Adaptive antenna lobing on spread spectrum signals at negative S/N

• US 4,152,702 A
• Filed: 02/13/1978
• Issued: 05/01/1979
• Est. Priority Date: 02/13/1978
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Piesinger, Gregory H.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US05/877,133
• Time in Patent Office: 442 Days
• Field of Search: 343/100 SA, 343/100 CL, 343/100 LE, 343/854
• US Class Current: 342/367
• CPC Class Codes: H01Q 3/2617 Array of identical elements
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10

Abstract

In a communications system including a multiple antenna array with null steering apparatus, a desired signal and an identifier signal are transmitted, the desired signal including a first carrier modulated with bits of data delayed a predetermined period and with a random code and the identifier signal being substantially reduced in amplitude relative to the desired signal and including a second carrier in phase quadrature with the first carrier and modulated with the bits of data and with the random code, which transmitted signal is received in the null steering apparatus where the data from the identifier signal, which leads the data of the desired signal, is utilized to modulate the recovered first carrier and is adjusted in amplitude to cause the null steering apparatus to lobe on the desired signal, the remodulated carrier being utilized as a reference signal in the feedback circuits of the null steering apparatus.

Claims

1. A communications system comprising:

(a) a transmitter for transmitting a desired signal and an identifier signal, simultaneously, said transmitter including;

(1) oscillator means for providing a carrier with means coupled thereto for providing a first carrier and a second carrier in phase quadrature with the first carrier,

(2) random code generating means providing a predetermined random code,

(3) input means for receiving bits of data and providing a data output and including delay means for delaying the bits of data a predetermined amount and providing a delayed data output, and

(4) modulating means coupled to receive the first and second carriers, the random code, and the data and delayed data outputs, and providing the desired signal, including the first carrier modulated with the delayed data and the random code, and the identifier signal, including the second carrier modulated with the data and the random code and reduced in amplitude a predetermined amount; and

(b) a receiver having a multiple antenna array connected thereto for receiving the desired signal and the identifier signal from said transmitter, said receiver including;

(1) feedback means associated with each antenna in said array for adjusting the amplitude and phase of signals therein so that unwanted signals from the array are cancelled,

(2) random code generating means for providing an output signal substantially similar to the random code modulating the carrier of the desired signal,

(3) demodulation means coupled to said feedback means and to said random code generating means for providing output signals corresponding with the first carrier, the delayed bits of data from the desired signal, and the bits of data from the identifier signal,

(4) delay means coupled to said demodulator means for receiving the bits of data from the identifier signal and delaying the bits to correspond with the data bits of the transmitted desired signal,

(5) modulation means coupled to said random code generating means, said demodulation means and said delay means for providing an output signal which corresponds with the transmitted desired signal, and

(6) combining means coupled to said feedback means and said modulation means for utilizing the output signal from said modulation means to adjust a lobe in the antenna pattern in the direction of the desired signal.

2. A communications system as claimed in claim 1 wherein the demodulation means includes a first mixing device for removing the random code modulation from the desired signal and the identifier signal, filtering means for allowing the passage of only the desired signal and the identifier signal without random code modulation, a second mixing device for removing the data modulation from the carrier of the desired signal, and filtering means for allowing the passage of only the unmodulated carrier.

3. A communications system as claimed in claim 2 wherein the demodulation means further includes first amplification means connected to receive the unmodulated carrier and provide an output signal having an amplitude directly proportional to the amplitude of the signal applied to the demodulation means, second amplification means with automatic gain control connected to receive the unmodulated carrier and provide an output signal having an amplitude which is substantially preset in accordance with the maximum lobe available in the system, and means for combining the output signals from said first and second amplification means and supplying a carrier signal to the receiver modulation means.

4. In a multiple antenna array, null steering apparatus for reception of a desired signal wherein an identifier signal is transmitted with the desired signal, the desired signal including a first carrier modulated with bits of data delayed a predetermined period and with a random code, the identifier signal being substantially reduced in amplitude relative to the desired signal and including a second carrier in phase quadrature with the first carrier and modulated with the bits of data and with the random code, said null steering apparatus comprising:

(a) feedback means associated with each antenna in said array for adjusting the amplitude and phase of signals therein so that unwanted signals from the array are cancelled;

(b) random code generating means for providing an output signal substantially similar to the random code modulating the carrier of the desired signal;

(c) demodulation means coupled to said feedback means and to said random code generating means for providing output signals corresponding with the first carrier, the delayed bits of data from the desired signal, and the bits of data from the identifier signal;

(d) delay means coupled to said demodulator means for receiving the bits of data from the identifier signal and delaying the bits to correspond with the data bits of the transmitted desired signal;

(e) modulation means coupled to said random code generating means, said demodulation means and said delay means for providing an output signal which corresponds with the transmitted desired signal; and

(f) combining means coupled to said feedback means and said modulation means for utilizing the output signal from said modulation means to adjust a lobe in the antenna pattern in the direction of the desired signal.

5. In a multiple antenna array, null steering apparatus for reception of a desired signal with a negative signal-to-noise ratio wherein an identifier signal is transmitted with the desired signal, the desired signal including a first carrier modulated with bits of data delayed a predetermined period and with a random code, the identifier signal being substantially reduced in amplitude relative to the desired signal and including a second carrier in phase quadrature with the first carrier and modulated with the bits of data and with the random code, and null steering apparatus comprising:

(a) feedback means associated with each antenna in said array for adjusting the amplitude and phase of signals therein so that unwanted signals from the array are cancelled, said feedback means including a first path through which unwanted signals are free to pass and a second path;

(b) random code generating means for providing an output signal substantially similar to the random code modulating the carrier of the desired signal;

(c) first mixing and filtering means connected in said second feedback path and to said random code generating means for allowing the passage of only the desired and identifier signals and removing the random code modulation therefrom;

(d) quadrature demodulation means connected to said second feedback path for providing the delayed bits of data from the desired signal on a first output and the bits of data from the identifier signal on a second output;

(e) delay means coupled to the second output of said quadrature demodulation means for delaying the bits of data to correspond with the bits of data of the transmitted desired signal;

(f) second mixing and filtering means connected in said second feedback path and further connected to receive the bits of data for substantially removing the remaining modulation on the carrier of the desired signal to provide a substantially pure carrier signal;

(g) first linear amplifying means coupled to said second mixing and filtering means for amplifying the output carrier signal;

(h) second amplifying means including automatic gain control circuitry preadjusted substantially in accordance with the maximum lobe available in the system, said amplifying means being coupled to said second mixing and filtering means for amplifying the output carrier signal;

(i) means coupled to said first amplifying means and said second amplifying means for combining the carrier signals therefrom so as to provide an output signal tending to cause said feedback means to form a lobe in the antenna pattern; and

(j) modulating means coupled to receive the output signal from said combining means, the random code from said random code generating means and the delayed bits of data from the delay means for providing a reference signal substantially identical to the desired signal, and further coupled to said feedback means so that the lobe formed in the antenna pattern is directed in the direction of the desired signal.

6. Null steering apparatus as claimed in claim 5 wherein the means for combining the carrier signals includes a subtracting circuit providing an output carrier signal approximately equal to the difference in amplitude between the signals provided by the first and second amplifying means.

7. In conjunction with a multiple antenna array having attached thereto null steering apparatus for reception of a desired signal with a negative signal-to-noise ratio wherein an identifier signal is transmitted with the desired signal, the desired signal including a first carrier modulated with bits of data delayed a predetermined period and with a random code, the identifier signal being substantially reduced in amplitude relative to the desired signal and including a second carrier in phase quadrature with the first carrier and modulated with the bits of data and with the random code, a method of null steering the array comprising the steps of:

(a) removing the random code modulation from the first and second carriers and providing a random code output;

(b) demodulating the first and second carriers to obtain the bits of data from the first carrier at an output terminal, the bits of data from the second carrier delayed a predetermined amount, and the recovered first carrier;

(c) supplying the recovered first carrier through a linear amplifier to a combining device;

(d) supplying the recovered first carrier through an AGC amplifier to the combining device;

(e) remodulating the combined carrier output of the combining device with the delayed bits of data and with the random code output;

(f) utilizing the remodulated carrier to adjust the null steering apparatus to form a lobe in the antenna pattern in the direction of the desired signal; and

(g) adjusting the AGC amplifier and the combining device to maximize the lobe directed toward the desired signal.

8. In a communications system including a transmitter and a receiver with a multiple antenna array having null steering apparatus attached thereto with feedback circuitry for directing nulls in the array pattern in the direction of unwanted signals, a method of directing a lobe in the array pattern in the direction of a desired signal comprising the steps of:

(a) transmitting a desired signal including a first carrier modulated with bits of data delayed a predetermined period and with a random code and an identifier signal substantially reduced in amplitude relative to the desired signal and including a second carrier in phase quadrature with the first carrier and modulated with the bits of data and with the random code;

(b) receiving the transmitted signals in the receiver;

(c) removing the random code modulation from the first and second carrier and providing a random code output;

(d) demodulating the first and second carriers to obtain the bits of data from the first carrier at an output terminal, the bits of data from the second carrier delayed a predetermined amount, and the recovered first carrier;

(e) supplying the recovered first carrier through a linear amplifier to a combining device;

(f) supplying the recovered first carrier through an AGC amplifier to the combining device;

(g) remodulating the combined carrier output of the combining device with the delayed bits of data and with the random code output;

(h) utilizing the remodulated carrier to adjust the null steering apparatus to form a lobe in the array pattern in the direction of the desired signal; and

(i) adjusting the AGC amplifier and the combining device to maximize the lobe directed toward the desired signal.