Two Improved Cancellation Techniques for Direct-Conversion Receivers

Figure 5

The voltage control phase shifter; when the phase-controlled voltage changes at 5.5 V~7.5 V, the electrical phase shifter adjusts a phase shift variation of ; taking into account the additional phase shift of the circulator and directional coupler itself, the phase control range of the voltage may also be larger than the theoretical results, which can meet the overall requirements of the circuit to compensate the phase shift. By carefully adjusting the control voltage , the exact 180° phase shift can be obtained between the transmitter port of the circulator and the cancellation signal.