Study On Digital Phase Shifter At Ku-band

Phase shifter is the key component of phased array antenna. Antenna scanning speed and accuracy relate to the performance of phase shifter closely. It can be divided into two kinds analog and digital according to different control modes. Digital phase shifter is widely applied in mobile satellite communication system. The more bits of digital phase shifter, the more precise of beam control, but the difficulties of design phase shifter are bigger also. It will be very practical if good performance phase shifter is designed.This thesis focused on the Ku-band PIN diode controlling 6-bit microstrip digital phase shifter. Firstly, circuit structure, phase shifting principle, structure features and design method of common Loaded-Line, Switched-Line and Reflected phase shifter at Ku-band were deeply analyzed respectively, which provided theoretical bases for specific circuit structure choice of shift units. At the same time the equivalent circuits of PIN diode, the working principles of 3dB Branch Bridge and the structure of phase shifter auxiliary circuits were analyzed and simulated. Then design scheme of 6-bit phase shifter was determined according to requirements,5.625°,11.25°,22.5°and 45°small phase shift units used Loaded-Line phase shifters while the 90°and the 180°big phase shift units used Reflected and Switched-Line phase shifter respectively to enhance precision of phase shift and to reduce input Voltage Standing Wave Ratio (VSWR). After choosing the most suitable circuits, ADS 2008 design software was utilized to simulate every phase shifter according to the theoretical analysis and calculated results. Input and output ports were both matched to 50Ωloads. By fine-tuning and optimizing, insertion loss, input VSWR and phase shifting precision of phase shifters attained to demands. When every phase shifter met the design demands, concatenated them all and simulated.This thesis mainly introduced the realization and simulation of Ku-band 6-bit digital phase shifter on a substrate that dielectric constant is 2.2 and thickness is 0.254mm. Simulation results showed that the insertion loss was less than 2.6dB, the maximum of input VSWR was 1.35 and the phase deviations of 5.625°,11.25°,22.5°,45°and 90°were 1.228°,2.437°,3.692°,5.57°and 7.032°respectively in the working frequency range 11.7°12.2GHz. All parameters achieved target.