Circuit synthesis method of broadband phase-shifting filter with port non-resonance points
By adding non-resonant points to the input and output ends of the broadband filter, building an admission matrix, and performing parameter solving and port coupling transformation, the problem of performance deterioration in broadband systems is solved, and the effective design of broadband phase shift filter and system miniaturization is realized.
Patent Information
- Application Number
- CN202510523307.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-08-05
AI Technical Summary
The existing phase shift filter comprehensive technology has narrowband approximation problems in broadband systems, resulting in deterioration of performance and is unable to effectively guide the design of broadband phased array systems.
Add non-resonant points to the input and output ends of traditional broadband filters to build an admission matrix of a broadband phase shift filter with phase shift. By solving the parameter values and based on the ABCD matrix equivalent principle, port coupling transformation is realized to obtain circuit parameters that meet the broadband phase shift conditions.
The phase shifting characteristics in the broadband range are realized, out-of-band interference signals are suppressed and phased array antenna beams are controlled, and the RF front-end miniaturization and multifunctional design is supported, avoiding performance deterioration caused by narrowband approximation.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of wireless communication systems, and in particular relates to a circuit synthesis method of a broadband phase-shift filter with a port non-resonance point. Background Art
[0002] Wideband bandpass filters play a key role in suppressing interfering signals in broadband phased array systems. Phase shifters also play an important role in broadband phased array systems, steering the beam of the phased array antenna, thereby improving the performance and efficiency of the communication system. Existing phase-shift filter synthesis technology primarily targets narrowband filters. However, this technology suffers from narrowband approximation when guiding circuit implementation in broadband systems, resulting in a sharp deterioration in performance at locations away from the center frequency.
[0003] To guide the design of broadband phase-shift filters, researchers have proposed a circuit synthesis method for broadband phase-shift filters by adding non-resonant points at their ports. This method, which derives circuit parameter values that meet the requirements for broadband phase-shift filtering, is presented. This method can be effectively applied to the design of phase-shift filters in broadband phased array systems. Summary of the Invention
[0004] The present invention aims to provide a circuit synthesis method for a broadband phase-shift filter with a non-resonant port point, thereby obtaining circuit parameter values that meet broadband phase-shift filtering requirements. This method addresses the technical problem of deteriorating broadband circuit performance due to narrowband approximation in existing multifunctional filter synthesis techniques.
[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:
[0006] A circuit synthesis method for a broadband phase-shift filter with a port non-resonance point, the method comprising the following steps:
[0007] Step S1: Based on the traditional matrix synthesis method, the admittance matrix of the traditional broadband filter is obtained;
[0008] Step S2: adding a non-resonant point at the input and output ends of the traditional broadband filter respectively, adding the non-resonant point term to the admittance matrix of the traditional broadband filter, and constructing the admittance matrix of the broadband phase-shift filter with phase shift;
[0009] Step S3: solving the parameter values that have changed in the admittance matrix of the broadband phase-shift filter relative to the admittance matrix of the traditional broadband filter, and obtaining the admittance matrix of the broadband phase-shift filter with additional phase shift;
[0010] Step S4: Based on the ABCD matrix equivalent principle and the admittance matrix of the broadband phase-shift filter with additional phase shift, the input / output port coupling and the position of the non-resonance point are transformed to obtain the broadband phase-shift filter port coupling that can be realized by the circuit.
[0011] Step S5: Based on the admittance matrix of the broadband phase-shift filter with additional phase shift, the broadband phase-shift filter circuit parameters corresponding to the matrix are synthesized.
[0012] Furthermore, the admittance matrix of the conventional broadband filter in step S1 is expressed as follows:
[0013]
[0014] Where n is the filter order; j represents the imaginary unit; and represents the coupling between the i-th resonator and the k-th resonator, and and represents the coupling between the source and the i-th resonator, and and represents the coupling between the load and the i-th resonator, and represents the coupling between the source and the load, and represents the self-coupling of the i-th resonator and can be expressed as follows:
[0015]
[0016] in and represents the equivalent capacitance and inductance of the i-th resonator in the traditional broadband filter, and ω represents the angular frequency.
[0017] Furthermore, the admittance matrix of the broadband phase-shift filter in step S2 is expressed as follows:
[0018]
[0019] in, represents the self-coupling at the non-resonant point of the input port, represents the self-coupling at the non-resonant point of the output port, represents the coupling between the input port and the first resonator, represents the coupling between the nth resonator and the output port, represents the equivalent capacitance of the first resonator of the broadband phase-shift filter, represents the equivalent inductance of the first resonator of the broadband phase-shift filter, represents the equivalent capacitance of the nth resonator of the broadband phase-shift filter, represents the equivalent inductance of the nth resonator of the broadband phase-shift filter.
[0020] Furthermore, the parameter value in step S3 is calculated as follows:
[0021] and It is calculated as follows:
[0022]
[0023] in, and They represent the additional phase shift introduced at the input / output port of the broadband phase-shift filter;
[0024] Let the phase shift of the output port be And the phase shift of the input port is Then we have:
[0025]
[0026] At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained:
[0027]
[0028] Where ω1 and ω2 are two arbitrary frequency points in the filter passband, is the S-parameter response of the admittance matrix [A0] of the traditional broadband filter, is the S-parameter response of the admittance matrix [A1] of the broadband phase-shifting filter, expressed as:
[0029]
[0030] Wherein, j represents the imaginary unit; The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A0] of the traditional broadband filter is represented by The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A1] of the broadband phase-shifting filter;
[0031]
[0032] represents the phase response of the admittance matrix [A0] of the conventional broadband filter, represents the phase response of the admittance matrix [A1] of the broadband phase-shift filter; imag(·) represents the extraction of the complex imaginary function, and real(·) represents the extraction of the complex real part function;
[0033] Solving equation group (6) by combining formulas (1)-(8) can obtain the three unknown variables corresponding to the input port in the admittance matrix [A1] of the broadband phase-shift filter: and
[0034] Let the phase shift of the input port be And the phase shift of the output port is Then we have:
[0035]
[0036] At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained:
[0037]
[0038] Solve equation (10) by combining formulas (1)-(4) and (7)-(10) to obtain the three unknown variables corresponding to the output port. and
[0039] Furthermore, in step S4, the ABCD matrix corresponding to the input port before the non-resonance point NRN is swapped is:
[0040]
[0041] The corresponding ABCD matrix after the input port and the non-resonant point NRN are exchanged is:
[0042]
[0043] Among them, Y SS It represents the series admittance value after the input port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2
[0044]
[0045] The ABCD matrix corresponding to the output port before exchanging positions with the non-resonant point NRN is:
[0046]
[0047] The corresponding ABCD matrix after the output port and the non-resonant point NRN are exchanged is:
[0048]
[0049] Among them, Y LLIt represents the series admittance value after the output port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2
[0050]
[0051] Furthermore, in step S5, the broadband phase-shift filter circuit parameter non-resonance point NRN is set by a capacitor C SS / C LL Or an inductor L SS / L LL The calculation method is as follows:
[0052]
[0053] Where ω0 represents the center frequency of the filter passband.
[0054] Compared with the prior art, the present invention has the following beneficial technical effects:
[0055] 1) The present invention proposes a broadband phase-shift filter architecture with a port non-resonant point, integrating the filter and phase shifter of a broadband RF front-end into one architecture, providing a feasible implementation plan for miniaturization, integration, and multifunctionality of the RF front-end.
[0056] 2) Based on the broadband phase-shift filter architecture, the present invention proposes a broadband filter synthesis method with arbitrary phase shift, which provides reliable guidance for the design of broadband filter phase shifters and avoids the problem of performance deterioration within the passband caused by narrowband approximation.
[0057] 3) This invention achieves broadband phase-shifting characteristics while maintaining the filtering properties of a broadband filter. In broadband phased array systems, a broadband phase-shifting filter with a non-resonant port suppresses out-of-band interference signals while simultaneously controlling the beam of the phased array antenna. Integrating phase shifter functionality into a broadband filter offers a promising solution for miniaturizing the system and enhancing overall performance, meeting the system's requirements for compact, low-cost, and lightweight design. BRIEF DESCRIPTION OF THE DRAWINGS
[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in describing the embodiments of the present invention. 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 any creative labor.
[0059] Figure 1 The figure is a schematic diagram of the circuit structure of a broadband phase-shift filter with a port non-resonance point according to the present invention.
[0060] Figure 2 It is a schematic diagram of the port and non-resonance point circuit conversion of the present invention.
[0061] Figure 3 FIG. 4 is a schematic diagram of a topological structure of a broadband phase-shift filter according to an embodiment of the present invention.
[0062] Figure 4 FIG. 4 is a circuit diagram of a broadband phase-shift filter according to an embodiment of the present invention.
[0063] Figure 5 FIG. 1 is a schematic diagram of the amplitude response and phase response of a broadband phase-shift filter according to an embodiment of the present invention. DETAILED DESCRIPTION
[0064] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.
[0065] The present invention proposes a circuit synthesis method for a broadband phase-shift filter with a port non-resonance point, the method is based on Figure 1 The broadband phase-shift filter architecture with nonresonant ports is shown. The broadband phase-shift filter (denoted by F_p) consists of a traditional nth-order broadband filter (denoted by F_c) and two nonresonant ports (NRN) at the input and output ports, respectively. By adjusting the admittance of the NRN and the input / output coupling coefficient of the proposed broadband phase-shift filter, arbitrary phase shift can be achieved within the passband of the broadband phase-shift filter F_p.
[0066] The present invention is based on the traditional broadband filter admittance matrix, and adds a non-resonant unit at the input and output ports respectively for phase shifting. The non-resonant unit is represented by two constants in the matrix.
[0067] The circuit synthesis method of the broadband phase-shift filter with a port non-resonance point proposed by the present invention comprises the following steps:
[0068] Step S1: Based on the traditional matrix synthesis method, the admittance matrix [A0] of the traditional broadband filter F_c is obtained. The admittance matrix [A0] is expressed as:
[0069]
[0070] Where n is the filter order; j represents the imaginary unit; and represents the coupling between the i-th resonator and the k-th resonator, and and represents the coupling between the source and the i-th resonator, and and represents the coupling between the load and the i-th resonator, and represents the coupling between the source and the load, and represents the self-coupling of the i-th resonator and can be expressed as follows:
[0071]
[0072] in and represents the equivalent capacitance and inductance of the i-th resonator in the traditional broadband filter, and ω represents the angular frequency.
[0073] Step S2: Add a non-resonant point at the input and output of the traditional broadband filter, and add a non-resonant point item to the admittance matrix of the traditional broadband filter. and Construct the admittance matrix [A1] of the broadband phase-shift filter F_p with phase shift. The admittance matrix [A1] is expressed as:
[0074]
[0075] The admittance matrix [A1] of the broadband phase-shift filter is only slightly smaller than the admittance matrix [A0] of the traditional broadband filter. and Something has changed. represents the self-coupling at the non-resonant point of the input port, represents the self-coupling at the non-resonant point of the output port, represents the coupling between the input port and the first resonator, represents the coupling between the nth resonator and the output port, represents the equivalent capacitance of the first resonator of the broadband phase-shift filter, represents the equivalent inductance of the first resonator of the broadband phase-shift filter, represents the equivalent capacitance of the nth resonator of the broadband phase-shift filter, represents the equivalent inductance of the nth resonator of the broadband phase-shift filter.
[0076] Step S3: solving the parameter values that have changed in the admittance matrix of the broadband phase-shift filter relative to the admittance matrix of the traditional broadband filter, and obtaining the admittance matrix of the broadband phase-shift filter with additional phase shift.
[0077] The additional phase shift introduced at the input / output ports of the broadband phase-shift filter is and Normalize the input / output load impedance to Z0=1, then and It can be calculated as follows:
[0078]
[0079] Phase shift of broadband phase-shift filter and and Independent of each other, the relevant coupling values of the two ports can be solved independently. Let the phase shift of the output port be And the phase shift of the input port is Then we have:
[0080]
[0081] At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained:
[0082]
[0083] Where ω1 and ω2 are two arbitrary frequency points in the filter passband, is the S-parameter response of the admittance matrix [A0] of the traditional broadband filter, is the S-parameter response of the admittance matrix [A1] of the broadband phase-shifting filter, expressed as:
[0084]
[0085] Where j represents the imaginary unit, The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A0] of the traditional broadband filter is represented by The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A1] of the broadband phase-shifting filter;
[0086]
[0087] represents the phase response of the admittance matrix [A0] of the conventional broadband filter, represents the phase response of the admittance matrix [A1] of the broadband phase-shifting filter; imag(·) represents the extraction of the complex imaginary function, and real(·) represents the extraction of the complex real part function.
[0088] Solving equation group (6) by combining formulas (1)-(8) can obtain the three unknown variables corresponding to the input port in the admittance matrix [A1] of the broadband phase-shift filter: and
[0089] For the unknown variables at the output port, similarly, let the phase shift at the input port be And the phase shift of the output port is Then we have:
[0090]
[0091] At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained:
[0092]
[0093] Solve equation (10) by combining formulas (1)-(4) and (7)-(10) to obtain the three unknown variables corresponding to the output port. and Through the above process, all parameter values in the admittance matrix of the broadband phase-shift filter that are different from the admittance matrix of the traditional broadband filter can be obtained.
[0094] At this point, the parameter values of the broadband phase-shift filter admittance matrix that have changed compared to the traditional broadband filter admittance matrix are substituted into the broadband phase-shift filter admittance matrix [A1], and the additional phase-shift filter is obtained. The admittance matrix of the broadband phase-shift filter.
[0095] Step S4: Based on the ABCD matrix equivalent principle and the broadband phase-shift filter admittance matrix with additional phase shift, the positions of the input / output ports and the non-resonance points are transformed to obtain the broadband phase-shift filter port coupling that can be realized by the circuit.
[0096] For the realization of port coupling, an equivalent circuit conversion method based on ABCD matrix transformation is introduced. Figure 2 The following is a schematic diagram of circuit conversion. Figure 1 The positions of the non-resonant point NRN and the input / output port in the architecture are exchanged so that the input / output coupling of the broadband phase-shift filter can be realized with a transmission line. After the circuit transformation, it is only necessary to use the admittance matrix scaling method to convert m s1 and m nL Scaling to 1 allows for direct connection.
[0097] Before the input port and the non-resonant point NRN are exchanged, that is, Figure 2 The ABCD matrix corresponding to (a) in is:
[0098]
[0099] After the input port and the non-resonance point NRN are exchanged, Figure 2 The ABCD matrix corresponding to (b) in is:
[0100]
[0101] Among them, Y SS It represents the series admittance value after the input port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2
[0102]
[0103] The ABCD matrix corresponding to the output port before exchanging positions with the non-resonant point NRN is:
[0104]
[0105] The corresponding ABCD matrix after the output port and the non-resonant point NRN are exchanged is:
[0106]
[0107] Among them, Y LL It represents the series admittance value after the output port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2
[0108]
[0109] Step S5: Based on the admittance matrix of the broadband phase-shift filter with additional phase shift, the broadband phase-shift filter circuit parameters corresponding to the matrix are synthesized.
[0110] The non-resonant point NRN of the broadband phase-shift filter is exchanged with the input and output positions, and the converted non-resonant point NRN is connected with a capacitor C SS / C LL Or an inductor L SS / L LL The calculation method is as follows:
[0111]
[0112] Where ω0 represents the center frequency of the filter passband. The parameters of the broadband phase-shift filter circuit can be solved.
[0113] This embodiment is described by taking a fourth-order broadband filter with a passband range of 1-2.2 GHz and a return loss of -20 dB as a comprehensive example.
[0114] Figure 3FIG. 4 shows the topology of the fourth-order filter. In the figure, + represents positive coupling and - represents negative coupling. Except for the cross coupling between the second resonator and the fourth resonator, which is negative coupling, the rest are positive coupling. Figure 4 The circuit structure of the broadband phase-shift filter after the port circuit transformation is shown in Table 1. Table 1 shows the circuit synthesis results of the broadband phase-shift filter with an additional phase shift of -40° to 40° in 20° steps.
[0115] Table 1 Broadband phase-shift filter circuit and matrix parameter table
[0116]
[0117] Notice: Additional phase shift. The unit of capacitance is pF; the unit of inductance is nH.
[0118] Figure 5 Table 1 shows the amplitude and phase responses for the five states. All five states meet the broadband filter requirements of a 20dB return loss and a 1-2.2GHz bandwidth, and the amplitude responses are consistent across all cases. Taking Case 1 as the reference state, with a phase of 0°, the additional phase shift values for Cases 2, 3, 4, and 5 are consistent with the target phase shift values of 40°, 20°, -20°, and -40°, respectively. Experimental results confirm that the synthesized broadband phase-shift filter achieves an 80° phase shift at the center frequency, validating the effectiveness of the proposed synthesis method.
[0119] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.
Claims
1. A circuit synthesis method for a broadband phase-shift filter with a non-resonant port, characterized in that: The method comprises the following steps: Step S1: Based on the traditional matrix synthesis method, the admittance matrix of the traditional broadband filter is obtained; Step S2: adding a non-resonant point at the input and output ends of the traditional broadband filter respectively, adding the non-resonant point term to the admittance matrix of the traditional broadband filter, and constructing the admittance matrix of the broadband phase-shift filter with phase shift; Step S3: solving the parameter values that have changed in the admittance matrix of the broadband phase-shift filter relative to the admittance matrix of the traditional broadband filter, and obtaining the admittance matrix of the broadband phase-shift filter with additional phase shift; Step S4: Based on the ABCD matrix equivalent principle and the admittance matrix of the broadband phase-shift filter with additional phase shift, the input / output port coupling and the position of the non-resonance point are transformed to obtain the broadband phase-shift filter port coupling that can be realized by the circuit; Step S5: Based on the admittance matrix of the broadband phase-shift filter with additional phase shift, the broadband phase-shift filter circuit parameters corresponding to the matrix are synthesized.
2. The circuit synthesis method of a broadband phase-shift filter with a port non-resonance point according to claim 1, characterized in that: The admittance matrix of the traditional broadband filter in step S1 is expressed as follows: Where n is the filter order; j represents the imaginary unit; and represents the coupling between the i-th resonator and the k-th resonator, and and represents the coupling between the source and the i-th resonator, and and represents the coupling between the load and the i-th resonator, and represents the coupling between the source and the load, and represents the self-coupling of the i-th resonator, which can be expressed as follows: in and represents the equivalent capacitance and inductance of the i-th resonator in the traditional broadband filter, and ω represents the angular frequency.
3. The circuit synthesis method of a broadband phase-shift filter with a port non-resonance point according to claim 2, characterized in that: The admittance matrix of the broadband phase-shift filter in step S2 is expressed as follows: in, represents the self-coupling at the non-resonant point of the input port, represents the self-coupling at the non-resonant point of the output port, represents the coupling between the input port and the first resonator, represents the coupling between the nth resonator and the output port, represents the equivalent capacitance of the first resonator of the broadband phase-shift filter, represents the equivalent inductance of the first resonator of the broadband phase-shift filter, represents the equivalent capacitance of the nth resonator of the broadband phase-shift filter, represents the equivalent inductance of the nth resonator of the broadband phase-shift filter.
4. The circuit synthesis method of a broadband phase-shift filter with a port non-resonance point according to claim 3, characterized in that: The parameter values in step S3 are calculated as follows: and It is calculated as follows: in, and They represent the additional phase shift introduced at the input / output port of the broadband phase-shift filter; Let the phase shift of the output port be And the phase shift of the input port is Then we have: At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained: Where ω1 and ω2 are two arbitrary frequency points in the filter passband, is the S-parameter response of the admittance matrix [A0] of the traditional broadband filter, is the S-parameter response of the admittance matrix [A1] of the broadband phase-shifting filter, expressed as: in, The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A0] of the traditional broadband filter is represented by The element in the first row and the n+2th column of the inverse matrix of the admittance matrix [A1] of the broadband phase-shifting filter; represents the phase response of the admittance matrix [A0] of the conventional broadband filter, represents the phase response of the admittance matrix [A1] of the broadband phase-shift filter; imag(·) represents the extraction of the complex imaginary function, and real(·) represents the extraction of the complex real part function; Solving equation group (6) by combining formulas (1)-(8) can obtain the three unknown variables corresponding to the input port in the admittance matrix [A1] of the broadband phase-shift filter: Let the phase shift of the input port be And the phase shift of the output port is Then we have: At the same time, the passband amplitude of the filter remains unchanged before and after the phase shift, and the phase changes The following equation can be obtained: Solve equation (10) by combining formulas (1)-(4) and (7)-(10) to obtain the three unknown variables corresponding to the output port. and 5. The circuit synthesis method of a broadband phase-shift filter with a port non-resonance point according to claim 4, characterized in that: In step S4, the ABCD matrix corresponding to the input port before the non-resonance point NRN is swapped is: The corresponding ABCD matrix after the input port and the non-resonant point NRN are exchanged is: Among them, Y SS It represents the series admittance value after the input port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2 The ABCD matrix corresponding to the output port before exchanging positions with the non-resonant point NRN is: The corresponding ABCD matrix after the output port and the non-resonant point NRN are exchanged is: Among them, Y LL It represents the series admittance value after the output port circuit is transformed, and it can be obtained by [ABCD]1=[ABCD]2 6. The circuit synthesis method of a broadband phase-shift filter with a port non-resonance point according to claim 4, characterized in that: In step S5, the broadband phase-shift filter circuit parameter non-resonance point NRN is calculated using a capacitor C SS / C LL Or an inductor L SS / L LL The calculation method is as follows: Where ω0 represents the center frequency of the filter passband.