The Research Of Diplexer With Ultra Wideband And High Isolation

With the increase demand of the transmission rate in telecoms market, improving spectral efficiency becomes a hot area of research. Diplexer is a component that is absolutely necessary in frequency division duplex technology, and it plays an important role in frequency splitting. To design and develop diplexers with high performance, compact size, and low cost is a hot spot of demand in transmit and receive systems in RF and microwave area. To make the structure more compact, researchers have proposed diplexers with split ring resonators based on slow wave, fold coupling line, step impendence resonator, etc. The performance of diplexers directly determines the capacity of the whole communicating system. Diplexers with wider bandwidth and higher isolation can make better spectrum efficiency, to some extent, bring preferable user experience.In this essay, we mainly do research on diplexers and full duplex technology to improve spectral efficiency. Firstly, diplexers applied in communicating systems with ultra wide band and high isolation is studied. In working band 5 MHz to 1 GHz, 85 MHz and 105 MHz are settled as the split points. Measurements show that the insertion loss is better than 1 dB, isolation between the two paths is higher than 40 dB. At the same time, microstrip diplexers working at L-S band are also studied. After optimization, the measured result shows that in 1-3 GHz, the out-of-band rejection reaches to 30 dB. The worst isolation appears between two transmission bands, which levers at 27.4 dB. High performance of isolation is realized.Apart from frequency division duplex, full duplex which transmits and receives at the same time and same frequency is also learned. By the combination of phase shift and attenuation chips, a controlling circuit is fulfilled, which can cancel RF self-interference. A multi-path full duplex circuit is then designed and verified.