The Study Of Digital Array Antenna Transmitting Digital Beam Sweeping Technology

The newly developed Digital Array Radar (DAR) which combines digital technology with antenna technology adopts transmitting digital beam forming and receiving digital beam forming technology. The DAR's performance is unique when compared to traditional radar.The key component of DAR is Digital T/R Module. The paper focuses on its transmitting part which is LO generator, analog frequency synthesizer, power amplifier, digital waveform forming and digital control.The paper firstly discusses the basic principles of phase control of phased array and digital T/R module. After that the author designed an 8-channel C band transmitting beam forming system. The system comprises two parts: digital part and analog part. There are three schemes to carry out the DDS technology for the design of digital part, which is implementing DDS in FPGA, using single-channel DDS chip and multi-channel DDS chip. The paper adopts four-channel DDS chip AD9959. So the system needs two AD9959s. The control chip is Spartan-3 series FPGA. The communication with computer is through serial port. For analog part, the author designed a 4.75GHz PLL, a 600MHz PLL, a mixing circuit whose IF input is 200MHz generated by DDS, whose LO input is 4.75GHz generated by PLL, and whose RF output is 4.95GHz. Besides, there are filters and amplifiers in analog part.Then the author introduced the design of control software which is VHDL language design and MATLAB language design. Under the control of the software, the author tested the performance of the digital part and the whole system. The output signal's frequency, phase and amplitude of the digital part are controllable and the spectrum of the output signal of the system is given out.