CN115863942A - Double-passband independently adjustable band-pass filter with constant bandwidth - Google Patents

Abstract

The invention provides an independent adjustable filter with dual passbands maintaining constant bandwidth, which is realized by using two different resonators and sharing the structure of input and output feeders. The resonator includes a microstrip line loaded varactor diode, and the varactor diode is connected with an external bias circuit. The filter mainly includes an upper layer microstrip line structure, an intermediate layer dielectric substrate and a lower layer grounding metal, and has the characteristics of simple structure, miniaturization, and excellent characteristics. It can overcome the shortcomings of insufficient selectivity and bandwidth change of the dual-passband adjustable filter, realize the independent adjustment of the dual-passband and maintain the effect of constant bandwidth, and is easy to realize circuit integration and system packaging, and can also be widely used in industrial production middle.

Description

A Constant Bandwidth Dual Passband Independently Adjustable Bandpass Filter

technical field

The invention relates to the technical field of microwave communication, in particular to a double-pass band independently adjustable band-pass filter with constant bandwidth.

Background technique

With the rapid development of modern wireless communication technology, more and more mobile communication, satellite communication, radar tracking and remote sensing technology need to rely on microwave and millimeter wave technology, which leads to an increasingly complex electromagnetic environment and ultimately makes spectrum resources more and more tense. The contradiction between limited spectrum resources and application requirements is becoming increasingly prominent. Traditional narrowband communication systems cannot meet the actual needs of these application scenarios due to their small transmission capacity and low transmission rate. Therefore, adjustable technology has attracted more and more attention.

In order to meet the urgent needs of multiple users for different communication modes and high transmission rates, modern communication systems need to combine multi-band technology and adjustable technology. Therefore, adjustable multi-passband filters have emerged as the times require. On the other hand, with the rapid development of wireless communication technologies, it is usually necessary to communicate through a series of channels with the same bandwidth. Although a large number of adjustable dual-passband filters have been reported, these filters cannot meet the requirements of constant bandwidth and independent adjustment, and their complex structures increase the uncertainty of many designs.

The tunable filter structure designed in the past has the following disadvantages:

(1) Bandwidth changes during frequency adjustment range;

(2) The passband in the multi-passband adjustable filter is not independently adjustable;

(3) During the adjustment process, the performance of the filter becomes worse and unstable.

Contents of the invention

In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a constant bandwidth dual-band independently adjustable band-pass filter, which is compact in structure, can simultaneously achieve high selectivity, independently adjustable, and can maintain a constant bandwidth .

To achieve the above object, the present invention provides the following scheme:

An independently adjustable filter with dual passbands that maintains a constant bandwidth, comprising: an upper layer microstrip structure, an intermediate layer dielectric substrate, a lower layer ground metal, a first port, a second port, and a first microstrip connected to the first port A strip line, a second microstrip line connected to the second port; the upper layer microstrip structure is attached to the upper surface of the intermediate layer dielectric substrate, and the lower layer ground metal is attached to the lower layer of the intermediate layer dielectric substrate surface; the first port and the second port are respectively located on both sides of the intermediate layer dielectric substrate; the first microstrip line and the second microstrip line are connected to each other to form a common input and output feeder line;

The upper microstrip structure includes a first resonator and a second resonator; both the first resonator and the second resonator are bilaterally symmetrical about the vertical axis; the first resonator is located on the common input and output feeder and connected to the common input and output feeder in a slot coupling manner; the first resonator includes two symmetrical impedance line structures; the impedance line structure includes a low impedance line, a first high impedance line, a second Two high-impedance lines, the third high-impedance line, the fourth high-impedance line and the first varactor diode; one end of the low-impedance line is connected to the first bias voltage through a large resistor, and the other end of the low-impedance line is connected to the first bias voltage. connected to the first high-impedance line and the second high-impedance line, the other end of the second high-impedance line is connected to one end of the first varactor diode, and the other end of the first varactor diode Both are connected to the third high-impedance line and the fourth high-impedance line, and the other end of the fourth high-impedance line is connected to the ground; the two symmetrical low-impedance lines are coupled to each other, and the two symmetrical the first high impedance lines are coupled to each other;

The second resonator is located inside the common input and output feeder, and is connected to the common input and output feeder in a slot-coupled manner; the second resonator includes a third varactor diode, a fifth microstrip line, The sixth microstrip line, the seventh microstrip line, and two symmetrical microstrip line structures; the microstrip line structure includes a second varactor diode, a third microstrip line, and a microstrip line connected to the third microstrip line A fourth microstrip line; the other end of the fourth microstrip line is connected to one end of the second varactor diode, and the other end of the second varactor diode is connected to the fifth microstrip line, the The two ends of the fifth microstrip line are respectively grounded through a large resistance, and the center of the fifth microstrip line is connected to the sixth microstrip line and the seventh microstrip line by loading the third varactor diode ; The sixth microstrip line is connected to the second bias voltage through a large resistor.

Preferably, the first resonator is used to generate two modes to form a first passband, and the frequency of the first passband can be adjusted by changing the capacitance of the first varactor diode; the second resonant The device is used to generate odd and even two modes to form a second passband, and realize the frequency adjustment of the second passband frequency by changing the capacitance of the second varactor diode; the sixth microstrip line and the stub structure The seventh microstrip line is loaded with the third varactor diode to generate its own transmission zero.

Preferably, the intermediate dielectric substrate is R04003C, with a thickness of 0.508mm, a dielectric constant of 3.55, and a loss tangent of 0.0027.

Preferably, the radius of the ground hole where both ends of the fifth microstrip line are respectively grounded through a large resistance is 0.3 mm.

Preferably, the first bias voltage and/or the second bias voltage is 0-15V.

Preferably, the model of the first varactor is silicon varactor SMV1233; the model of the second varactor and/or the third varactor is silicon varactor SMV1234.

Preferably, the resistance value of the large resistor is 100K ohms.

Preferably, the common input and output feeder includes a source-load coupling structure, and the source-load coupling structure is used to additionally generate three adaptive transmission zeros.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

The present invention provides the present invention has the following beneficial effects

The present invention can generate four transmission zeros of the upper and lower passbands through the stub loading and source-load coupling structure to achieve high selectivity; and realize the independent adjustment of the upper and lower passbands by sharing the input and output feeders through two different resonators . And in a specific embodiment, the constant bandwidth in the frequency tuning process is realized by controlling the coupling coefficient K ₁₂ and the external quality factor Q _e . The invention can make the structure of the device compact and realize the independent adjustment of two passbands while maintaining a constant absolute bandwidth.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

FIG. 1 is a schematic diagram of a three-dimensional structure of a tunable filter provided by an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a tunable filter provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of the physical size of the tunable filter provided by the embodiment of the present invention;

4 is a schematic diagram of an S-parameter simulation curve of an adjustable passband provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of an S-parameter simulation curve of an adjustable two-passband provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The occurrences of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments.

The terms "first", "second", "third" and "fourth" in the specification and claims of the present application and the drawings are used to distinguish different objects, rather than to describe a specific order . Furthermore, the terms "include" and "have", as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a series of steps, processes, methods, etc. are not limited to the listed steps, but optionally also include steps that are not listed, or optionally also include the inherent characteristics of these processes, methods, products or equipment. other steps.

The object of the present invention is to provide a constant bandwidth double passband independently adjustable bandpass filter, which has a compact structure, can realize high selectivity at the same time, is independently adjustable, and can maintain a constant bandwidth.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 is a schematic diagram of a three-dimensional structure of an adjustable filter provided by an embodiment of the present invention. As shown in Figure 1, this embodiment provides a dual-passband independently adjustable filter that maintains a constant bandwidth, including an upper microstrip structure, The middle layer dielectric substrate and the lower layer ground metal.

As shown in Fig. 2, the upper microstrip structure is left-right symmetrical about the vertical axis. The microstrip structure of the filter is realized by two different resonators through a common input and output feeder, and the two different resonators are respectively the first resonator and the second resonator; the first resonator and the second resonator are both It is symmetrical about the vertical axis; the first port of the filter is located on one side of the dielectric substrate, and the second port is located on the other side of the dielectric substrate; two 50-ohm microstrip lines are respectively connected to the corresponding two ports, which Two 50 ohm microstrip lines are the first microstrip line 12 (12_1), and the two microstrip lines are arranged on the same horizontal line; the first microstrip line 12 is connected with the second microstrip line 11 (11_1) to form a common Input and output feeders.

The first resonator is located on the outside of the common feeder, and is connected to the feeder in a slot-coupled manner; the first resonator includes a symmetrical low-impedance line 1 (1_1) and a first high-impedance line 2 (2_1), and a second high-impedance line Line 3, the third high-impedance line 4, the fourth high-impedance line 5 and the first varactor diode Cv1, one section of the low-impedance line 1 is connected to the first bias voltage (bias 1) through a large resistor, and the other end is connected to the first bias voltage (bias 1). The first high-impedance line 2 is connected to the second high-impedance line 3, the other end of the second high-impedance line 3 is connected to one end of the first varactor diode _Cv1 , and the other end of the first varactor diode _Cv1 is connected to the third high-impedance line The impedance line 4 is connected to the fourth high-impedance line 5, and the other end of the fourth high-impedance line 5 is connected to the ground; wherein, the low-impedance line 1 and the low-impedance line 1_1 are mutually coupled, and the first high-impedance line 2 is connected to the first high-impedance line 5. The impedance lines 2_1 are coupled to each other.

The second resonator is located at the inner test of the common feeder, and is connected with the feeder in a slot-coupled manner; the second resonator includes a symmetrical third microstrip line 6 connected to the fourth microstrip line 7, and the fourth microstrip line 7 The other end is connected to one end of the second varactor diode C _v2 , and the other end of the second varactor diode C _v2 is connected to the fifth microstrip line 8, and the two ends of the fifth microstrip line 8 are respectively grounded through a large resistance, and the fifth The center of the microstrip line 8 is connected to the seventh microstrip line 9 and the sixth microstrip line 10 by loading the third varactor diode C _v3 ; the seventh microstrip line 9 is connected to the second bias voltage (bias voltage 2) connected.

The first resonator is a pair of dual-mode resonators coupled with the feeder to generate two resonant modes to form a first passband, and the frequency of a passband can be adjusted by changing the external bias voltage 1 . The second resonator is a step-impedance resonator loaded with stubs, which can generate two resonant modes, one odd and one even, to form a second passband. The frequency of the second passband can be adjusted by changing the external bias voltage 2. The resonator An additional zero can also be generated.

In this embodiment, the coupling coefficient K ₁₂ and the external quality factor Q _e of the upper and lower passbands are respectively analyzed. When the bandwidth of the passband remains constant, the coupling coefficient K ₁₂ decreases with the increase of the frequency in the tuning process, while the external quality factor Q e The quality factor Q _e increases.

As shown in FIG. 1 , the intermediate dielectric plate used in this embodiment is R04003C, with a thickness of 0.508 mm, a dielectric constant of 3.55, and a loss tangent of 0.0027. The feeder structure uses a source-load coupling structure for feeding, which can introduce additional transmission zeros to improve the selectivity of the passband and the isolation between the passbands.

As shown in Figure 3, the detailed circuit dimensions of the resonator structure are: L ₁ =1.1mm, L ₂ =2.4mm, L ₃ =4.15mm, L ₄ =5.65mm, L ₅ =2.7mm, L ₆ =12.1mm , L ₇ =5.8mm, L ₈ =4.3mm, L ₉ =7.85mm, L ₁₀ =6.95mm, L ₁₁ =19.95mm, w ₁ =2.3mm, w ₂ =0.1mm, w ₃ =0.3mm, w ₄ = 0.7 mm, w ₅ = 0.3 mm, w ₆ = 0.15 mm, w ₇ = 0.4 mm, w ₈ = 1.1 mm, g ₁ = 0.3 mm, g ₂ = 0.4 mm, s ₁ = 0.3 mm, s ₂ = 0.2 mm, s ₃ =0.8 mm. The ground hole radius is 0.3mm.

In this embodiment, the high-frequency simulation software sonnet is used to optimize and analyze the overall structure, and the obtained S-parameter simulation curves are shown in Fig. 4 and Fig. 5 . As can be seen from Fig. 4 and Fig. 5, the first passband center frequency of the filter can be changed in the range of 2.06-2.22GHz, and the absolute bandwidth can be kept constant at 60MHz during the change process; the second passband center frequency can be changed at 3.1 Change within the range of -3.6GHz, the absolute bandwidth can remain unchanged at 72MHz during the change process; in the entire tuning range, the insertion loss is less than 1.4dB, and the return loss is better than 12dB; and the tuning process of the upper and lower passbands does not affect each other, you can Two passbands are independently adjustable. Two adaptive zeros on either side of the upper and lower passbands make this filter highly selective.

In summary, the double-passband independent tunable filter with constant bandwidth of the present invention combines multimode resonators and step impedance resonators to achieve a compact structure, high selectivity, low loss, and bandwidth can be maintained during the adjustment process. Constant dual passband independently tunable filter suitable for modern wireless communication systems.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. A double-passband independently adjustable filter that maintains a constant bandwidth is characterized in that it includes: an upper layer microstrip structure, an intermediate layer dielectric substrate, a lower layer ground metal, a first port, a second port, and the first The first microstrip line connected to the port and the second microstrip line connected to the second port; the upper layer microstrip structure is attached to the upper surface of the intermediate dielectric substrate, and the lower layer ground metal is attached to the The lower surface of the interlayer dielectric substrate; the first port and the second port are respectively located on both sides of the interlayer dielectric substrate; the first microstrip line and the second microstrip line are connected to each other to form a Shared input and output feeders; The upper microstrip structure includes a first resonator and a second resonator; both the first resonator and the second resonator are bilaterally symmetrical about the vertical axis; the first resonator is located on the common input and output feeder and connected to the common input and output feeder in a slot coupling manner; the first resonator includes two symmetrical impedance line structures; the impedance line structure includes a low impedance line, a first high impedance line, a second Two high-impedance lines, the third high-impedance line, the fourth high-impedance line and the first varactor diode; one end of the low-impedance line is connected to the first bias voltage through a large resistor, and the other end of the low-impedance line is connected to the first bias voltage. connected to the first high-impedance line and the second high-impedance line, the other end of the second high-impedance line is connected to one end of the first varactor diode, and the other end of the first varactor diode Both are connected to the third high-impedance line and the fourth high-impedance line, and the other end of the fourth high-impedance line is connected to the ground; the two symmetrical low-impedance lines are coupled to each other, and the two symmetrical the first high impedance lines are coupled to each other; The second resonator is located inside the common input and output feeder, and is connected to the common input and output feeder in a slot-coupled manner; the second resonator includes a third varactor diode, a fifth microstrip line, The sixth microstrip line, the seventh microstrip line, and two symmetrical microstrip line structures; the microstrip line structure includes a second varactor diode, a third microstrip line, and a microstrip line connected to the third microstrip line A fourth microstrip line; the other end of the fourth microstrip line is connected to one end of the second varactor diode, and the other end of the second varactor diode is connected to the fifth microstrip line, the The two ends of the fifth microstrip line are respectively grounded through a large resistance, and the center of the fifth microstrip line is connected to the sixth microstrip line and the seventh microstrip line by loading the third varactor diode ; The sixth microstrip line is connected to the second bias voltage through a large resistor. 2. A kind of double-passband independent tunable filter that keeps constant bandwidth according to claim 1, is characterized in that, described first resonator is used for generating two modes, to form the first passband, and by changing The capacitance of the first varactor diode is used to realize the adjustable frequency of the first passband; the second resonator is used to generate two modes of odd and even to form the second passband, and by changing the frequency of the second varactor diode The capacitance of the capacitor is used to realize the frequency adjustment of the second passband frequency; the sixth microstrip line and the seventh microstrip line of the stub structure are loaded with a third varactor diode to generate a transmission zero point of its own. 3. A dual-band independent tunable filter with constant bandwidth according to claim 1, characterized in that the intermediate dielectric substrate is R04003C with a thickness of 0.508mm, a dielectric constant of 3.55, and a loss angle of The tangent is 0.0027. 4. A kind of independent adjustable filter with dual-pass bands maintaining constant bandwidth according to claim 1, characterized in that, the two ends of the fifth microstrip line pass through the ground hole of the large resistance ground respectively. The radius is 0.3mm. 5 . The dual-band independently adjustable filter with constant bandwidth according to claim 1 , wherein the first bias voltage and/or the second bias voltage is 0-15V. 6. A kind of independent adjustable filter with dual passbands maintaining a constant bandwidth according to claim 1, characterized in that, the model of the first varactor is a silicon varactor SMV1233; the second varactor The model of the diode and/or the third varactor is a silicon varactor SMV1234. 7. A dual-band independent adjustable filter with constant bandwidth according to claim 1, characterized in that the resistance value of the large resistor is 100K ohms. 8. A kind of independent adjustable filter with dual passbands maintaining constant bandwidth according to claim 1, characterized in that, said common input and output feeder includes a source-load coupling structure, and said source-load coupling structure is used to generate additional Three adaptive transmission zeros.

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