WLAN frequency band channel selection narrowband high-order filter, design method and electronic device

Abstract

The present invention relates to the field of signal processing technology, and in particular to a WLAN frequency band channel selection narrowband high-order filter, design method and electronic device, the filter comprising: an input port, an output port and a resonator composed of more than five microstrip lines; the head end microstrip line of the resonator is connected to the input port, the microstrip lines of each section in the resonator are connected in series in sequence, and the end microstrip line of the resonator is connected to the output port; the resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port; the out-of-band frequency band signal outside the preset working frequency band of the original signal is suppressed by the out-of-band suppression processing to obtain a filtered signal with out-of-band suppression exceeding a preset attenuation threshold. The fast attenuation of the out-of-band signal is realized, the proportion of the out-of-band signal entering the receiving device is reduced, the demodulation capability of the receiving device for the useful signal is improved, and the system capacity and communication rate of the communication system are improved.

Description

Technical Field

[0001] The present invention relates to the field of signal processing technology, and in particular to a WLAN frequency band channel selection narrowband high-order filter, a design method and electronic equipment. Background Art

[0002] With the continuous and rapid development of economic life, the demand for communication in society will continue to increase. The era of the Internet of Things and big data is approaching. We can see the use of various handheld devices to connect to the Internet for various work, life, entertainment and other aspects. Electromagnetic waves are everywhere in life. However, if the various electromagnetic waves are not sorted out at the receiving end of the electronic device and only the required signals are allowed to enter the receiving device, then all kinds of electromagnetic waves in the environment will enter the receiving device, and the demodulation ability of the receiving device will be greatly challenged. It will not be able to demodulate the useful signal, which will lead to the inability to realize the normal function of wireless communication transmission. Therefore, it is particularly important to process the signal before the electromagnetic wave enters the receiving device.

[0003] At present, the processing method before the signal enters the receiving device is mainly to select the frequency through the antenna and select the signal through the filter. The antenna bandwidth is relatively wide. For example, there are 13 channels in the WLAN frequency band, and some channels can work at the same time. However, the existing filter bandwidth is narrow and the out-of-band suppression capability is limited. The out-of-band attenuation is usually only about 3dB / MHz, and the interference between channels is extremely large. It is necessary to design a high-performance channel selection narrowband high-order filter to achieve fast out-of-band attenuation.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The main purpose of the present invention is to provide a WLAN frequency band channel selection narrowband high-order filter, aiming to solve the technical problem that it is difficult to realize an antenna with a beam scanning function in the terahertz frequency band in the prior art.

[0006] To achieve the above-mentioned object, the present invention proposes a WLAN frequency band channel selection narrowband high-order filter, a design method and an electronic device, wherein the WLAN frequency band channel selection narrowband high-order filter comprises: an input port, an output port and a resonator composed of more than five microstrip lines;

[0007] The head end microstrip line of the resonator is connected to the input port, each section of the microstrip line in the resonator is connected in series in sequence, and the end microstrip line of the resonator is connected to the output port;

[0008] The resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port;

[0009] The out-of-band suppression process is used to suppress out-of-band frequency band signals outside the preset working frequency band of the original signal to obtain a filtered signal whose out-of-band suppression exceeds a preset attenuation threshold.

[0010] Optionally, each of the microstrip lines in the resonator adopts a U-shaped comb structure, the length of each of the microstrip lines is set according to the wavelength, and the spacing between adjacent microstrip lines is set according to the coupling coefficient.

[0011] Optionally, the resonator adopts a symmetrical structure, and the spacing between adjacent microstrip lines is adjusted so as to gradually widen from both sides close to the input port and the output port to the middle.

[0012] Optionally, each of the microstrip lines in the resonator comprises: each of the microstrip lines is connected through an equivalent transmission line to form an equivalent circuit;

[0013] The equivalent circuit includes: a capacitor, a resistor and an inductor which are arranged in parallel.

[0014] Optionally, the input port includes: an input feed line and an input coupling line;

[0015] The output port includes: an output feed line and an output coupling line;

[0016] The input feed line is used to receive an original signal and transmit the original signal to the resonator through the input coupling line;

[0017] The resonator is also used to transmit the filtered signal to the output feeder through the output coupling line so as to output it to the subsequent circuit.

[0018] Optionally, the WLAN frequency band channel selection narrowband high-order filtering further includes: an input tuning metal sheet and an output tuning metal sheet;

[0019] The input tuning metal sheet is arranged at one side of the input coupling line, the output tuning metal sheet is arranged at one side of the output coupling line, and the input tuning metal sheet and the output tuning metal sheet are arranged at diagonal positions of the resonator respectively;

[0020] The input tuning metal sheet and the output tuning metal sheet are used to adjust the filter performance index by bonding and tearing.

[0021] In addition, to achieve the above purpose, the present invention also proposes a filter design method, which is applied to the production of the above WLAN frequency band channel selection narrowband high-order filter, and the method comprises the following steps:

[0022] Setting the number of microstrip lines in the resonator according to a preset attenuation threshold of the filter;

[0023] The transmission parameters of the filter are used to obtain the length and spacing of each microstrip line in the resonator;

[0024] Obtain the structural parameters of the input port and the output port according to the standard impedance parameter conditions;

[0025] The structural parameters of the input port and the output port, the number of microstrip lines, the length of the microstrip lines and the spacing are used to produce a WLAN frequency band channel selection narrowband high-order filter.

[0026] Optionally, the step of obtaining the length and spacing of each microstrip line in the resonator using the transmission parameters of the filter includes:

[0027] Obtaining a first coupling coefficient of adjacent microstrip lines using an upper limit frequency and a lower limit frequency in the transmission parameters of the filter;

[0028] Obtaining a second coupling coefficient of a non-adjacent microstrip line according to a coupling curve of the microstrip line;

[0029] The length and spacing of each microstrip line in the resonator are obtained according to the first coupling coefficient and the second coupling coefficient.

[0030] Optionally, the step of acquiring structural parameters of the input port and the output port according to the standard impedance parameter condition includes:

[0031] Obtaining the width of the input feeder in the input port and the width of the output feeder in the output port according to the standard impedance parameter condition;

[0032] The horizontal positions of the input feeder and the output feeder satisfying a preset standing wave ratio are obtained according to the obtained width of the input feeder and the obtained width of the output feeder.

[0033] In addition, to achieve the above object, the present invention also provides an electronic device, comprising the WLAN frequency band channel selection narrowband high-order filter as described above.

[0034] The present invention provides a WLAN frequency band channel selection narrowband high-order filter, design method and electronic device, the filter comprises: an input port, an output port and a resonator composed of more than five sections of microstrip lines; the head end microstrip line of the resonator is connected to the input port, each section of the microstrip line in the resonator is connected in series in sequence, and the end microstrip line of the resonator is connected to the output port; the resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port; the out-of-band frequency band signal outside the preset working frequency band of the original signal is suppressed by the out-of-band suppression processing to obtain a filtered signal with out-of-band suppression exceeding a preset attenuation threshold. Rapid attenuation of out-of-band signals is achieved, the proportion of out-of-band signals entering the receiving device is reduced, the demodulation capability of the receiving device for useful signals is improved, and the system capacity and communication rate of the communication system are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0036] Figure 1 A schematic diagram of the structure of a first embodiment of a narrowband high-order filter for selecting a WLAN frequency band channel according to the present invention;

[0037] Figure 2 A schematic diagram of the structure of a second embodiment of a narrowband high-order filter for selecting a WLAN frequency band channel according to the present invention;

[0038] Figure 3 A waveform diagram of return loss in the second embodiment of the narrowband high-order filter for selecting a WLAN frequency band channel of the present invention;

[0039] Figure 4 A waveform diagram of the insertion loss of the second embodiment of the narrowband high-order filter for selecting a WLAN frequency band channel of the present invention;

[0040] Figure 5 A waveform diagram of the standing wave ratio in the second embodiment of the narrowband high-order filter for selecting a WLAN frequency band channel of the present invention;

[0041] Figure 6 An equivalent circuit diagram of a second embodiment of a narrowband high-order filter for selecting a WLAN frequency band channel according to the present invention;

[0042] Figure 7 A frequency allocation diagram for each WLAN frequency band in the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention;

[0043] Figure 8 The figure is a flow chart of an embodiment of a filter design method proposed by the present invention.

[0044] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0045] 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.

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0048] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0049] Reference Figure 1 , Figure 1 The schematic diagram of the structure of the first embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention is as follows: Figure 1 As shown, in this embodiment, the WLAN frequency band channel selection narrowband high-order filter includes: an input port 10, an output port 30, and a resonator 20 composed of more than five microstrip lines. The head end microstrip line of the resonator is connected to the input port, the microstrip lines in the resonator are connected in series in sequence, and the end microstrip line of the resonator is connected to the output port.

[0050] It should be noted that the resonator 20 can be used to perform out-of-band suppression processing on the original signal received at the input port to generate a filtered signal, and output the filtered signal through the output port; wherein the out-of-band suppression processing can be used to suppress the out-of-band frequency band signal outside the preset working frequency band of the original signal, and obtain a filtered signal with out-of-band suppression exceeding a preset attenuation threshold.

[0051] It should be understood that the original signal can be an external electromagnetic wave signal received by the input port through a signal acquisition device such as an antenna, and the original signal can be limited in frequency range according to the selection of the signal acquisition device. The resonator can be an electronic component that performs a frequency control function, which can allow signals of a preset working frequency band to pass through while blocking other frequency signals, thereby achieving the function of frequency selection. When the signal frequency is consistent with the natural frequency of the resonator, the impedance of the resonator to the signal is small, and when the signal frequency is far away from the natural resonant frequency, the impedance of the resonator to the signal is large.

[0052] It should be noted that there are 13 channels in the WLAN frequency band, among which some non-overlapping channels can work simultaneously (for example, channels 1, 6, and 11), but the spacing between the channels is narrow, such as the frequency spacing between channels 1 and 6 is only 2MHz. Therefore, when the three channels work simultaneously, ordinary filters are used for filtering, and the design is basically controlled within the 5th order. According to the normalized filter design theory, due to the limitation of poor out-of-band suppression, the out-of-band attenuation is usually only about 3dB / MHz, and the interference between the channels is extremely large. Out-of-band suppression can be the attenuation capability of signals outside the preset working frequency band, and the preset attenuation threshold can be a pre-set attenuation that satisfies the WLAN frequency band and will not be affected by out-of-band interference signals, for example, it can be set to 35dB / MHz. By setting a high-order resonator composed of multiple microstrip lines (the number of microstrip lines is the same as the order of the resonator), the low-pass prototype is used as a high-order Chebyshev function to achieve the out-of-band attenuation steepness, and its Chebyshev polynomial is:

[0053]

[0054] Where n is the order of the resonator, T n (x) is the attenuation steepness of the high-order resonator. Then the out-of-band attenuation can be calculated as:

[0055]

[0056] Among them, L dB is the out-of-band attenuation, ε is the fluctuation coefficient that determines the fluctuation size in the passband, which is a constant less than 1 and can be set according to the actual needs of the filter, ω i ' is the center frequency of the i-th passband. For signals at different angular frequencies ω', there is a relationship:

[0057] , when ω'≤ω i 'hour;

[0058] , when ω'≥ω i 'hour;

[0059] Among them, as n increases, the steepness of the out-of-band attenuation calculated according to the formula becomes greater, and the corresponding filter selectivity becomes better, so n=16 can be selected to achieve a filter with an out-of-band attenuation greater than or equal to 35dB / MHz, achieving a better suppression effect on out-of-band interference signals. And according to the selected Chebyshev multi-project low-pass prototype, the resonator is constructed using a microstrip line.

[0060] In this embodiment, the WLAN frequency band channel selection narrowband high-order filter includes an input port, an output port and a resonator composed of more than five microstrip lines; the head end microstrip line of the resonator is connected to the input port, the microstrip lines in the resonator are connected in series in sequence, and the end microstrip line of the resonator is connected to the output port; the resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port; the out-of-band frequency band signal outside the preset working frequency band of the original signal is suppressed by the out-of-band suppression processing to obtain a filtered signal with out-of-band suppression exceeding a preset attenuation threshold. Rapid attenuation of out-of-band signals is achieved, the proportion of out-of-band signals entering the receiving device is reduced, the demodulation capability of the receiving device for useful signals is improved, and the system capacity and communication rate of the communication system are improved.

[0061] Reference Figure 2 , Figure 2 The schematic diagram of the structure of the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention is as follows: Figure 2As shown, in this embodiment, the same or similar contents as those in the first embodiment can be referred to the above description, and will not be described in detail later. The WLAN frequency band channel selection narrowband high-order filter includes: an input feeder line 101, an output feeder line 102, an input coupling line 103, an output coupling line 104, a first microstrip line 105, a second microstrip line 106, a third microstrip line 107, a fourth microstrip line 108, a fifth microstrip line 109, a sixth microstrip line 110, a seventh microstrip line 111, an eighth microstrip line 112, a ninth microstrip line 113, a tenth microstrip line 114, an eleventh microstrip line 115, a twelfth microstrip line 116, a thirteenth microstrip line 117, a fourteenth microstrip line 118, a fifth microstrip line 119, a sixth microstrip line 120, a seventh microstrip line 121, a eighth microstrip line 122, a ninth microstrip line 123, a tenth microstrip line 124, a eleventh microstrip line 125, a twelfth microstrip line 126, a thirteenth microstrip line 127, a fourteenth microstrip line 128, a fifth microstrip line 129, a sixth microstrip line 130, a seventh microstrip line 131, a eighth microstrip line 132, a ninth microstrip line 133, a tenth microstrip line 134, a eleventh microstrip line 135, a twelfth microstrip line 136, a thirteenth microstrip line 137, a Line 118, the fifteenth microstrip line 119, the sixteenth microstrip line 120, the first coupling spacing 121, the second coupling spacing 122, the third coupling spacing 123, the fourth coupling spacing 124, the fifth coupling spacing 125, the sixth coupling spacing 126, the seventh coupling spacing 127, the eighth coupling spacing 128, the ninth coupling spacing 129, the tenth coupling spacing 130, the eleventh coupling spacing 131, the twelfth coupling spacing 132, the thirteenth coupling spacing 133, the fourteenth coupling spacing 134, and the fifteenth coupling spacing 135.

[0062] Wherein, the input port includes: an input feeder line and an input coupling line; the output port includes: an output feeder line and an output coupling line.

[0063] It should be noted that the input feeder can be used to receive the original signal and transmit the original signal to the resonator through the input coupling line; the resonator can also be used to transmit the filtered signal to the output feeder through the output coupling line to output it to the subsequent circuit.

[0064] Wherein, each of the microstrip lines in the resonator adopts a U-shaped comb structure, the length of each microstrip line is set according to the wavelength, and the spacing between adjacent microstrip lines is set according to the coupling coefficient.

[0065] It should be noted that the length (L) of each section of the comb line is approximately half of the signal wavelength (λ), which can be adjusted according to the resonance coefficient between the two sections of the microstrip line. For example, the g of the parameters of each circuit element of the low-pass prototype can be obtained by solving the high-order Chebyshev polynomial. i The coupling coefficient of two adjacent microstrip lines is calculated by the value. The calculation formula of the coupling coefficient is:

[0066]

[0067] Among them, M i,i+1 is the coupling coefficient between adjacent microstrip lines, FBW represents the relative bandwidth of the filter of the present invention, and f H and f L Respectively represent the lower and upper frequency limits of the filter.

[0068] In a possible implementation, the coupling coefficient m between the input port and the first microstrip line is S,1 =0.979735068, coupling coefficient from the first microstrip line to the sixteenth microstrip line: m 1,2 =0.8034448557, m 2,3 =0.576403425, m 3,4 =0.536313029, m 4,5 =0.5224447509, m 5,6 =0.5162437212, m 6,7 =0.5131614953, m 7,8 =0.5116806384, m 8,9 =0.511236689,m 9,10 =0.5116806384, m 10,11 =0.5131614952, m 11,12 =0.5162437212, m 12,13 =0.5224447508, m 13,14 =0.5363130289, m 14,15 =0.5764034249, m 15,16 =0.803444856, coupling coefficient between the sixteenth microstrip line and the output port: m 16,L =0.9797350684.

[0069] Furthermore, M represents the coupling coefficient between non-adjacent microstrip lines, and the calculation formula of the coupling coefficient is:

[0070]

[0071] Wherein, f1 and f2 are the frequencies of two resonance peaks in the coupling curve between two non-adjacent microstrip lines.

[0072] It should be understood that the resonator adopts a symmetrical structure, and the spacing between adjacent microstrip lines is adjusted in a manner that it widens from the two sides close to the input port and the output port to the middle. Since there are multiple microstrip lines, their coupling coefficients may affect each other, and the width of the input and output feeder lines is determined according to the condition of the 50Ω standard impedance parameter. Therefore, it is necessary to comprehensively simulate and calculate the final spacing of the strips. At the same time, the width of the input and output feeder lines is determined according to the condition of the 50Ω standard impedance parameter. In actual design, the width of the input and output feeder lines can be determined by ADS electromagnetic simulation software. The position of the input feeder and the output feeder directly affects the external Q value of the filter. The electromagnetic field simulation software SONNET or HFSS is used for multiple simulations, and multiple simulations and calculations are used to obtain the optimal input and output feeder positions.

[0073] Furthermore, the WLAN frequency band channel selection narrowband high-order filter also includes: an input tuning metal sheet 136 and an output tuning metal sheet 137; the input tuning metal sheet is arranged on one side of the input coupling line, the output tuning metal sheet is arranged on one side of the output coupling line, and the input tuning metal sheet and the output tuning metal sheet are respectively arranged at diagonal positions of the resonator; the input tuning metal sheet and the output tuning metal sheet are used to adjust the filter performance indicators by bonding and tearing.

[0074] It should be noted that in the process of manufacturing the WLAN frequency band channel selection narrowband high-order filter, considering that the influencing factors such as processing technology may affect the performance of the WLAN frequency band channel selection narrowband high-order filter, the method of appropriate tuning after processing is adopted, and the manufactured WLAN frequency band channel selection narrowband high-order filter can also be adjusted to a certain extent, so that the performance index of the WLAN frequency band channel selection narrowband high-order filter can fully meet the design requirements, and can be further optimized to a certain extent. A tunable metal sheet is arranged near the input port and the output port, which has the characteristics of being bondable and tearable, and the filter parameters can be fine-tuned by bonding and tearing the metal sheet. When the filter is manufactured, if the parameters are not enough to meet the indicators after testing, the filter indicators can be fine-tuned by bonding or tearing the tuning metal sheet, ensuring that the performance indicators can still be fine-tuned within a certain range when the filter has been manufactured, solving the influence of the processing error on the filter performance indicators, improving the qualified rate of the finished product, and greatly reducing the cost of product manufacturing.

[0075] Reference Figure 3 , Figure 3This is a waveform diagram of the return loss in the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention. The simulation software can be used to obtain the in-band return loss of the constructed WLAN frequency band channel selection narrowband high-order filter, wherein the return loss is a method of expressing the reflection coefficient in logarithmic form (dB). In the figure, the horizontal axis (Frequency) is the frequency, the unit is MHz; the vertical axis (Magnitude) is the logarithmic series. The return loss is the number of dB that the reflected signal is lower than the incident signal. The return loss is always a positive number, between infinity (using characteristic impedance load termination) and 0dB (open circuit or short circuit termination). As Figure 3 As shown, the in-band return loss of the filter in this embodiment is >17.65dB, which is higher than the same type of WLAN frequency band filter (generally, the in-band return loss is >15dB).

[0076] Reference Figure 4 , Figure 4 This is a waveform diagram of the insertion loss in the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention. Similar to the above return loss, the in-band insertion loss of the constructed WLAN frequency band channel selection narrowband high-order filter can be obtained using simulation software, where the insertion loss is the power loss between the filter input port and the output port, and the unit is dB. Figure 4 As shown, the in-band insertion loss of the filter in this embodiment is <0.64dB, which is better than the same type of WLAN frequency band filter (generally the in-band insertion loss is 1.5dB).

[0077] Reference Figure 5 , Figure 5 This is a waveform diagram of the standing wave ratio of the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention. Similar to the above return loss, the standing wave ratio of the constructed WLAN frequency band channel selection narrowband high-order filter can be obtained using simulation software, where the standing wave ratio (Voltage Standing Wave Ratio, VSWR) is the ratio of the antinode voltage to the trough voltage amplitude of the transmission signal. Figure 5 As shown, the VSWR of the filter in this embodiment is less than 1.283, which is better than the same type of WLAN frequency band filter (generally the VSWR is 1.5).

[0078] Furthermore, each of the microstrip lines is connected via an equivalent transmission line to form an equivalent circuit; the equivalent circuit includes: a capacitor C, a resistor R, and an inductor L arranged in parallel, and each of the microstrip lines is connected via an equivalent transmission line TL. Figure 6 , Figure 6The equivalent circuit diagram of the second embodiment of the WLAN frequency band channel selection narrowband high-order filter of the present invention. According to the above-selected Chebyshev multi-project low-pass prototype, it is converted into a corresponding bandpass filter, and the corresponding distributed parameter value is realized using a microstrip circuit to achieve the performance index of the filter. The above-mentioned theoretical value of the coupling coefficient can be simulated by the simulation software ADS, and a resonator that is easy to process, has a high unloaded Q value (with extremely low insertion loss), and is weakly coupled is selected. The electromagnetic simulation software is used for comprehensive simulation to obtain the final optimized simulation result, and the actual plate making test is carried out. After the size is modified, the test verification is continued to obtain the final filter.

[0079] Reference Figure 7 , Figure 7 The frequency allocation diagram of each WLAN frequency band in the second embodiment of the present invention for selecting a narrowband high-order filter for the WLAN frequency band channel. In order to ensure that the 1, 6, and 11 channels (with a frequency interval of only 2MHz) that can work simultaneously do not interfere with each other, the out-of-band attenuation of the 1 channel implemented in this embodiment is ≧35dB / MHz, thereby achieving rapid attenuation of the out-of-band signal.

[0080] In this embodiment, each of the microstrip lines in the resonator adopts a U-shaped comb structure, the length of each microstrip line is set according to the wavelength, and the spacing between adjacent microstrip lines is set according to the coupling coefficient. The resonator adopts a symmetrical structure, and the spacing between adjacent microstrip lines is adjusted in a manner that it widens from the two sides close to the input port and the output port to the middle. Each of the microstrip lines is connected by an equivalent transmission line to form an equivalent circuit; the equivalent circuit includes: a capacitor, a resistor and an inductor arranged in parallel. In the communication frequency band, the insertion loss is low, the standing wave ratio is low, and the out-of-band suppression is strong, reaching 35dB / MHz, which can improve the noise coefficient of the receiver, the sensitivity of the receiver, the anti-interference ability of the communication system, the communication quality of the WLAN system, and the experience of WLAN users of the WLAN system.

[0081] In addition, the present invention also proposes a filter design method. Figure 8 , Figure 8 The figure is a flow chart of an embodiment of a filter design method proposed by the present invention.

[0082] In this embodiment, the filter design method includes the following steps:

[0083] Step S01: setting the number of microstrip lines in the resonator according to a preset attenuation threshold of the filter.

[0084] It should be noted that the preset attenuation threshold can be a pre-set attenuation that satisfies the WLAN frequency band and is not affected by out-of-band interference signals, for example, it can be set to 35 dB / MHz. By setting a high-order resonator composed of multiple microstrip lines (the number of microstrip lines is the same as the order of the resonator), the low-pass prototype is used as a high-order Chebyshev function to achieve the out-of-band attenuation steepness, and the out-of-band suppression level, order, and overall structure of the filter are determined through theoretical calculations. By solving high-order Chebyshev polynomials, the parameters of each circuit element of the low-pass prototype are obtained.

[0085] Step S02: using the transmission parameters of the filter to obtain the length and spacing of each microstrip line in the resonator.

[0086] It should be noted that the length of each microstrip line is set according to the wavelength, and the spacing between adjacent microstrip lines is set according to the coupling coefficient. The spacing between adjacent microstrip lines is adjusted in a manner that it becomes wider from the two sides close to the input port and the output port to the middle. The first coupling coefficient of adjacent microstrip lines can be obtained using the upper limit frequency and the lower limit frequency in the transmission parameters of the filter; the second coupling coefficient of non-adjacent microstrip lines can be obtained according to the coupling curve of the microstrip lines; and the length and spacing of each microstrip line in the resonator can be obtained according to the first coupling coefficient and the second coupling coefficient.

[0087] It should be understood that since there are multiple microstrip lines in the filter, their coupling coefficients may affect each other, and the width of the input and output feed lines is determined according to the condition of the 50Ω standard impedance parameter. Therefore, comprehensive simulation is required to calculate the final spacing of the strips.

[0088] Step S03: Acquire structural parameters of the input port and the output port according to standard impedance parameter conditions.

[0089] It should be noted that the width of the input feeder in the input port and the width of the output feeder in the output port can be obtained according to the standard impedance parameter conditions; the horizontal positions of the input feeder and the output feeder that meet the preset standing wave ratio are obtained according to the obtained width of the input feeder and the width of the output feeder.

[0090] It should be understood that the width of the input and output feeder is determined according to the condition of the 50Ω standard impedance parameter. In actual design, the width of the input and output feeder can be determined by using ADS electromagnetic simulation software. The position of the input and output feeder directly affects the external Q value of the filter. Multiple simulations and multiple simulations are performed using electromagnetic field simulation software SONNET or HFSS to obtain the optimal input and output feeder position.

[0091] Step S04: using the structural parameters of the input port and the output port, the number of microstrip lines, the length of the microstrip lines and the spacing between the microstrip lines to produce a WLAN frequency band channel selection narrowband high-order filter.

[0092] It should be noted that the structural parameters of the above input and output ports, the number of microstrip lines, the length of the microstrip lines, and the theoretical values ​​of the spacing can be simulated through the RF simulation software ADS to obtain preliminary simulation results, and the preliminary simulation results are fine-tuned and optimized to make the simulation results far better than the expected indicators. Then, a resonator that is easy to process, has a high unloaded Q value (with extremely low insertion loss), and is weakly coupled is selected, and a comprehensive simulation is performed using electromagnetic simulation software to obtain the final optimized simulation results, actual plate making tests, and after modifying the size, continued testing and verification to obtain the final filter.

[0093] Furthermore, when the filter is manufactured and the tested parameters do not meet the indicators, the filter indicators can be fine-tuned by gluing or tearing off the tuning metal sheet, ensuring that the performance indicators can still be fine-tuned within a certain range after the filter has been manufactured, thus solving the impact of processing errors on the filter performance indicators, improving the qualified rate of finished products, and greatly reducing the cost of product manufacturing.

[0094] In this embodiment, the filter design method includes setting the number of microstrip lines in the resonator according to the preset attenuation threshold of the filter; using the transmission parameters of the filter to obtain the length and spacing of each microstrip line in the resonator; obtaining the structural parameters of the input port and the output port according to the standard impedance parameter conditions; using the structural parameters of the input port and the output port, the number of microstrip lines, the length and spacing of the microstrip lines to make a WLAN frequency band channel selection narrowband high-order filter. After the signal passes through the filter, the useful signal passes almost without attenuation, while the useless signal is greatly attenuated, achieving the suppression of out-of-band interference signals, greatly reducing the out-of-band interference of the receiver system, improving the network capacity of the WLAN system, and improving the network quality of the WLAN system.

[0095] In addition, in order to achieve the above-mentioned purpose, an embodiment of the present invention also proposes an electronic device. Since the electronic device includes the above-mentioned WLAN frequency band channel selection narrowband high-order filter, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0096] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

[0097] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0098] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0099] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A WLAN frequency band channel selection narrowband high-order filter, characterized in that: The WLAN frequency band channel selection narrowband high-order filter comprises: an input port, an output port and a resonator consisting of more than five sections of microstrip lines; The head end microstrip line of the resonator is connected to the input port, each section of the microstrip line in the resonator is connected in series in sequence, and the end microstrip line of the resonator is connected to the output port; The resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port; The out-of-band suppression process is used to suppress out-of-band frequency band signals outside the preset working frequency band of the original signal to obtain a filtered signal whose out-of-band suppression exceeds a preset attenuation threshold; Wherein, each of the microstrip lines in the resonator adopts a U-shaped comb structure, the length of each microstrip line is set according to the wavelength, and the spacing between adjacent microstrip lines is set according to the coupling coefficient; The resonator comprises sixteen sections of the microstrip lines, adopting a symmetrical structure, and the spacing between adjacent microstrip lines gradually widens from the two sides close to the input port and the output port to the middle; The input port includes: an input feed line and an input coupling line; The output port includes: an output feed line and an output coupling line; The WLAN frequency band channel selection narrowband high-order filter also includes: an input tuning metal sheet and an output tuning metal sheet; The input tuning metal sheet is arranged at one side of the input coupling line, the output tuning metal sheet is arranged at one side of the output coupling line, and the input tuning metal sheet and the output tuning metal sheet are arranged at diagonal positions of the resonator respectively; The input tuning metal sheet and the output tuning metal sheet are used to adjust the filter performance index by bonding and tearing.

2. The WLAN frequency band channel selection narrowband high-order filter according to claim 1, characterized in that: Each of the microstrip lines is connected via an equivalent transmission line to form an equivalent circuit; The equivalent circuit includes: a capacitor, a resistor and an inductor which are arranged in parallel.

3. The WLAN frequency band channel selection narrowband high-order filter according to claim 1, characterized in that: The input feed line is used to receive an original signal and transmit the original signal to the resonator through the input coupling line; The resonator is also used to transmit the filtered signal to the output feeder through the output coupling line so as to output it to the subsequent circuit.

4. A filter design method, applied to the manufacture of a WLAN frequency band channel selection narrowband high-order filter as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: Setting the number of microstrip lines in the resonator according to a preset attenuation threshold of the filter; The transmission parameters of the filter are used to obtain the length and spacing of each microstrip line in the resonator; Obtain the structural parameters of the input port and the output port according to the standard impedance parameter conditions; The structural parameters of the input port and the output port, the number of microstrip lines, the length of the microstrip lines and the spacing are used to produce a WLAN frequency band channel selection narrowband high-order filter.

5. The filter design method according to claim 4, characterized in that: The step of using the transmission parameters of the filter to obtain the length and spacing of each microstrip line in the resonator includes: Obtaining a first coupling coefficient of adjacent microstrip lines using an upper limit frequency and a lower limit frequency in the transmission parameters of the filter; Obtaining a second coupling coefficient of a non-adjacent microstrip line according to a coupling curve of the microstrip line; The length and spacing of each microstrip line in the resonator are obtained according to the first coupling coefficient and the second coupling coefficient.

6. The filter design method according to claim 4, characterized in that: The step of obtaining the structural parameters of the input port and the output port according to the standard impedance parameter conditions includes: Obtaining the width of the input feeder in the input port and the width of the output feeder in the output port according to the standard impedance parameter condition; The horizontal positions of the input feeder line and the output feeder line that meet a preset standing wave ratio are obtained according to the obtained width of the input feeder line and the obtained width of the output feeder line.

7. An electronic device, characterized in that: The electronic device comprises the WLAN frequency band channel selection narrowband high-order filter according to any one of claims 1 to 3.

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