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-- to obtain optimal performance of the active blocks.