JPH0448287B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic tuning device provided between a signal source such as a transmitter and a load such as an antenna.

[Prior Art] A circuit shown in FIG. 6 is conventionally known as a circuit for impedance matching between a transmitter and an antenna.

This circuit includes a pair of variable inductors 3 and 4 connected between a transmitter 1 and an antenna 2 through a so-called π-type connection.
and a pair of capacitors 5 and 6, which constitutes a tuning circuit section for tuning the transmission line by means of a parallel resonant circuit formed by the variable inductor 3 and capacitor 5 on the transmitter 1 side.
A parallel resonant circuit including a variable inductor 4 and a capacitor 6 on the side constitutes a matching circuit section for impedance matching between the signal source 1 side and the antenna 2 side.

The variable inductor 3 in the tuning circuit section is automatically varied by an automatic tracking circuit provided on the transmitter 1 side based on the amount of phase shift between the voltage and current on the transmission line, and the impedance on the antenna 2 side is changed. It has come to be controlled by following the That is, this automatic tracking circuit includes a voltage phase detector 7 that detects the voltage phase of the oscillation output signal from the signal source 1.
, a current phase detector 8 that detects the current phase of this oscillation output signal, and a phase comparator 9 that detects the phase difference between the voltage and current of the oscillation output signal based on the detection signals of these phase detectors 7 and 8. , a rotator 10 that mechanically variably controls the variable inductor 3, and a controller 11 that controls the rotator 10 based on the voltage output of the phase comparator 9, and transmits the variable inductor 3. Automatically variable control is performed in the direction of zeroing the reactance component of the impedance on the line.

On the other hand, the variable inductor 4 on the matching circuit side is varied by manual operation or the like, and adjusted so that the output of the antenna 2 is maximized. That is, when adjusting the matching circuit section, the above-mentioned automatic follow-up circuit is activated to maintain the tuned state on the transmission line against impedance fluctuations on the matching circuit section side.

[Problems to be Solved by the Invention] By the way, in the prior art as described above, the reactance value X _L1 of the variable inductor 3 in the tuned circuit section is equal to the reactance value of the capacitor 5.
_If X _C1 is the impedance value when looking at the load side from _point A on the transmission line ^is R ₁ + jX ₁ , then X _L1 = - (2X ₁ + X _C1 ) ± ^√ is given by

Therefore, from this relationship, for example, as shown by the Smith Chart in Figure 7, the impedance locus C _p seen from point B on the transmission line toward the load side is the base line showing that the Smith Chart reactance component is zero. D may intersect with two points a and b, resulting in two tuning points a and b.

However, in the above-mentioned automatic tracking circuit, the phase difference between the voltage and current of the oscillation output signal, that is, the reactance component, is determined to be inductive (above the base line D) or capacitive (below the base line D). 10
This uniquely determines the driving method of the variable reactance 3, that is, the variable direction of the variable reactance 3. Therefore, when there are two tuning points a and b as described above, the variable direction of the variable inductor 3 is opposite to the tuning point. Areas that tend to occur may occur. In other words, in the trajectory C _p , the points between point c on one end side and tuning point a, and between the point d on the other end side and tuning point b are both capacitive in the illustrated example, so one side If the direction of variation from point c to point a is the proper tuning direction (direction of arrow α ₁ in the figure), the same direction of variation will be obtained between point d and point b (direction of arrow α ₂ in the figure), Since the variable inductor 3 is controlled in a direction away from the tuning point, automatic tuning becomes impossible in this region. Therefore, in such a conventional circuit, there is a problem in that there is a region where automatic tuning is impossible depending on the load side conditions, and the follow-up range of automatic tuning is correspondingly narrowed.

In addition, as can be seen from the example shown in the figure, the point e where the standing wave ratio (hereinafter referred to as VSWR) indicating the matching state is minimum on the trajectory C _p does not coincide with the tuning points a and b. For example, it is difficult to perform control to obtain the optimum matching point by detecting the minimum value of VSWR, and the matching adjustment is complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic tuning device that can easily perform reliable tuning and matching and can obtain a wide tracking range.

[Means for Solving the Problems] That is, in order to solve the above-mentioned problems, the automatic tuning device of the present invention is provided on a transmission line between a signal source and a load, and is connected in series with the signal source. The transmission line is tuned by automatically adjusting the variable reactance of the tuned tuning circuit section using an automatic tracking circuit, and by adjusting the variable reactance of the matching circuit section provided at the output stage of this tuning circuit section. , in an automatic tuning device for impedance matching between a signal source and a load; the automatic tracking circuit includes a voltage phase detector that detects the voltage phase of the output signal from the signal source, and a voltage phase detector that detects the current phase of the output signal. a phase comparator that detects the phase difference between the voltage and current of the output signal based on the detection signal of each of the phase detectors, and a driver that varies the variable reactance of the tuned circuit section; a controller that controls the driver based on the output of the phase comparator; the tuning circuit section includes a variable reactance made of a variable inductor or a variable capacitor, and a variable reactance in parallel with the variable reactance of the matching circuit section. It is characterized by being constructed from a series resonant circuit with a capacitor.

[Operation] When the automatic tracking circuit variably controls the variable reactance of the tuned circuit section based on the phase difference between the voltage and current of the output signal, the impedance on the transmission line changes only the reactance component while the resistance component remains constant. Therefore, tuning is completed at the point where the reactance component becomes zero. Then, in this automatic tracking state, the variable reactance of the matching circuit section is varied,
Performs impedance matching between the signal source and the load.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

The impedance matching circuit in this embodiment performs impedance matching between the transmitter 12 and the antenna 13, and is a series resonant circuit configured by sequentially connecting a variable inductor 14 and a capacitor 15 to the transmitter 12 in series. and a matching circuit section including a variable inductor 16 connected in series to the antenna 13 from a connection point between the variable inductor 14 and the capacitor 15.

With this configuration, the tuning circuit section and the matching circuit section form a T-type connected low-pass filter, and
High frequency components generated by the transmitter 12 can be removed.

By the way, in such a transmitting circuit, when matching the impedance on the antenna 13 side to the characteristic impedance Z _p of the transmitter 12, when the reactance value of the variable inductor 16 is X _L2 , the load side impedance at point A on the transmission line is value R <sub>1
+ j _</sub>
4's reactance value is X _L1 , the load-side impedance at point B on the transmission line is R ₁ + j (X ₁ + X _L1 . Therefore, X ₁ + X _L1 = 0, that is, X _L1 = -X ₁ . Tuning is performed by varying X _L1 as shown.

At this time, the load side impedance at point B on the transmission line is only the resistance component _R1 ,
The VSWR at point B on the transmission line for a certain reactance value of the variable inductor 16 is minimum. Therefore, while maintaining the reactance value of the variable inductor 14 at only the resistance R ₁ by the automatic tracking circuit, the variable inductor 16 is controlled in the direction of decreasing the VSWR, and VSWR = 1 (Z _p = R ₁ ). Impedance matching can be completed in a relaxed state.

In this embodiment, based on the above principle, the variable inductor 14 in the tuning circuit section is controlled by an automatic tracking circuit, and the variable inductor 16 in the matching circuit section is controlled.
By operating based on the VSWR detector 24 and the VSWR indicator 25, the transmitter 12 and the antenna 1
3 and impedance matching between the two.

That is, since the tuned circuit section and the matching circuit section together form a T-type connected low-pass filter, the tuned circuit section becomes one tuning point, and
This means that the impedance matching of the matching circuit section can be performed separately and reliably.

Each component will be explained in turn below.

The tuning circuit unit makes the reactance component of the load-side impedance at point B on the transmission line zero by varying the inductive reactance of the variable inductor 14 with respect to the capacitive reactance of the capacitor 15, thereby adjusting the tuning on the transmission line. It is something to take. By the way, the transmitter 1 in this embodiment
No. 2 uses a power transistor in the output stage, and its transmission line has low impedance as a whole. Therefore, the tuning circuit section can also be configured as a series resonant circuit without a capacitor provided at the input stage of the variable inductor 14.

The automatic tracking circuit that controls the variable inductor 14 of the tuned circuit section includes a voltage phase detector 17 that detects the voltage phase of the oscillation output signal from the signal source 12, and a voltage phase detector 17 that detects the current phase of the oscillation output signal. current phase detector 18 and these phase detectors 1
a phase comparator 19 that detects the phase difference between the voltage and current of the oscillation output signal based on the detection signals of 7 and 18;
, a rotator 20 that is a driver that mechanically and variably controls the variable inductor 14, and a controller 21 that controls the rotator 20 based on the voltage output of the phase comparator 19. The inductor 14 is automatically variably controlled in a direction that makes the reactance component of the impedance on the transmission line zero. Note that the means for driving the variable inductor 14 is not limited to the rotator 20, and various methods such as a slide drive may be employed.

FIG. 2 is a Smith chart showing a locus C ₁ of impedance change viewed from point B on the transmission line to the load side based on such variable control of the variable inductor 14. As can be seen from this figure, the load side impedance is kept constant by changing the variable inductor 14, and only the reactance component increases or decreases, and the tuning point f, that is, the reactance component becomes zero, and the trajectory C ₁ At the point where VSWR intersects the baseline D, VSWR takes the minimum value on the locus _C1 .

The matching circuit section includes a parallel resonant circuit including a variable inductor 16 and a capacitor 15 in the preceding stage, and a parallel circuit including a plurality of stages of inductors 22 and capacitors 23 provided after the variable inductor 16 (in the illustrated example, one stage is used). (provided only)
It is composed of.

Further, on the output stage side of the transmitter 12, a VSWR detector 24 and a VSWR indicator 25 are provided for monitoring the matching state. In this example,
VSWR based on detection by VSWR detector 24
Based on the VSWR value displayed by the indicator 25, impedance matching between the transmitter 12 and the antenna 13 is performed by manually operating the variable inductor 16 in a direction in which the VSWR value becomes smaller. In other words, when the value of VSWR becomes 1,
Since the characteristic impedance of the transmitter 12 and the impedance on the side of the antenna 13 match, matching adjustment is performed by controlling the variable inductor 16 to maintain this state. The variable inductor 16 due to this matching adjustment
The above-mentioned automatic follow-up circuit operates in response to reactance fluctuations, and automatically controls the variable inductor 14 to maintain the tuned state on the transmission line.
Therefore, in this matching operation, the load-side impedance located at point f of the Smith Chart mentioned above changes only by the resistance and moves on the base line D, and is displaced to point g where VSWR becomes 1. It turns out.

As described above, in this embodiment, when the automatic tracking circuit operates for variable control of the variable inductor 16 for matching, the tuning point f is always located on the impedance locus C ₁ by the tuning circuit section based on series resonance.
Since the VSWR has the characteristic of minimizing the value, it is sufficient to keep this automatic tracking circuit operating and vary the variable inductor 16 for matching in the direction of decreasing the VSWR, and the matching adjustment can be performed extremely reliably and easily. be able to.

In addition, in the tuning device of this embodiment, when the automatic tracking circuit performs tuning control, the locus C ₁ of the load side impedance passes on a concentric circle with a constant resistance value, and there is only one tuning point. , the variable direction of the variable inductor 14 by the automatic tracking circuit can always be determined by determining whether it is capacitive or inductive. Therefore, unlike the conventional case shown in FIG. 7, there is no region where tracking is not possible, and a wide tracking range can be obtained.

Further, in the above embodiment, a configuration was described in which the variable inductor 16 for matching is manually operated based on the value of VSWR, but for example, as shown in FIG. Variable inductor 1 for identification and automatic matching
6 may also be configured.

In this example, when tuning by the automatic tracking circuit,
A memory device 26 stores the value of VSWR as appropriate, and the value of VSWR is compared with the variable inductor 1.
Arithmetic unit 27 that determines the variable direction and variable amount of 6.
, a rotator 28 that mechanically variably controls the variable inductor 16 , and a controller 29 that drives and controls the rotator 28 based on the calculation output of the calculation device 27 .

In this matching circuit, the detection value of the VSWR detector 24 is
After storing VS ₁ in the storage device 26, the variable inductor 16 is varied by a certain amount in a predetermined direction, and when tuning is performed again by the automatic tracking circuit.
The detected value VS ₂ of the VSWR detector 24 is stored in the storage device 26.
to be memorized. Then, these two detected values VS ₁ and
The magnitude of VS ₂ is determined by the arithmetic unit 27, and the variable inductor 16 is controlled based on this result,
The matching adjustment is completed when VS _o =1. This allows for fully automatic alignment adjustment.

Further, in the above embodiment, the variable inductor 14 was used as the variable reactance element of the tuned circuit section, but as shown in FIG. Alternatively, as shown in FIG. 5, the tuning circuit section may be configured with a series resonant circuit including a variable capacitor 33, an inductor 34, and a capacitor 35. In these modified examples of each of the embodiments shown in FIGS. 4 and 5, the tuning circuit section and the matching circuit section form a T-connected bandpass filter, similar to the embodiments described above. , transmitter 12
In addition to eliminating high frequency components, the tuning of the tuning circuit section and the matching of the matching circuit section can be performed separately and reliably. In this case, since tuning is achieved by variable control of the variable capacitors 30 and 33, the other capacitors 32 and 35 and the inductor 34 are set in advance so that the tuning circuit section as a whole has inductive reactance. .

In addition, in the embodiment described above, the detection of the matching state is
Although this is performed using the VSWR detector 24, for example, if the output of the signal source is constant, a similar matching operation can be performed using a reflected power detector or its indicator. Note that in this case, the optimum matching state is achieved when the reflected power is zero.

Furthermore, instead of such a VSWR detector 24 or a reflected power detector, a resistance value detector or its indicator may be used to detect the matching state. In other words, this is possible on the condition that the above-mentioned automatic tracking circuit properly performs tuning control so that the load-side impedance is only a resistance component, and when the resistance value and the characteristic impedance match, Optimal consistency is reached.

[Effects of the Invention] As explained above, according to the present invention, since the tuned circuit section is configured by a series resonant circuit,
Reliable tuning control can be performed by the automatic tracking device, and along with this, impedance matching becomes easy and a wide tracking range can be obtained.

In addition, the tuning circuit section and the matching circuit section are so-called T
Since it is configured with a low-pass filter or a band-pass filter using type connection, the following effects can be obtained.

High frequency components generated by the transmitter can be removed.

Even when a power transistor is used in the output stage of the transmitter, impedance matching can be performed without using a tap-up transformer.

Since there is only one tuning point in the tuning circuit section, tuning can be achieved automatically and reliably by simply varying the variable inductance.

In addition, the matching circuit unit is configured to match the characteristic impedance of the transmitter and the impedance of the antenna, and the matching is adjusted so that the variable inductance is reduced until the value of VSWR becomes 1. Since the matching adjustment is performed based on the output of the automatic tracking circuit in which the reactance component on the transmission line becomes zero, that is, at the time of tuning, reliable matching can be achieved.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a Smith Chart explaining the action of tuning control in the same embodiment, FIG. 3 is a circuit diagram showing another embodiment of the invention, and FIG. 4 is a tuning circuit section in still another embodiment of the invention. A circuit diagram, FIG. 5 is a circuit diagram showing a tuning circuit section in yet another embodiment of the present invention, and FIG. 6 is a circuit diagram showing an example of the conventional technology.
FIG. 7 is a Smith chart illustrating the operation of the prior art tuning control shown in FIG. 6. 12... Transmitter (signal source), 13... Antenna (load), 14... Variable inductor for tuning, 1
5, 32, 35... Capacitor, 16... Variable inductor for matching, 17... Voltage phase detector, 1
8... Current phase detector, 19... Phase comparator, 2
0... Rotator, 21... Controller, 30, 33...
Variable capacitor for tuning.

Claims (1)

[Claims] 1. Provided on a transmission line between a signal source and a load,
The automatic tracking circuit automatically adjusts the variable reactance of the tuned circuit connected in series with the above signal source to achieve tuning on the transmission line, and the output stage of the tuned circuit is controlled by the output of the matching state detector. In an automatic tuning device for performing impedance matching between a signal source and a load by adjusting the variable reactance of a matching circuit section provided; a phase detector 17 and a current phase detector 1 that detects the current phase of the output signal
8, a phase comparator 19 that detects the phase difference between the voltage and current of the output signal based on the detection signals of the phase detectors 17 and 18, and variable reactances 14, 30, and 33 of the tuned circuit section. and a controller 21 that controls the driver based on the output of the phase comparator; the tuning circuit section and the matching circuit section receive the output signal from one end and input the output signal from the other end. and a second variable reactance 1 whose one end is connected to the other end of the first variable reactance and the other end is connected to the load 13.
6, and a third reactance 15, one end of which is connected to the other end of the first variable reactance, and the other end of which is connected to the reference power source of the automatic tracking circuit. Moreover, the tuning circuit section is composed of the variable inductor 14 or the variable capacitors 30, 33, which is the first variable reactance, and the capacitor 15, which is the third reactance, and the matching circuit section is configured to perform the phase comparison. a variable inductor 16, which is a second variable reactance that varies based on the output of the matching state detector 24;
and a capacitor 15 which is a third reactance. 2 The matching circuit unit has a second
is the variable reactance of variable inductor 16
and capacitor 15, which is the third reactance.
, a first detection value (VS1) of the matching state detector during the first tuning of the automatic tracking circuit, and a second detection value of the matching state detector during the second tuning of the automatic tracking circuit. A storage device 26 that stores the value (VS2), an arithmetic device 27 that compares the first detected value and the second detected value, and a driver 28 that drives the variable inductor 16 using the output of the arithmetic device.
2. The automatic tuning device according to claim 1, further comprising: a controller 29 for driving and controlling the driver according to an output from an arithmetic unit.