The Reasearch And Design Of UWB Electronic Control Phase Shifter

Phase shifters are widely used in electronic countermeasure systems, measurement and test systems, especially phased array antenna radar systems. The phased array antenna radar systems always have great quality and large size, having inertial large mechanical scanning surface, making it difficult to detect the movement of the goal moving faster. The phased array antenna radar systems not have to mechanical move, spatial beams can be scanned by controlling the phase shift of the phase shifter to change the amount of the phase distribution of the antenna aperture. This paper focuses on discussing the ultra-wideband, 360° phase shifter, and controllable phase shifter.The phase shifter designed here contains two parts, UWB 3dB directional coupler and control circuit program. The UWB 3dB directional coupler divides the input signal into two orthogonal signals, and the control circuit program achieves phase shift in 360° by vector modulation chip controlled by microcontroller.First, the structural design of multi-layer microstrip directional coupler are discussed and gives a detailed correspondence curves between the size of microstrip lines and the odd even mode impedances. By using this relationship graphs, it’s very easily to design couplers with different orders or different couplings.Then single-section coupler design uses two different structures: rectangular structure and oval structure. These two different structures directional couplers with different couplings(2dB, 3dB, 4dB, 5dB) a total of eight couplers are designed and simulated, and then for analysis and comparison. The isolation and return loss of rectangular couplers is better than the elliptical structure couplers. The bandwidth of the elliptical structure couplers is wider than the rectangular couplers. Next, in order to increase the bandwidth, the 3dB three-order and five-order directional couplers with rectangular structure are designed and simulated. As the microstrip line of three-order and five-order coupler is so long, linear structure is not reality. In this paper, the coupling lines have been processed: the three-order couplers using semicircular structure and compact structure, and the five-order using surround structure. The measured amplitude imbalance of three-order coupler is less than 1.1dB, and phase imbalance is less than 90°±4.8° in 0.6~1.8GHz. The measured phase imbalance of five-order coupler is less than 90°±5.8° in 0.2~2GHz.Finally, the scheme of the phase shifter control circuit program is designed: by the microcontroller D/A function to control vector modulation chip to achieve the final phase shifter. The phase shifter can be tested as the 3dB directional coupler connected to the control circuit, given several phases tests of the phase shifter in 0.2~2GHz. The phase shift error are less than 9°、11.5°、14° respectively, when phase shift are 90°、180°、314°. The orthogonal signals have amplitude error and phase error, respectively, the magnitudes of the phase shift error caused by them are calculated in theoretical. Finally, this paper discussed a compensation method of the amplitude error, and proposes a change in microcontroller programming language software compensation scheme.