Passive filter design method for ocean short-wave communication

Abstract

The invention discloses a passive filter design method for ocean short-wave communication, which comprises the following steps of: a, determining design indexes according to communication requirements of the ocean short-wave communication; b, selecting a proper filter type according to the index proposed in the step a, and calculating a corresponding LC device numerical value; c, when the inductor is selected, the principle that the inductance value is not suitable to be too large and the Q value needs to meet specific conditions is followed; d, if the inductance value obtained through calculation in the step b is too large, Norton transformation is carried out on the large inductance value to obtain an inductance nominal value with the Q value meeting the requirement of the step c and the value being small; e, adding or replacing in the filter schematic diagram according to the capacitance value obtained by the Norton transform in the step d; f, importing the device results obtained in the steps d and e into EDA software for simulation, and optimizing the overlarge device numerical value according to the simulation result; g, performing impedance matching on the optimized filter; h, selecting a substrate, and designing a PCB layout according to the optimized filter; and i, processing the designed substrate.

Description

Technical Field

[0001] The invention relates to the technical field of communication and information processing, and in particular to a passive filter design method for ocean shortwave communication. Background Art

[0002] In the process of wireless communication based on shortwave frequency band, due to the mutual interference of signals between multiple frequency bands, the signal quality received at the receiving end is poor and there is a lot of interference. Therefore, a filter is needed to filter out the signal of the target frequency band and suppress the signals of other frequency bands to further improve the quality of the received signal. As an important component of the wireless communication system, the performance of the filter has a direct impact on the performance of the communication system. How to select the target signal from many frequencies without distortion and reduce useless or interfering signals, this demand puts forward higher requirements for the design of the filter.

[0003] In the current era of continuous development and iteration of various electronic circuit technologies, lumped parameter passive filters are usually preferred for use in communication systems due to their low cost and easy processing. Lumped parameter passive filters are mainly composed of a finite number of ideal R, L, and C components, and the transmission characteristics are mainly determined by the lumped parameter component values. Summary of the invention

[0004] Based on this, it is necessary to propose a passive filter design method for marine shortwave communication to address the above problems.

[0005] The embodiment of the present invention provides a passive filter design method for marine shortwave communication, comprising the following steps:

[0006] a. Determine the design indicators according to the communication requirements of marine shortwave communication;

[0007] b. Select the appropriate filter type according to the indicators proposed in step a and calculate the corresponding LC device value;

[0008] c. When selecting an inductor, follow the principle that the inductance value should not be too large and the Q value must meet specific conditions;

[0009] d. If the inductance value calculated in step b is too large, the larger inductance is subjected to a Norton transform to obtain a smaller nominal inductance value whose Q value meets the requirements of step c;

[0010] e. Add or replace the capacitance value obtained by the Norton transform in step d in the filter schematic;

[0011] f. Import the device results obtained in steps d and e into the EDA software for simulation, and optimize the excessive device values ​​according to the simulation results;

[0012] g. Impedance matching of the optimized filter;

[0013] h. Select a suitable substrate and design the PCB layout based on the optimized filter;

[0014] i. Process the substrate designed in step h to complete the production of the passive filter.

[0015] In the above scheme, the LC filter component value calculation method in step b uses EDA software to directly calculate parameters according to target values, and allows one or more component values ​​to be appropriately changed according to actual conditions to observe whether the target result is met.

[0016] In the above scheme, the Q value in step c is calculated according to the formula Q min (BP) = Q min (LP)×Q BP Determine, where Q min (BP) represents the minimum inductance value, Q min (LP) represents the minimum Q value of the low-pass prototype, and Q BP satisfy: Where F0 is the center frequency and BW is the passband bandwidth.

[0017] In the above scheme, the Norton transformation in step d includes: using the Norton transformation to change the larger inductance value, reducing the influence of the parasitic parameters of the substrate itself on the actual inductance value, and using the following calculation formula: Among them, C1, C2, and C3 are the capacitance values ​​added after the Norton transformation, and C is the capacitance value that resonates with the original inductance.

[0018] The embodiment of the present invention further provides a marine shortwave communication receiver designed by the passive filter design method for marine shortwave communication as described above, the marine shortwave communication receiver comprising:

[0019] Yag i antenna module, used to receive and amplify signals in the 19MHz frequency band, with an amplification factor of about 15-20dB;

[0020] The passive bandpass filter module is connected to the Yagi antenna module and is used to perform the first limiting filter on the received signal. The filter frequency band is 19MHz and the bandwidth is 2MHz.

[0021] The low noise amplifier (LNA) module is connected to the passive bandpass filter module to further amplify the signal and reduce the system noise, with an amplification factor of about 20-30dB;

[0022] Automatic gain control (AGC) module, connected to the LNA module, is used to adjust the signal amplification factor. The operating frequency range supports the shortwave frequency band and the control gain range is 0-30dB;

[0023] Active bandpass filter and amplifier (OPA) module, connected to the AGC module, is used to selectively amplify the target signal with an amplification factor of about 40-50dB;

[0024] The analog-to-digital converter (ADC) module is connected to the OPA module and is used to receive and convert the amplified signal. The receiving sensitivity range is about 0-7dB.

[0025] The embodiments of the present invention have the following beneficial effects:

[0026] The present invention is designed based on the whole design process of lumped parameter bandpass filter, integrates the existing technology into the shortwave frequency band filter design, and is used to construct the marine shortwave communication system, which can better improve the performance of the South China Sea shortwave communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 these drawings without paying creative work.

[0028] in:

[0029] Figure 1 The present invention provides a flow chart of a passive filter design method for marine shortwave communication;

[0030] Figure 2 is the original image result of parameter calculation performed by the EDA software in the embodiment of the present invention;

[0031] Figure 3 is a circuit schematic diagram and related parameters after Norton transformation in an embodiment of the present invention;

[0032] Figure 4 It is a circuit diagram in which the theoretical value of the inductance in the schematic diagram is replaced with the nominal value of the inductance provided by the device manufacturer in an embodiment of the present invention;

[0033] Figure 5 A circuit diagram in which the theoretical value of capacitance in the schematic diagram is replaced with the nominal value capacitance provided by the device manufacturer in an embodiment of the present invention;

[0034] Figure 6 It is a circuit diagram after impedance matching is performed on the schematic diagram and nominal value devices are replaced in an embodiment of the present invention;

[0035] 7 is a simulation result of the S parameters, output and input impedance of the bandpass filter in an embodiment of the present invention;

[0036] Figure 8 is a layout generated in an embodiment of the present invention;

[0037] Fig. 9 It is a principle block diagram of the marine shortwave communication receiver in the present invention. DETAILED DESCRIPTION

[0038] 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.

[0039] The embodiment of the present invention provides a passive filter design method for marine shortwave communication, comprising the following steps:

[0040] Step 1: Determine the design indicators according to communication requirements;

[0041] Specifically, the center frequency F0=19MHz, the passband bandwidth BW=2MHz, the attenuation at the bandwidth of 18MHz-20MHz is <=3dB; the attenuation at the stopband of 14MHz-25MHz is >=20dB, and the input and output impedances are both 50Ω.

[0042] Figure 2 The filter parameters calculated by the software Filtersolution mainly illustrate the specific structure and device parameters of the third-order Butterworth bandpass filter.

[0043] Step 2: Select the appropriate filter type according to the indicators proposed in step 1, and calculate the corresponding LC component value;

[0044] Specifically, the target parameters of step 1 are input into the EDA software, the Butterworth type is selected as the transfer function, and the π type is selected as the circuit structure, and the required order and circuit parameters can be calculated, that is, the Butterworth bandpass filter circuit diagram of the order 2 is obtained.

[0045] First, it should be noted that this order is the minimum ideal order, and the stopband attenuation may not reach the target. Therefore, the order is increased to 3rd order in the present invention to meet the stopband attenuation requirement.

[0046] Secondly, due to the influence of the Q value, the final passband attenuation result will differ from the theoretical attenuation result by 1 dB. Therefore, the passband attenuation calculation of the present invention uses a value of 1 dB.

[0047] Step 3: The inductor selection principle should not be too large, and the Q value needs to meet specific conditions;

[0048] Specifically, due to the substrate material itself, parasitic parameters are affected, causing deviations in device values. In order to reduce this effect, the selected inductor should not be too large.

[0049] The required Q value of the inductor can be calculated according to the formula:

[0050] Q min (BP) = Q min (LP)×Q BP (1)

[0051] Among them, Q min (BP) is the minimum Q value required for the low-pass prototype filter, Q min (LP) represents the minimum Q value of the low-pass prototype, and Q BP satisfy:

[0052]

[0053] Among them, F0 is the center frequency and BW is the passband bandwidth.

[0054] Step 4: According to the result of step 2, since an overly large inductance will produce large parasitic parameters, which will cause the final result to deviate from the theoretical value, the larger inductance is Norton transformed to a nominal inductance value whose Q value satisfies the result of step 3 and has a smaller value;

[0055] Specifically, the capacitance value obtained by the Norton transformation in step 4 is added or replaced in the schematic diagram;

[0056] There are two main types of Norton transformation. The present invention mainly uses Norton transformation type I, and the capacitance transformation satisfies the following formula:

[0057]

[0058] Capacitor 1:

[0059]

[0060] Capacitor 2:

[0061]

[0062] Capacitor 3:

[0063]

[0064] Where C is the capacitance value that resonates with the original inductance.

[0065] Step 5, adding or replacing the capacitance value obtained by the Norton transformation in step 4 in the schematic diagram;

[0066] in, Figure 3 In order to utilize the results after Norton transformation, the theoretical values ​​of the device after Norton transformation are specifically explained.

[0067] Step 6: According to the device results obtained in Step 4 and Step 5, the device package provided by the manufacturer is imported into the EDA software, and simulation is performed in the EDA software. For device values ​​that are too large, the methods of Step 4 and Step 5 are referred to for optimization, and the final optimized results are simulated in the EDA software;

[0068] Step 7: Perform impedance matching;

[0069] Using the impedance matching calculator provided by the EDA software, the input and output impedances can be obtained by simulation according to step 6. By combining the frequency band, impedance size and matching network type, an impedance matching network can be obtained, and devices can be selected for the network according to the principles of step 3.

[0070] Figure 7(a) shows the S parameter result, i.e. the attenuation result of transmission from the input end to the output end. If the result is greater than -3dB within the target frequency band, it means that the target result has been achieved. Figure 7(b)(c) shows the impedance of the two ports. The port impedance is close to 50 ohms, which means that the result can be directly used in the RF circuit to ensure that the transmission result will not be attenuated due to impedance mismatch during access.

[0071] Step 8. Select a suitable substrate to design the PCB layout;

[0072] like Figure 8 As shown, the present invention will perform layout design based on Rogers R4350B type board, the substrate thickness is 0.508mm, the dielectric constant is 3.66, and the number of PCB layers is two.

[0073] Step 9: Process the substrate in step 8.

[0074] The shortwave frequency band filter designed through the above steps is used in marine shortwave communication receivers.

[0075] like Fig. 9 As shown, the marine shortwave communication receiver comprises:

[0076] Yag i antenna module, used to receive and amplify signals in the 19MHz band, with an amplification factor of about 15-20dB;

[0077] The passive bandpass filter module is connected to the Yag i antenna module and is used to perform the first limiting filter on the received signal. The filter frequency band is 19 MHz and the bandwidth is 2 MHz.

[0078] The low noise amplifier (LNA) module is connected to the passive bandpass filter module to further amplify the signal and reduce the system noise, with an amplification factor of about 20-30dB;

[0079] Automatic gain control (AGC) module, connected to the LNA module, is used to adjust the signal amplification factor. The operating frequency range supports the shortwave frequency band and the control gain range is 0-30dB;

[0080] Active bandpass filter and amplifier (OPA) module, connected to the AGC module, is used to selectively amplify the target signal with an amplification factor of about 40-50dB;

[0081] The analog-to-digital converter (ADC) module is connected to the OPA module and is used to receive and convert the amplified signal. The receiving sensitivity range is about 0-7dB.

[0082] The marine shortwave communication receiver is connected in sequence through a Yagi antenna module, a passive bandpass filter module, an LNA module, an AGC module, an OPA module and an ADC module, which together constitute a signal processing link of the receiver, realize signal reception, filtering, amplification, regulation and conversion, and is used for signal transmission in a 19MHz frequency band in long-distance marine communication. The wavelength of this frequency band is about 15 meters, and the longest communication distance can reach 2,000 kilometers, which is approximately equal to 130,000 wavelengths.

[0083] When the maximum attenuation multiple (considering MIMO and the worst weather condition of high humidity) is about 1.7x10^10, i.e. about 103dB attenuation, and the ionospheric escape is about 10dB, the receiver can ultimately withstand a total attenuation of about 113dB through its overall architectural design.

[0084] Furthermore, the marine shortwave communication receiver also includes auxiliary modules, such as a power management module, a signal processing module, etc., to support the normal operation and signal processing functions of the receiver.

[0085] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A passive filter design method for marine shortwave communication, characterized in that: The following steps are involved: a. Determine the design indicators according to the communication requirements of marine shortwave communication; b. Select the appropriate filter type according to the indicators proposed in step a and calculate the corresponding LC device value; c. When selecting an inductor, follow the principle that the inductance value should not be too large and the Q value must meet specific conditions; d. If the inductance value calculated in step b is too large, the larger inductance is subjected to a Norton transform to obtain a smaller nominal inductance value whose Q value meets the requirements of step c; e. Add or replace the capacitance value obtained by the Norton transform in step d in the filter schematic; f. Import the device results obtained in steps d and e into the EDA software for simulation, and optimize the excessive device values ​​according to the simulation results; g. Impedance matching of the optimized filter; h. Select a suitable substrate and design the PCB layout based on the optimized filter; i. Process the substrate designed in step h to complete the production of the passive filter.

2. The passive filter design method for ocean shortwave communication according to claim 1, characterized in that: The LC filter component value calculation method in step b uses EDA software to directly calculate parameters according to target values, and allows one or more component values ​​to be appropriately changed according to actual conditions to observe whether the target result is met.

3. The passive filter design method for ocean shortwave communication according to claim 1 or 2, characterized in that: The Q value in step c is calculated according to the formula Q min (BP) = Q min (LP)×Q BP Determine, where Q min (BP) represents the minimum inductance value, Q min (LP) represents the minimum Q value of the low-pass prototype, and Q BP satisfy: Where F0 is the center frequency and BW is the passband bandwidth.

4. The passive filter design method for ocean shortwave communication according to claim 3 is characterized in that: The Norton transformation in step d includes: using the Norton transformation to change the larger inductance value, reducing the influence of the parasitic parameters of the substrate itself on the actual inductance value, and using the following calculation formula: Among them, C1, C2, and C3 are the capacitance values ​​added after the Norton transformation, and C is the capacitance value that resonates with the original inductance.

5. A marine shortwave communication receiver designed according to the passive filter design method for marine shortwave communication as claimed in any one of claims 1 to 4, characterized in that: The marine shortwave communication receiver comprises: Yagi antenna module, used to receive and amplify signals in the 19MHz band, with an amplification factor of about 15-20dB; The passive bandpass filter module is connected to the Yagi antenna module and is used to perform the first limiting filter on the received signal. The filter frequency band is 19MHz and the bandwidth is 2MHz. The low noise amplifier (LNA) module is connected to the passive bandpass filter module to further amplify the signal and reduce the system noise, with an amplification factor of about 20-30dB; Automatic gain control (AGC) module, connected to the LNA module, is used to adjust the signal amplification factor. The operating frequency range supports the shortwave frequency band and the control gain range is 0-30dB; Active bandpass filter and amplifier (OPA) module, connected to the AGC module, is used to selectively amplify the target signal with an amplification factor of about 40-50dB; The analog-to-digital converter (ADC) module is connected to the OPA module and is used to receive and convert the amplified signal. The receiving sensitivity range is about 0-7dB.

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