Research On Digital Transmitted Conformal Array Based On DDS

By combining the advantages of both conformal array antennas and phase-controlled array antenna, conformal phase-controlled array is able to perform fast half-spatial beam scanning. By combining digital array with conformal array, this paper proposes the concept of digital conformal phase-controlled array antenna and conduct analysis, design, synthesis and simulation on the new antenna system. The system includes two parts: DDS-based digital firing circuit and conformal array of 12 cylinders.First of all, a design and simulation is conducted of a double-layered micro-strip antenna unit and antenna units are miniaturized. Then, we analyze and synthesize conformal phase-controlled array of 12 cylinders with the use of projection analysis method, and get direction figures under the situations respectively with no scanning and under 20° and 40° scan. The Last but not the least, a stringent electromagnetic simulation in HFSS is performed on conformal phase-controlled array of 12 cylinder. The results are basically consistent to the results of synthesis, verifying the correctness of the synthesis approach.The digital firing circuit is consisted of four parts, namely a DDS signal generator module, a frequency source module, a power splitter module and a RF inverter module. The DDS signal generator module is implemented on AD9959 chip, and it mainly includes ARM controller, DDS chip, differential variable single end and low-pass filter. In the frequency source module, we use100 MHz high quality OCXO as reference frequency and output 2.8GHz and 500 MHz of microwave local vibrating signal through phase-locked loop technology, making phase noise respectively reach-112.1 dBc/Hz@1KHz and-116.1dBc/Hz@1KHz. And all power splitter module is formed by cascading two-stage or three-stage Wilkinson 1-2 splitters while the RF module is composed of RF mixers, RF amplifiers, band-pass filter and RF digitally controlled attenuator. After calibration for each channel, our circuit has an inconsistent amplitude no bigger than 0.3dB and an inconsistent phase no bigger than 3°.Lastly, we perform the experiment with conformal phased array for digital launch, by testing the direction maps under equal amplitude and same phase and-20 dB of low side lobe pencil beam pattern. By comparing the test outcome and the simulation results in HFSS, a relatively good consistency is found.