Design and Calibration of a 4 Channel Programmable Phase Shifter (2 − 6GHz)

Modern day high frequency phase shifters are often limited in bandwidth, as the phase delays implemented in classical phase shifter architectures are inherently frequency dependent. Furthermore, these phase shifters often lack in linearity and high phase resolution. In this paper a design is presented of a 4-channel phase shifter with high linearity and a simulated phase resolution of 2◦, with an operational frequency of 2GHz to 6GHz. The design overcomes the classical phase shifter issues of bandwidth limitations by opting for an In-phase-Quadrature (I-Q) addition architecture, of which components offer higher bandwidth capabilities. Implementation of 7-bit attenuators with a minimal attenuation step of 0.25dB allows the system to overcome systematic phase inaccuracies, after correct calibration. Notably, the model proposed in this work does not take into account any other inaccuracies besides the systematic phase and amplitude unbalance of the components. In case a better estimation of the path phase and amplitude discrepancies can be made, the more accurate estimation can be used in this work’s proposed calibration method. The theory behind this calibration is explained and can be used for different design situation of an I-Q based phase shifter. The dependence of maximum phase error and the minimal attenuation step of the system is mathematically estimated in this work, and using numerical analysis this relationship was proven to hold for all attenuation steps tested. In the case of this system’s attenuation step (0.25dB) the maximum phase error is ±0.87◦, regardless of the phase resolution.