GB2199447A

GB2199447A - Monitoring arrangement for a receive array system

Info

Publication number: GB2199447A
Application number: GB08426954A
Authority: GB
Inventors: Andrew Chi-Chung Wong; Andrew Peter Norris; Stuart James Dean
Original assignee: STC PLC; Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1984-10-25
Filing date: 1984-10-25
Publication date: 1988-07-06
Also published as: GB8426954D0; GB2199447B

Abstract

For monitoring a receive array system having a reflector (10) focussed upon an array (11) of antenna elements each feeding an individual signal channel, the reflector is fitted with at least one substantially point source (12, 13) of test or calibration signals directed toward the element array. <IMAGE>

Description

MONITORING ARRANGEMENT FOR A RECEIVE ARRAY SYSTEM This invention relates to a monitoring arrangement for a receive array system having a reflector, which may for instance be parabolic or cylindrical with a linear array feeding a number of receive channels. A monitoring arrangement will allow any drafts in phase and amplitude tracking between the channels to be detected and corrected fron in the subsequent signal processing algorithm.

One known way to monitor a receive array system is to generate a test signal which is injected locally into the feed signal channels immediately behind each array element. This requires relatively complex circuitry in order that the phase and amplitudes of the calibration signals can be sufficiently good to be used as a -reference and cannot indicate if there is any malfunction or damage to the actual array elements. An alternative is to use a far field source which, in theory, illuminates all the array elements substantially evenly. However this pre-supposes the availability of a suitable site far enough away for the far field source at all times and minimal disturbance from local multi-path sources.

According to the present invention there is provided a monitoring arrangement for a receive array system having a reflector focussed upon an array of antenna elements each feeding an individual signal channel, characterised in that the reflector is fitted with at least one substantially point source of test or calibration signals directed toward the element array.

Embodiments of the invention will now be described with reference to the accompanying drawing which depicts a reflector 10 focussed on a linear array 11 of receive antennas. The monitoring arrangement comprises a pair of horn transmitters 12, 13 mounted at each end of the reflector on the centre line thereof.

The horn transmitters are fed from a source 14 of special test or calibration signals. In a preferred mode of operation the horns are energised alternately so that each horn in turn illuminates the entire element array.

Whilst the distance from horn 12 to element lia is the shortest and to element ila is the longest, for horn 13 the reverse is true. The distances from both horns to the centre of the array are equal. The system includes signal processing means (not shown) which examines and analyses the signals received in each element channel from both horns and, after making due allowance for the differences in horn-to-element distances, evaluates the performance of each channel. Such a monitoring arrangement automatically compensates for, e.g.

mechanical expansion of the array mounting due to temperature changes.

In an alternative embodiment (not illustrated) a single horn transmitter is located in an aperture in the centre of the reflector. In this case only one calibration signal is required. The signal processor has to allow for the differences in path lengths between the horn and the elements, but there is balancing required as a consequence of this.

Since the invention is effectively using near field sources there is no significant multi-path disturbance to be considered. Also, since there is no multiplicity of additional cabling as required by the local injection technique costs are reduced and alterations in cable lengths are minimised. Test and calibration procedures can be carried whenever desired and without the need for special site requirements such as are necessary for far field source monitoring.

Claims

CLAIMS:-

1. A monitoring arrangement for a receive array system having a reflector focussed upon an array of antenna elements each feeding an individual signal channel, characterised in that the reflector is fitted with at least one substantially point source of test or calibration signals directed toward the element array.

2. An arrangement according to claim 1 characterised in that the array is a linear array and that the reflector is fitted with two substantially point sources of test or calibration signals directed toward the array one at each end of the reflector opposite the respective ends of the linear array.

3. An arrangement according to claim 1 characterised in that the array is a linear array and that the point source is fitted in the centre of the reflector.

4. A monitoring arrangement for a receive array radar substantially as described with reference to the accompanying drawing.

5. A method of monitoring a receive array system having a reflector focussed on an array of antenna elements each feeding an individual signal channel characterised in that test or calibration signals are directed toward the array from one or more substantially point sources of signals located on or in the reflector.