Antenna Switch Production And Digital Feedforward Amplifier

There are two parts in this paper.In first part, a four-route antenna switch used in PAS system is introduced. The switch is acquired a low insertion loss and high isolation, so we have difficulty on making it meet the full specification and have some margin. First the design parameter is provided, then comparison and analysis of all kinds of components are made, last the simulation on HP-ADS explain the design result. Moreover, routing line and testing are also mentioned. During the practical designing, the accuracy of simulation is the key factor, so the model of components applied in the circuit must be accord with the actual condition. Of course, routing line on board is also important due to the area of board being small but the route so much. The testing result show the design spec can be meet basically. However, several result exceed the spec because of the imperfect routing line, which need improvement in the future.In second part, this paper introduces a new method for feedforward power amplifier. The third loop is added to the feedforward system which could detect the intermodulation directly, and additional pilot signal isn't necessary. The DSP system is used to control adaptively three loops and makes the feedforward system automatically to achieve optimum result. The paper firstly analyses the nonlinearity of RF power amplifier in theory, then puts forward the new self-adaptive feedforward method based on The DSP. EDA-tool ADS is applied to simulate the whole feedforward system, then discusses the intermodulation detection using the third loop and adaptive control using DSP in detail. According to the simulation result, the feasibility of this new feedforward method is verified.