Compact Wide Stopband Filters And Their Integration With Other Circuits

With the development of wireless communication, multi-frequency and multi-modes transmit-receive systems become more popular. Accepted signals usually contain various frequencies, which need to be separated. Therefore, miniaturization and wide stopband become basic requirements for filters, which are the important parts in communication systems. On the other hand, miniaturized terminal equipments require filter and related components to be more and more compact. Hence, high selectivity and miniaturized filters are important. This paper presents some circuits which focus on novel wide stopband, compact bandpass filters and its co-design with other components. The main work can be summarized as follows in three parts:1. Three filters using discriminating coupling scheme between feeding lines and resonators and low-temperature cofired ceramics (LTCC) technology with widestopband bandpass are designed. The first one is LTCC filter with third harmonic suppression. The second filter owns a wide stopband since the third and fifth harmonics are suppressed by the discriminating coupling. The third one is an oversized 60 GHz millimeter wave filter with the fundamental mode suppressed by the discriminating coupling. The last one is a wide stopband and high isolation diplexer based on discriminating coupling. All the circuits are firstly analyzed in theory and then simulated by software. Good agreement between the simulation and measurement results validates the proposed methods. These works have been accepted by IEEE Transactions on Components, Packaging and Manufacturing Technology and published in 2015 Asia-Pacific Conference on Antennas and Propagation.2. Crossover integrated with filtering function. In addition, we use such mode suppression method to analyze crossovers, which are usually used in antenna feeding network. We proposed co-design method to design filtering crossovers for circuit miniaturization. The first filtering crossover is designed with both transmission paths operating at the same frequency. The two paths maintain high isolation between each other. Based on the similar mechanism and design method, the second filtering crossover is designed with one path operating at certain frequency while the other working at different frequency. These works have been published in IEEE Microwave and Wireless Component Letters and 2015 Asia-Pacific Conference on Antennas and Propagation.3. Co-design between compact wide stopband filter and power amplifier. We use novel stepped impedance resonator (SIR) and feeding structure to design wide stopband cavity filter. Then, the cavity filter is integrated into class F power amplifier as a component of ouput matching network. Due to such co-design method, the class F power amplifier exhibits high efficiency with bandpass response.