Communications: radio wave antennas – Antennas – With coupling network or impedance in the leadin
Patent
1997-09-29
1999-11-02
Wong, Don
Communications: radio wave antennas
Antennas
With coupling network or impedance in the leadin
343772, 343776, 343778, H01Q 2100, H01Q 1300
Patent
active
059779306
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a phased array antenna comprising an array of waveguide radiators connected to a supply system and furthermore comprising a calibration network for calibrating the supply system.
DISCUSSION OF THE BACKGROUND
A phased array antenna of this type is known from the European patent specification EP-B 0.110.260. This patent specification describes a pulse radar apparatus comprising a coherent transmitting and receiving unit incorporating a transmitter, a transmitting antenna, a number of receiving antennas connected to coherent receivers which are suitable for converting, by phase-coherent detection, echo signals into quadrature video signals having two components. The coherent transmitting and receiving unit additionally incorporates a beam former, the transmitter being suitable for the transmission of test signals in a test phase in the course of which the test signals are injected into the receiver channels. On the basis of the video signals generated by the receivers, the amplitude and phase-correcting signals are determined which are representative of the amplitude and phase errors introduced by the receivers. The need to provide a calibration or test network stems from the fact that differences in gain and phase of the receivers may constitute an impediment to a desired side-lobe reduction. The drawback of the prior art phased array antenna is that the test signal is injected directly into the receiver channels. As a result, phase and amplitude errors generated beyond the receiver channels, for instance in the connection between receiver and waveguide radiators and in a transformer element generally comprised in the waveguide radiators, are not included in the test procedures and, hence, are not compensated for. A possible solution is to inject the test signal by means of a separate feedhorn to be placed in front of the antenna. This however has the drawback that compensation is also required for errors caused by the distance between the feedhorn and a waveguide radiator being different for each waveguide radiator.
SUMMARY OF THE INVENTION
The phased array antenna according to the invention has for its object to provide a solution to this problem by injecting the test signal directly into at least substantially all waveguide radiators. This entails the advantage that phase and amplitude errors generated in the waveguide radiators are also included in the test procedure. It is characterized in that at least substantially all waveguide radiators comprise a coupling device connected to the calibration network.
In phased array antennas provided with waveguide radiators, the supply system generally comprises a T/R module per waveguide radiator or per group of waveguide radiators. As a result there is insufficient room at the input to provide a coupling device to be connected to the calibration network. At the output of a waveguide radiator there is no room available either for a coupling device to be connected to the calibration network, as the output has to be free from obstacles in order to ensure an undisturbed emission of radiant energy. A special embodiment offers a solution to the above-mentioned problem and is thereto characterized in that the coupling device is mounted at a side wall of the waveguide radiators.
The calibration network is required to ensure a low-loss transmission of microwave energy. To this end, use is generally made of a stripline network in which Duroid generally serves as a dielectric. Such a network is however very expensive. A favorable embodiment of the phased array antenna according to the invention is aimed at realising a far less expensive calibration network and is thereto characterized in that the calibration network comprises at least one waveguide.
If the waveguide-shaped calibration network is mounted between the waveguide radiators such that it abuts on the side walls of the waveguide radiators, due care should be taken that the distance between the rows of waveguide radiators is kept a
REFERENCES:
patent: 4742355 (1988-05-01), Wolfson et al.
patent: 5014022 (1991-05-01), Wolfson et al.
Fischer Henk
Klein Breteler Antonius B. M.
Hollandse Signaalapparaten B.V.
Malos Jennifer H.
Wong Don
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