Disclosure of Invention
The invention aims to realize a duplex filter based on a TE103 waveguide mode, and provides a duplex filter which has the outstanding advantages of simple structure, low processing complexity, small influence of assembly errors on technical indexes and the like and simultaneously solves the contradiction requirement of in-band insertion loss and out-of-band high attenuation aiming at the high requirement of the existing microwave millimeter wave communication system. Due to the simple structure, the reliability of the device is improved, the related higher requirements of the microwave millimeter wave communication system can be effectively met, and the device has wide application prospect in the microwave millimeter wave communication system.
The invention relates to a duplex filter based on a TE103 waveguide mode, which comprises a main cavity body 1 and a cover plate 20, wherein the cover plate covers the main cavity body to form a waveguide cavity body. A common waveguide port 18 is formed in the center of the cover plate; the central position of the main cavity is provided with a step 2, and the step 2 is positioned at the projection position of the common waveguide port 18 on the main cavity;
the main cavity is divided into a high-frequency cavity and a low-frequency cavity; the high-frequency cavity and the low-frequency cavity are distributed in two sides relative to a straight line L1; the high-frequency cavity and the low-frequency cavity are coupled through a common coupling window, the step 2 is arranged in the common coupling window, the center line of the common coupling window is a straight line L1, and the projection of the center line L2 of the step 2 in the length direction of the common coupling window is superposed with the straight line L1;
for a high frequency cavity:
from left to right, a high-frequency band waveguide port 9, a high-frequency TE103 mode cross coupling window 7, a high-frequency TE103 mode coupling window 8 and a high-frequency TE103 mode resonant cavity 6 are arranged in sequence;
the cavity structure of the high-frequency cavity is as follows: the two cavities are in a shape like a Chinese character 'yi', namely a left cavity in a shape like a Chinese character 'yi' and a right cavity in a shape like a Chinese character 'yi' and are arranged above the two cavities in a shape like a Chinese character 'yi';
the left side of the left U-shaped cavity is coupled with the high-frequency band waveguide port 9; the left side of the left I-shaped cavity is coupled to the left side of the left U-shaped cavity through a coupling hole, and a cross coupling window 7 of a TE103 mode is arranged beside the coupling hole; the right side of the left I-shaped cavity is coupled to the right side of the left U-shaped cavity through a coupling hole, and the coupling hole is a high-frequency TE103 mode coupling window 8;
the connecting edges of the left U-shaped cavity and the right U-shaped cavity respectively extend into the two linear cavities, a coupling hole is formed between the connecting edges and the top edges of the two linear cavities, and the cavity between the coupling hole and the right side of the right linear cavity is the high-frequency TE103 mode resonant cavity 6;
the right side of the right U-shaped cavity is coupled to the public coupling window, and the right side of the right I-shaped cavity is coupled to the right side of the right U-shaped cavity through the coupling hole;
tuning threaded holes penetrating through the main cavity are formed in the side surfaces of the linear cavities, the U-shaped cavities and the coupling holes;
for low frequency cavities:
from right to left are a low-band waveguide port 10, a low-frequency TE103 mode cross-coupling window 5, a low-frequency TE103 mode coupling window 4, and a low-frequency TE103 mode resonator 3 in this order.
Further, the common waveguide port 18 is a standard BJ320 waveguide port; the high-band waveguide port 9 is a BJ320 high-band waveguide port; the low band waveguide port 10 is a BJ320 low band waveguide port.
Further, the common waveguide port 18 is a common waveguide T-junction.
The invention utilizes the characteristic that the high Q value of the resonant cavity of the waveguide TE103 mode can generate good pass band insertion loss in the waveguide filter, and simultaneously adds the cross coupling structure of the resonant cavity to improve the pass band isolation of high and low ends. In the aspect of structure, due to the fact that machining is convenient, the influence of assembly on performance indexes can be almost ignored, technical indexes are excellent, and the like, the method is also a prominent advantage of the method.
Detailed Description
The invention provides a duplex filter based on a TE103 waveguide mode, and belongs to the field of microwave and millimeter wave communication. The method mainly utilizes the characteristics of the TE103 waveguide mode to solve the problem that the single-cavity resonance Q value of the conventional waveguide duplex filter is relatively small, and brings the results of low loss and high out-of-band attenuation.
The invention is further described with reference to the following detailed description of embodiments in conjunction with the accompanying drawings:
referring to fig. 7, a duplex filter based on the TE103 waveguide mode includes a main cavity 1 and a cover plate 20, and the cover plate covers the main cavity to form a waveguide cavity. Referring to fig. 4-7, a common waveguide port 18 is formed in the center of the cover plate; referring to fig. 1-3, a step 2 is arranged at the central position of the main cavity, and the step 2 is arranged at the projection position of the common waveguide port 18 on the main cavity;
with further reference to fig. 3, the main cavity is divided into a high frequency cavity and a low frequency cavity; the high-frequency cavity and the low-frequency cavity are of a two-sided structure about a straight line L1; the high-frequency cavity and the low-frequency cavity are coupled through a common coupling window, the step 2 is arranged in the common coupling window, the center line of the common coupling window is a straight line L1, and the projection of the center line L2 of the step 2 in the length direction of the common coupling window is superposed with the straight line L1;
for a high frequency cavity:
from left to right, a high-frequency band waveguide port 9, a high-frequency TE103 mode cross coupling window 7, a high-frequency TE103 mode coupling window 8 and a high-frequency TE103 mode resonant cavity 6 are arranged in sequence;
the cavity structure of the high-frequency cavity is as follows: the two cavities are in a shape like a Chinese character 'yi', namely a left cavity in a shape like a Chinese character 'yi' and a right cavity in a shape like a Chinese character 'yi' and are arranged above the two cavities in a shape like a Chinese character 'yi';
the left side of the left U-shaped cavity is coupled with the high-frequency band waveguide port 9; the left side of the left I-shaped cavity is coupled to the left side of the left U-shaped cavity through a coupling hole, and a cross coupling window 7 of a TE103 mode is arranged beside the coupling hole; the right side of the left I-shaped cavity is coupled to the right side of the left U-shaped cavity through a coupling hole, and the coupling hole is a high-frequency TE103 mode coupling window 8;
the connecting edges of the left U-shaped cavity and the right U-shaped cavity respectively extend into the two linear cavities, a coupling hole is formed between the connecting edges and the top edges of the two linear cavities, and the cavity between the coupling hole and the right side of the right linear cavity is the high-frequency TE103 mode resonant cavity 6;
the right side of the right U-shaped cavity is coupled to the public coupling window, and the right side of the right I-shaped cavity is coupled to the right side of the right U-shaped cavity through the coupling hole;
tuning threaded holes penetrating through the main cavity are formed in the side surfaces of the linear cavities, the U-shaped cavities and the coupling holes;
for low frequency cavities:
from right to left are a low-band waveguide port 10, a low-frequency TE103 mode cross-coupling window 5, a low-frequency TE103 mode coupling window 4, and a low-frequency TE103 mode resonator 3 in this order.
Further, the common waveguide port 18 is a standard BJ320 waveguide port; the high-band waveguide port 9 is a BJ320 high-band waveguide port; the low band waveguide port 10 is a BJ320 low band waveguide port.
Further, with reference to fig. 4, the common waveguide port 18 is a common waveguide T-junction.
Referring to fig. 1 to 7, the principle of the duplex filter based on the TE103 waveguide mode in this embodiment includes a common standard BJ320 waveguide port 18, a standard BJ320 high-band waveguide port 9, a standard BJ320 low-band waveguide port 10, high-low end TE103 mode resonators 3 and 6, high-low end TE103 mode coupling windows 4 and 8, high-low frequency TE103 mode cross-coupling windows 5 and 7, a common waveguide T-shaped connector 18, a main cavity cover plate 20, tuning screw holes 11, 12, 13, and 14, and the like.
The high-frequency and low-frequency TE103 mode resonant cavity is the core part of the duplex filter of the waveguide mode, and is also the key part of the high Q value of the single cavity of the duplex filter of the TE103 waveguide mode, and directly determines the pass-band insertion loss of the duplex filter of the TE103 waveguide mode. According to the related theory, the definition of the Q value of a single cavity is the ratio of the energy storage to the energy consumption of the cavity. Because the TE103 mode of the waveguide is utilized, the volume of the resonant cavities 3 and 6 is 3 times of that of a conventional single cavity theoretically, and thus the energy storage capacity of the cavity is approximately 3 times of that of the conventional cavity, so that the energy storage capacity of the TE103 mode is quite large, and the energy consumption difference between the TE103 mode and the conventional mode is very small. Therefore, the insertion loss of the waveguide filter designed in TE103 mode can be greatly reduced. Due to the duplex filter, the high and low ends are at different frequencies, with a slight difference in frequency, so that the resonant cavities at the high and low ends differ in size to ensure that the respective resonant frequencies are within the desired range. The TE103 modes discussed above are for the respective resonators.
Besides the important resonant cavity of the TE103 mode, the duplex filter based on the TE103 waveguide mode has another structural form which has a larger influence on the isolation of the high-end and low-end channels, that is, the cross-coupling window 5, 7 structure. From the basic knowledge of the filter, it can be known that, in general, the more resonators 3 and 6 of the filter, the greater the attenuation outside the band, but this is a contradictory matter with the insertion loss inside the band, and the more resonators and the greater the insertion loss inside the band, so the use of TE103 mode can compensate this deficiency. To improve the out-of-band attenuation, a very efficient approach is taken to the cell cross-coupling window 5, 7 structure.
The duplex filter of the TE103 waveguide mode mainly utilizes the phase and amplitude relation of a certain out-of-band frequency after the cross coupling windowing of the separate cells, and if the out-of-band attenuation is counteracted as much as possible due to ideal effect, the phase difference of 180 degrees and the amplitude are required to be the same. For a duplex filter based on a TE103 waveguide mode, the main out-of-band attenuation is the mutual isolation of a high-end frequency and a low-end frequency, and cross coupling is generated to perform respective attenuation on the high-end frequency and the low-end frequency, so that the attenuation of the cross coupling has relative high and low side frequencies, for the high-end passband of the duplex filter based on the TE103 waveguide mode, the low-end passband frequency needs to be attenuated, and capacitive cross coupling forms are arranged in cross coupling window structures 5 and 7; for the low-end pass band of the duplex filter of the TE103 waveguide mode, it is the high-end pass band frequency that needs to be attenuated, and an inductive cross-coupling form is set in the cross-coupling. The methods are equivalent to additionally introducing out-of-band attenuation except for the out-of-band attenuation of the filter formed by the TE103 mode resonant cavities 3 and 6, so that the passband isolation of the duplex filter of the TE103 waveguide mode is increased without remarkably increasing the in-band insertion loss.
The above mainly describes the TE103 mode resonant cavities 3, 6, the cell cross coupling windows 5, 7 structures, etc. in the main constitution of the duplex filter based on the TE103 waveguide mode of the present invention, in addition to which there is a waveguide T-type connector 18, the function of this connector is to connect the filters of high and low ends into a duplexer with required characteristics, which is one of the key parts for realizing the duplexer, and the structure of this part is designed as a key part for optimizing the duplexer index. The basic working principle of the high-frequency-band filter is that a common end can input and output signals in a high-low end frequency range, and two branch channels respectively correspond to a frequency passband of a high-end filter and a frequency passband of a low-end filter. The waveguide T-shaped joint 18 is provided with a concave step 2 at the center, and the step 2 has the following functions: the method comprises the steps of matching a public port, eliminating the influence of a waveguide high-order mode, and effectively distributing the frequency pass bands of high and low ends. The high and low ends of the waveguide T-junction 18 typically have a section of standard waveguide corresponding to the high and low end filters of the TE103 waveguide mode, respectively, thus forming an integral duplex filter.
Referring to fig. 3 and 4, the invention integrates the resonant cavities 3 and 6, the coupling windows 4 and 8, the cross-coupling windows 5 and 7, the tuning screw holes 11, 12, 13 and 14 and the like of the step 2 and the TE103 mode, and performs another integrated structural design on the common port and the resonant cavity cover plate of the TE103 mode, after silver plating, the two parts are welded by high-temperature solder, and screws are installed through the fixing holes 15 of the main cavity, the fastening holes 19 of the cover plate and the installation holes 16, so that the complete TE103 mode waveguide duplex filter is formed. Because the whole TE103 mode waveguide duplex filter mainly comprises the main cavity 1 and the cover plate 20, and the installation of the cover plate 20 has almost no influence on the indexes of the device, the assembly difficulty can be effectively reduced, the success rate of the product is improved, and great convenience is brought to the production work. The design idea is characterized in that the problems of relatively simple processing and small influence of assembly on technical index results are solved, and meanwhile, the reliability of the TE103 mode waveguide duplex filter is improved due to simple assembly. Has wide market prospect in various microwave and millimeter wave communication electronic devices.
The invention is mainly characterized in that the characteristic that the high Q value of the resonant cavity in the TE103 mode of the waveguide is applied to the waveguide filter to generate good pass band insertion loss is utilized, and meanwhile, the cross-coupling structure of the resonant cavity is added to improve the pass band isolation of high and low ends. In the aspect of structure, due to the fact that machining is convenient, the influence of assembly on performance indexes can be almost ignored, technical indexes are excellent, and the like, the method is also a prominent advantage of the method.
The following are specifications of a duplex filter based on the TE103 waveguide mode designed by the system requirements:
(1) and the working frequency: ka wave band
(2) And working bandwidth: 300MHz
(3) Insertion loss: not more than 0.8dB
(4) Port standing waves: less than or equal to 1.2
(5) And isolation of transmitting and receiving: not less than 80dB
(6) And interface form: BJ320 standard waveguide
(7) And working temperature: minus 40 ℃ to plus 55 DEG C
(8) And storage temperature: -55 ℃ to +70 ℃.