Compact high-frequency selectivity patch filter with loaded branches

Abstract

The invention discloses a compact high-frequency-selectivity patch filter with loaded branches. The compact high-frequency-selectivity patch filter comprises a rectangular metal patch and two metal branches on the upper layer, a dielectric substrate on the middle layer, and a metal ground and two metal probes on the lower layer. The two metal branches are vertically connected to the middle points of the upper and lower long edges of the rectangular metal patch respectively; the two metal probes vertically penetrate through the metal ground and the dielectric substrate from the bottom respectively and then are connected with the rectangular metal patch, and the two feeding points are symmetrically located on the left side and the right side of the upper portion of the rectangular metal patch. According to the compact patch filter, two symmetrical feeding points are introduced to the side, close to one long edge, of the rectangular metal patch, a pair of metal branches are introduced perpendicular to the long edge of the patch, two transmission zero points close to the edge of a frequency band are introduced while three resonance modes are achieved, and the compact patch filter is simple in structure and high in frequency selectivity. The two quarter-wavelength metal branches can expand the filtering bandwidth and improve the frequency selectivity of the filter at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to a microwave communication device, in particular to a high frequency selective patch filter. BACKGROUND

[0002] Microstrip bandpass filters have been extensively studied and applied in radio frequency / microwave circuits and systems. Compared with microstrip line resonators, microstrip patch resonators have the advantages of lower insertion loss and higher power handling. Therefore, patch resonators are more attractive for bandpass filters.

[0003] Generally, patch filters can be designed using patch resonators of any shape, such as square, circular, triangular resonators, etc., but square and circular patch resonators are more often used because they can support dual-mode characteristics. Dual-mode patch resonators can achieve quasi-elliptic filter responses with two transmission poles (TPs) and two finite transmission zeros (FTZs), which are more advanced than filters using two coupled single-mode patch resonators. However, the size of conventional dual-mode patch resonators can be large. To reduce the size of dual-mode patch filters, slots can be employed on the metal surface of the patch resonator. Larger size slots can achieve smaller size patch filters, but the unloaded quality (Qu) factor of the patch resonator is deteriorated due to increased radiation loss.

[0004] To achieve higher bandpass filter performance, two or more dual-mode patch resonators can be cascaded to design high-order filters, but their size is large. In addition to dual-mode patch filters, filters with reduced size are designed by using triple-mode patch resonators, but there is still a problem of poor frequency selectivity. Furthermore, the bandwidth and center frequency of the reduced size dual-band bandpass filter designed by studying the multi-mode characteristics of the patch resonator are difficult to control independently. SUMMARY

[0005] The present application aims to solve the problems of the prior art, such as complex structure, increased size, and increased loss, and to achieve the filter function without increasing complexity.

[0006] Technical solution: A compact high-frequency selective patch filter loaded with branches, comprising a rectangular metal patch and two metal branches on the upper layer, a dielectric substrate on the middle layer, and a metal ground and two metal probes on the lower layer; the two metal branches are respectively connected perpendicularly to the middle points of the upper and lower long sides of the rectangular metal patch; the two metal probes are respectively connected to the rectangular metal patch after being vertically passed through the metal ground and the dielectric substrate from the bottom; and the two feed points are symmetrically located on the left and right sides of the upper part of the rectangular metal patch.

[0007] Further, the center frequency of the filter is controlled by controlling the length of the rectangular metal patch, and the impedance matching is adjusted by the width of the rectangular metal patch.

[0008] Further, the frequency of the transmission zero of the filter is controlled by controlling the length and width of the metal stub.

[0009] Further, the length of the rectangular metal patch is between 0.49 λ g and 0.50 λ g , the width is between 0.31 λ g and 0.32 λ g , λ g corresponding to the center frequency.

[0010] Further, the length of the metal stub is between 0.25 λ g and 0.26 λ g , the width is between 0.02 λ g and 0.03 λ g .

[0011] Further, the distance between the two feeding points and the upper edge of the rectangular metal patch is 0.045 λ g to 0.046 λ g .

[0012] Further, the distance between the two feeding points is 0.25 λ g to 0.251 λ g .

[0013] Beneficial effects: the existing patch filter has a narrow bandwidth, and the three-mode patch filter with a larger bandwidth has the problems of large size and lack of frequency selectivity. The present application introduces two symmetric feeding points near one long side of the rectangular metal patch, and introduces a pair of metal stubs perpendicular to the long side of the rectangular metal patch, which realizes three resonance modes and introduces two transmission zeros near the band edge, realizes a compact patch filter with simple structure and high frequency selectivity. Among them, the two quarter-wave metal stubs perpendicular to the rectangular metal patch can expand the filter bandwidth while improving the frequency selectivity of the filter. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A top view schematic diagram of the patch filter of the present application; Figure 2 A top view schematic diagram of the patch filter of the present application; Figure 1 A longitudinal section schematic diagram through one of the feed points; Figure 3 S-parameter simulation results of the patch filter of the embodiment. DETAILED DESCRIPTION

[0015] The present application will be further explained in conjunction with the accompanying drawings.

[0016] As shown in Fig. 1, a compact patch filter with high frequency selectivity and loaded stubs, the upper layer is composed of a rectangular metal patch 2 and two metal stubs 4, the middle layer is a dielectric substrate 1, and the lower layer is divided into a metal ground 6 and two metal probes 5. Figure 1 , Figure 2

[0017] Among them, the two metal stubs 4 are respectively connected perpendicularly to the middle points of the upper and lower long edges of the rectangular metal patch 2. The two metal probes 5 are respectively connected to the rectangular metal patch 2 after vertically penetrating through the metal ground 6 and the dielectric substrate 1 from the bottom. The two feed points 3 of the metal probe 5 are symmetrically located on the left and right sides of the upper part of the rectangular metal patch 2.

[0018] The length of the rectangular metal patch 2 is between 0.49 λ g and 0.5 λ g , the width is between 0.31 λ g and 0.32 λ g , λ g and the center frequency corresponds to the electrical wavelength.

[0019] The length of the metal stub 4 is between 0.25 λ g and 0.26 λ g , the width is between 0.02 λ g and 0.03 λ g .

[0020] The feed point 3 deviates to the positive direction of the y-axis to 0.045 λ g to 0.046 λ g from the upper edge of the rectangular metal patch 2. The distance between the two feed points 3 along the x-axis direction is between 0.25 λ g and 0.251 λ ​g .

[0021] The material of the medium substrate 1 is RO4003C, and the substrate thickness is 0.813 mm.

[0022] For this filter structure, the signal is fed through the metal probe 5 to excite the rectangular metal patch 2 to generate a main electromagnetic field mode TM10 mode, and then the electromagnetic energy is excited through the metal branch 4 to excite two additional electromagnetic field modes and save the energy flowing through. When the energy is exchanged with the main mode, the phase of the current in the strip of the metal branch 4 and the current in the rectangular metal patch 2 is offset, so that the energy of a certain frequency is greatly lost, thereby creating a radiation zero point of a certain frequency to realize the filtering function.

[0023] In the present application, the two metal branches 4 are close to one quarter of the wavelength in length, so as to function as a resonator as a short-circuit branch, and the electric field of the two branches is uniformly and reversely distributed when working. The introduction of additional electromagnetic field modes for the filter increases two additional resonance points, which can effectively increase the width of the working frequency band. In addition, the distance between the two ports is also close to one quarter of the wavelength, which can provide a transmission zero point at high frequencies.

[0024] The position of the transmission zero point can be controlled by controlling the length and width of the metal branch 4, the central frequency can be controlled by controlling the length of the metal patch 2 along the x-axis direction, and the impedance matching can be improved to a certain extent by controlling the length of the rectangular metal patch 2 along the y-axis direction.

[0025] In the present embodiment, the length of the rectangular metal patch 2 is 0.495 λ g , and the width is 0.318 λ g . The length of the metal branch 4 is 0.25 λ g , and the width is 0.021 λ g . The distance between the feeding point 3 and the upper edge of the rectangular metal patch 2 is 0.045 λ g , and the distance between the two feeding points 3 along the x-axis direction is 0.25 λ g . The present embodiment works at 3.62 GHz, and the 10 dB matching bandwidth is 11.1%, and the two transmission zero points are respectively at 3.358 GHz and 3.844 GHz.

[0026] The S parameter simulation result of the patch filter of the present embodiment is shown in Figure 3 , and it can be seen that the profile and size of the present embodiment are greatly improved compared with the conventional patch filter.

[0027] Compared with the conventional patch filter, the patch filter of the present application can realize the miniaturization of the patch filter without complex structure, and has the advantages of simple structure, small overall size, wide working frequency band and no additional loss.

[0028] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A compact, high-frequency selective patch filter with loaded stubs, characterized in that, It includes an upper rectangular metal patch (2) and two metal branches (4), a middle dielectric substrate (1), and a lower metal ground (6) and two metal probes (5); wherein, the two metal branches (4) are vertically connected to the midpoints of the upper and lower long sides of the rectangular metal patch (2); the two metal probes (5) pass vertically through the metal ground (6) and the dielectric substrate (1) from the bottom and are connected to the rectangular metal patch (2); and the two power supply points (3) are symmetrically located on the left and right sides of the upper part of the rectangular metal patch (2).

2. The high-frequency selective patch filter with compact loaded stubs according to claim 1, characterized in that, The center frequency of the filter is controlled by controlling the length of the rectangular metal patch (2), and the impedance matching is adjusted by controlling the width of the rectangular metal patch (2).

3. The high-frequency selective patch filter with compact loaded stubs according to claim 2, characterized in that, The frequency of the transmission zero of the filter is controlled by controlling the length and width of the metal stub (4).

4. The high-frequency selective patch filter with compact loaded stubs according to claim 1 or 2, characterized in that, The length of the rectangular metal patch (2) is 0.49 mm. λ g to 0.50 λ g Between, with a width of 0.31 λ g Up to 0.32 λ g between, λ g The wavelength is the electrical wavelength corresponding to the center frequency.

5. A high-frequency selective patch filter with a compact loaded stub as described in claim 1 or 3, characterized in that, The length of the metal branch (4) is 0.

25. λ g Up to 0.26 λ g Between, with a width of 0.02 λ g Up to 0.03 λ g between, λ g The wavelength is the electrical wavelength corresponding to the center frequency.

6. A high-frequency selective patch filter with a compact loaded stub according to any one of claims 1-3, characterized in that, The distance between the two feed points (3) and the upper edge of the rectangular metal patch (2) is 0.

045. λ g Up to 0.046 λ g , λ g The wavelength is the electrical wavelength corresponding to the center frequency.

7. The high-frequency selective patch filter with compact loaded stubs according to claim 6, characterized in that, The distance between the two feed points (3) is 0.

25. λ g up to 0.251 λ g .

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