[0028] 1. Solve the problem of liquid crystal packaging. The method used is to etch a hollow structure on the intermediate dielectric substrate, and bond the hollow part to the bottom metal carrier through conductive glue to form a groove with the same thickness as the dielectric substrate to accommodate the liquid crystal Then, the top dielectric substrate is glued to the grooved dielectric substrate through conductive glue, thereby realizing the liquid crystal packaging, solving the problem of liquid crystal leakage in the traditional packaging method, and greatly improving the engineering application value;
[0029] 2. Solve the problem of impedance mismatch caused by impedance changes during the tuning process of the liquid crystal device. The method adopted is to transition the substrate integrated waveguide inverted metal layer of the liquid crystal contact part to the coplanar waveguide structure with fixed impedance on the upper layer by means of interlayer via interconnection, and adopt a step between the metal via and the lead metal layer Impedance transition method to achieve the purpose of impedance matching, thereby solving the problem of impedance mismatch;
[0030] 3. The problem that the traditional broadside coupling filter cannot be loaded with modulation voltage is solved. The present invention adopts the method of contact-fed open resonant ring defect structure, that is, the resonant unit adopts the open resonant ring defect structure, and the input and output feeders The direct contact feeding method is adopted to maintain the low frequency path of the entire filter to load the low frequency modulation voltage, thereby solving the problem that the traditional broadside coupling filter cannot load the modulation voltage due to the discontinuity;
[0031] The technical problem proposed by the present invention is solved as follows: Provide a new package based on a liquid crystal material substrate integrated waveguide microwave tunable filter, the specific structure of which is as follows figure 1 As shown, it includes the following components:
[0032] Dielectric substrate and metal carrier board. Among them, the dielectric substrate is used to carry the input and output feeders and the upper metal surface of the substrate integrated waveguide; on the one hand, the metal carrier serves as the lower metal surface of the substrate integrated waveguide; on the other hand, it serves as the lower surface of the groove containing the liquid crystal. The two are bonded together by conductive glue during assembly to realize the encapsulation of the liquid crystal.
[0033] 1) Dielectric substrate:
[0034] The lower surface of the upper dielectric substrate is etched with the feeder structure and the upper metal surface of the resonant unit of the substrate integrated waveguide. The resonant unit adopts an open resonant ring defect structure, and the signal is fed through the feeder and passes through the resonant unit to form the required filter Frequency response. The upper surface of the upper dielectric substrate is etched with a 50-ohm coplanar waveguide as the input and output port. The 50-ohm coplanar waveguide port is connected to the feeder on the lower surface through a metalized through hole. On the one hand, the modulation voltage is applied through a continuous metal connection, and the other On the one hand, it makes up for the discontinuity of the upper and lower transmission lines.
[0035] 2) Metal carrier board:
[0036] The surface of the metal carrier and the dielectric substrate with a hollow structure are bonded together by conductive glue to form a groove with the same thickness as the dielectric substrate. The groove is used to accommodate liquid crystal; on the other hand, the metal carrier is also integrated as a substrate The bottom surface of the waveguide.
[0037] 3) Assembly:
[0038] After the metal carrier and the dielectric substrate, the dielectric substrate and the dielectric substrate are bonded together by conductive glue, the liquid crystal is injected through the injection hole reserved on the upper dielectric substrate, and then the reserved injection hole is sealed with AB glue to complete the assembly .
[0039] 4) Working process:
[0040] After the external modulation voltage is applied to the radio frequency signal through Bias-T, it is input to the designed substrate integrated waveguide filter through the upper input and output ports of the upper dielectric substrate. When the amplitude of the peak voltage of the modulation signal is 0, the long axes of the liquid crystal molecules are parallel to each other and parallel to the dielectric substrate. At this time, the dielectric constant is small. When the amplitude of the peak voltage of the modulation signal increases, the direction of the liquid crystal molecules in the grooves of the dielectric substrate will gradually deflect to the direction of the electric field, until the modulation voltage is high enough and reaches the saturation voltage of the liquid crystal material, the polarization of the liquid crystal reaches saturation. During this process, the dielectric constant of the liquid crystal increases and reaches the maximum value.
[0041] It is precisely because the dielectric constant of the liquid crystal material can change with the change of the modulation voltage, the electrical length of the resonant unit changes with the change of the liquid crystal dielectric constant, and the resonant frequency changes accordingly, so it finally achieves continuous Adjustable filter frequency response.
[0042] The present invention provides a novel package and design method for a substrate-integrated waveguide microwave tunable filter based on liquid crystal materials. The three-dimensional structure diagram is as follows figure 1 As shown, the side view is as figure 2 Shown. The filter adopts the etching of the open resonant ring (13, 14, 15) on the upper metal surface (11) of the substrate integrated waveguide to achieve bandpass characteristics; the upper metal surface (11) of the substrate integrated waveguide and the intermediate dielectric substrate The metallized shielded through holes (16) on both sides and the bottom metal carrier (29) together form the substrate integrated waveguide; the inverted microstrip line (8, 20) on the lower surface of the upper dielectric substrate passes through the stepped impedance transformer (9, 19) ) Is connected with the upper metal surface (11) of the substrate integrated waveguide to form an impedance matching transition from the microstrip line to the substrate integrated waveguide; the metalized signal through-hole discs (5, 7, 21, 22) are in the input and output 50 ohm coplanar The connection between the waveguide feeder (2, 26) and the inverted microstrip line (8, 20) on the lower surface of the upper dielectric substrate can effectively reduce the signal discontinuity between the transmission line and the signal via; the liquid crystal is mounted on the intermediate dielectric substrate (28) in the groove (17). The external signal enters the filter through the input and output 50 ohm coplanar waveguide feeder (2, 26) to form the required frequency response, and the low-frequency modulation signal superimposed with the RF signal (accessed through Bias-T) also passes through the inverted microstrip section Generate the required electric field and modulate the liquid crystal material to change its dielectric constant, thereby forming an adjustable frequency response. The inverted microstrip line (8, 20) on the lower surface of the upper dielectric substrate passes through the upper dielectric substrate (1) through two metallized signal through holes (6, 23) to transition to the upper surface of the upper dielectric substrate (1) and external fixed input and output The 50 ohm coplanar waveguide feeder lines (2, 26) are connected to form a complete filter.
[0043] The assembling step is to first bond the intermediate dielectric substrate (28) and the metal carrier board (29) through conductive adhesive, and then bond the upper dielectric substrate (1) and the intermediate dielectric substrate (28) together through conductive adhesive. Then, the liquid crystal is injected into the groove (17) on the intermediate layer dielectric substrate through the liquid crystal injection holes (10, 12, 18, 24) reserved on the upper dielectric substrate (1). When working, the RF signal and modulation voltage signal are added through the input and output 50 ohm coplanar waveguide feeder (2, 26), and then the dielectric constant of the liquid crystal is changed by changing the amplitude of the modulation voltage, and finally a continuously adjustable frequency response is obtained.
