Miniaturized s-band microstrip bandpass filter

Abstract

This invention discloses a miniaturized S-band microstrip bandpass filter, comprising an interdigital resonant unit and a hairpin resonant unit, with the hairpin resonant unit positioned in the middle of the interdigital resonant unit. This invention optimizes the left-end suppression performance of the interdigital microstrip bandpass filter by introducing a hairpin microstrip open-circuit line into the interdigital microstrip bandpass filter and forming a transmission zero at the left end through the structure of the hairpin resonant unit itself. Furthermore, the hairpin resonant unit is composed of U-shaped microstrip open-circuit lines, resulting in a small size that simultaneously meets the requirements of miniaturization and high suppression performance.

Description

Technical Field

[0001] This utility model relates to the field of microwave circuit technology, and in particular to a miniaturized S-band microstrip bandpass filter. Background Technology

[0002] Microstrip bandpass filters are key passive devices in microwave circuits, used to allow signals to pass within a specific frequency band while suppressing out-of-band interference. Their structures include parallel-coupled structures, hairpin structures, combline structures, and interdigital structures. To achieve high suppression characteristics in microstrip bandpass filters, multiple filters can be cascaded or the internal order of the filter can be increased. However, cascading multiple filters may lead to impedance matching issues, increasing size and failing to meet miniaturization requirements. Increasing the internal order of the filter introduces more coupling variables, increasing the difficulty of filter tuning and inevitably increasing the filter size, making it impossible to simultaneously achieve miniaturization and high suppression performance. Utility Model Content

[0003] The main purpose of this invention is to provide a miniaturized S-band microstrip bandpass filter, which aims to solve the problem that existing microstrip bandpass filters cannot simultaneously meet the requirements of miniaturization and high suppression performance.

[0004] To achieve the above objectives, this utility model proposes a miniaturized S-band microstrip bandpass filter, which includes:

[0005] The interdigital resonant unit and the hairpin resonant unit are provided, with the hairpin resonant unit located in the middle of the interdigital resonant unit. The hairpin resonant unit is used to form a transmission zero at the left end.

[0006] In one embodiment, the hairpin resonant unit includes a U-shaped microstrip open circuit.

[0007] In one embodiment, the miniaturized S-band microstrip bandpass filter further includes a dielectric substrate on which the interdigital resonant unit and the hairpin resonant unit are disposed.

[0008] In one embodiment, the dielectric substrate is a ceramic dielectric substrate.

[0009] In one embodiment, the miniaturized S-band microstrip bandpass filter operates in the frequency band of 2.16~3.9 GHz.

[0010] This utility model's technical solution optimizes the left-end suppression performance of the interdigital microstrip bandpass filter by introducing a hairpin-type microstrip open circuit into the interdigital microstrip bandpass filter and forming a transmission zero at the left end through the structure of the hairpin-type resonant unit itself. Furthermore, the hairpin-type resonant unit is composed of U-shaped microstrip open circuits, which are small in size and can simultaneously meet the requirements of miniaturization and high suppression performance. Attached Figure Description

[0011] Figure 1 This is a structural diagram of the miniaturized S-band microstrip bandpass filter of this utility model;

[0012] Figure 2 This is a structural diagram of an interdigital microstrip bandpass filter;

[0013] Figure 3 This is a structural diagram of the miniaturized S-band microstrip bandpass filter of this utility model;

[0014] Figure 4 This is a comparison of the S-parameters of the miniaturized S-band microstrip bandpass filter and the interdigital microstrip bandpass filter of this invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0017] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0018] In the description of this utility model, it should be understood that the terms "upper", "lower", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use, or the orientation or positional relationship that is commonly understood by those skilled in the art. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0019] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0020] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0021] To achieve high suppression characteristics in microstrip bandpass filters, multiple filters can be connected in series or the internal order of the filters can be increased. However, connecting multiple filters in series may lead to impedance matching issues, increasing the size and failing to meet the requirements of miniaturization design. Increasing the internal order of the filters will introduce more coupling variables, increasing the difficulty of filter tuning, and will inevitably increase the filter size, making it impossible to simultaneously meet the requirements of miniaturization and high suppression performance.

[0022] To address the aforementioned problems, this invention proposes a miniaturized S-band microstrip bandpass filter. The specific implementation of this invention will be described in detail below with reference to the accompanying drawings.

[0023] like Figure 1-4 As shown, the miniaturized S-band microstrip bandpass filter includes:

[0024] The interdigital resonant unit and the hairpin resonant unit are provided, with the hairpin resonant unit located in the middle of the interdigital resonant unit. The hairpin resonant unit is used to form a transmission zero at the left end.

[0025] In one embodiment, the hairpin resonant unit includes a U-shaped microstrip open circuit.

[0026] In one embodiment, the miniaturized S-band microstrip bandpass filter further includes a dielectric substrate on which the interdigital resonant unit and the hairpin resonant unit are disposed.

[0027] In one embodiment, the dielectric substrate is a ceramic dielectric substrate.

[0028] In one embodiment, the miniaturized S-band microstrip bandpass filter operates in the frequency band of 2.16~3.9 GHz.

[0029] In this embodiment, the hairpin resonant unit is derived from the parallel coupling structure. That is, a U-shaped resonator is obtained by bending the microstrip line, and the resonators are coupled together. In this way, it not only inherits the superior performance of parallel coupling, but also greatly reduces the physical size to meet the miniaturization requirements. Moreover, this structure does not require via grounding and is easy to process.

[0030] like Figure 2 As shown, the resonators in the interdigital resonant unit are arranged in a cross pattern. Interdigital microstrip bandpass filters can be divided into three types according to their structure: those suitable for medium bandwidth input / output resonators with one end open and the other short-circuited; those suitable for wide bandwidth input / output resonators with both ends open; and those with capacitors loaded at the resonator ports. Interdigital microstrip bandpass filters can also be divided into structures with tapped feed lines and structures with coupled feed lines, depending on the feed line. The advantage of microstrip interdigital filters with tapped feed lines compared to those with coupled feed lines is that when the required parallel input / output coupling lines are very compact and physical implementation becomes impractical, the tapped lines can still be used as input / output. Therefore, this feed line structure is widely used in the field of microstrip interdigital filters.

[0031] In practical applications, interdigital microstrip bandpass filters exhibit good suppression performance due to their structural characteristics, which allow for attenuation poles at the right end of the passband. However, their left-end suppression performance differs significantly from the right-end performance, by approximately 20 dB. Therefore, this embodiment introduces a hairpin structure, which uses the resonant unit's own structure to create a transmission zero at the left end. Figure 4 As shown, this achieves the goal of optimizing the left-end suppression of the interdigital microstrip bandpass filter, and the hairpin resonant unit is small in size, which can simultaneously meet the requirements of miniaturization and high suppression performance.

[0032] It is understood that the miniaturized S-band microstrip bandpass filter in this embodiment operates in the frequency band of 2.16-3.9 GHz (S-band) and has a relative bandwidth of 57%. Based on the traditional interdigital microstrip bandpass filter, a hairpin-type open circuit is introduced, which enables the filter to achieve out-of-band rejection of more than 40 dB. Traditional interdigital filters that achieve the same performance require 9th-11th order resonators and have a large filter size. The filter size in this embodiment is reduced by 43% compared with the traditional filter structure, achieving miniaturization, while the out-of-band rejection is also optimized.

[0033] Figure 3 The diagram shows the structure of a miniaturized S-band microstrip bandpass filter. In this embodiment, the dielectric substrate is made of ceramic dielectric, such as alumina ceramic dielectric. First, the high dielectric constant of the ceramic dielectric can reduce the signal transmission wavelength λ in the microstrip structure, thereby reducing the resonator length and miniaturizing the filter. Second, the microstrip ceramic filter can suppress various interference signals and transmit useful signals. Its greatest feature is that it can withstand higher voltage and higher power. Compared with LC cavity filters and dielectric filters, it has the advantages of small size, low power consumption, compact structure and high reliability.

[0034] This novel miniaturized S-band microstrip bandpass filter optimizes the left-end suppression performance of the interdigital microstrip bandpass filter by introducing a hairpin-type microstrip open circuit into the interdigital microstrip bandpass filter. The hairpin-type resonant unit itself forms a transmission zero at the left end, thereby optimizing the left-end suppression performance of the interdigital microstrip bandpass filter. Furthermore, the hairpin-type resonant unit is composed of U-shaped microstrip open circuits, which are small in size and can simultaneously meet the requirements of miniaturization and high suppression performance.

[0035] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A miniaturized S-band microstrip bandpass filter, characterized in that, The miniaturized S-band microstrip bandpass filter includes: The interdigital resonant unit and the hairpin resonant unit are provided, with the hairpin resonant unit located in the middle of the interdigital resonant unit. The hairpin resonant unit is used to form a transmission zero at the left end.

2. The miniaturized S-band microstrip bandpass filter according to claim 1, characterized in that, The hairpin resonant unit includes a U-shaped microstrip open circuit.

3. The miniaturized S-band microstrip bandpass filter of claim 1, wherein, The miniaturized S-band microstrip bandpass filter also includes a dielectric substrate, on which the interdigital resonant unit and the hairpin resonant unit are disposed.

4. The miniaturized S-band microstrip bandpass filter according to claim 3, characterized in that, The dielectric substrate is a ceramic dielectric substrate.

5. The miniaturized S-band microstrip bandpass filter of claim 1, wherein, The miniaturized S-band microstrip bandpass filter operates in the frequency band of 2.16~3.9GHz.

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