A reconfigurable phase-shift filter design method with frequency-dependent coupling characteristics

Abstract

The application discloses a reconfigurable phase shift filter design method with frequency-dependent coupling characteristics, comprising the following steps: given target parameter values of a filter and coupling inductance values in a frequency-dependent coupling structure; corresponding variables (coupling matrix element values and circuit element values) to be optimized in the filter to optimization variables in an optimization algorithm; obtaining optimization variable values by using the optimization algorithm to obtain a new coupling matrix; calculating an error function value through the new coupling matrix to determine whether a convergence condition is met; if the convergence condition is met, deriving the optimization variable values and substituting the optimization variable values into the circuit. The application combines the optimization method of the coupling matrix element and the circuit element value, uses the frequency-dependent coupling structure, does not need to adjust the inductance value in the coupling structure, and independently adjusts the filter center frequency, transmission phase and phase slope. Moreover, the coupling structure with the frequency-dependent characteristic introduces multiple transmission zeros, and improves the frequency selection characteristic of the phase shift filter.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and in particular to a design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics. Background Technology

[0002] Bandpass filters and phase shifters are essential components of radio frequency (RF) systems. Phase shifters are widely used in phased array systems to control the scanning direction of the beam; by changing the transmission phase of the phase shifter, different beam scanning angles can be obtained. On the other hand, bandpass filters are widely used to select the desired signal. To reduce the cost and size of RF systems, engineers have proposed a circuit that combines filtering and phase shifting functions—the phase-shifting filter.

[0003] Phase-shifting filters typically require high frequency selectivity, minimal phase error within the passband, and the ability to flexibly adjust the passband center frequency and transmission phase. To achieve high frequency selectivity, a common practice is to introduce frequency-dependent coupling between resonators to generate more transmission zeros outside the filter's passband. Conversely, to achieve small phase error, the circuit needs the ability to adjust the phase slope to ensure consistency across all phase states.

[0004] Traditional phase-shift filter design methods typically involve using network synthesis to derive the circuit structure and component parameters based on the desired amplitude and phase responses. However, with this approach, once the circuit parameters are determined, the passband frequency and transmission phase are uniquely fixed, resulting in a lack of flexible adjustment capabilities. Furthermore, existing reconfigurable filter design methods do not consider the frequency-dependent characteristics of the coupling structure, making it impossible to accurately predict the location of the transmission zero during adjustment. To achieve reconfigurability of the frequency-dependent coupling coefficients, the values ​​of both the capacitor and inductor in the coupling structure need to be changed simultaneously. However, in practical circuits, it is difficult to flexibly control the inductor value, rendering existing methods unsuitable for reconfigurable phase-shift filter designs with frequency-dependent coupling characteristics. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a design method for a reconfigurable phase-shift filter with frequency-dependent coupling characteristics. This invention is a reconfigurable phase-shift filter design method formed by combining the optimization of coupling matrix and circuit element values, and is applicable to the design of reconfigurable phase-shift filters with frequency-dependent coupling characteristics.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics, characterized by comprising:

[0008] S1: Given the target parameter values ​​of the filter and the coupling inductance value in the frequency-dependent coupling structure;

[0009] S2: Match the variables to be optimized in the filter with the optimization variables in the optimization algorithm; the variables to be optimized in the filter include the values ​​of coupling matrix elements and circuit element values;

[0010] S3: Use optimization algorithms to obtain the optimized variable values ​​and obtain a new coupling matrix;

[0011] S4: Calculate the error function value using the newly obtained coupling matrix and determine whether the convergence condition is met;

[0012] S5: If the convergence condition is met, derive the optimized variable values ​​and substitute them into the circuit.

[0013] Preferably, the element values ​​of the coupling matrix include the external coupling coefficient m. s1 m nL The resonator's self-resonant frequency m ii The circuit element values ​​include the coupling capacitance value C in the coupled structure. ij Where i and j represent the i-th and j-th resonators, respectively.

[0014] Preferably, the target parameter values ​​of the filter in step S1 include: the target center frequency, target bandwidth, target return loss, target phase, and target phase slope of the designed phase-shifting filter.

[0015] Preferably, the error function value in step S4 is calculated using the optimization target parameter value and filter S-parameters given in step S1; the filter S-parameters are calculated using the coupling matrix [m] obtained in step S3.

[0016] in

[0017] Where [A] = [m] + Ω[U] - j[q], Ω represents the normalized frequency variable, and [U] represents [U] 1,1 =[U] 6,6 The identity matrix with 0, [q] represents [q]. 1,1 =[q] 6,6 =1 is a matrix in which all other terms are 0.

[0018] Preferably, the error function in step S4 is expressed as:

[0019]

[0020] In this equation, the first term on the right-hand side represents the error between the optimized return loss and the target; the second and third terms represent the error between the optimized passband edge return loss and the target; the fourth term represents the error between the optimized transmission phase and the target; and the fifth term represents the error between the optimized phase slope and the target.

[0021] Preferably, in step S3, the new coupling matrix is ​​the external coupling coefficient m obtained using an optimization algorithm. s1 m nL The resonator's self-resonant frequency m ii With optimized circuit element value C ij It is obtained by combining.

[0022] Preferably, the inter-level coupling coefficient m in the coupling matrix ij It is represented as:

[0023]

[0024] This represents the normalized coupling coefficient of adjacent resonators i and j, where ω represents the frequency variable, FBW represents the filter bandwidth, and b... i and b j C represents the admittance slope of the i-th and j-th resonators. ij and L ij This represents the component parameters of the corresponding frequency-dependent coupling structure.

[0025] Preferably, the filter is a fourth-order bandpass phase-shifting filter.

[0026] Preferably, the inter-resonator capacitance C of the filter... ij Introducing capacitive coupling, L ij Introducing inductive coupling, through a fixed L ij Adjust C ij In this way, the total coupling coefficient m ij To meet the requirements of the filter.

[0027] Preferably, step S5 determines whether the convergence condition is met based on a preset convergence threshold. If the convergence condition is met, the optimization is stopped and the value of the optimized variable is derived; otherwise, the process returns to step S3 to continue the calculation.

[0028] The beneficial effects of this invention are reflected in:

[0029] 1. This invention introduces multiple transmission zeros through a coupling structure with frequency-dependent characteristics, thereby improving the frequency selectivity of the phase-shifting filter. 2. By flexibly adjusting the circuit parameters in the coupling structure, this invention can adjust the transmission phase and phase slope while maintaining a constant in-band amplitude response. 3. The optimization method combining the coupling matrix and circuit parameters proposed in this invention can keep the inductor value in the frequency-dependent coupling structure constant, and adjust the filter's transmission phase, center frequency, and phase slope simply by changing the capacitance value, thus enabling the realization of a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics. Attached image description:

[0030] Figure 1 The flowchart of the phase-shifting filter design method provided by the present invention is shown below;

[0031] Figure 2 This is the coupled topology of the present invention;

[0032] Figure 3 This is the circuit structure for frequency-dependent coupling between resonators in this invention;

[0033] Figure 4 This is an optimized example of the present invention;

[0034] Figure 5 This is a physical processing diagram of the present invention;

[0035] Figure 6 The results are the measured values ​​at 600MHz in this invention.

[0036] Figure 7 The actual measured results at 650MHz are from this invention;

[0037] Figure 8 The measured results at 710MHz are from this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Please see Figure 1-8 As shown, the specific embodiments provided by the present invention are as follows:

[0040] Example 1

[0041] S1: Given three sets of target parameter values ​​for the designed phase-shifting filter, where the target transmission phases are 80°, 110°, and 140°, and all are optimized with a center frequency of 650MHz, a relative bandwidth of 10%, and a return loss of 20dB, and pre-determine the inductor L in the coupling structure. ij =25nH, the admittance slope of the resonator at the center frequency is 0.082.

[0042] S2: Map the variables to be optimized in the filter to the optimization variables in the optimization algorithm. The parameters to be optimized in the filter include the values ​​of the coupling matrix elements and the values ​​of the circuit components. The values ​​of the coupling matrix elements include the external coupling coefficients m. s1 m nL The resonator's self-resonant frequency m ii The circuit element values ​​include the coupling capacitance value C in the coupled structure. ij .

[0043] S3: Obtain the optimized variable values ​​using an optimization algorithm, and then calculate the inter-level coupling coefficients m in the coupling matrix. ij (i≠j) use Figure 2 The capacitance and inductance values ​​in the figure are expressed as follows:

[0044]

[0045] Where m ij Let ω represent the normalized coupling coefficient of adjacent resonators i and j, ω represent the frequency variable, FBW represent the bandwidth of the filter, and b represent the normalized coupling coefficient of adjacent resonators i and j. i and b j C represents the admittance slope of the i-th and j-th resonators. ij and L ij This represents the component parameters corresponding to the frequency-dependent coupling structure. The calculated m... ij By combining the coupling matrix parameter in the optimization variables, a new coupling matrix is ​​obtained.

[0046] S4: Calculate the filter S-parameters using the coupling matrix obtained in step three:

[0047]

[0048]

[0049] Where [A] = [m] + Ω[U] - j[q] represents the normalized frequency variable, Ω represents the normalized frequency variable, and [U] represents [U] 1,1 =[U] 6,6 The identity matrix with 0, [q] represents [q]. 1,1 =[q] 6,6 =1, and all other terms are 0.

[0050] S5: The error function is expressed as:

[0051]

[0052] In this equation, the first term on the right-hand side represents the error between the optimized return loss and the target return loss; the second and third terms represent the errors between the optimized passband edge return loss and the target return loss; the fourth term represents the error between the optimized transmission phase and the target phase; and the fifth term represents the error between the optimized phase slope and the target phase slope. The error function value is calculated using the target parameters input in step S1 and the S-parameters obtained in step S4. Based on the pre-set maximum number of iterations or a pre-set convergence condition, it is determined whether the convergence condition is met. If the convergence condition is met, optimization stops, and the optimization result is exported; otherwise, the process returns to step S3 to continue calculation.

[0053] S6: Substitute the optimized variable values ​​into the circuit.

[0054] In this embodiment, a fourth-order bandpass phase-shifting filter is designed. The coupling topology of the designed circuit is as follows: Figure 2 As shown, the filter circuit topology is as follows: Figure 3 As shown. Using this circuit topology and the proposed method, three optimization cases were implemented. The target transmission phases for the three optimization cases were 80°, 110°, and 140°, respectively. All three cases had a center frequency of 650MHz, a relative bandwidth of 10%, and a return loss of 20dB as optimization targets, and the inductor L in the coupling structure was preset. ij =25nH, the admittance slope of the resonator at the center frequency is 0.082. The optimization results obtained using the proposed optimization method are shown in Table 1, and the response is as follows: Figure 4 As shown. The optimization results satisfy the target response, achieving adjustment of the transmission phase and phase slope while keeping the in-band amplitude response unchanged. At the same time, the inductance value in the frequency-dependent coupling structure can be kept constant, and the transmission phase, center frequency, and phase slope of the filter can be adjusted simply by changing the capacitance value, thus realizing a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics.

[0055] Table 1

[0056]

[0057] Example 2

[0058] In this embodiment, as a further improvement to Embodiment 1, a verification circuit was fabricated using a microstrip structure. The dielectric substrate used was Rogers 6010, with a substrate thickness of 0.635 mm. As shown in Figure 5, C1-C4 and C... 12 C 34C e1 and C e2 A variable capacitance tube using MA46H204 is used, C 13 C 24 The system uses an MA46H202 varactor diode, with all other capacitors being 100pF and all resistors being 100kΩ. The inter-resonator capacitance C... 12 C 13 C 24 C 34 This will introduce capacitive coupling, equivalent to Figure 2 In the middle coupling capacitor, the coupling gap between the resonators will introduce inductive coupling, which is equivalent to Figure 2 Medium-coupled inductor.

[0059] Figure 6 , Figure 7 , Figure 8 The amplitude and phase test results of the phase-shifting filter at three different frequency points are shown. The test results demonstrate frequency adjustment from 600MHz to 710MHz. The insertion losses at 600MHz, 650MHz, and 700MHz are 2.3dB–3dB, 2.2dB–2.6dB, and 1.9dB–2.4dB, respectively. A phase adjustment range greater than 175° was achieved at each frequency point, and three out-of-band transmission zeros are consistent with the optimization results, improving the frequency selectivity of the phase-shifting filter.

[0060] In the description of the embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "center", "top", "bottom", "top", "bottom", "inner", "outer", "inner side", "outer side", etc. indicate the orientation or positional relationship.

[0061] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "assembly" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0062] In the description of embodiments of the present invention, specific features, structures, materials or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0063] In the description of the embodiments of the present invention, it should be understood that "-" and "~" represent a range of two values, and this range includes the endpoints. For example, "AB" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0064] In the description of embodiments of the present invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics, characterized in that, include: S1: Given the target parameter values ​​of the filter and the coupling inductance value in the frequency-dependent coupling structure; The target parameter values ​​of the filter include: the target center frequency, target bandwidth, target return loss, target phase, and target phase slope of the designed phase-shifting filter; S2: Match the variables to be optimized in the filter with the optimization variables in the optimization algorithm; the variables to be optimized in the filter include the values ​​of coupling matrix elements and circuit element values; S3: Obtain the optimized variable values ​​using an optimization algorithm to obtain a new coupling matrix; the new coupling matrix in step S3 is the external coupling coefficient obtained using the optimization algorithm. m s1 , m nL Resonator self-resonant frequency m ii With optimized circuit element values C ij Obtained by combination; The inter-resonator capacitance of the filter C ij Introducing capacitive coupling, L ij Introducing inductive coupling, through fixed L ij ,Adjustment C ij In this way, the total coupling coefficient is reduced. m ij To meet the requirements of the filter; S4: Calculate the error function value using the obtained new coupling matrix, and determine whether the convergence condition is met; S5: If the convergence condition is met, derive the optimized variable values ​​and substitute them into the circuit.

2. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 1, characterized in that: The element values ​​of the coupling matrix include the external coupling coefficient m. s1 m nL The resonator's self-resonant frequency m ii The circuit element values ​​include the coupling capacitance value C in the coupled structure. ij Where i and j represent the i-th and j-th resonators, respectively.

3. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 2, characterized in that: The error function value in step S4 is calculated using the optimization target parameter value and filter S-parameters given in step S1; the filter S-parameters are calculated using the coupling matrix [m] obtained in step S3. in , ; in , Represents the normalized frequency variable, express[ U ] 1,1 =[ U ] 6,6 = 0 identity matrix express[ q ] 1,1 =[ q ] 6,6 A matrix where 1 is a matrix and all other terms are 0.

4. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 3, characterized in that: The error function in step S4 is expressed as follows: ； In this equation, the first term on the right-hand side represents the error between the optimized return loss and the target return loss; the second and third terms represent the error between the optimized passband edge return loss and the target return loss; the fourth term represents the error between the optimized transmission phase and the target phase; and the fifth term represents the error between the optimized phase slope and the target phase slope.

5. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 4, characterized in that: The inter-level coupling coefficients in the coupling matrix m ij It is represented as: ； This is used to represent adjacent resonators. i and j The normalized coupling coefficients, where, ω FBW represents the bandwidth of the filter, representing the frequency variable. b i and b j Indicates the first i The and the first j The admittance slope of a resonator C ij and L ij This represents the component parameters of the corresponding frequency-dependent coupling structure.

6. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 5, characterized in that... : The filter is a fourth-order bandpass phase-shifting filter.

7. The design method for a reconfigurable phase-shifting filter with frequency-dependent coupling characteristics according to claim 1, characterized in that... : Step S5 determines whether the convergence condition is met based on a pre-set convergence threshold. If the convergence condition is met, the optimization is stopped and the value of the optimized variable is derived; otherwise, the process returns to step S3 to continue the calculation.

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