This paper proposes EM mechanism to improve the isolation between transmitting and receiving array antennas using metamaterial EM band gap (MTM-EBG). The proposed mechanism can be applied to full-duplex array antenna system with very closely spaced arrays (0.33λ0) with no degradation in radiation pattern. Using the proposed technique the isolation is shown to improve by >30 dB in an antenna array consisting of three-element microstrip patches designed to operate across 9.7 to 12.3 GHz. Parametric analysis was used to optimise the decoupling arrays performances. The proposed antenna array has physical dimensions of 65×22.5×1.6 mm 3 and an electrical size of 2.16 ×0.75 ×0.053 , where is free space-wavelength at mid-band of 10 GHz.

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A recently presented implementation of the current‐reuse concept, specifically devised for microwave cascaded single‐ended amplifiers, is applied to the design of a three‐stage medium‐power low‐noise amplifier (LNA) operating in X‐band. The LNA is realized on a GaN‐on‐SiC 0.25 µm technology supplied by Leonardo S.p.A.'s internal foundry and achieves a transducer gain (GT) of 24 dB, a noise figure (NF) better than 2.5 dB and an output power at 1 dB gain compression (Pout,1dB) higher than 20 dBm over the whole X‐band. The first two stages of the LNA are stacked and share the same current while requiring, as a pair, a doubled external supply voltage, which corresponds to that of the third, medium‐power stage. The versatility of the adopted current‐reuse concept is exemplified by the fact that the two low‐noise stages are initially designed in a conventional single‐ended topology: only in a second step are they converted into a current‐sharing stage pair with no significant effect on RF performance. Nonconventional approaches to low‐noise design and small‐signal stability analysis developed by the Authors and adopted in this design are referred to the Reader.