No abstract

Abstract-A novel method for a dual-band filter and quad-channel diplexer design is presented in this paper. This method, by altering the gap between resonators, realizes a transformation from bandpass to dual-band for the filter and diplexer. At first, a high selectivity bandpass filter (BPF) with four controllable transmission zeros (TZs) is designed. Then altering the gap between resonators, a band gap is generated and utilized to split the passband of the proposed BPF into two bands, which transform the BPF to a dual-band filter with a narrow passband separation. The center frequency and bandwidth of the new dual-band filter are controllable by adjusting the frequency and width of the band gap. Based on the dual-band filter, a quad-channel diplexer with stepped impedance T-junction is designed, and it can be transformed to a wideband diplexer. For demonstration, the dual-band filter and quad-channel diplexer are fabricated and measured.

In the ultrasonic gas temperature measurement system, the principle is that the velocity of sound in gas is a function of temperature. But because the propagation speed of ultrasonic wave can be easily affected by humidity, the accuracy of the gas temperature measurement will be affected too. This dissertation will implement the ultrasonic gas temperature measurement system with humidity correction suitable for all kinds of environment humidity. This type of ultrasonic technique is a highly efficient algorithm with the advantages of both time-of-flight method and phase shift method. And the system is realized with a single-chip microcomputer-based with a relative humidity/water vapor pressure meter. The main advantages of this ultrasonic temperature measurement system are high resolution, using narrow-bandwidth ultrasonic transducer of low cost and ease of implementation.

Abstract-We present a revised Cauchy method to accurately extract the high quality factor of dielectric resonators from measurements. Since the losses displace all the zeros and poles of the transfer function horizontally to the left in the complex plane, the accurate evaluation of the unloaded quality factor of microwave resonators can be achieved based on the complex frequency transformation. The results show that if the three-point method is employed, the accuracy of the quality factor values deteriorates when the input/output coupling is strong. Nevertheless, a nearly constant factor value can be obtained by our proposed technique whether the input/output couplings are weak or strong. This algorithm provides an alternative method to measure the unloaded quality factor when the signal-tonoise ratio is high.

No abstract