A frequency and bandwidth reconfigurable diplexer based on sisl structure

Abstract

The present application belongs to the technical field of microwave devices, and specifically provides a frequency and bandwidth reconfigurable diplexer based on SISL structure, to fill the research gap of the prior art. The present application uses SISL technology to realize the miniaturization and self-packaging of the overall structure, and in each channel of the reconfigurable triple-diplexer resonant circuit, a two-step ladder impedance mixed coupling resonator loaded with a variable capacitor is used, the resonant frequency adjustment is realized by loading the frequency adjustment variable capacitor on the adjacent short-circuit end, and the bandwidth adjustment is realized by loading the bandwidth adjustment variable capacitor between the two-step resonators. Thus, the frequency and bandwidth reconfigurable diplexer based on SISL proposed by the present application realizes the simultaneous adjustment of both with a simple structure and an efficient method, and because it has the bandwidth adjustable characteristic, it has a wider center frequency adjustable range, and at the same time, it has a certain guiding significance for the research of other low-loss, self-shielded diplexers and multiplexers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave devices, and particularly provides a frequency and bandwidth reconfigurable diplexer based on an SISL structure. BACKGROUND

[0002] The main function of the diplexer is to divide a wideband input signal into two narrowband signals, which plays an extremely important role in frequency band division in mobile communication. With the rapid development of mobile communication systems, miniaturization and reconfigurable function are the mainstream trends of the development of the diplexer. The existing reconfigurable diplexer mostly adopts a microstrip open structure, which cannot effectively reduce the radiation loss and will cause electromagnetic interference to other circuit modules in the circuit system. At present, there are only a few research results on the diplexer with reconfigurable frequency and bandwidth, and the research on the reconfigurable device based on the SISL self-packaging structure is also rare. The research on the reconfigurable diplexer based on the SISL structure is almost blank. SUMMARY

[0003] The application aims to provide a frequency and bandwidth reconfigurable diplexer based on the SISL self-packaging structure to fill the research gap in the prior art. The application realizes the miniaturization and self-packaging of the overall structure by adopting the SISL technology. In each channel of the reconfigurable triple diplexer resonant circuit, a two-step ladder impedance mixed coupling resonator loaded with a variable capacitor is adopted. The resonant frequency adjustment is realized by loading the frequency adjustment variable capacitor on the adjacent short-circuit end, and the bandwidth adjustment is realized by loading the bandwidth adjustment variable capacitor between the two-step resonators. Thus, the frequency and bandwidth reconfigurable diplexer based on the SISL proposed by the application realizes the simultaneous adjustment of the two by a simple structure and an efficient method. Due to the bandwidth adjustable characteristic, the application has a wider center frequency adjustable range. Meanwhile, the application has a certain guiding significance for the research on the low-loss, self-shielded diplexer and multiplexer.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0005] A frequency and bandwidth reconfigurable microwave diplexer based on an SISL structure comprises five layers of dielectric substrates 5-1 stacked from bottom to top. The application is characterized by:

[0006] Each layer of dielectric substrate adopts a double-layer board. Rectangular windows of the same size are formed in the same position of the second dielectric substrate 2 and the fourth dielectric substrate 4. The rectangular windows penetrate the dielectric substrate and the upper and lower metal layers thereof, and form air cavities on the upper and lower surfaces of the third dielectric substrate. The upper metal layer of the third dielectric substrate is etched to form a reconfigurable triple diplexer resonant circuit opposite the air cavities, and the lower metal layer of the third dielectric substrate is provided with a rectangular window opposite the air cavities.

[0007] The reconfigurable triple-duplex resonant circuit includes: an input main feed port 3-1, a first output feed port 3-2, a second output feed port 3-3, a first adjustable filter 3-4, and a second adjustable filter 3-5; wherein, the input main feed port, the first adjustable filter, and the first output feed port constitute a first adjustable channel, and the input main feed port, the second adjustable filter, and the second output feed port constitute a second adjustable channel; the input main feed port is directly connected to both the first and second adjustable filters for power supply, and the first and second adjustable filters are directly connected to their respective output feed ports.

[0008] Furthermore, the operating frequency of the first adjustable channel is f1, and the operating frequency of the second adjustable channel is f2, and the two satisfy the relationship: f1 < f2.

[0009] Furthermore, the first adjustable filter 3-4 and the second adjustable filter 3-5 respectively include: a two-stage stepped impedance hybrid coupling resonator, two frequency-adjustable variable capacitors 3-6, two bandwidth-adjustable variable capacitors 3-7, and four DC blocking capacitors 3-8; in the two-stage stepped impedance hybrid coupling resonator, one end of the high impedance line of each resonator is grounded and short-circuited, and a frequency-adjustable variable capacitor is loaded near the short-circuited end; the two bandwidth-adjustable variable capacitors are connected in series and loaded between the low impedance lines of the two resonators; DC blocking capacitors are loaded between the bandwidth-adjustable variable capacitors and the hybrid coupling resonator, and at the signal input port and output port of the hybrid coupling resonator.

[0010] Furthermore, all variable capacitors use varactor diodes. The grounding terminal of the frequency-adjustable variable capacitor is grounded with the short-circuit terminal of the high-impedance line, while the grounding terminal of the bandwidth-adjustable variable capacitor is grounded after being connected in series with a large resistor.

[0011] Furthermore, in the first and second adjustable filters, the bias circuit of each variable capacitor adopts the method of loading a large resistor and connecting an external DC regulated power source.

[0012] Furthermore, in each adjustable channel, the resonant frequency is adjusted by controlling the frequency to regulate the magnitude of the reverse bias voltage of the varactor capacitor, and the bandwidth is adjusted by controlling the bandwidth to regulate the magnitude of the reverse bias voltage of the varactor capacitor.

[0013] It should be noted that:

[0014] In the application, the bias circuit of each variable capacitor adopts the way of loading resistance and external power supply, the bias circuit design is simple, and is beneficial to welding on the microstrip substrate; generally, the resistance value is large, so as to reduce the leakage of microwave signal, and the direct current signal is prevented from leaking to the microwave path by adding the corresponding isolation capacitor; in the two adjustable filters, the bias circuit of two bandwidth adjustment variable capacitors is arranged in the middle of the two bandwidth adjustment variable capacitors. In each adjustable channel, by changing the bias voltage of the frequency adjustment variable capacitor, the junction capacitance changes, so that the equivalent length of the resonator changes, that is, the resonant frequency is continuously and quickly adjusted; by changing the bias voltage of the bandwidth adjustment variable capacitor, the junction capacitance changes, so that the coupling coefficient between the resonators changes, that is, the reconfigurable characteristic of the bandwidth is realized.

[0015] In the application, two-step ladder hybrid impedance hybrid electromagnetic coupling structures are adopted in the first adjustable channel and the second adjustable channel, generally, at the same resonant frequency, the size of the resonator is smaller than other types, and by folding the resonant structure, the miniaturization of the whole model is realized.

[0016] In the application, the input and output ports of the first adjustable channel and the second adjustable channel adopt the way of directly connecting with the resonator for feeding, and the design of the common connection port adopts a T-shaped matching structure, which is convenient for design.

[0017] In the application, in the first adjustable filter and the second adjustable filter, the isolation capacitor loaded between the bandwidth adjustment variable capacitor and the resonator generally has a small capacitance value; on the one hand, it is beneficial to the design of the bias circuit of the variable diode between the resonators, mainly playing the role of isolating direct current voltage; on the other hand, the equivalent coupling capacitor between the resonators is reduced, so that the channel has a larger range of bandwidth adjustment.

[0018] From the working principle:

[0019] From the synthesis theory of diplexer, the design of diplexer mainly falls into two parts, one is the design of two separate filters, the other is the matching design of the common port, that is, combining the two filters together in a certain way to form a diplexer with better characteristics; in addition, for the design of reconfigurable diplexer, in addition to the above two points, the implementation method of reconfigurable function also needs to be studied. The present application is a frequency and bandwidth reconfigurable diplexer, which includes two aspects of adjustment. For the microstrip structure, the adjustment of frequency or bandwidth is mainly realized by loading PIN diode or varactor diode. Although the PIN diode can be loaded to form different tuning states, it cannot be continuously adjusted and cannot quickly and accurately reach the required center frequency or bandwidth of the system. The varactor diode can be quickly and continuously adjusted, and has more working states. Therefore, the present application adopts the varactor diode. Secondly, the key point of the design of a single channel filter lies in the selection of resonator type. In order to realize the miniaturization of the diplexer structure, the first adjustable channel and the second adjustable channel of the present application adopt two-step folded stepped impedance hybrid electromagnetic coupling resonators.

[0020] The microstrip thin line is loaded near the high impedance line short circuit end of the two resonators to connect the two resonators, forming a current loop and generating magnetic coupling between the two resonators. Since the quarter wavelength short circuit resonator has the strongest electric field distribution at its open end, the gap between the low impedance of the two resonators in the present application generates electric coupling, realizing the electromagnetic hybrid coupling between the two resonators.

[0021] In order to realize the reconfiguration of the channel bandwidth, it is noted that the expression describes the relationship between the coupling coefficient between general resonators and the channel bandwidth, wherein FBW is the percentage bandwidth of the filter, g i ,g i+1 is the prototype value of the selected low-pass filter; therefore, the coupling coefficient between resonators is in direct proportion to the bandwidth, so the varactor diode can be loaded between the resonators, and the coupling coefficient can be changed by changing the bias voltage: when the bias voltage increases, the junction capacitance of the varactor diode decreases, and the coupling coefficient becomes smaller, and the bandwidth decreases; when the bias voltage decreases, the junction capacitance of the varactor diode increases, the coupling coefficient becomes larger, and the bandwidth becomes larger, so the bandwidth of the channel can be controlled.

[0022] The frequency reconfigurable feature means that the center frequency of each channel has a certain range of adjustable characteristics, and the adjustment method is to change the bias voltage of the varactor diode loaded on the resonator, so that the equivalent length of the resonator changes, and then the resonant frequency changes.

[0023] For matching connections at the common port, special attention needs to be paid to important parameters at each feeder port, namely the quality factor, which is inversely proportional to the relative bandwidth. The quality factor is checked against the passband requirements using the group delay extraction method. In this invention, the common connection port is directly connected to the first adjustable channel and the second adjustable channel, and is coupled to the third adjustable channel. Therefore, the common matching port mainly includes the matching between the first adjustable channel and the second adjustable channel, which is simple to adjust and easy to design.

[0024] Unlike traditional suspended microstrip line structures that require an additional bulky metal cavity for encapsulation, the duplexer employs SISL technology to achieve overall miniaturization and self-encapsulation. Compared to traditional microstrip structure designs in open electromagnetic environments, the metal walls of the first and fifth layers of the SISL structure, as well as the metal vias around each dielectric substrate, can form an equivalent metal cavity, effectively reducing the duplexer's radiation loss and insertion loss. It also possesses electromagnetic shielding characteristics, ensuring no interference with other circuit structures in the system.

[0025] In summary, the beneficial effects of the present invention are as follows:

[0026] This invention provides a microwave duplexer based on a SISL structure whose center frequency and bandwidth are reconfigurable. It can simultaneously achieve continuous and rapid adjustment of the center frequency and bandwidth of each adjustable channel, and has self-encapsulation and low insertion loss characteristics. At the same time, the device has a simple structure and is easy to adjust. Attached Figure Description

[0027] Figure 1 The diagram shows a layered structure of a frequency and bandwidth reconfigurable microwave duplexer based on the SISL structure in the embodiment. In this diagram, 1 is the first dielectric substrate, 2 is the second dielectric substrate, 3 is the third dielectric substrate, 4 is the fourth dielectric substrate, and 5 is the fifth dielectric substrate.

[0028] Figure 2 for Figure 1 The diagram shows the structure of the resonant circuit in a frequency and bandwidth reconfigurable microwave duplexer based on the SISL structure. In the diagram, 3-1 is the main input feed port, 3-2 is the first output feed port, 3-3 is the second output feed port, 3-4 is the first adjustable filter, 3-5 is the second adjustable filter, 3-6 is the bandwidth-adjustable varactor diode, 3-7 is the frequency-adjustable varactor diode, 3-8 is the DC blocking capacitor, and 3-9 is the large resistor.

[0029] Figure 3 The figure shows the simulation test results of the frequency and bandwidth reconfigurable microwave duplexer in the initial state in the embodiment of the present invention.

[0030] Figure 4 Fig. 6 is a return loss and isolation result diagram of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application in the process of adjusting the frequency and bandwidth of the first channel only.

[0031] Figure 5 Fig. 7 is an insertion loss result diagram of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application in the process of adjusting the frequency and bandwidth of the first channel only.

[0032] Figure 6 Fig. 8 is a return loss and isolation result diagram of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application in the process of adjusting the frequency and bandwidth of the second channel only.

[0033] Figure 7 Fig. 9 is an insertion loss result diagram of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application in the process of adjusting the frequency and bandwidth of the second channel only.

[0034] Figure 8 Fig. 10 is an insertion loss result diagram of the first channel bandwidth adjustment of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application.

[0035] Figure 9 Fig. 11 is an insertion loss result diagram of the second channel bandwidth adjustment of the frequency and bandwidth reconfigurable microwave diplexer in the embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be given to the present application in combination with embodiments and drawings, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0037] Embodiment 1

[0038] The embodiment provides a frequency and bandwidth reconfigurable microwave diplexer based on SISL structure, which mainly functions to divide a wideband input signal into two corresponding narrowband signal outputs, has the characteristics of reconfigurable center frequency and reconfigurable channel bandwidth, each channel is a two-step impedance hybrid electromagnetic coupling resonator, by loading a varactor diode on each resonator, adjusting the junction capacitance to change the equivalent length of the resonator, and then changing the resonant frequency of the channel, secondly, because the coupling coefficient between the resonators is proportional to the bandwidth, the varactor diode is loaded between the two resonators to change the bias to change the coupling coefficient, and then the bandwidth is adjusted.

[0039] As Figure 1As shown, the frequency and bandwidth reconfigurable microwave diplexer based on SISL structure comprises: a fifth dielectric substrate 5, a fourth dielectric substrate 4, a third dielectric substrate 3, a second dielectric substrate 2 and a first dielectric substrate 1 stacked from bottom to top; wherein the upper and lower surfaces of each dielectric substrate are covered with upper and lower metal layers, and the four sides of each dielectric substrate are metal through holes connecting the upper and lower metal layers; the second dielectric substrate 2 and the fourth dielectric substrate 4 are provided with rectangular windows of the same size at the same position, the rectangular windows penetrate the dielectric substrate and its upper and lower metal layers, and form air cavities on the upper and lower surfaces of the third dielectric substrate; the upper metal layer of the third dielectric substrate is etched to form a reconfigurable three-diplexer resonant circuit opposite the air cavity, and the lower metal layer of the third dielectric substrate is provided with a rectangular window opposite the air cavity.

[0040] As shown in Figure 2 The reconfigurable three-diplexer resonant circuit comprises: an input total feeder port 3-1, a first output feeder port 3-2, a second output feeder port 3-3, a first adjustable filter 3-4 and a second adjustable filter 3-5; wherein the first adjustable channel is composed of the input total feeder port, the first adjustable filter and the first output feeder port, and the second adjustable channel is composed of the input total feeder port, the second adjustable filter and the second output feeder port; the input total feeder port is directly connected to the first adjustable filter and the second adjustable filter, and the first adjustable filter and the second adjustable filter are directly connected to the corresponding output feeder ports. The first adjustable filter 3-4 and the second adjustable filter 3-5 have similar structures and each comprises: two-step impedance mixed coupling resonators, two frequency-adjustable variable capacitors 3-6, two bandwidth-adjustable variable capacitors 3-7 and four DC blocking capacitors 3-8; in the two-step impedance mixed coupling resonator, the high impedance line of each resonator is grounded and short-circuited at one end, and a frequency-adjustable variable capacitor is loaded near the short-circuit end, two bandwidth-adjustable variable capacitors are connected in series and loaded between the low impedance lines of the two resonators, and a DC blocking capacitor is loaded between the bandwidth-adjustable variable capacitor and the mixed coupling resonator, and between the signal input port and the output port of the mixed coupling resonator.

[0041] Further, the working frequency of the first adjustable channel is f1, and the working frequency of the second adjustable channel is f2, and the relationship between them satisfies: f1 < f2.

[0042] Further, in the first adjustable filter and the second adjustable filter, the variable capacitors are all variable diodes, and the bias circuit of each variable diode is loaded with a 300Kohm resistor 3-9 and externally connected to a DC voltage source; the ground end of the frequency-adjustable variable diode is grounded with the short-circuit end of the high impedance line, and the ground end of the bandwidth-adjustable variable diode is connected in series with a large resistor 3-9 and then grounded.

[0043] Based on the above structure, the initial design center frequency of the frequency and bandwidth reconfigurable diplexer based on the SISL structure in the embodiment is set to 2.1 GHz and 2.7 GHz, the initial given capacitance values of each varactor diode are 0.9 pF and 1.8 pF respectively, the thickness of the substrate 3 is 0.254 mm, Rogers 5880 is used, and thus the specific physical size of the resonator can be determined; the thicknesses of the substrate 1 and the substrate 5 are 0.6 mm, FR4 board material is used, the thicknesses of the substrate 2 and the substrate 4 are 2 mm, FR4 board material is used; in the first adjustable filter, the length of the high impedance line of each resonator of the two-stage stepped impedance hybrid coupled resonator is L3 = 21.2 mm, the length of the low impedance line is L4 = 19.7 mm, the length of the loading position of the frequency adjustable varactor diode from the short circuit end is L1 = 5 mm, the length of the loading position of the bandwidth adjustable varactor diode from the open circuit end is L2 = 14.6 mm, the bias value of the bandwidth adjustment varactor diode is V1, and the bias value of the frequency adjustment varactor diode is V2; in the second adjustable filter, the length of the high impedance line of each resonator of the two-stage stepped impedance hybrid coupled resonator is L7 = 9 mm, the length of the low impedance line is L8 = 14.7 mm, the length of the loading position of the frequency adjustable varactor diode from the short circuit end is L5 = 5 mm, the length of the loading position of the bandwidth adjustable varactor diode from the open circuit end is L6 = 13.3 mm, the bias value of the bandwidth adjustment varactor diode is V3, and the bias value of the frequency adjustment varactor diode is V4; in each adjustable channel, the resonant frequency is adjusted by controlling the size of the bias value of the frequency adjustment varactor capacitance, and the bandwidth is adjusted by controlling the size of the reverse bias voltage of the bandwidth adjustment varactor capacitance; it should be noted that the specific positions (L1, L2, L5, L6) of the loading of the frequency adjustable varactor diode and the bandwidth adjustment varactor diode can be adaptively optimized and adjusted according to impedance matching, and the functions are not affected.

[0044] As Figures 3-9 shown, the simulation and test results of the reconfigurable microwave diplexer of the embodiment show that the center frequencies of each channel can be adjusted individually or simultaneously, and the bandwidth can also be adjusted within a certain range. Figure 3 It can be seen from the initial simulation and test results that the in-band matching of the two channels is good, and the S 11 ≤-10dB, the simulation results of the two channels are less than 0.95dB and 0.82dB respectively, and the test results of the two channels are less than 1.67dB and 1.96dB respectively. Figures 4-9 The simulation characteristics in adjusting the frequency and bandwidth of the diplexer are described, wherein Figures 4-7The simulation results of adjusting the first and second adjustable channels respectively, it is easy to know that when adjusting a channel alone, the transmission characteristics of other channels are almost not affected, specifically, the frequency adjustable range of the first channel is 1.71-2.34GHz (650MHz); the frequency adjustable range of the second channel is 2.50-3.32GHz (820MHz), and in all states of adjusting the two adjustable channels, the isolation between the ports is greater than 30dB. Figure 8 With Figure 9 To adjust the bandwidth variation of the two adjustable channels, it can be seen that when the value of C2 (the first adjustable filter bandwidth adjustment capacitor) changes from 0.5pF to 2.4pF, the bandwidth of channel one increases from 80MHz to 160MHz, and the 1dB bandwidth variation range is 80MHz. When the value of C6 (the second adjustable filter bandwidth adjustment capacitor) changes from 0.5pF to 2.4pF, the 1dB bandwidth of channel two increases from 140MHz to 290MHz, and the bandwidth variation range is 150MHz. Based on this, it is confirmed that loading a varactor diode in the low impedance gap between the two resonant channels of the diplexer can achieve the purpose of bandwidth adjustment. In summary, from the simulation results, it can be concluded that the diplexer of the present application realizes the reconfigurable function of channel frequency and bandwidth, and has the advantages of small size and low insertion loss.

[0045] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically stated; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A frequency and bandwidth reconfigurable duplexer based on a SISL structure, comprising: A five-layer dielectric substrate (5-1) stacked sequentially from bottom to top; characterized in that: Each dielectric substrate is a double-layer board. The second dielectric substrate (2) and the fourth dielectric substrate (4) have rectangular windows of the same size at the same position. The rectangular windows penetrate the dielectric substrate and its upper and lower metal layers, forming air cavities on the upper and lower surfaces of the third dielectric substrate. The upper metal layer of the third dielectric substrate is etched to form a reconfigurable triple duplexer resonant circuit facing the air cavity, and the lower metal layer of the third dielectric substrate has a rectangular window facing the air cavity. The reconfigurable triple-duplex resonant circuit includes: an input main feed port (3-1), a first output feed port (3-2), a second output feed port (3-3), a first adjustable filter (3-4), and a second adjustable filter (3-5); wherein, the input main feed port, the first adjustable filter, and the first output feed port constitute a first adjustable channel, and the input main feed port, the second adjustable filter, and the second output feed port constitute a second adjustable channel; the input main feed port is directly connected to both the first and second adjustable filters for power supply, and the first and second adjustable filters are directly connected to their respective output feed ports; The first adjustable filter (3-4) and the second adjustable filter (3-5) respectively include: a two-stage stepped impedance hybrid coupling resonator, two frequency-adjustable variable capacitors (3-6), two bandwidth-adjustable variable capacitors (3-7), and four DC blocking capacitors (3-8); in the two-stage stepped impedance hybrid coupling resonator, one end of the high impedance line of each resonator is grounded and short-circuited, and a frequency-adjustable variable capacitor is loaded near the short-circuited end. The two bandwidth-adjustable variable capacitors are connected in series and loaded between the low impedance lines of the two resonators. DC blocking capacitors are loaded between the bandwidth-adjustable variable capacitors and the hybrid coupling resonator, and between the signal input port and the output port of the hybrid coupling resonator.

2. The frequency and bandwidth reconfigurable duplexer based on SISL structure as described in claim 1, characterized in that, The operating frequency of the first adjustable channel is f1, and the operating frequency of the second adjustable channel is f2. The relationship between the two is: f1 < f2.

3. The frequency and bandwidth reconfigurable duplexer based on SISL structure as described in claim 1, characterized in that, All variable capacitors use varactor diodes. The grounding terminal of the frequency-adjustable variable capacitor is grounded with the short-circuit terminal of the high-impedance line. The grounding terminal of the bandwidth-adjustable variable capacitor is grounded after being connected in series with a large resistor.

4. The frequency and bandwidth reconfigurable duplexer based on SISL structure as described in claim 1, characterized in that, In the first and second adjustable filters, the bias circuit of each variable capacitor adopts the method of loading a large resistor and connecting an external DC regulated power source.

5. The frequency and bandwidth reconfigurable duplexer based on SISL structure as described in claim 1, characterized in that, In each adjustable channel, the resonant frequency is adjusted by controlling the frequency and the reverse bias voltage of the varactor capacitor, and the bandwidth is adjusted by controlling the bandwidth and the reverse bias voltage of the varactor capacitor.

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