In [1] was shown, that if in the method of synthetic aperture to use a weighting function, approximate equal to the pattern of a used antenna in the tested regions, it will increase the signal to noise ratio up to 4 dB. However it is known, that the pattern of real antenna depends on frequency, especially in the regions with dispersion, such as a ground. Therefore the using of frequency properties of antenna pattern in weighting function must additionally increase signal to noise ratio. In the case of continuous signal of variable frequency it can be made as follows. In each point on a surface of the tested regions receive a reflected signal for a number of discreet frequencies. Separately for signal on each of these frequency applied a synthetic aperture method with the weighting function, that are equal the product of the pattern of using antenna on a given frequency and phase multiplier, that depends on frequency and coordinates of point in the testing regions. Then the signals on each frequency are summarized and we get the amplitude of reflections for this point. After the recurrence of a given procedure for all points of a regions under testing we can receive the distribution of buried reflectors. Analytical testing shows that this technique provides additional increase signal to noise ratio on 3-7dB. This value depends on accuracy of the approximation of frequency dependence of the antenna diagram in controllable regions. REFERENCES

1. I. Arai, T. Suzuki. Experimental Results on Subsurface Radar with Improved Resolution. Journal of Electromagnetic Waves and Applications, Vol. 7, No. 11, 1993, 1479-1495.
2. G. N. Deshchenko, A. A. Kovalchuk. The computing method of high-resolution determination the inhomogeneities depth in dielectric objects. International Conference "Computer Method and Inverse Problems in Nondestructive Testing and Diagnostics", 21-24 November, 1995, Minsk, Belarus.