Broadband equalization network, single directional coupler and dual directional coupler

Abstract

The invention discloses a broadband equalization network, a single directional coupler and a dual directional coupler. The broadband equalization network comprises a main resonator and an equalization circuit, the equalization circuit comprises at least one first L-shaped branch equalization module, a second L-shaped branch equalization module and a third L-shaped branch equalization module; the first end of the first L-shaped branch equalization module is electrically connected with the second end of the main resonator; the second end of the first L-shaped branch equalization module is electrically connected with the first end of the second L-shaped branch equalization module; the second end of the second L-shaped branch equalization module is electrically connected with the second end of the third L-shaped branch equalization module; the first end of the third branch L-shaped equalization module is electrically connected with the first end of the first main resonator; the first end of the main resonator is electrically connected with any coupling end of the coupling channel of the directional coupler; according to the scheme, the bandwidth of the directional coupler is improved through the broadband equalization network.

Description

Technical Field

[0001] This invention relates to radio frequency signal technology, and more particularly to a broadband equalization network, a unidirectional coupler, and a bidirectional coupler. Background Technology

[0002] Currently, for multi-core imaging in MRI medical imaging ranging from 1.5T to 9.4T, a broadband radio frequency (RF) power amplifier with a bandwidth of 8MHz–420MHz is required, with a peak power of up to 6kW at 10% duty cycle. The output signal of the RF power amplifier needs to be acquired so that the input signal can be nonlinearly corrected. A directional coupler can detect the coupled signal to determine the actual output signal of the RF power amplifier, thus performing nonlinear correction together with the input signal.

[0003] A directional coupler is a commonly used radio frequency (RF) component that couples a portion of energy from the main transmission path to a specific port for acquiring forward signals or monitoring reflected signals. Currently, directional couplers in bridge-T RF equalization network technology are limited by bandwidth, and their coupling port return loss is relatively poor. Summary of the Invention

[0004] This invention provides a broadband equalization network, a single directional coupler, and a dual directional coupler to improve the bandwidth of the directional coupler and reduce its coupling port return loss through the broadband equalization network.

[0005] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a broadband equalization network, the broadband equalization network comprising: a main resonator and an equalization circuit; the equalization circuit comprises at least a first L-type branch equalization module, a second L-type branch equalization module and a third L-type branch equalization module;

[0006] The first end of the first L-shaped branch equalization module is electrically connected to the second end of the main resonator; the second end of the first L-shaped branch equalization module is electrically connected to the first end of the second L-shaped branch equalization module; the second end of the second L-shaped branch equalization module is electrically connected to the second end of the third branch L-shaped equalization module; the first end of the third branch L-shaped equalization module is electrically connected to the first end of the first main resonator; the first end of the main resonator is electrically connected to any coupling end of the coupling channel of the directional coupler; the second end of the main resonator serves as the coupling end of the bidirectional coupler.

[0007] Optionally, the first L-shaped branch equalization module includes a first resistor, a first capacitor, and a second resistor;

[0008] One end of the first resistor serves as the first end of the first L-shaped branch equalization module and is electrically connected to the second end of the first main resonator; the second end of the first resistor is electrically connected to the first end of the first capacitor; the second end of the first capacitor is electrically connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the second end of the first L-shaped branch equalization module and is electrically connected to the first end of the second L-shaped branch equalization module.

[0009] Optionally, the first L-shaped branch equalization module includes a first resistor, a first capacitor, a second resistor, and a second capacitor;

[0010] One end of the first resistor serves as the first end of the first L-shaped branch equalization module and is electrically connected to the second end of the first main resonator; the second end of the first resistor is electrically connected to the first end of the first capacitor; the second end of the first capacitor is electrically connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the second end of the first L-shaped branch equalization module and is electrically connected to the first end of the second L-shaped branch equalization module; the second capacitor and the second resistor are connected in parallel.

[0011] Optionally, the second L-shaped branch equalization module includes a third resistor, a third capacitor, and a fourth resistor;

[0012] One end of the third resistor serves as the first end of the second L-shaped branch equalization module and is electrically connected to the second end of the first L-shaped branch equalization module; the second end of the third resistor is electrically connected to the first end of the third capacitor; the second end of the third capacitor is electrically connected to the first end of the fourth resistor; the second end of the fourth resistor is grounded; the second end of the third resistor serves as the second end of the second L-shaped branch equalization module and is electrically connected to the second end of the third L-shaped branch equalization module.

[0013] Optionally, the second L-shaped branch equalization module includes a third resistor, a third capacitor, a fourth resistor, and a fourth capacitor;

[0014] One end of the third resistor serves as the first end of the second L-shaped branch equalization module and is electrically connected to the second end of the first L-shaped branch equalization module; the second end of the third resistor is electrically connected to the first end of the third capacitor; the second end of the third capacitor is electrically connected to the first end of the fourth resistor; the second end of the fourth resistor is grounded; the second end of the third resistor serves as the second end of the second L-shaped branch equalization module and is electrically connected to the second end of the third L-shaped branch equalization module; the fourth capacitor and the fourth resistor are connected in parallel.

[0015] Optionally, the third L-shaped branch equalization module includes a fifth resistor and a first inductor;

[0016] The first end of the fifth resistor serves as the second end of the third L-shaped branch equalization module and is electrically connected to the second end of the second L-shaped branch equalization module; the second end of the fifth resistor is electrically connected to the first end of the first main resonator; the first end of the fifth resistor is electrically connected to the first end of the first inductor; and the second end of the first inductor is grounded.

[0017] Optionally, the main resonator includes a series inductor and a series capacitor; the series inductor and the series capacitor are connected in series.

[0018] Alternatively, the main resonator may include a parallel inductor and a parallel capacitor; the parallel inductor and the parallel capacitor may be connected in parallel.

[0019] In a second aspect, embodiments of the present invention also provide a unidirectional coupler, which includes: a unidirectional coupler body and the broadband equalization network described in the first aspect above;

[0020] The unidirectional coupler body includes a main transmission channel and a coupling channel; the broadband equalization network is connected to the coupling end of the coupling channel.

[0021] Thirdly, embodiments of the present invention also provide a dual-directional coupler, which includes: a bidirectional coupler body and two broadband equalization networks as described in the first aspect above;

[0022] The bidirectional coupler body includes a main transmission channel, a coupling channel, and a reverse coupling channel; the coupling end of the coupling channel is symmetrical about the main transmission channel and the reverse coupling end of the reverse coupling channel.

[0023] One of the broadband equalization networks is coupled to the coupling end of the coupling channel; the other broadband equalization network is coupled to the coupling end of the reverse coupling channel.

[0024] Optionally, the coupling channel and the reverse coupling channel are arranged on the same layer;

[0025] The coupling channel is configured on a different layer than the main transmission channel.

[0026] Optionally, the dual-directional coupler further includes: a medium channel; the medium channel covers the upper surface of the main transmission channel; the projected area of ​​the medium channel on the plane where the coupling channel is located is the area between the coupling channel and the reverse coupling channel.

[0027] In this embodiment of the invention, the first end of the first L-shaped branch equalization module is electrically connected to the second end of the main resonator; the second end of the first L-shaped branch equalization module is electrically connected to the first end of the second L-shaped branch equalization module; the second end of the second L-shaped branch equalization module is electrically connected to the second end of the third branch L-shaped equalization module; the first end of the third branch L-shaped equalization module is electrically connected to the first end of the main resonator; and the first end of the main resonator is electrically connected to the coupling end of the coupling channel of the external directional coupler. This generates a monotonically decreasing frequency gain curve for the main resonator. The second and third L-shaped branch equalization modules can adjust the monotonically decreasing frequency gain curve generated by the main resonator. The first L-shaped branch equalization modules further adjust the adjusted monotonically decreasing frequency gain curve, thereby compensating for the monotonically increasing frequency gain curve output from the coupling end of the external directional coupler. This results in smaller fluctuations in the flatness of the gain-frequency curve within the overall operating frequency, thus increasing the bandwidth.

[0028] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a broadband balanced network provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of a broadband equalization network provided in an embodiment of the present invention;

[0032] Figure 3 This is a frequency-coupling curve related to the forward transmission impedance of a broadband balanced network provided in an embodiment of the present invention;

[0033] Figure 4 This is a frequency-coupling degree curve of a bidirectional coupler body provided in an embodiment of the present invention;

[0034] Figure 5 This is a frequency-coupling curve of a dual directional coupler after adding a broadband equalization network to the two coupling ends of the bidirectional coupler body, as provided in an embodiment of the present invention.

[0035] Figure 6 This invention provides a frequency-voltage standing wave ratio curve for determining the output impedance of a broadband equalization network.

[0036] Figure 7 It is a frequency-voltage standing wave ratio curve of the directional coupler after adding a broadband equalization network to the two coupling ends of the bidirectional coupler body;

[0037] Figure 8 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention;

[0038] Figure 9 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention;

[0039] Figure 10 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention;

[0040] Figure 11 This is a schematic diagram of a unidirectional coupler provided in an embodiment of the present invention;

[0041] Figure 12 This is a schematic diagram of a dual directional coupler provided in an embodiment of the present invention;

[0042] Figure 13 This is a schematic diagram of the physical location of a bidirectional coupler body provided in an embodiment of the present invention;

[0043] Figures 14-17 This is a field-path cooperative simulation result of a dual directional coupler from a broadband equalization network to the bidirectional coupler body provided in an embodiment of the present invention;

[0044] Figures 18-21 This is the test result of a unidirectional coupler prototype from a broadband balanced network to the unidirectional coupler body provided in an embodiment of the present invention. Detailed Implementation

[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0047] Figure 1 This is a schematic diagram of the structure of a broadband balanced network provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the broadband equalization network 01 includes: a main resonator 10 and an equalization circuit 20; the equalization circuit includes at least a first L-shaped branch equalization module 21, a second L-shaped branch equalization module 22 and a third L-shaped branch equalization module 23.

[0048] The first end of the first L-shaped branch equalization module 21 is electrically connected to the second end of the main resonator 10; the second end of the first L-shaped branch equalization module 21 is electrically connected to the first end of the second L-shaped branch equalization module 22; the second end of the second L-shaped branch equalization module 22 is electrically connected to the second end of the third branch L-shaped equalization module 23; the first end of the third branch L-shaped equalization module 23 is electrically connected to the first end of the main resonator 10; and the first end of the main resonator 10 is electrically connected to the coupling end C1A of the coupling channel of the external directional coupler.

[0049] The main resonator 10 can generate a monotonically decreasing frequency gain curve. Specifically, the main resonator 10 can include a series inductor and a series capacitor. The series inductor and the series capacitor are connected in series, and when resonating at a low frequency, the main resonator 10 can generate a monotonically decreasing frequency gain curve starting from the low frequency band. The main resonator 10 can also include a parallel inductor and a parallel capacitor. The parallel inductor and the parallel capacitor are connected in parallel, and when resonating at a high frequency, the main resonator 10 can generate a monotonically decreasing frequency gain curve ending at the high frequency band.

[0050] The second L-type branch equalization module 22 and the third L-type branch equalization module 23 can adjust the monotonically decreasing frequency gain curve generated by the main resonator 10; for example, the monotonically decreasing trend can be changed; this embodiment does not limit the configuration of the second L-type branch equalization module 22 and the third L-type branch equalization module 23.

[0051] The first L-shaped branch equalization module 21 can further adjust the monotonically decreasing frequency gain curve after adjustment; for example, it can further adjust the monotonically decreasing trend; this embodiment does not limit the configuration of the first L-shaped branch equalization module 21; the number of first L-shaped branch equalization modules 21 is not limited; in this way, the main resonator 10, the second L-shaped branch equalization module 22, the third L-shaped branch equalization module 23 and each first L-shaped branch equalization module 21 can compensate for the monotonically increasing frequency gain curve output from the coupling end of the external directional coupler, thereby making the flatness fluctuation of the gain-frequency curve within the overall operating frequency small, thus increasing the operating frequency band of the overall broadband equalization network, that is, increasing the bandwidth of the overall broadband equalization network;

[0052] It should be noted that when the main resonator 10 is composed of an inductor and a capacitor connected in series, the main resonator 10, the second L-shaped branch equalization module 22, the third L-shaped branch equalization module 23, and each of the first L-shaped branch equalization modules 21 can compensate for the monotonically increasing frequency gain curve of the output of the external directional coupler. Thus, the main resonator 10 compensates for the monotonically increasing frequency gain curve of the output of the external directional coupler above the low-frequency range. This means that the resonant frequency of the main resonator 10 is the lowest frequency of the overall broadband equalization network's operating frequency band. Frequency; When the main resonator 10 is composed of inductors and capacitors connected in parallel, the main resonator 10, the second L-type branch equalization module 22, the third L-type branch equalization module 23 and each first L-type branch equalization module 21 can compensate for the monotonically increasing frequency gain curve of the output of the coupling end of the external directional coupler. In this way, the main resonator 10 compensates for the monotonically increasing frequency gain curve of the output of the coupling end of the external directional coupler below the high frequency band. Thus, the resonant frequency of the main resonator 10 is the highest frequency of the overall broadband equalization network operating frequency band.

[0053] In this embodiment of the invention, a monotonically decreasing frequency gain curve is generated by the main resonator 10. The monotonically decreasing frequency gain curve generated by the main resonator 10 can be adjusted by the second L-type branch equalization module 22 and the third L-type branch equalization module 23. The adjusted monotonically decreasing frequency gain curve is further adjusted by each first L-type branch equalization module 21. This further adjusts the monotonically decreasing frequency gain curve to compensate for the monotonically increasing frequency gain curve output from the coupling end of the external directional coupler. As a result, the flatness fluctuation of the gain-frequency curve within the overall operating frequency is small, thus increasing the bandwidth.

[0054] Optionally, based on the above embodiments, each module can be further refined. Figure 2 This is a schematic diagram of a broadband equalization network provided in an embodiment of the present invention, as shown below. Figure 2As shown, in one embodiment, the first L-shaped branch equalization module 21 includes a first resistor R1, a first capacitor C1, and a second resistor R2; one end of the first resistor R1 serves as the first end of the first L-shaped branch equalization module 21 and is electrically connected to the second end of the main resonator 10; the second end of the first resistor R1 is electrically connected to the first end of the first capacitor C1; the second end of the first capacitor C1 is electrically connected to the first end of the second resistor R2; the second end of the second resistor R2 is grounded; the second end of the first resistor R1 serves as the second end of the first L-shaped branch equalization module 21 and is electrically connected to the first end of the second L-shaped branch equalization module 22.

[0055] Optional, continue to refer to Figure 2 The second L-shaped branch equalization module 22 includes a third resistor R3, a third capacitor C3, and a fourth resistor R4; one end of the third resistor R3 serves as the first end of the second L-shaped branch equalization module 22 and is electrically connected to the second end of the first L-shaped branch equalization module 22; the second end of the third resistor R3 is electrically connected to the first end of the third capacitor C3; the second end of the third capacitor C3 is electrically connected to the first end of the fourth resistor R4; the second end of the fourth resistor R4 is grounded; the second end of the third resistor R3 serves as the second end of the second L-shaped branch equalization module 21 and is electrically connected to the second end of the third L-shaped branch equalization module 23.

[0056] Optional, continue to refer to Figure 2 The third L-shaped branch equalization module 23 includes a fifth resistor R5 and a first inductor L1; the first end of the fifth resistor R5 serves as the second end of the third L-shaped branch equalization module 23 and is electrically connected to the second end of the second L-shaped branch equalization module 22; the second end of the fifth resistor R5 is electrically connected to the first end of the main resonator 10; the first end of the fifth resistor R5 is electrically connected to the first end of the first inductor L1; the second end of the first inductor L1 is grounded.

[0057] Specifically, this embodiment takes the main resonator 10, which includes a series inductor L0 and a series capacitor C0, as an example, and explains the equalization principle of the broadband equalization network in conjunction with the specific composition of the first L-type branch equalization module 21, the second L-type branch equalization module 22, and the third L-type branch equalization module 21:

[0058] For further explanation of broadband balanced networks, please refer to... Figure 2 Wherein, the inductor impedance is represented as sL, the capacitor impedance as 1 / sC, L is the inductance value, C is the capacitance value, and s is the complex frequency variable in the Laplace transform. To explain the equalization principle of the broadband equalization network, we first perform a Π-type circuit equivalent on L1, C3, R4, C1, and R2 in the equalization circuit 20, i.e., the branches of L1, C3, and R4 are connected in parallel, and their impedance is equivalently represented as Z1; the branch of C1 and R2 has its impedance equivalently represented as Z2; thus, R3, Z1, and Z2 form a Π-type circuit.

[0059]

[0060]

[0061] Then, a T-type equivalent is performed on the Π-type circuit, i.e., Z01, Z02, and Z03 are the equivalent impedances in the T-type network; specifically:

[0062]

[0063]

[0064]

[0065] Then take into account R1 and R5 in the equalization circuit 20;

[0066]

[0067]

[0068]

[0069] To investigate the transmission characteristics of the broadband equalization circuit 20, the equivalent T-type circuit, combined with R1 and R5, is compared using the ABCD parameter transmission matrix method. The following system of equations can be solved to obtain the following:

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] Where A, B, C, and D are commonly used parameters in the ABCD parameter transfer matrix method; Z11 is the input impedance of the broadband equalization circuit 20; Z22 is the output impedance of the broadband equalization circuit 20; Z12 is the reverse transmission impedance of the broadband equalization circuit 20; and Z21 is the forward transmission impedance of the broadband equalization circuit 20. These parameters reflect the impedance characteristics of the broadband equalization circuit 20, which are frequency-dependent.

[0077] After further incorporating the main resonator 10, the forward transmission impedance of the overall broadband equalization network is:

[0078]

[0079] Thus, the frequency-coupling curve is determined based on the forward transmission impedance Z(s); the frequency-coupling curve determined by the forward transmission impedance and the reverse transmission impedance of the network are close. Figure 3 This is a frequency-coupling curve related to the forward transmission impedance of a broadband balanced network provided in an embodiment of the present invention; see Figure 3 As shown, the broadband equalization network exhibits a monotonically decreasing frequency-coupling curve. Figure 4 This is a frequency-coupling degree curve of a bidirectional coupler body provided in an embodiment of the present invention; Figure 5 This is a frequency-coupling curve of a dual directional coupler after adding a broadband equalization network to both coupling ends of the bidirectional coupler body, as provided in this embodiment of the invention; Figure 4 As shown, the output of the bidirectional coupler is a monotonically increasing frequency-coupling curve; thus, through... Figure 3 The broadband equalization network in the circuit complements the coupling curve of the circuit without an equalization network, resulting in smaller fluctuations in the flatness of the coupling curve across the overall operating frequency range (see...). Figure 5 As shown, the dotted line curve represents the coupling degree curve at the forward coupling end; the segmented line curve represents the coupling degree curve at the reverse coupling end, thus increasing the bandwidth. For details, refer to... Figure 5 This improves the ratio of the highest to lowest frequency band in the overall broadband balanced network operating frequency band, meeting the requirements of low-frequency bands down to 8MHz and high-frequency bands exceeding 420MHz. It should be noted that... Figure 3 The lowest frequency in the frequency range is the resonant frequency of the main resonator 10, which is also the lowest operating frequency of the broadband equalization network.

[0080] It should also be noted that Z11 is the input impedance of the broadband equalization circuit 20; Z22 is the output impedance of the broadband equalization circuit 20. Figure 6 This invention provides a frequency-voltage standing wave ratio curve for determining the output impedance of a broadband equalization network. Figure 7 This is a frequency-voltage standing wave ratio (VSWR) curve of a dual directional coupler after adding a broadband equalization network to both coupling ends of the bidirectional coupler body; for example... Figure 7 As shown (the dotted line curve represents the frequency-voltage standing wave ratio curve at the forward coupling end, and the segmented line curve represents the frequency-voltage standing wave ratio curve at the reverse coupling end), this frequency-voltage standing wave ratio is the frequency-voltage standing wave ratio curve after adding a broadband equalization network. The voltage standing wave ratios in the figure are all less than 1.5, which is obviously better than the voltage standing wave ratio at the coupling end of the directional coupler in the existing bridge T RF equalization network technology.

[0081] Optionally, in another embodiment, Figure 8 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention, such as... Figure 8As shown, the first L-shaped branch equalization module 21 includes a first resistor R1, a first capacitor C1, a second resistor R2, and a second capacitor C2. One end of the first resistor R1 serves as the first terminal of the first L-shaped branch equalization module 21 and is electrically connected to the second terminal of the main resonator 10. The second terminal of the first resistor R1 is electrically connected to the first terminal of the first capacitor C1. The second terminal of the first capacitor C1 is electrically connected to the first terminal of the second resistor R2. The second terminal of the second resistor R2 is grounded. The second terminal of the first resistor R1 serves as the second terminal of the first L-shaped branch equalization module 21 and is electrically connected to the first terminal of the second L-shaped branch equalization module 22. The second capacitor C2 is connected in parallel with the second resistor R2. It can be understood that when the first L-shaped branch equalization module 21 is composed of the first resistor R1, the first capacitor C1, the second resistor R2, and the second capacitor C2, the broadband equalization network formed by it, the second L-shaped branch equalization modules 22, and the second L-shaped branch equalization module 23 can also complement the gain curve without an equalization network, thereby reducing the flatness fluctuation of the gain-frequency curve within the overall operating frequency and increasing the bandwidth.

[0082] Optionally, in another embodiment, Figure 9 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of another broadband equalization network provided in an embodiment of the present invention, such as... Figure 9-10The second L-shaped branch equalization module 22 includes a third resistor R3, a third capacitor C3, a fourth resistor R4, and a fourth capacitor C4. One end of the third resistor R5 serves as the first end of the second L-shaped branch equalization module 22 and is electrically connected to the second end of the first L-shaped branch equalization module 21. The second end of the third resistor R3 is electrically connected to the first end of the third capacitor C3. The second end of the third capacitor C3 is electrically connected to the first end of the fourth resistor. The second end of the fourth resistor R4 is grounded. The second end of the third resistor R3 serves as the second end of the second L-shaped branch equalization module 22 and is electrically connected to the second end of the third L-shaped branch equalization module 22. The fourth capacitor C4 is connected in parallel with the fourth resistor R5. It can be understood that when the second L-shaped branch equalization module 22 is composed of the third resistor R3, the third capacitor C3, the fourth resistor R4, and the fourth capacitor C4, the broadband equalization network formed by it, the first L-shaped branch equalization module 22, and the third L-shaped branch equalization module 23 can also complement the gain curve without an equalization network, thereby reducing the flatness fluctuation of the gain-frequency curve within the overall operating frequency and increasing the bandwidth. It is understandable that when the second L-type branch equalization module 22 is composed of the third resistor R3, the third capacitor C3, the fourth resistor R4 and the fourth capacitor C4, the first L-type branch equalization module 21 can also be composed of the first resistor R1, the first capacitor C1, the second resistor R2 and the second capacitor C2. The broadband equalization network thus formed can also complement the gain curve when no equalization network is added, thereby increasing the bandwidth.

[0083] Based on the same inventive concept, this invention also provides a unidirectional coupler. Figure 11 This is a schematic diagram of a unidirectional coupler provided in an embodiment of the present invention; as shown. Figure 11 As shown, the unidirectional coupler includes a unidirectional coupler body and a broadband equalization network 01 as described in the above embodiment. The unidirectional coupler body includes a main transmission channel AB and coupling channels C1A and D1. The broadband equalization network coupling 01 is connected to the coupling terminal CA1 of coupling channels C1A and D1, and D1 is connected to the matched load to ground. Since this embodiment includes the broadband equalization network described in the above embodiment, it also has the beneficial effects of the above embodiment, which will not be repeated here.

[0084] Based on the same inventive concept, this invention also provides a dual directional coupler. Figure 12 This is a schematic diagram of a dual directional coupler provided in an embodiment of the present invention; as shown. Figure 12As shown, the dual-directional coupler includes: a bidirectional coupler body and two broadband equalization networks as described in the above embodiments; the bidirectional coupler body includes a main transmission channel, coupling channels C1A and D1, and reverse coupling channels C2A and D2; the coupling end C1A of coupling channels C1A and D1 is centrally symmetrical about the main transmission channel AB and the reverse coupling end C2 of reverse coupling channels C2A and D2; one broadband equalization network is connected to the coupling end C1A of C1A and D1; the other broadband equalization network is coupled and connected to the coupling end C2A of the reverse coupling channels C2A and D2. Connecting one broadband equalization network to the coupling end C1A of C1A and D1 increases the bandwidth of the output signal at the coupling end; while connecting the other broadband equalization network to the coupling end C2A of the reverse coupling channels C2A and D2, with D1 and D2 connected to a matched load to ground, further increases the bandwidth of the output signal at the reverse coupling end.

[0085] Optional, Figure 13 This is a schematic diagram of the physical location structure of a bidirectional coupler body provided in an embodiment of the present invention, as shown below. Figure 13 As shown, the coupling channel and reverse coupling channel are arranged on the same layer; the coupling channel and the main transmission channel are arranged on different layers. By placing the coupling channel and reverse coupling channel on the same layer and the coupling channel and the main transmission channel on different layers of the PCB, good isolation is achieved, avoiding arcing under high power. This allows the directional coupler to be easily integrated with the broadband power amplifier onto a single PCB board, solving the output signal detection problem of the RF power amplifier, and is applicable to broadband RF power amplifiers for multi-core imaging magnetic resonance imaging.

[0086] Optional, continue to refer to Figure 13 The bidirectional coupler body also includes: a dielectric channel; the dielectric channel covers the upper surface of the main transmission channel; the projected area of ​​the dielectric channel on the plane of the coupling channel is the area between the coupling channel and the reverse coupling channel. Specifically, in the coupling interval between the main transmission channel and each coupling channel, a dielectric material is covered, with a dielectric constant between that of air and the PCB dielectric constant, reducing the phase velocity difference between odd and even modes of the broadband RF signal and improving directivity. Furthermore, the bidirectional coupler structure also includes a PCB bottom layer; the PCB bottom layer is ground and mounted on a metal heat sink; this allows for good heat dissipation, which can further increase power and achieve higher power output for the bidirectional coupler.

[0087] Figures 14-17 This is a field-path cooperative simulation result of a dual directional coupler from a broadband equalization network to the bidirectional coupler body provided in an embodiment of the present invention; such as... Figure 14-17As shown, in a bandwidth equalization network, the first resistor R1 is 36 ohms, the first capacitor C1 is 85pF, the second resistor R2 is 5 ohms, the third resistor R3 is 20 ohms, the third capacitor C3 is 220pF, the fourth resistor R4 is 8.2 ohms, the fifth resistor R5 is 50 ohms, the first inductor L1 is 1720nH, the series inductor L0 is 1720nH, and the series capacitor C0 is 250pF. The frequency-coupling curves at the forward coupling end (see dotted curve) and the frequency-coupling curves at the reverse coupling end (see...) can be obtained. Figure 14 Segment curve); frequency-directivity curve at the positive coupling end (see...) Figure 15 The dotted line curve in the middle), the frequency-directivity curve of the reverse coupling end (see...) Figure 15 (segment curves in the middle).

[0088] Insertion loss of the main transmission channel AB of the dual directional coupler (see...) Figure 16 (The curve in the middle), the frequency-voltage standing wave ratio curve at the positive coupling terminal (see...) Figure 17 The dotted line curve above), the frequency-voltage standing wave ratio curve at the reverse coupling terminal (see...) Figure 17 The frequency-voltage standing wave ratio (VSWR) curve of the main transmission channel AB within the bidirectional coupler body (see the segment curve in the figure) and the frequency-voltage standing wave ratio (VSWR) curve of the main transmission channel AB within the bidirectional coupler body (see the figure). Figure 17 (The curve below the dots)

[0089] Figures 18-21 This is a prototype test result of a unidirectional coupler from a broadband balanced network to the unidirectional coupler body provided in an embodiment of the present invention; such as... Figure 18-21 As shown, in the bandwidth equalization network, the first resistor R1 is 36 ohms, the first capacitor C1 is 85pF, the second resistor R2 is 4.99 ohms, the third resistor R3 is 20 ohms, the third capacitor C3 is 220pF, the fourth resistor R4 is 8.2 ohms, the fifth resistor R5 is 50 ohms, the first inductor L1 is 1720nH, the series inductor L0 is 1720nH (where the 1720nH inductor can be composed of two inductors in series, such as 900nH and 820nH), and the series capacitor C0 is 250pF. The frequency-coupling curve of the actual forward coupling terminal can be obtained (see...). Figure 18 Curve a) Frequency-isolation curve at the actual forward coupling end (see curve a) Figure 18 (b) The frequency-output return loss curve at the actual forward coupling end (see curve b) Figure 19 (Middle curve), the actual frequency-output return loss curve of the main transmission channel AB of the single directional coupler (see...) Figure 20 The curves in the figure), and the actual frequency-insertion loss curve of the main transmission channel AB of the unidirectional coupler (see ...). Figure 21 (the curve in the middle)

[0090] Figure 18-21Various parameters and Figure 14-17 The high degree of agreement among the parameters further verifies the feasibility of the invention. It also indicates optimization of the insertion loss of the main transmission channel AB within the directional coupler body.

[0091] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A broadband load balancing network, characterized in that, include: The main resonator and equalization circuit; the equalization circuit includes at least one first L-type branch equalization module, a second L-type branch equalization module, and a third L-type branch equalization module. The first end of the first L-shaped branch equalization module is electrically connected to the second end of the main resonator; the second end of the first L-shaped branch equalization module is electrically connected to the first end of the second L-shaped branch equalization module; the second end of the second L-shaped branch equalization module is electrically connected to the second end of the third branch L-shaped equalization module. The first end of the third branch L-shaped equalization module is electrically connected to the first end of the first main resonator; the first end of the main resonator is electrically connected to any coupling end of the coupling channel of the directional coupler.

2. The broadband load balancing network according to claim 1, characterized in that, The first L-shaped branch equalization module includes a first resistor, a first capacitor, and a second resistor; One end of the first resistor serves as the first end of the first L-shaped branch equalization module and is electrically connected to the second end of the first main resonator; the second end of the first resistor is electrically connected to the first end of the first capacitor; the second end of the first capacitor is electrically connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the second end of the first L-shaped branch equalization module and is electrically connected to the first end of the second L-shaped branch equalization module.

3. The broadband load balancing network according to claim 1, characterized in that, The first L-shaped branch equalization module includes a first resistor, a first capacitor, a second resistor, and a second capacitor; One end of the first resistor serves as the first end of the first L-shaped branch equalization module and is electrically connected to the second end of the first main resonator; the second end of the first resistor is electrically connected to the first end of the first capacitor; the second end of the first capacitor is electrically connected to the first end of the second resistor; the second end of the second resistor is grounded; the second end of the first resistor serves as the second end of the first L-shaped branch equalization module and is electrically connected to the first end of the second L-shaped branch equalization module; the second capacitor and the second resistor are connected in parallel.

4. The broadband load balancing network according to claim 1, characterized in that, The second L-shaped branch equalization module includes a third resistor, a third capacitor, and a fourth resistor; One end of the third resistor serves as the first end of the second L-shaped branch equalization module and is electrically connected to the second end of the first L-shaped branch equalization module; the second end of the third resistor is electrically connected to the first end of the third capacitor; the second end of the third capacitor is electrically connected to the first end of the fourth resistor; the second end of the fourth resistor is grounded; the second end of the third resistor serves as the second end of the second L-shaped branch equalization module and is electrically connected to the second end of the third L-shaped branch equalization module.

5. The broadband load balancing network according to claim 1, characterized in that, The second L-shaped branch equalization module includes a third resistor, a third capacitor, a fourth resistor, and a fourth capacitor; One end of the third resistor serves as the first end of the second L-shaped branch equalization module and is electrically connected to the second end of the first L-shaped branch equalization module; the second end of the third resistor is electrically connected to the first end of the third capacitor; the second end of the third capacitor is electrically connected to the first end of the fourth resistor; the second end of the fourth resistor is grounded; the second end of the third resistor serves as the second end of the second L-shaped branch equalization module and is electrically connected to the second end of the third L-shaped branch equalization module; the fourth capacitor and the fourth resistor are connected in parallel.

6. The broadband load balancing network according to claim 1, characterized in that, The third L-shaped branch equalization module includes a fifth resistor and a first inductor; The first end of the fifth resistor serves as the second end of the third L-shaped branch equalization module and is electrically connected to the second end of the second L-shaped branch equalization module; the second end of the fifth resistor is electrically connected to the first end of the first main resonator; the first end of the fifth resistor is electrically connected to the first end of the first inductor; and the second end of the first inductor is grounded.

7. The broadband equalization network according to claim 1, characterized in that, The main resonator includes a series inductor and a series capacitor; the series inductor and the series capacitor are connected in series. Alternatively, the main resonator may include a parallel inductor and a parallel capacitor; the parallel inductor and the parallel capacitor may be connected in parallel.

8. A unidirectional coupler, characterized in that, include: The unidirectional coupler body and the broadband equalization network according to any one of claims 1-7; The unidirectional coupler body includes a main transmission channel and a coupling channel; the broadband equalization network is connected to the coupling end of the coupling channel.

9. A dual directional coupler, characterized in that, include: The bidirectional coupler body and two broadband equalization networks as described in any one of claims 1-7 above; The bidirectional coupler body includes a main transmission channel, a coupling channel, and a reverse coupling channel; the coupling end of the coupling channel is symmetrical with respect to the main transmission channel and the reverse coupling end of the reverse coupling channel. One of the broadband equalization networks is coupled to the coupling end of the coupling channel; the other broadband equalization network is coupled to the coupling end of the reverse coupling channel.

10. The dual directional coupler according to claim 9, characterized in that, The coupling channel and the reverse coupling channel are arranged on the same layer; The coupling channel is configured on a different layer than the main transmission channel.

11. The dual directional coupler according to claim 10, characterized in that, Also includes: Medium channel; The medium channel covers the upper surface of the main transmission channel; The projected area of ​​the medium channel on the plane where the coupling channel is located is the area between the coupling channel and the reverse coupling channel.

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