Heterodyned double sideband diplex radar

• US 6,236,352 B1
• Filed: 10/28/1999
• Issued: 05/22/2001
• Est. Priority Date: 10/28/1999
• Status: Expired due to Term

• Current Assignee: Bendix Commercial Vehicle Systems LLC (Estate of Heinz Hermann Thiele)
• Original Assignee: Eaton Vorad Technologies, LLC
• Inventors: Walmsley, Prescott A.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/428,694
• Time in Patent Office: 572 Days
• Field of Search: 342/21, 342/118, 342/127, 342/128, 342/129, 342/130, 342/131, 342/132, 342/134, 342/135
• US Class Current: 342/118
• 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

Abstract

A heterodyned double side band diplex radar system determines the range of targets as a function of the amplitude variation of reflected target Doppler signals. The present invention includes a real radar system that accurately determines the range of fading targets and the magnitude of the velocity of the targets. The present invention also includes a complex radar system that determines the relative velocity of targets in addition to the range of targets. In either embodiment, the transmitted signal may be modulated with a pseudo-random number (“PN”) sequence to attenuate or decorrelate signals reflected from targets beyond some maximum range. The modulation of the pseudo-random sequence may also attenuate or decorrelate signals reflected from targets closer than some minimum range. The present invention also includes a real radar system having BPSK modulation with PN coding. The selection of BPSK modulation enables or facilitates the implementation of a portion of the system in digital form. In particular, the generation of the IF signals needed to modulate and demodulate the transmitted and received signal may be implemented in a programmable logic device (“PLD”).

Claims

1. A radar system for determining the range of targets, the system comprising:

(a) an RF signal generator, the generator generating an RF signal;

(b) an IF frequency generator, the IF frequency generator generating an IF modulation signal, an in-phase IF modulation signal, and an out-of-phase IF modulation signal;

(c) an IF modulator coupled to the RF signal generator and IF frequency generator, the IF modulator mixing the RF signal and the IF modulation signal to generate a transmit signal;

(d) an RF downconverter coupled to the RF signal generator, the RF downconverter mixing a received signal and the RF signal to generate an intermediate IF signal;

(e) an in-phase IF demodulator coupled to the RF downconverter and the IF frequency generator, the in-phase IF demodulator mixing the intermediate IF signal and the in-phase IF modulation signal to generate an in-phase baseband signal; and

(f) an out-of-phase IF demodulator coupled to the RF downconverter and the IF frequency generator, the out-of-phase IF demodulator mixing the intermediate IF signal and the out-of-phase IF modulation signal to generate an out-of1 phase baseband signal,

wherein the ratio of the amplitudes of the in-phase baseband signal and the out-of-phase baseband signal includes information about the range of the targets.

2. The radar system according to claim 1, further comprising a transmit antenna coupled to the IF modulator, the transmit antenna converting the transmit signal to an electromagnetic wave.

3. The radar system according to claim 2, further comprising a receive antenna coupled to the RF downconverter, the receive antenna receiving electromagnetic waves and converting them to the receive signal.

4. The radar system according to claim 1, wherein the IF frequency generator modulates the IF modulation signal with a pseudo random sequence.

5. The radar system according to claim 4, wherein the IF frequency generator modulates the in-phase IF modulation signal and the IF out-of-phase modulation signal with the pseudo random sequence.

6. The radar system according to claim 4, wherein the pseudo random sequence is 32 bits.

7. The radar system according to claim 6, wherein the pseudo random sequence is equal to one of 0000 0011 0111 1001 1110 1010 1001 0011 and any combination of inversion, bit-reversal, and rotation thereof.

8. The radar system according to claim 4, wherein the pseudo random sequence is 24 bits.

9. The radar system according to claim 8, wherein the pseudo random sequence is equal to one of 0000 0110 0010 1011 1101 1011 and any combination of inversion, bit reversal, and rotation thereof.

10. The radar system according to claim 4, wherein the pseudo random sequence is 16 bits.

11. The radar system according to claim 10, wherein the pseudo random sequence is equal to one of 0000 1001 0111 0111 and any combination of inversion, bit-reversal, and rotation thereof.

12. The radar system according to claim 4, wherein the pseudo random sequence is 12 bits.

13. The radar system according to claim 12, wherein the pseudo random sequence is equal to one of 0000 1011 1011 and any combination of inversion, bit-reversal, and rotation thereof.

14. The radar system according to claim 4, wherein the pseudo random sequence is 8 bits.

15. The radar system according to claim 14, wherein the pseudo random sequence is equal to one of 0001 0111 and any combination of inversion, bit-reversal, and rotation thereof.

16. The radar system according to claim 1, wherein the IF frequency generator includes:

a) an oscillator, the oscillator generating a predetermined clock rate; and

b) a plurality of counters coupled to the oscillator, the plurality of counters generating at least two different signals each signal have a different clock rate.

17. The radar system according to claim 16, wherein the clock rate of one of the at least two different signals corresponds to a clock rate of the IF modulation signal and the clock rate of the other of the at least two different signals corresponds to a clock rate of the in-phase IF modulation signal and the out-of-phase IF modulation signal.

18. The radar system according to claim 17, wherein the IF modulation signal has a clock rate of 1.25 MHz, the in-phase IF modulation signal and the out-of-phase IF modulation signal have a clock rate 83.33 KHz.

19. The radar system according to claim 17, wherein the IF frequency generator further includes a pseudo random number generator coupled one of the plurality of counters, the pseudo random number generator generating a predetermined sequence of numbers.

20. The radar system according to claim 19, wherein the IF frequency generator further includes a delay circuit coupled to the pseudo random number generator, the delay circuit adding a fixed delay to the predetermined sequence of numbers.

43. The radar system according to claim 1, further comprising:

a) a delay circuit coupled to the RF signal generator, the delay circuit delaying the RF signal;

b) a second RF downconverter coupled to the delay circuit, the second RF downconverter mixing the received signal and the delayed RF signal to generate a second intermediate IF signal;

c) a second in-phase IF demodulator coupled to the second RF downconverter and the IF frequency generator, the second in-phase IF demodulator mixing the second intermediate IF signal and the in-phase IF modulation signal to generate an imaginary in-phase baseband signal; and

d) a second out-of-phase IF demodulator coupled to the second RF downconverter and the IF frequency generator, the second out-of-phase IF demodulator mixing the second intermediate IF signal and the out-of-phase IF modulation signal to generate an imaginary out-of-phase baseband signal.

44. The radar system according to claim 43, wherein the delay circuit is a phase shifter and the phase shifter shifts the phase of the RF signal by 90 degrees.

45. The radar system according to claim 43, further comprising a transmit antenna coupled to the IF modulator, the transmit antenna converting the transmit signal to an electromagnetic wave.

46. The radar system according to claim 45, further comprising a receive antenna coupled to the RF downconverter and the delay circuit, the receive antenna receiving electromagnetic waves and converting them to the receive signal.

47. The radar system according to claim 43, wherein the IF frequency generator modulates the IF modulation signal with a pseudo random sequence.

48. The radar system according to claim 47, wherein the IF frequency generator modulates the in-phase IF modulation signal and the IF out-of-phase modulation signal with the pseudo random sequence.

49. The radar system according to claim 4, wherein the pseudo random sequence is 20 bits.

50. The radar system according to claim 49, wherein the pseudo random sequence is equal to one of 0000 0100 1110 1101 0111 and any combination of inversion, bit-reversal, and rotation thereof.

51. The radar system according to claim 4, wherein the pseudo random sequence is 28 bits.

52. The radar system according to claim 51, wherein the pseudo random sequence is equal to one of 0000 0101 1011 1010 1111 0010 0011 and any combination of inversion, bit-reversal, and rotation thereof.

53. The radar system according to claim 18, wherein the IF frequency generator further generates a demodulation signal having a clock rate of 1.333 MHz where the demodulation signal is mixed with the 1.25 MHz intermediate IF signal to generate the in-phase IF modulation signal and out-of-phase IF modulation signal having a clock rate of 83.33 KHz.

55. The radar system according to claim 48, wherein the pseudo random sequence is one of 32 bits, 28 bits, 24 bits, 20 bits, 16 bits, 12 bits and 8 bits in length.

56. The radar system according to claim 55, wherein the pseudo random sequence is equal to one of 0000 0011 0111 1001 1110 1010 1001 0011, 0000 0101 1011 1010 1111 0010 0011, 0000 0110 0010 1011 1101 1011, 0000 0100 1110 1101 0111, 0000 1001 0111 0111, 0000 1011 1011, 0001 0111 and any combination of inversion, bit-reversal, and rotation thereof.

21. A radar system for determining the range of targets, the system comprising:

(a) an RF signal generator, the generator generating an RF signal;

(b) a BPSK IF frequency generator, the BPSK IF frequency generator generating a BPSK IF modulation signal, a secondary IF modulation signal, an in-phase IF modulation signal, and an out-of-phase IF modulation signal;

(c) a BPSK modulator coupled to the RF signal generator and IF frequency generator, the BPSK modulator mixing the RF signal and the BPSK IF modulation signal to generate a transmit signal;

(d) an RF downconverter coupled to the RF signal generator, the RF downconverter mixing a received signal and the RF signal to generate a first intermediate IF signal;

(e) a BPSK demodulator coupled to the RF downconverter and the BPSK IF frequency generator, the BPSK demodulator mixing the first intermediate IF signal and the secondary IF modulation signal to generate a second intermediate IF signal;

(f) a dual BPSK demodulator coupled to the BPSK demodulator and the BPSK IF frequency generator, the dual BPSK demodulator mixing the second intermediate IF signal and the in-phase IF modulation signal to generate an real in-phase baseband signal and mixing the second intermediate IF signal and the out-of-phase IF modulation signal to generate an real out-of-phase baseband signal,

wherein the ratio of the amplitudes of the real in-phase baseband signal and the real out-of-phase baseband signal includes information about the range of the targets.

22. The radar system according to claim 21, further comprising:

a) an antenna, the antenna receiving electromagnetic waves and converting them to the receive signal and receiving a transmit signal and converting the transmit signal to electromagnetic; and

b) a circulator coupled to the antenna, the BPSK modulator and the RF downconverter, the circulator passing receive signals from the antenna to he RF downconverter and passing transmit signals from the BPSK modulator to the antenna.

23. The radar system according to claim 21, wherein the BPSK IF frequency generator modulates the IF modulation signal with a pseudo random sequence.

24. The radar system according to claim 23, wherein the BPSK IF frequency generator modulates the in-phase IF modulation signal and the out-of-phase modulation signal with the pseudo random sequence.

25. The radar system according to claim 24, wherein the pseudo random sequence is one of 32 bits, 28 bits, 24 bits, 20 bits, 16 bits, 12 bits and 8 bits in length.

26. The radar system according to claim 25, wherein the pseudo random sequence is equal to one of 0000 0011 0111 1001 1110 1010 1001 0011, 0000 0101 1011 1010 1111 0010 0011, 0000 0110 0010 1011 1101 1011, 0000 0100 1110 1101 0111, 0000 1001 0111 0111, 0000 1011 1011, 0001 0111 and any combination of inversion, bit-reversal, and rotation thereof.

27. The radar system according to claim 21, wherein the BPSK IF frequency generator includes:

a) an oscillator, the oscillator generating a predetermined clock rate; and

b) a plurality of counters coupled to the oscillator, the plurality of counters generating at least two different signals each signal have a different clock rate.

28. The radar system according to claim 27, wherein the clock rate of one of the at least two different signals corresponds to a clock rate of the IF modulation signal and the clock rate of the other of the at least two different signals corresponds to a clock rate of the in-phase IF modulation signal and the out-of-phase IF modulation signal.

29. The radar system according to claim 28, wherein the IF modulation signal has a clock rate of 1.25 MHz, the in-phase IF modulation signal and the out-of-phase IF modulation signal have a clock rate 83.33 KHz.

30. The radar system according to claim 29, wherein the WBPSK IF frequency generator further includes:

a) a pseudo random number generator coupled to the plurality of counters, the pseudo random number generator generating a predetermined sequence of numbers; and

b) a delay circuit coupled to the pseudo random number generator, the delay circuit adding a fixed delay to the predetermined sequence of numbers.

54. The radar system according to claim 29, wherein the IF frequency generator further generates a demodulation signal having a clock rate of 1.333 MHz where the demodulation signal is mixed with the 1.25 MHz intermediate IF signal to generate the in-phase IF modulation signal and out-of-phase IF modulation signal having a clock rate of 83.33 KHz.

31. A radar system for determining the range of targets, the system comprising:

(a) an RF signal generator, the generator generating an RF signal;

(b) a PN-coded BPSK IF frequency generator, the PN-coded BPSK IF frequency generator generating an PN-coded BPSK IF modulation signal, an in-phase PN-coded IF modulation signal, and an out-of-phase PN-coded IF modulation signal;

(c) a BPSK modulator coupled to the RF signal generator and PN-coded BPSK IF frequency generator, the BPSK modulator mixing the RF signal and the PN-coded BPSK IF modulation signal to generate a transmit signal;

(d) an RF downconverter coupled to the RF signal generator, the RF downconverter mixing a received signal and the RF signal to generate an intermediate PN-coded BPSK IF signal; and

(e) a dual BPSK demodulator coupled RF downconverter and the PN-coded BPSK IF frequency generator, the dual BPSK demodulator mixing the intermediate PN-coded BPSK IF signal with the in-phase PN-coded modulation signal to generate an in-phase baseband signal and mixing the intermediate PN-coded BPSK IF signal with the out-of-phase PN-coded modulation signal to generate an out-of-phase baseband signal,

wherein the ratio of the amplitudes of the in-phase baseband signal and the out-of-phase baseband signal includes information about the range of the targets.

32. The radar system according to claim 31, further comprising:

a) a transmit antenna coupled the BPSK modulator, the transmit antenna converting the transmit signal to an electromagnetic wave; and

b) a receive antenna coupled to the RF downconverter, the receive antenna receiving an electromagnetic wave and converting the received electromagnetic wave into the receive signal.

33. The radar system according to claim 32, further comprising a dual low pass filter coupled to the dual BPSK demodulator, the dual low pass filter anti-alias filtering the in-phase baseband signal and the out-of-phase baseband signal.

34. The radar system according to claim 33, wherein the PN-coded BPSK IF frequency generator modulates the PN-coded BPSK IF modulation signal with a pseudo random sequence.

35. The radar system according to claim 34, wherein the PN-coded BPSK IF frequency generator modulates the in-phase IF modulation signal and the out-of-phase IF modulation signal with the pseudo random sequence.

36. The radar system according to claim 35, wherein the pseudo random sequence is one of 32 bits, 28 bits, 24 bits, 20 bits, 16 bits, 12 bits and 8 bits in length.

37. The radar system according to claim 36, wherein the pseudo random sequence is equal to one of 0000 0011 0111 1001 1110 1010 1001 0011, 0000 0101 1011 1010 1111 0010 0011, 0000 0110 0010 1011 1101 1011, 0000 0100 1110 1101 0111, 0000 1001 0111 0111, 0000 1011 1011, 0001 0111 and any combination of inversion, bit-reversal, and rotation thereof.

38. The radar system according to claim 31, wherein the PN-coded BPSK IF frequency generator includes:

a) an oscillator, the oscillator generating a predetermined clock rate; and

b) a plurality of counters coupled to the oscillator, the plurality of counters generating at least two different signals each signal have a different clock rate.

39. The radar system according to claim 38, wherein the clock rate of one of the at least two different signals corresponds to a clock rate of the PN-coded BPSK IF modulation signal, and the clock rate of the other of the at least two different signals corresponds to a clock rate of the in-phase PN-coded IF modulation signal and the out-of-phase PN-coded IF modulation signal.

40. The radar system according to claim 39, wherein the PN-coded BPSK IF frequency generator further includes:

a) a pseudo random number generator coupled to the plurality of counters, the pseudo random number generator generating a predetermined sequence of numbers; and

b) a delay circuit coupled to the pseudo random number generator, the delay circuit adding a fixed delay to the predetermined sequence of numbers.

41. The radar system according to claim 40, the system further comprising a dual analog to digital (A/D) converter coupled the dual low pass filter, the dual A/D converter converting the in-phase baseband signal from an analog signal to a digital signal and converting the out-of-phase baseband signal from an analog signal to a digital signal.

42. The radar system according to claim 41, the system further comprising a digital signal processor (“

DSP”

) coupled to the dual A/D converter, the DSP processing the digital in-phase baseband signal and the digital out-of-phase baseband signal to interpret range information about the targets.