JPH0646712B2 - Automatic antenna tuner - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an automatic antenna tuner which is inserted in the middle of an antenna and a transmitter output part of a wireless communication device to perform impedance matching.

[Prior art]

Conventionally, in wireless communication devices, except for the handy type, the antenna is installed at a high place where it is convenient to radiate radio waves or outdoors, so it is convenient to connect it to the transmitter with a feeder of several meters to several tens of meters. The output of the transmitter and the impedances of the feeder and antenna were matched.

Means to be Solved by the Invention

However, if only the feeder is matched, in addition to the ohmic loss and the dielectric loss of the feeder, the more the characteristic impedance of the connection part is different, the more the reflection of the radio wave becomes large. By inserting an impedance matching device in the middle, practically it is done by changing the constant of the element of the low-pass filter or band-pass filter. Normally, the tap of the coil is switched to select the band, and the impedance is set by the capacitor (varicon). Be consistent. (Maximum output or minimum SWR) has the effect of minimizing transmission loss and suppressing harmonics, and is called an antenna matching device or antenna tuner. As is clear from the above, it is desirable to insert the antenna matching device into the connecting portion between the feeder and the antenna, but since it is inconvenient to adjust the position locally, automatic antenna tuners that do not require adjustment are commercially available. There are roughly two types. One is that the band setting is manually switched and the fine adjustment within the band is automated, and the other is that the band setting is sparsely adjusted by incorporating the band information on the transmitter side ( (The band switching, etc.) is performed, and the fine adjustment within the band is automated.If the former is semi-automatic, the latter is fully automatic and has a wide range of application, but the transmitter sends band information to the antenna tuner. However, in the current situation where there is no uniform standard for transmission of band information, the fully automatic antenna tuner can be used together with the transmitter. There was an inconvenience that it was designed together and limited as a system.

[Means for Solving the Problems]

The present invention is intended to solve the above-mentioned problems, and is a method for automatically setting the information necessary for automatic band setting in a fully automatic antenna tuner to the optimum band by judging from the transmitted radio waves, It is a fully automatic antenna tuner with a wide adaptation range, which replaces the conventional antenna tuner that requires system design with the transmitter.

【Example】

An embodiment of the present invention will be described with reference to the drawings. In an antenna tuner that performs impedance matching inserted between the transmitter output section and the antenna, the voltage value obtained by frequency / voltage (hereinafter referred to as f / v) conversion of the transmission wave input to the antenna tuner This is an automatic antenna tuner that determines the adaptive band of the antenna tuner and automatically sets the band of the antenna tuner.
The outline of FIG. 1 will be described below. In the figure, 1 is a transmitter, 2 is an antenna, and 3 is an automatic antenna tuner unit 3 according to the present invention. In this circuit, the coil 31, the capacitors 32 and 33 form a π matching circuit. When the input side impedance and the output side impedance are equal, the capacitance values of the capacitors 32 and 33 are equal, but when the impedances (for example, 50 ohm) are different,
Impedance matching can be performed by changing the capacitance values on the input side and the output side, and since it is basically a low-pass filter type configuration, it also has the effect of suppressing high frequencies. The circuit impedance matching is indirectly confirmed by the SWR (standing wave ratio) meter 35 that is inserted in series with the transmission line. The definition of the SWR and the circuit impedance matching method using the automatic SWR meter are well known to those skilled in the art, and the description thereof is omitted because it is outside the scope of the present invention, but the SWR in the impedance matching state is omitted.
Is 1, and the SWR value increases as the matching is lost. Therefore, it is usually desirable that the SWR value of the antenna circuit be 1.3 or less, and often up to about 1.5. It is possible to match an antenna 1.3 or less whose value is about 2 to 3. Therefore, for the operation in the single band, as described above, it is only necessary to operate one impedance matching circuit, but in the HF band, the VHF band and the UHF band for the amateur communication device, the 1.9 MHz band or 28MHz band, or 50
There are multi-band machines that compose frequency bands such as the MHz band, 144 MHz band, and 430 MHz band, and antennas for multiple bands are also manufactured according to their respective purposes. Therefore, the antenna tuner also needs to be compatible with the communication device. Therefore, the tap of the coil 31 is switched by the switch 34 for adjustment, and the capacitor (varicon) 3
By finely adjusting 2 and 33 so that the SWR value is minimized, the antenna tuner can have multiple bands. Further, regarding coarse adjustment of band setting, in the present invention, the transmission radio wave 11 is converted into a voltage having a correlation with the frequency by the f / v converter 36, and the band is determined based on the voltage value. Is the output of the f / v converter 36 and the upper end reference voltage of the preset band,
The band in the middle of the lower end reference voltage is selected. The frequency bands used in so-called amateur radio are spaced apart as shown in FIG. 3, and the frequencies that can be used are extremely narrow. If the output voltage of the f / v converter 36 is not so accurate, the band determination will not be hindered. Therefore, the f / v converter 36 does not need a highly accurate digital conversion system, and can be practically used even if it is configured by a simpler analog conversion system. When the band is determined by the functions of the above circuits, the output voltage is applied to the switching circuit 38, and the switch 34 is operated.
Is set to a fixed band position. In the case of two or more bands, a combination of a rotary switch and a rotary magnet, or a relay switch is used to improve convenience. In addition, the transmission carrier detection circuit 39 is
Since the / v conversion output becomes 0, and the band determination is determined to be the lowest band, when the transmission carrier detection is 0, the switching control circuit 38 is locked and the band is switched to meaningless. To prevent. Next, explaining the outline with reference to FIG. 2, A is f
/ V converter, B is a band determination circuit, C is a switching control circuit,
D is a transmission carrier detection circuit. In the f / v converter A , the output voltage of the contact a with the resistor R _{1 and the} resistor R ₂ is a value obtained by dividing the input voltage by R ₁ and R ₂ regardless of the frequency, but the output voltage at the point b is If X is an inductance, it will increase / decrease in inverse proportion to the frequency, and if it is capacitance, it will increase / decrease in proportion to the frequency. Therefore, the frequency at which the voltage at point a and the voltage at point b match is f / v converted to the desired frequency. If set to the upper or lower limit of the band, the output voltage between a and b can be obtained as a change proportional or inversely proportional to the frequency, and points a and b are the diagonal points of the bridge circuit. because there is,
It can be considered that the output voltage between a and b is independent of the input voltage in the practical range and depends only on the frequency. However, it is inconvenient to handle with high frequency voltage, so diode
It is rectified by D ₁ and D ₂ into a DC voltage, and in addition to the input of the differential amplifier Q ₁ , a DC voltage V ₀ between a and b is output. Also, the third
The figure is a graph for explaining the relationship between the input frequency and the output voltage of the f / v converter, and f / v is shown by a straight line, but it is not necessarily a straight line for the purpose of the present invention. Next, the band determination circuit B has a configuration capable of determining three bands in accordance with the antenna for three bands, and the band reference voltages V ₁ and V ₂ are set by the three variable resistors VR ₁ , VR ₂ and VR _3. If the f / v output voltage V ₀ is smaller than the voltage V _{1 at} the contact point of VR ₁ and V ₂ (A) band, if it is between the voltage V _{2 at} the contact point of VR ₂ and VR ₃ and the V ₁ ( B) Band, and the V
A is to determine larger than ₂ and (C) band, the comparison of the voltage is performed by the direct current voltage comparator Q ₂ · Q _3, wherein Q ₂ ·
When Q ₃ is positively fed back by R ₁ and R ₂ to have a hysteresis in the output voltage value, when V ₀ and the return voltage are close to each other for applications other than amateur radio, an unstable phenomenon near the band switching point Has the effect of excluding. Next, in the switching control circuit C , Q ₄ , Q ₅ , and Q ₆ are exclusive OR.
A gate, outputs and H level Q ₄ are Q _2, Q ₅ by inputting the output and L level of the output and Q ₃ of Q _2, band I
The output of Q ₄ is H at the time of input in, the output of Q ₅ is H at the time of input in band II, and Q at the time of input in band III.
The output of ₆ becomes H (the others are L), and the electronic switches Q ₇ , Q
By driving the relays RL ₁ , RL _{2 and} RL ₃ via ₈ and Q ₉ , the coil 31 (Fig. I) of the π matching circuit is switched to perform the coarse adjustment of the band setting. It looks like Figure 4. Relays RL ₁ , RL ₂ , RL ₃ latch type, when L ₁ is energized, the contact is held in break (release), and when L ₂ is energized, contact is held in make (contact) and the energization is stopped. However, the contact state is still latched. In addition, L ₂ performs a make operation of a required band by Q ₇ , Q ₈ and Q ₉ collector currents, and an unnecessary band is energized to L ₁ through a matrix circuit of six diodes D to be in a break state. Next, the transmission carrier detecting circuit D is the conduction bias added to the transistor Q ₁₀ in DC voltage clear stream of carrier by diodes D _1, D _2, has a switching transistor Q ₁₁ of the relay power supply circuit to ON. Also, Q ₁₁ when there is no carrier input becomes OFF so as not to relay operation.

【The invention's effect】

The automatic antenna tuner of the present invention has an automatic band selection switching function so as to support a plurality of frequency bands,
Moreover, since it does not require any special means for transmitting band information from the transmitter, it not only has the convenience of not having to install the antenna tuner, but it does not require system design with the transmitter, and it is a universal automatic antenna tuner. Therefore, it is convenient to commercialize it independently. In the present invention, the f / v converter is used to determine the band frequency of the transmitted radio wave. However, as shown in the embodiment, an extremely simple circuit configuration provides a sufficiently practical result that the band frequency range is Since the setting can be obtained only by adjusting the DC band reference voltage, the adaptive frequency band can be easily set or changed.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the present invention. FIG. 2 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is an explanatory diagram of the band determination operation. FIG. 4 is an explanatory chart of band setting operation. 1 transmitter 2 antenna 3 automatic antenna tuner 31 coil 32, 33 variable capacitor 34 band setting switch 35 SWR 36. A f / v converter 37. B band judgment circuit 38. C switching control circuit 39. D transmission carrier detection circuit Q ₁ differential amplifier Q _{2, Q 3} dc voltage comparator Q _4, to Q ₆ exclusive OR gate Q ₇ to Q ₁₁ switching transistor RL ₁ ~RL ₃ latch type relay

Claims (1)

[Claims] 1. A π type in which a coil having a switching tap for each band inserted between the output part of a transmitter and an antenna and a variable capacitance element for impedance matching the front and rear of the coil with a control signal based on a SWR signal are grounded. In an antenna tuner composed of a matching circuit, a band voltage is determined by comparing the voltage from the frequency voltage converter that converts the frequency of the transmitted wave input to the antenna with the voltage from the frequency voltage converter and the reference voltage, and determine the band signal. Tap selection means in which a band determination circuit for outputting and a switching control circuit for inputting a band signal output from the band determination circuit and performing tap switching setting of the corresponding coil are connected in cascade,
A transmission carrier detection circuit that supplies drive power to the switching control circuit when a carrier of the transmission wave is detected is provided in parallel with the antenna tuner. When the transmission wave from the transmitter is input, the transmission carrier is input to the switching control circuit. The drive power is supplied from the detection circuit and switched to the tap of the coil corresponding to the band signal judged by the band judgment circuit. If the transmission wave is not input, the drive power from the transmission carrier detection circuit is supplied to the switching circuit. The automatic antenna tuner is characterized in that the tap that has already been set is held and locked.