The Research And Design Of Digital Radio Based On ADF7021-V

In the so called "information age", wireless communications plays a very important role in social life, cell phone,which was once the symbol of status, also becomes the basic part of normal people’s life. Compared with the mobile communication, prominent advantages of radio communication is the cheaper price. Because a third party operators participation is not needed, radio communication nearly do not produce any cost, in addition, it can realize one-to-one or one-to-more calls easily. Usually a call distance can reach3km above. Based on the above advantages, radio in the civilian and military fields attracts many customers, and is playing the more and more important role in People’s Daily life and national defence construction.Along with the development of special mobile communication technology, radio communication is developing from analog to digital technology gradually.Compared with analog interphone, digital radio spectrum is high efficiency and good quality with long call communication, etc.This paper studies the key techniques of the digital radio and the structure of the functional modules in the current mainstream market,and analyzes the working principle of the main modules. With the new RF transceiver ADF7021-V as the main RF processing chip,this paper introduces a kind of digital radio design that can be used for short distance communication. In this design, the receiver is based on the low IF structure. Compared with the traditional receiver and the common specialized superheterodyne type structure, the receiver of this design has the very good mirror suppression characteristics.Besides,the low IF structure dose not need the expensive image inhibit filter, which will save the cost. The transmitter of this design is based the Direct Quadrature-up Conversion(DQUC) structure. And the Local Oscillator signal is worked in two times of RF frequency, which not only save design cost, but also solves the spill caused the direct current system performance deterioration. This system’s RF frontend mainly relies on ADF7021-V,considering to the performance, complemented with LNA unit, and the micro controller chip adopts STM32F103C8, and the audio processing part is based on vocoder CMX618. ADF7021-V uses the external VCO as a local oscillating signal, and the system uses MAX2620to design pressure controlled oscillator.