A Non-Reciprocal, Ultrawideband Energy Selective Antenna Based on Conductivity Modulation Effect

This article presents a realization of nonreciprocal energy selective antenna (NESA) using conductivity modulation effect. NESA can protect sensitive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rx</i> frontend from high power microwave threats while permitting a normal transmission of wireless signals in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tx</i> channel. The proposed NESA consists of a transmission module, a rectifier circuit, and a ultrawideband antenna loaded with positive-intrinsic-negative (PIN) diodes. The transmission module discriminates the direction of guided wave and controls the rectifier circuit to select the modulation mode of PIN diodes. When NESA operates in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rx</i> state, PIN diodes are controlled by the dc conductance modulation, and it enters the defense mode at a lower threshold. Conversely, when operating in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tx</i> state, PIN diodes are controlled by radio frequency (RF) conductance modulation, NESA will not enter the defense mode and allow normal power transmission. To demonstrate this new concept, a design using a Vivaldi antenna is fabricated and measured. The theoretical, numerical, and experimental results agree well for the prototype antenna. The prototype operates in the frequency range of 2–6 GHz, allowing for the transmission of continuous wave signals up to 20 W, and providing ∼20 dB of defense level across the entire band. The prototype exhibits 25 dB of nonreciprocity and ∼ 1 dB of insertion loss in the normal mode. The added circuitry has a small size and requires no dc power supply, which is useful for protecting broadband front-ends and arrays.