WE CLAIM:
1. A radar apparatus comprising:
a plurality of transmission radars for generating mutually different modulation codes by cyclically shifting the same code sequence by mutually different cyclic shift amounts, generating mutually different transmission signals using the mutually different modulation codes, and emitting the mutually different transmission signals;
a reception radar for receiving reflected waves of the transmission signals reflected by a target to be observed after the transmission signals are emitted from the plurality of transmission radars, and outputting a reception signal of the reflected waves;
a signal processor for performing code demodulation on the reception signal output from the reception radar, using the modulation codes generated by the plurality of transmission radars; and
a target detecting unit for detecting the target on a basis of a signal subjected to the code demodulation performed by the signal processor.
2. The radar apparatus according to claim 1, wherein the plurality of transmission radars use an M-sequence as the code sequence.
3. The radar apparatus according to claim 1, wherein the signal processor includes:
a frequency domain converting unit for converting the reception signal output from the reception radar into a frequency domain signal; and
a code demodulating unit for performing code demodulation on the frequency domain signal converted by the frequency domain converting unit, using the modulation codes generated by the plurality of transmission radars.

4. The radar apparatus according to claim 3, wherein the signal processor includes an integration unit for integrating the signal subjected to the code demodulation performed by the code demodulating unit, and outputting the integrated signal to the target detecting unit.
5. The radar apparatus according to claim 4, wherein the integration unit includes a first integration unit for coherently integrating the signal subjected to the code demodulation performed by the code demodulating unit, by performing hit-direction complex integration on the signal subjected to the code demodulation.
6. The radar apparatus according to claim 5, wherein the integration unit includes a second integration unit for integrating the signal integrated by the first integration unit, on a basis of positions of the plurality of transmission radars, a position of the reception radar, and an assumed value of an angle with the target.
7. The radar apparatus according to claim 4, wherein the integration unit includes a first integration unit for coherently integrating the signal subjected to the code demodulation performed by the code demodulating unit, by performing hit-direction Fourier Transform on the signal subjected to the code demodulation.
8. The radar apparatus according to claim 7, wherein the integration unit includes a second integration unit for integrating the signal integrated by the first integration unit, on a basis of positions of the plurality of transmission radars, a position of the reception radar, and an assumed value of an angle with the target.

9. The radar apparatus according to claim 1, wherein the plurality of transmission
radars use, as the code sequence, a cyclic code having a cross-correlation value that varies with cyclic shift amounts, set mutually different cyclic shift amounts on a basis of a value of integral of the cross-correlation value with the cyclic code, and cyclically shift the code sequence by the set cyclic shift amounts.