Notch-Based Miniaturized Multi-Transmission-Zero Balanced Dual-Band Bandpass Filter

Abstract

The present invention discloses a miniaturized multi-transmission zero balanced dual-band bandpass filter based on notch, specifically including: a differential structure parallel two-wire input port A, a differential structure parallel two-wire output port B, a dielectric substrate, two sections of annular double-sided differential signal transmission lines, two sections of straight double-sided differential signal transmission lines, two groups of inverting connection structures, two groups of double-sided hairpin-type coupled lines, two sections of double-sided terminated open stubs, two sections of double-sided high-impedance transmission lines, one section of double-sided low-impedance transmission line, one group of double-sided grounding structures, and one group of double-sided terminated short-circuit parallel coupled lines. The present invention realizes the high-performance dual-band broadband bandpass filtering characteristics of multi-transmission zeros and high out-of-band rejection for differential-mode signals, and introduces notch characteristics into the balanced filter structure, thereby suppressing the interference signals between the high- and low-pass frequency bands. Therefore, it is very suitable for application in various balanced microwave systems to improve the overall performance of the system.

Description

Technical Field

[0001] The present invention relates to a balanced dual - band band - pass filter, and more particularly to a miniaturized multi - transmission - zero balanced dual - band band - pass filter based on notch filtering. Background Art

[0002] In modern wireless communication systems, balanced circuits play an important role. Compared with unbalanced single - port input - output circuits, balanced circuits can efficiently suppress environmental noise and noise generated by internal active devices, and thus have superior electromagnetic compatibility characteristics. A variety of radio - frequency and microwave devices, such as filters, mixers, and power amplifiers, etc., are widely designed in balanced topological structures. With the rapid development of integrated circuits, the demand for balanced devices will be more urgent. A balanced filter has filtering characteristics when a differential - mode signal is input, and can effectively suppress common - mode noise. A balanced filter can be simply constructed by a single - port filter and two baluns, but its area is huge. Therefore, it is very important to design a balanced filter as a single device without adding an extra balun, which has broad application prospects.

[0003] A notch filter is a filter that can rapidly attenuate an input signal within a relatively narrow frequency band to prevent the signal in this frequency band from passing through. It is usually used in the design of ultra - wideband filters to filter out interference - band signals within the passband. However, most of the existing research on notch filters is based on the premise of ultra - wideband technology application, and then band - stop stubs are introduced on the basis of the ultra - wideband filter structure to achieve the notch effect. There are few studies on designing a notch filter as an independent passive device. Therefore, more or less, the existing notch filters have many problems such as a relatively large filter structure size, poor selectivity, a not - steep enough transition band near the notch frequency band within the passband, and poor out - of - band rejection of the overall filter. Therefore, it is of great significance to study a miniaturized notch filter with high - performance differential - mode filtering characteristics and at the same time capable of achieving common - mode suppression. In view of this, it is necessary to propose a miniaturized multi - transmission - zero balanced dual - band band - pass filter based on notch filtering. Summary of the Invention

[0004] According to the problems existing in the prior art, the present invention discloses a miniaturized multi - transmission - zero balanced dual - band band - pass filter based on notch filtering, specifically including:

[0005] A differential - structure parallel - two - wire input port A, a differential - structure parallel - two - wire output port B, a dielectric substrate, two sections of annular double - sided differential - signal transmission lines, two sections of straight - line double - sided differential - signal transmission lines, two groups of in - phase - connection structures, two groups of double - sided hairpin - type coupled lines, two sections of double - sided open - circuited stubs, two sections of double - sided high - impedance transmission lines, one section of double - sided low - impedance transmission line, one group of double - sided grounded structures, and one group of double - sided short - circuited parallel - coupled lines;

[0006] The differential structure parallel two-wire input port A includes an input port A+ and an input port A-.

[0007] The differential structure parallel two-wire output port B includes an output port B+ and an output port B-.

[0008] The two-section ring-shaped double-sided differential signal transmission lines include a first ring-shaped double-sided differential signal transmission line and a second ring-shaped double-sided differential signal transmission line; one end of the first ring-shaped double-sided differential signal transmission line is connected to the input port A+, and the other end is connected to the connection point between the inverting connection combination I and the double-sided hairpin line combination I; one end of the second ring-shaped double-sided differential signal transmission line is connected to the output port B+, and the other end is connected to the connection point between the inverting connection combination II and the double-sided hairpin line combination II.

[0009] The two-section straight-line double-sided differential signal transmission lines include a first straight-line double-sided differential signal transmission line and a second straight-line double-sided differential signal transmission line; one end of the first straight-line double-sided differential signal transmission line is connected to the input port A-, and the other end is connected to the inverting connection combination I; one end of the second straight-line double-sided differential signal transmission line is connected to the output port B-, and the other end is connected to the inverting connection combination II.

[0010] The two groups of inverting connection structures include an inverting connection combination I and an inverting connection combination II; one end of the inverting connection combination I is connected to the first ring-shaped double-sided differential signal transmission line, and the other end is connected to the first straight-line double-sided differential signal transmission line; one end of the inverting connection combination II is connected to the second ring-shaped double-sided differential signal transmission line, and the other end is connected to the second straight-line double-sided differential signal transmission line.

[0011] The two groups of double-sided hairpin-type coupled lines include a double-sided hairpin line combination I and a double-sided hairpin line combination II; the double-sided hairpin line combination I and the double-sided hairpin line combination II have the same structure; the double-sided hairpin line combination I includes a double-sided hairpin line combination I outer coupled line and a double-sided hairpin line combination I inner coupled line; the double-sided hairpin line combination II includes a double-sided hairpin line combination II outer coupled line and a double-sided hairpin line combination II inner coupled line; wherein the double-sided hairpin line combination I outer coupled line is connected to the connection point between the first ring-shaped double-sided differential signal transmission line and the double-sided terminal short-circuited parallel coupled line; the double-sided hairpin line combination I inner coupled line is connected to the first double-sided high-impedance transmission line.

[0012] The two-section double-sided terminal open stub lines include a first double-sided terminal open stub line and a second double-sided terminal open stub line; the first double-sided terminal open stub line is connected to the double-sided hairpin line combination I outer coupled line; the second double-sided terminal open stub line is connected to the double-sided hairpin line combination II outer coupled line.

[0013] The two-section double-sided high-impedance transmission line includes a first double-sided high-impedance transmission line and a second double-sided high-impedance transmission line; one end of the first double-sided high-impedance transmission line is connected to the inner coupled line of the double-sided hairpin line combination I, and the other end is connected to the double-sided low-impedance transmission line; one end of the second double-sided high-impedance transmission line is connected to the inner coupled line of the double-sided hairpin line combination II, and the other end is connected to the double-sided low-impedance transmission line;

[0014] One end of the one-section double-sided low-impedance transmission line is connected to the first double-sided high-impedance transmission line, and the other end is connected to the second double-sided high-impedance transmission line;

[0015] The group of double-sided grounding structures is connected to the center of the double-sided low-impedance transmission line;

[0016] One end of the group of double-sided terminally shorted parallel coupled lines is connected to the double-sided hairpin line combination I, and the other end is connected to the double-sided hairpin line combination II.

[0017] Furthermore, by adjusting the coupling coefficients of the two groups of double-sided hairpin coupled lines, the passband bandwidth of the filter is controlled and adjusted.

[0018] Furthermore, by adjusting the coupling length and coupling coefficients of the double-sided terminally shorted parallel coupled lines, the positions of the transmission zeros and the stopband rejection capabilities of the lower and upper stopbands of the filter are controlled and adjusted.

[0019] Furthermore, by adjusting the lengths and widths of the two sections of double-sided open-circuited stubs, the positions and notch depths of the two notch points between the two passbands are controlled and adjusted.

[0020] In order to miniaturize the balanced filter as a single device and achieve high-performance dual-band filtering of differential-mode signals while achieving common-mode suppression, the present invention provides a notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter. In addition to the function of suppressing common-mode noise, this balanced filter realizes high-performance dual-band bandpass filtering characteristics with multi-transmission zeros for the input differential-mode signals, and notch characteristics are introduced in the structure of the balanced filter to suppress the interference signals in the useless frequency bands between the high- and low-pass frequency bands. In addition, this balanced filter also has the characteristics of simple structure, small circuit size, and high out-of-band rejection, solving many problems existing in the current balanced notch filters, such as large circuit size, poor filtering selectivity, insufficiently steep transition band near the notch frequency band, and poor out-of-band rejection of the overall filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0022] Figure 1 is a schematic structural diagram of a notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter according to the present invention;

[0023] Figure 2 is a hybrid S-parameter amplitude curve diagram of the notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter of the present invention under differential-mode signal excitation;

[0024] Figure 3 is a hybrid S-parameter amplitude curve diagram of the notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter of the present invention under common-mode signal excitation. Detailed Embodiments

[0025] To make the technical solutions and advantages of the present invention clearer, 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:

[0026] As Figure 1 shown, a notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter specifically includes: a differential structure parallel two-wire input port A, a differential structure parallel two-wire output port B, a dielectric substrate 5, two sections of annular double-sided differential signal transmission lines, two sections of straight double-sided differential signal transmission lines, two groups of inverting connection structures 10, two groups of double-sided hairpin-type coupled lines, two sections of double-sided terminated open stubs, two sections of double-sided high-impedance transmission lines, one section of double-sided low-impedance transmission line 17, one group of double-sided grounding structures 18, and one group of double-sided terminated short-circuited parallel coupled lines 19;

[0027] The differential structure parallel two-wire input port A includes an input port A+1 and an input port A-2;

[0028] The differential structure parallel two-wire output port B includes an output port B+3 and an output port B-4;

[0029] The two-section annular double-sided differential signal transmission line includes a first annular double-sided differential signal transmission line 6 and a second annular double-sided differential signal transmission line 7; one end of the first annular double-sided differential signal transmission line 6 is connected to the input port A+1, and the other end is connected to the connection point between the inverting connection combination I 101 and the double-sided hairpin line combination I 11; one end of the second annular double-sided differential signal transmission line 7 is connected to the output port B+3, and the other end is connected to the connection point between the inverting connection combination II 102 and the double-sided hairpin line combination II 12;

[0030] The two-section straight double-sided differential signal transmission line includes a first straight double-sided differential signal transmission line 8 and a second straight double-sided differential signal transmission line 9; one end of the first straight double-sided differential signal transmission line 8 is connected to the input port A-2, and the other end is connected to the inverting connection combination I 101; one end of the second straight double-sided differential signal transmission line 9 is connected to the output port B-4, and the other end is connected to the inverting connection combination II 102;

[0031] The two sets of inverting connection structures 10 include an inverting connection combination I 101 and an inverting connection combination II 102; one end of the inverting connection combination I 101 is connected to the first annular double-sided differential signal transmission line 6, and the other end is connected to the first straight double-sided differential signal transmission line 8; one end of the inverting connection combination II 102 is connected to the second annular double-sided differential signal transmission line 7, and the other end is connected to the second straight double-sided differential signal transmission line 9;

[0032] The two sets of double-sided hairpin coupled lines include a double-sided hairpin line combination I 11 and a double-sided hairpin line combination II 12; the double-sided hairpin line combination I 11 and the double-sided hairpin line combination II 12 have the same structure; the double-sided hairpin line combination I 11 includes a double-sided hairpin line combination I outer coupled line 111 and a double-sided hairpin line combination I inner coupled line 112; the double-sided hairpin line combination II 12 includes a double-sided hairpin line combination II outer coupled line 121 and a double-sided hairpin line combination II inner coupled line 122; wherein the double-sided hairpin line combination I outer coupled line 111 is connected to the connection point between the first annular double-sided differential signal transmission line 6 and the double-sided terminal short-circuited parallel coupled line 19; the double-sided hairpin line combination I inner coupled line 112 is connected to the first double-sided high impedance transmission line 15;

[0033] The two-section double-sided terminal open stub lines include a first double-sided terminal open stub line 13 and a second double-sided terminal open stub line 14; the first double-sided terminal open stub line 13 is connected to the double-sided hairpin line combination I outer coupled line 111; the second double-sided terminal open stub line 14 is connected to the double-sided hairpin line combination II outer coupled line 121;

[0034] The two-segment double-sided high-impedance transmission line includes a first double-sided high-impedance transmission line 15 and a second double-sided high-impedance transmission line 16; one end of the first double-sided high-impedance transmission line 15 is connected to the inner coupled line 112 of the double-sided hairpin line combination I, and the other end is connected to the double-sided low-impedance transmission line 17; one end of the second double-sided high-impedance transmission line 16 is connected to the inner coupled line 122 of the double-sided hairpin line combination II, and the other end is connected to the double-sided low-impedance transmission line 17;

[0035] One end of the one-segment double-sided low-impedance transmission line 17 is connected to the first double-sided high-impedance transmission line 15, and the other end is connected to the second double-sided high-impedance transmission line 16;

[0036] A group of double-sided grounding structures 18 are connected to the center of the double-sided low-impedance transmission line 17;

[0037] One end of a group of double-sided terminally shorted parallel coupled lines 19 is connected to the double-sided hairpin line combination I 11, and the other end is connected to the double-sided hairpin line combination II 12.

[0038] By adjusting the coupling coefficients of the two groups of double-sided hairpin-type coupled lines, the passband bandwidth of the filter is controlled and adjusted.

[0039] By adjusting the coupling length and coupling coefficient of the double-sided terminally shorted parallel coupled line 19, the transmission zero positions and stopband rejection capabilities of the lower stopband and upper stopband of the filter are controlled and adjusted.

[0040] By adjusting the lengths and widths of the two-segment double-sided terminally open stubs, the positions and notch depths of the two notch points between the two passbands are controlled and adjusted.

[0041] Embodiment:

[0042] To further illustrate the notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter provided by the present invention, the following is a detailed description of specific examples implemented on the premise of the technical solution of the present invention. However, the protection scope of the present invention is not limited to the following embodiments. The methods used in the following embodiments are all conventional methods unless otherwise specified.

[0043] Specific example: This example lists a notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter. As Figure 2 shown, the notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter described in the present invention introduces a second-order notch characteristic under the excitation of the differential-mode signal at the center frequency of 3 GHz. In the notch frequency band from 2.84 GHz to 3.30 GHz, the differential-mode signal suppression level is better than 20 dB; under the excitation of the differential-mode signal, the minimum differential-mode transmission loss |S ddBA | in the low-frequency band of the filter is -0.35 dB, and the reflection coefficient |SddAA is -14.2 dB, the 3 dB relative bandwidth of the low-frequency band of the filter is 44.7%, and the minimum differential-mode transmission loss in the high-frequency band of the filter ddBA is -0.45 dB, and the reflection coefficient at the center frequency of 4.05 GHz in the high-frequency band ddAA is -15.9 dB, and the 3 dB relative bandwidth of the high-frequency band of the filter is 34.9%; in the frequency ranges of the lower stopband 0 - 1.52 GHz and the upper stopband 5.15 - 7.0 GHz, the out-of-band rejection level of the differential-mode signal is better than 20 dB, and at the same time near the differential-mode passband of the filter ddBA there are five transmission zeros, located at the frequencies of 1.44 GHz, 2.98 GHz, 3.28 GHz, 5.31 GHz, and 6.46 GHz respectively, improving the differential-mode filtering performance. As Figure 3 shown, in the case of common-mode signal excitation, the common-mode transmission suppression of the notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter described in the present invention ccBA is less than -34 dB in the entire frequency range of 0 - 7 GHz, having excellent common-mode rejection ability. It shows that the notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter described in the present invention not only well suppresses common-mode noise but also realizes the dual-band wideband bandpass filtering characteristics of multi-transmission zeros and high out-of-band rejection for differential-mode signals, and introduces a notch characteristic between the high- and low-pass frequency bands to suppress interference signals in the useless frequency bands.

[0044] In summary, the notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter described in the present invention can effectively suppress common-mode noise, and at the same time realizes the high-performance dual-band wideband bandpass filtering characteristics of multi-transmission zeros and high out-of-band rejection for differential-mode signals, and introduces a notch characteristic into the balanced filter structure, thereby suppressing interference signals between the high- and low-pass frequency bands. Therefore, it is very suitable for application in various balanced microwave systems to improve the overall performance of the system.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter, characterized in that, Comprising: A differential - structure parallel - twin - line input port A, a differential - structure parallel - twin - line output port B, a dielectric substrate (5), two sections of annular double - sided differential - signal transmission lines, two sections of straight - line double - sided differential - signal transmission lines, two groups of inverting connection structures (10), two groups of double - sided hairpin - type coupled lines, two sections of double - sided open - circuited stubs, two sections of double - sided high - impedance transmission lines, one section of double - sided low - impedance transmission line (17), one group of double - sided grounding structures (18), and one group of double - sided terminally - short - circuited parallel - coupled lines (19); The differential - structure parallel - twin - line input port A includes an input port A+(1) and an input port A-(2); The differential - structure parallel - twin - line output port B includes an output port B+(3) and an output port B-(4); The two sections of annular double - sided differential - signal transmission lines include a first annular double - sided differential - signal transmission line (6) and a second annular double - sided differential - signal transmission line (7); One end of the first annular double - sided differential - signal transmission line (6) is connected to the input port A+(1), and the other end is connected to the connection point of the inverting connection combination Ⅰ(101) and the double - sided hairpin - line combination Ⅰ(11); One end of the second annular double - sided differential - signal transmission line (7) is connected to the output port B+(3), and the other end is connected to the connection point of the inverting connection combination Ⅱ(102) and the double - sided hairpin - line combination Ⅱ(12); The two sections of straight - line double - sided differential - signal transmission lines include a first straight - line double - sided differential - signal transmission line (8) and a second straight - line double - sided differential - signal transmission line (9); One end of the first straight - line double - sided differential - signal transmission line (8) is connected to the input port A-(2), and the other end is connected to the inverting connection combination Ⅰ(101); One end of the second straight - line double - sided differential - signal transmission line (9) is connected to the output port B-(4), and the other end is connected to the inverting connection combination Ⅱ(102); The two groups of inverting connection structures (10) include an inverting connection combination Ⅰ(101) and an inverting connection combination Ⅱ(102); One end of the inverting connection combination Ⅰ(101) is connected to the first annular double - sided differential - signal transmission line (6), and the other end is connected to the first straight - line double - sided differential - signal transmission line (8); One end of the inverting connection combination Ⅱ(102) is connected to the second annular double - sided differential - signal transmission line (7), and the other end is connected to the second straight - line double - sided differential - signal transmission line (9); The two sets of double-sided hairpin-type coupled lines include double-sided hairpin line combination I (11) and double-sided hairpin line combination II (12); the double-sided hairpin line combination I (11) and the double-sided hairpin line combination II (12) have the same structure; the double-sided hairpin line combination I (11) includes the double-sided hairpin line combination I outer coupled line (111) and the double-sided hairpin line combination I inner coupled line (112); the double-sided hairpin line combination II (12) includes the double-sided hairpin line combination II outer coupled line (121) and the double-sided hairpin line combination II inner coupled line (122); wherein the double-sided hairpin line combination I outer coupled line (111) is connected to the connection point of the first ring-shaped double-sided differential signal transmission line (6) and the double-sided terminal short-circuited parallel coupled line (19); the double-sided hairpin line combination I inner coupled line (112) is connected to the first double-sided high-impedance transmission line (15). The two sections of double-sided open-circuit stubs include the first double-sided open-circuit stub (13) and the second double-sided open-circuit stub (14); the first double-sided open-circuit stub (13) is connected to the double-sided hairpin line combination I outer coupled line (111); the second double-sided open-circuit stub (14) is connected to the double-sided hairpin line combination II outer coupled line (121). The two sections of double-sided high-impedance transmission lines include the first double-sided high-impedance transmission line (15) and the second double-sided high-impedance transmission line (16); one end of the first double-sided high-impedance transmission line (15) is connected to the double-sided hairpin line combination I inner coupled line (112), and the other end is connected to the double-sided low-impedance transmission line (17); one end of the second double-sided high-impedance transmission line (16) is connected to the double-sided hairpin line combination II inner coupled line (122), and the other end is connected to the double-sided low-impedance transmission line (17). One section of the double-sided low-impedance transmission line (17) has one end connected to the first double-sided high-impedance transmission line (15) and the other end connected to the second double-sided high-impedance transmission line (16). One set of double-sided grounding structures (18) is connected to the center of the double-sided low-impedance transmission line (17). One set of double-sided terminal short-circuited parallel coupled lines (19) has one end connected to the double-sided hairpin line combination I (11) and the other end connected to the double-sided hairpin line combination II (12).

2. The notch-based miniaturized multi-transmission-zero balanced dual-band bandpass filter according to claim 1, wherein: By adjusting the coupling coefficient of the two sets of double-sided hairpin-type coupled lines, the passband bandwidth of the filter is controlled and adjusted.

3. The notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter according to claim 1, characterized in that: By adjusting the coupling length and coupling coefficient of the double-sided terminal short-circuited parallel coupled line (19), the positions of the transmission zeros and the stopband rejection ability of the lower stopband and the upper stopband of the filter are controlled and adjusted.

4. The notch-based miniaturized multi-transmission zero balanced dual-band bandpass filter according to claim 1, characterized in that: By adjusting the length and width of the two sections of double-sided open-circuit stubs, the positions and notch depths of the two notch points between the two passbands are controlled and adjusted.

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