Improving performance of non-duplexer active transceiver antenna with defected structures

The implementation of an active transceiver patch antenna without duplexer is reported. The isolation of the transmitting-receiving ports is increased by almost 20 dB by using defected ground structure patterns obtaining more than 50 dB; besides, cross-polarisation levels are also decreased by more than 15 dB. On the other hand, the use of spur lines allows increasing the linearity of the transmitting path, obtaining a low-harmonic distortion class E power amplifier. In the receiving path, a high-linear low noise amplifier (LNA) is employed with a third-order input intercept point close to 20 dBm. Both amplifiers are built with heterounion bipolar transistor (HBT). To prove the idea, as an example, the operation frequencies and channel separation of the GSM1800 were taken into account for a practical design. The complete active antenna is developed with characteristic impedances different from 50 Ω to obtain optimal performance of the active blocks.