JPS61206322A - Antenna impedance matching circuit - Google Patents

Abstract

PURPOSE:To obtain quickly the matching state by providing plural series circuits comprising capacitors with fixed capacitance and switches provided at its grounding side, constituting an impedance matching circuit with them and inductances and providing a reflection power measuring circuit and a control circuit at the transmitter side. CONSTITUTION:The control circuit for reflecting power is constituted by an input/output device 50, a CPU 60 and diode drive sections 30, 40. A matching circuit where on end of capacitors other than capacitors 10, 20 is grounded is constituted at the initial set state. In starting new control of matching by movement of an antenna, the reflecting power extracted by a directional coupler 9, a diode 51 and an A/D converter 52 is measured by the CPU 60 so as to discriminate whether or not the power is minimized. That is, the power is compared with the reflecting power at the initial matching state. When the said power is not a minimum value, the number of turned-on PIN diodes 46-48 is adjusted and when the reflection power measurement shows a minimum value, the PIN diodes 46-48 are operated and the adjustment similar to above is attained. Then the value reaches a minimum value by repeating the said adjustment.

Description

[Detailed Description of the Invention] [Summary] The present invention uses a circuit that combines a capacitor and an inductance as a circuit for matching the input impedance of the antenna side with the output impedance of the transmitter, and uses a series circuit of a capacitor and a switch. - Provide multiple sets of capacitors and control the ground potential connection of the capacitors to obtain good matching.

[Industrial Application Field] The present invention relates to an impedance matching circuit that controls a switch provided on the ground side of a capacitor in order to constantly match the impedance seen from a transmitter to an antenna.

[Prior Art] Mobile radio antennas such as those used in in-vehicle transceivers undergo large changes in the antenna environment, such as when approaching people or surrounding buildings, and as a result, the impedance of the antenna viewed from the transceiver changes significantly. FIG. 4 shows the configuration of a conventional impedance matching circuit provided between an antenna and a transmitter. In FIG. 4, ] is an antenna, 2 is a load such as a transmitter/receiver, 3.4 is a fixed capacitor, and 5 is an inductance. A π-type matching circuit is formed by the capacitors 3 and 4 and the inductance, and the π-type matching circuit is usually only adjusted when there are no objects in the vicinity of the antenna. In addition, in antennas whose positions are fixed, such as broadcast antennas and communication antennas, the rotor of an impedance matching capacitor is rotated by a motor to variably control the capacitance.

[Problems to be Solved by the Invention] Therefore, when the surrounding situation changes, such as when the antenna moves, impedance mismatch naturally occurs, which affects the power radiated from the antenna. Also,
With the method of rotating the rotor of the capacitor, it was not possible to achieve matching as quickly as possible when the situation around the antenna changed.

[Means for Solving the Problems] The means adopted in the present invention is configured as shown in FIG. In other words, in Fig. 1, fixed capacity capacitors 11.12 and 13-120.2 are used as capacitors.
1, 22, and 23 are used, and a plurality of series circuits are provided with switches 16, 17, 18, 26, and 27, 28 provided on the ground 6 side of the capacitor. These capacitors and inductance 5 constitute an impedance matching circuit. Also, on the transmitter 2 side of the matching circuit, there is a reflected power measuring device 7 from the antenna.
and a control circuit 8. The control circuit 8 connects the switch 16 to
Regarding No. 28, the change in reflected power before and after the closing control is determined, and the next opening/closing control is performed.

[Operation] The reflected power from the antenna is measured by a reflected power measuring device, and based on the result, the control circuit 8 controls the switches 16 to 28 to turn on and off, and determines the magnitude of the reflected power before and after the control. conduct. Then, conditions for minimizing the reflected power are obtained as soon as possible to achieve a good matching state.

[Embodiment] FIG. 2 is a block diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same components. In Figure 2, 30.
40 is a PIN diode drive section, 36.37.38.4
6, 47, 48 are PIN diodes, 50 is an input/output device, 60 is a central processing unit CPU, 9 is a directional coupler, 51
52 is a detection diode, 52 is an A/D converter, and 53 is a high frequency choke coil. The input/output device 50, the central processing unit 60 (CPU), and the diode drive sections 30 and 40 constitute the above-mentioned reflected power control circuit.

The central processing unit 60 (CPU) operates as shown in the operational flowchart of FIG. The antenna is initially set when there is nothing nearby that can change the impedance. At this time, in addition to capacitors 10 and 20, other capacitors often constitute a matching circuit in which one end of the capacitor is grounded.

Next, when starting a new matching control such as when the antenna moves, the reflected power measurement in step (2) is performed since the initial value setting in step (2) is normally done. This is to measure the reflected power extracted by the directional coupler 9 and the diode 51° A/D converter 52 in the central processing unit 60. Next, in step (2), it is determined whether the power is minimum. That is, since the reflected power in the initial impedance matching state should be the minimum, it is compared with that.

Since it is usually not the minimum, proceed to step (3) and determine whether the reflected power has decreased. Normally, it has not decreased, so reduce or increase the number of PIN diodes 36, 37, and 38 turned on in the previous stage and return to step (2). These steps are repeated, and when the reflected power measurement value reaches the minimum value, the PIN diode 46 on the downstream side of the inductance 5
, 47° and 48, and perform step ① and subsequent steps in the same manner as before. When the state of minimum reflected power is obtained by the subsequent stage operation, it is desirable to return to the previous stage and readjust. Then, the minimum value in step (2) is reached.

[Effects of the Invention] As described above, according to the present invention, since the opening/closing operation of the switch connected to the ground is quickly performed by electrical processing, impedance matching can be re-established in a shorter time than conventionally.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle configuration of the present invention. Fig. 2 is a block diagram showing an embodiment of the invention. Fig. 3 is an operation flowchart of Fig. 2. Fig. 4 is a diagram showing a conventional impedance matching circuit. It is. 1... Antenna 2 - Load 3 such as a transmitter, 4.10.11...-20,21... Capacitor 5-
Inductance 6 - Grounding 7 - Antenna reflected power measuring device 8 - Size determination/control circuit

Claims (1)

[Claims] An antenna (1
) and the transmitter (2), use fixed capacitors (10) (11) as the capacitors.
...(21)(22)..., and a switch (16)(17)...(26)(27)... is installed on the grounding side of the capacitor.
and a series circuit with a reflected power measuring device (7) from the antenna provided on the transmitter side of the impedance matching circuit, and controlling the opening and closing of the switch based on the output of the reflected power measuring device (7). 1. An antenna impedance matching circuit comprising: a circuit for determining the magnitude of output before and after control; and controlling opening and closing of the switch so that reflected power from the antenna is minimized.