A frequency hopping bandpass filter

Abstract

The application relates to the technical field of communication, in particular to a frequency hopping band-pass filter, which has a substrate, a coupling microstrip line arranged on the substrate, two variable capacitance diodes arranged on the coupling microstrip line, and feeding ports arranged on the left and right sides of the substrate. In the application, the coupling microstrip line is arranged on the substrate in a bending form, so that the size of the filter is reduced, and the influence of the filter on the communication quality of the whole system and equipment in the wireless communication system is reduced.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and specifically to a frequency hopping bandpass filter. Background Technology

[0002] With the advent of the information age, human society's demands for communication technology are constantly increasing. Driven by these demands, modern communication technology, especially wireless communication technology, is advancing rapidly. From third-generation to fourth-generation communication technology, and now to the 5G era of the Internet of Things, human wireless communication technology has undergone generation after generation of updates and developments. In long-distance wireless communication systems, the operating frequency is often in the microwave band, i.e., 300MHz to 300GHz. As we all know, the limited nature of frequency resources determines their preciousness. Limited spectrum resources and increasing communication demands make the allocation and utilization of frequency bands a challenge. Therefore, in practical applications, different communication scenarios will restrict the use of different frequency bands. In microwave communication systems, microwave filters play the role of limiting the frequency band of communication signals.

[0003] Microwave filters, as two-port networks that allow signals to pass through the passband while providing stopband rejection, have key performance indicators including center frequency, passband insertion loss, in-band ripple, and out-of-band rejection. These can typically be obtained from the filter's attenuation characteristic curve. The signal transmission efficiency through the filter depends on the insertion loss, while in-band ripple affects the stability of the transmitted signal, and out-of-band rejection minimizes interference between signals of different frequencies. Furthermore, the size of the filter significantly impacts the communication quality of the entire system and equipment in wireless communication systems. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a frequency hopping bandpass filter to overcome the problem that current filters are too large and affect the communication quality of the entire system and equipment in wireless communication systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A frequency-hopping bandpass filter includes a substrate, a coupling microstrip line disposed on the substrate, two varactor diodes disposed on the coupling microstrip line, and feed ports disposed on the left and right sides of the substrate.

[0007] The coupled microstrip line is arranged on the substrate in a bent form. A shorting wire is connected to the center of the upper microstrip line of the coupled microstrip line, forming a T-shaped structure with the microstrip line. Two varactor diodes are respectively arranged on both sides of the center of the upper microstrip line of the coupled microstrip line, with the anodes of the two varactor diodes facing the center. The center of the lower microstrip line of the coupled microstrip line is left blank for 2 mm. Two parallel thin straight microstrip lines are provided at the center blank of the lower microstrip line of the coupled microstrip line. The upper thin straight microstrip line is connected to the microstrip line to the left of the center blank, and the lower thin straight microstrip line is connected to the microstrip line to the right of the center blank.

[0008] Furthermore, in the frequency hopping bandpass filter described above, the substrate is an FR4 substrate.

[0009] Furthermore, in the frequency hopping bandpass filter described above, the width of the lower microstrip line in the coupled microstrip line is 0.72 mm.

[0010] Furthermore, in the frequency-hopping bandpass filter described above, the coupled microstrip line is disposed on the substrate in a bent form, comprising:

[0011] The coupled microstrip line is arranged on the substrate with five right-angle bends.

[0012] Furthermore, in the frequency hopping bandpass filter described above, the substrate has a length of 46.73 mm, a width of 8.5 mm, and a thickness of 0.4 mm.

[0013] Furthermore, in the frequency-hopping bandpass filter described above, the coupled microstrip line is disposed on the substrate in a bent form, comprising:

[0014] The coupled microstrip line is arranged on the substrate by being bent three times in a right-angle manner.

[0015] Furthermore, in the frequency hopping bandpass filter described above, the substrate has a length of 40.2 mm, a width of 18.27 mm, and a thickness of 0.4 mm.

[0016] Furthermore, the frequency-hopping bandpass filter described above includes:

[0017] The coupled microstrip line uses two 45-degree rounded bends instead of right-angle bends.

[0018] Furthermore, in the frequency hopping bandpass filter described above, the substrate has a length of 31.17 mm, a width of 16.94 mm, and a thickness of 0.4 mm.

[0019] The beneficial effects of the frequency hopping bandpass filter of the present invention are as follows:

[0020] This application includes a substrate, a coupled microstrip line disposed on the substrate, two varactor diodes disposed on the coupled microstrip line, and feed ports disposed on the left and right sides of the substrate. The coupled microstrip line is disposed on the substrate in a bent form, and a shorting wire is connected to the center position of the upper microstrip line of the coupled microstrip line, forming a T-shaped structure with the microstrip line. The two varactor diodes are respectively disposed on both sides of the center position of the upper microstrip line of the coupled microstrip line, and the anodes of the two varactor diodes face the center position. The center position of the lower microstrip line of the coupled microstrip line has a 2 mm gap, and two parallel thin straight microstrip lines are provided at the center gap of the lower microstrip line of the coupled microstrip line. The upper thin straight microstrip line is connected to the microstrip line on the left side of the center gap, and the lower thin straight microstrip line is connected to the microstrip line on the right side of the center gap. In this application, by disposing of the coupled microstrip line on the substrate in a bent form, the size of the filter is reduced, thereby reducing the impact on the communication quality of the entire system and device in the wireless communication system caused by the filter being too large. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a structural diagram of an embodiment of a frequency-hopping bandpass filter provided by the present invention;

[0023] Figure 2 This is an equivalent circuit diagram provided in one embodiment of a frequency hopping bandpass filter according to the present invention;

[0024] Figure 3 This is a structural diagram of an embodiment of a frequency-hopping bandpass filter provided by the present invention;

[0025] Figure 4 This is a structural diagram of an embodiment of a frequency-hopping bandpass filter provided by the present invention;

[0026] Figure 5 This is a simulation result diagram provided by an embodiment of the frequency hopping bandpass filter of the present invention;

[0027] Figure 6 This is a simulation result diagram provided by an embodiment of the frequency hopping bandpass filter of the present invention;

[0028] Figure 7 This is a simulation result diagram provided by an embodiment of the frequency hopping bandpass filter of the present invention;

[0029] Figure 8 This is a simulation result diagram provided by an embodiment of a frequency hopping bandpass filter according to the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] With the advent of the information age, human society's demands for communication technology are constantly increasing. Driven by these demands, modern communication technology, especially wireless communication technology, is advancing rapidly. From third-generation to fourth-generation communication technology, and now to the 5G era of the Internet of Things, human wireless communication technology has undergone generation after generation of updates and developments. In long-distance wireless communication systems, the operating frequency is often in the microwave band, i.e., 300MHz to 300GHz. As we all know, the limited nature of frequency resources determines their preciousness. Limited spectrum resources and increasing communication demands make the allocation and utilization of frequency bands a challenge. Therefore, in practical applications, different communication scenarios will restrict the use of different frequency bands. In microwave communication systems, microwave filters play the role of limiting the frequency band of communication signals.

[0032] Microwave filters, as two-port networks that allow signals to pass through the passband while providing stopband rejection, have key performance indicators including center frequency, passband insertion loss, in-band ripple, and out-of-band rejection. These can typically be obtained from the filter's attenuation characteristic curve. The signal transmission efficiency through the filter depends on the insertion loss, while in-band ripple affects the stability of the transmitted signal, and out-of-band rejection minimizes interference between signals of different frequencies. Furthermore, the size of the filter significantly impacts the communication quality of the entire system and equipment in wireless communication systems.

[0033] In view of this, the purpose of the present invention is to provide a frequency hopping bandpass filter to overcome the problem that current filters are too large and affect the communication quality of the entire system and equipment in wireless communication systems.

[0034] Figure 1 This is a structural diagram of an embodiment of a frequency-hopping bandpass filter according to the present invention, as shown below. Figure 1 As shown, a frequency hopping bandpass filter includes a substrate 1, a coupling microstrip line 2 disposed on the substrate 1, two varactor diodes 4 disposed on the coupling microstrip line 2, and feed ports 3 disposed on the left and right sides of the substrate 1.

[0035] The coupled microstrip line 2 is disposed on the substrate 1 in a bent form. A shorting wire is connected to the center of the upper microstrip line in the coupled microstrip line 2, forming a T-shaped structure with the microstrip line. Two varactor diodes 4 are respectively disposed on both sides of the center of the upper microstrip line in the coupled microstrip line 2, with the anodes of the two varactor diodes 4 facing the center. The center of the lower microstrip line in the coupled microstrip line 2 is left blank for 2 mm. Two parallel thin straight microstrip lines are provided at the center blank of the lower microstrip line in the coupled microstrip line 2. The upper thin straight microstrip line is connected to the microstrip line on the left side of the center blank, and the lower thin straight microstrip line is connected to the microstrip line on the right side of the center blank.

[0036] This embodiment includes a substrate 1, a coupled microstrip line 2 disposed on the substrate 1, two varactor diodes 4 disposed on the coupled microstrip line 2, and feed ports 3 disposed on the left and right sides of the substrate 1. The coupled microstrip line 2 is disposed on the substrate 1 in a bent manner, and a shorting wire is connected to the center position of the upper microstrip line of the coupled microstrip line 2, forming a T-shaped structure with the microstrip line. The two varactor diodes 4 are respectively disposed on both sides of the center position of the upper microstrip line of the coupled microstrip line 2, with the anodes of the two varactor diodes 4 facing the center position. The center of the lower microstrip line in line 2 has a 2 mm gap. Two parallel thin, straight microstrip lines are located at the center gap of the lower microstrip line in the coupling microstrip line 2. The upper thin, straight microstrip line is connected to the microstrip line to the left of the center gap, and the lower thin, straight microstrip line is connected to the microstrip line to the right of the center gap. In this application, by setting the coupling microstrip line 2 in a bent form on the substrate 1, the size of the filter is reduced, thereby reducing the impact on the communication quality of the entire system and device in the wireless communication system caused by the filter being too large.

[0037] like Figure 2 The diagram shows an equivalent circuit of an embodiment of a frequency-hopping bandpass filter, proposing an equivalent structure for STDR. The compact microstrip filter structure with a rounded-corner curved coupling microstrip line 2 is loaded by two variable capacitors Ct, the electrical length of the variable capacitor loading position from the center plane being θ1. θ3 is a variable related to θ1; for ease of calculation, the difference between the constant value of the bending angle and θ1 is denoted as θ3.

[0038] The formula for calculating the input admittance is as follows:

[0039]

[0040]

[0041]

[0042] Under resonance conditions:

[0043]

[0044] Based on the above formula, by changing θ1 and θ2, the even / odd resonant frequencies fe / fo can be obtained, and thus the center frequency fr can be obtained.

[0045] f r =(f0+f e ) / 2

[0046] Therefore, the center frequency of the proposed compact bandpass filter can be easily controlled.

[0047] Preferably, substrate 1 is FR4 substrate 1. The relationship between the characteristic impedance of the microstrip line and the dielectric constant of the dielectric substrate 1 is as follows:

[0048] ε r Let h be the dielectric constant of substrate 1, t be the thickness of substrate 1, t be the thickness of the microstrip line, and W be the linewidth. The characteristic impedance of the microstrip line changes with the dielectric constant of substrate 1; therefore, changing the substrate material will result in changes to the frequency characteristics of the filter. Within the same dimensions, the center frequency of the filter increases as the dielectric constant decreases, and the bandwidth also increases. Therefore, it is advisable to increase the dielectric constant of substrate 1 and reduce the structural size of the filter to achieve the same attenuation characteristics. FR4 is selected as the substrate material for substrate 1. FR4 is a common substrate material with a dielectric constant of 4.2 and a loss tangent of 0.02. The thickness of substrate 1 is set to 0.4 mm.

[0049] Preferably, the width of the lower microstrip line in the coupled microstrip line 2 is 0.72 mm. In RF impedance matching, considering various factors, the standard impedance matching value is often considered to be 50Ω in engineering fields. Using the relationship between the dielectric constant of the substrate 1 and the impedance of the coupled microstrip line 2, and the dielectric constant of FR4, the width of the lower microstrip line in the coupled microstrip line 2 under a characteristic impedance of 50Ω can be calculated to be 0.72 mm.

[0050] In some alternative embodiments, such as Figure 1 As shown, the coupling microstrip line 2 is disposed on the substrate 1 in a bent form, including five right-angle bends. The large length of the long straight coupling line will affect the miniaturization of the actual microwave system equipment. Therefore, after changing the dielectric material, the next step is to change the shape of the coupling microstrip line 2 from a long straight type to a bent type, bend the long straight coupling line five times, and place the feed port of the feed line on the left and right sides.

[0051] In practical application, after optimizing the filter's size parameters using HFSS simulation software, the following results were obtained: Figure 3 The filter structure has the following dimensions: length 46.73 mm, width 8.5 mm, and height 0.4 mm.

[0052] Figure 5 The simulation results of the filter after five bends in the coupling line show that the insertion loss and return loss in the passband are significantly worse after the bends. This may be because the bends in the middle of the line are too dense, resulting in an excessively large coupling capacitance. Reducing the number of bends could decrease the coupling effect.

[0053] In some alternative embodiments, such as Figure 3 As shown, the coupled microstrip line is disposed on the substrate 1 in a bent manner, including being disposed on the substrate 1 by three right-angle bends. In specific practice, Figure 6 The simulation results of the filter after three bends in the coupling line are shown, and compared. Figure 5 and Figure 6 Simulation results show that the filter performance of the two schemes is not significantly different, and the insertion loss and return loss are still poor. However, the cause must be the bending of the coupling lines. Excluding the possibility of excessive density in the middle section, the problem likely stems from the right-angle loss caused by coupling and bending between the two vertically coupled microstrip lines. To address this issue, the distance between the two vertically coupled microstrip lines can be increased to reduce coupling.

[0054] Preferably, the substrate 1 has a length of 40.2 mm, a width of 18.27 mm, and a thickness of 0.4 mm.

[0055] Specifically, coupling occurs because the longitudinal spacing of the coupling segments is too small. Therefore, the longitudinal distance between the segments is increased, and the spacing between the left and right portions of the filter's feed line is adjusted. The optimal values ​​are obtained by scanning and analyzing the variables using the Optimetrics function in the software. The optimized filter, based on three bends, has substrate 1 dimensions of 40.2 mm in length, 18.27 mm in width, and 0.4 mm in height.

[0056] from Figure 7 Simulation results are presented after adjusting the spacing between the two segments of the coupled microstrip line. Comparing the S-curve with the unoptimized version, it is evident that increasing the distance between the two segments of the longitudinally coupled microstrip line significantly reduces the coupling between them, thereby effectively reducing filter loss.

[0057] Preferably, such as Figure 4 As shown, the coupled microstrip line uses two 45-degree rounded bends instead of right-angle bends.

[0058] Impedance mismatch in coupled microstrip line 2 causes signal reflection, increasing return loss. In right-angle routing, the microstrip line width changes at the corner, causing impedance discontinuities and further increasing signal reflection. Simultaneously, right-angle routing of coupled microstrip line 2 generates a capacitive loading effect at the corner, slowing signal rise. In this situation, two improvement methods can be adopted: one is to replace the 90-degree corner with two 45-degree corners; the other is to replace the right-angle routing with rounded corners. Of these two methods, rounded corners cause less signal reflection than 45-degree corners, and reducing the corner angle decreases the capacitive loading effect of coupled microstrip line 2.

[0059] Preferably, the substrate 1 has a length of 31.17 mm, a width of 16.94 mm, and a thickness of 0.4 mm.

[0060] Compared to the initial filter, there is still room for optimization in the filter's loss. Analysis can be used to optimize the antenna radiation effect of the filter-coupled microstrip line 2, specifically by controlling the line length to maintain a certain ratio to the signal wavelength.

[0061] Based on the filter's line length and center frequency, the required length of the half-wavelength coupled microstrip line 2 is obtained. Using the Optimetrics function in the simulation software, the line length is reduced within the range of 0-1.5 mm to perform a parameter sweep and obtain the optimal solution.

[0062] After optimizing the length of the coupled microstrip line 2, the dimensions of the filter substrate 1 are: length 31.17 mm, width 16.94 mm, height 0.4 mm. This significantly reduces the filter size compared to the filter with the long, straight coupled microstrip line 2. Figure 8 The simulation results show that the antenna radiation response has been significantly improved, and the performance of the filter has also been significantly enhanced.

[0063] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0064] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0065] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A frequency-hopping bandpass filter, characterized in that, Includes a substrate, a coupled microstrip line disposed on the substrate, two varactor diodes disposed on the coupled microstrip line, and power supply ports disposed on the left and right sides of the substrate. The coupled microstrip line is arranged on the substrate in a bent form. A shorting wire is connected to the center of the upper microstrip line of the coupled microstrip line, forming a T-shaped structure with the microstrip line. Two varactor diodes are respectively arranged on both sides of the center of the upper microstrip line of the coupled microstrip line, with the anodes of the two varactor diodes facing the center. The center of the lower microstrip line of the coupled microstrip line is left blank for 2 mm. Two parallel thin straight microstrip lines are provided at the center blank of the lower microstrip line of the coupled microstrip line. The upper thin straight microstrip line is connected to the microstrip line to the left of the center blank, and the lower thin straight microstrip line is connected to the microstrip line to the right of the center blank.

2. The frequency-hopping bandpass filter according to claim 1, characterized in that, The substrate is an FR4 substrate.

3. The frequency-hopping bandpass filter according to claim 2, characterized in that, The width of the lower microstrip line in the coupled microstrip line is 0.72 mm.

4. The frequency-hopping bandpass filter according to claim 3, characterized in that, The coupled microstrip line is disposed on the substrate in a bent form, including: The coupled microstrip line is arranged on the substrate with five right-angle bends.

5. The frequency-hopping bandpass filter according to claim 4, characterized in that, The substrate has a length of 46.73 mm, a width of 8.5 mm, and a thickness of 0.4 mm.

6. The frequency-hopping bandpass filter according to claim 3, characterized in that, The coupled microstrip line is disposed on the substrate in a bent form, including: The coupled microstrip line is arranged on the substrate by being bent three times in a right-angle manner.

7. The frequency-hopping bandpass filter according to claim 6, characterized in that, The substrate has a length of 40.2 mm, a width of 18.27 mm, and a thickness of 0.4 mm.

8. The frequency-hopping bandpass filter according to claim 6, characterized in that, include: The coupled microstrip line uses two 45-degree rounded bends instead of right-angle bends.

9. The frequency-hopping bandpass filter according to claim 8, characterized in that, The substrate has a length of 31.17 mm, a width of 16.94 mm, and a thickness of 0.4 mm.

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