Abstract: An electromagnetic lens for a commutated scanning beam antenna has a plurality of petal-shaped parallel plate segments, connected in series, with the first petal-shaped segment adapted to receiver power at its input edge through an array of input probes connected, in a commutative switching arrangement, to a radio frequency transmitter. The last petal-shaped segment of the lens is formed into a radiating aperture or is connected to a linear array of radiating elements. Various techniques for determining petal shapes and for connecting together the petals are discussed. Stacked and folded lenses are described.

Abstract: A parallel plate geodesic lens aerial in the shape of a spherical cap or a flat disc, generates scanned planar radio beams. Commutated input signals to the lens are fed via output probes located around an arc of the perimeter of the lens to an arcuate array of radiating elements. The positional relationship between the power output from the lens and the power input to the array is 1:k, where k .noteq. 1. Dielectric-filled geodesic lenses, power level and scanned beam accuracy monitoring, and complex modulation of the input power to enable simpler aerials to be realized, are described.

Abstract: Determination of the pointing accuracy of a commutated scanning beam aerial is effected by monitoring the phase of the signal received at a point where, at all times during its operation, a field is established by the aerial. The phase of the sampled signal is observed by comparing it with a second signal which is sampled elsewhere in the field region or which is derived from the RF signal source of the aerial. This comparison can be effected by heterodyning the two signals. Pointing accuracy is determined by comparing the signal produced by the heterodyning with a pre-recorded signal typifying that experienced when the pointing error is zero. The technique is applicable to commutated torus aerials and to aerials incorporating a linear array of radiators to which power is supplied from a commutated array of excitation elements via an electromagnetic lens.