| In recent years, with the rapid development of wireless communication technology, spectrum resources became tense accordingly. Because the structure and performance of the RF front-end system have a direct impact on the quality of the entire communication system, therefore, it plays a special role in the wireless communications transceiver. So the study of high-performance receiver becomes the key and difficult points for RF engineers.The working principle and structure of the digital radio was introduced in this thesis at first. We focus on the mainstream form of receiver’s architecture and its indicators and give a brief analysis of their advantages and disadvantages. Then focus on the elaboration and design of RF front-end circuits respectively. These circuits include low-noise preamplifier, filter and mixer module circuit. Finally, the RF front-end system was simulated.The NXP’s BUF760microwave transistors and the basic common-emitter configuration with the active bias network were used for LNA’s design. With the AC and DC simulation, stability analysis, noise analysis, input and output matching circuit, harmonic balance and gain compression simulation, the LNA gets the Noise figure less than2dB, gain greater than20dB and the P1dB is7.1dBm. Filter was designed by separation devices. The frequency response of the four filters was analyzed in this thesis. By comparison, we design a1.6dB Equiripple Chebyshev low-pass filter with bandwidth is30MHz and the return loss is26dB. At40MHz frequency the filter with20dB stopband rejection. Mixer circuit module use ADI’s AD8343mixer chip, with AC and DC analysis, stability analysis, input and output match, the mixer circuit has a conversion gain greater than3dB, noise figure less than11dB and the third-order inter-modulation is20dBm. Finally, by the simulation of system link budget, we get a RF front-end system with the gain of29dB, signal to noise ratio of78.995dB, spurious free dynamic range of68dB and the1dBcompression point is7.4dBm.which is meets the requirements of the RF front-end indicators. |
