A balanced broadband substrate integrated coaxial line filter switch

Abstract

The application discloses a balanced wideband substrate integrated coaxial filter switch, a wide-side coupling structure composed of a top-layer co-planar waveguide loaded with a PIN tube and a substrate integrated coaxial line is arranged in the middle of a pair of substrate integrated coaxial feeding structures with mode impedance identification, and the balanced wideband substrate integrated coaxial filter switch is realized by using the wide-side coupling effect, the mode impedance of the feeding structure and the short-circuit and open-circuit effects of the PIN tube, and has the advantages of switchable differential-mode filter passband, common-mode suppression and wideband operation, and can also consider small size, simple structure and planar integrability.

Description

TECHNICAL FIELD

[0001] The present application relates to a microwave communication device, in particular to a filter switch. BACKGROUND

[0002] Switch and filter are important devices of radio frequency front end, generally cascaded in system, in order to reduce the number of devices in the system, reduce the loss and reduce the size, the filter switch of switch and filter fusion is proposed, which can realize the functions of switch and filter in a single device.

[0003] The existing filter switch is mainly microstrip filter switch, dielectric resonator filter switch and coaxial resonator filter switch. There are mainly two kinds of implementation methods for microstrip filter switch: one is that multiple quarter wavelength short circuit stubs are respectively connected in parallel with field effect tubes; the other is that multiple quarter wavelength short circuit resonators or half wavelength open circuit resonators are cascaded in a coupling manner, and a PIN tube is loaded on one or more resonators. The main feature of microstrip filter switch is planar integration, and the weakness is poor shielding. The dielectric resonator filter switch is based on a multi-stage filter, and a PIN tube is loaded on the open end of the feed line to realize the filter switch. The main feature is small loss and good frequency selectivity, and the weakness is complex structure and poor integrability. The coaxial resonator filter switch introduces a PIN tube between the inner core and the outer conductor in each coaxial resonator to realize the filter switch. The main feature is similar to that of the dielectric resonator filter switch. However, there is no balanced substrate integrated coaxial line filter switch at present, which cannot switch the differential mode filter passband, has no common mode suppression, and the bandwidth is relatively narrow, and in addition, part of the design cannot consider small size, simple structure and planar integration.

[0004] Therefore, it is necessary to propose a balanced wideband substrate integrated coaxial line filter switch, which can consider small size, simple structure and planar integration. SUMMARY

[0005] The present application is a balanced wideband substrate integrated coaxial line filter switch, which solves the problem that the existing filter switch cannot switch the differential mode filter passband, has no common mode suppression, and the bandwidth is relatively narrow, and part of the design cannot consider small size, simple structure and planar integration.

[0006] Technical scheme: A balanced wideband substrate integrated coaxial line filter switch, comprising top metal layer, first substrate layer, middle metal layer, second substrate layer and bottom metal layer arranged in sequence from top to bottom, and further comprising metallized via, resistance and two PIN tubes.

[0007] The top metal layer is composed of a rectangular metal ground with a T-shaped 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 part and the vertical part of the T-shaped slot; two PIN tubes are respectively located on both sides of the horizontal metal strip, the negative electrode is connected with the center of the horizontal metal strip, and the positive electrode is connected with the horizontal center of the rectangular metal ground; a resistor connects the upper end of the horizontal metal strip and the vertical metal strip.

[0008] The middle metal layer is left-right symmetrical and contains metal strip one to metal strip eight; metal strip two and metal strip seven are horizontally arranged on the left and right sides; metal strip one and metal strip three are respectively vertically connected to both ends of the same side of metal strip two, and metal strip six and metal strip eight are respectively vertically connected to both ends of the same side of metal strip seven; metal strip four and metal strip five are horizontally arranged opposite to each other between metal strip two and metal strip seven, and metal strip four and metal strip five are located directly below the horizontal metal strip; one end of metal strip four is connected with one end of metal strip three, and one end of metal strip five is connected with one end of metal strip seven.

[0009] The metalized via penetrates from the top metal layer to the bottom metal layer; metal strip one to metal strip eight, the metalized via, the first substrate layer, the second substrate layer, the top metal layer and the bottom metal layer form substrate integrated coaxial lines one to eight; the rectangular metal ground, the horizontal metal strip and the first substrate layer, the second substrate layer and the bottom metal layer of the top metal layer together form a top layer coplanar waveguide; substrate integrated coaxial lines one and three form a pair of balanced input feed lines, and substrate integrated coaxial lines six and eight form a pair of balanced output feed lines.

[0010] When the two PIN tubes are reversely biased, the top layer coplanar waveguide and substrate integrated coaxial lines four to five form a wide-side coupling structure.

[0011] Further, the horizontal center points of the horizontal metal strip, the rectangular metal ground and the horizontal part of the T-shaped slot are overlapped.

[0012] Further, the electrical length of the horizontal metal strip is between 0.52~0.58λ g , and λ g is the guided wave wavelength corresponding to the center frequency.

[0013] Further, the structure formed by substrate integrated coaxial lines one to three is equivalent to A ohm impedance at the center frequency in the differential mode state, and the impedance decreases when away from the center frequency; in the common mode state, it is equivalent to B ohm impedance, the wide-side coupling structure can achieve wideband matching with A ohm impedance, but cannot match with B ohm impedance and lower impedance, thereby wideband differential mode filtering response and common mode suppression can be achieved.

[0014] Beneficial effects: 1. The present application places the wide-side coupling structure composed of the top layer co-planar waveguide loaded PIN tube and the substrate integrated coaxial line into a pair of substrate integrated coaxial line feeding structures with mode impedance recognition, and uses the wide-side coupling effect, the mode impedance of the feeding structure and the short circuit and open circuit effect of the PIN tube to realize a balanced broadband substrate integrated coaxial line filter switch, which has the advantages of switchable differential mode filter passband, common mode suppression and broadband operation, and can also consider small size, simple structure and planar integrability.

[0015] 2. Two PIN tubes are located on both sides of the center of the top layer co-planar waveguide strip, and the two ends of each PIN tube are connected with the center point of the co-planar waveguide strip and the horizontal center point of the top layer metal ground, respectively, and the two PIN tubes use the same DC bias voltage; when the PIN tube is forward biased, the center point of the top layer co-planar waveguide is conductive to the metal ground, which is equivalent to a short circuit, and this short circuit point has effect on all frequency points of the differential mode and the common mode, so at this time the transmission of the differential mode and the common mode signal can be turned off, and the overall circuit is in the off state of the filter switch, and symmetrically loading two PIN tubes is beneficial to improve the off isolation; when the PIN tube is reversely biased, the center point of the top layer co-planar waveguide is equivalent to an open circuit, and the overall circuit is in the on state of the filter switch.

[0016] 3. The top layer co-planar waveguide and the substrate integrated coaxial line four form a wide-side coupling structure with the substrate integrated coaxial line five, which improves the coupling strength between the two, can provide three transmission poles for the differential mode filter response, and provides a basis for broadband differential mode operation, and in terms of structure, the wide-side coupling structure has small footprint and compact and simple structure, so that the overall circuit has the characteristics of small size and simple structure.

[0017] 4. The substrate integrated coaxial line one and the substrate integrated coaxial line three are connected to the same side of the substrate integrated coaxial line two, at this time the structure composed of the three is equivalent to a 25 ohm impedance at the center frequency of the differential mode, and the impedance decreases away from the center frequency, and in the common mode state, the structure is equivalent to a 6 ohm impedance; the structure composed of the substrate integrated coaxial line six, the substrate integrated coaxial line seven and the substrate integrated coaxial line eight has similar characteristics; when combined with the wide-side coupling structure, broadband differential mode filter 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 filter response; in terms of structure, the substrate integrated coaxial line can reflect the characteristics of small size and simple structure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a three-dimensional structure diagram of the balanced broadband substrate integrated coaxial line filter switch of the present application;

[0019] Figure 2 It is a top layer structure diagram of the balanced broadband substrate integrated coaxial line filter switch of the present application;

[0020] Figure 3 This is a horizontal middle shot of the balanced broadband substrate integrated coaxial line filter switch of the present invention;

[0021] Figure 4 This is the simulation response of the balanced broadband substrate integrated coaxial line filter switch of the present invention in the on state;

[0022] 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 Method

[0023] The present invention will be further explained below with reference to the accompanying drawings.

[0024] 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.

[0025] The top metal layer 1 consists of a rectangular metal ground plane 101 with T-slots 102, horizontal metal strips 103, and vertical metal strips 104. The horizontal metal strips 103 and vertical metal strips 104 are embedded in the horizontal and vertical portions of the T-slots 102, respectively. The horizontal center points of the horizontal metal strips 103, the rectangular metal ground plane 101, and the horizontal portion of the T-slots 102 overlap. The electrical length of the horizontal metal strips 103 is between 0.52 and 0.58 λ. g Between, λ g is the guided wavelength corresponding to the center frequency. Two PIN transistors 8 are located on either side of horizontal metal strip 103, with their cathodes connected to the center of horizontal metal strip 103 and their anodes connected to the horizontal center point of rectangular metal ground 101. Resistor 7 connects the upper ends of horizontal metal strip 103 and vertical metal strip 104.

[0026] The intermediate metal layer 3 is symmetrical about the vertical center line, and comprises metal strips 1-8 301-308. The metal strip 2 302 and the metal strip 7 307 are horizontally arranged on the left and right sides. The metal strip 1 301 and the metal strip 3 303 are vertically connected to the same side of the two ends of the metal strip 2 302. The metal strip 6 306 and the metal strip 8 308 are vertically connected to the same side of the two ends of the metal strip 7 307. The metal strip 4 304 and the metal strip 5 305 are horizontally arranged between the metal strip 2 302 and the metal strip 7 307, and the metal strip 4 304 and the metal strip 5 305 are located below the horizontal metal strip 103. One end of the metal strip 4 304 is connected to one end of the metal strip 3 303. One end of the metal strip 5 305 is connected to one end of the metal strip 7 307.

[0027] The metalized via hole 6 penetrates from the top metal layer 1 to the bottom metal layer 5. The metalized via hole 6 is composed of metalized via holes 1-9 601-609. The metalized via holes 1-8 601-608 are mainly arranged on the two sides of the metal strips 1-8 301-308. The metalized via hole 9 609 is arranged on the two sides of the vertical metal strip 104.

[0028] The metal strips 1-8 301-308, the metalized via holes 1-8 601-608, 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 lines 1-8. 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 layer coplanar waveguide. The substrate integrated coaxial line 1 and the substrate integrated coaxial line 3 form a pair of balanced input feed lines. The substrate integrated coaxial line 6 and the substrate integrated coaxial line 8 form a pair of balanced output feed lines.

[0029] In the present application, the differential mode and common mode signals are input from the balanced input feed lines, pass through the substrate integrated coaxial lines 1-8, the top layer coplanar waveguide, the vertical metal strip 104, the resistor 7 and the two PIN tubes 8, and are then output from the balanced output feed lines, thereby forming a balanced broadband substrate integrated coaxial line filter switch under the action of the overall circuit and the direct current bias voltage. The balanced broadband substrate integrated coaxial line filter switch has the functions of differential mode broadband filtering response and switching, and common mode suppression.

[0030] During the working process, when the two PIN tubes 8 are forward biased, the center position of the top layer coplanar waveguide transmission line strip is conductive with the metal ground, which is equivalent to a short circuit. Although the transmission line is an open resonator, the signal needs to be transmitted from one side to the other side in the overall circuit, and the short circuit point has an effect on all frequency points of the differential mode and the common mode. Therefore, the transmission of the differential mode and the common mode signals can be turned off at this time, and the overall circuit is in the off state of the filter switch.

[0031] When the two PIN diodes 8 are reversely biased, the center of the top layer CPW strip is disconnected from the metal ground, and the top layer CPW and the substrate integrated coaxial line four and the substrate integrated coaxial line five form a broadside coupled structure. Meanwhile, the structure formed by the substrate integrated coaxial line one and the substrate integrated coaxial line three is equivalent to a 25-ohm impedance at the center frequency in the differential mode, and the impedance decreases when the frequency deviates from the center frequency, and is equivalent to a 6-ohm impedance in the common mode. The broadside coupled structure can be matched with the 25-ohm impedance in a wide frequency band, but cannot be matched with the 6-ohm impedance and lower impedance, so that a wideband differential mode filter response and common mode suppression can be obtained.

[0032] The transmission lines in different forms have different effects on the filter switch. The substrate integrated coaxial line mainly uses the TEM mode, and is closed in structure and small in cross-sectional size. Compared with the microstrip line technology, the stripline technology, the CPW technology and the substrate integrated waveguide technology, the substrate integrated coaxial line can balance the loss, low dispersion, size, shielding property, bandwidth and integration. The balanced substrate integrated coaxial line filter switch can switch the differential mode filter band, and can maintain effective common mode suppression in the on and off states. Therefore, the balanced substrate integrated coaxial line filter switch has important application value and engineering value.

[0033] In summary, the balanced wideband substrate integrated coaxial line filter switch has the advantages of switchable differential mode filter passband, common mode suppression and wideband operation. Since the substrate integrated coaxial line is used in the application, small size, simple structure and planar integrability can be balanced.

[0034] An embodiment of the application is listed as follows. The embodiment uses two layers of Rogers 5880 substrates 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 shown in Figures 1 to 3 , the on-state response is shown in Figure 4 , and the off-state response is shown in Figure 5 . As can be seen from Figure 4 , the center frequency is 1.8 GHz when the switch is on, the 3-dB relative bandwidth can reach 72.6%, and the minimum insertion loss is only 0.48 dB. Five transmission poles are realized, and the common mode suppression in the differential mode passband can reach more than 15 dB. As can be seen from Figure 5 , the differential mode signal isolation in the observation band can reach more than 23 dB when the switch is off, and the common mode suppression can reach more than 35 dB.

[0035] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A balanced broadband substrate integrated coaxial line filter switch, characterized in that: It 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 order from top to bottom, and also includes 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 of the horizontal metal strip (103) and the positive electrodes respectively connected to the horizontal center point of the rectangular metal ground (101); a resistor (7) is connected to the upper ends of the horizontal metal strip (103) and the vertical metal strip (104); The middle metal layer (3) is symmetrical on both sides, 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); 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) constitute 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 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 (8) are reverse biased, the top coplanar waveguide and substrate integrated coaxial line four to substrate integrated coaxial line five 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, λ 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 consisting of substrate-integrated coaxial line one to substrate-integrated coaxial line three can be equivalent to A ohm impedance at the center frequency in 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.

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