Patent GB-1425144-A (GB)
Title: Array antenna for radiating doppler coded pattern using phase control
IPC: G01S1/40
Filed: 1974-02-15
Abstract: 1425144 Radio navigation; aerials HAZELTINE CORP 15 Feb 1974 [3 April 1973] 6898/74 Headings H4D and H4A An aerial system comprises an array of substantially parallel aerial element columns arranged with their centres along a predetermined path, said columns comprising one or more elements, and means for coupling wave energy signals thereto from a supply means. The system also comprises means for controlling the phase of the signals supplied to each of the columns, to produce phase reinforcement of the energy radiated by adjacent columns in a direction which continually changes during a period of time, no two pairs of adjacent columns having the same direction of phase reinforcement at any instant during said period. The system radiates with a desired radiation pattern into a region of space during the time period, and the frequency of the radiated energy is directionally-dependent. As described an aerial system comprises an aerial array of twenty-one waveguide columns 10, Fig. 1b, which are arranged in a circular arc of 180 degrees and each of which is provided with a plurality of radiating slots on its outwardly facing narrow wall (Fig. 1a, not shown). Other forms of radiating elements besides slots may be used, and there may be only one element in each column. A signal generator 12 supplies the array through a power divider 13, a variable phase shifter 15 being inserted in the transmission line 14 to each waveguide column. A control unit 16 provides phase control signals to the phase shifters during a predetermined time period, and there may be a succession of such time periods. With a linear variation of each phase shifter, and maintaining equal phase differences between them, as shown in Fig. 3, the effect is, that all adjacent pairs of columns radiate in different directions which continually change during the time period, but which make equal angles to tangents to the array at the associated pairs of columns at any instant during the time period (Figs. 2a, 2b, 2c, not shown). Considering a particular point in the far field, at the beginning of the time period, radiation might be directed thereto from the columns 10a, 10b (the first and second columns, counting clockwise). Later, during the time period, radiation might be directed to the point from the columns 10e, 10f (the fifth and sixth columns) and, still later, at the end of the time period, from the columns 10j, 10k (the tenth and eleventh columns). The phase slopes shown in Fig. 3 represent frequency shifts of the signals supplied to successive columns, each column after the first (10a) radiating at a higher frequency than the previous column. Each direction within an operating range, which may be, for example, 90 degrees, has a distinct set of columns from which signals in that direction originate and an associated unique average frequency of radiation by which it may be determined. As some columns of the array would be radiating in directions outside the operating range during part of the time period, they may then be disconnected, in order to save power. In another embodiment the radiating columns are arranged along a linear path and the signals supplied to no two pairs of columns simultaneously have the same phase relationship at any particular instant during the time period (Figs. 4a, 4b, not shown).