A Novel Method to Acquire Circuit Transmission Characteristics by Noncontact Power Injection and Detection

To address problematic circuit transmission characteristics, test terminals are needed. In this study, an innovative method for determining the transmission characteristics of circuits by employing two semirigid coaxial probes with a T-shaped structure for signal injection and detection is developed. Initially, the proposed method can obtain circuit characteristics from 100 kHz to 10 GHz with a separation distance between the probes greater than 28 mm and a separation distance between the microstrip lines at the location of the injected and detected signals greater than 1.6 mm. Subsequently, an equivalent circuit model is proposed and validated through a 10 GHz measurement on a microstrip line, obtaining the root mean square error (RMSE) is 0.14 dB. Furthermore, the methodology is applied to measure the gain of a low-noise amplifier across frequencies from 100 MHz to 10 GHz. The maximum error is less than 1.66 dB, and the RMSE is 0.58 dB. Additionally, the transmission loss of parallel microstrip lines is investigated within the 3 GHz range, yielding the RMSE is 0.8 dB. The proposed approach enables precise testing of circuit transmission characteristics and facilitates the extraction of circuit equivalent parameters.