STUDY AND DESIGN OF ELECTRICAL BALANCED DUPLEXER

Abstract

It is practically very difficult to transmit and receive the signal at same frequency of carrier in wireless communication. The main cause in the operating over a same carrier frequency is, it is nearly impossible not to allow high power signal coming through the transmitter to penetrate into the low noise amplifier of the receiver. The power level of the signal coming from the transmitter is usually much stronger than what is being received by the receiver, because the signal is expected to face environmental losses. This kind of leakage is shown sharply in the below figure, where signals are flowing between antenna and transceiver. If the transmitted signal’s power is too high that means signal leaking into receiver is also has significant amplitude, the first stages of receiver which is analog will overload. That is why any such system require a thing which can isolate both transmitter and receiver. TDD and FDD is used basically separate uplink and downlink in time or frequency, respectively. In FDD systems, different frequency is used by transmitter and receiver. This allows separation by using frequency filters. As this system separates transmitter and receiver in either time or frequency, both cannot establish bidirectional link across single channel and that is why it is called half duplex.