US 6,204,809 B1Granted

Radio wave receiving apparatus having an improved antenna resolution

AssigneeNational Space Development Agency

InventorToshihiro Sezai

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Abstract

A radio wave receiving apparatus including a signal processing circuit which performs on Fourier transform with respect to an azimuth of an electric field signal outputted from an antenna receiving circuit. The Fourier transform is also performed with respect to an azimuth of the antenna pattern of an antenna. The Fourier transform signal derived from the electric field signal is then divided by the antenna pattern Fourier transform signal. A low-pass filter subjects the divided signal to low-pass filtering. The band of the output signal of the low-pass filter is extended into that beyond the cut-off frequency of the low-pass filter by using extrapolation. The band-extended signal is subjected to Fourier inverse transform with respect to azimuth, the signal after the Fourier inverse transform being outputted as a final antenna output. The antenna resolution thereof is improved by thus using a transfer function in the azimuthal frequency domain resulting from the Fourier transform with respect to azimuth of the antenna pattern.

Claims4

Dependent claims

A radio wave receiving apparatus having an antenna for receiving radio wave and means for moving the pointing direction of an antenna beam of the antenna toward directions for improving resolution, said radio wave receiving apparatus comprising:

means for effecting a Fourier transform with respect to azimuth of a received electric field signal obtained from the antenna while moving said antenna beam;
means for effecting a Fourier transform with respect to azimuth of a received electric field pattern of the antenna in the presence of one point wave source;
means for dividing a signal resulting from the Fourier transform with respect to azimuth of said antenna received electric field signal by a signal resulting from the Fourier transform with respect to azimuth of said received electric field pattern of the antenna in the presence of one point wave source;
a low-pass filter for subjecting the signal divided at the division means to a low-pass filtering with respect to an azimuthal frequency;
band extention means for extending the output signal of the low-pass filter into a azimuthal frequency region beyond the cut-off of the low-pass filter by using extrapolation;
and
means for subjecting the signal extended by the band extention means to a Fourier inverse transform with respect to azimuth,
the signal after being subjected to said Fourier inverse transform being outputted as a final antenna output.

5 more elements

Dependencies are inferred from the claim text.