A broadband coupled-line directional coupler circuit

Abstract

The present invention is applicable to the technical field of broadband coupled line power distribution, and provides a broadband coupled line directional coupler circuit, which is a four-port microstrip circuit, wherein a certain gap is passed between the through line and the coupled line to couple part of the through line power to the coupled line, and it is required that the power is only transmitted to a certain output port in the coupled line, and no power is output at the other port. For the broadband coupled line directional coupler circuit, the cost can be greatly reduced, and the electrical characteristics are significantly stable. A certain gap is passed between the main line and the auxiliary line in the circuit, and part of the main line power is coupled to the auxiliary line, and it is required that the power is only transmitted to a designated output port in the coupled line, so as to realize power distribution and achieve isolation between signals.

Description

Technical Field

[0001] The invention belongs to the technical field of broadband coupled line power distribution, and in particular relates to a broadband coupled line directional coupler circuit. Background Art

[0002] In satellite communications, multiple satellites are generally selected for signal transmission to ensure the continuity and reliability of communication. Therefore, when switching signals from different satellites, a satellite switch is needed to switch the received satellite signals to select the best signal for transmission. The core circuit of the satellite switch uses a directional coupler to achieve signal power distribution. The performance of the directional coupler determines the continuity and stability of communication.

[0003] In order to achieve stability, the existing solution is to use a high-frequency transformer made of high-frequency ferrite fired enameled wire to achieve power distribution, but this distribution method is inconvenient to manufacture and has high cost, especially poor stability, and is prone to characteristics degradation due to oscillation. After long-term use, the coil turns are prone to short circuits. Summary of the invention

[0004] The object of the present invention is to provide a broadband coupled-line directional coupler circuit, aiming to solve the problems existing in the background technology.

[0005] The present invention is implemented in this way: a broadband coupled line directional coupler circuit mainly comprises two parts: a main line and a secondary line.

[0006] The broadband coupled line directional coupler circuit is a four-port microstrip circuit. A certain gap is used between the straight line and the coupled line to couple part of the straight line power to the coupled line, and the power is required to be transmitted to a certain output port in the coupled line, and no power is output at the other port. The input frequency of the directional coupler is 290MHz-2350MHz. It receives the intermediate frequency signal after the satellite high frequency head is downconverted. Part of the signal is output through the main line with an insertion loss as low as 0.75dB, and then connected to the input end of the next coupled line directional coupler, which can achieve 1-12 power distribution output; the other part is output through the branch line. The branch end output is designed to be -20dB output according to the actual needs of the satellite receiving system, and then connected to the filter in the satellite switching switch, and then connected to the set-top box through the RF connection cable, so as to watch stable and high-quality satellite TV programs.

[0007] As a further solution of the present circuit invention, the PCB material adopts 0.8mm 7628NO INNER1 high frequency material.

[0008] As a further solution of the present invention, the microstrip coupled line is simulated and calculated by ADS microwave simulation software, the line width is designed to be 0.35mm, and the gap between the main line and the auxiliary line is designed to be 0.18mm. The actual measurement results of the circuit on the PCB are: S21 (insertion loss) is greater than -0.75dB, S23 (isolation) is less than -30dB, S31 (branch port to input port isolation) is less than -16dB, S11 (input port reflection loss) is less than -12dB, and S33 (branch port reflection loss) is less than -12dB.

[0009] A broadband coupled line directional coupler circuit provided by the present invention has the following beneficial effects:

[0010] For broadband coupled-line directional coupler circuits, the cost can be greatly reduced, and the electrical characteristics are significantly stable. A certain gap is passed between the main line and the auxiliary line in the circuit, and part of the main line power is coupled to the auxiliary line. It is required that the power is only transmitted to a designated output port in the coupled line to achieve power distribution, which can achieve isolation between signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the circuit diagram of the broadband coupled line directional coupler;

[0012] Figure 2 This is the 3D simulation diagram of the broadband coupled-line directional coupler;

[0013] Figure 3 This is the circuit board assembly diagram of this broadband coupled-line directional coupler;

[0014] Figure 4 This is the S parameter test diagram of this broadband coupled-line directional coupler circuit. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0017] like Figure 1 and Figure 2 As shown, a broadband coupled line directional coupler circuit, the broadband coupled line directional coupler circuit comprising:

[0018] A first-stage directional coupler main line A, wherein an input port Port1 of the first-stage directional coupler main line A is connected to a radio frequency signal source and is used to transmit a satellite intermediate frequency signal of 230-2350 MHz;

[0019] A first-stage directional coupler sub-line B, which is arranged at one side of the first-stage directional coupler main line A, and couples the signal power of the first-stage directional coupler main line A through a slot, and is used to distribute the power to the branch port Port3 for directional coupling;

[0020] A second-stage directional coupler main line C, wherein an input port of the second-stage directional coupler main line C is connected to a branch port Port3 for transmitting a signal;

[0021] The secondary line D of the second-stage directional coupler is coupled with the main line C of the second-stage directional coupler, and outputs a signal through the branch port Port5;

[0022] The third-stage directional coupler main line E is connected to the second-stage directional coupler main line C to establish a signal transmission path;

[0023] The third-stage directional coupler secondary line F is coupled to the third-stage directional coupler main line E and outputs a signal through a branch port Port7;

[0024] The output port Port2 is connected to the main line E of the third-stage directional coupler for receiving the final output signal;

[0025] The matching port Port4, the matching port Port6 and the matching port Port8 are respectively connected to the first-stage, second-stage and third-stage matching networks for impedance matching and signal isolation.

[0026] like Figure 3 As shown, this is the assembly diagram of the broadband coupled line directional coupler circuit board. For the circuit board, U1 is the first-stage directional coupler, U2 is the second-stage directional coupler, and U3 is the third-stage directional coupler.

[0027] U1 is the first-stage broadband coupled-line directional coupler circuit, U2 is the second-stage broadband coupled-line directional coupler circuit, and U3 is the third-stage broadband coupled-line directional coupler circuit, which can realize three-stage cascade. For the sake of simplicity, this experiment only uses the first-stage directional coupling branch output, and the second and third-stage branch ends are connected to load resistors, and no branch loss test is performed.

[0028] In the embodiment of the present invention, the first-stage directional coupler secondary line B couples part of the power of the first-stage directional coupler main line A to the branch port Port3 through the slot, so as to control the unidirectional transmission of the signal.

[0029] In the embodiment of the present invention, the branch port Port3 outputs a -20 dB power signal and is connected to a filter in the satellite switch for signal processing.

[0030] like Figure 2 As shown, the second-stage directional coupler sub-line D and the third-stage directional coupler sub-line F are both provided with a matching port Port6 and a matching port Port8 for impedance matching.

[0031] like Figure 3 As shown, the circuit includes an adjustable signal attenuation adjustment resistor R4, which is used to adjust the attenuation of the branch output terminal signal.

[0032] like Figure 3 As shown, the circuit further includes a DC blocking capacitor C1, a DC capacitor C2 and load resistors R1, R2, R3 and R5 for signal isolation and load matching.

[0033] like Figure 3 As shown, the inter-stage matching inductors L1 and L2 in the circuit are used to improve the signal transmission efficiency between each stage.

[0034] Combination Figure 4 , S11 is the reflection loss test value of the first-stage directional coupler input end; S21 is the main line insertion loss test value of the three-stage directional coupler; S31 is the branch loss test value of the first-stage directional coupler; S33 is the reflection loss test value of the first-stage directional coupler branch end; S23 is the isolation test value from the third-stage output end to the first-stage branch end.

[0035] The operating frequency of this broadband coupled-line directional coupler circuit is 230-2350MHz wide band. The actual measurement results of the experimental board using Agilent vector network analyzer are: S21 (insertion loss) is greater than -0.75dB, S23 (isolation) is less than -30dB, S31 (branch port to input port isolation) is less than -16dB, S11 (input port reflection loss) is less than -12dB, S33 (branch port reflection loss) is less than -12dB.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A broadband coupled-line directional coupler circuit, characterized in that: The broadband coupled-line directional coupler circuit comprises: A first-stage directional coupler main line A, wherein an input port Port1 of the first-stage directional coupler main line A is connected to a radio frequency signal source and is used to transmit a satellite intermediate frequency signal of 230-2350 MHz; A first-stage directional coupler sub-line B, which is arranged at one side of the first-stage directional coupler main line A, and couples the signal power of the first-stage directional coupler main line A through a slot, and is used to distribute the power to the branch port Port3 for directional coupling; A second-stage directional coupler main line C, wherein an input port of the second-stage directional coupler main line C is connected to a branch port Port3 for transmitting a signal; The secondary line D of the second-stage directional coupler is coupled with the main line C of the second-stage directional coupler, and outputs a signal through the branch port Port5; The third-stage directional coupler main line E is connected to the second-stage directional coupler main line C to establish a signal transmission path; The third-stage directional coupler secondary line F is coupled to the third-stage directional coupler main line E and outputs a signal through a branch port Port7; The output port Port2 is connected to the main line E of the third-stage directional coupler for receiving the final output signal; The matching port Port4, the matching port Port6 and the matching port Port8 are respectively connected to the first-stage, second-stage and third-stage matching networks for impedance matching and signal isolation.

2. The broadband coupled-line directional coupler circuit according to claim 1, characterized in that: The first-stage directional coupler secondary line B couples part of the power of the first-stage directional coupler main line A to the branch port Port3 through the slot, so as to control the unidirectional transmission of the signal.

3. The broadband coupled-line directional coupler circuit according to claim 2, characterized in that: The branch port Port3 outputs a -20 dB power signal and is connected to a filter in the satellite switch for signal processing.

4. The broadband coupled-line directional coupler circuit according to claim 1, characterized in that: The second-stage directional coupler sub-line D and the third-stage directional coupler sub-line F are both provided with a matching port Port6 and a matching port Port8 for impedance matching.

5. The broadband coupled-line directional coupler circuit according to claim 1, characterized in that: The circuit includes an adjustable signal attenuation adjustment resistor R4, which is used to adjust the attenuation of the branch output terminal signal.

6. The broadband coupled-line directional coupler circuit according to claim 1, characterized in that: The circuit further includes a DC blocking capacitor C1, a DC capacitor C2 and load resistors R1, R2, R3 and R5 for signal isolation and load matching.

7. The broadband coupled-line directional coupler circuit according to claim 1, characterized in that: The inter-stage matching inductors L1 and L2 in the circuit are used to improve the signal transmission efficiency between each stage.

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