| Analog phase shifter, an important part in microwave engineering, is widely applied in beam-forming networks, phased array radars, phase-modulated communication systems and intelligent broadband wireless mobile communication systems. This paper aims to design a small-sized reflection-type phase shifter with an over 360 degree phase-shift range and a constant insertion loss by adopting the Admittance Matrix theory. The main procedures are as follows:At first, this paper studied in detail the design principle of quadrature hybrid directional couplers. In view of the fact that the traditional even-odd mode analysis is confined to symmetric networks, this paper proposed a new network analysis method with the use of the admittance matrix, which was adoptedin the analysis of a lumped-element branch-line directional coupler with port impedance-transformation characteristics.In addition, this paper focused on the design principle of the reflection-type phase shifter with impedance-transformation characteristics and explored deep into its insertion loss and its phase-shift range. The results show that the insertion loss and phase-shift range of the phase shifter are proportional to the port impedance transformation ratio of the directional coupler. Therefore, in order to design a phase shifter with a wider phase-shift range and less insertion loss, it is better to choose an appropriate impedance transformation ratio.Finally, this paper simulated a 360 degree analog phase shifter under the frequency of 1 GHz by using the Agilent-ADS software. According to the simulation results, the return loss of the analog phase shifter is more than 10 dB with the bias voltage between 0-5.0V and under the frequency of 0.85GHz-1.1GHz, and the analog phase shifter achieves a continuous variable phase-shift range of more than 380 degree. The biggest insertion loss is less than-10dB in the whole frequency range and bias voltage range. The circuit area of the phase shifter is less than 80mm×80mm×1mm. |
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