A reconfigurable multiplexer filter module

Abstract

The present invention discloses a reconfigurable multi-channel switch filter module, which includes a multi-layer printed circuit board. The adjacent two layers of printed circuit boards are bonded with a prepreg; the bottom two layers of printed circuit boards are used to transmit radio frequency signals, and the other layers are used to transmit control signals; the multi-layer printed circuit board is grooved to expose the microstrip circuit on the upper surface of the bottom printed circuit board for assembling two MMIC radio frequency switches and multiple FBAR filters; the filters are arranged between the two MMIC radio frequency switches and are cascaded with the MMIC radio frequency switches respectively; the MMIC decoder driver is arranged on the upper surface of the multi-layer printed circuit board or at the grooved part of the printed circuit board according to the actual wiring situation; the TTL signal passes through the MMIC decoder driver to control the opening of a channel of the MMIC radio frequency switch; by changing the TTL signal, the required switch channel and the FBAR filter are switched to achieve frequency band selection. The present invention has the advantages of small volume, low insertion loss, high isolation, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave radio frequency circuits, and particularly relates to a reconfigurable multi-channel switch filter module. Background Art

[0002] Frequency synthesizers are core components of electronic systems such as communication, radar, electronic reconnaissance and countermeasure, and precision measuring instruments, and are key devices determining the performance of electronic systems. With the development of modern wireless communication, systems such as mobile communication, radar, guided weapons, and electronic countermeasure have put forward increasingly high requirements for frequency synthesizers. As an important part of frequency synthesizers, switch filter banks determine the spurious suppression ratio and integration level of frequency synthesizers.

[0003] In order to reduce transmission delay, traditional frequency synthesizers usually adopt LC or dielectric filters with relatively large volume and bandwidth, which results in a relatively wide signal working bandwidth, that is, large noise power; at the same time, they usually contain multiple switch filter banks inside, which leads to a relatively large volume of frequency synthesizers. Summary of the Invention

[0004] The purpose of the present invention is to provide a reconfigurable multi-channel switch filter module with high integration, good performance, low cost, and simple assembly, which can select frequency components according to application requirements.

[0005] The technical solution for achieving the purpose of the present invention is: a reconfigurable multi-channel switch filter module, including a multi-layer printed circuit board, two MMIC radio frequency switches, multiple FBAR filters, and one MMIC decoder driver;

[0006] The multi-layer printed circuit board is successively PCB1, PCB2,..., PCBn from bottom to top, where n is the number of layers of the printed circuit board, and adjacent two-layer printed circuit boards are bonded with prepreg; the bottom two-layer printed circuit boards PCB1 and PCB2 are used to transmit radio frequency signals, and the printed circuit boards PCB3 to PCBn are used to transmit control signals; the multi-layer printed circuit board is grooved until the microstrip circuit on the upper surface of the bottom printed circuit board PCB1 is exposed, for assembling two MMIC radio frequency switches US1 to US2 and multiple FBAR filters UF1 to UFm, where m is the total number of FBAR filters; the filters UF1 to UFm are arranged between the two MMIC radio frequency switches and are respectively cascaded with the MMIC radio frequency switches US1 and US2 to form m channels of the MMIC radio frequency switch; the MMIC decoder driver is arranged on the upper surface of the multi-layer printed circuit board or at the grooved part of the printed circuit board according to the actual wiring situation;

[0007] The TTL signal passes through the MMIC decoding driver to control the opening of a channel of the MMIC radio frequency switch. After passing through the FBAR filter in this channel, the microwave radio frequency signal reduces the insertion loss within the operating frequency band and improves the rejection outside the frequency band. By changing the TTL signal, the required switch channel and the FBAR filter are switched to achieve frequency band selection.

[0008] Compared with the prior art, the present invention has the following remarkable advantages: (1) The SICL transmission structure with high quality factor and the FBAR filter are adopted, and this technology has the advantages of low insertion loss and high isolation; (2) The multilayer printed circuit board based on the SICL transmission structure is adopted, which is convenient for integrated integration. At the same time, combined with the extremely small volume of the FBAR filter, this technology has the advantages of miniaturization and easy integration; (3) The assembly of the module can be completed through the bonding process of micro-assembly and the gold wire bonding process. This technology has low requirements for assembly, and at the same time has the advantages of reconfigurability, easy later maintenance and low cost. Brief Description of the Drawings

[0009] Figure 1 It is a schematic cross-sectional structure diagram of the reconfigurable multi-channel switch filter module of the present invention.

[0010] Figure 2 It is a schematic structure diagram of the substrate integrated coaxial line in the present invention.

[0011] Figure 3 It is a schematic top view of the reconfigurable multi-channel switch filter module of the present invention. Detailed Embodiments

[0012] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0013] The present invention provides a reconfigurable multi-channel switch filter module, which includes a multi-layer printed circuit board, two MMIC (Monolithic Microwave Integrated Circuit) radio frequency switches, multiple FBAR (Film Bulk Acoustic Resonator) filters, and an MMIC decoder driver. Among them, the bottom two layers of the multi-layer printed circuit board transmit radio frequency signals, adopting a substrate integrated coaxial line structure, which has relatively small insertion loss and good anti-interference ability. The MMIC radio frequency switch adopts a single-pole multi-throw structure, with characteristics such as low insertion loss, high isolation, and fast switching. The FBAR filter has a small volume and an extremely high quality factor. The MMIC decoder driver adopts a CMOS process, and the response time is about 20 ns. The TTL signal passes through the MMIC decoder driver to control the opening of a certain channel of the MMIC radio frequency switch. After the microwave radio frequency signal passes through the FBAR filter in this channel, it has low insertion loss within the working frequency band and high suppression outside the frequency band. By changing the TTL signal, the required switch channel and FBAR filter are switched to achieve the purpose of frequency band selection (reconfigurable).

[0014] The multi-layer printed circuit board is successively PCB1, PCB2,..., PCBn from bottom to top, where n is the number of layers of the printed circuit board, and adjacent two layers of printed circuit boards are bonded with a prepreg. The bottom two layers of printed circuit boards PCB1 and PCB2 are used to transmit radio frequency signals, and the printed circuit boards PCB3 - PCBn are used to transmit control signals. The multi-layer printed circuit board is grooved until the microstrip circuit on the upper surface of the bottom printed circuit board PCB1 is exposed, which is used to assemble two MMIC radio frequency switches US1 - US2 and multiple FBAR filters UF1 - UFm, where m is the total number of FBAR filters. The filters UF1 - UFm are arranged between the two MMIC radio frequency switches and are respectively cascaded with the MMIC radio frequency switches US1 and US2 to form m channels of the MMIC radio frequency switch. The MMIC decoder driver is arranged on the upper surface of the multi-layer printed circuit board or at the grooved part of the printed circuit board according to the actual wiring situation.

[0015] The TTL signal passes through the MMIC decoder driver to control the opening of a channel of the MMIC radio frequency switch. After the microwave radio frequency signal passes through the FBAR filter in this channel, the insertion loss is reduced within the working frequency band and the suppression is improved outside the frequency band. By changing the TTL signal, the required switch channel and FBAR filter are switched to achieve frequency band selection.

[0016] As a specific embodiment, the multilayer printed circuit boards PCB1, PCB2, …, PCBn adopt microwave radio frequency boards TSM-DS3. The thermal expansion coefficients of the boards of the microwave radio frequency board TSM-DS3 in the x, y, and z directions are all lower than the set values, meeting the conditions for directly bonding MMIC bare chips on vias; the lower surface of PCB1 is plated with thin gold, with a gold thickness of 0.13 - 0.45 um for soldering; the upper surfaces of PCB1 - PCBn are plated with nickel-gold, with a nickel thickness of 1.3 - 5 um and a gold thickness of 2 - 3 um for bonding.

[0017] As a specific embodiment, the microwave radio frequency boards TSM-DS3 of the multilayer printed circuit boards are bonded by prepregs PP1, PP2, …, PPn-1. The thickness of the prepregs is 0.05 mm, and the difference in dielectric constant between the prepregs and the multilayer printed circuit boards TSM-DS3 is within the threshold range; the multilayer printed circuit boards are connected by metallized vias v1 to transmit control signals.

[0018] As a specific embodiment, the bottom two printed circuit boards PCB1 and PCB2 are used to transmit radio frequency signals and adopt a substrate integrated coaxial line structure, that is, a column of metallized vias v3 are respectively introduced on both sides of the microstrip line. By setting the width w a of the internal transmission line of the microstrip line and the thickness h of the upper and lower two layers of transmission media of the microstrip line, the characteristic impedance of the microstrip line is 50 ohms; w b is the pitch between the metallized vias v3, and w b is 5 times of w a ; vias v2 are set to make the control circuits on the printed circuit boards PCB3 - PCBn and the radio frequency transmission links on the printed circuit boards PCB1 - PCB2 share the same ground. Adopting the substrate integrated coaxial line transmission structure has smaller insertion loss and better anti-interference ability, and can improve the isolation degree between radio frequency channels inside the module.

[0019] As a specific embodiment, the MMIC radio frequency switches US1 and US2 adopt a single-pole multi-throw structure, and the required number of switch paths is selected according to the number of frequency bands, and the number of switch paths does not exceed 5; each path of the MMIC radio frequency switches US1 and US2 adopts a circuit topology structure of PIN diode series-parallel cascade to achieve; each path of control drive signal passes through a bypass capacitor to drive the MMIC radio frequency switches US1 and US2, and the bypass capacitor is 100 pF; the MMIC radio frequency switches US1 and US2 are assembled on the upper surface of the printed circuit board PCB1 through a micro-assembly bonding process and then connected to the microstrip through a gold wire bonding process. The MMIC radio frequency switches US1 and US2 can open a certain channel within the operating frequency band, and this channel has smaller insertion loss, and other channels are turned off, with good isolation; the switch switching speed is about dozens of nanoseconds.

[0020] As a specific embodiment, the total number m of the FBAR filters is 5, which are FBAR filters UF1, UF2, …, UF5 in sequence. The operating frequency band is selected as required, and in the entire 1 - 8 GHz range, the quality factor is above 1000, the temperature drift does not exceed 30×10 -6 / ℃, and the volume does not exceed 1 mm 3 , having characteristics such as an extremely small volume, low insertion loss, high suppression of adjacent frequencies, and low temperature drift; the FBAR filters are assembled on the upper surface of the printed circuit board PCB1 through a micro-assembly bonding process, and then connected to the microstrip through a gold wire bonding process.

[0021] As a specific embodiment, the FBAR filters UF1, UF2, …, UF5 are respectively cascaded with the RF switches US1 and US2 through gold wires, microstrips, substrate integrated coaxial lines, microstrips, and gold wires.

[0022] As a specific embodiment, the MMIC decoder driver uses a CMOS process, has low power consumption, and the highest operating frequency is 50 MHz; the MMIC decoder driver decodes 3-bit TTL signals into multiple required control and drive signals to drive the MMIC RF switch, and the response time is about 20 ns; unused input terminals are connected to low or high levels, and unused output terminals are left floating and not grounded; the back of the MMIC decoder driver chip is floating and not grounded; the MMIC decoder driver is assembled on the upper surface of PCBn through a micro-assembly bonding process and is connected to the peripheral circuit using a gold wire or aluminum wire bonding process.

[0023] In the reconfigurable multi-channel switch filter module of the present invention, the MMIC RF switch, FBAR filter, and MMIC decoder driver can all be installed on a multi-layer printed circuit board through a micro-assembly bonding process and connected to the external circuit through gold wire bonding. The assembly requirements are low, which is convenient for customizing the required switch filter module as needed and for later maintenance. The TTL signal passes through the MMIC decoder driver to control the opening of a certain channel of the MMIC RF switch. After the microwave RF signal passes through the FBAR filter in this channel, it has low insertion loss within the operating frequency band and high suppression outside the frequency band; by changing the TTL signal, the required switch channel and FBAR filter are switched to achieve the purpose of frequency band selection; the switching time required for frequency band selection is within 150 ns.

[0024] The present invention has advantages such as a small volume, low insertion loss, and high isolation, has low requirements for assembly and application, has strong applicability, is convenient for later maintenance, does not require a high cost, and is applicable to high-performance miniaturized frequency synthesizers.

[0025] The following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments.

[0026] Embodiment

[0027] AsFigure 1 As shown, the multi-layer printed circuit boards PCB1, PCB2, …, PCBn adopt microwave radio frequency boards TSM-DS3. The thermal expansion coefficients of this board material in the x, y, and z directions are extremely low, and MMIC bare chips can be directly bonded on the vias. The lower surface of PCB1 is plated with thin gold, with a gold thickness of 0.13 - 0.45 um to ensure soldering. The upper surface of PCB1 is plated with nickel-gold, with a nickel thickness of 1.3 - 5 um and a gold thickness of 2 - 3 um to ensure bonding. The upper surface of PCBn is plated with nickel-gold, with a nickel thickness of 1.3 - 5 um and a gold thickness of 2 - 3 um to ensure bonding. The number of layers n of the multi-layer printed circuit board is determined by the wiring requirements, usually not less than 3 layers. The bottom two layers transmit radio frequency signals, and the other layers are used to transmit control signals.

[0028] Furthermore, the multi-layer printed circuit boards and the microwave radio frequency boards TSM-DS3 are bonded through prepregs PP1, PP2, …, PPn-1. The dielectric constant of the prepreg needs to be close to that of the multi-layer printed circuit board TSM-DS3, and the thickness should be as thin as possible, generally 0.05 mm, to reduce the influence of the prepreg on the characteristic impedance of the transmission structure. The multi-layer printed circuit boards are connected through metallized vias v1 to transmit control signals.

[0029] Furthermore, the multi-layer printed circuit board needs to be grooved until the microstrip circuit on the upper surface of PCB1 is exposed, for bonding microwave radio frequency chips such as MMIC radio frequency switches USi and FBAR filters UFi.

[0030] Furthermore, as Figure 2 shown, for the multi-layer printed circuit board, PCB1 and PCB2 transmit radio frequency signals and are the bottom two layers of the multi-layer printed circuit board. They adopt a substrate integrated coaxial line (SICL) transmission structure, that is, a column of metallized vias v3 are introduced on each side of the stripline. Among them, w a is the width of the internal transmission line of the stripline, h is the thickness of the transmission medium between the upper and lower layers of the stripline. By setting w a and h, the characteristic impedance of the stripline is made 50 ohms; w b is the spacing between the introduced metallized vias v3, usually 5 times of w a , forming a similar closed structure, thus having a smaller insertion loss and better anti-interference ability, and can improve the isolation degree between the radio frequency channels inside the module. If necessary, by setting via v2, the above circuit can be grounded with the radio frequency transmission link.

[0031] Furthermore, for the MMIC RF switches US1 and US2, the required number of switch paths is selected according to the number of frequency bands, usually not exceeding 5 paths. Too many switch paths may lead to overly compact RF line routing. Each path of US1 and US2 adopts a series-parallel cascaded circuit topology of PIN diodes to achieve low insertion loss and high isolation at the same time. The on-off time of each path of the switch is about several tens of nanoseconds. Each path of the control drive signal needs to pass through a bypass capacitor and then drive US1 and US2. This capacitor cannot affect the switch switching speed and is usually 100 pF. US1 and US2 are assembled on the upper surface of PCB1 through a microassembly bonding process and then connected to the microstrip through a gold wire bonding process.

[0032] Furthermore, for the FBAR filters UF1, UF2, …, UF5, the operating frequency band is selected as needed. Throughout the range of 1 - 8 GHz, the quality factor is above 1000, with extremely low temperature drift, not exceeding 30×10 -6 / ℃, and the volume does not exceed 1 mm 3 ; within the operating frequency band, it has a small insertion loss, and at the near frequency (as low as several tens of MHz), it can achieve an attenuation of about 40 dB; similar to the above-mentioned MMIC RF switches, it can be assembled on the upper surface of PCB1 through a microassembly bonding process and then connected to the microstrip through a gold wire bonding process.

[0033] Furthermore, as Figure 3 shown, the FBAR filters UF1, UF2, …, UF5 are respectively located between US1 and US2 and are cascaded with the RF switches US1 and US2 through gold wires, microstrips, SICL, microstrips, and gold wires. The number of FBAR filters is related to the number of channels of US1 and US2.

[0034] Furthermore, the MMIC decoder driver UD1 adopts a CMOS process, with low power consumption, and the highest operating frequency can reach 50 MHz; it can decode 3-bit TTL signals into multiple required control drive signals; unused input terminals should not be left floating and should be connected to low or high level; unused output terminals should be left floating and should not be grounded; the back of the chip should be left floating and should not be grounded; it is recommended that the current of the control drive signal should not be higher than 50% of the typical operating current; UD1 is assembled on the upper surface of PCBn through a microassembly bonding process and is connected to the peripheral circuit by gold wire or aluminum wire bonding depending on the material of the PAD.

[0035] Furthermore, for the microassembly bonding process, the principle of facilitating installation, replacement, and maintenance should be followed, and appropriate conductive adhesives and curing temperatures should be selected.

[0036] Furthermore, in the miniaturization technology of the reconfigurable switched filter bank, the TTL signal passes through the UD1 decoder driver and is decoded into multiple drive control signals. These signals drive US1 and US2 through current-limiting resistors and bypass capacitors, simultaneously opening a certain channel Pathi and turning off all other channels. The RF signal enters from P1, passes through US1, Pathi, UFi, and US2, and then exits from P2. By changing the TTL signal, the channel Pathi and the FBAR filter UFi are selected to achieve the purpose of frequency band selection.

[0037] Furthermore, in the miniaturization technology of the reconfigurable switched filter bank, the insertion loss within the working bandwidth is < 4 dB, the suppression ratio at near frequencies (not higher than 50 MHz) is not less than 40 dBc, and the switching time for frequency band selection does not exceed 150 ns.

[0038] The present invention describes a miniaturization technology of a reconfigurable multi-channel switched filter bank. By adopting a SICL transmission structure with an extremely high quality factor and FBAR filters, it achieves low insertion loss in the working frequency band, and can reach a relatively high suppression ratio at near frequencies (tens of MHz). The assembly and use of the module can be completed through the bonding process of micro-assembly and the gold wire bonding process. This technology has low requirements for assembly and application, strong applicability, is convenient for later maintenance, and does not require high costs. It is applicable to high-performance miniaturized frequency synthesizers.

[0039] The embodiments described above only represent the implementation modes of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A reconfigurable multiplexer filter module, characterized in that It includes a multi-layer printed circuit board, two MMIC RF switches, multiple FBAR filters, and one MMIC decoder driver; The multi-layer printed circuit board successively includes PCB1, PCB2, …, PCBn from bottom to top, where n is the number of layers of the printed circuit board, and adjacent two-layer printed circuit boards are bonded with a prepreg; the bottom two-layer printed circuit boards PCB1 and PCB2 are used to transmit RF signals, and the printed circuit boards PCB3~PCBn are used to transmit control signals; the multi-layer printed circuit board is grooved until the microstrip circuit on the upper surface of the bottom printed circuit board PCB1 is exposed, for assembling two MMIC RF switches US1~US2 and multiple FBAR filters UF1~UFm, where m is the total number of FBAR filters; the filters UF1~UFm are arranged between the two MMIC RF switches and are respectively cascaded with the MMIC RF switches US1 and US2 to form m channels of the MMIC RF switch; The MMIC decoder driver is arranged on the upper surface of the multi-layer printed circuit board or at the grooved part of the printed circuit board according to the actual wiring situation; The TTL signal passes through the MMIC decoder driver to control the opening of one channel of the MMIC RF switch. After the microwave RF signal passes through the FBAR filter in this channel, the insertion loss is reduced within the working frequency band, and the rejection is improved outside the frequency band; by changing the TTL signal, the required switch channel and FBAR filter are switched to achieve frequency band selection; The two printed circuit boards PCB1 and PCB2 at the bottom are used to transmit radio frequency signals and adopt a substrate integrated coaxial line structure, that is, a column of metallized vias v3 are introduced on each side of the stripline, and by setting the width of the internal transmission line of the stripline w a and the thickness of the transmission media on the upper and lower layers of the stripline h the characteristic impedance of the stripline is made 50 ohms; w b is the pitch between the metallized vias v3, w b is w a 5 times that of; Through holes v2 are set to make the control circuits on the printed circuit boards PCB3~PCBn and the radio frequency transmission link on the printed circuit boards PCB1~PCB2 achieve common grounding.

2. The reconfigurable multiplexer filter module according to claim 1, wherein The multi-layer printed circuit boards PCB1, PCB2, …, PCBn use the microwave RF board TSM-DS3. The thermal expansion coefficients of the board material of the microwave RF board TSM-DS3 in the x, y, and z directions are all lower than the set value, meeting the condition of directly bonding the MMIC bare chip on the via; the lower surface of PCB1 is plated with thin gold with a gold thickness of 0.13~0.45um for soldering; the upper surfaces of PCB1~PCBn are plated with nickel-gold with a nickel thickness of 1.3~5um and a gold thickness of 2~3um for bonding.

3. The reconfigurable multiplexer filter module according to claim 2, wherein The microwave RF boards TSM-DS3 of the multi-layer printed circuit board are bonded through prepregs PP1, PP2, …, PPn-1. The thickness of the prepreg is 0.05mm, and the difference between the dielectric constant of the prepreg and the dielectric constant of the multi-layer printed circuit board TSM-DS3 is within the threshold range; the multi-layer printed circuit boards are connected through metallized vias v1 to transmit control signals.

4. The reconfigurable multiplexer filter module according to claim 3, wherein The MMIC RF switches US1 and US2 adopt a single-pole multi-throw structure, and the required number of switch paths is selected according to the number of frequency bands, and the number of switch paths does not exceed 5; each path of the MMIC RF switches US1 and US2 adopts a circuit topology structure of PIN tube series-parallel cascade to achieve; each path of control drive signal passes through a bypass capacitor to drive the MMIC RF switches US1 and US2, and the bypass capacitor is 100pF; the MMIC RF switches US1 and US2 are assembled on the upper surface of the printed circuit board PCB1 through a micro-assembly bonding process and then connected to the microstrip through a gold wire bonding process.

5. The reconfigurable multiplexer filter module according to claim 3, wherein, The total number m of the FBAR filters is 5, which are the FBAR filters UF1, UF2, …, UF5 in sequence. The operating frequency band is selected as required, and the quality factor is above 1000 throughout the range of 1 to 8 GHz, the temperature drift does not exceed 30×10 -6 / ℃, and the volume does not exceed 1 mm 3 ; The FBAR filters are assembled on the upper surface of the printed circuit board PCB1 through the micro-assembly bonding process and then connected to the microstrip through the gold wire bonding process.

6. The reconfigurable multiplexer filter module according to claim 5, wherein The FBAR filters UF1, UF2, …, UF5 are respectively cascaded with the RF switches US1 and US2 through gold wires, microstrips, substrate integrated coaxial lines, microstrips, and gold wires.

7. The reconfigurable multiplexer filter module according to claim 5, wherein The MMIC decoder driver adopts the CMOS process and has a maximum operating frequency of 50 MHz. The MMIC decoder driver decodes 3-bit TTL signals into multiple required control and drive signals. The unused input terminals are connected to low or high levels, and the unused output terminals are left floating without grounding. The back of the MMIC decoder driver chip is left floating without grounding. The MMIC decoder driver is assembled on the upper surface of the PCBn through a micro-assembly bonding process and is connected to the peripheral circuit by using a gold wire or aluminum wire bonding process.

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