Microwave Signal Replicator Design for Testing of the Multi-Channel Transcranial Magnetic Stimulator

The multi-channel transcranial magnetic stimulator is commonly used for rehabilitation treatment of ischemic cerebrovascular disease, neurosis, and brain injury diseases in the elderly. And multiple high coherency signals are required as inputs for its test, which are with consistent frequency, adjustable amplitude, equal magnitude, and long-time phase consistency $⩽$±1°. But ordinary signal sources have only one output channel, which is far from meeting the test requirements. If the traditional power division is used for the duplication, the phase difference between the channels will be larger than ±1°. If the multi-throw Radio Frequency (RF) switch is used, it will seriously affect the phase consistency of the input signal and increase the distortion of the signal. In order to solve the above problems, the method to extend the output of the microwave signal source has been proposed in the paper by using the integrated transceiver AD9361. The proposed method can realize the duplication of the number of signal channels according to user requirements. Then a signal replicator has been designed by combining AD9361 chip and Field-Programmable Gate Array (FPGA) control module. The experimental platform has been built to test the performance of the designed device. Experimental results show that the duplicated signals are highly consistent with the source signal in the power amplitude and frequency, meanwhile the phase of the duplicated signals are all highly consistent with each other.