Patent GB-1051038-A (GB)
IPC: H01Q25/00
Abstract: 1,051,038. Aerials; pulse radar. MITSUBISHI DENKI KABUSHIKI-KAISHA. May 28, 1963 [May 28, 1962], No. 21230/63. Headings H4A and H4D. An aerial system comprises at least two arrays each of which is characterized by having its elements disposed at intervals greater than one half wavelength and by having circuit means for introducing different predetermined phase differences between its elements, there being means for combining the said arrays through the said circuit means. Each array has a multilobed directional radiation pattern which is unique in the angular interval between lobes, and the effect of the predetermined phase differences between its elements is to cause a preselected lobe to coincide in direction with a pre-selected lobe of the pattern of each other array. As described, two arrays 10, 20, Fig. 1, comprise elements 11, 12 and 21, 22, respectively with spacings d 1  and d 2 , respectively, where d 1  and d 2  are each greater than a half wavelength. Circuit means 30a, 30b, 30c, 30d are provided in parallel for the array 10, and circuit means 40a, 40b, 40c, 40d in parallel for the array 20 and each pair, for example 30b and 40b, corresponds to coincidence in a particular direction, different from those for other pairs, of the preselected lobes of the arrays. Following the said circuit means are hybrid circuits, such as 50a, 60a for coupling the element pairs 11, 12 and 21, 22 to feeders from duploxers 70a, 80a. Each pair of duplexers is supplied by a transmitter, such as 90a, and their received powers are taken through a coincidence gate 100a and a switching circuit 120a to the input a of a receiver. A power differential gate 110a is also connected to the outputs of the duplexers 70a, 80a and controls the switching circuit 120a. A signal such as a radar echo is only passed to input a when (i) the responses of arrays 10 and 20 are simultaneous (gate 100a operates) and (ii) they are equal (gate 110a operates) and the effects of spurious signals are thus reduced. In a second embodiment the arrays are fed through phasing circuit means which are connected in series instead of in parallel (Fig. 2, not shown). A third embodiment (Fig. 3, not shown) is similar to the first embodiment except that the elements 11 and 21 are incorporated into a single element 11, and it may be adapted for passive direction finding only by removal of the duplexers and the transmitters (Fig. 4, not shown). In a further modification of the third embodiment (Fig. 5, not shown) a single transmitter 90 with duplexer 70 is connected directly to the centre element 11 and in a yet further modification (Fig. 6, not shown) variable phase shifting means 34, 44 are in addition connected directly to the outer elements 12, 22. Another embodiment, largely similar to the third embodiment, is equipped with beam shaping means (Fig. 7, not shown). Each hybrid circuit, such as 50a, is equipped to yield the difference D between the inputs A and B of the two halves of its associated array as well as their sum C. Both of these outputs C and D are supplied as inputs E and F to a beam shaping circuit 140a which so functions as to yield the input E as an output G only when the input F is smaller than preselected valve P. The effect is stated to be a substantial sharpening of the resultant lobes (Fig. 9, not shown). In a modification, the input E of the beam shaping circuit 140a is supplied directly from the half of the associated array (Fig. 8, not shown). The beam shaping circuit may, alternatively, be of the kind which yields an output G proportional to the quotient E/F of the two inputs only when the said quotient exceeds a preselected threshold value. A modification is also described in which phase differences between the elements of an array are obtained by means of mixers introduced into the paths of the signals from the appropriate elements, said mixers also receiving inputs of different phases from a common local oscillator (Fig. 10, not shown).