The high precision time-modulated module based on differential control method

In order to meet the high-precision amplitude control requirements of the time-modulated module, a differential control method is proposed in this paper to change the generation of modulation sequence. By utilizing the characteristic of high precision time delay control of square wave signals output by FPGA, the phase difference between two square wave signals is used as the control signal, while the duty cycle of the square wave signals is kept unchanged. The two square wave signals are connected to the RF switches in series and logically run as “AND gate”. The amplitude of the module output signal can be controlled in high precise due to the turn-on time of the module has been improved to a high precise. A verification module for the proposed method is designed, manufactured and tested. By fully utilizing the logical relationship of different RF switches in differential control, the amplitude control precision is improved while the control line number is kept unchanged. The experimental results demonstrate that the verification module has excellent performance in the operating frequency band. With the differential control method, the module can achieve amplitude attenuation control with a step size of 0.25 dB and a dynamic range of 0–28.5 dB at 10 MHz modulation frequency, with an error range within ±(0.1 dB+1%AS).