CN204271236U - A Broadband Miniaturized Directional Coupler - Google Patents

Abstract

The utility model discloses a wide-band miniaturized directional coupler, which includes a main transmission line, and two ports of the main transmission line are respectively an input port and a straight-through port of the directional coupler, and further includes an amplitude equalization network I and an isolation resistor I A secondary transmission line I coupled with the main transmission line, the main transmission line and the secondary transmission line I form a coupled microstrip line I, wherein one end of the amplitude equalization network I is connected to the coupling end of the coupled microstrip line I, and the other end is the coupling end of the directional coupler Coupling port, one end of the isolation resistor I is connected to the isolation end of the coupling microstrip line I, and the other end is grounded. The broadband miniaturized directional coupler of the utility model has wide working frequency band, small size, simple manufacturing process and low production cost.

Description

A Broadband Miniaturized Directional Coupler

technical field

The utility model relates to the field of radio frequency circuit design, in particular to a broadband miniaturized directional coupler.

Background technique

The directional coupler is a radio frequency device widely used in the radio frequency system. Its essence is to distribute the power of the radio frequency signal according to a certain ratio, and couple a part of the radio frequency signal transmitted in the main transmission line for power detection. The directional coupler is generally a four-port network, the first port is the input end, the second port is the through end, the transmission line between the first port and the second port is the main transmission line; the other transmission line is the secondary transmission line (ie, coupling line), The port adjacent to the first port in the secondary transmission line is a coupling end, and the other port is an isolation end.

The technical indicators of directional couplers mainly include coupling degree, working bandwidth, insertion loss, coupling degree flatness and directivity. The existing technology has the following deficiencies: first, the traditional two-hole magnetic wrapping wire method has a relatively small power capacity, and when the power is high, it will produce a certain nonlinearity, which will generate interference signals and affect the communication effect; second, the use of λ The /4 transmission line coupler must be connected in multiple stages to achieve broadband use. When used in the VHF/UHF frequency band, the working wavelength is longer, and with more orders, the insertion loss and size are larger.

Utility model content

The purpose of the utility model is to overcome the shortcomings and deficiencies of the prior art, and provide a broadband miniaturized directional coupler.

The purpose of this utility model is achieved through the following technical solutions:

A broadband miniaturized directional coupler, including a main transmission line, the two ports of the main transmission line are respectively the input port and the through port of the directional coupler, and also include an amplitude equalization network I, an isolation resistor I, and a main transmission line coupling The secondary transmission line I, the main transmission line and the secondary transmission line I form a coupled microstrip line I, wherein one end of the amplitude equalization network I is connected to the coupled end of the coupled microstrip line I, and the other end is the coupling port of the directional coupler. The isolation resistor One end of device I is connected to the isolation end of coupled microstrip line I, and the other end is grounded.

The amplitude equalization network I is an equalization network with a transmission characteristic of 6dB attenuation per octave.

The amplitude equalization network I includes resistors R1, R2, R3, and an inductor L1, wherein R2, R3 are connected in parallel to the coupling port of the directional coupler, the other end of R2 is grounded, and the other end of R3 is connected to R1 It is connected in parallel to the inductor L1, the other end of R1 is grounded, and the other end of L1 is connected to the coupling end of the coupled microstrip line I.

The broadband miniaturized directional coupler also includes an amplitude equalization network II, an isolation resistor II, and an auxiliary transmission line II coupled with the main transmission line. The main transmission line and the auxiliary transmission line II form a coupling microstrip line II, wherein the amplitude equalization network II One end of the coupling microstrip line II is connected to the coupling end, the other end is the coupling port of the directional coupler, one end of the isolation resistor II is connected to the isolation end of the coupling microstrip line II, and the other end is grounded; the amplitude Balance network I, sub-transmission line I, isolation resistor I and amplitude equalization network II, sub-transmission line II, and isolation resistor II are mirror-symmetrically arranged on both sides of the vertical line of the main transmission line. The wide-band miniaturized directional coupler of the utility model realizes dual orientation, and can simultaneously sample signals in the forward and reverse directions, and the forward and reverse sampling work independently, and the forward and reverse isolation is greater than 20dB.

The amplitude equalization network II is an equalization network with a transmission characteristic of 6dB attenuation per octave.

The amplitude equalization network II includes resistors R5, R6, R7, and an inductor L2, wherein R6 and R7 are connected in parallel to the coupling port of the directional coupler, the other end of R6 is grounded, and the other end of R7 is connected to R5 It is connected in parallel to the inductor L2, the other end of R5 is grounded, and the other end of L2 is connected to the coupled end of the coupled microstrip line II.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

1. The broadband miniaturized directional coupler described in this utility model can realize broadband use without multi-stage cascading, and the insertion loss is small, and the coupling flatness can be realized when used across octaves in the VHF/UHF frequency band Not more than ±0.3dB, insertion loss is less than 0.2dB.

2. The wide-band miniaturized directional coupler described in the utility model has small size, simple production process, and low cost. It is realized by coupling microstrip line and amplitude equalization network, and the size of the coupler is greatly reduced. At the same time, the coupler adopts PCB Layout printed circuits, devices are mounted, the production process is simple, and the cost is low.

Description of drawings

Fig. 1 is a broadband dual-directional coupler described in the utility model.

Detailed ways

The utility model will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the implementation of the utility model is not limited thereto.

As shown in Figure 1, a broadband miniaturized directional coupler includes a main transmission line, and the two ports of the main transmission line are respectively the input port and the through port of the directional coupler, and also includes an amplitude equalization network I, an isolation resistor I, The sub-transmission line I coupled with the main transmission line, the main transmission line and the sub-transmission line I form a coupled microstrip line I, wherein one end of the amplitude equalization network I is connected to the coupling end of the coupled microstrip line I, and the other end is the coupling of the directional coupler One end of the isolation resistor I is connected to the isolation end of the coupled microstrip line I, and the other end is grounded;

The broadband miniaturized directional coupler also includes an amplitude equalization network II, an isolation resistor II, and an auxiliary transmission line II coupled with the main transmission line. The main transmission line and the auxiliary transmission line II form a coupling microstrip line II, wherein the amplitude equalization network II One end of the coupling microstrip line II is connected to the coupling end, the other end is the coupling port of the directional coupler, one end of the isolation resistor II is connected to the isolation end of the coupling microstrip line II, and the other end is grounded; the amplitude Equilibrium network Ⅰ, secondary transmission line Ⅰ, isolation resistor Ⅰ and amplitude equalization network Ⅱ, secondary transmission line Ⅱ, and isolation resistor Ⅱ are mirror-symmetrically arranged on both sides of the vertical line of the main transmission line;

The amplitude equalization network I includes resistors R1, R2, R3, and an inductor L1, wherein R2, R3 are connected in parallel to the coupling port of the directional coupler, the other end of R2 is grounded, and the other end of R3 is connected to R1 Connect to the inductor L1 in parallel, the other end of R1 is grounded, and the other end of L1 is connected to the coupling end of the coupled microstrip line I;

The amplitude equalization network II includes resistors R5, R6, R7, and an inductor L2, wherein R6 and R7 are connected in parallel to the coupling port of the directional coupler, the other end of R6 is grounded, and the other end of R7 is connected to R5 Connect to the inductor L2 in parallel, the other end of R5 is grounded, and the other end of L2 is connected to the coupling end of the coupled microstrip line II;

The isolation resistor I is R4, and the isolation resistor II is R8.

Its specific working process is as follows:

As shown in Figure 1, the values of resistors R1, R2, R5, and R6 are 120Ω, the values of resistors R4 and R8 are 60Ω (obtained by connecting two resistors with resistances of 120Ω in parallel), and the values of inductors L1 and L2 are 82nH, within the working frequency range of 225MHz～512MHz, the coupling degree of the directional coupler is 48.8dB, the flatness is not greater than ±0.3dB, and the directivity is greater than 20dB. The overall structural size of the dual directional coupler is only 38mm×20mm×2mm.

As shown in Figure 1, we define the direction of signal transmission from Port1 input to Port2 as forward, and the direction of signal transmission from Port2 input to Port1 as reverse. For the forward unidirectional coupler, Port1 is the input port, Port2 is the straight-through port, Port3 is the coupling port, and the isolation terminal is connected to the resistor R4. Adjusting the resistance of R4 can make the forward unidirectional coupler obtain better Directionality; for the reverse single-directional coupler, Port2 is the input port, Port1 is the through port, Port4 is the coupling port, and the isolated end is connected to R8. Adjusting the resistance of R8 can make the reverse single-directional coupler get better Directivity, where resistors R4 and R8 have the same resistance value.

In actual use, Port1 is connected to the RF output port of the high-power broadband linear RF power amplifier, and Port2 is connected to the RF input port of the antenna. The sampling mechanism of the forward single-directional coupler is as follows: When the high-power RF signal output by the RF power amplifier is transmitted from Port1 to Port2 along the main microstrip transmission line, the secondary transmission line of the microstrip couples a part of the signal from the main transmission line of the microstrip through the coupling gap The energy is sent to the equalization network. When the length of the coupling region is less than one-tenth of the working wavelength, the amplitude-frequency characteristic curve of the coupled signal will change according to the law of increasing 6dB per octave; through reasonable configuration of the inductance in the equalization network The inductance value of the inductor L1 and the resistance values of the resistors R1, R2 and R3 can make the transmission characteristic curve of the equalization network change according to the rule that the attenuation of each octave increases by 6dB; the inductor L1 is mainly used to adjust the forward single-directional coupling The center frequency of the device, the inductance value increases, the center frequency will decrease accordingly. The Π-type attenuation network composed of resistors R1, R2 and R3 is mainly used to adjust the coupling degree of the forward unidirectional coupler. When the attenuation value of the attenuation network increases, the coupling degree of the forward unidirectional coupler increases, and the The attenuation network is also used to adjust the port impedance matching of the forward coupling port Port3.

When the antenna port generates reflection due to impedance mismatch, the reflected signal is transmitted from Port2 to Port1 along the main microstrip transmission line. The sampling mechanism of the reverse single-directional coupler is the same as that of the above-mentioned forward single-directional coupler. Among them, L2 is used to adjust the center frequency of the reverse directional coupler, and the Π-type attenuation network composed of resistors R5, R6 and R7 is mainly used to adjust the coupling degree of the reverse directional coupler and the port impedance of the reverse coupling port Port4 match. Among them, the resistance values of resistors R5, R6, R1 and R2 are the same, the resistance values of resistors R4 and R8 are the same, the resistance values of resistors R7 and R3 are the same, the inductance values of inductors L2 and L1 are the same, reverse single-directional coupling The coupling degree and isolation degree of the forward single-directional coupler are the same as those of the forward unidirectional coupler.

The forward single-directional coupler and the reverse single-directional coupler are directly connected to form a double-directional coupler, which can simultaneously sample the forward signal and the reverse signal.

The above-mentioned embodiment is a preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the above-mentioned embodiment, and any other changes, modifications and substitutions made without departing from the spirit and principle of the present utility model , combination, and simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (6)

1. the miniaturized directional coupler of broadband, it is characterized in that: comprise main transmission line, two ports of main transmission line are respectively the input port of described directional coupler, straightthrough port, also comprise amplitude equalization network I, isolation resistor I, the secondary transmission line I be coupled with main transmission line, main transmission line and secondary transmission line I form coupled microstrip line I, wherein one end of amplitude equalization network I is connected with the coupled end of coupled microstrip line I, the other end is the coupling aperture of described directional coupler, one end of isolation resistor I is connected with the isolation end of coupled microstrip line I, other end ground connection.

2. the miniaturized directional coupler of broadband according to claim 1, is characterized in that: described amplitude equalization network I is for having the equalizing network of every octave decay 6dB transmission characteristic.

3. the miniaturized directional coupler of broadband according to claim 2, it is characterized in that: described amplitude equalization network I, comprise resistor R1, R2, R3, and inductor L1, wherein R2, R3 are connected in parallel to the coupling aperture of described directional coupler, the other end ground connection of R2, and the other end of R3 and R1 are connected in parallel to inductance L 1, the other end ground connection of R1, the other end of L1 is connected with the coupled end of coupled microstrip line I.

4. the miniaturized directional coupler of broadband according to claim 1, it is characterized in that: also comprise amplitude equalization network II, isolation resistor II, the secondary transmission line II that is coupled with main transmission line, main transmission line and secondary transmission line II form coupled microstrip line II, wherein one end of amplitude equalization network II is connected with the coupled end of coupled microstrip line II, the other end is the coupling aperture of described directional coupler, one end of isolation resistor II is connected with the isolation end of coupled microstrip line II, other end ground connection; Described amplitude equalization network I, secondary transmission line I, isolation resistor I and amplitude equalization network II, secondary transmission line II, isolation resistor II are arranged in the both sides of the vertical line of main transmission line in Mirror Symmetry.

5. the miniaturized directional coupler of broadband according to claim 4, is characterized in that: described amplitude equalization network II is for having the equalizing network of every octave decay 6dB transmission characteristic.

6. the miniaturized directional coupler of broadband according to claim 5, it is characterized in that: described amplitude equalization network II, comprise resistor R5, R6, R7, and inductor L2, wherein R6, R7 are connected in parallel to the coupling aperture of described directional coupler, the other end ground connection of R6, and the other end of R7 and R5 are connected in parallel to inductance L 2, the other end ground connection of R5, the other end of L2 is connected with the coupled end of coupled microstrip line II.