Multiple access diplex doppler radar

• US 5,828,333 A
• Filed: 01/21/1997
• Issued: 10/27/1998
• Est. Priority Date: 01/21/1997
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Gustafson, Kenneth Alan, Timm, Beverly Jean, Collar, Stuart J., Richardson, David Livingstone, Hischke, Mark Douglas, Williams, Roger Brunner
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/774,931
• Time in Patent Office: 644 Days
• Field of Search: 342/70, 342/71, 342/72, 342/194, 342/196, 375/200
• US Class Current: 342/70
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• CPC Class Codes: G01S 13/348 using square or rectangular modulation, e.g. diplex radar for ranging over short distances
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/0232 Avoidance by frequency multiplex
• CPC Class Codes: G01S 7/0235 Avoidance by time multiplex

Abstract

A continuous wave diplex Doppler radar, comprising an oscillator generating a transmit signal having a spectrum at a carrier frequency, the oscillator having a frequency control input, and spread spectrum modulation means coupled to the frequency control input for spreading the spectrum of the transmit signal.

Claims

1. A continuous wave diplex Doppler radar, comprising:

an oscillator generating a carrier frequency modulated by an offset frequency to produce at least a diplex transmit signal, said oscillator having a frequency control input;

a spread spectrum modulator coupled to said frequency control input for spreading the spectrum of said transmit signal, said spectrum modulater further comprising;

a carrier frequency selector;

a summer having plural input nodes, one of said input nodes connected to said frequency selector;

a pseudo-random noise modulator connected to another of said input nodes of said summer;

a temperature sensor connected to a further input node of said summer for compensation of frequency changes caused by temperature; and

a digital to analog converter connected to an output of said summer and to said frequency control input.

2. A continuous wave diplex Doppler radar, comprising:

an oscillator generating a carrier frequency modulated by an offset frequency to produce at least a diplex transmit signal, said oscillator having a frequency control input, and wherein said oscillator has a frequency measurement output;

a spread spectrum modulator coupled to said frequency control input for spreading the spectrum of said transmit signal, said spread spectrum modulator further comprising;

a carrier frequency selector;

a phase lock loop connected to said carrier frequency selector and said frequency measurement output;

a summer having plural input nodes, one of said nodes connected to said phase lock loop;

a digital to analog converter connected to another of said input nodes; and

a pseudo-random noise modulator connected to said digital to analog converter.

3. A continuous wave diplex Doppler radar, comprising:

an oscillator generating a carrier frequency modulated by an offset frequency to produce at least a diplex transmit signal, said oscillator having a frequency control input, and wherein said oscillator generates said transmit signal during a time slot;

a spread spectrum modulator coupled to said frequency control input for spreading the spectrum of said transmit signal;

a contention detector for sensing interference between a return signal and one of a plurality of received signals and generating a transmit adjust signal adjusting one of;

(a) said carrier frequency and (b) said time slot; and

an interference controller for adjusting a respective one of;

(a) said carrier frequency and (b) said time slot in response to said transmit adjust signal.

4. The radar of claim 3 wherein said contention detector further comprises one of Aloha and a modified reservation Aloha.

5. The radar of claim 4 wherein said modified reservation Aloha comprises:

means for sensing frequency frames and time slots in one of said frequency frames;

means for selecting an unoccupied time slot in said frequency frame; and

means for transmitting in said unoccupied time slot.

6. The radar of claim 3 wherein said contention detector comprises:

means for sensing a received signal strength of a signal having a Doppler frequency shift beyond a range of interest;

means for comparing said signal strength to a sum of a noise signal for said channel and a present threshold value; and

means for declaring a contention exists whenever said signal strength exceeds said sum.

7. The radar of claim 6 wherein said contention detector comprises:

means for sensing a plurality of received signal strengths of signals having Doppler frequency shifts beyond a range of interest;

means for computing an average of said received signal strengths;

means for comparing said average to a sum of a noise signal for said channel and a present threshold value; and

means for declaring a contention exists whenever said signal strength exceeds said sum.

8. The radar of claim 3 wherein said interference controller comprises:

a frequency controller for changing said carrier frequency in predetermined steps to provide frequency division multiple access to a predetermined bandwidth.

9. The radar of claim 8 wherein said frequency controller comprises a computer processor.

10. The radar of claim 3 where said interference controller comprises:

a pulse modulator for changing said time slot of the transmit signal to provide time division multiple access in a predetermined time interval.

11. The radar of claim 10 wherein said pulse modulator comprises:

a clock;

a digital logic circuit connected to said clock for generating time slots; and

a transmit switch for turning on said transmit signal during a selected one of said time slots.

12. A continuous wave diplex Doppler radar, comprising:

an oscillator generating a carrier frequency modulated by an offset frequency to produce at least a diplex transmit signal, said oscillator having a frequency control input;

a spread spectrum modulator coupled to said frequency control input for spreading the spectrum of said transmit signal;

an amplitude sort for generating a power control signal based on received signal strengths; and

,

an RF attenuator for changing a transmit power in response to said power control signal whereby to provide adaptive gain in a predetermined range of transmit powers.

13. A continuous wave diplex Doppler radar, comprising:

an oscillator for generating a carrier frequency modulated by an offset frequency to produce at least a diplex transmit signal during a time slot;

a contention detector for sensing interference between a return signal and one of a plurality of received signals and generating a transmit adjust signal adjusting one of;

(a) said carrier frequency and (b) said time slot; and

an interference controller for adjusting a respective one of;

(a) said carrier frequency and (b) said time slot in response to said transmit adjust signal.

14. The radar of claim 13 wherein said interference controller comprises:

a frequency controller for changing the carrier frequency in predetermined steps to provide frequency division multiple access to a predetermined bandwidth.

15. The radar of claim 14 wherein said frequency controller comprises a computer processor.

16. The radar of claim 13 wherein said interference controller comprises:

a pulse modulator for changing the time slot of the transmit signal to provide time division multiple access to a predetermined time interval.

17. The radar of claim 16 wherein said pulse modulator comprises:

a clock;

a digital logic circuit connected to said clock for generating time slots; and

a transmit switch for turning on said transmit signal during a selected one of said time slots.

18. The radar of claim 13 further comprising:

an amplitude sort for generating a power control signal based on received signal strengths; and

an RF attenuator for changing a transmit power in response to said power control signal whereby to provide adaptive gain in a predetermined range of transmit powers.

19. A continuous wave diplex Doppler radar, comprising:

means for generating a continuous diplex waveform having a spectrum at a carrier frequency during a time slot;

means for detecting contention between a return of said continuous diplex waveform and a plurality of received signals and generating a transmit adjust signal adjusting one of;

(a) said carrier frequency and (b) said time slot; and

means for adjusting a respective one of;

(a) said carrier frequency and (b) said time slot in response to said transmit adjust signal.

20. The radar of claim 19 wherein said contention detecting means comprises:

a contention detector for sensing interference between a return signal and one of a plurality of received signals in a selected channel; and

a contention protocol for generating a waveform adjust signal in response to a sensed interference.

21. The radar of claim 19 wherein said means for adjusting comprises:

a pulse modulator for changing the time slot of the continuous wave diplex waveform in response to a detected contention whereby to provide time division multiple access in a predetermined time interval.

22. The radar of claim 19 wherein said means for adjusting comprises:

a frequency controller for changing the frequency of the continuous wave diplex waveform in response to a detected contention whereby to provide frequency division multiple access to a predetermined bandwidth.

23. The radar of claim 19 wherein said means for adjusting comprises:

an RF attenuator for changing the transmit power of the continuous wave diplex waveform in response to a detected contention whereby to provide adaptive gain in a predetermined range of transmit powers.

24. The radar of claim 19 wherein said generating means having a frequency control input, further comprising:

a spread spectrum modulation means coupled to said frequency control input for spreading the spectrum of said continuous wave diplex waveform.