A quasi-optical receiver with angle diversity

Quasi-optical transmit/receive front ends

“…The lens is fed by its center elements, which does not contribute directly to the combined output power. [7]. Fig.…”

“…It has been shown that this architecture also reduces the effects of multipath fading since the lens has built-in angle diversity. For example, if three receivers are placed along a focal arc of a lens in reception, in [7] each of the receivers preferentially receives a signal from one incident direction. This means that in a standard slow-fading communication channel [20], it is unlikely that incoming signals would simultaneously destructively interfere at all three receivers.…”

“…Three received IF signals in a receiver with angle diversity. The three signals are measured at three mixers positioned along a focal arc, as a carrier source is moved in the far field [7]. was rotated through a set of angles.…”

“…For many T/R applications, adaptive beamforming is either required or could offer substantial improvements. The QO approach, in particular the lens amplifiers, can be used to perform a part of the adaptive signal processing at the analog front end without additional hardware, as has been crudely demonstrated in [7]. A more advanced study is required to demonstrate the usefulness of this concept.…”

“…A few researchers have demonstrated powercombining arrays that include some functionality. For example, a grid oscillator was characterized as a self-oscillating harmonic and subharmonic mixer, and several such identical mixers were used in a diversity receiver where the front end was a QO lens amplifier array [7]. Furthermore, two different phase-shifterless beam-steering schemes have been demonstrated: an oscillator linear steering array using voltagecontrolled oscillators (VCO's) to detune end elements of a self-injection locked array to produce a progressive phase shift across it in one dimension [8]; and using antenna arrays with integrated lensing, similar to Rotman lenses [9].…”