Directional coupler and radio frequency front-end module
By introducing adjustment branches and control circuits into the directional coupler, the coupling degree in the high-frequency band is adjusted, which solves the problem of poor flatness caused by the change of coupling degree with frequency. This achieves flattening of coupling degree and improvement of ESD performance in a wide frequency band.
Patent Information
- Application Number
- CN202520518120.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2035-03-24
AI Technical Summary
Existing directional couplers exhibit increased coupling as the RF signal frequency increases, resulting in poor coupling flatness.
By introducing an adjustment branch into the directional coupler and setting a switch on the adjustment branch, the control circuit controls the switch to be in the off state, which is equivalent to a capacitor, thereby adjusting the coupling degree in the high-frequency band and suppressing high-frequency coupling. Combined with impedance matching circuit, signal transmission is optimized.
The coupling flatness is improved over a wide frequency range, enhancing the coupling flatness and ESD performance of the directional coupler.
Smart Images
Figure CN223898592U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of radio frequency technology, and in particular to a directional coupler and a radio frequency front-end module. Background Technology
[0002] A directional coupler is an important microwave / millimeter-wave component that can distribute the power of radio frequency signals in a certain proportion for signal isolation, separation, and mixing. Figure 1 A typical structure and signal flow diagram of a directional coupler are shown, such as... Figure 1 As shown, a directional coupler consists of two transmission lines: a main transmission line and a coupling line. Power coupling between these two transmission lines is achieved through a specific coupling mechanism (such as a gap, aperture, or coupling segment). Due to the design of this coupling mechanism, power in the coupling line is only transmitted to one output port, while the other port receives no power output.
[0003] like Figure 1 As shown, in the directional coupler, the signal power at input terminal 1 of the main transmission line is P1, the signal power at the through terminal 2 of the main transmission line is P2, the signal power at coupling terminal 3 of the coupling line is P3, and the signal power at isolation terminal 4 of the coupling line is P4. The main technical specifications of the directional coupler are:
[0004] Insertion loss IL = 10 * log(P1 / P2) = -20 * log(|S21|), which represents the energy loss of the signal when it passes through the directional coupler;
[0005] Isolation I = 10 * log(P1 / P4) = -20 * log(|S41|), which represents the degree of signal isolation between the main transmission line and the coupling line;
[0006] Coupling strength CP = 10 * log(P1 / P3) = -20 * log(|S31|), representing the signal coupling strength from the main transmission line to the coupling line;
[0007] And the directionality D = 10 * log (P3 / P4) = 20 * log (|S31| / |S41|), represents the distribution of the input signal between different ports.
[0008] It is understandable that a coupled-line directional coupler essentially transmits signals between two transmission lines via a coupling capacitor. The capacitive reactance Xc = 1 / (2πfC), where f is the frequency of the radio frequency signal and C is the capacitance value. As the radio frequency signal frequency f increases, the capacitive reactance Xc decreases, thus increasing the coupling degree CP of the directional coupler. This results in the following curve showing the change in coupling degree CP of the directional coupler with the radio frequency signal f: Figure 2As shown, as the RF signal frequency f increases from 1 GHz to 4 GHz, that is, within the bandwidth range of 1 GHz to 4 GHz, the coupling degree CP of the directional coupler increases from -28.3332 dB to -14.4752 dB, an increase of 13.8 dB. This results in poor coupling flatness of the directional coupler (reflecting the stability of the coupling degree CP within the frequency band).
[0009] Therefore, it can be seen that existing directional couplers have the problem that as the frequency of the radio frequency signal increases, the coupling degree also increases, resulting in poor coupling flatness. Utility Model Content
[0010] To address the aforementioned technical problems, this application provides a directional coupler and an RF front-end module to improve the coupling flatness of the directional coupler.
[0011] To achieve the above objectives, the embodiments of this application provide the following technical solutions:
[0012] In a first aspect, embodiments of this application provide a directional coupler, including:
[0013] A main transmission line is used to transmit radio frequency signals, and the main transmission line includes an input end and a through end;
[0014] A coupling line, coupled to the main transmission line, is used to generate a coupling signal based on the radio frequency signal. The coupling line includes a first end and a second end, one of which is an isolation end and the other is a coupling end.
[0015] An adjusting branch is provided, one end of which is electrically connected to the coupling end of the coupling line, and the other end of which is grounded. At least one first switch is provided on the adjusting branch.
[0016] A control circuit is used to control at least a portion of the first switch on the regulating branch to be in the off state.
[0017] Optionally, the directional coupler has a coupling signal output terminal, and the coupling end of the coupling line is connected to the coupling signal output terminal;
[0018] The isolation end of the coupling line is also grounded through a first impedance matching circuit.
[0019] Optionally, the directional coupler has a coupling signal output terminal, and the coupling end of the coupling line is electrically connected to the coupling signal output terminal through a second switch;
[0020] The isolation end of the coupling line is also grounded through a third switch and a second impedance matching circuit connected in series.
[0021] The regulating branch is directly connected to the coupling end of the coupling line, or one end of the regulating branch is connected to the coupling signal output end and electrically connected to the coupling end of the coupling line through the second switch, and the other end of the regulating branch is grounded;
[0022] When the control circuit controls both the second switch and the third switch to be in the closed state, the coupling signal is output at the coupling signal output terminal.
[0023] Optionally, the directional coupler has a coupling signal output terminal;
[0024] The first and second ends of the coupling line are each connected to an adjustment branch.
[0025] The first end of the coupling line is also electrically connected to the coupling signal output terminal via a fourth switch, and the second end of the coupling line is also electrically connected to the coupling signal output terminal via a fifth switch;
[0026] The first end of the coupling line is also grounded through a sixth switch and a third impedance matching circuit connected in series, and the second end of the coupling line is also grounded through a seventh switch and a fourth impedance matching circuit connected in series.
[0027] When the first end of the coupling line is an isolation end and the second end is a coupling end, the control circuit controls the fourth switch to be in the off state, the fifth switch to be in the closed state, the sixth switch to be in the closed state, and the seventh switch to be in the off state.
[0028] When the second end of the coupling line is the isolation end and the first end is the coupling end, the control circuit controls the fourth switch to be in the closed state, the fifth switch to be in the off state, the sixth switch to be in the off state, and the seventh switch to be in the closed state.
[0029] Optionally, the regulating branch is provided with a first switch, and the first switch is controlled by the control circuit to be in the off state.
[0030] Optionally, at least two of the first switches are provided on the regulating branch, and at least some of the first switches on the regulating branch are controlled by the control circuit to be in the off state.
[0031] Optionally, when the directional coupler operates in the first frequency band range, on the adjustment branch connected to the coupling end of the coupling line, M of the first switches are controlled by the control circuit to be in the off state, and the other first switches are in the closed state.
[0032] When the directional coupler operates in the second frequency band range, the second frequency band range does not overlap with the first frequency band range at least partially. On the adjustment branch connected to the coupling end of the coupling line, N first switches are controlled by the control circuit to be in the off state, and the other first switches are in the closed state, N≠M.
[0033] Optionally, the third impedance matching circuit includes a first resistor and a first capacitor connected in parallel, and one common terminal of the first resistor and the first capacitor connected in parallel is connected to the first end of the coupling line through the sixth switch, and the other common terminal is grounded.
[0034] Optionally, the fourth impedance matching circuit includes a second resistor and a second capacitor connected in parallel, and one common terminal of the second resistor and the second capacitor connected in parallel is connected to the second terminal of the coupling line through the seventh switch, and the other common terminal is grounded.
[0035] Secondly, embodiments of this application provide a radio frequency front-end module, including any of the aforementioned directional couplers.
[0036] Compared with existing technologies, the above technical solution has the following advantages:
[0037] The directional coupler provided in this application embodiment includes a main transmission line and a coupling line. The main transmission line is used to transmit radio frequency signals and includes an input terminal and a through terminal. The coupling line is coupled to the main transmission line and is used to generate a coupling signal based on the radio frequency signal transmitted by the main transmission line. The coupling line includes a first terminal and a second terminal, one of which is an isolation terminal and the other is a coupling terminal. By setting an adjustment branch, one end of the adjustment branch is electrically connected to the coupling terminal of the coupling line, and the other end is grounded. At least one first switch is provided on the adjustment branch, and a control circuit is used to control at least some of the first switches on the adjustment branch to be in an off state. Thus, the coupling terminal of the adjustment branch connected to the coupling line is electrically connected and in an off state. The first switch in the off state is equivalent to a capacitor. The capacitance equivalent to the first switch in the off state has a larger capacitive reactance in the low-frequency range and a smaller capacitive reactance in the high-frequency range. Since the coupling capacitance between the main transmission line and the coupling line in the directional coupler also has a larger capacitive reactance in the low-frequency range and a smaller capacitive reactance in the high-frequency range, the capacitance equivalent to the first switch in the off state has a greater impact in the high-frequency range. This is equivalent to increasing the capacitive reactance at the coupling end of the coupling line in the high-frequency range, which has a suppressive effect on high-frequency coupling. Therefore, the coupling degree of the directional coupler is reduced in the high-frequency range, thus reducing the coupling degree difference of the directional coupler over a wide frequency range and making the coupling degree curve flatter, i.e., improving the coupling flatness of the directional coupler. Simultaneously, the regulating branch can also serve as an ESD release path, which is beneficial to improving the ESD performance of the directional coupler.
[0038] Other objects and advantages of this application will be described in detail in conjunction with the accompanying drawings in the following embodiments. Attached Figure Description
[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0040] Figure 1 This is a schematic diagram of a typical structure and signal flow of a directional coupler;
[0041] Figure 2 The graph shows the coupling degree of an existing directional coupler as a function of the radio frequency signal frequency.
[0042] Figure 3 This is a schematic diagram of the circuit structure of a directional coupler provided in an embodiment of this application;
[0043] Figure 4 The first switch, which is in the off state, is equivalent to the curve of the degree of coupling with the frequency of the radio frequency signal with different capacitance values, where the first switch is not electrically connected to the coupling end of the coupling line of the directional coupler and is electrically connected to the coupling end of the coupling line of the directional coupler.
[0044] Figure 5 This is a schematic diagram of the circuit structure of another directional coupler provided in an embodiment of this application;
[0045] Figure 6 This is a schematic diagram of the circuit structure of another directional coupler provided in an embodiment of this application;
[0046] Figure 7 This is a schematic diagram of the circuit structure of another directional coupler provided in the embodiments of this application;
[0047] Figure 8 This is a schematic diagram of the circuit structure of another directional coupler provided in an embodiment of this application.
[0048] Figure label:
[0049] 10-Main transmission line; 11-Input terminal; 12-Straight-through terminal; 20-Coupled line; 21-First terminal; 22-Second terminal; 30-Regulating branch; 40-Control circuit; S1-First switch; S2-Second switch; S3-Third switch; S4-Fourth switch; S5-Fifth switch; S6-Sixth switch; S7-Seventh switch; R1-First resistor; C1-First capacitor; R2-Second resistor; C2-Second capacitor; OUT-Coupled signal output terminal; 51-First impedance matching circuit; 52-Second impedance matching circuit; 53-Third impedance matching circuit; 54-Fourth impedance matching circuit. Detailed Implementation
[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0051] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.
[0052] As described in the background section, existing directional couplers suffer from a problem where the coupling degree increases with the increase of the radio frequency signal frequency, resulting in poor coupling flatness. Specifically, for example... Figure 2 As shown, the directional coupler has a coupling of -28.3332dB when the radio frequency signal is 1.0GHz, and a coupling of -14.4752dB when the radio frequency signal is 4.0GHz. In the 3GHz range from 1.0GHz to 4.0GHz, the coupling increases by 13.86dB, which is equivalent to the coupling CP increasing at a rate of 4.61933ndB / Hz with the increase of the radio frequency signal frequency f.
[0053] In view of this, embodiments of this application provide a directional coupler. Figure 3 A schematic diagram of the circuit structure of a directional coupler provided in an embodiment of this application is shown, as follows: Figure 3As shown, the directional coupler includes a main transmission line 10 and a coupling line 20. The main transmission line 10 is used to transmit radio frequency signals and includes an input terminal 11 and a through terminal 12. The coupling line 20 is coupled to the main transmission line 10 and is used to generate a coupling signal according to the radio frequency signal. The coupling line 20 includes a first end 21 and a second end 22. One of the first end 21 and the second end 22 of the coupling line 20 is an isolation end and the other is a coupling end. That is, the first end 21 of the coupling line 20 is an isolation end and the second end 22 is a coupling end, or the first end 21 of the coupling line 20 is a coupling end and the second end 22 is an isolation end.
[0054] like Figure 3 As shown, the directional coupler also includes an adjustment branch 30, one end of which is electrically connected to the coupling end of the coupling line 20, and the other end of which is grounded. At least one first switch S1 is provided on the adjustment branch 30.
[0055] like Figure 3 As shown, the directional coupler also includes a control circuit 40, which controls at least a portion of the first switch S1 on the regulating branch 30 to be in the off state.
[0056] Therefore, it can be understood that the first switch S1 on the regulating branch 30, which is electrically connected to the coupling end of the coupling line 20 and is in the off state, is equivalent to a capacitor. The capacitor equivalent to the first switch S1 in the off state has a large capacitive reactance in the low frequency range and a small capacitive reactance in the high frequency range.
[0057] Furthermore, as is known from the background section, a coupled-line type directional coupler is essentially two transmission lines that transmit signals through a coupling capacitor. Its capacitive reactance Xc = 1 / (2πfC), where f is the frequency of the radio frequency signal and C is the capacitance value. Therefore, it can be seen that the coupling capacitance between the main transmission line 10 and the coupling line 20 in the directional coupler is larger in the low-frequency range and smaller in the high-frequency range.
[0058] Therefore, the equivalent capacitance of the first switch S1 in the off state has a greater impact in the high-frequency band, effectively increasing the capacitive reactance of the coupling end of the coupling line 20 in the high-frequency band. This suppresses coupling in the high-frequency band, thereby reducing the coupling degree of the directional coupler in the high-frequency band. This reduces the coupling degree difference of the directional coupler over a wide frequency range, making the coupling degree curve flatter, thus improving the coupling flatness of the directional coupler. Simultaneously, the regulating branch 30 can also serve as an ESD release path, which is beneficial for improving the ESD performance of the directional coupler.
[0059] Figure 3The example shown is based on the first end 21 of the coupling line 20 being the isolation end and the second end 22 being the coupling end. It can be understood that the second end 22 of the coupling line 20 can also be the isolation end and the first end 21 is the coupling end. The situation is similar and will not be elaborated further.
[0060] Figure 4 The diagram shows the curves of the coupling degree CP versus the radio frequency signal frequency f with different capacitive reactance values. The first switch S1 on the first switch S1 is shown to be in the off state, with the first switch S1 on the first switch S1 not electrically connected to the first switch S1 at the coupling end of the coupling line 20 of the directional coupler, and the first switch S1 electrically connected to the first switch S1 at the coupling end of the coupling line 20 of the directional coupler. Figure 4 The topmost curve represents the change in coupling degree CP of the directional coupler's coupling line 20 (without electrical connection to the regulating branch 30) as a function of the radio frequency signal frequency f. Figure 4 The other five curves are curves showing the change in coupling degree CP of the regulating branch 30 electrically connected to the coupling end of the coupling line 20 of the directional coupler as a function of the radio frequency signal frequency f. Furthermore, from top to bottom, the overall equivalent capacitive reactance of the first switch S1 in the off state on the regulating branch 30 gradually increases. Figure 4 It can be seen that the overall equivalent capacitive reactance of the first switch S1 in the off state on the regulating branch 30, which is electrically connected to the coupling end of the coupling line 20, has a suppressive effect on the coupling of the high-frequency band, making the coupling curve tend to flatten. Moreover, the larger the overall equivalent capacitive reactance of the first switch S1 in the off state on the regulating branch 30, the flatter the coupling curve becomes.
[0061] For example, such as Figure 4 As shown by the bottom curve, the coupling of the directional coupler is -30.3116dB when the RF signal is 1.0GHz, corresponding to coordinate point M1: (1.0GHz, -30.3116dB); when the RF signal is 4.0GHz, its coupling is -30.0493dB, corresponding to coordinate point M2: (4.0GHz, 30.0493dB); the highest point of this curve is coordinate point M3: (2.2GHz, -27.5049dB), corresponding to an RF signal of 2.2GHz and a coupling of -27.5049dB. It can be seen that within a wide frequency range (1.0GHz-4.0GHz), the difference in coupling is very small, and the coupling curve tends to flatten out.
[0062] Optionally, in some embodiments of this application, one of the first end 21 and the second end 22 of the coupling line 20 may be fixed as an isolation end and the other as a coupling end, for example, as Figure 3 As shown, the first end 21 of the fixed coupling line 20 is the isolation end, and the second end 22 is the coupling end. In this case, it is optional, as follows: Figure 3As shown, the directional coupler has a coupling signal output terminal OUT. The coupling terminal (such as the second terminal 22) of the coupling line 20 is connected to the coupling signal output terminal OUT. At the same time, the isolation terminal (such as the first terminal 21) of the coupling line 20 is also grounded through the first impedance matching circuit 51.
[0063] It is understandable that the isolation terminal of the coupling line 20 theoretically has no power output. The isolation terminal of the coupling line 20 is grounded through the first impedance matching circuit 51. Thus, the first impedance matching circuit 51 of the isolation terminal of the coupling line 20 can ensure that the impedance of the isolation port matches the impedance of the transmission line, reduce the generation of reflected signals, improve the transmission efficiency of the coupled signal, and enable more coupled signals to be transmitted from the coupling terminal of the coupling line 20 to the coupled signal output terminal OUT.
[0064] Optional, such as Figure 3 As shown, the first impedance matching circuit 51 includes a resistor R01 and a capacitor C01 connected in parallel, and one common terminal of the resistor R01 and capacitor C01 connected in parallel is connected to the isolation terminal of the coupling line 20, and the other common terminal is grounded.
[0065] When one of the first end 21 and the second end 22 of the fixed coupling line 20 is an isolation end and the other is a coupling end, another option is, such as Figure 5 As shown, Figure 5 A schematic diagram of the circuit structure of another directional coupler provided in an embodiment of this application is shown, wherein, Figure 5 Taking the first end 21 of the directional coupling line 20 as the isolation end and the second end 22 as the coupling end as an example, it can be seen that the directional coupler has a coupling signal output end OUT. The coupling end of the coupling line 20 is electrically connected to the coupling signal output end OUT through the second switch S2; the isolation end of the coupling line 20 is also grounded through the third switch S3 connected in series and the second impedance matching circuit 52. When the control circuit 40 controls both the second switch S2 and the third switch S3 to be in the closed state, the coupling signal output end OUT outputs the coupling signal.
[0066] In this embodiment, as Figure 5 As shown, the regulating branch 30 can be directly connected to the coupling end of the coupling line 20, or, as... Figure 6 As shown, Figure 6 This paper shows a schematic diagram of the circuit structure of another directional coupler provided in an embodiment of the present application. Figure 6Taking the first end 21 of the fixed coupling line 20 as the isolation end and the second end 22 as the coupling end as an example, one end of the adjustment branch 30 is connected to the coupling signal output terminal OUT, and is electrically connected to the coupling end of the coupling line 20 through the second switch S2. The other end of the adjustment branch 30 is grounded. That is to say, the adjustment branch 30 can be connected between the second switch S2 and the coupling end of the coupling line 20, or between the second switch S2 and the coupling signal output terminal OUT. Since the coupling signal output terminal OUT outputs a coupling signal when the control circuit 40 controls both the second switch S2 and the third switch S3 to be in the closed state, connecting the adjustment branch 30 between the second switch S2 and the coupling end of the coupling line 20, or connecting the adjustment branch 30 between the second switch S2 and the coupling signal output terminal OUT, is essentially the same when the second switch S2 is in the closed state.
[0067] In this embodiment, when the third switch S3 is closed, the isolation end of the coupling line 20 is grounded through the second impedance matching circuit 52. Thus, the second impedance matching circuit 52 at the isolation end of the coupling line 20 can ensure that the impedance of the isolation port matches the impedance of the transmission line, reduce the generation of reflected signals, improve the transmission efficiency of the coupled signal, and enable more coupled signals to be transmitted from the coupling end of the coupling line 20 to the coupled signal output end.
[0068] Optional, such as Figure 5 and Figure 6 As shown, the second impedance matching circuit 52 includes a resistor R02 and a capacitor C02 connected in parallel. One common terminal of the resistor R02 and the capacitor C02 is connected to the isolation terminal of the coupling line 20 through the third switch S3, and the other common terminal is grounded.
[0069] Optionally, in some embodiments of this application, such as Figure 7 As shown, Figure 7 The diagram shows a circuit structure of another directional coupler provided in the embodiment of this application. The isolation end and the coupling end of the coupling line 20 are interchangeable. That is, the first end 21 of the coupling line 20 is the isolation end and the second end 22 is the coupling end. This can be switched between the first end 21 of the coupling line 20 being the coupling end and the second end 22 being the isolation end.
[0070] Specifically, such as Figure 7As shown, the directional coupler has a coupling signal output terminal OUT; the first end 21 and the second end 22 of the coupling line 20 are each connected to an adjustment branch 30, that is, the first end 21 and the second end 22 of the coupling line 20 are each grounded through an adjustment branch 30, and at least one first switch S1 is provided on each adjustment branch 30; the first end 21 of the coupling line 20 is also electrically connected to the coupling signal output terminal OUT through a fourth switch S4, and the second end 22 of the coupling line 20 is also electrically connected to the coupling signal output terminal OUT through a fifth switch S5; the first end 21 of the coupling line 20 is also grounded through a sixth switch S6 connected in series and a third impedance matching circuit 53, and the second end 22 of the coupling line 20 is also grounded through a seventh switch S7 connected in series and a fourth impedance matching circuit 54.
[0071] With this configuration, when the first end 21 of the coupling line 20 needs to be the isolation end and the second end 22 the coupling end, the control circuit 40 controls the fourth switch S4 to be in the off state, the fifth switch S5 to be in the closed state, the sixth switch S6 to be in the closed state, and the seventh switch S7 to be in the off state. At this time, the first end 21 (i.e., the isolation end) of the coupling line 20 is grounded through the closed sixth switch S6 and the third impedance matching circuit 53, and the second end 22 (i.e., the coupling end) of the coupling line 20 is electrically connected to the coupling signal output terminal OUT through the closed fifth switch S5. Furthermore, the first end 21 of the coupling line 20 is grounded because the fourth switch S4 is in the off state. When the coupling line 20 is disconnected from the output terminal OUT, the regulating branch 30 connected to the first end 21 of the coupling line 20 is inactive because the first end 21 of the coupling line 20 is an isolation terminal. The fourth impedance matching circuit 54 connected to the second end 22 (i.e. the coupling terminal) of the coupling line 20 is inactive because the seventh switch S7 is in the off state. The first switch S1 on the regulating branch 30 connected to the second end 22 (i.e. the coupling terminal) of the coupling line 20, which is in the off state, is equivalent to adding the equivalent capacitive reactance of the high-frequency band at the coupling terminal of the coupling line 20, which suppresses the coupling of the high-frequency band and makes the coupling curve tend to flatten in the wide frequency range.
[0072] Similarly, when the second end 22 of the coupling line 20 is the isolation end and the first end 21 is the coupling end, the control circuit 40 controls the fourth switch S4 to be closed, the fifth switch S5 to be closed, the sixth switch S6 to be closed, and the seventh switch S7 to be closed. At this time, the second end 22 (i.e., the isolation end) of the coupling line 20 is grounded through the closed seventh switch S7 and the fourth impedance matching circuit 54, and the first end 21 (i.e., the coupling end) of the coupling line 20 is electrically connected to the coupling signal output terminal OUT through the closed fourth switch S4. Furthermore, the second end 22 (isolation end) of the coupling line 20 is grounded because the fifth switch S5 is closed. When the coupling line is in the off state and disconnected from the output terminal OUT of the coupling signal, the adjustment branch 30 connected to the second end 22 of the coupling line 20 is inactive because the second end 22 of the coupling line 20 is an isolation terminal. The third impedance matching circuit 53 electrically connected to the first end 21 (i.e. the coupling terminal) of the coupling line 20 is inactive because the sixth switch S6 is in the off state. The first switch S1 on the adjustment branch 30 connected to the first end 21 (i.e. the coupling terminal) of the coupling line 20, which is in the off state, is equivalent to adding the equivalent capacitive reactance of the high-frequency band at the coupling terminal of the coupling line 20, which suppresses the coupling of the high-frequency band and makes the coupling curve tend to flatten in the wide frequency range.
[0073] Based on any of the above embodiments, optionally, in some embodiments of this application, such as Figure 3 , Figures 5-7 As shown, a first switch S1 is provided on the regulating branch 30, and the first switch S1 is controlled by the control circuit 40 to be in the off state.
[0074] It should be noted that when a first switch S1 is installed on the regulating branch 30, refer to Figure 4 As shown, the appropriate equivalent capacitive reactance value of the first switch S1 in the off state on the regulating branch 30 connected to the coupling end of the coupling line 20 can be found through simulation over the entire broadband range, so that the coupling flatness is optimal. Then, the area of the first switch S1 required on the regulating branch 30 connected to the coupling end of the coupling line 20 can be calculated based on this appropriate equivalent capacitive reactance value. In other words, the area of the first switch S1 on the regulating branch 30 connected to the coupling end of the coupling line 20 can be designed so that the first switch S1 in the off state on the regulating branch 30 connected to the coupling end of the coupling line 20 is equivalent to an appropriate capacitive reactance value, thereby achieving optimal coupling flatness.
[0075] Furthermore, it can be known that the larger the area of the first switch S1, the larger the equivalent capacitance and the smaller the equivalent capacitive reactance of the first switch S1 in the off state. Conversely, the smaller the area of the first switch S1, the smaller the equivalent capacitance and the larger the equivalent capacitive reactance of the first switch S1 in the off state.
[0076] Optionally, in other embodiments of this application, such as Figure 8 As shown, Figure 8 A schematic diagram of the circuit structure of another directional coupler provided in an embodiment of this application is shown. It can be seen that at least two first switches S1 are provided on the regulating branch 30, and at least a portion of the first switches S1 on the regulating branch 30 are controlled by the control circuit 40 to be in the off state. Therefore, the control circuit 40 can select an appropriate number of first switches S1 on the regulating branch 30 connected to the coupling end of the coupling line 20 to be in the off state according to the frequency range of the directional coupler's operation, thereby increasing the equivalent capacitive reactance value at the coupling end of the coupling line 20, thus achieving optimal coupling flatness.
[0077] It can be known that the more first switches S1 in the off state that are connected to the regulating branch 30 at the coupling end of the coupling line 20, the smaller the total equivalent capacitance value and the larger the total equivalent capacitive reactance value at the coupling end of the coupling line 20. Conversely, the fewer first switches S1 in the off state that are connected to the coupling branch 30, the larger the total equivalent capacitance value and the smaller the total equivalent capacitive reactance value at the coupling end of the coupling line 20.
[0078] Understandably, this application selects an appropriate number of first switches S1 on the regulating branch 30 connected to the coupling end of the coupling line 20 to be in the off state, based on the frequency range of the directional coupler's operation, thereby achieving adjustable in-band coupling and frequency band extension of the coupling. Furthermore, in high-power applications, setting at least two first switches S1 on the regulating branch 30 can also protect the first switches S1.
[0079] Further optional, in some embodiments of this application, when the directional coupler is operating in the first frequency band range, on the adjustment branch 30 connected to the coupling end of the coupling line 20, M first switches S1 are controlled by the control circuit 40 to be in the off state, and the other first switches S1 are in the closed state.
[0080] When the directional coupler operates in the second frequency band range, the second frequency band range does not overlap with the first frequency band range at least partially. On the adjustment branch connected to the coupling end of the coupling line 20, N first switches S1 are controlled by the control circuit 40 to be in the off state, and the other first switches are in the closed state, N≠M.
[0081] Therefore, the control circuit 40 can select an appropriate number of first switches S1 on the adjustment branch 30 connected to the coupling end of the coupling line 20 to be in the off state according to the frequency range of the directional coupler, so as to increase the appropriate equivalent capacitive reactance value at the coupling end of the coupling line 20, thereby making the coupling flatness optimal.
[0082] It should be noted that the control circuit 40 can control the number of first switches S1 in the off state of the adjustment branch 30 connected by the same end of the coupling line 20 as the coupling end to be different in different frequency bands. It can also control the number of first switches S1 in the off state of the adjustment branch 30 connected by the first end 21 and the second end 22 of the coupling line 20 as the coupling ends to be different in different frequency bands, depending on the specific situation.
[0083] Optional, such as Figure 7 and Figure 8 As shown, the third impedance matching circuit 53 includes a first resistor R1 and a first capacitor C1 connected in parallel. One common terminal of the first resistor R1 and the first capacitor C1 connected in parallel is connected to the first terminal 21 of the coupling line 20 through the sixth switch S6, and the other common terminal is grounded.
[0084] Optional, such as Figure 7 and Figure 8 As shown, the fourth impedance matching circuit 54 includes a second resistor R2 and a second capacitor C2 connected in parallel. One common terminal of the second resistor R2 and the second capacitor C2 connected in parallel is connected to the second terminal 22 of the coupling line 20 through the seventh switch S7, and the other common terminal is grounded.
[0085] Accordingly, this application also provides a radio frequency front-end module, including the directional coupler provided in any of the above embodiments. Since the directional coupler has been described in detail in the foregoing embodiments, it will not be repeated here.
[0086] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.
[0087] The features described above regarding the disclosed embodiments can be substituted or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A directional coupler, characterized in that, include: A main transmission line is used to transmit radio frequency signals, and the main transmission line includes an input end and a through end; A coupling line, coupled to the main transmission line, is used to generate a coupling signal based on the radio frequency signal. The coupling line includes a first end and a second end, one of which is an isolation end and the other is a coupling end. An adjusting branch is provided, one end of which is electrically connected to the coupling end of the coupling line, and the other end of which is grounded. At least one first switch is provided on the adjusting branch. A control circuit is used to control at least a portion of the first switch on the regulating branch to be in the off state.
2. The directional coupler according to claim 1, characterized in that, The directional coupler has a coupling signal output terminal, and the coupling end of the coupling line is connected to the coupling signal output terminal; The isolation end of the coupling line is also grounded through a first impedance matching circuit.
3. The directional coupler according to claim 1, characterized in that, The directional coupler has a coupling signal output terminal, and the coupling end of the coupling line is electrically connected to the coupling signal output terminal through a second switch; The isolation end of the coupling line is also grounded through a third switch and a second impedance matching circuit connected in series. The regulating branch is directly connected to the coupling end of the coupling line, or one end of the regulating branch is connected to the coupling signal output end and electrically connected to the coupling end of the coupling line through the second switch, and the other end of the regulating branch is grounded; When the control circuit controls both the second switch and the third switch to be in the closed state, the coupling signal is output at the coupling signal output terminal.
4. The directional coupler according to claim 1, characterized in that, The directional coupler has a coupling signal output terminal; The first and second ends of the coupling line are each connected to an adjustment branch. The first end of the coupling line is also electrically connected to the coupling signal output terminal via a fourth switch, and the second end of the coupling line is also electrically connected to the coupling signal output terminal via a fifth switch; The first end of the coupling line is also grounded through a sixth switch and a third impedance matching circuit connected in series, and the second end of the coupling line is also grounded through a seventh switch and a fourth impedance matching circuit connected in series. When the first end of the coupling line is an isolation end and the second end is a coupling end, the control circuit controls the fourth switch to be in the off state, the fifth switch to be in the closed state, the sixth switch to be in the closed state, and the seventh switch to be in the off state. When the second end of the coupling line is the isolation end and the first end is the coupling end, the control circuit controls the fourth switch to be in the closed state, the fifth switch to be in the off state, the sixth switch to be in the off state, and the seventh switch to be in the closed state.
5. The directional coupler according to any one of claims 1-4, characterized in that, The regulating branch is provided with a first switch, and the first switch is controlled by the control circuit to be in the off state.
6. The directional coupler according to any one of claims 1-4, characterized in that, At least two of the first switches are provided on the regulating branch, and at least some of the first switches on the regulating branch are controlled by the control circuit to be in the off state.
7. The directional coupler according to claim 6, characterized in that, When the directional coupler operates in the first frequency band, on the adjustment branch connected to the coupling end of the coupling line, M of the first switches are controlled by the control circuit to be in the off state, and the other first switches are in the closed state. When the directional coupler operates in the second frequency band range, the second frequency band range does not overlap with the first frequency band range at least partially. On the adjustment branch connected to the coupling end of the coupling line, N first switches are controlled by the control circuit to be in the off state, and the other first switches are in the closed state, N≠M.
8. The directional coupler according to claim 4, characterized in that, The third impedance matching circuit includes a first resistor and a first capacitor connected in parallel, and one common terminal of the first resistor and the first capacitor connected in parallel is connected to the first end of the coupling line through the sixth switch, and the other common terminal is grounded.
9. The directional coupler according to claim 4, characterized in that, The fourth impedance matching circuit includes a second resistor and a second capacitor connected in parallel, and one common terminal of the second resistor and the second capacitor connected in parallel is connected to the second terminal of the coupling line through the seventh switch, while the other common terminal is grounded.
10. A radio frequency front-end module, characterized in that, Includes the directional coupler as described in any one of claims 1-9.