A method for constructing a broadband decoupling matching network suitable for multi-element linear arrays

Abstract

The present invention relates to a method for constructing a broadband decoupling matching network suitable for a multi-element linear array, comprising: judging and selecting a coupling curve whose frequency increases according to the variation trend of a mutual coupling curve to be compensated by an LC network; taking the mutual coupling admittance parameter equal to 0 as the target, obtaining the frequency response of the Y parameter of the decoupling network, obtaining an approximate rational function of the frequency response by vector fitting, and making it equivalent to a lumped element network, and establishing a four-stage LC decoupling network; since the antenna units are independent of each other at this time, the matching problem becomes a single-port matching problem, and obtaining the component value required by the wide-band matching network by vector fitting of broadband matching. The present invention has broadband performance because the decoupling matching network creates a continuous decoupling zero point; it can be applied to antenna arrays with more array elements and array elements of different forms; the proposed decoupling matching network can improve isolation, return loss, and achievable gain.

Description

Technical Field

[0001] The invention relates to the field of microwave circuits, and in particular to a method for constructing a broadband decoupling matching network suitable for a multi-element linear array. Background Art

[0002] Antenna arrays have been widely used in wireless systems such as multiple-input multiple-output (MIMO) communications, satellite communications, phased-control radars, and remote sensing networks. Since array elements are close to each other, there is always mutual coupling between them. Strong mutual coupling will greatly affect the array performance, such as the coupling coefficient between array elements.

[0003] To date, most of the reported broadband decoupling methods are applicable to dual-element antenna arrays, while the problem of multi-element antenna arrays has not been systematically solved; the difficulty lies in that broadband decoupling requires comprehensive consideration of the frequency response of continuous frequency points, and the decoupling of multi-element arrays is more challenging because there are more coupling paths in the array, so solving one coupling path may affect other paths, and vice versa. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for constructing a broadband decoupling matching network suitable for a multi-element linear array, thereby solving the deficiencies of the prior art.

[0005] The object of the present invention is achieved by the following technical solution: a method for constructing a broadband decoupling matching network suitable for a multi-element linear array, the method comprising:

[0006] Step 1: Pre-determine the decoupling frequency range: According to the changing trend of the mutual coupling curve, it is determined that the curve whose coupling curve increases with the frequency can be compensated by the LC network;

[0007] Step 2: Synthesize a broadband decoupling network: With the mutual coupling admittance parameter equal to 0 as the goal, obtain the frequency response of the decoupling network Y parameter, obtain the approximate rational function of the frequency response through vector fitting, and equate it to a lumped element network to establish a four-stage LC decoupling network;

[0008] Step 3: Synthesize a broadband matching network: Since the antenna units are independent of each other at this time, the matching problem becomes a single-port matching problem, and the component values ​​required for the broadband matching network are obtained through vector fitting of broadband matching.

[0009] The step 2 of establishing a four-stage LC decoupling network includes:

[0010] First level: The imaginary part of the mutual coupling admittance of the overall network is made 0 through a parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit methods;

[0011] The second stage: the imaginary part of the self-coupling admittance of the whole network is made 0 through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit method;

[0012] The third level: through the cascade network, the real part of the mutual coupling admittance of the overall network is made 0. The composition form and component values ​​of the network are completed by vector fitting and equivalent circuit method;

[0013] Level 4: The imaginary part of the mutual coupling admittance of the overall network is made 0 again through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit methods.

[0014] The vector fitting equation is:

[0015]

[0016] Among them, a n represents the extreme point, c n represents the residue corresponding to the pole, N represents the number of poles or residues, d and h are real numbers, and s represents the complex frequency.

[0017] The relationship between the approximate rational function and the equivalent network element value is:

[0018] C Y =k ∞ ,L Y =1 / k0,L i =1 / (2k i ),

[0019] Among them, k ∞ , k0, k i The poles of the admittance parameter are infinity, 0, and finite value jω i The residue at, j represents the imaginary unit, C Y Indicates the parallel capacitance value, L Y Indicates the parallel inductance value, L i With C i They represent the inductance and capacitance of the series resonance in the parallel network respectively;

[0020] or L Z =r ∞1 ,C Z =1 / r 01 ,C j =1 / (2r j ),

[0021] Among them, r ∞1 、r 01 、r j The poles of the impedance parameter are infinity, 0, and finite value jω jThe residue at C Z represents the series capacitance value, L Z Indicates the series inductance value, L j With C j They represent the inductance and capacitance of the parallel resonance in the series network respectively.

[0022] The width matching network includes one of an L-type broadband matching network, a Π-type broadband matching network and a T-type broadband matching network;

[0023] The L-type broadband matching network uses vector fitting to obtain component values ​​required for broadband matching;

[0024] The Π-type broadband matching network and the T-type broadband matching network utilize the broadband response of the lumped components to match the S 11 The trajectory moves to the equal voltage standing wave ratio circle required by the design.

[0025] The decoupling network produces continuous decoupling zeros over a wide frequency band.

[0026] The present invention has the following advantages: a method for constructing a broadband decoupling matching network suitable for a multi-element linear array; since the decoupling matching network is completely composed of LC elements, it has a small volume; since the decoupling matching network creates a continuous decoupling zero point, it has a wide-band performance; the proposed decoupling matching network can be applied to antenna arrays with more array elements and array elements of different forms; the proposed decoupling matching network can improve isolation, return loss and achievable gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of the present invention;

[0028] Figure 2 It is a schematic diagram of the construction process of the four-level broadband decoupling network of the present invention;

[0029] Figure 3 This is a schematic diagram of an equivalent network used in the present invention;

[0030] Figure 4 The frequency response diagrams of various rational functions obtained by vector fitting used in the present invention;

[0031] Figure 5 A scanning scattering parameter diagram of the broadband decoupling matching network of the present invention after being applied to a binary monopole antenna array;

[0032] Figure 6 This is a scanning admittance parameter diagram after the broadband decoupling matching network of the present invention is applied to a binary monopole antenna array. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided below in conjunction with the drawings is not intended to limit the scope of protection of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The present invention is further described below in conjunction with the drawings.

[0034] like Figure 1 As shown, the present invention specifically relates to a method for constructing a broadband decoupling matching network suitable for a multi-element linear array, taking the admittance matrix as the research target, with the purpose of making the mutual coupling admittance 0 in a wide frequency band, which specifically includes the following contents:

[0035] Step 1: Pre-determination of the decoupling frequency range: Since the first step in building a decoupling matching network is to make the imaginary part zero, the applicable frequency range must be determined. Figure 4 As shown, the curves all show an upward trend. According to the changing trend of the mutual coupling curve, it can be judged in advance that only the curves whose frequency increases can be compensated by the LC network. For the curves with other trends, passive devices such as transformers and resistors can be considered to be added, and microstrip lines or other active devices can also be added. The present invention does not limit the types of components.

[0036] Specifically, the vector fitting equation is:

[0037]

[0038] where a n is the extreme point, c n is the residue corresponding to the pole, N represents the number of poles or residues, d and h are real numbers, and s represents the complex frequency.

[0039] Since the decoupling matching network is composed entirely of passive LC components, its frequency response is a set of purely imaginary data that varies with frequency. The vector fitting equation can be further written as:

[0040]

[0041] where k ∞ , k0, k i The poles of the admittance parameter are infinity, 0, and finite value jω i The residue at j represents the imaginary unit, the residue is a positive real number and jω iis a pure imaginary number, and m represents the logarithm that satisfies the conjugate complex pair.

[0042] or,

[0043]

[0044] where r ∞1 、r 01 、r j The poles of the impedance parameter are infinity, 0, and finite value jω j The residue at , n represents the number of logarithms that satisfy the conjugate complex pair.

[0045] Step 2: Synthesize broadband decoupling network: With the mutual coupling admittance parameter equal to 0 as the goal, the frequency response of the decoupling network Y parameter is obtained. In the relevant frequency range, the real and imaginary parts of the Y parameter are zero. Subsequently, the approximate rational function of the frequency response is obtained by vector fitting, and it is equivalent to a lumped element network to establish a four-stage LC decoupling network.

[0046] like Figure 3 As shown in the figure, the relationship between the component value and the rational function parameter is:

[0047] C Y =k ∞ ,L Y =1 / k0,L i =1 / (2k i ),

[0048] C Y Representatives such as Figure 3 The shunt capacitance value, L Y Representatives such as Figure 3 The shunt inductance value, L i With C i Respectively represent Figure 3 The inductor and capacitor values ​​for series resonance in the parallel network shown.

[0049] or,

[0050] L Z =r ∞1 ,C Z =1 / r 01 ,C j =1 / (2r j ),

[0051] C Z Representatives such as Figure 3 The series capacitance value, L Z Representatives such as Figure 3 The series inductance value, L j With Cj Respectively represent Figure 3 The inductor and capacitor values ​​for parallel resonance in the series network shown.

[0052] Furthermore, if Figure 2 As shown, the construction steps of the four-level decoupling network are as follows:

[0053] First level: The imaginary part of the mutual coupling admittance of the overall network is made 0 through a parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit methods;

[0054] The second stage: the imaginary part of the self-coupling admittance of the whole network is made 0 through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit method;

[0055] The third level: through the cascade network, the real part of the mutual coupling admittance of the overall network is made 0. The composition form and component values ​​of the network are completed by vector fitting and equivalent circuit method;

[0056] Specifically, a network is connected in series at each port to achieve the goal of making the real part of the mutual coupling admittance of the overall network zero. The series networks connected to each port are symmetrically distributed due to the symmetry of the array. It can be proved that the required series networks always exist because the set of equations to be solved for the real part of the mutual coupling admittance to be zero is always well-posed or under-determined.

[0057] Level 4: The imaginary part of the mutual coupling admittance of the overall network is made 0 again through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit method;

[0058] Specifically, the introduction of the third-level network will cause a change in the imaginary part of the mutual coupling, so it is necessary to make the imaginary part of the mutual coupling admittance of the entire network zero again through a parallel network.

[0059] At this point, the decoupling step is completed, the decoupling target has been achieved, and the antenna units are independent of each other. It can be seen that the decoupling method proposed in the present invention can achieve the effect of broadband decoupling.

[0060] Step 3: Synthesize broadband matching network: Since the antenna units are independent of each other at this time, the matching problem becomes the matching problem of each single port. Since L-type matching has a specific expression, the relevant component values ​​are obtained by vector fitting of broadband matching. In addition, π-type, T-type and other cascaded broadband matching networks can also be used.

[0061] For ease of description, the decoupling effect of a binary monopole array is taken as an example. Figure 5 and Figure 6 As shown, assuming that the symmetric binary antenna array admittance matrix is:

[0062]

[0063] Where a(s) is the real part of a set of antenna self-coupling admittances that vary with frequency, b(s) is the imaginary part of a set of antenna self-coupling admittances that vary with frequency, c(s) is the real part of a set of antenna mutual coupling admittances that vary with frequency, and d(s) is the imaginary part of a set of antenna mutual coupling admittances that vary with frequency.

[0064] After adding the first-stage decoupling network, the first-stage decoupling network has an admittance value of Y comp1 =jd(s), the number of components may be more than one. The network composition and each component value are completed by vector fitting and equivalent circuit method. It is connected in parallel with the two ports of the antenna network, and the admittance matrix becomes:

[0065]

[0066] After adding the second-stage decoupling network, the second-stage decoupling network has an admittance value of Y comp2 =-j[b(s)+d(s)], the number of elements may be more than one, the network composition and each element value are completed by vector fitting and equivalent circuit method, which is connected to the two ports of the antenna in parallel and grounded respectively, and the admittance matrix becomes:

[0067]

[0068] After adding the third-level decoupling network, the impedance value of the third-level decoupling network is Z comp3 =jK(s), the number of components may be more than one. The network composition and each component value are completed by vector fitting and equivalent circuit method. It is connected in series with each port, and the admittance matrix becomes:

[0069]

[0070] After adding the fourth-level decoupling network, the fourth-level decoupling network has an admittance value of Y comp4 =-jc(s) / (2K(s)a(s)), the number of components may be more than one, the network composition and each component value are completed by vector fitting and equivalent circuit method, which is connected in parallel with the two ports of the antenna network, and the admittance matrix becomes:

[0071]

[0072] U(s) represents Y step4 The diagonal element value, K(s) is the impedance value of the third-level decoupling network Z comp3 The amplitude of .

[0073] like Figure 5As shown, the isolation of the original two-element monopole array in the frequency range of 3GHz-4.5GHz is 8dB to 11.6dB. Due to the use of a broadband decoupling matching network suitable for a multi-element linear array provided by the present invention, the isolation is improved to 18-29dB. In this frequency range, the return loss of both ports is better than 10dB.

[0074] like Figure 6 As shown, within the frequency range of 3 GHz-4.5 GHZ, both the real and imaginary parts of the mutual coupling admittance parameter are close to 0; the real part of the self-coupling admittance parameter is close to 0.02 (Z0=50Ω), and the imaginary part is close to 0.

[0075] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used for various other combinations, modifications and improvements, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for constructing a broadband decoupling matching network suitable for a multi-element linear array, characterized in that: The construction method comprises: Step 1: Pre-determine the decoupling frequency range: According to the changing trend of the mutual coupling curve, it is determined that the curve whose coupling curve increases with the frequency can be compensated by the LC network; Step 2: Synthesize a broadband decoupling network: With the mutual coupling admittance parameter equal to 0 as the goal, obtain the frequency response of the decoupling network Y parameter, obtain the approximate rational function of the frequency response through vector fitting, and equate it to a lumped element network to establish a four-stage LC decoupling network; Step 3: Synthesize a broadband matching network: Since the antenna units are independent of each other at this time, the matching problem becomes a single-port matching problem. The component values ​​required for the broadband matching network are obtained through vector fitting of broadband matching. The step 2 of establishing a four-stage LC decoupling network includes: First level: The imaginary part of the mutual coupling admittance of the overall network is made 0 through a parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit methods; The second stage: the imaginary part of the self-coupling admittance of the whole network is made 0 through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit method; The third level: through the cascade network, the real part of the mutual coupling admittance of the overall network is made 0. The composition form and component values ​​of the network are completed by vector fitting and equivalent circuit method; Level 4: The imaginary part of the mutual coupling admittance of the overall network is made 0 again through the parallel network. The composition form and component values ​​of the network are completed through vector fitting and equivalent circuit methods.

2. The method for constructing a broadband decoupling matching network suitable for a multi-element linear array according to claim 1, characterized in that: The vector fitting equation is: in, Indicates the extreme point, represents the residue corresponding to the pole, N represents the number of poles or residues, d and h are real numbers, and s represents the complex frequency.

3. The method for constructing a broadband decoupling matching network suitable for a multi-element linear array according to claim 1, characterized in that: The relationship between the approximate rational function and the equivalent network element value is: in, , , The poles of the admittance parameter are at infinity, 0, and finite values. The number of residues at j represents the imaginary unit, represents the parallel capacitance value, represents the parallel inductance value, and They represent the inductance and capacitance of the series resonance in the parallel network respectively; or in, , , The poles of the impedance parameter are infinite, zero, and finite. The number of residues at represents the series capacitance value, represents the series inductance value, and They represent the inductance and capacitance of the parallel resonance in the series network respectively.

4. The method for constructing a broadband decoupling matching network suitable for a multi-element linear array according to claim 1, characterized in that: The width matching network includes one of an L-type broadband matching network, a Π-type broadband matching network and a T-type broadband matching network; The L-type broadband matching network uses vector fitting to obtain component values ​​required for broadband matching; The Π-type broadband matching network and the T-type broadband matching network utilize the broadband response of the lumped components to match the S 11 The trajectory moves to the equal voltage standing wave ratio circle required by the design.

5. The method for constructing a broadband decoupling matching network suitable for a multi-element linear array according to claim 4, characterized in that: The decoupling network produces continuous decoupling zeros over a wide frequency band.

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