A kind of flat transmission multi-mode resonant cavity
Technical field
The present invention relates to a kind of multimode cavity, specifically, relate to a kind of flat transmission multi-mode resonant cavity.
Background technology
Utilize multimode cavity, can constitute multi-mode filter.Because constituting the mode of operation of the resonant cavity of multi-mode filter is not the minimum basic mode of resonance frequency in this resonant cavity in general, the volume of the volume ratio basic mode resonant cavity of multimode cavity is big, and the Q value of this multimode cavity is higher than the Q value in the basic mode chamber of same resonance frequency.The multimode cavity that multi-mode filter adopts, have a plurality of mode of operations to exist simultaneously in same resonant cavity, these patterns intercouple to produce to produce than the cross-couplings between the different single mode cavitys of the general filter that is made of the single mode resonant cavity zero point and more can realize easily zero point.The multi-mode filter that is made of multimode cavity produces zero point owing to realizing easily that multimode is coupled in the same resonant cavity, satisfying under the condition of same technical indicator, the number of the needed cavity of multi-mode filter is than there not being cross-linked common single mode filter to lack.More than two factors make the Insertion Loss of multi-mode filter more much smaller than the Insertion Loss of single mode filter, and the volume of filter is also reduced.
The patent application that number of patent application is 200710050788.7, name is called " a kind of compact multimode cavity " discloses a kind of multimode cavity that is used to constitute the multimode resonance filter, this compact multimode cavity mainly can encourage cavity, coupled structure and the electric field metallic object of a plurality of mode of operations to form by one, and the electric field metallic object only is connected with cavity inner wall in one direction.This multimode cavity can reduce the volume of resonant cavity, has solved parasitism band between filter, duplexer, the multiplexer topic of corresponding well, has good frequency selective characteristic simultaneously.
But there are a plurality of mode of operations in above-mentioned multimode cavity and compact multimode cavity.These mode of operations are different with extraneous stiffness of coupling.In order to realize that very precipitous band suppresses outward, a little less than other mode of operation of coupling ratio in one of them mode of operation and the external world, loaded Q is higher.Because constituting the actual metal material of resonant cavity is non-perfact conductor, the mode of operation of this high Q value is big to the loss of microwave to other mode of operation of loss ratio of microwave; When such multimode cavity constitutes band pass filter, the transmission coefficient of filter particularly at the edge of passband near transmission zero, " pit " will occur in passband, cause the passband fluctuation of filter transmission coefficient bigger, the result of use of filter is brought very big influence.
Summary of the invention
The purpose of this invention is to provide a kind of flat transmission multi-mode resonant cavity, overcome deficiency of the prior art.
To achieve these goals, the technical solution used in the present invention is:
A kind of flat transmission multi-mode resonant cavity comprises cavity and coupled structure that at least one can encourage a plurality of mode of operations, it is characterized in that described cavity is provided with microwave-absorbing body.
Described microwave-absorbing body is arranged on the upper cover plate of cavity.
Described inside cavity electric field strength maximum is provided with the electric field metal column, and described microwave-absorbing body is arranged on the cavity upper cover plate directly over the electric field metal column.
Described microwave-absorbing body passes the upper cover plate of cavity from outside to inside.
Described microwave-absorbing body is provided with the lossy microwave layer of being made by microwave absorbing material, and described lossy microwave layer is arranged at the surperficial or inner of microwave-absorbing body.
Also be provided with tuning screw on the described cavity upper cover plate.
Principle of the present invention: the mode of operation in the multimode cavity is owing to different with the stiffness of coupling in the external world, to the decay difference of microwave.The pattern strong with external world's coupling is little to the decay of microwave.And it is big with the weak pattern of external world coupling to the decay of microwave.By a microwave-absorbing body is set on the cavity upper cover plate, can increase those and the extraneous decay of strong mode of operation that be coupled selectively to microwave, make all mode of operations have identical or close decay, thereby make the interior transmission of band of filter smooth microwave.
Described cavity is a column construction, and the above and below is a parallel plane; Electric field metallic object and vertical connection of cavity lower plane inwall.For easy to process, the cavity level cross-sectionn can be designed to rectangle.Can certainly be circle, ellipse etc.
Described microwave-absorbing body be arranged at certain mode of operation electric field in the resonant cavity concentrate the place directly over upper cover plate on.The surface of microwave-absorbing body is provided with microwave absorbing material, and this microwave absorbing material can add in any form.The adding of microwave absorbing material has realized that the passband fluctuation in the passband is tending towards smooth.
The cavity upper cover plate can also be provided with tuning screw, simultaneously, also microwave-absorbing body can be set on tuning screw.
The present invention is simple and practical, can solve the bigger problem of passband fluctuation in the prior art well.
Description of drawings
Fig. 1 is for the prior art constructions schematic diagram.
Fig. 2 is a kind of structural representation of the present invention.
Fig. 3 is an another kind of structural representation of the present invention.
The name of label correspondence is called in the accompanying drawing: 1-cavity, 2-electric field metallic object, 3-microwave-absorbing body, 4-lossy microwave layer, 5-tuning screw.
Embodiment
Embodiment 1
As shown in Figure 2, a kind of flat transmission multi-mode resonant cavity comprises the cavity 1 and a coupled structure that can encourage two mode of operations, and the electric field metal column 2 that is arranged at cavity 1 inside, and wherein, described cavity 1 upper cover plate is provided with microwave-absorbing body 3.
This microwave-absorbing body 3 is a screw-like, be arranged at electric field metallic object 2 directly over, and pass cavity 1 upper cover plate from outside to inside.The surface of microwave-absorbing body 3 or inside are provided with lossy microwave layer 4, and lossy microwave layer 4 is made by nonmetal consumable material, are used to increase the loss of the stronger pattern of coupling, make whole cavity 1 inner passband fluctuation smooth.
Embodiment 2
As shown in Figure 3, embodiment 2 is do not have electric field metal column 2 in the cavity 1 of described smooth multimode cavity with the difference of embodiment 1, and other structures are all identical.