A radar system is capable of transmitting necessary information through a very small amount of data from a radar device to a host device via a bus with a limited bandwidth. A radar sensor generates a beat signal between a transmission signal and a reflected signal from a target. A signal processor determines a spectrum of the beat signal and compresses the data indicating the spectrum. The resultant compressed data is transmitted to the host device via a bus. The host device decompresses the received data thereby reproducing the spectrum data. The host device then detects the target on the basis of the reproduced spectrum data.