Microwave Planar Circuit Time Domain And Frequency Domain Testing Technology Research

Planar microwave circuits are more and more widely used in design of mi-crowave circuits and high-speed digital circuits, which makes the frequency limit of planar microwave circuits increase and meanwhile the size decrease. To fully under-stand planar microwave circuits, the characteristics of the circuits are needed to be acquired both from time domain and frequency domain. In this dissertation, some problems which are encountered when measuring planar microwave circuits both in time domain and frequency domain are studied.One way to obtain the behavior of planar microwave circuits is to implement measurements in time domain and frequency domain, respectively. Another way is using mathematical methods to transform the measurement results from one domain to the other. In this dissertation, the relationship of the measurement results in time domain and frequency domain are analyzed firstly. Then the Chirp-Z Transform and its inverse transform are selected to transform the measurement results in time domain to frequency domain, or vice versa. The relationship of time domain and frequency domain have ensured the possibilities of obtaining the characteristics of planar microwave circuits both in time domain and frequency domain especially when only one domain measurement results exist. To get smooth transform results, window functions are also discussed in this dissertation.When analyzing in time domain, the principle of the measurements for planar microwave circuits using TDR is introduced firstly. Then we focuse on the discussion of the multiple reflections in non-uniform planar microwave circuits. To compute and analyze the multiple reflections, a recursive algorithm is proposed. And based on this recursive method, the true impedance profiles of non-uniform planar mi-crowave circuits are reconstructed from their step response measured by TDR. To validate the multiple reflection computation algorithm and impedance reconstruc-tion algorithm, three non-uniform microstrip lines are designed and fabricated. The three microstrip lines are measured from 10 MHz to 20 GHz every 10 MHz. The corresponding step responses are obtained using inverse Chirp-Z Transform. The reconstructed impedance profiles of the microstrip lines illustrate the validity of the methods.When analyzing in frequency domain, the errors due to test fixtures in vector network analyzer measurement system are discussed. A 10-term error model of two- port vector network analyzer measurement system is proposed. According to the TRL calibration procedure, the closed-form solutions of the error terms are derived. The expressions of the error terms are based on S parameters. Meanwhile, the parameter X of calibration standards LINE andΓof REFLECT are also obtained. A simple but useful strategy is put forward to select the proper roots. To validate our algorithm, two sets of microstrip devices with via holes and a coplanar waveguide transmission line are fabricated and calibrated using the present TRL calibration method and the traditional algorithm, respectively. The magnitudes and phases of S11 and S21 of the devices are compared. The consistency of the de-embedded results with those calibrated by traditional TRL algorithm illustrates the validity of the TRL algorithm in this dissertation.