Study On Key Technology Of Microwave Cavity Passive Components

Microwave cavity filters and power dividers, among other passive components, playeven more important roles in modern microwave communication systems, such aswireless communication systems, satellite communication systems, radar systems andelectronic count-warfare systems etc. The quality of these passive components has greatinfluence on the performance of the whole system. More and more efforts have beendevoted on the development on those components, with higher capability, smaller size,wider bandwidth, lower loss, higher power capacity, lighter weight and lower cost.Creative ideas, new theories, and novel structure of both filters and power dividers arerequired.This doctoral dissertation aims at solving some practical engineering problems usingnovel structure, new technique of passive cavity filters and millimeter waveguide powerdivider, with advantages such as high performance, wide bandwidth, small size, etc.The main contents of this dissertation are listed as follows:1. The principle on expanding bandwidth and reducing sizes of cavity filters havebeen studied. Then a novel structure of cavity filter has been provided based on theprinciple, with wide bandwidth, low loss and high power capacity.2. An ultra-wideband waveguide filter has been analyzed and a notchedultra-wideband bandpass filter based on new waveguide structure have been provided.the ultra-wideband waveguide filter is designed to satisfy the demand of U. S. FederalCommunications Commission based on the technique in presented in Chapter Ⅲ byfurther utilizing ridged waveguide and capacity-loaded structure. Moreover, notchedband ultra-wideband bandpass filter can be obtained by adding short-circuited stubs onan ultra-wideband band-pass filter. The filter possesses such characteristics as one ormore notches with flexible frequencies can be achieved, by setting the heights ornumbers of the posts in the short-circuited stubs.3. In order to further miniature filters, the coupling theory of electromagnetism isanalyzed deeply and a coaxial cavity filter with novel controllable mixed electric andmagnetic coupling is put forward by setting additional coupling structure to produce transmission zero, which can be changed by controlling the electrical coupling andmagnetic coupling, separately. The structure can realize quasi-elliptic function filterwithout using cross-coupled structure. By this technique, transmission zeros can berealized by linearly-positioned cavities. Furthermore, N-1transmission zeros can berealized by N cavities. Thus, quasi-elliptic function filters with good performance canbe realized from linearly positioned-cavities, leading to more compact structures.4. Network of millimeter waveguide power divider and power distribution networkare analyzed in detail. By using the designing methods of power divider reported beforeand analyzing the Riblet coupler, the power can be divided with any proportion in thetwo output ports. Because of the phase difference of90degree existed in the two outputports, it is hard to realize the same phase in the two output ports. By analyzing theworking principle of phase shifters, power dividers with equal phases and amplitudescan be realized in a certain bandwidth in the two channels by adding waveguides ofdifferent width and length to eahc channel. Besides, by cascading the structure together,ten channel two-layer power divider network with high performance is obtained whichpossesses equal phase and equal amplitude.Finally, a summary on this thesis is provided and the further work is proposed.