A balanced band-pass filter with single / dual / triple-band switchable function

Abstract

The application discloses a balanced band-pass filter with single / dual / triple-band switchable function, comprising a balanced differential input port A, a balanced differential output port B, two half-wavelength reverse transmission lines, four quarter-wavelength terminal short-circuit parallel coupling lines, two half-wavelength resonant microstrip lines, two semiconductor PIN diodes, two bypass capacitors, two voltage dividing resistors and two DC power supplies. The balanced band-pass filter can be realized on a single PCB board, and has simple structure and is conducive to processing integration. In addition, the filter can not only effectively suppress common-mode noise and improve the electromagnetic compatibility characteristics of a communication system, but also realize the single / dual / triple-band mode switchable function under differential-mode signal excitation by loading only two semiconductor diodes, thereby improving the overall performance of the balanced band-pass filter, so as to meet the demand of a radio frequency terminal communication system for multiple working frequencies, multiple working modes and working under a complex electromagnetic environment.

Description

Technical Field

[0001] This invention relates to a balanced bandpass filter, specifically a balanced bandpass filter with switchable single / dual / triple passband functionality. Background Technology

[0002] Balanced circuits play a crucial role in modern wireless communication systems. Compared to unbalanced single-port input / output circuits, balanced circuits can efficiently suppress ambient noise and noise generated by internal active components, thus exhibiting superior electromagnetic compatibility characteristics. Various RF microwave devices, such as filters, mixers, and power amplifiers, are widely designed with balanced topologies. With the rapid development of integrated circuits, the demand for balanced devices will become even more urgent. Balanced filters possess filtering characteristics for differential-mode signal inputs while effectively suppressing common-mode noise. While a balanced filter can be easily constructed using a single-port filter and two baluns, its size is enormous. Therefore, it is essential to design the balanced filter as a single device without adding additional baluns.

[0003] As modern wireless communication systems evolve towards higher integration, higher demands are placed on the performance of microwave passive devices with reconfigurable capabilities, aiming to achieve more functions within limited circuit space and cost. Therefore, various reconfigurable components, such as reconfigurable power dividers, couplers, duplexers, antennas, and filters, are being researched to meet the application requirements of radio frequency (RF) front-ends. Reconfigurable bandpass filters, due to their ability to transmit signals and suppress unwanted interference, can meet the needs of operating at multiple frequencies, in multiple modes, and under complex electromagnetic environments in RF terminal circuits, playing a crucial role in communication systems. Consequently, in recent years, scholars have conducted in-depth research on various reconfigurable bandpass filters. Among these methods, loading semiconductor diodes into microstrip filters is one of the simplest and lowest-cost ways to achieve functional reconfiguration, showing broad application prospects.

[0004] However, current research on reconfigurable bandpass filters in both academic and industrial fields mainly focuses on the switchability of the passband and its tunability in the frequency domain. Research on bandpass filters with multi-mode switchable passbands remains scarce. Furthermore, most reconfigurable bandpass filters suffer from an excessive number of semiconductor diodes. Research on balanced reconfigurable bandpass filters is even rarer. Therefore, researching balanced reconfigurable bandpass filters that achieve common-mode rejection while simultaneously enabling switchable differential-mode single / dual / triple passband modes is of great significance. In view of this, it is indeed necessary to propose a balanced bandpass filter with single / dual / triple passband switchability. Summary of the Invention

[0005] Based on this, and to address the shortcomings of existing technologies, a balanced bandpass filter with switchable single / dual / triple pass functionality is proposed.

[0006] Based on the above objectives, the technical solution of the present invention includes: a balanced differential input port A, a balanced differential output port B, two half-wavelength anti-phase transmission lines, four quarter-wavelength short-circuited parallel coupling lines, two half-wavelength resonant microstrip lines, two semiconductor PIN diodes, two bypass capacitors, two voltage divider resistors, and two DC power supplies.

[0007] The balanced differential input port A includes input port A+ and input port A-;

[0008] The balanced differential output port B includes output port B+ and output port B-;

[0009] The two half-wavelength anti-phase transmission lines include a first anti-phase transmission line and a second anti-phase transmission line; wherein one end of the first anti-phase transmission line is connected to the input port A+ and the other end is connected to the input port A-; one end of the second anti-phase transmission line is connected to the output port B+ and the other end is connected to the output port B-.

[0010] The four quarter-wavelength terminated short-circuit parallel coupling lines include a first terminated short-circuit parallel coupling line, a second terminated short-circuit parallel coupling line, a third terminated short-circuit parallel coupling line, and a fourth terminated short-circuit parallel coupling line. One end of the first terminated short-circuit parallel coupling line is connected to the connection between the input port A+ and the first inverting transmission line, and the other end is connected to the connection between the third terminated short-circuit parallel coupling line and the first resonant microstrip line. One end of the second terminated short-circuit parallel coupling line is connected to the connection between the input port A- and the first inverting transmission line, and the other end is connected to the connection between the fourth terminated short-circuit parallel coupling line and the second resonant microstrip line. One end of the third terminated short-circuit parallel coupling line is connected to the connection between the output port B+ and the second inverting transmission line, and the other end is connected to the connection between the first terminated short-circuit parallel coupling line and the first resonant microstrip line. One end of the fourth terminated short-circuit parallel coupling line is connected to the connection between the output port B- and the second inverting transmission line, and the other end is connected to the connection between the second terminated short-circuit parallel coupling line and the second resonant microstrip line.

[0011] The two half-wavelength resonant microstrip lines include a first resonant microstrip line and a second resonant microstrip line; wherein one end of the first resonant microstrip line is connected to the connection between the first terminal short-circuit parallel coupling line and the third terminal short-circuit parallel coupling line, and the other end is connected to the negative terminal of the first PIN diode; one end of the second resonant microstrip line is connected to the connection between the second terminal short-circuit parallel coupling line and the fourth terminal short-circuit parallel coupling line, and the other end is connected to the negative terminal of the second PIN diode;

[0012] The two semiconductor PIN diodes include a first PIN diode and a second PIN diode; wherein the negative terminal of the first PIN diode is connected to the first resonant microstrip line, and the positive terminal of the first PIN diode is connected to the connection between the first bypass capacitor and the first voltage divider resistor; the negative terminal of the second PIN diode is connected to the second resonant microstrip line, and the positive terminal of the second PIN diode is connected to the connection between the second bypass capacitor and the second voltage divider resistor.

[0013] The two bypass capacitors include a first bypass capacitor and a second bypass capacitor; wherein one end of the first bypass capacitor is connected to the connection between the positive terminal of the first PIN diode and the first voltage divider resistor, and the other end is grounded; one end of the second bypass capacitor is connected to the connection between the positive terminal of the second PIN diode and the second voltage divider resistor, and the other end is grounded;

[0014] The two voltage divider resistors include a first voltage divider resistor and a second voltage divider resistor; wherein one end of the first voltage divider resistor is connected to the connection between the positive terminal of the first PIN diode and the first bypass capacitor, and the other end is connected to the first DC power supply; one end of the second voltage divider resistor is connected to the connection between the positive terminal of the second PIN diode and the second bypass capacitor, and the other end is connected to the second DC power supply.

[0015] The two DC power supplies include a first DC power supply and a second DC power supply; wherein the first DC power supply is connected to a first voltage divider resistor; and the second DC power supply is connected to a second voltage divider resistor.

[0016] Furthermore, by adjusting the output voltage V of the first DC power supply p1 The output voltage V of the second DC power supply p2 The first PIN diode and the second PIN diode are controlled to turn on / off, thereby enabling the switching function of the balanced bandpass filter in single / dual / triple passband modes.

[0017] Furthermore, by adjusting the first terminal short-circuit parallel coupling line, the second terminal short-circuit parallel coupling line, the third terminal short-circuit parallel coupling line, and the fourth terminal short-circuit parallel coupling line, the filtering bandwidth and frequency selectivity of the balanced bandpass filter can be adjusted.

[0018] Furthermore, the common-mode rejection characteristics of the balanced bandpass filter can be adjusted by modifying the first and second inverting transmission lines.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] To design balanced filters as a single device and address the current shortcomings in research on balanced reconfigurable bandpass filters, this invention provides a balanced bandpass filter with switchable single / dual / triple passband functionality. This balanced bandpass filter can be implemented on a single PCB board, featuring a simple structure that facilitates fabrication and integration. Furthermore, this filter effectively suppresses common-mode noise, improving the electromagnetic compatibility of communication systems. It also achieves switchable single / dual / triple passband modes under differential-mode signal excitation with only two semiconductor diodes, thereby enhancing the overall performance of the balanced bandpass filter to meet the requirements of RF terminal communication systems operating at various frequencies, in various modes, and under complex electromagnetic environments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a balanced bandpass filter with single / dual / triple pass bandpass switchable function according to the present invention;

[0023] Figure 2 This is a hybrid S-parameter amplitude curve of a balanced bandpass filter with single / dual / triple passband switchable function under differential mode signal excitation in single passband mode according to the present invention.

[0024] Figure 3 This is a hybrid S-parameter amplitude curve of a balanced bandpass filter with single / dual / triple passband switchable function under differential mode signal excitation in dual passband mode according to the present invention.

[0025] Figure 4 This is a mixed S-parameter amplitude curve of a balanced bandpass filter with single / dual / triple passband switchable function under differential mode signal excitation in the triple passband mode of the present invention;

[0026] Figure 5 This is a mixed S-parameter amplitude curve of a balanced bandpass filter with single / dual / triple passband switchable function under common-mode signal excitation, showing the three switchable modes of single / dual / triple passband. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] The present invention provides a balanced bandpass filter with single / dual / triple bandpass switchable function, comprising: a balanced differential input port A, a balanced differential output port B, two half-wavelength anti-phase transmission lines, four quarter-wavelength short-circuited parallel coupling lines, two half-wavelength resonant microstrip lines, two semiconductor PIN diodes, two bypass capacitors, two voltage divider resistors, and two DC power supplies.

[0029] The balanced differential input port A includes input port A+1 and input port A-2;

[0030] The balanced differential output port B includes output port B+3 and output port B-4;

[0031] The two half-wavelength anti-phase transmission lines include a first anti-phase transmission line 5 and a second anti-phase transmission line 6; wherein one end of the first anti-phase transmission line 5 is connected to the input port A+1 and the other end is connected to the input port A-2; one end of the second anti-phase transmission line 6 is connected to the output port B+3 and the other end is connected to the output port B-4;

[0032] The four quarter-wavelength terminated short-circuit parallel coupling lines include a first terminated short-circuit parallel coupling line 7, a second terminated short-circuit parallel coupling line 8, a third terminated short-circuit parallel coupling line 9, and a fourth terminated short-circuit parallel coupling line 10; wherein one end of the first terminated short-circuit parallel coupling line 7 is connected to the connection between the input port A+1 and the first inverting transmission line 5, and the other end is connected to the connection between the third terminated short-circuit parallel coupling line 9 and the first resonant microstrip line 11; one end of the second terminated short-circuit parallel coupling line 8 is connected to the connection between the input port A-2 and the first inverting transmission line 5. One end of the third terminal short-circuited parallel coupling line 9 is connected to the connection between the output port B+3 and the second inverting transmission line 6, and the other end is connected to the connection between the first terminal short-circuited parallel coupling line 7 and the first resonant microstrip line 11; one end of the fourth terminal short-circuited parallel coupling line 10 is connected to the connection between the output port B-4 and the second inverting transmission line 6, and the other end is connected to the connection between the second terminal short-circuited parallel coupling line 8 and the second resonant microstrip line 12.

[0033] The two half-wavelength resonant microstrip lines include a first resonant microstrip line 11 and a second resonant microstrip line 12; wherein one end of the first resonant microstrip line 11 is connected to the connection between the first terminal short-circuit parallel coupling line 7 and the third terminal short-circuit parallel coupling line 9, and the other end is connected to the negative terminal of the first PIN diode 13; one end of the second resonant microstrip line 12 is connected to the connection between the second terminal short-circuit parallel coupling line 8 and the fourth terminal short-circuit parallel coupling line 10, and the other end is connected to the negative terminal of the second PIN diode 14;

[0034] The two semiconductor PIN diodes include a first PIN diode 13 and a second PIN diode 14; wherein the cathode of the first PIN diode 13 is connected to the first resonant microstrip line 11, and the anode of the first PIN diode 13 is connected to the connection between the first bypass capacitor 15 and the first voltage divider resistor 17; the cathode of the second PIN diode 14 is connected to the second resonant microstrip line 12, and the anode of the second PIN diode 14 is connected to the connection between the second bypass capacitor 16 and the second voltage divider resistor 18.

[0035] The two bypass capacitors include a first bypass capacitor 15 and a second bypass capacitor 16; wherein one end of the first bypass capacitor 15 is connected to the connection between the positive terminal of the first PIN diode 13 and the first voltage divider resistor 17, and the other end is grounded; one end of the second bypass capacitor 16 is connected to the connection between the positive terminal of the second PIN diode 14 and the second voltage divider resistor 18, and the other end is grounded.

[0036] The two voltage divider resistors include a first voltage divider resistor 17 and a second voltage divider resistor 18; wherein one end of the first voltage divider resistor 17 is connected to the connection between the positive terminal of the first PIN diode 13 and the first bypass capacitor 15, and the other end is connected to the first DC power supply 19; one end of the second voltage divider resistor 18 is connected to the connection between the positive terminal of the second PIN diode 14 and the second bypass capacitor 16, and the other end is connected to the second DC power supply 20;

[0037] The two DC power supplies include a first DC power supply 19 and a second DC power supply 20; wherein the first DC power supply 19 is connected to a first voltage divider resistor 17; and the second DC power supply 20 is connected to a second voltage divider resistor 18.

[0038] By adjusting the output voltage V of the first DC power supply 19 p1 The output voltage V of the second DC power supply 20 p2 The first PIN diode 13 and the second PIN diode 14 are controlled to turn on / off respectively, thereby realizing the switching function of single / dual / triple passband mode of balanced bandpass filter.

[0039] The filtering bandwidth and frequency selectivity of the balanced bandpass filter can be adjusted by adjusting the first terminal short-circuit parallel coupling line 7, the second terminal short-circuit parallel coupling line 8, the third terminal short-circuit parallel coupling line 9, and the fourth terminal short-circuit parallel coupling line 10.

[0040] The common-mode rejection characteristics of the balanced bandpass filter are adjusted by adjusting the first inverting transmission line 5 and the second inverting transmission line 6.

[0041] To further illustrate the balanced bandpass filter with single / dual / triple bandpass switchable function provided by the present invention, specific examples of implementation based on the technical solution of the present invention are described in detail below. However, the scope of protection of the present invention is not limited to the following embodiments, and the methods used in the following embodiments are conventional methods unless otherwise specified.

[0042] Specific example: This example illustrates a balanced bandpass filter with switchable single / dual / triple pass functionality. For example... Figure 2 As shown, the reflection coefficient |S| of a balanced bandpass filter with single / dual / triple passband switchable function described in this invention at the center frequency of 1.0 GHz in single passband mode under differential mode signal excitation. ddAA |The minimum differential-mode transmission loss within the filter band is -21.7dB|S ddBA The value is -0.23dB, and the filter's 3dB transmission bandwidth is 15.0%. For example... Figure 3 As shown, the reflection coefficient |S| of a balanced bandpass filter with single / dual / triple passband switchable function described in this invention at the center frequency of 0.76 GHz in the low-frequency band of the dual passband mode under differential mode excitation is... ddAA |The minimum differential mode transmission loss in the low-frequency band of the filter is -21.0dB|S ddBA The reflection coefficient at the center frequency of 1.26 GHz in the high-frequency band of the dual-passband mode is -0.73 dB, with a relative bandwidth of 5.2% for the 3 dB transmission. ddAA |The minimum differential-mode transmission loss in the high-frequency band of the filter is -20.4dB|S ddBA The value is -0.83dB, and the relative bandwidth of the filter's 3dB transmission is 4.0%. For example... Figure 4 As shown, the reflection coefficient |S| of a balanced bandpass filter with single / dual / triple passband switchable function described in this invention at the low-frequency center frequency of 0.78GHz in triple passband mode under differential mode signal excitation. ddAA |15.6dB, minimum differential mode transmission loss in the low-frequency band of the filter|S ddBA | is -1.58dB, the relative bandwidth of the filter's 3dB transmission is 3.8% in the low-frequency band; the reflection coefficient at the center frequency of 1.0GHz in the three-passband mode is |S ddAA|The minimum differential mode transmission loss in the mid-frequency band of the filter is -23.0dB|S ddBA The reflection coefficient is -0.44dB, and the relative bandwidth of the filter's 3dB transmission in the mid-frequency band is 7.0%; the reflection coefficient at the center frequency of 1.25GHz in the high-frequency band of the three-pass mode is |S ddAA |15.2dB, minimum differential mode transmission loss in the high-frequency band of the filter|S ddBA The value is -1.53dB, and the relative bandwidth of the filter's 3dB transmission in the high-frequency band is 2.4%. For example... Figure 5 As shown, the present invention relates to a balanced bandpass filter with single / dual / triple passband switchable function, and its in-band common-mode transmission suppression in single passband mode |S ccBA | Less than -33.8dB, in-band common-mode transmission rejection in dual-band dual-passband mode|S ccBA All are less than -21.4dB, in-band common-mode transmission rejection in three frequency bands in three-passband mode |S ccBA All values ​​are less than -26.2 dB. This indicates that the balanced bandpass filter with single / dual / triple passband switching function described in this invention not only suppresses common-mode noise, but also realizes the single / dual / triple passband mode switching function under differential-mode signal excitation.

[0043] In summary, the balanced bandpass filter with single / dual / triple pass switchable function described in this invention not only effectively suppresses common-mode noise and possesses superior electromagnetic compatibility characteristics, but also achieves single / dual / triple pass mode switchability under differential-mode signal excitation with only two semiconductor diodes loaded, thus meeting the needs of RF terminal communication systems operating at multiple frequencies, in multiple modes, and under complex electromagnetic environments. Furthermore, the balanced bandpass filter with single / dual / triple pass switchable function described in this invention can be implemented on a single PCB board, resulting in a simple structure that facilitates fabrication and integration. Therefore, it is highly suitable for application in various balanced microwave systems to improve overall system performance.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A balanced bandpass filter with switchable single / dual / triple pass functionality, characterized in that, include: Balanced differential input port A, balanced differential output port B, two half-wavelength inverting transmission lines, four quarter-wavelength short-circuited parallel coupling lines, two half-wavelength resonant microstrip lines, two semiconductor PIN diodes, two bypass capacitors, two voltage divider resistors, and two DC power supplies. The balanced differential input port A includes input port A+(1) and input port A-(2); The balanced differential output port B includes output port B+(3) and output port B-(4); The two half-wavelength anti-phase transmission lines include a first anti-phase transmission line (5) and a second anti-phase transmission line (6); wherein one end of the first anti-phase transmission line (5) is connected to the input port A+ (1) and the other end is connected to the input port A- (2); one end of the second anti-phase transmission line (6) is connected to the output port B+ (3) and the other end is connected to the output port B- (4); The four quarter-wavelength terminated short-circuit parallel coupling lines include a first terminated short-circuit parallel coupling line (7), a second terminated short-circuit parallel coupling line (8), a third terminated short-circuit parallel coupling line (9), and a fourth terminated short-circuit parallel coupling line (10); wherein one end of the first terminated short-circuit parallel coupling line (7) is connected to the connection between the input port A+ (1) and the first inverted transmission line (5), and the other end is connected to the connection between the third terminated short-circuit parallel coupling line (9) and the first resonant microstrip line (11); one end of the second terminated short-circuit parallel coupling line (8) is connected to the connection between the input port A- (2) and the first inverted transmission line (5). One end of the third terminal short-circuited parallel coupling line (9) is connected to the connection between the output port B+ (3) and the second anti-phase transmission line (6), and the other end is connected to the connection between the first terminal short-circuited parallel coupling line (7) and the first resonant microstrip line (11); one end of the fourth terminal short-circuited parallel coupling line (10) is connected to the connection between the output port B- (4) and the second anti-phase transmission line (6), and the other end is connected to the connection between the second terminal short-circuited parallel coupling line (8) and the second resonant microstrip line (12); The two half-wavelength resonant microstrip lines include a first resonant microstrip line (11) and a second resonant microstrip line (12); wherein one end of the first resonant microstrip line (11) is connected to the connection between the first terminal short-circuit parallel coupling line (7) and the third terminal short-circuit parallel coupling line (9), and the other end is connected to the negative terminal of the first PIN diode (13); one end of the second resonant microstrip line (12) is connected to the connection between the second terminal short-circuit parallel coupling line (8) and the fourth terminal short-circuit parallel coupling line (10), and the other end is connected to the negative terminal of the second PIN diode (14); The two semiconductor PIN diodes include a first PIN diode (13) and a second PIN diode (14); wherein the negative terminal of the first PIN diode (13) is connected to the first resonant microstrip line (11), and the positive terminal of the first PIN diode (13) is connected to the connection between the first bypass capacitor (15) and the first voltage divider resistor (17); the negative terminal of the second PIN diode (14) is connected to the second resonant microstrip line (12), and the positive terminal of the second PIN diode (14) is connected to the connection between the second bypass capacitor (16) and the second voltage divider resistor (18); The two bypass capacitors include a first bypass capacitor (15) and a second bypass capacitor (16); wherein one end of the first bypass capacitor (15) is connected to the connection between the positive terminal of the first PIN diode (13) and the first voltage divider resistor (17), and the other end is grounded; one end of the second bypass capacitor (16) is connected to the connection between the positive terminal of the second PIN diode (14) and the second voltage divider resistor (18), and the other end is grounded; The two voltage divider resistors include a first voltage divider resistor (17) and a second voltage divider resistor (18); wherein one end of the first voltage divider resistor (17) is connected to the connection between the positive terminal of the first PIN diode (13) and the first bypass capacitor (15), and the other end is connected to the first DC power supply (19); one end of the second voltage divider resistor (18) is connected to the connection between the positive terminal of the second PIN diode (14) and the second bypass capacitor (16), and the other end is connected to the second DC power supply (20); The two DC power supplies include a first DC power supply (19) and a second DC power supply (20); wherein the first DC power supply (19) is connected to a first voltage divider resistor (17); and the second DC power supply (20) is connected to a second voltage divider resistor (18).

2. A balanced bandpass filter with single / dual / triple pass switchable function according to claim 1, characterized in that: By adjusting the output voltage V of the first DC power supply (19) p1 The output voltage V of the second DC power supply (20) p2 The first PIN diode (13) and the second PIN diode (14) are controlled to turn on / off respectively, thereby realizing the switching function of single / dual / triple passband mode of balanced bandpass filter.

3. A balanced bandpass filter with single / dual / triple pass switchable function according to claim 1, characterized in that: The filtering bandwidth and frequency selectivity of the balanced bandpass filter can be adjusted by adjusting the first terminal short-circuit parallel coupling line (7), the second terminal short-circuit parallel coupling line (8), the third terminal short-circuit parallel coupling line (9), and the fourth terminal short-circuit parallel coupling line (10).

4. A balanced bandpass filter with single / dual / triple pass switchable function according to claim 1, characterized in that: The common-mode rejection characteristics of the balanced bandpass filter are adjusted by adjusting the first inverted transmission line (5) and the second inverted transmission line (6).

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