JPH10294636A - Impedance matching circuit - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an impedance matching circuit capable of expanding a load impedance matching range without obstructing physical conditions such as dimensions of the impedance matching circuit. An impedance conversion circuit is provided between a load and an L-type impedance matching circuit including a variable capacitor and a variable coil connected to a signal source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance matching circuit used for, for example, a short-wave transmitter and connected between an antenna and a transmitter.

[0002]

2. Description of the Related Art Conventionally, when performing impedance matching between an impedance Zo on a signal source (transmitter) side and an impedance Zx on a load (antenna) side which varies widely depending on a used frequency, an L-type which has a theoretically wide matching range Is generally used.

FIG. 4 shows an example of this L-type impedance matching circuit. The L-type impedance matching circuit 1 shown in FIG. 4 includes a variable capacitor 2 and a variable coil 3 for changing inductance, and its matching range has a characteristic of a theoretical value as shown in FIG. is there. The hatched portion indicates a mismatched portion.

However, since the L-type impedance matching circuit 1 has a theoretically unmatchable range as shown by a hatched portion in FIG. 5, if necessary, a matching range opposite to the matching range is required. Is used in combination with the impedance matching circuit 4 shown in FIG. The theoretical value of the matching range of the impedance matching circuit 4 of FIG.
It has the characteristics shown in FIG. The hatched portion indicates a mismatched portion.

Therefore, as can be seen from the characteristics of FIGS. 5 and 7, if the impedance matching circuits 1 and 4 shown in FIGS. 4 and 6 are switched and used in theory, all load impedances Zx And signal source impedance Z
The impedance matching with o can be achieved.

[0006]

However, the matching ranges in the conventional impedance matching circuits 1 and 4 shown in FIGS. 4 and 6 are determined by the variable ranges of the variable capacitor 2 and the variable coil 3 of each circuit. , The wider the variable range, the wider the matching range,
In an actual matching circuit, due to physical restrictions such as dimensions of the variable capacitor 2 and the variable coil 3 and the influence of stray capacitance, etc.
There is a problem that the variable range naturally has a limit, and accordingly, the matching range also has a limit.

[0007] An object of the present invention is to provide an impedance matching circuit having a wide matching range by adding a simple circuit to the above-described conventional impedance matching circuit.

[0008]

An impedance matching circuit according to the present invention comprises a series reactance element between an L-type impedance matching circuit connected to a signal source and comprising a variable capacitor and a variable inductance, and a load whose impedance varies widely. And an impedance conversion circuit comprising a parallel reactance element is provided.

The series reactance element of the impedance conversion circuit according to claim 1, wherein the series reactance element and the parallel reactance element of the impedance conversion circuit are configured to be independently turned on / off by a relay. The element and the parallel reactance element are characterized in that a plurality of elements having different set values are switched by a switch.

[0010]

FIG. 1 shows an embodiment of an impedance matching circuit according to the present invention. A series reactance element Xs and a parallel reactance element are provided on the load side of the conventional L-type impedance matching circuit 1 shown in FIG. This is provided with an impedance conversion circuit 5 composed of an element Xp.

The matching range of the impedance matching circuit of the present invention will be described. First, when the matching range in the conventional L-type impedance matching circuit 1 is inside the symbols A, B, C, and D shown on the characteristic diagram of the matching range in FIG. 2, outside the symbols A, B, C, and D Load side impedance Z
x and the impedance Zo on the signal source side, the reactance element Xs
And Xp, the impedance is once converted to the impedance Z2 inside the symbols A, B, C and D. Next, the impedance Z2 is matched to the impedance Xo on the signal source side by changing the variable capacitor 2 and the variable coil 3 of the L-type impedance matching circuit 1.

The impedance matching in the impedance matching circuit of the present invention is adjusted in the order of Zx → Z1 → Z2 → Z3 → Zo of the impedance symbol shown in FIG. , And Z 2 → Z 3 → Zo is adjusted by the impedance matching circuit 1.

As described above, in the impedance conversion circuit of the present invention, the impedance Zx on the load side is represented by the symbols A, B,
Since the impedance may be set to any one of the ranges of C and D, it is not necessary to convert the impedance to a precise value, and the constants of the reactance elements Xs and Xp are changed according to the value of the impedance Zx on the load side. Only a few steps need to be switched.

FIG. 3 is a circuit diagram showing a specific example of the present invention. The impedance conversion circuit 51 shown in FIG.
Xs by ₁ and k _2, is configured to turn on / off as required Xp, impedance conversion circuit 5 (B)
Reference numeral 2 denotes a configuration in which reactance elements having different set values are switched by the switches S ₁ and S ₂ .

[0015]

As described above, according to the present invention, the conventional L
By adding a simple impedance conversion circuit to the type impedance matching circuit, the matching range can be expanded as compared with the conventional L type impedance matching circuit, and the adjustment for the matching is also precise. It can be easily done without being required. Further, since it can be composed of relatively small components, the impact on physical conditions such as the dimensions of the impedance matching circuit is extremely small.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the impedance matching circuit of the present invention.

FIG. 2 is an explanatory diagram of an impedance matching adjustment process of the impedance matching circuit of FIG. 1;

FIG. 3 is a circuit diagram showing a specific example of the present invention.

FIG. 4 is a circuit diagram showing an example of a conventional impedance matching circuit.

FIG. 5 is a characteristic diagram showing a theoretical value of a matching range of the impedance matching circuit of FIG. 4;

FIG. 6 is a circuit diagram showing another example of a conventional impedance matching circuit.

7 is a characteristic diagram showing a theoretical value of a matching range of the impedance matching circuit of FIG.

[Explanation of symbols]

 1,4 Impedance matching circuit 2 Variable capacitor 3 Variable coil 5,51,52 Impedance conversion circuit Xs, Xp Reactance element

Claims (3)

[Claims] 1. An impedance conversion circuit comprising a series reactance element and a parallel reactance element is provided between an L-type impedance matching circuit connected to a signal source and comprising a variable capacitor and a variable inductance, and a load having a widely varying impedance. An impedance matching circuit characterized in that: 2. The impedance matching circuit according to claim 1, wherein the series reactance element and the parallel reactance element of the impedance conversion circuit are configured to be independently turned on / off by a relay. 3. The impedance reacting circuit according to claim 1, wherein the series reactance element and the parallel reactance element are configured to switch a plurality of elements having different set values by switches. Impedance matching circuit.