is increased by receiving the spread spectrum signal in the presence of less noise near the edge of the spread spectrum bandwidth. The technique requires only small additions to a conventional spread spectrum system, in the form of an extra modulator at the transmitter, and an extra demodulator and filter at the receiver.

Claims

1. A transmitter for transmitting a spread spectrum code division multiple access (CDMA) communication signal over a carrier frequency, the signal comprising a data sequence convolved with a pseudo-noise sequence, the data sequence having a chip rate, the transmitter comprising:

a frequency translator for translating the signal to a portion of the signal bandwidth having less than the greatest magnitude of noise;

a spread spectrum encoder for encoding the translated signal into a spread signal;

an antenna from which the spread signal is transmitted; and

a power amplifier for driving the antenna.

2. The transmitter of claim 1, wherein the frequency translator comprises a single sideband modulator.

3. The transmitter of claim 1, wherein the encoder comprises a mixer for mixing the translated signal with the pseudo-noise sequence.

4. The transmitter of claim 1, wherein the translator is responsive to a reference signal having a frequency at the chip rate, further comprising:

a low-pass filter having a cutoff frequency corresponding to the chip rate;

a miser for up-converting said spread spectrum data signal at the carrier frequency; and

a band-pass filter with a bandwidth corresponding to twice the chip rate for filtering the signal prior to transmission.

5. The transmitter of claim 4, wherein the band-pass filter is a helical resonator.

6. The transmitter of claim 1, wherein the spread spectrum signal is bimodal.

7. A receiver for receiving a spread spectrum code division multiple access (CDMA) communication signal with a data rate on a carrier frequency, the signal encoded with a pseudo-noise sequence, the receiver comprising:

an antenna for receiving a single sideband modulated form of the spread spectrum signal;

a mixer for down-converting the spread spectrum data signal at the carrier frequency;

a spread spectrum decoder for decoding the dawn-converted signal into a decoded signal; and

a single sideband demodulator for translating the decoded signal to a replica of the spread-spectrum signal.

8. The receiver of claim 7 wherein the decoder comprises a mixer for despreading the received spread spectrum signal with the pseudo-noise sequence.

9. The receiver of claim 7 further comprising:

a mixer for down-converting the spread spectrum data signal at the carrier frequency prior to decoding;

a band-pass filter having a bandwidth corresponding to the data rate;

a low-pass filter with a cutoff frequency corresponding to the data rate.

10. A transmitter for transmitting a spread spectrum code division multiple access (CDMA) communication signal over a carrier frequency, the signal comprising noise and a data sequence convolved with a pseudo-noise sequence, the pseudo-noise sequence having a chip rate, the transmitter comprising:

a single sideband modulator for shifting the signal responsive to a reference signal to a portion of the signal bandwidth having less than the greatest magnitude of noise;

a spread spectrum encoder for encoding the translated signal into a spread signal;

an antenna from which the spread signal is transmitted; and

a power amplifier for driving the antenna.

11. The transmitter of claim 10 whereby the reference signal has a frequency that is about equal to the chip rate.