Balanced broadband substrate integrated coaxial line filter switch

Abstract

The invention discloses a balanced broadband substrate integrated coaxial line filter switch, which is characterized in that a broadside coupling structure consisting of a top coplanar waveguide loaded by a PIN tube and a substrate integrated coaxial line is arranged between a pair of substrate integrated coaxial line feed structures with mode impedance identification; the balanced broadband substrate integrated coaxial line filter switch is realized by utilizing the broadside coupling effect, the mode impedance of the feed structure and the short-circuit and open-circuit effects of the PIN tube, has the advantages of switchable differential-mode filter passband, common-mode rejection and broadband work, and can consider small size, simple structure and planar integration.

Description

Technical Field

[0001] The invention relates to a microwave communication device, in particular to a filter switch. Background Art

[0002] Switches and filters are both important components of the RF front-end. Generally, they are cascaded in the system. In order to reduce the number of components in the system, reduce losses and reduce size, a filter switch that integrates switches and filters is proposed, which can realize both switching and filtering functions in a single device.

[0003] The existing filter switches are mainly microstrip filter switches, dielectric resonator filter switches and coaxial resonator filter switches. There are two main methods for implementing microstrip filter switches: one is to connect multiple quarter-wavelength short-circuit branches in parallel with field effect tubes; the other is to cascade multiple quarter-wavelength short-circuit resonators or half-wavelength open-circuit resonators in a coupled manner, and load PIN tubes on one or more resonators. The main feature of the microstrip filter switch is that it can be integrated in a plane, and the weakness is poor shielding. The dielectric resonator filter switch is based on a multi-order filter, and the filter switch is realized by loading the PIN tube on the open end of the feeder. The main features are low loss and good frequency selectivity, and the weakness is complex structure and poor integration. The coaxial resonator filter switch is to introduce a PIN tube between the inner core and the outer conductor in each coaxial resonator to realize the filter switch, and the main features are similar to the dielectric resonator filter switch. However, there is currently no balanced substrate integrated coaxial line filter switch, which cannot switch the differential mode filter passband, has no common mode suppression, and has a relatively narrow bandwidth. In addition, some designs cannot take into account small size, simple structure and planar integration.

[0004] Therefore, it is necessary to propose a balanced broadband substrate integrated coaxial line filter switch that can take into account small size, simple structure and planar integration. Summary of the invention

[0005] Purpose of the invention: In view of the above-mentioned prior art, a balanced broadband substrate integrated coaxial line filter switch is proposed to solve the problems that the existing filter switches cannot switch the differential mode filter passband, have no common mode suppression, have a narrow bandwidth, and some designs cannot take into account small size, simple structure and planar integrability.

[0006] Technical solution: A balanced broadband substrate integrated coaxial line filter switch, comprising a top metal layer, a first substrate layer, an intermediate metal layer, a second substrate layer, and a bottom metal layer arranged in order from top to bottom, and also comprising metallized vias, resistors, and two PIN tubes; The top metal layer is composed of a rectangular metal ground with a T-slot, a horizontal metal strip, and a vertical metal strip; the horizontal metal strip and the vertical metal strip are respectively embedded in the horizontal and vertical grooves of the T-slot; two PIN tubes are respectively located on both sides of the horizontal metal strip, with the negative poles connected to the center of the horizontal metal strip and the positive poles connected to the horizontal center point of the rectangular metal ground; the resistor connects the upper ends of the horizontal metal strip and the vertical metal strip; The middle metal layer is bilaterally symmetrical, and includes metal strips 1 to 8; metal strips 2 and 7 are horizontally arranged on the left and right sides; metal strips 1 and 3 are respectively vertically connected to the two ends of the same side of metal strip 2, and metal strips 6 and 8 are respectively vertically connected to the two ends of the same side of metal strip 7; metal strips 4 and 5 are horizontally arranged between metal strips 2 and 7, and metal strips 4 and 5 are located directly below the horizontal metal strips; one end of metal strip 4 is connected to one end of metal strip 3, and one end of metal strip 5 is connected to one end of metal strip 7; The metallized vias penetrate from the top metal layer to the bottom metal layer; the metal strips 1 to 8, the metallized vias, the first substrate layer, the second substrate layer, the top metal layer, and the bottom metal layer constitute substrate integrated coaxial line 1 to substrate integrated coaxial line 8; the rectangular metal ground of the top metal layer, the horizontal metal strips, the first substrate layer, the second substrate layer, and the bottom metal layer together constitute a top coplanar waveguide; the substrate integrated coaxial line 1 and the substrate integrated coaxial line 3 constitute a pair of balanced input feed lines, and the substrate integrated coaxial line 6 and the substrate integrated coaxial line 8 constitute a pair of balanced output feed lines; When the two PIN tubes are reverse biased, the top coplanar waveguide and substrate integrated coaxial line 4 to substrate integrated coaxial line 5 form a broadside coupling structure.

[0007] Furthermore, horizontal center points of the horizontal metal strip, the rectangular metal ground and the horizontal portion of the T-shaped slot overlap.

[0008] Furthermore, the electrical length of the horizontal metal strip is between 0.52 and 0.58λ. g Between g is the guided wavelength corresponding to the center frequency.

[0009] Furthermore, the structure composed of substrate integrated coaxial line 1 to substrate integrated coaxial line 3 can be equivalent to A ohm impedance at the center frequency of the differential mode state, and the impedance decreases when away from the center frequency, and is equivalent to B ohm impedance in the common mode state. The wide-side coupling structure can obtain broadband matching with A ohm impedance, but cannot match with B ohm impedance and lower impedance, thereby obtaining broadband differential mode filtering response and common mode suppression.

[0010] Beneficial effects: 1. The present invention places a broadside coupling structure composed of a top coplanar waveguide loaded by a PIN tube and a substrate integrated coaxial line in the middle of a pair of substrate integrated coaxial line feeding structures with mode impedance recognition, and utilizes the broadside coupling effect, the mode impedance of the feeding structure and the short-circuit and open-circuit effects of the PIN tube to realize a balanced broadband substrate integrated coaxial line filter switch, which has the advantages of differential mode filtering passband switchability, common mode suppression and broadband operation, and can take into account small size, simple structure and planar integrability.

[0011] 2. Two PIN tubes are located on both sides of the center position of the top coplanar waveguide strip. The two ends of each PIN tube are respectively connected to the center point of the coplanar waveguide strip and the horizontal center point of the top metal ground. The two PIN tubes use the same DC bias voltage. When the PIN tube is forward biased, the center point of the top coplanar waveguide is connected to the metal ground, which is equivalent to a short circuit. The short circuit point is effective for all frequency points of the differential mode and common mode. Therefore, the transmission of differential mode and common mode signals can be shut off at this time. The overall circuit is in the off state of the filter switch, and symmetrical loading of the two PIN tubes is beneficial to improve the off isolation. When the PIN tube is reverse biased, the center point of the top coplanar waveguide is equivalent to an open circuit, and the overall circuit is in the on state of the filter switch.

[0012] 3. The top coplanar waveguide and substrate integrated coaxial line 4 to substrate integrated coaxial line 5 form a wide-side coupling structure, which improves the coupling strength between the two, can provide three transmission poles for the differential mode filtering response, and provide a basis for broadband differential mode operation. Structurally, the wide-side coupling structure occupies a small area and has a compact and simple structure, so that the overall circuit has the characteristics of small size and simple structure.

[0013] 4. The substrate integrated coaxial line one and the substrate integrated coaxial line three are respectively connected to the two ends of the same side of the substrate integrated coaxial line two. At this time, the structure composed of the three is equivalent to 25 ohm impedance at the center frequency of the differential mode state. The impedance decreases when it is far away from the center frequency, and is equivalent to 6 ohm impedance in the common mode state; the structure composed of substrate integrated coaxial line six, substrate integrated coaxial line seven and substrate integrated coaxial line eight has similar characteristics; when combined with the wide-side coupling structure, broadband differential mode filtering response and common mode suppression can be obtained. At this time, the substrate integrated coaxial line structure provides two transmission poles for the differential mode filtering response; in terms of structure, the substrate integrated coaxial line can embody the characteristics of small size and simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a three-dimensional structural schematic diagram of the balanced broadband substrate integrated coaxial line filter switch of the present invention; Figure 2 It is a schematic diagram of the top structure of the balanced broadband substrate integrated coaxial line filter switch of the present invention; Figure 3It is a middle horizontal screenshot of the balanced broadband substrate integrated coaxial line filter switch of the present invention; Figure 4 It is the simulation response of the balanced broadband substrate integrated coaxial line filter switch of the present invention in the on state; Figure 5 This is the simulated response of the balanced broadband substrate integrated coaxial line filter switch of the present invention in the off state. Implementation

[0015] The present invention will be further explained below in conjunction with the accompanying drawings.

[0016] like Figures 1 to 3 As shown, a balanced broadband substrate integrated coaxial line filter switch includes a top metal layer 1, a first substrate layer 2, an intermediate metal layer 3, a second substrate layer 4, and a bottom metal layer 5 arranged in sequence from top to bottom, and also includes a metallized via 6, a resistor 7 and two PIN tubes 8.

[0017] The top metal layer 1 is composed of a rectangular metal ground 101 with a T-slot 102, a horizontal metal strip 103, and a vertical metal strip 104. The horizontal metal strip 103 and the vertical metal strip 104 are respectively embedded in the horizontal and vertical grooves of the T-slot 102, and the horizontal center points of the horizontal metal strip 103, the rectangular metal ground 101, and the horizontal part of the T-slot 102 overlap. The electrical length of the horizontal metal strip 103 is between 0.52 and 0.58 λ. g Between g is the waveguide wavelength corresponding to the center frequency. The two PIN tubes 8 are respectively located on both sides of the horizontal metal strip 103, with the negative electrodes connected to the center of the horizontal metal strip 103 and the positive electrodes connected to the horizontal center point of the rectangular metal ground 101. The resistor 7 connects the upper end of the horizontal metal strip 103 and the vertical metal strip 104.

[0018] The middle metal layer 3 is bilaterally symmetrical, and includes metal strips 1 to 8 301-308. Metal strip 2 302 and metal strip 7 307 are arranged horizontally on the left and right sides; metal strip 1 301 and metal strip 3 303 are respectively vertically connected to the two ends of the same side of metal strip 2 302, and metal strip 6 306 and metal strip 8 308 are respectively vertically connected to the two ends of the same side of metal strip 7 307. Metal strip 4 304 and metal strip 5 305 are horizontally arranged between metal strip 2 302 and metal strip 7 307, and metal strip 4 304 and metal strip 5 305 are located directly below the horizontal metal strip 103; one end of metal strip 4 304 is connected to one end of metal strip 3 303, and one end of metal strip 5 305 is connected to one end of metal strip 7 307.

[0019] The metallized via 6 penetrates from the top metal layer 1 to the bottom metal layer 5. The metallized via 6 consists of metallized vias 1 to 9 601-609, which mainly surround the two sides of the metal strips 1 to 8 301-308, and the metallized via 9 609 surrounds the two sides of the vertical metal strip 104.

[0020] Metal strips 1 to 8 301-308, metalized vias 1 to 8 601-608, first substrate layer 2, second substrate layer 4, top metal layer 1, and bottom metal layer 5 form substrate integrated coaxial line 1 to substrate integrated coaxial line 8. The rectangular metal ground 101 of the top metal layer 1, the horizontal metal strips 103, the first substrate layer 2, the second substrate layer 4, and the bottom metal layer 5 together form a top coplanar waveguide. The substrate integrated coaxial line 1 and the substrate integrated coaxial line 3 form a pair of balanced input feed lines, and the substrate integrated coaxial line 6 and the substrate integrated coaxial line 8 form a pair of balanced output feed lines.

[0021] In the present invention, differential-mode and common-mode signals are input from a balanced input feeder, passed through substrate-integrated coaxial line 1 to substrate-integrated coaxial line 8, top coplanar waveguide, vertical metal strip 104, resistor 7 and two PIN tubes 8, and then output from a balanced output feeder. Under the action of the overall circuit and DC bias voltage, a balanced broadband substrate-integrated coaxial line filter switch is formed, which has a differential-mode broadband filter response, a switching function, and a common-mode suppression function.

[0022] During this working process, when the two PIN tubes 8 are forward biased, the center position of the top coplanar waveguide transmission line strip is connected to the metal ground, which is equivalent to a short circuit. Although the transmission line is an open-circuit resonator, the signal needs to be transmitted from one side to the other in the overall circuit, and the short-circuit point is effective for all frequency points of differential mode and common mode. Therefore, the transmission of differential mode and common mode signals can be shut off at this time, and the overall circuit is in the off state of the filter switch.

[0023] When the two PIN tubes 8 are reverse biased, the center position of the top coplanar waveguide transmission line strip is disconnected from the metal ground, and the top coplanar waveguide and substrate integrated coaxial line 4 to substrate integrated coaxial line 5 form a wide-side coupling structure. At the same time, the structure composed of substrate integrated coaxial line 1 to substrate integrated coaxial line 3 can be equivalent to 25 ohm impedance at the center frequency of the differential mode state, and the impedance decreases when it is far away from the center frequency, and is equivalent to 6 ohm impedance in the common mode state. The wide-side coupling structure can obtain broadband matching with 25 ohm impedance, but cannot match with 6 ohm impedance and lower impedance, so broadband differential mode filtering response and common mode suppression can be obtained.

[0024] The use of different forms of transmission lines has different effects on the filter switch. The substrate integrated coaxial line uses the TEM mode as the main mode, is closed in structure and has a small cross-sectional size. Compared with transmission lines such as microstrip technology, stripline technology, coplanar waveguide technology and substrate integrated waveguide technology, it can take into account loss, low dispersion, size, shielding, working frequency bandwidth and integration. In addition to the above characteristics, the balanced substrate integrated coaxial line filter switch can also switch the differential mode filter band, and can maintain effective common mode suppression in both the on and off states. Therefore, the balanced substrate integrated coaxial line filter switch has important application value and engineering value.

[0025] In summary, the balanced broadband substrate integrated coaxial line filter switch has the advantages of differential mode filter passband switchability, common mode suppression and broadband operation. Since the present invention adopts a substrate integrated coaxial line design, it can take into account small size, simple structure and planar integrability.

[0026] An embodiment of the present invention is listed below. This embodiment uses two layers of Rogers 5880 substrate with the same thickness, and the circuit size is only 1.5 λ g ×0.014 λ g ×0.004 λ g , the circuit structure diagram is as follows Figures 1 to 3 As shown, the on-state response is as Figure 4 As shown, the shutdown state response is as follows Figure 5 As shown. Figure 4 It can be seen that when it is turned on, the center frequency is 1.8 GHz, the 3-dB relative bandwidth can reach 72.6%, the minimum insertion loss is only 0.48 dB, five transmission poles are achieved, and the common-mode rejection in the differential mode passband can reach more than 15 dB. Figure 5 It can be seen that when turned off, the differential mode signal isolation in the observation band can reach more than 23dB, and the common mode rejection can reach more than 35dB.

[0027] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A balanced broadband substrate integrated coaxial line filter switch, characterized in that: It comprises a top metal layer (1), a first substrate layer (2), an intermediate metal layer (3), a second substrate layer (4), and a bottom metal layer (5) which are arranged in order from top to bottom, and also comprises a metallized via (6), a resistor (7), and two PIN tubes (8); The top metal layer (1) is composed of a rectangular metal ground (101) with a T-shaped slot (102), a horizontal metal strip (103), and a vertical metal strip (104); wherein the horizontal metal strip (103) and the vertical metal strip (104) are respectively embedded in the horizontal and vertical slots of the T-shaped slot (102); two PIN tubes (8) are respectively located on both sides of the horizontal metal strip (103), with the negative electrodes respectively connected to the center position of the horizontal metal strip (103) and the positive electrodes respectively connected to the horizontal center point of the rectangular metal ground (101); the resistor (7) connects the upper ends of the horizontal metal strip (103) and the vertical metal strip (104); The middle metal layer (3) is bilaterally symmetrical, and includes metal strips 1 to 8 (301-308); metal strip 2 (302) and metal strip 7 (307) are horizontally arranged on the left and right sides; metal strip 1 (301) and metal strip 3 (303) are respectively vertically connected to the two ends of the same side of metal strip 2 (302); metal strip 6 (306) and metal strip 8 (308) are respectively vertically connected to the same side of metal strip 7 (307). two ends; metal strip four (304) and metal strip five (305) are horizontally arranged between metal strip two (302) and metal strip seven (307), and metal strip four (304) and metal strip five (305) are located directly below the horizontal metal strip (103); one end of metal strip four (304) is connected to one end of metal strip three (303), and one end of metal strip five (305) is connected to one end of metal strip seven (307); The metallized via (6) passes through the top metal layer (1) to the bottom metal layer (5); the metal strips 1 to 8 (301-308), the metallized via, the first substrate layer (2), the second substrate layer (4), the top metal layer (1), and the bottom metal layer (5) form substrate integrated coaxial line 1 to substrate integrated coaxial line 8; the rectangular metal ground (101) of the top metal layer (1), the horizontal metal strip (103), the first substrate layer (2), the second substrate layer (4), and the bottom metal layer (5) together form a top coplanar waveguide; the substrate integrated coaxial line 1 and the substrate integrated coaxial line 3 form a pair of balanced input feed lines, and the substrate integrated coaxial line 6 and the substrate integrated coaxial line 8 form a pair of balanced output feed lines; When the two PIN tubes (8) are reverse biased, the top coplanar waveguide and substrate integrated coaxial line 4 to substrate integrated coaxial line 5 form a broadside coupling structure.

2. The balanced broadband substrate integrated coaxial line filter switch according to claim 1, characterized in that: The horizontal center points of the horizontal metal strip (103), the rectangular metal ground (101) and the horizontal portion of the T-shaped slot (102) overlap.

3. The balanced broadband substrate integrated coaxial line filter switch according to claim 2, characterized in that: The electrical length of the horizontal metal strip (103) is between 0.52 and 0.58λ. g Between g is the guided wavelength corresponding to the center frequency.

4. The balanced broadband substrate integrated coaxial line filter switch according to any one of claims 1 to 3, characterized in that: The structure composed of substrate integrated coaxial line 1 to substrate integrated coaxial line 3 can be equivalent to A ohm impedance at the center frequency of the differential mode state, and the impedance decreases when it is far away from the center frequency, and is equivalent to B ohm impedance in the common mode state. The wide-side coupling structure can obtain broadband matching with A ohm impedance, but cannot match with B ohm impedance and lower impedance, thereby obtaining broadband differential mode filtering response and common mode suppression.

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