Research On Microwave Capacitor Based On LTCC Technology

As an essential passive component in modern wireless communication system, the capacitor can have great influence on the performance of the system. In practical circuit system, it is always be used as bypass or decoupling functions. However, as the developing orientation of communication system, such as high integration and high speed, the performance of the capacitor should have the property of high frequency and miniaturization. Therefore, it is imperative to research on the performance of the microwave capacitor.This paper mainly analysis the equivalent circuit model of high frequency capacitor. It also researches the features of the capacitor including resonant frequency and Q, influenced by the physical model and connecting method. Furthermore, we pick up the equivalent circuit models. By using the LTCC(Low Temperature Co-fired Ceramic) technology, we manufacture high frequency microwave capacitors with different sizes. Moreover, we improve the drawback of the firing and metallization. Finally, we designed a TRL calibration system to improve the measurement accuracy. The main contents of this paper are as following:Firstly, the basic theory of microwave capacitor design is analyzed in detail, including the effective capacitance and the Q factors. It will provide directions for the circuit model of the capacitor. Then we propose two different equivalent circuit models. By analysing the capacitor loss, we find that it increases with the frequency. Therefore, it will deteriorate the Q factor for the purpose of increasing the operation frequency of the capacitor.Secondly, the capacitor model with the size of 0.5mm×0.5mm×0.2mm is created in HFSS. The influence on the resonant frequency with different connection topology is analysis. It can be found that the resonant frequency of the capacitor in the same side is nearly twice of the opposite side. In practice circuit, the capacitor is connected by using the gold wire. Therefore, we analyse the microwave performance of the gold wire and pick up the π type equivalent circuit model.As the capacitor works at high frequency, the measured results are seriously affected by the parasitic effect from SMA connector to the capacitor, finally. Thus, in or-der to improve the measurement precision, a TRL calibration is designed to eliminate measurement error caused by the parasitic effect from the SMA connector to the capacitor. Moreover, the microwave capacitors with different capacitances are manufactured by using the LTCC technology. Moreover, we solved the problem caused by firing and metallization. The capacitor will be measured accurately by the texture and the TRL calibration.