GB1385905A - Aerial arrangements - Google Patents

Abstract

1385905 Aerials; Doppler radar EMI Ltd 17 May 1972 [28 April 1971] 11752/71 Headings H4A and H4D In an aerial arrangement having transmitting and receiving aerials which are coupled to Doppler radar means, each aerial comprises at least one resonant slot in a conductive layer on one side of a sheet of dielectric material, and components of the Doppler radar means are formed as patterns of microstrip conductors on the other side of said sheet. One of said microstrip conductors is disposed transversely to the centre line of each slot, and is terminated in one direction beyond said slot, to effect electromagnetic coupling. Impedance matching may be obtained by moving a said microstrip conductor in a direction which is parallel to the centre line of its associated slot. As described, an arrangement comprises a transmission aerial array of four slots 5, Fig. 7, which are formed in a ground plane conductor on the lower face of a dielectric substrate 1, and which are fed cophasally from a strip conductor 3 by limbs 4 on the upper face of said substrate. The arrangement also comprises a similar receiving aerial array of four slots 6. The strip conductor 3 is continued by strip conductors 20, 19 to a quarter-wave Gunn-effect diode source line resonator 27, which receives power from a conductive pad 30. The receiving array is connected through a microstrip filter 13 to a coupling device B, which also receives power from the diode source 27. Output from the device B is coupled to a mixer diode 22, which receives bias from a pad 28 via a strip 23. Output at Doppler frequency is available at a conductive pad 29. Tuning adjustment of the oscillator may be achieved by mechanical abrasion of circuit strips, or by proximity effect means. Various constructions of the coupling device B are described, associated with either one or two mixer diodes (Figs. 3 to 6, not shown). The shape of the radiation diagram of an array of slots of the kind described may be modified by suitably locating the slots in the ground plane (Figs. 2(a) 2(e), not shown), and a conducting reflector plate may be provided near the substrate 1.