Ka-band miniaturized filter based on LTCC technology

Abstract

This invention discloses a Ka-band miniaturized filter based on LTCC technology, comprising a ground plane; an input electrode, an output electrode, and multiple ground electrodes are disposed below the ground plane; a first resonator to a third resonator are disposed above the ground plane; one end of the first resonator is connected to an input port via an input tap, and the input port is connected to the input electrode; one end of the third resonator is connected to an output port via an output tap, and the output port is connected to the output electrode; four independently distributed U-shaped tuning capacitors are disposed between the first to third resonators and the ground plane. This invention uses U-shaped tuning capacitors to precisely control out-of-band characteristics and improve stopband rejection capability. The filter has a passband range of 17.7–21.2 GHz, an insertion loss of less than 1 dB, and a stopband rejection greater than 45 dB, with a maximum of 60 dB, exhibiting advantages such as small size, low loss, and strong rejection.

Description

Technical Field

[0001] This invention relates to the field of radio frequency microwave communication technology, specifically to a Ka-band miniaturized filter based on LTCC technology, and particularly to a miniaturized low-temperature co-fired ceramic (LTCC) comb-shaped bandpass filter employing a bottom electrode and a novel coupling structure. Background Technology

[0002] With the development of modern wireless communication, satellite communication, radar systems, and various smart terminal devices towards the Ka band (26.5-40GHz), increasingly stringent requirements have been placed on filters—key passive components in RF front-end modules: miniaturization, low insertion loss, high out-of-band rejection, and good selectivity have become core technical indicators. Ka-band filters need to achieve low insertion loss, high selectivity, and strong out-of-band rejection within extremely small physical dimensions, while also addressing the challenges of significant parasitic effects from high frequencies and high processing precision requirements.

[0003] To achieve device miniaturization, low-temperature co-fired ceramic (LTCC) technology has become one of the mainstream processes for manufacturing microwave and millimeter-wave filters due to its ability to realize multi-layer three-dimensional structures, flexible design, ease of integration, and excellent high-frequency characteristics. Among the many LTCC filter structures, combline filters are widely used because of their compact structure, relatively large power capacity, and mature design methods.

[0004] Despite some progress in existing technologies, many challenges remain in realizing high-performance miniaturized Ka-band filters: The contradiction between traditional electrode structures and high-frequency performance: Traditional LTCC combline filters often use side electrodes for grounding and coupling. This structure introduces significant parasitic effects and conductor losses at high frequencies, hindering the achievement of extremely low insertion loss. Furthermore, the side electrode structure also faces limitations in further reducing filter size.

[0005] Balancing integration and performance: While LTCC technology supports three-dimensional integration, traditional designs (such as filters based on lumped-parameter elements) often struggle to simultaneously guarantee excellent out-of-band rejection and passband characteristics when pursuing higher integration levels due to factors such as interlayer alignment accuracy and parasitic coupling. Some studies have attempted to improve sideband steepness by increasing the number of filter stages and introducing cross-coupling to generate transmission zeros, but this usually comes at the cost of increasing filter size.

[0006] To suppress interference from adjacent frequency bands, such as in Ka-band filters where effective suppression of uplink signals in the 27.5-31 GHz range is necessary, precise control of the position and depth of the transmission null is crucial. While there are precedents for generating transmission nulls by introducing Z-shaped or U-shaped conductor layers, how these structures can work in conjunction with novel electrodes and compact layouts to achieve precisely controllable out-of-band nulls, especially in ultra-miniaturized designs, remains a challenge.

[0007] Furthermore, the LTCC process itself involves multiple stages such as casting, drilling, filling, printing, lamination, and sintering, making it complex. Deviations in the dielectric constant of the material, lamination alignment errors, and uneven sintering shrinkage can all directly affect the final performance of the filter (e.g., center frequency shift, increased insertion loss). Traditional structures are often more sensitive to these process fluctuations, impacting consistency and yield in mass production. Summary of the Invention

[0008] To overcome the shortcomings of the existing technology, this invention provides a Ka-band miniaturized filter based on LTCC technology. Its primary objective is to solve the problems of high insertion loss and difficulty in achieving strong coupling and high suppression in ultra-small size caused by the use of side electrodes in traditional combline filters in the Ka band. Without increasing the filter size, it significantly enhances the coupling strength between resonators to support a wider passband or smaller volume. Without introducing complex structures, it accurately generates transmission zeros in the stopband (especially the Ka-band uplink frequency band 27.5-31GHz) to achieve high out-of-band suppression.

[0009] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A miniaturized Ka-band filter based on LTCC technology includes a ground plane GND; an input electrode, an output electrode, and multiple ground electrodes are disposed below the ground plane GND; a first resonator R1, a second resonator R2, and a third resonator R3 are disposed above the ground plane GND; one end of the first resonator R1 is connected to an input aperture post Hin via an input tap Jin, and the input aperture post Hin is connected to the input electrode; one end of the third resonator R3 is connected to an output aperture post Hout via an output tap Jout, and the output aperture post Hout is connected to the output electrode. Four independently distributed U-shaped tuning capacitors are provided between the first resonator R1, the second resonator R2, the third resonator R3 and the ground plane GND.

[0010] Preferably, the first resonator R1, the second resonator R2, and the third resonator R3 have the same structure, all being multi-layered three-dimensional structures, wherein: The first resonator R1 includes a horizontally arranged first lower electrode plate J11 and a first upper electrode plate J12, and a vertically arranged first inductor post L11 and a second inductor post L12; the first lower electrode plate J11 and the first middle electrode plate J12 are stacked vertically, the upper end of the first inductor post L11 is connected to one end of the first upper electrode plate J12, the upper end of the second inductor post L12 is connected to one end of the first lower electrode plate J11, and the lower ends of the first inductor post L11 and the second inductor post L12 are respectively connected to the ground plane GND; The second resonator R2 includes a horizontally arranged second lower electrode plate J21 and a second upper electrode plate J22, and a vertically arranged third inductor post L21 and a fourth inductor post L22; the second lower electrode plate J21 and the second upper electrode plate J22 are stacked vertically, the upper end of the third inductor post L21 is connected to one end of the second upper electrode plate J22, the upper end of the fourth inductor post L22 is connected to one end of the second lower electrode plate J21, and the lower ends of the third inductor post L21 and the fourth inductor post L22 are respectively connected to the ground plane GND; The third resonator R3 includes a horizontally arranged lower third electrode plate J31 and a upper third electrode plate J32, and a vertically arranged fifth inductor post L31 and a sixth inductor post L32. The lower third electrode plate J31 and the upper third electrode plate J32 are stacked vertically. The upper end of the fifth inductor post L31 is connected to one end of the upper third electrode plate J32, and the upper end of the sixth inductor post L32 is connected to one end of the lower third electrode plate J31. The lower ends of the fifth inductor post L31 and the sixth inductor post L32 are respectively connected to the ground plane GND.

[0011] Preferably, a first suspended parallel plate J13, a second suspended parallel plate J23, and a third suspended parallel plate J33 are respectively provided above the first upper plate J12, the second upper plate J22, and the third upper plate J32.

[0012] Preferably, the U-shaped tuning capacitor includes a first U-shaped tuning capacitor C1, a second U-shaped tuning capacitor C2, a third U-shaped tuning capacitor C4, and a fourth U-shaped tuning capacitor C4; wherein, the first U-shaped tuning capacitor C1 and the second U-shaped tuning capacitor C2 are located in the projection area below the first resonator R1 and the second resonator R2, and are symmetrically distributed along the central axis; the third U-shaped tuning capacitor C4 and the fourth U-shaped tuning capacitor C4 are located in the projection area below the second resonator R2 and the third resonator R3, and are symmetrically distributed along the central axis.

[0013] Preferably, the ground plane GND has symmetrical rectangular notches at both ends to accommodate the input hole post Hin and the output hole post Hout, respectively.

[0014] Preferably, the bottom of the ground plane GND is provided with multiple through holes, which are respectively connected to multiple grounding electrodes.

[0015] Preferably, the Ka-band miniaturized filter based on LTCC technology has an external ceramic substrate.

[0016] Preferably, the first inductor post L11 of the first resonator R1 is coupled to the third inductor post L21 of the second resonator R2, the second inductor post L12 of the first resonator R1 is coupled to the fourth inductor post L22 of the second resonator R2, and the first lower plate J11 and the first upper plate J12 of the first resonator R1 are capacitively coupled to the second lower plate J21 and the second upper plate J22 of the second resonator R2. The third inductor post L21 of the second resonator R2 is coupled to the fifth inductor post L31 of the third resonator R3, and the fourth inductor post L22 of the second resonator R2 is coupled to the sixth inductor post L32 of the third resonator R3. The second lower plate J21 and the second upper plate J22 of the second resonator R2 form a capacitive side coupling with the third lower plate J31 and the third upper plate J32 of the third resonator R3. The first inductor post L11 of the first resonator R1 is coupled to the fifth inductor post L31 of the third resonator R3, the second inductor post L12 of the first resonator R1 is coupled to the sixth inductor post L32 of the third resonator R3, and the first lower plate J11 and the first upper plate J12 of the first resonator R1 are capacitively coupled to the third lower plate J31 and the third upper plate J32 of the third resonator R3.

[0017] Preferably, the LTCC ceramic substrate has a dielectric constant of 7.4 and a loss tangent of 0.002. This dielectric constant allows for a smaller filter size, while the low loss tangent enables low insertion loss. The filter's conductors and electrodes are printed with silver material. The filter's passband range is 17.7-21.2 GHz, with an insertion loss of less than 1 dB and a minimum insertion loss of only 0.6 dB. In the high-end stopband (27.5-31 GHz), i.e., the uplink suppression at Ka is greater than 45 dB, with a maximum suppression of 60 dB.

[0018] Preferably, the taps Jin and Jout are directly coupled, which allows the tap position to control the external Q value.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: Unlike traditional combline filters that place the main ground electrode on the side of the resonant pillar, this invention places the electrode, crucial for resonator grounding and signal coupling, at the bottom of the dielectric layer, allowing for more flexible circuit design. This bottom electrode, together with the upper resonant pillar, forms a new electric field distribution pattern, effectively reducing the parasitic capacitance introduced by traditional side electrodes at high frequencies, thus laying the foundation for reducing insertion loss.

[0020] Between the resonators composed of a bottom electrode and parallel plates, this invention creatively introduces metallized vias that vertically penetrate multiple dielectric layers. These vias are not simply vertically interconnected, but are designed as inductive elements with specific inductance values. They directly connect the bottom electrode to the resonant structures at different levels, forming strong vertical magnetic coupling and significantly enhancing the coupling coefficient between the resonators. This construction makes it possible to achieve sufficient coupling in a very small physical space, a key means of achieving miniaturization. To precisely control out-of-band characteristics, floating U-shaped stripline capacitors, not directly connected to any DC ground, are placed on both sides of the parallel plate resonators or specific coupling paths. These capacitors are used to adjust the transmission zero at the high-frequency end and suppress second harmonics. The U-shaped capacitors, through their specific geometry, improve the energy coupling of the main path, thereby greatly enhancing stopband rejection capability.

[0021] In this invention, the first, second, and third resonators all adopt through-hole inductors and two layers of short-circuited wide-side coupled striplines. This form enables the resonators to be miniaturized, and their resonance modes only have odd-order modes, thereby suppressing the generation of second harmonics. A suspended parallel plate is added above the resonators, and a capacitor is added to the structure of the parallel plate, which is beneficial to further reduce the size of the resonators. Attached Figure Description

[0022] Figure 1 This is the equivalent circuit diagram of the LTCC bandpass filter of the present invention.

[0023] Figure 2 This is a schematic diagram of the outer surface structure of the LTCC bandpass filter of the present invention.

[0024] Figure 3 This is a schematic diagram of the internal three-dimensional structure of the LTCC bandpass filter of the present invention.

[0025] Figure 4 This is a schematic diagram showing the internal structure of the LTCC bandpass filter of the present invention.

[0026] Figure 5 This is a schematic diagram of the sixth layer of the LTCC bandpass filter of the present invention.

[0027] Figure 6 This is a planar structural diagram of the 7th layer of the LTCC bandpass filter of the present invention.

[0028] Figure 7 This is a planar structural diagram of the 8th layer of the LTCC bandpass filter of the present invention.

[0029] Figure 8 This is a planar structural diagram of the 9th layer of the LTCC bandpass filter of the present invention.

[0030] Figure 9 This is a planar structural diagram of the 11th layer of the LTCC bandpass filter of the present invention.

[0031] Figure 10 The figure shows the S11 simulation results of the LTCC bandpass filter of the present invention.

[0032] Figure 11 The figure shows the S21 simulation results of the LTCC bandpass filter of the present invention.

[0033] Figure 12 This is a schematic diagram of the LTCC bandpass filter mounted on the PCB test board of the present invention.

[0034] Figure 13 This is a three-dimensional structural diagram of the PCB test board of the present invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] like Figure 2 , Figure 3 , Figure 4 , Figure 12 and Figure 13 As shown, this invention provides an external surface structure, an internal multi-layer three-dimensional structure view, and a PCB test board for a Ka-band miniaturized filter based on LTCC technology.

[0037] like Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 9 The image shows a top view of each layer of the internal structure of an LTCC filter.

[0038] like Figure 10 , Figure 11 As shown, the LTCC bandpass filter has extremely low insertion loss in the downlink band of Ka and extremely high out-of-band rejection in the uplink band of Ka.

[0039] To describe the filter in more detail, the invention will now be further described in detail with reference to the accompanying drawings.

[0040] Figure 1This is a schematic diagram of the equivalent circuit of the LTCC bandpass filter of the present invention. Figure 1 As shown, this invention employs a third-order bandpass filter, including a first resonator R1 composed of capacitor C1 and inductor L1, a second resonator R2 composed of capacitor C2 and inductor L2, and a third resonator R3 composed of capacitor C3 and inductor L3. The main coupling is magnetic coupling. As can be briefly described from the schematic diagram, the first resonator R1 and the second resonator R2 are magnetically coupled through inductor L12, the second resonator R2 and the third resonator R3 are magnetically coupled through inductor L23, and the first resonator R1 and the third resonator R3 are cross-magnetically coupled through inductor L13, thereby introducing a transmission zero.

[0041] Figure 2 The diagram shows the external structure of the LTCC bandpass filter of the present invention. It includes a ceramic substrate 1, and its electrodes are all disposed at the bottom of the bandpass filter. Specifically, it includes: a first ground electrode 2, an input electrode 3, a second ground electrode 4, a third ground electrode 5, an output electrode 6, and a fourth bottom ground electrode 7. The electrodes are generally centrally mirror-symmetrical.

[0042] Figure 3 This is a diagram showing the internal structure of the LTCC bandpass filter of the present invention. Figure 4 This is an exploded view of the internal structure of the LTCC bandpass filter of the present invention. The LTCC bandpass filter includes a through-hole inductor Hin connected to the bottom input electrode 3, a first resonator R1, a second resonator R2, a third resonator R3, a pair of U-shaped tuning capacitors C1 and C2, a pair of U-shaped tuning capacitors C3 and C4, a through-hole inductor Hout connected to the bottom output electrode 6, a ground plane GND, and four through-holes h1, h2, h3, and h4 connected to the ground plane GND and the bottom ground electrode. Tap Jin connects the first resonator R1 and the through-hole inductor Hin, and tap Jout connects the third resonator R3 and the through-hole inductor Hout.

[0043] The first resonator R1 is composed of through-hole inductors L11 and L12 and parallel plates J11, J12, and J13. The intersection of the parallel plates generates distributed capacitance, and the short-circuit grounding portion generates inductance. The second resonator R2 is composed of through-hole inductors L21 and L22 and parallel plates J21, J22, and J23. The intersection of the parallel plates generates distributed capacitance, and the short-circuit grounding portion generates inductance. The third resonator is composed of through-hole inductors L31 and L32 and parallel plates J31, J32, and J33. The intersection of the parallel plates generates distributed capacitance, and the short-circuit grounding portion generates inductance. The resonators R1 and R2 are coupled through their own side-mounted inductors L11 and L21, and also through their own side-mounted inductors L12 and L22. They are also laterally coupled to the parallel plates J11 and J12 of resonator R1 and the parallel plates J21 and J22 of resonator R2. The resonators R2 and R3 are coupled through their own side-mounted inductors L21 and L31, and simultaneously through their own side-mounted inductors L22 and L32. They are also laterally coupled to the parallel plates J21 and J22 of resonator R2 and the parallel plates J31 and J32 of resonator R3. Due to their smaller size, the first resonator R1 and the third resonator R3 are coupled through their own side-mounted inductors L11 and L31, and through their own side-mounted inductors L12 and L32. They are also laterally coupled to the parallel plates J11 and J12 of resonator R1 and the parallel plates J31 and J32 of resonator R3, thus achieving cross-coupling.

[0044] like Figure 9 As shown, the ground plane GND is located on the 11th layer, and two rectangular slots are symmetrically provided to connect the bottom input and output electrodes.

[0045] like Figure 8 As shown, four U-shaped tuning capacitors C1, C2, C3, and C4 are located on the 10th layer. The first U-shaped tuning capacitor C1 and the second U-shaped tuning capacitor C2 are located below the first resonator R1 and the second resonator R2, and act on the first resonator R1 and the second resonator R2. The third U-shaped tuning capacitor C3 and the fourth U-shaped tuning capacitor C4 are located below the second resonator R2 and the third resonator R3, and act on the second resonator R2 and the third resonator R3.

[0046] like Figure 7 As shown, parallel plates J11, J21, and J31 are located on the 9th layer and are connected to the ground plane GND through through-hole inductors L12, L22, and L32.

[0047] like Figure 6As shown, parallel plates J12, J22, and J32 are located on layer 8 and are connected to the ground plane GND through via inductors L11, L21, and L31. Taps Jin and Jout are located on layer 8 and are connected to the input and output electrodes through via inductors Hin and Hout.

[0048] like Figure 5 As shown, parallel plates J13, J23, and J33 are located on the 7th layer and are suspended directly above parallel plates J11, J21, and J31.

[0049] The overall external dimensions of this invention are 1.2mm × 1.2mm × 0.5mm. It uses ceramic with a dielectric constant of 7.4 and a loss tangent of 0.002 as the green ceramic tape material. The metal conductor is made of metallic silver with a thickness of 10µm. The thickness of a single layer of green ceramic tape is 35.4µm.

[0050] The LTCC bandpass filter provided by this invention has a passband range of 17.7-21.2 GHz in the downlink band of Ka, with an insertion loss of less than 1 dB and a minimum insertion loss of only 0.6 dB. The stopband of the filter is the uplink band of Ka, 27.5-31 GHz, with a suppression of more than 45 dB and a maximum suppression of 62 dB.

[0051] To facilitate testing, this invention provides a PCB test board that can be used in conjunction with a vector network analyzer for testing.

[0052] like Figure 12 , 13 As shown, the PCB test board uses CPWG transmission lines with a characteristic impedance of 50Ω. The conductor is made of copper, and the dielectric layer is Rogers RO4350 with a dielectric constant of 3.66 and a loss tangent of 0.004, which can effectively reduce dielectric loss.

[0053] The above description of the embodiments is only for the purpose of helping to understand the method and central idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall under the protection of the claims of the present invention.

Claims

1. A Ka-band miniaturized filter based on LTCC technology, comprising a ground plane GND; an input electrode, an output electrode, and multiple ground electrodes are disposed below the ground plane GND; characterized in that, A first resonator R1, a second resonator R2, and a third resonator R3 are disposed above the ground plane GND; one end of the first resonator R1 is connected to the input hole post Hin through the input tap Jin, and the input hole post Hin is connected to the input electrode; One end of the third resonator R3 is connected to the output hole post Hout via the output tap Jout, and the output hole post Hout is connected to the output electrode. Four independently distributed U-shaped tuning capacitors are provided between the first resonator R1, the second resonator R2, the third resonator R3 and the ground plane GND.

2. The Ka-band miniaturized filter based on LTCC technology according to claim 1, characterized in that, The first resonator R1, the second resonator R2, and the third resonator R3 have the same structure, all of which are multi-layered three-dimensional structures.

3. The Ka-band miniaturized filter based on LTCC technology according to claim 2, characterized in that, The first resonator R1 includes a horizontally arranged first lower electrode plate J11 and a first upper electrode plate J12, and a vertically arranged first inductor post L11 and a second inductor post L12; the first lower electrode plate J11 and the first middle electrode plate J12 are stacked vertically, the upper end of the first inductor post L11 is connected to one end of the first upper electrode plate J12, the upper end of the second inductor post L12 is connected to one end of the first lower electrode plate J11, and the lower ends of the first inductor post L11 and the second inductor post L12 are respectively connected to the ground plane GND; The second resonator R2 includes a horizontally arranged second lower electrode plate J21 and a second upper electrode plate J22, and a vertically arranged third inductor post L21 and a fourth inductor post L22; the second lower electrode plate J21 and the second upper electrode plate J22 are stacked vertically, the upper end of the third inductor post L21 is connected to one end of the second upper electrode plate J22, the upper end of the fourth inductor post L22 is connected to one end of the second lower electrode plate J21, and the lower ends of the third inductor post L21 and the fourth inductor post L22 are respectively connected to the ground plane GND; The third resonator R3 includes a horizontally arranged lower third electrode plate J31 and a upper third electrode plate J32, and a vertically arranged fifth inductor post L31 and a sixth inductor post L32. The lower third electrode plate J31 and the upper third electrode plate J32 are stacked vertically. The upper end of the fifth inductor post L31 is connected to one end of the upper third electrode plate J32, and the upper end of the sixth inductor post L32 is connected to one end of the lower third electrode plate J31. The lower ends of the fifth inductor post L31 and the sixth inductor post L32 are respectively connected to the ground plane GND.

4. The Ka-band miniaturized filter based on LTCC technology according to claim 3, characterized in that, Above the first upper electrode plate J12, the second upper electrode plate J22 and the third upper electrode plate J32, there are respectively a first suspended parallel plate J13, a second suspended parallel plate J23 and a third suspended parallel plate J33.

5. The Ka-band miniaturized filter based on LTCC technology according to claim 4, characterized in that, The U-shaped tuning capacitors include a first U-shaped tuning capacitor C1, a second U-shaped tuning capacitor C2, a third U-shaped tuning capacitor C4, and a fourth U-shaped tuning capacitor C4; wherein, the first U-shaped tuning capacitor C1 and the second U-shaped tuning capacitor C2 are located in the projection area below the first resonator R1 and the second resonator R2, and are symmetrically distributed along the central axis; the third U-shaped tuning capacitor C4 and the fourth U-shaped tuning capacitor C4 are located in the projection area below the second resonator R2 and the third resonator R3, and are symmetrically distributed along the central axis.

6. The Ka-band miniaturized filter based on LTCC technology according to claim 1, characterized in that, The ground plane GND has symmetrical rectangular notches at both ends to accommodate the input hole post Hin and the output hole post Hout, respectively.

7. The Ka-band miniaturized filter based on LTCC technology according to claim 5, characterized in that, The bottom of the grounding plate GND has multiple through holes, which are respectively connected to multiple grounding electrodes.

8. The Ka-band miniaturized filter based on LTCC technology according to claim 1, characterized in that, The Ka-band miniaturized filter based on LTCC technology has an external ceramic substrate.

9. The Ka-band miniaturized filter based on LTCC technology according to claim 1, characterized in that, The first inductor post L11 of the first resonator R1 is coupled to the third inductor post L21 of the second resonator R2, and the second inductor post L12 of the first resonator R1 is coupled to the fourth inductor post L22 of the second resonator R2. The first lower plate J11 and the first upper plate J12 of the first resonator R1 are capacitively coupled to the second lower plate J21 and the second upper plate J22 of the second resonator R2. The third inductor post L21 of the second resonator R2 is coupled to the fifth inductor post L31 of the third resonator R3, and the fourth inductor post L22 of the second resonator R2 is coupled to the sixth inductor post L32 of the third resonator R3. The second lower plate J21 and the second upper plate J22 of the second resonator R2 form a capacitive side coupling with the third lower plate J31 and the third upper plate J32 of the third resonator R3. The first inductor post L11 of the first resonator R1 is coupled to the fifth inductor post L31 of the third resonator R3, the second inductor post L12 of the first resonator R1 is coupled to the sixth inductor post L32 of the third resonator R3, and the first lower plate J11 and the first upper plate J12 of the first resonator R1 are capacitively coupled to the third lower plate J31 and the third upper plate J32 of the third resonator R3.

10. The Ka-band miniaturized filter based on LTCC technology according to claim 1, characterized in that, The dielectric constant of the LTCC ceramic dielectric substrate is 7.4, and the loss tangent is 0.002.

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