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High-resolution radars with large frequency bandwidth are widely used for the detection and location of subsurface objects (Daniels et at. 1988). The most common wideband signal is the very short pulse (impulse) utilized in short pulse radars (impulseradars). In the ideal case the impulse is a one-sided sinusoidal or gaussian signal (Esselle & Stuchly 1991). In practice the signal contains a few oscillation periods at a particular operation frequency. Frequencies of the order of 100 MHz are used in the measurement of large objects (e.g. ground), where high penetration depth is needed and range resolution of 0.1-1 m is adequate. If range resolution of the order of centimetres is desired, the frequency of the radar must be 1000 MHz or more.