A reconfigurable filtering phase shifter based on stub-loaded resonators

Abstract

The application provides a reconfigurable filter phase shifter based on branch loaded resonator, and belongs to the technical field of microwave and radio frequency. The reconfigurable filter phase shifter comprises a dielectric substrate, two L-shaped input microstrip lines which are symmetric about AA', a reference line on the middle of BB' and two pairs of main lines which are perpendicular to BB' and are located on the two sides of the dielectric substrate; the reference line is composed of a group of symmetric and same-structure two-step microstrip lines and a terminal bent T-shaped microstrip line which is coupled to the two-step microstrip lines; the main line is composed of a group of symmetric and same-structure two-step microstrip lines, a terminal bent T-shaped microstrip line which is coupled to the two-step microstrip lines and an L-shaped output microstrip line; the reference line and the main line are connected with the L-shaped input microstrip line through a group of series-connected diodes and capacitors respectively; a metal floor is printed on the lower surface of the dielectric substrate; one end of the L-shaped input microstrip line connected with each group of series-connected diodes and capacitors is led out and connected with the metal floor through a metallized via hole.

Description

Technical Field

[0001] This invention belongs to the field of microwave and radio frequency technology, and relates to a filter reconfigurable phase shifter that can be applied to wireless communication and radar fields. Background Technology

[0002] In recent years, with the rapid development of wireless communication and antenna technology, the requirements for miniaturization, integration, and multifunctionality of systems have become increasingly stringent. The use of traditional single-function devices has led to larger system size and increased costs. As one of the most important technologies in wireless communication, beam scanning or beamforming technology can change the radiation mode of an antenna, and its lowest-cost implementation method is passive phased array. Passive phased arrays control the phase of the signal through phase shifters. To achieve higher resolution, the number of antenna elements needs to be increased, which further increases the number of phase shifters in the phased array. Therefore, reducing the cost of phase shifters is of great significance in any beamforming system. Since filters and phase shifters are often used simultaneously in communication systems, multifunctional devices such as reconfigurable phase shifters and phase shifters with filtering characteristics have attracted increasing attention from scholars both domestically and internationally due to their advantages of low cost and small size.

[0003] For example, in 2023, Xiong Chen et al. published a paper titled "Novel Synthesis Method for Reconfigurable Filtering Phase Shifter With Frequency-Dependent Coupling Using Optimization Technique" in IEEE Transactions on Circuits and Systems II: Express Briefs (Volume: 70, Issue: 4, April 2023). This paper proposed a filter reconfigurable phase shifter that controls the switching of diodes using an external bias voltage to select different paths, thereby achieving changes in the phase shift between ports. However, this structure operates at a relatively low frequency and has a narrow bandwidth for phase shifting. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by proposing a reconfigurable filter phase shifter based on a stub-loaded resonator. This invention aims to improve the operating bandwidth of this type of device at higher frequencies and increase the integration of the phase shifter, thereby meeting the performance requirements of wireless communication systems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A reconfigurable filter phase shifter based on a stub-loaded resonator includes a rectangular dielectric substrate 1 and two L-shaped input microstrip lines 2 and four L-shaped output microstrip lines 3 printed on the upper surface of the rectangular dielectric substrate 1.

[0007] The rectangular dielectric substrate is divided into four square regions by the AA' and BB' lines that run through the center of the upper surface of the substrate. The four L-shaped output microstrip lines 3 correspond one-to-one with the four square regions. Each square region and the BB' line are equipped with a T-shaped microstrip line 4 and two stepped microstrip lines 5 belonging to the same group.

[0008] Each stepped microstrip line 5 consists of two microstrip lines, including a narrow segment and a wide segment; two stepped microstrip lines in the same group are on the same straight line, and the narrow segments of the stepped microstrip lines in the same group are adjacent and do not contact each other; the T-shaped microstrip line 4 is composed of a uniform microstrip line 41 and a bent microstrip line 42, with one end of the bent microstrip line 42 connected to the middle position of the uniform microstrip line 41; the T-shaped microstrip line is located on one side of the stepped microstrip lines in the same group, and the uniform microstrip line 41 is parallel to the straight line on which the stepped microstrip lines in the same group are located;

[0009] Both L-shaped input microstrip lines 2 are located on the BB' line. The filtering between the two L-shaped input microstrip lines 2 and between the L-shaped input microstrip line 2 and the adjacent L-shaped output microstrip line 3 is achieved through a T-shaped microstrip line 4 and two stepped microstrip lines 5 in the corresponding group.

[0010] The input terminals of the L-shaped input microstrip line 2 and its adjacent stepped microstrip line 5 are connected by a series diode and a capacitor 6; each uniform microstrip line 41 is coupled to the narrow segments of the two stepped microstrip lines 5 in the same group.

[0011] The lower surface of the rectangular dielectric substrate 1 is printed with a metal ground plane 7. A series diode and capacitor 6 are connected to one end of the L-shaped input microstrip line 2 and an isolation inductor 8 is connected in parallel. The isolation inductor 8 is connected to the metal ground plane 7 through a metallized via 9.

[0012] Furthermore, the stubs of the L-shaped input microstrip line 2, which serves as a port, are parallel to the stubs of the L-shaped output microstrip line 3, which also serves as a port; the uniform microstrip line 41 of each T-shaped microstrip line 4 is parallel to the stepped microstrip line 5 in the same group.

[0013] Furthermore, the stepped microstrip lines 5 on both sides of each L-shaped input microstrip line 2 are located on a line and are parallel to the AA' line.

[0014] Furthermore, another branch microstrip line of the L-shaped output microstrip line 3, which is directly connected to the wide section of the stepped microstrip line 5, is parallel to the AA' line, and this branch microstrip line has a length corresponding to the target phase shift of each main line.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. This invention utilizes the mutual coupling between the symmetrical stepped impedance microstrip lines printed on the upper surface of the rectangular dielectric substrate and the microstrip lines of the T-shaped loaded stepped stubs to generate two controllable transmission zeros. This structure improves passband selectivity.

[0017] 2. This invention employs a reconfigurable design, allowing switching between phase shifts of 0°, 45°, 90°, 135°, and 180° by applying bias voltages to each diode and controlling their on / off states. This design significantly reduces the number of components used in the phased array, is simple in structure, easy to implement, and improves the overall system integration. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a diagram showing the interrelationships of the various structures on the upper surface of the dielectric substrate of the present invention;

[0020] Figure 3 This is a diagram showing the dimensions of the various structures on the upper surface of the dielectric substrate of the present invention;

[0021] Figure 4 The measured S-parameter diagrams of return loss and insertion loss for the reference line, 45° and 90° main lines of this invention are shown.

[0022] Figure 5 The measured S-parameter diagrams of return loss and insertion loss for the 135° and 180° main lines of this invention are shown.

[0023] Figure 6 This is a schematic diagram of the phase shift curves of each phase shifter of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] A reconfigurable filter phase shifter based on a stub-loaded resonator includes a rectangular dielectric substrate 1 and two L-shaped input microstrip lines 2 and four L-shaped output microstrip lines 3 printed on the upper surface of the rectangular dielectric substrate 1. The feature is that the printed microstrip structures on both sides of the two L-shaped input microstrip lines 2 are symmetrical about the midlines AA' and BB' of opposite sides of the rectangular dielectric substrate 1. Each set of L-shaped input microstrip lines 2 and L-shaped output microstrip lines 3, or the space between two L-shaped output microstrip lines 3 on the same side, is used to implement the filtering function. The system comprises a T-shaped microstrip line 4 and a set of two symmetrical and identical stepped microstrip lines 5; each stepped microstrip line 5 consists of two microstrip lines, with the narrower ends facing each other symmetrically; each T-shaped microstrip line 4 consists of a uniform microstrip line 41 and a bent microstrip line 42 in the center, and each uniform microstrip line 41 is coupled to the narrower portions of the two adjacent stepped microstrip lines 5; the L-shaped input microstrip line 2 and the input end of the symmetrical set of stepped microstrip lines 5 are connected by a series diode and capacitor 6.

[0026] The lower surface of the rectangular dielectric substrate 1 is printed with a metal ground plane 7. A series diode and capacitor 6 are connected to one end of the L-shaped input microstrip line 2 and an isolation inductor 8 is connected in parallel. The isolation inductor 8 is connected to the metal ground plane 7 through a metallized via 9.

[0027] The reconfigurable filter phase shifter based on a stub-loaded resonator is characterized in that the reference line located on the central axis BB' is connected to one side of the corner of the L-shaped input microstrip line 2 on both sides through two sets of series-connected diodes and capacitors 6; the input end of the stepped microstrip line 5 of the four main lines in the structure is connected to one end of the adjacent L-shaped input microstrip line 2 or the other side of the corner through a set of series-connected diodes and capacitors 6; only one of the L-shaped input microstrip line 2 and L-shaped output microstrip line 3 can be regarded as an input port at the same time, and only the port near the outside of the rectangular dielectric substrate 1 can be regarded as an input port or an output port; the wider parts of the L-shaped input microstrip line 2, L-shaped output microstrip line 3 and stepped microstrip line 5 all adopt a 50Ω impedance linewidth.

[0028] The following is a more specific example:

[0029] Reference Figure 1 , Figure 2 , Figure 3This embodiment includes a rectangular dielectric substrate 1, a pair of L-shaped input microstrip lines 2 printed on the upper surface of the rectangular dielectric substrate 1, a main line located on AA', and four main lines perpendicular to the main line located on both sides of the two L-shaped input microstrip lines 2; the reference line is composed of a set of two symmetrical and identical stepped microstrip lines 5 and a T-shaped microstrip line 4; each main line is composed of a set of two symmetrical and identical stepped microstrip lines 5 and a T-shaped microstrip line 4, and an L-shaped output microstrip line 3; wherein the stepped microstrip line 5 and the T-shaped microstrip line 4 constitute a filter; the stepped microstrip line 5 is composed of two microstrip lines, wherein the narrower end is symmetrically opposite to the other;

[0030] Each T-shaped microstrip line 4 consists of a uniform microstrip line 41 and a bent microstrip line 42 in the center. Each uniform microstrip line is coupled to the narrower portions of two adjacent stepped microstrip lines 5. The L-shaped output microstrip line 3 is used to adjust the phase. Each line is connected to the input port using a set of diodes and capacitors 6 in series, and an isolation inductor 8 connected in parallel to one end of the L-shaped input microstrip line 2 and above the capacitor and connected to the metallized via 9. The diodes can control the on / off state of the DC bias applied to them to control whether different main lines are connected to the input microstrip line 2. The capacitors are used to isolate DC signals, and the inductors are used to isolate RF signals.

[0031] The wider portions of the L-shaped input microstrip line 2, L-shaped output microstrip line 3, and stepped microstrip line 5 all use a 50Ω impedance linewidth. The longer segments of the L-shaped input microstrip line 2 and the wider segments of the stepped microstrip line 5, along with the midline of the diodes and capacitors 6 connected in series at both ends of the reference line, are all located on BB'. One end of the narrower segment of the stepped microstrip line 5 is aligned with one side of the wider segment and is coupled parallel to the uniform microstrip line 41 in the T-shaped microstrip line 4. The midline of the wider segment of the stepped microstrip line 42, which is symmetrical about AA' and bends about the uniform microstrip line 41 in the T-shaped microstrip line 4 of the reference line, is located on AA', and the narrower segment is perpendicular to AA' and points downwards.

[0032] The shorter segment of the L-shaped input microstrip line 2 is parallel to both ends of AA' and connected to a series diode and capacitor 6, as well as the main line. The longer segment of the L-shaped output microstrip line 3, the narrower segment of the uniform microstrip line 41 and the bent stepped microstrip line 42 on the stepped microstrip line 5 and the series diode and capacitor 6 are all parallel to AA'. The shorter segment of the L-shaped output microstrip line 3 and the wider segment of the bent stepped microstrip line 42 on the T-shaped microstrip line 4 are parallel to BB'. The L-shaped input microstrip line 2 is directly connected to the diodes in the series diode and capacitor 6. The isolation inductor 8 of the main line is located to the left of BB' and perpendicular to BB'.

[0033] The isolation inductor 8 for the reference lines is located between AA' and each reference line and is perpendicular to AA'; the metallized via 9 is located in front of each isolation inductor 8 along the BB' direction; a metal ground plane 7 is printed on the lower surface of the rectangular dielectric substrate 1, which is connected to the isolation inductor 8 through the metal via 9. Wherein:

[0034] The rectangular dielectric substrate 1 is made of Roger 5880 material with a relative permittivity of 2.2, a loss tangent of 0.0009, a size of 170mm × 63mm, and a thickness of 0.8mm.

[0035] The phase shifters are arranged as follows: the one located in the middle of the rectangular dielectric substrate 1 is the 0° reference line; the one in the upper right is the 45° phase shifter; the one in the lower right is the 90° phase shifter; the one in the upper left is the 135° phase shifter; and the one in the lower left is the 180° phase shifter.

[0036] The linewidth of all 50Ω microstrip lines is w0 = 2.5mm; the uniform microstrip line 41 of all T-shaped microstrip lines 4 is equal to the sum of the narrower segment length and the spacing gap = 2.5mm of a pair of stepped microstrip lines 5, l0 = 31mm; the thicker segment length of all bent stepped microstrip lines 42 is l3 = 17.76mm and the narrower segment length is l4 = 14.9mm; the radius of all metal vias 9 is R = 1mm; all capacitors are C = 1μF; and the size of all isolation inductors 8 is L = 2μH.

[0037] The wider section of the stepped microstrip line 5 of the main line has a length l1 = 6 mm, the uniform microstrip line 41 of the T-shaped microstrip line 4 has a linewidth w1 = 0.58 mm, a coupling gap width g1 = 0.17 mm, and the thicker section of the bent stepped microstrip line 42 has a width w2 = 1.36 mm and a narrower section width w3 = 0.26 mm; the wider section of the stepped microstrip line 5 of the 45° phase shifter has a length l7 = 11.5 mm, the uniform microstrip line 41 of the T-shaped microstrip line 4 has a linewidth w7 = 0.56 mm, a coupling gap width g3 = 0.13 mm, and the thicker section of the bent stepped microstrip line 42 has a length l7 = 11.5 mm, a length l7 = 0.56 mm, a coupling gap width g3 = 0.13 mm, and a narrower section of the bent stepped microstrip line 42 has a width l1 = 0.58 mm, a linewidth w1 = 0.58 mm, a coupling gap width g1 = 0.17 ... width w1 = 0.58 mm. The L-shaped output microstrip line 3 has a line width of l8 = 1.25 mm, a narrower section width of w9 = 0.5 mm, and a line length of l8 = 16.9 mm; the stepped microstrip line 5 of the 90° phase shifter has a wider section length of l5 = 11 mm, the uniform microstrip line 41 of the T-shaped microstrip line 4 has a line width of w4 = 0.56 mm, a coupling gap width of g2 = 0.11 mm, the thicker section width of the bent stepped microstrip line 42 is w5 = 1.2 mm, the narrower section width is w6 = 0.7 mm, and the line length of L-shaped output microstrip line 3 is l6 = 22 mm; the stepped microstrip line 5 of the 135° phase shifter has a wider section length of l8 = 1.25 mm, a narrower section width of w9 = 0.5 mm, and a line length of l8 = 16.9 mm. 11 =14mm, uniform microstrip line 41 with linewidth w of T-shaped microstrip line 41 13=0.52mm, coupling gap width g5=0.15mm, width w of the thicker section of the bent stepped microstrip line 42 14 =1.2mm, narrower section width w 15 =0.7mm, the length l of the L-shaped output microstrip line 3 12 =14.7mm; the wider section length l9 of the stepped microstrip line 5 of the 180° phase shifter is 13mm, and the uniform microstrip line 41 of the T-shaped microstrip line 4 has a linewidth w 10 =0.56mm, coupling gap width g4=0.15mm, width w of the thicker section of the bent stepped microstrip line 42 11 =1.5mm, narrower section width w 12 =0.7mm, the length l of the L-shaped output microstrip line 3 10 =8.7mm;

[0038] The working principle of this invention is as follows: the signal is input through an L-shaped output microstrip line, and the switching on and off of diodes is controlled by an external bias voltage to control the switching on and off of different phase shifters. Only one phase shifter can be running at a time. The specific control method is as follows:

[0039] 1. When only two L-shaped output microstrip lines and two diodes located on BB' are turned on, the reference line operates. At this time, one of the two L-shaped output microstrip lines serves as the input terminal and the other as the output terminal.

[0040] 2. When the 45° phase shifter is running, only the diode on the left side of the upper L-shaped output microstrip line is turned on;

[0041] 3. When the 90° phase shifter is running, only the diode on the left side of the lower L-shaped output microstrip line is turned on;

[0042] 4. When the 135° phase shifter is running, only the diode on the right side of the upper L-shaped output microstrip line is turned on;

[0043] 5. When the 180° phase shifter is running, only the diode on the right side of the lower L-shaped output microstrip line is turned on;

[0044] In this process, the paired stepped microstrip line coupled T-shaped microstrip structure of each phase shifting unit will generate two adjustable transmission zeros and four transmission poles. The position of the transmission poles can be controlled by controlling the stepped stubs of the T-shaped microstrip structure, and the filter structure has minimal impact on the transmission phase. Different phase shift angles can be achieved by adjusting the length of the L-shaped output microstrip line.

[0045] The technical effects of the present invention will be further explained below based on the actual test results:

[0046] 1. Experimental conditions and content: The return loss, insertion loss, and phase difference of this invention were measured using a vector network analyzer N5230C. The results are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0047] 2. Analysis of experimental results:

[0048] Reference Figure 4 and Figure 5 In this embodiment, the center frequency of the passband is 3.5 GHz;

[0049] Among all filter phase shifters, the maximum return loss in the passband is |S 11 |All are greater than 45dB, minimum insertion loss|S 21 | is 0.44dB; all filters have a transmission zero on both sides of the passband, located near 2GHz and 5GHz, and the return loss in the passband is greater than 10dB.

[0050] Reference Figure 6 Phase shifts of 45°, 90°, 135° and 180° were achieved in the 2.5GHz-4.5GHz range, respectively, achieving a relative bandwidth of 57.1%.

Claims

1. A reconfigurable filter phase shifter based on a stub-loaded resonator, comprising a rectangular dielectric substrate (1) and two L-shaped input microstrip lines (2) and four L-shaped output microstrip lines (3) printed on the upper surface of the rectangular dielectric substrate (1); characterized in that, The rectangular dielectric substrate is divided into four square regions by the AA' and BB' lines that run through the center of the upper surface. The four L-shaped output microstrip lines (3) correspond one-to-one with the four square regions. Each square region and the BB' line are provided with a T-shaped microstrip line (4) and two stepped microstrip lines (5) belonging to the same group. Each stepped microstrip line (5) consists of two segments, including a narrow segment and a wide segment; the two stepped microstrip lines in the same group are on the same straight line, and the narrow segments of the stepped microstrip lines in the same group are adjacent and do not contact each other; the T-shaped microstrip line (4) consists of a uniform microstrip line (41) and a bent microstrip line (42), one end of the bent microstrip line (42) is connected to the middle position of the uniform microstrip line (41); the T-shaped microstrip line is located on one side of the stepped microstrip lines in the same group, and the uniform microstrip line (41) is parallel to the straight line where the stepped microstrip lines in the same group are located; Both L-shaped input microstrip lines (2) are located on the BB' line. The two L-shaped input microstrip lines (2) and the L-shaped input microstrip line (2) and the adjacent L-shaped output microstrip line (3) are filtered by a T-shaped microstrip line (4) and two stepped microstrip lines (5) of the corresponding group. The input terminals of the L-shaped input microstrip line (2) and its adjacent stepped microstrip line (5) are connected by a series diode and a capacitor (6); each uniform microstrip line (41) is coupled to the narrow segments of the two stepped microstrip lines (5) in the same group; The lower surface of the rectangular dielectric substrate (1) is printed with a metal ground plane (7). A series diode and a capacitor (6) are connected to one end of the L-shaped input microstrip line (2) and an isolation inductor (8) is connected in parallel. The isolation inductor (8) is connected to the metal ground plane (7) through a metallized via (9).

2. The reconfigurable filter phase shifter based on a stub-loaded resonator according to claim 1, characterized in that, The stubs of the L-shaped input microstrip line (2) serving as a port are parallel to the stubs of the L-shaped output microstrip line (3) serving as a port; the uniform microstrip line (41) of each T-shaped microstrip line (4) is parallel to the stepped microstrip line (5) of the same group.

3. A reconfigurable filter phase shifter based on a stub-loaded resonator according to claim 1, characterized in that, The stepped microstrip lines (5) on both sides of each L-shaped input microstrip line (2) are located on a line and are parallel to the AA' line.

4. A reconfigurable filter phase shifter based on a stub-loaded resonator according to claim 2, characterized in that, Another branch microstrip line of the L-shaped output microstrip line (3), which is directly connected to the wide section of the stepped microstrip line (5), is parallel to the AA' line, and this branch microstrip line has a length corresponding to the target phase shift of each main line.

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