Abstract: A transmitting channel includes a pulse generator unit for generating frequency or phase code modulated pulses having a common centre frequency. The pulses are transformed to a transmitting frequency in the transmitting channel. An antenna, which is connected to the output of the transmitting channel, radiates the transformed frequency pulses and receives return signals. A receiver channel processes the return signals. The receiver channel includes a pulse compressor unit for compressing the return signals. Each pulse to be transmitted consists of two or more sub pulses, at least one of the sub pulses being substantially longer than at least another one of the sub pulses. Each sub pulse is coded with a different compression code. The compression code of each sub pulse having a low cross-correlation property with the compression codes of all other sub pulses, all sub pulses having the same center frequency.