The Research And Design Of Digital Handset RF Circuit

With the development of wireless communication, the traditional analog interphonehas been unable to meet demand, digital intercom, with its superior performance toreplace analog interphone become inevitable. This paper proposes a digital handsetRF circuit, analyzing its working principle. The main tasks are:1. Analyzing the super-heterodyne receiver, direct conversion (zero-IF) receivercircuit structure. Studies have shown that direct conversion receiver (zero-IF) circuitstructure due to intermediate frequency is zero, avoiding the mirror interferenceproblems, therefore saving the mirror suppression filter and intermediate frequencyfilter and reducing the circuit components is helpful to reduce the cost and theminiaturization of handset. For conversion receiver the existing of dc drift、flickernoise, even disorder, IO mismatch problems in the circuit structure, in-depthresearching is done, find out the ways and means to solve the problems. According tothe direct conversion (zero-IF) receiver circuit structure principle, designing thedigital handset rf receiving circuit, and the circuit simulating, testing and resultanalysis is done.2. Analysis the transmission circuit structure of rf circuit, focus on analysising andstudying the structure of rf power amplifier circuit, and discusses problems of rfpower amplifier efficiency and the ways and methods of improving the efficiency.Analysis results show that, the use of switch type rf power amplifier is an effectivemethod to improve efficiency, especially class F amplifier, the efficiency can reach100%theoretically. Try to introduced class F amplifier technology handset in class Famplifier, according to the working principle of class F amplifier, load line theory andLoadpull technology designing class F power amplifier,rf power amplifier circuit.And the circuit simulating, testing and result analysis is done.3. With the help of computer simulation software while designing, by S parametersand the harmonic balance simulation obtaining simulation amplifier, filterperformance parameters, determine the input and output matching network. 4. In the process of designing and producting, Using the rules of controlling ofelectromagnetic interference (EMI) in the design of every step, in order to get goodelectromagnetic compatibility (EMC).