Broadband Digital T / R Module Receive Channel Key Technologies

The wideband digital array radar (WDAR), which accomplishes the transform between digital signal and analog signal in the radar array, is the trend of the development of the phased array radar and becomes a fully digital radar, attracting wide attention.Wideband digital array radar is a fully digitized array antenna radar, which employs wideband signal waveforms and uses digital beamforming technology in transmitting and receiving.With the development of high-speed sampling technology and digital signal processors, wideband radar signals can be dealed digitally.Wideband digital T/R module is one of the key technologies of wideband digital array radar and has become an important research direction.The concept of software radio was put forward in 1992. In recent years, remarkable progress has been made in this field, and it is widely knowleged and received enormous interest. The important idea of software radio is to make A/D converter as close to RF antenna as possible. Thus, the prevalent choice is to convert the digitalized analog IF signals to the baseband counterpart before digital signal processing in baseband.This kind of receiver is called digitalized IF receiver, which has become one of the most important parts in modern radar and communication systems.Firstly, the basic theory of signal sampling, Digital Down Conversion (DDC) and theoretical mathematical model of the software radio receiver is introduced. The Numerically Control Oscillator (NCO), integral decimation and digital filter design theory in DDC are emphasized.Secondly, after a brief overview of the digtal T/R module technologies, the dissertation presents a principle diagram of S band wideband digital T/R module including radio frequency(RF) module and digital module, and its work processes are introduced. Hardware structure of digital module and the design of receive channel are analyzed in detail, and the selection of the main devices and essentials are described.Thirdly, the structures of several common radar receivers and main technical indices are introduced. A principle diagram of RF module is proposed, and difficulties in system design are analysed with several solutions. Design principles of receiving channel and selection of the main devices are discussed in depth.Due to the specific demand in this project, then the digitalized IF receiver system is analysed, designed and simulated in Matlab, for the wideband and narrowband working modes, respectively.Finally,the designs and implementation of the DDC module in FPGA are discussed in detail, for the wideband and narrowband working modes, respectively. The proposed scheme and the system functions are verified in Matlab and Quartus II, along with the theoretical analysis.