Design And Implementation Of Digital IF Circuit In High Performance Communication Transceiver

As China gradually enters into4G era,4G-related equipment demand is growing rapidly, demand for4G communication terminal test equipment is also very large. The characteristics of LTE signal are high-frequency and high-bandwidth, which puts forward higher requirements for communication terminal test equipment. The frequency and bandwidth of most communication terminal test equipment currently support can not fully meet the requirements of LTE, therefore, a communication terminal test equipment supporting high frequency range, high bandwidth will has a very big market.High performance communication transceiver is a major part of communication test instrument, and plays a decisive role in supported frequency range and bandwidth of communication test instrument. High performance communication transceiver mainly consists of radio module, digital IF module, baseband module, and main CPU. Among them, digital IF circuit is mainly used to implement the conversion between analog IF signal and digital baseband signal as well as the high-speed communication interface with the baseband board and main CPU.It is of great importance to the performance of communication transceiver.The main design challenges of digital IF circuit are high-bandwidth digital IF receiver link design,transmitter link design,and FPGA circuit design, including receiver filters, amplifiers, ADC design and transmitter filter, DAC design and related clock, power supply design.The main content of this article is the design and implementation of digital IF circuit in high performance communication transceiver. After introducing the background and significance of the subject, it describes the design principles of digital IF circuit including receiver, transmitter design principles and the overall design framework.Then it describes the schematic and PCB design of digital IF circuit, discusses every module such as FPGA, receiver link, transmitter link, clock networks, and other detailed circuit design and design cautions.Then it presents the testing results and measured data of every module.Finally it describes digital IF circuit production self-test procedure in detail from two aspects:board self-test program and interface self-test program.The digital IF board discussed in this article has met or exceeded all design requirements and targets, and has completed production process, and is going to be used in real communication test equipment.It has a certain practical significance and value to the realization of4G communication test equipment.