High Isolation Transmit/Receive Antenna System

Research is proposed to investigate the feasibility of a high-isolation transmit/receive antenna system for Army land vehicles, using an innovative, circuit-domain, distributed, RF-passive cancellation system with active feedback control. Conventional time- and frequency-domain cancellation approaches have inherently-narrow cancellation bandwidths due to applying amplitude and phase adjustments or fixed time delays to sampled signals, and often require electronics of prohibitively high cost. Spatial nulling approaches also suffer from bandwidth restrictions, in addition to their need for expensive RF circuitry, and their inability to cancel interference that has undergone spatial spreading, as would be caused by multi-path scattering on an Army vehicle. The proposed circuit-domain approach removes the cancellation bandwidth limitation by using variable true-time-delay lines and level controls. The proposed system uses wideband components to achieve the required, very wide operating frequency range of 20MHz to 6GHz, and can be built at low cost. The system features real-time optimization, with the ability to adjust cancellation settings in microseconds. Proof of feasibility will be assessed against a minimum cancellation threshold of 50dB.