Method for radar mapping an area and a radar equipment to carry out the method
First Claim
1. A synthetic aperture radar equipment SAR, for radar mapping an area at frequencies below 300 MHz with suppression of speckle and including mapping of structures concealed by dielectrical layers, the radar equipment including transmitter means, antenna means, receiver means and registration means, especially carried by an aeroplane, wherein the transmitter means comprises means to generate a number N of signals with discrete frequencies, distributed over a wideband frequency interval and which are determined as to phase and frequency in that they are different harmonics to a determined fundamental frequency, and which signals are connected in groups to a number M of power amplifiers, where M is smaller than N, in such a way that each such group corresponds to a smaller frequency interval and these smaller frequency intervals cover said wideband frequency interval essentially without overlapping, and a number M of antennas with tuning frequencies adapted to respective smaller frequency interval and the receiver means comprises a number M of pre-amplifiers, the inputs of which are connected to different said antennas and the outputs of which are each connected to a number of mixers, the sum of which are N, said means to generate a number N of mixing frequencies and the conducting of these to respective mixer, a number N of low-pass filters, the inputs of which are connected to different mixers, and a means of registration that is connected to the low-pass filters.
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Abstract
The invention relates to a method for radar mapping an area and a radar equipment for wideband exploration at frequencies below 300 MHz. A large number of frequencies, for instance 1000, are distributed over a frequency band between for instance 12.5 and 200 MHz, and approximately corresponding to terms in a geometrical series but being different harmonics to a certain fundamental frequency. This is accomplished by a synthesis generator (1) coupled to a phase control device (7) and the generated frequencies are each amplified in a separate amplifier (2), the outputs of which are guided in groups to a number of antennas, tuned to different frequency bands and fewer than the number of frequencies. The reception is carried out in a similar way from the antennas with pre-amplifiers and a mixer (3) each and an A/D-converter (4) and a registration device (5). The equipment is meant to use the principle of so called synthetic aperture (SAR).
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Citations
4 Claims
- 1. A synthetic aperture radar equipment SAR, for radar mapping an area at frequencies below 300 MHz with suppression of speckle and including mapping of structures concealed by dielectrical layers, the radar equipment including transmitter means, antenna means, receiver means and registration means, especially carried by an aeroplane, wherein the transmitter means comprises means to generate a number N of signals with discrete frequencies, distributed over a wideband frequency interval and which are determined as to phase and frequency in that they are different harmonics to a determined fundamental frequency, and which signals are connected in groups to a number M of power amplifiers, where M is smaller than N, in such a way that each such group corresponds to a smaller frequency interval and these smaller frequency intervals cover said wideband frequency interval essentially without overlapping, and a number M of antennas with tuning frequencies adapted to respective smaller frequency interval and the receiver means comprises a number M of pre-amplifiers, the inputs of which are connected to different said antennas and the outputs of which are each connected to a number of mixers, the sum of which are N, said means to generate a number N of mixing frequencies and the conducting of these to respective mixer, a number N of low-pass filters, the inputs of which are connected to different mixers, and a means of registration that is connected to the low-pass filters.
Specification