Spread spectrum radar apparatus
A spread spectrum radar apparatus includes: a transmission unit which generates a spread signal that is a spectrum-spread signal, using a first oscillator signal, a second oscillator signal, and a transmission PN code, and which emits the spread signal as a detection radio wave; and a reception unit which receives, as a reception signal, the detection radio wave reflected from an object, and which generates an intermediate frequency signal by despreading the reception signal based on the first oscillator signal and a reception PN code obtained by delaying the transmission PN code.
1. A spread spectrum radar apparatus, comprising:
a first local oscillator which generates a first oscillator signal;
a second local oscillator which generates a second oscillator signal;
a first pseudo-noise code generating circuit which generates a first pseudo-noise code;
a second pseudo-noise generating circuit which generates a second pseudo-noise code;
a transmission circuit which generates a spread signal that is a spectrum-spread signal, using the first oscillator signal, the second oscillator signal, and the first pseudo-noise code, and which emits the spread signal as a detection radio wave; and
a reception circuit which receives, as a reception signal, the detection radio wave reflected from an object, and which generates an intermediate frequency signal by the reception circuit despreading a spectrum of the reception signal based on the first oscillator signal and the second pseudo-noise code being generated by delaying the first pseudo-noise code,
wherein a frequency associated with the first pseudo-noise code is higher than a frequency of the second oscillator signal.
2. The spread spectrum radar apparatus according to claim 1 , the reception circuit comprising:
a balanced modulator which generates a modulation signal by modulating a phase of the reception signal based on the second pseudo-noise code to despread the spectrum of the reception signal; and
a quadrature demodulator which outputs, as the intermediate frequency signal, an in-phase signal and a quadrature signal which are included in the modulation signal.
3. The spread spectrum radar apparatus according to claim 2 ,
wherein the quadrature demodulator includes:
a phase shifter which generates a third oscillator signal in which a shift amount with respect to the first oscillator signal is different by 90 degrees;
a first balanced modulator which generates the in-phase signal by mixing the modulation signal and the first oscillator signal; and
a second balanced modulator which generates the quadrature signal by mixing the modulation signal and the third oscillator signal.
4. The spread spectrum radar apparatus according to claim 2 , wherein the reception circuit includes:
a first band-pass filter to which the in-phase signal is inputted from the quadrature demodulator, and which allows a band from among frequency components of the in-phase signal to pass, the band having the frequency of the second oscillator signal as a center frequency;
a second band-pass filter to which the quadrature signal is inputted from the quadrature demodulator, and which allows a band from among frequency components of the quadrature signal to pass, the band having the frequency of the second oscillator signal as the center frequency;
a first amplifier which outputs a signal intensity and a signal amplified by limiting an amplitude of a signal which has passed the first band-pass filter, the signal intensity being proportional to a logarithm of intensity of the signal which has passed the first band-pass filter; and
a second amplifier which outputs a signal intensity and a signal amplified by limiting an amplitude of a signal which has passed the second band-pass filter, the signal intensity being proportional to a logarithm of intensity of the signal which has passed the second band-pass filter.
5. The spread spectrum radar apparatus according to claim 2 ,
wherein the quadrature demodulator includes:
a phase shifter which alternately outputs the first oscillator signal and a third oscillator signal in which a shift amount with respect to the first oscillator signal is different by 90 degrees; and
a balanced modulator which alternately generates the in-phase signal and the quadrature signal by mixing the modulation signal and the signal outputted from the phase shifter.
6. The spread spectrum radar apparatus according to claim 2 ,
wherein the reception circuit includes:
a band-pass filter to which the in-phase signal and the quadrature signal are alternately inputted from the quadrature demodulator, and which allows a band from among frequency components of the in-phase signal and the quadrature signal to pass, the band having the frequency of the second oscillator signal as a center frequency; and
an amplifier which outputs a signal intensity and a signal amplified by limiting an amplitude of a signal which has passed the band-pass filter, the signal intensity being proportional to a logarithm of intensity of the signal which has passed the band-pass filter.
7. The spread spectrum radar apparatus according to claim 2 , further comprising:
a signal processing circuit which calculates an intensity of the reception signal based on the quadrature signal and the in-phase signal, checks the intensity with a reference value, and judges whether or not the object is present.
8. The spread spectrum radar apparatus according to claim 2 , further comprising:
a signal processing circuit which identifies a time for which the first pseudo-noise code is delayed in order for the second pseudo-noise code to be generated, and which calculates, based on the in-phase signal and the quadrature signal, a distance to the object from the identified time.
9. The spread spectrum radar apparatus according to claim 2 , further comprising:
a signal processing circuit which calculates a phase of the reception signal based on the second oscillator signal, the in-phase signal, and the quadrature signal, and calculates a relative velocity for the object based on time variations in the phase.
10. The spread spectrum radar apparatus according to claim 1 ,
wherein the transmission circuit generates an intermediate signal by mixing the first oscillator signal and the second oscillator signal, and generates the spread signal by modulating a phase of the intermediate signal based on the first pseudo-noise code.
11. The spread spectrum radar apparatus according to claim 10 ,
wherein the transmission circuit further includes:
a first balanced modulator which generates the intermediate signal by mixing the first oscillator signal and the second oscillator signal; and
a second balanced modulator which generates the spread signal by modulating a phase of the intermediate signal based on the first pseudo-noise code.
12. The spread spectrum radar apparatus according to claim 1 ,
wherein the transmission circuit generates an intermediate signal by modulating a phase of the second oscillator signal based on the first pseudo-noise code, and generates the spread signal by mixing the intermediate signal and the first oscillator signal.
13. The spread spectrum radar apparatus according to claim 12 ,
wherein the transmission circuit includes:
a first balanced modulator which generates the intermediate signal by modulating a phase of the second oscillator signal based on the first pseudo-noise code; and
a second balanced modulator which generates the spread signal by mixing the intermediate signal and the first oscillator signal.
14. The spread spectrum radar apparatus according to claim 1 ,
wherein the transmission circuit generates an intermediate signal by modulating a phase of the first oscillator signal based on the first pseudo-noise code, and generates the spread signal by mixing the intermediate signal and the second oscillator signal.
15. The spread spectrum radar apparatus according to claim 14 ,
wherein the transmission circuit further includes:
a first balanced modulator which generates the intermediate signal by modulating a phase of the first oscillator signal based on the first pseudo-noise code; and
a second balanced modulator which generates the spread signal by mixing the intermediate signal and the second oscillator signal.
16. The spread spectrum radar apparatus according to claim 1 ,
wherein the first pseudo-noise code generating circuit generates an M sequence code as the first pseudo-noise code; and
the second pseudo-noise code generating circuit generates the M sequence code as the second pseudo-noise code.
17. The spread spectrum radar apparatus according to claim 1 , further comprising:
a random signal generating circuit which generates a random signal that randomly changes a frequency of the first oscillator signal.
18. The spread spectrum radar apparatus according to claim 1 , wherein a frequency of the second oscillator signal is one-integer-th of a frequency of a cycle of the first pseudo-noise code.
19. A spread spectrum radar apparatus, comprising:
a first local oscillator which generates a first oscillator signal;
a first pseudo-noise code generating circuit which generates a first pseudo-noise code;
a second pseudo-noise generating circuit which generates a second pseudo-noise code;
a transmission circuit which modulates the first oscillator signal with the first pseudo-noise code, and which emits, as a detection radio wave, a spread signal that is a spectrum-spread signal;
a reception circuit which receives, as a reception signal, the detection radio wave reflected from an object, and which generates a demodulation signal by despreading the reception signal based on the second pseudo-noise code and the first oscillator signal;
a repetition code generating circuit which generates a repetition code by generating a code using a predetermined frequency; and
an exclusive OR operation circuit which outputs, as the second pseudo-noise code, a result obtained by performing an exclusive OR operation between the repetition code and a pseudo-noise code obtained by delaying the first pseudo-noise code.
20. The spread spectrum radar apparatus according to claim 19 ,
wherein the repetition code generating circuit and the exclusive OR operation circuit are integrated in a semiconductor integrated circuit.
21. The spread spectrum radar apparatus according to claim 19 , wherein a half of a clock frequency of the repetition code is one-integer-th of a frequency of a cycle of the first pseudo-noise code.
22. A spread spectrum detection methods comprising:
generating a spread signal that is a spectrum-spread signal, using a first oscillator signal, a second oscillator signal, and a first pseudo-noise code, and emitting the spread signal as a detection radio wave to detect an object; and
receiving, as a reception signal, the detection radio wave reflected from the object, and generating an intermediate frequency signal by despreading a spectrum of the reception signal based on the first oscillator signal and a second pseudo-noise code obtained by delaying the first pseudo-noise code,
wherein a frequency associated with the first pseudo-noise code is higher than a frequency of the second oscillator signal.