JPH0150131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a directional coupler installed in a transmission output section of a VHF band radio communication device or the like. [Prior art] A directional coupler used in a wireless communication device transmits by attaching a wire of a certain length (1/8 wavelength or more) as a directional coupling line to the transmission power line between the transmitter output side and the antenna. It generates an induced voltage by receiving electromagnetic waves generated from the power line, and in addition to the above-mentioned wire, there is also a coaxial type (shielded cable, etc.) attached to the outer periphery of the transmitting power line.
There are those that have a dielectric of a certain length, and those that have two or more linear patterns on a printed circuit board and use one of them as a transmission power line for a directional coupler, and those that use a wire for generating induced voltage as a transmission power line. There are directional couplers and the like that are inserted into a wound ferrite core to obtain induced power. The output of this directional coupler is used for forward wave voltage, reflected wave power, SWR meter, etc. to monitor the output matching of the transmitter. Here, a method of separating and detecting the transmitted power and the reflected wave power is disclosed in Japanese Utility Model Publication No. 57-4520, etc., in which the central thin line pattern is used as the transmitter by using the conductive pattern of the printed circuit board. This is the transmission output line connecting the antennas, and the CM directional coupler configured with a thin line pattern is shown on both sides. However, since the pattern length requires at least 1/8 wavelength, at frequencies below VHF it is often adopted and separated due to the shape. In addition, coaxial type directional couplers can be bent, so the length is not a problem, but processing is time-consuming, making them unsuitable for mass production. In addition, the current transformer type, which is currently widely used in frequency bands below VHF, has a structure in which a ring core 1 with a secondary winding 2 is passed through a transmission output line 3 between the transmitter and the antenna, as shown in Figure 1. A voltage proportional to the passing current is induced in the secondary winding 2 by detecting the standing wave ratio of the passing power and reflected waves. Furthermore, when a suitable capacitor 4 is coupled between the through conductor and one end of the secondary winding, it operates as a directional coupler that detects only the power in one direction determined by the winding direction and the coupling position, and the secondary winding Detector 5 outputs
The rectified DC output voltage is used to swing a meter and control circuits. [Problem to be solved by the invention] As in the three types of directional couplers shown in the prior art, there are two types: a high-frequency dedicated type in which a detection line is provided in parallel with the transmission line on a printed circuit board, and a type in which a detection line is provided in parallel with the transmission line on a printed circuit board, and a type using a coaxial cable. The adjustment process is complicated, and the ring core method requires a special ferrite material with a large μ at high frequencies, which has the disadvantage of cracking when handled. The purpose is to provide a directional coupler. [Means for solving the problem] A conductor band connecting the transmitter output stage and the load terminal is formed on one surface of a double-sided board made by bonding copper plates to both sides of an insulator, and the conductor band and the board supporting it are formed. By forming a coil with an arbitrary number of turns using a conductor wire that is insulated from the conductor band and the copper plate on the back side, and detecting the induced voltage in the coil,
The configuration is such that traveling wave power, reflected wave power, or standing wave ratio can be measured. [Embodiment] FIG. 2 is a perspective view of a directional coupler showing an embodiment of the present invention, and FIG. 2 will be explained. In the figure, a conductor band 13 and other required patterns are formed by ordinary etching on the surface copper plate 11a of a double-sided conductor board 10 (although there is no distinction between the front and back of the double-sided printed circuit board itself, for convenience, the conductor band 13 is Holes 14a to 14n are provided in the substrate on both sides of the conductor band 13, and the conductor 12 is wound through the holes in a solenoid coil shape with the conductor band 13 as the center, and one end of the wire is connected to the detection rectifier 15. The other end is grounded through the balance adjuster 16. It is desirable that the conductive wire 12 forming the coil is closely coupled to the conductor band 13, so it is necessary to wrap the conductor wire closely on the board surface, and the coated wire is also used so that it can come into direct contact with the conductor band and the back copper plate 11b. Alternatively, a thin insulator may be sandwiched between the substrate and the substrate. Conductive wire 12 on the back side of the board
Alternatively, a pattern may be etched on the back copper plate 11b to form a part of the coil. The operating principle of this directional coupler can be considered as follows. That is, when the length of the conductor band 13 is sufficiently small compared to the wavelength, the stripline
Since it is close to the TEN mode, in the cross section perpendicular to the conductor 13 in FIG. It is closed in free space on the band 13. The conducting wire 12 of the coil portion forming the secondary line for induced voltage shares a common magnetic field with the conductor band 13 and has a certain angle with respect to the direction of the lines of magnetic force, so that a secondary voltage can be induced. Also conductor band 1
Since the secondary side induced voltage output can have directionality due to the coupling by the stray capacitance between the secondary side electromotive force 3 and the conductive wire 12 of the secondary line for induced voltage, the component corresponding to the capacitor 4 in FIG. 1 can be omitted. For convenience, the balance adjuster 16 in FIG. 2 also serves as a capacitively coupled load. Experiments have shown that the greater the number of turns of the conductive wire 12 as a secondary wire, the greater the secondary electromotive force and the higher the detection sensitivity, but if the number of turns is too large, the effect of self-resonance will occur, so it should be reduced as much as possible within the practically necessary range. It's better. 144M is used to detect load mismatch using reflected wave power and operate the output stage protection circuit.
In the case of an output of 10 W in the Hz band, 4 or 5 turns was sufficient. Since protective operation is not necessary at an output of about 5 W or less, there is no problem even if it does not operate. For reference, Table 1 shows the conductor band (width 3.0mm length 35.0mm)
shows the detection voltage (DC output) at 144.5MHz of a directional coupler configured with a 0.8mm wire wound four times to a total length of 20.0mm. Transmitter power 10W, 15W, 20W, 25W
For both, at 50Ω matched load (SWR=
The change in detection voltage between 1) and 150Ω load (SWR = 3) reaches more than 10 times, so this is enough to directly operate the protection circuit. [Effects of the Invention] The directional coupler of the present invention has dimensions suitable for incorporation into equipment for the VHF band, and a simple and robust structure, and has practical effects when implemented as a directional coupler. There is. 【table】

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional current transformer type directional coupler, Fig. 2 is a perspective view showing the configuration of the directional coupler of the present invention, and Fig. 3 is a sectional view of the directional coupler. be. 1... Ring core of directional coupler, 2... Secondary winding, 3... Transmission power line, 4... Capacitor,
5, 15...Detection rectifier, 10...Double-sided conductor board, 11a, 11b...Conductor copper plate, 12...Conductor wire, 13...Conductor band, 14a-14n...Conductor insertion hole, 16...Balance adjuster.

Claims (1)

[Claims] 1 A directional coupler installed between the output stage of a wireless communication device and an antenna to detect traveling wave power and reflected wave power, with copper plates 11a and 11b on both sides of the insulator.
A conductor band 13 connecting the transmitter output stage and the load terminal is formed on one surface of the double-sided conductor substrate 10 formed by adhering the
The core includes the conductor band 13 and the insulator supporting it, and the conductor band 13 and the copper plate 1 on the back side.
By forming a coil of arbitrary winding with the conducting wire 12 insulated from 1b and detecting the induced voltage induced in the coil by the electromagnetic wave generated by the transmission output passing through the conductor band 13, traveling wave power, A directional coupler characterized by being capable of measuring reflected wave power or standing wave ratio.