National Space Development Agency of Japan

Japan Aerospace Exploration Agency

National Space Development Agency

Toshihiro Sezai

Yuji Osawa

An antenna according to an embodiment of the present invention includes a primary radiator and a reflector mirror. The primary radiator radiates radio waves. The reflector mirror reflects radio waves radiated from the primary radiator, has same aperture diameter and height as a parabolic reflector mirror whose aperture diameter is equal to or less than 1.7 times a wavelength of the radio waves, and has a non-parabolic surface as a mirror surface shape.

Antenna, electronic apparatus, and method of manufacturing an antenna

An observation apparatus includes a signal processing unit that performs, using a square root signal of a received electric power signal from an antenna whose beam is scanned within a predetermined azimuthal angle range and a signal of an azimuthal angle of the scanned beam, a Fourier transform with respect to the azimuthal angle on the square root signal, divides a first azimuth frequency signal by a second azimuth frequency signal, the first azimuth frequency signal being obtained by performing the Fourier transform, the second azimuth frequency signal being obtained by performing a Fourier transform with respect to the azimuthal angle on a square root signal of an antenna electric power pattern, and fits the divided signal with exponential functions including real parts and imaginary parts in arguments by using Prony's method.

Observation apparatus, observation method, and program

A signal processing unit performs, on the basis of a received electric field signal from an antenna by which a beam is scanned within a predetermined azimuthal angle and a signal of an azimuthal angle of the scanned beam, a Fourier transform on a distribution function of the received electric field signal into a frequency domain of the azimuthal angle, divides a signal according to a first spectral function by a signal according to a second spectral function, the first spectral function being obtained by performing the Fourier transform, the second spectral function being obtained by performing a Fourier transform on an antenna pattern of the antenna into a frequency domain of the azimuthal angle, and subjects the divided signal to fitting by using Prony's method with exponential functions including real parts and imaginary parts in arguments.

Provided is an antenna including: a primary radiator configured to radiate radio waves; and a parabolic reflector configured to reflect the radio waves radiated by the primary radiator and has an aperture diameter reduced to be equal to or smaller than an aperture diameter with which no null points are generated in an antenna pattern in a semi-sphere where the radio waves are reflected and radiated.

Antenna

Method for calibrating a total-power microwave radiometer for a satellite

Provided herein is a radio wave receiving apparatus including a signal processing circuit comprising: a means for the Fourier transform in respect of azimuth of an electric field signal outputted from an antenna receiving circuit; a means for the Fourier transform in respect of azimuth of the antenna pattern of an antenna; a means for dividing the Fourier transform signal derived from the electric field signal by the antenna pattern Fourier transform signal; a low-pass filter for subjecting the divided signal to low-pass filtering; a means for extracting exponential function components of the output signal of the low-pass filter; a means for extending the band of the output signal of the low-pass filter beyond the cut-off frequency of the low-pass filter by using the exponential function components; and a means for subjecting the band-extended signal to Fourier inverse transform in respect of 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 in respect of azimuth of the antenna pattern.

Radio wave receiving apparatus having an improved antenna resolution

A radio wave source information display apparatus including: a signal processing circuit having a means for performing the Fourier transform with respect to azimuth of an electric field signal outputted from an antenna receiving circuit, a means for performing the Fourier transform with respect to azimuth of the antenna pattern of an antenna, a means for dividing the Fourier transform signal derived from the electric field signal by the antenna pattern Fourier transform signal, a low-pass filter for subjecting the divided signal to low-pass filtering with respect to azimuthal frequency, a means for extracting exponential function components of the output signal of the low-pass filter, and a means for obtaining radio wave source information from the extracted exponential function components; and a display section for displaying radio wave source information obtained at the signal processing circuit. Provided hereby is the radio wave source information display apparatus in which exponential function components contained in a radio wave source spectrum signal obtained in the process of applying deconvolution method to antenna response is extracted so as to directly obtain and display radio wave source information.

Radio wave source information display apparatus

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.

A radio wave receiving apparatus including having improved antenna resolution. The apparatus includes a signal processing circuit; a circuit for performing the Fourier transform with respect to an azimuth of an electric field signal outputted from an antenna receiving circuit; a circuit for performing the Fourier transform with respect to an azimuth of the antenna pattern of an antenna; a circuit for dividing the Fourier transform signal resulting from the electric field signal by the antenna pattern Fourier transform signal; and a circuit for passing the divided signal through a low-pass filter in respect of azimuthal frequency and then subjecting it to a Fourier inverse transform in respect of azimuth, so as to output the signal after the Fourier inverse transform as a final antenna output, thereby improving the antenna resolution by using a transfer function in the azimuthal frequency domain resulting from the Fourier transform of the antenna pattern with respect to an azimuth.

An antenna system is made up by a main antenna and a sub antenna which is adjacent the main antenna in a direction not perpendicular to the direction of beam scan of the main antenna and which has a beam axis coincident with a beam axis of the main antenna. Antenna beams of the antenna system are scanned by a scan device. Received signals of both the antennas are subjected to a multiplication process under phase coherent condition in a phase-coherent multiplying device. A signal corresponding to a maximum frequency component in the output signal of the phase-coherent multiplying device is output by a frequency discriminating device and then subjected to a signal conversion process in a signal converting device. Information about a radio wave source only in the direction of the antenna beams is thus obtained.

Antenna device

In a method of designing the transmission power of a synthetic aperture radar installed on a flight object such as an artificial satellite, the transmission power is designed such that, in applying radar equation P.sub.r =P.sub.t .multidot..sigma..multidot.A.sub.p.sup.2 /(4.pi..lambda..sup.2 R.sup.4) [P.sub.t :transmission power (W), .sigma.: radar scattering cross section (m.sup.2), A.sub.p :antenna area (m.sup.2), R: distance to the object to be observed (m), .lambda.: wavelength of radio wave (m)] for setting transmission power P.sub.r so as to satisfy the conditions required for the radar, the radar scattering cross section .sigma. is set to .sigma.=.sigma..sup.0 .multidot.S.sup.2 .multidot.4.pi./ .lambda..sup.2 [.sigma..sup.0 :scattering coefficient, S:area of irradiated domain (m.sup.2)].

Method of designing transmission power in synthetic aperture radar

An active reflector including an antenna, a frequency converter, and a delay circuit is placed at a location within an area to be detected by a synthetic aperture radar. The active reflector receives an incoming radio wave emitted by the synthetic aperture radar and changes its frequency or delay time. The resultant radio wave is transmitted as a reflected radio wave toward the synthetic aperture radar. As a result, the position of the active reflector image displayed on the screen of the synthetic aperture radar is shifted. The ambiguity is quantitatively detected from the pixel value at the original display position at which the active reflector image was displayed before it was shifted, thereby evaluating the image quality of the synthetic aperture radar.

Method of evaluating the image quality of a synthetic aperture radar

An antenna system comprising two similar antennas with a monopulse feed system is scanned while transmitting in-phase radio waves from the two antennas. Reflected radio waves are received by the two antennas and fed to a hybrid circuit which in turn produces a sum signal .SIGMA. and a difference signal .increment.. After detection is performed by a detector, a signal processing unit performs double differential processing on the sum signal .SIGMA. and the differential signal .increment.. In this processing step, the sum signal is output only if the double differential coefficient of said sum signal is equal to or less than a predefined positive real number value and if the double differential coefficient of said difference signal is equal to or greater than a predefined negative real number value, and a zero signal is output in any other cases. Thus, the beam width of an antenna pattern is compressed without missing a necessary output signal.

Method of performing beam compression process on antenna pattern of radar

An antenna system is formed by arranging a sub-antenna adjacent to a main antenna along the direction of the beam width to be reduced of the main antenna and in such a way that the beam axis of the sub-antenna is coincident with that of the main antenna. The antenna beam of this antenna system is scanned along the beam width direction and received signals obtained by the main and sub-antennas are set in phase and subjected to multiplication and signal processing by a multiplication circuit and signal processing circuit. When the ratio of the value of the synthetic reception pattern obtained by the multiplication to the maximum set value of the radar display device is not less than a preset value, the received signal of the main antenna corresponding to the range of angle of the beam width of the synthetic reception pattern is output as the final output signal instead of the synthetic reception pattern, and, when the ratio of the value of the synthetic reception pattern to the maximum set value is less than the preset value, the output is cut off.

Beam compression method for radar antenna patterns

An antenna system comprising two similar radiation antenna elements with a single monopulse feed system is scanned while transmitting in-phase radio waves from the two elements. Reflected radio waves are received by the two elements and fed to a hybrid circuit which in turn produces a sum signal .SIGMA. and a difference signal .DELTA.. After detection is performed by a detector, a signal processing unit subtracts the difference signal .DELTA. from the sum signal .SIGMA.. In this processing step, the output signal produced by the above subtraction process is actually output only if the receiving pattern waveform associated with the sum signal .SIGMA. has an upwardly convex form, that is, its double differential coefficient is negative and further if the receiving pattern waveform associated with the difference signal .DELTA. has a downwardly convex form, that is, its double differential coefficient is positive, whereby an antenna pattern with beam compression is provided.

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Tokyo, Japan

Toshihiro Sezai