JP2727769B2 - Automatic tuning device for bandpass filters. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center frequency (hereinafter simply referred to as "center frequency") of a signal pass band of a band-pass filter, which is used as a reference signal input from an external device or output from a built-in signal generator. The present invention relates to an automatic tuning device for a bandpass filter that automatically tunes to a frequency.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram of a conventional example of an automatic tuning type band-pass filter proposed in Japanese Patent Application Laid-Open No. 1-105601.

[0003] In FIG. 10, a conventional automatic tuning type band-pass filter passes an input high-frequency signal in one direction and has an isolator 101 having a reflected power coupling terminal 111, and a high-frequency signal passing through the isolator 101. , Which operates as a band-pass filter for band-pass filtering, and a resonator 102 by moving a resonance frequency adjusting element (not shown) in the resonator 102.
And a control circuit 10 for detecting a high-frequency signal output from the reflected power coupling element 111 of the isolator 101 by the diode D1, and controlling the drive mechanism 103 based on the detected signal.
4 is provided.

In this automatic tuning type band-pass filter, when a certain high-frequency signal is passed through the band-pass filter, the high-frequency signal of the reflected power detected by the diode D1 (hereinafter referred to as a reflected signal). The control circuit 104 controls the driving mechanism 103 based on the reflected signal so that the level of the reflected signal is minimized, utilizing the fact that the level is minimized at the resonance frequency of the resonator 102. Thereby, the resonator 102
Can be tuned to the frequency of the high-frequency signal passing through the isolator 101.

[0005]

However, in the above-mentioned conventional automatic tuning band-pass filter, the resonator 10
Since the above-mentioned tuning operation is performed by utilizing the fact that the level of the reflected signal is minimized at the resonance frequency of 2, for example, when the automatic tuning type band-pass filter of FIG. When the sneak signal is input to the automatic tuning type band-pass filter, there is a problem that the tuning operation cannot be performed accurately.

A first object of the present invention is to solve the above-mentioned problems and to tune the center frequency of the band-pass filter to the frequency of the reference signal with better accuracy than the conventional example. To provide an automatic tuning device.

A second object of the present invention is to provide an automatic tuning type band-pass filter which can tune the center frequency of the band-pass filter to the frequency of the reference signal with better accuracy than the conventional example. It is in.

Further, a third object of the present invention is to provide an automatic tuning type band pass filter, in which, for example, when an automatic tuning type band pass filter is used in an antenna sharing device, a wraparound signal from another channel is input to the automatic tuning type band pass filter. Even if
An object of the present invention is to provide an antenna sharing device including a plurality of automatic tuning type band-pass filters capable of performing the tuning operation accurately.

[0009]

According to a first aspect of the present invention, there is provided an automatic tuning apparatus for a band-pass filter, comprising a predetermined reference signal and a band-pass filter capable of changing a center frequency. Mixing means for mixing and multiplying a signal output from the band-pass filter by passing through the band-pass filter when a signal is input and outputting a signal of a multiplication result; and a multiplication result output from the mixing means. Low-pass filtering means for filtering the DC component signal of the signal, and the center frequency of the band-pass filter is set to the frequency of the reference signal based on the DC component signal output from the low-pass filtering means. Control means for controlling the band-pass filter so as to coincide with each other.

According to a second aspect of the present invention, in the automatic tuning apparatus according to the first aspect, the reference signal is a signal input from an external device, and the automatic tuning apparatus further includes the band-pass filter. A first coupling unit that extracts a part of the reference signal input to the band-pass filter and that outputs the reference signal to the mixing unit; and when the reference signal is input to the band-pass filter, the band-pass filter passes the band-pass filter. A second coupling means for extracting a part of the output signal and outputting the extracted signal to the mixing means.

Further, the automatic tuning device according to claim 3 is
2. The automatic tuning apparatus according to claim 1, wherein said automatic tuning apparatus further generates a reference signal and outputs the reference signal to said mixing means, and extracts a part of the reference signal generated by said generating means, and extracts said band signal. Third coupling means for outputting to the filter, and fourth coupling means for extracting a part of a signal that passes through the band-pass filter and is output from the band-pass filter and outputs the extracted signal to the mixing means. Features.

The automatic tuning apparatus according to a fourth aspect of the present invention is the automatic tuning apparatus according to the third aspect, wherein the automatic tuning apparatus further comprises input means for inputting a center frequency to be set by the band-pass filter. The control means includes:
On the basis of the center frequency to be set inputted by the input means, the generation means is controlled to generate a reference signal having the center frequency to be set.

According to a fifth aspect of the present invention, in the automatic tuning apparatus according to the third aspect, the automatic tuning apparatus further receives information on a center frequency to be set by the band-pass filter from an external device. Receiving means, wherein the control means controls the generating means to generate a reference signal having the center frequency to be set based on the center frequency to be set received by the receiving means. And

Further, the automatic tuning apparatus according to claim 6 is
6. The automatic tuning apparatus according to claim 1, wherein the band-pass filter includes a resonator, and the control unit is configured to perform control based on a DC component signal output from the low-pass filtering unit. A resonance frequency of the resonator is calculated, and the band-pass filter is controlled based on the calculated resonance frequency such that a center frequency of the band-pass filter matches a frequency of the reference signal.

Still further, an automatic tuning type band pass filter according to claim 7 is a band pass filter according to claim 1, 2, 3, 4, 5 or 6, and a band pass filter according to claim 1, 2, 3, 4, 5 or 6. Or an automatic tuning device according to item 6.

Further, an antenna sharing apparatus according to claim 8 is provided with a plurality of automatic tuning band-pass filters according to claim 7, and is provided in each of the plurality of automatic tuning band-pass filters. Each output terminal for outputting a signal output from each band-pass filter described in 1, 2, 3, 4, 5, or 6 is electrically connected together.

[0017]

In the automatic tuning apparatus for a band-pass filter according to claim 1, the mixing means comprises a band-pass filter capable of changing a predetermined reference signal and a center frequency. After inputting the reference signal to the above, after passing through the band-pass filter and mixing and multiplying the signal output from the band-pass filter to output a multiplication result signal, the low-pass filtering means includes: The DC component signal of the multiplication result signal output from the mixing means is filtered. Next, the control means controls the band-pass filter based on the DC component signal output from the low-pass filtering means such that the center frequency of the band-pass filter matches the frequency of the reference signal. As a result, the center frequency of the band-pass filter can be matched with the frequency of the reference signal and tuned (hereinafter referred to as a tuning operation) with a simple circuit configuration and with better accuracy than the conventional example.

Preferably, the reference signal is a signal input from an external device, and the automatic tuning device further includes a reference signal input to the band-pass filter. A first coupling means for extracting a part of the signal and outputting the signal to the mixing means; and a signal output from the band-pass filter after passing through the band-pass filter when the reference signal is input to the band-pass filter. Second combining means for taking out the part and outputting the taken out part to the mixing means.

Further, in the automatic tuning apparatus according to claim 3, preferably, the automatic tuning apparatus further includes a generating means for generating the reference signal and outputting the reference signal to the mixing means;
Third coupling means for extracting a part of the reference signal generated by the generating means and outputting the reference signal to the band-pass filter, and extracting a part of the signal output from the band-pass filter after passing through the band-pass filter And a fourth coupling means for outputting to the mixing means.

Still further, in the automatic tuning apparatus according to claim 4, preferably, the automatic tuning apparatus further comprises:
Input means for inputting the center frequency to be set of the band-pass filter, the control means, based on the center frequency to be set input by the input means,
The generating means is controlled to generate a reference signal having the center frequency to be set.

In the automatic tuning apparatus according to the present invention, preferably, the automatic tuning apparatus further comprises a receiving means for receiving information on a center frequency to be set by the band-pass filter from an external device. The control means controls the generating means based on the center frequency to be set received by the receiving means to generate a reference signal having the center frequency to be set.

In the automatic tuning apparatus according to the present invention, preferably, the band-pass filter includes a resonator, and the control means calculates a resonance frequency of the resonator based on the DC component signal. The band-pass filter is controlled based on the calculated resonance frequency such that the center frequency of the band-pass filter matches the frequency of the reference signal.

Still further, in the automatic tuning type band pass filter according to the present invention, the first, second, third, fourth and fifth aspects are provided.
Or the band-pass filter according to claim 6 and claim 1, 2, 3, or
An automatic tuning type band-pass filter can be configured by including the automatic tuning device according to 4, 5, or 6.

Further, in the antenna sharing apparatus according to the present invention, a plurality of automatic tuning type band pass filters are provided, and the plurality of automatic tuning type band pass filters are respectively provided in the plurality of automatic tuning type band pass filters. Terms 1, 2, 3,
Each of the output terminals for outputting a signal output from each of the band-pass filters described in 4, 5, or 6 is electrically connected to each other, so that each of the automatic tuning type band-pass filters is affected by a signal sneak from another channel. An antenna sharing device capable of performing the above-described tuning operation without receiving the signal can be configured.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 2 is a block diagram showing an automatic tuning type bandpass filter 2a, 2b, 2 according to a first embodiment of the present invention.
FIG. 1 is a block diagram of the automatic tunable band-pass filter 2a of FIG. In FIG. 1, a band-pass filter (B
The dielectric resonator 31 in the (PF) 30 is illustrated by an equivalent circuit.

Automatic tuning type band pass filter 2 of this embodiment
a, 2b, and 2c cause the directional coupler 20 to split a part of the power of each ultrahigh-frequency transmission signal (hereinafter, referred to as a transmission signal) output from the transmitters 1a, 1b, and 1c. The frequency of the transmission signal branched by 20 is measured by the frequency counter 47. Further, after the transmission signal passes through the band-pass filter 30, a part of the power of the transmission signal is branched by the directional coupler 22, and The transmission signal branched by the directional coupler 20 is used as a local oscillation signal, and the transmission signal branched by the directional coupler 22 is transmitted from the mixer 60 and the low-pass filter 61 that passes only a predetermined low-frequency component. Is converted to a DC component by a frequency conversion circuit, and based on the converted DC component, the level of the signal of the DC component is substantially zero, The center frequency fc of the over-filter 30
Is characterized in that it drives a stepping motor 33 that changes the variable capacitance VC of the dielectric resonator 31 in the band-pass filter 30 so as to substantially match the frequency of the transmission signal measured by the frequency counter 47.

As shown in FIG. 2, each transmitter 1a, 1b,
1c, each of which has a predetermined constant level, for example, each transmission signal having a different frequency f ₁ , f ₂ , f ₃ (f ₁ <f ₂ <f ₃ ) in the UHF band, Automatically tunable bandpass filters 2a, 2 of the embodiment
After passing through b and 2c, they are synthesized. Here, each output terminal of each automatic tuning type band pass filter 2a, 2b, 2c is electrically connected together. Next, the frequencies f ₁ , f ₂ ,
via the transmission bandpass filter 3 which passes only frequency band including f ₃ is output to the antenna 4, synthesized above transmission signal is radiated from the antenna 4. here,
The automatic tuning type band pass filters 2a, 2b, 2c have the same configuration. Therefore, the following description will be made in detail with reference to FIG.

As shown in FIG. 1, a signal output from the transmitter 1a is transmitted through the isolator 10 to the directional coupler 20a.
Is input to the input terminal 20a. The directional coupler 20 divides and extracts a transmission line through which a transmission signal input from the transmitter 1a to the input terminal 20a passes, and a part of the power of the transmission signal which is electromagnetically coupled to the transmission line and passes therethrough. Directional coupler 20 separated by a predetermined distance so that
And a transmission signal detection coupling line for detecting the passing transmission signal (hereinafter referred to as a “pass signal”). The transmission signal detection coupling line includes an output terminal (hereinafter, referred to as a coupling line). 20p is provided.
The output end 20p of the coupled line is connected to two distributors 40, 4
1 is connected to a local oscillation signal input terminal of the mixer 60. Furthermore, the output end 2 of the passing line of the directional coupler 20
Signal output from 0b is input across the input coil L ₁ of the band-pass filter 30 having a center frequency fc with a dielectric resonator 31.

The transmission signal output from both ends of the output coil L ₂ passes through the band pass filter 30 has an input terminal 22a and an output end of the pass line of the directional coupler 22 22
The signal is output to the band-pass filter 3 via b. The directional coupler 22 is capable of extracting a transmission line that passes the transmission signal after passing through the band-pass filter 30 and a part of the power of the transmission signal that is electromagnetically coupled to the transmission line and passes therethrough. A transmission signal detecting coupling line for detecting a pass signal, which is provided on the input end 22a side of the directional coupler 22 so as to be separated by a predetermined interval so that the transmission signal detecting coupling line has an output terminal 22p. . The output end 22p of the coupling line is connected to the main signal input terminal of the mixer 60.

Dielectric resonator 3 in band pass filter 30
1 is composed of two inductances L ₁₁ and L ₁₂ connected in parallel, a variable capacitance VC, and a loss resistance Ro, as shown in the equivalent circuit of FIG. 1, and the inductance L ₁₁ is the input side coil L ₁ to be electromagnetically coupled by inductive coupling + M, whereas, the inductance L ₁₂ is electromagnetically coupled by inductive coupling + M on the output side coil L ₂ of the band-pass filter 30. The capacitance of the capacitance VC is changed by a stepping motor 33 controlled by the control circuit 50 as described later in detail.

FIG. 3 is a sectional view of a band-pass filter 30 having a dielectric resonator 31. As shown in FIG. 3, a cylindrical dielectric resonator 211 is placed on a support base 214 having the same linear expansion coefficient as the dielectric resonator 211 at a central portion in the cylindrical shield case 210. ing. The dielectric resonator 211 is, for example, a ceramic dielectric resonator in which TiO ₂ is a main component and ZrSn is mixed, and the dielectric resonator 31 of this embodiment is about 886 in a TE _01δ mode which is a fundamental mode. It has a resonance frequency f _{0 of} .4 MHz. A cylindrical dielectric tuning element 212 is provided inside the cylinder of the dielectric resonator 211 and supported by a shaft 215. Here, the shaft 215 is moved by an arrow A by the stepping motor 33.
It is moved in the minus direction of 1 and in the plus direction of arrow A2 in the opposite direction. By moving the dielectric tuning element 212 in the gradient of the electric field of the dielectric resonator 211,
The resonance frequency f ₀ of the dielectric resonator 211 can be finely adjusted.

FIG. 4 shows the relationship between the position of the dielectric tuning element 212 of the band-pass filter 30 of FIG. 3 and the center frequency fc of the band-pass filter 30 substantially equal to the resonance frequency f ₀ of the dielectric resonator 211. It is a graph. Here, g is a distance from the upper surface of the dielectric tuning element 212 to the shield case 210.
Is the distance to the inside of the upper surface of. As is apparent from FIG. 4, by moving the dielectric tuning element 212 away from the upper surface of the shield case 210, that is, by increasing the distance g, the resonance frequency f ₀ of the dielectric resonator 211 becomes equal to the distance g. It generally changes in inverse proportion.

The shield case 210 is constructed by baking silver electrodes on the outer surface of a cylindrical housing made of ceramics having the same linear expansion coefficient as the dielectric resonator 211 for electromagnetic shielding. I have. As shown in FIG. 3, at two positions on the lower surface of the shield case 210 and directly below the outer peripheral edge of the dielectric resonator 211 and opposite to each other about the center of the cylinder as shown in FIG. To couple with the magnetic field of the dielectric resonator 211,
For example the input coil L ₁ and the output-side coil L ₂ of each one turn is provided.

FIG. 5 shows a case where a signal is input to the input terminal of the band-pass filter 30 when the output terminal of the band-pass filter 30 of FIG. 3 is terminated by a terminating resistor having a predetermined impedance. 30 is a graph showing the frequency characteristics of 30 pass losses. Here, the unloaded Q of the dielectric resonator 31 in the band-pass filter 30 is used.
(Q ₀ ) is 20,000 and its load Q (Q _L ) is 1,800. As is clear from FIG. 5, the pass loss of the band-pass filter 30 becomes minimum at the resonance frequency f ₀ of the dielectric resonator 31.

Generally, in a band-pass filter 30 having a load Q (Q _L ) and including a resonator, a pass phase θ of the band-pass filter 30 at a frequency f ₁ separated from the resonance frequency f ₀ by a frequency Δf. _R is represented by Equation 1.
Here, Δf≪f ₀ .

[0037]

(Equation 1)

Further, the difference between the passing loss IL ₀ of the band-pass filter 30 at the resonance frequency f ₀ [dB] pass loss of the band-pass filter 30 at the frequency f ₁ with a vicinity of the resonance frequency f ₀ and IL ₁ [dB] Is represented by Equation 2.

[0039]

(Equation 2)

Accordingly, Equation 3 is obtained from Equations 1 and 2.

[0041]

(Equation 3)

Further, from _{equation (} 1), the resonance frequency f ₀ is represented by _{equation (} 4).

[0043]

(Equation 4)

Here, the dimensionless constant F ₁ is expressed by Equation 5.

[0045]

(Equation 5)

Next, the automatic tuning type band pass filter 2a
The circuit of the signal processing system and the control system therein will be described with reference to FIG.

As shown in FIG. 1, the passing signal of the frequency f ₁ output from the output end 20p of the coupling line of the directional coupler 20 is divided into two by the divider 40, and one of the divided passing signals is While being output to the detection circuit 42, the other divided passing signal is output to the distributor 41. After detecting the input pass signal, the detection circuit 42 detects a low-pass filter (LP) having a predetermined cutoff frequency.
F) The signal is input to the non-inverting input terminal of the comparator 45 via the amplifier 43 and the amplifier 43. On the other hand, the threshold voltage generating circuit 46 generates a threshold voltage for determining whether or not the transmission signal exists, and outputs the generated threshold voltage to the inverting input terminal of the comparator 45. When the transmission signal input to the non-inverting input terminal is equal to or higher than the threshold voltage, the comparator 45 outputs an H-level comparison result signal via the interface circuit 54 in the control circuit 50 to a central processing unit (hereinafter, CPU). ) Is output to 51. On the other hand, when the passing signal input to the non-inverting input terminal is lower than the threshold voltage, the comparator 45 outputs an L level comparison result signal to the CPU 51 via the interface circuit 54.

The splitter 41 splits the input passing signal into two and outputs the split signal to the frequency counter 47 and the mixer 60. The frequency counter 47 measures the frequency of the input passing signal, and outputs data fm of the measured frequency to the CPU 51 via the interface circuit 55 in the control circuit 50.

The mixer 60 composed of a multiplier mixes and multiplies the signal input to the main signal input terminal and the signal input to the local oscillation signal input terminal, and converts the mixed signal into a low-frequency signal. The signal is output to a pass filter (LPF) 61. Here, the mixed signal output from the mixer 60 is represented by f ₁ + f ₁ and f _1
1- f ₁ (DC component), the low-pass filter 61 passes only the DC component of the input mixed signal, and then converts the DC component signal into an amplifier 62.
To an analog / digital conversion (hereinafter referred to as A / D conversion) circuit 63. Next, the A / D conversion circuit 63 converts the DC component analog signal into a digital signal, and converts the signal into an interface circuit 56 in the control circuit 50.
Is output to the CPU 51 via the.

Here, the directional coupler 22 to the mixer 60
The voltage of the main signals input to the V _M, also distributor 4
The voltage of the local oscillation signal input from 1 to the mixer 60 is V
_Assuming that _L is _L and the phase difference between the signals input to the mixer 60 is Δθ, the DC component voltage V ₀ output from the low-pass filter 61 is expressed by Equation 6.

[0051]

(Equation 6)

Here, a ₆₀ is a multiplication coefficient of the mixer 60,
This is a device constant determined by the DC passing loss of the low-pass filter 61.

Now, the input end 20a of the directional coupler 20 is used as a reference point, and the input end of the directional coupler 20 and the output end 20b of its passing line, the band-pass filter 30, and the input of the directional coupler 22 from the reference point. The main signal transmission line extending from the end 22a to the main signal input terminal of the mixer 60 through the output end 20p of the coupled line is defined as a first transmission line. A local oscillation signal transmission line extending from the coupled line, the output end 20p thereof, and the two distributors 40 and 41 to the local oscillation signal input terminal of the mixer 60 is defined as a second transmission line. Here, the transmission phase θ ₁ a of the first transmission line at an arbitrary frequency fa which is preferably near the resonance frequency f ₀ of the dielectric resonator 31 of the band-pass filter 30 (however, excluding transmission phase theta _R.) and the transmission phase theta ₂ a of the second transmission line is measured in advance.

When the resonance frequency f ₀ of the dielectric resonator 31 of the band pass filter 30 is set to a certain set frequency f ₁ , at the set frequency f ₁ , the band pass filter 30
Assuming that the transmission phase of the first transmission line excluding the transmission phase θ _R is θ ₁ and the transmission phase of the second transmission line is θ ₂ , the phase difference Δθ of each signal input to the mixer 60 is Number 7
It is represented by

[0055]

(Equation 7)

In this embodiment, the phase difference Δθ of each signal input to the mixer 60 at the set frequency f _{1 at} which the resonance frequency f ₀ of the dielectric resonator 31 of the band-pass filter 30 is to be set. Is 2nπ + π / 2 [rad]
(Where n is an integer), preferably π /
A delay circuit (not shown) is previously inserted into the first or second transmission line so as to obtain 2 [rad].

At a certain set frequency f ₁ , assuming that the signal level of the transmission signal input to the input terminal 20 a of the directional coupler 20 is S _r [dBm], the signal level of the main signal input to the mixer 60 is S _M [dBm] and the signal level S _L [dBm] of the local oscillation signal are expressed by Expressions 8 and 9, respectively.
become that way. In Equations 8 and 9, the loss of each transmission line connecting each element is neglected.

[0058]

(Equation 8)

[0059]

(Equation 9)

Here, L ₂₀ t is the passing loss [dB] of the directional coupler 20 measured in advance, L ₂₀ p is the branch loss [dB] of the directional coupler 20 measured in advance, L
₂₂ p branching loss of the directional coupler 22 to be measured in advance [d
B], L ₄₀ is the distribution loss [dB] of the distributor 40 measured in advance, and L ₄₁ is the distribution loss [dB] of the distributor 41 measured in advance. Further, a ₆₀₁ and a ₆₀₂ are constants determined in advance.

As is apparent from equations 8 and 9, the signal level S _M of the main signal is smaller than the signal level S _r of the transmission signal.
Set is determined depending on the transmission loss IL ₁ of the band-pass filter 30 at the frequency f _1, whereas, the signal level S _L of the local oscillation signal is predetermined for the signal level S _r of the transmission signal.

Therefore, as is apparent from the equations (6) and (8), the voltage V _{0 of the} DC component output from the low-pass filter 61 is different from that of the band-pass filter 30 at the set frequency f ₁ .
A transmission loss IL ₁ of is determined depending on the phase difference Δθ of each signal inputted to the mixer 60. That is, the voltage V _{0 of the} DC component becomes the set frequency f _{1 as} shown in Expression _10.
A transmission loss IL ₁ of the band-pass filter 30 in, is expressed by a function related to the phase difference Δθ of each signal inputted to the mixer 60.

[0063]

(Equation 10)

In this embodiment, transmission from the transmitter 1a
Signal input to automatic tuning bandpass filter 2a
And the DC component output from the low-pass filter 61.
Pressure V₀Is measured, and the measured voltage V₀Was substituted into Equation 10.
Then, solve the ternary system of equations (3), (7) and (10)
And thereby the center frequency of the bandpass filter 30
Set frequency f to be set for fc₁Bandpass filter at
Transmission phase θ of the filter 30_RAnd passage loss IL₁And the phase difference Δ
θ is calculated. Then, the calculated transmission phase θ_RTo
Substituting into Equation 5, constant F₁, And then the calculated
Constant F₁Is substituted into Equation 4 to obtain the resonance frequency f₀Is calculated. This
Calculated resonance frequency f₀And set frequency f ₁On the basis of
Movement by which the dielectric tuning element 212 is to be moved by using Expression 11
Calculate the distance lm.

[0065]

[Equation 11]

Here, k is a constant determined from the graph of FIG. Further, a pulse drive signal having a pulse number corresponding to the calculated moving distance lm is input to the stepping motor 33 to move the dielectric tuning element 212, thereby setting the center frequency fc of the band-pass filter 30 to the above-described value. tuning process as substantially to match the frequency f ₁ can be performed.

The control circuit 50 of the automatic tuning type band pass filter 2a executes a tuning process of the band pass filter 2a and controls the dielectric resonator 31 in the band pass filter 30, and a control program of the tuning process. A ROM 52 for storing data necessary for executing the control program, and interface circuits 54, 55 used as a working area of the CPU 51;
RAM for storing data input via 56
53. In the control circuit 50, the CPU 51
, The ROM 52, the RAM 53, and each of the interface circuits 54 to 57 are connected via the bus 58.

When the CPU 51 executes the tuning process,
As will be described later in detail, in order to make the resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 substantially coincide with the frequency f ₁ of the signal output from the transmitter 1a, the interface circuits 54 to 56 are used. In order to drive the stepping motor 33 so that the level of the DC component signal input from the A / D conversion circuit 63 to the CPU 51 via the interface circuit 56 becomes substantially 0 based on each data input through the interface. Is output to the stepping motor 33 via the interface circuit 57 and the motor drive circuit 32 to be driven. Here, when a positive polarity pulse motor drive signal is input to the stepping motor 33, the dielectric tuning element 212 in the band-pass filter 30 of FIG. 3 is moved in the direction of arrow A2. When a pulsed motor drive signal is input, the band-pass filter 3 of FIG.
The dielectric tuning element 212 within 0 is moved in the direction of arrow A1. As a result, the capacitance of the variable capacitance VC in the equivalent circuit of FIG.
Changes the resonance frequency f ₀ of Therefore, it is possible to change the center frequency fc of approximately equal band pass filter 30 to the resonance frequency f _0. In the present embodiment, the control circuit 50 drives the stepping motor 33 so that the level of the DC component output from the low-pass filter 61 becomes 0, and controls the dielectric resonator 31 in the band-pass filter 30. Change the resonance frequency, thereby causing the resonance frequency f ₀
Center frequency fc of bandpass filter 30 approximately equal to
Can be substantially matched with the frequency f _{1 of the} transmission signal input from the transmitter 1a.

FIG. 6 is a flowchart showing the main routine of the tuning process of the control circuit 50 of the automatic tuning type band pass filter shown in FIG. 1. This main routine determines the center frequency fc of the built-in band pass filter 30 by the transmitter. 1a is a process for substantially match the frequency f ₁ of the signal outputted from the. In the initial state before the start of the main routine, the dielectric tuning element 212 of the dielectric resonator 31 is located at an arbitrary distance g. In this main routine, the processing from step S5 to step S7, be coarse tuning process for changing the center frequency fc of the band-pass filter 30 built in the frequency near the frequency f ₁ of the signal outputted from the transmitter 1a , The processing of step S8 is based on the center frequency fc of the built-in bandpass filter 30.
And by changing the frequency in the vicinity of the frequency f ₁ after the coarse tuning process is a fine tuning process for a generally matching the frequency f _1.

As shown in FIG. 6, when the power switch (not shown) of the control circuit 50 is turned on, the main routine of the tuning process shown in FIG. 6 is started.
The dielectric tuning element 212 in the stepping motor 3
3 is moved to a position of g = 4 [mm] (hereinafter, referred to as a home position). That is, in this embodiment, a stopper (not shown) for the dielectric tuning element is provided in the band-pass filter 30 so that the dielectric tuning element 212 cannot move from the home position in the direction of arrow A1. In step S1, the stepping motor 3
When a positive polarity pulse motor drive signal is continuously input to 3, and the dielectric tuning element 212 is stopped at the home position by the stopper, a microswitch (not shown) provided at the home position is operated. At this time, the driving of the stepping motor 33 is stopped. In addition, the resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 at the home position is 897 [MHz] measured in advance as shown in FIG.

Then, in step S2, 897 [MHz] is set as data of the current resonance frequency f ₀ and stored in the RAM 53, and then the comparison result signal output from the comparator 45 is changed from L level to H level in step S3. It is determined whether or not it has risen to L level, or remains at H level, or changes from H level to L level.
When the level falls (N in step S3)
O) In a standby state, on the other hand, when rising from the L level to the H level (YES in step S3), the process proceeds to step S4. Next, in step S4, the frequency data f of the passing signal input from the frequency counter 47 is output.
m is stored in the RAM 53 in step S5, and the measured frequency data fm is used as the set frequency f ₁ of the center frequency fc of the band-pass filter 30 as RA
Store it in M53.

Next, at step S6, the resonance frequency f ₀ stored in the RAM 53 for performing the coarse tuning process.
Based on the data of ( ₁₎ and the data of the set frequency f1,
Is used to calculate the moving distance lm for moving the dielectric tuning element 212. Next, in step S7, a pulse drive signal having the number of pulses corresponding to the calculated moving distance lm is input to the stepping motor 33 to move the dielectric tuning element 212. When the moving distance lm is positive, a pulse drive signal having a positive polarity is input to the stepping motor 33, whereby the dielectric tuning element 212 is moved in the direction of the arrow A2 by the moving distance lm. When the moving distance lm is negative, a pulse drive signal having a negative polarity is input to the stepping motor 33, whereby the dielectric tuning element 212 is moved in the direction of the arrow A1 by the moving distance lm. Thus, the rough adjustment is completed. Further, in step S8, the center frequency fc of the band-pass filter 30 built, by changing the frequency in the vicinity of the frequency f ₁ after the coarse tuning process, the fine tuning process for a generally matching the frequency f ₁ After executing (see FIG. 7), the process returns to step S3. Hereinafter, the coarse tuning process and the fine tuning process are repeated according to the transmission signal newly input to the automatic tuning type bandpass filter 2a.

FIG. 7 shows the fine tuning process of FIG. 6 (step S
The flowchart of the subroutine of 8) is shown.

As shown in FIG. 7, the output voltage data V input from the A / D conversion circuit 63 in step S11.
d, the output voltage V ₀ of the low-pass filter 61 is converted into the output voltage V ₀ and stored in the RAM 53. Then, in step S12, based on the converted output voltage V ₀ , Equations 3, 7, and 10 are used as described above. Then, the resonance frequency f ₀ is calculated using Equations 4 and 5.

Next, in step S13, based on the calculated resonance frequency f ₀ and the set frequency f ₁ set in the previous step S5, the moving distance lm to be moved by the dielectric adjustment element 212 is calculated by using _{equation (} 11). After the calculation, in step S14, the calculated moving distance l
The pulse drive signal of the pulse number corresponding to m is input to the stepping motor 33 to move the dielectric tuning element 212. Next, in step S15, the output voltage data Vd input from the A / D conversion circuit 63 is fetched.
The output voltage V ₀ of the low-pass filter 61 is converted into RAM
53, whether or not the absolute value | Vd | of the output voltage data is smaller than a threshold voltage Vth, which is a positive number very close to 0, for judging that the output voltage data is substantially synchronized in step S16. Is determined. Here, when the absolute value | Vd | of the output voltage data is smaller than threshold voltage Vth (YES in step S16), it is determined that the fine tuning process has been completed, and the process returns to the original main routine. NO), in order to further perform fine tuning processing, in step S17,
The output voltage data V ₀ measured and converted at 15
After calculating the resonance frequency f ₀ based on
It returns to step S13. Hereinafter, until the absolute value | Vd | of the output voltage data becomes smaller than the threshold voltage Vth.
That process of the loop is performed to the center frequency fc of the band-pass filter 30 is substantially coincides with the set frequency f _1.

In the present embodiment, as described above, a part of the transmission signal input from the transmitter 1a is
0, a part of the transmission signal after passing through the band-pass filter 30 is extracted by the directional coupler 22, and the extracted signals are mixed by the mixer 60, and the output of the mixer 60 is output. among the low-pass filter 61 extracts only the DC component, based on the output voltage V ₀ which low-pass filter 61 calculates the resonance frequency f ₀ of the dielectric resonator 31 of the band-pass filter 30, is calculated for The moving distance lm to be moved by the dielectric tuning element 212 is calculated based on the resonance frequency f ₀ , and the dielectric tuning element 212 is moved by the calculated moving distance lm so that the center frequency fc of the band-pass filter 30 becomes It is generally matched to the set frequency f _1. In other words, the stepping motor 33 is driven to move the dielectric tuning element 212 so that the output voltage V ₀ of the low-pass filter 61 becomes 0, whereby the center frequency fc of the band-pass filter 30 becomes equal to the set frequency f. Generally matched to ₁ .

In the automatic tuning type band pass filter 2a configured as shown in FIG. 1, for example, the components of the transmission signals of the frequencies f ₂ and f ₃ from the transmitters 1b and 1c of the other channels are respectively transmitted to the automatic tuning type band pass filter 2b. , 2c, the directional couplers 22 and 20 are provided, so that the frequency components of the sneak path from the other channel are not input to the mixer 60. Therefore, the above-described tuning processing can be performed without being affected by frequency components wrapping around from other channels as in the conventional example.

When the frequencies f ₂ and f _{3 of} the other channels are sufficiently separated from the frequency f _{1 of the} transmission signal output from the transmitter 1a, reflections are made instead of the directional couplers 22 and 20. even when using such distributor signal is output, the mixer 60 after the echo signal of the other channel is passed through a bandpass filter 30 having a large attenuation sufficiently with respect to the frequency f ₁ Since the signal is input to the local oscillation signal input terminal, the level of the DC component related to the frequencies f ₂ and f ₃ of the other channels, which appears in the output of the low-pass filter 61, is very small, and almost always affects the tuning processing. Absent. Therefore, as in the conventional example,
The above-described tuning processing can be performed without being affected by the frequency components of the wraparound from other channels.

The automatic tuning band-pass filters 2b and 2c have the same configuration as that of the above-mentioned automatic tuning band-pass filter 1a.
In 2c, the above-mentioned tuning process is performed so that the center frequency of the built-in band-pass filter substantially matches the frequencies f ₂ and f ₃ of the signals output from the transmitters 1b and 1c.

<Second Embodiment> FIG. 8 is a block diagram of an automatic tuning type bandpass filter 2aa according to a second embodiment of the present invention. In FIG. 8, the same components as those in FIG. 1 are the same. Are given.

Although the transmission signal from the transmitter 1a is used as the reference signal in the automatic tuning type band pass filter 2a of the first embodiment, the automatic tuning type band pass filter 2aa of the second embodiment is Compared with the automatic tuning type band-pass filter 2a of the first embodiment shown in FIG. 1, the set frequency fs inputted by using the keyboard 81 without using the frequency counter 47, the comparator 45 and its peripheral circuits is provided.
A signal of the set frequency fs is generated by the built-in signal generator 71 based on the data of the band pass filter 30, and the center frequency fc of the bandpass filter 30 is made to substantially match the set frequency fs using the signal as a reference signal. And Hereinafter, differences from the first embodiment will be described.

As shown in FIG. 8, the control circuit 50 includes an interface circuit 80 connected to the keyboard 81 for inputting the set frequency f ₁ , an interface circuit 59 connected to the control terminal of the switch SW, and a signal An interface circuit 70 is connected to the generator 71. Each of the interface circuits 59, 70, 80 is connected to a bus 58 in the control circuit 50. The CPU 51 outputs the frequency setting data fs to the signal generator 71 via the interface circuit 70. In response to this, the signal generator 71 generates a reference signal having the frequency fs, and transmits the reference signal to the amplifier 72 and the switch. The signal is output to the input terminal 24a of the directional coupler 24 via the SW b side. Here, the signal generator 71 is a signal generator that includes, for example, a PLL circuit and can change the frequency of a generated signal. Further, the a side of the switch SW is connected to the ground via the terminating resistor _RL , and the switch SW is selectively switched to the a side or the b side by the CPU 51.

The directional coupler 24 passes a reference signal input to the input terminal 24a from the signal generator 71 via the amplifier 72 and the switch SW, and electromagnetically couples with the passing line to pass. A reference signal detecting coupling line provided at the input end 24a side of the directional coupler 24 and separated by a predetermined interval so as to allow a part of the power of the reference signal to be branched and taken out; The coupling line for detecting a reference signal includes an output terminal 24p. The directional coupler 20 is separated from the directional coupler by a predetermined distance so as to be electromagnetically coupled to the passing line and to combine a reference signal input to the input end of the coupling line with the passing signal. And a signal-combining coupling line provided on the input end 20b side of the input terminal 20. The output end 24b of the passing line of the directional coupler 24 is connected to the input end 20r of the coupling line of the directional coupler 20, and the output end 24p of the coupling line of the directional coupler 24 is connected to the local oscillation signal input of the mixer 60. Connected to terminal.

In this embodiment, at the set frequency f _{1 at} which the resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 is to be set, the phase difference of each signal input to the mixer 60 is set. Δθ is 2nπ + π / 2 [rad]
(Where n is an integer), preferably π /
As in the first embodiment, a delay circuit (not shown) is inserted in advance so as to obtain 2 [rad].

FIG. 9 is a flowchart showing a main routine of the tuning process of the control circuit 50 of the automatic tuning type band-pass filter 2aa of FIG. 8 constructed as described above. This is a process for making the center frequency fc of 30 approximately match the set frequency fs input using the keyboard 81. In this main routine, the processing from step S26 to step S27 is performed by the built-in bandpass filter 30.
Is a coarse tuning process for changing the center frequency fc of the set to a frequency near the set frequency fs.
This is a fine tuning process for changing the center frequency fc of the built-in band-pass filter 30 from a frequency near the set frequency fs after the coarse tuning process so as to substantially match the set frequency fs. Note that, before executing the tuning process of FIG. 9, a transmission signal is not input from the transmitter 1a to the automatic tuning type bandpass filter 2a, and for example, the input terminal of the isolator 10 is terminated by a predetermined terminating resistor.

As shown in FIG. 9, when a power switch (not shown) of the control circuit 50 is turned on, the main routine of the tuning process shown in FIG. 9 is started.
In step 1, the dielectric tuning element 212 is moved to the home position of g = 4 [mm] by driving the stepping motor 33. Next, in step S22, 897 [MHz] is set as the data of the current resonance frequency f ₀ and R
After being stored in the AM 53, it is determined in step S23 whether or not the data of the set frequency fs has been input from the keyboard 81 via the interface circuit 80, and if the data of the set frequency fs has not been input (NO in step S23). If the data of the set frequency fs is input (YES in step S23), the process proceeds to step S24. Step S24
In the above, the set frequency fs is
Is stored in the RAM 53 as the set frequency f ₁ of the center frequency fc of the above.

Next, in step S25, the resonance frequency f stored in the RAM 53 for performing the coarse tuning process is set.
Based on the set frequency f ₁ of the data and ₀ data, number 11
Is used to calculate the moving distance lm for moving the dielectric tuning element 212. Next, in step S26,
As in step S7, a pulse drive signal having a pulse number corresponding to the calculated moving distance lm is input to the stepping motor 33 to move the dielectric tuning element 212. Thus, the rough adjustment is completed. Further, step S2
After switching the switch SW to the side b at 7, the center frequency fc of the band-pass filter 30 having a built-in step S28, by changing the frequency in the vicinity of the frequency f ₁ after the coarse tuning process, the frequency f ₁ A fine tuning process (see FIG. 7) is performed to substantially match. Next, after the switch SW is switched to the a side in step S29, the process returns to step S23.

In this embodiment, as described above, the reference signal having the set frequency fs input using the keyboard 81 is generated by the signal generator 71, and the reference signal after passing through the band-pass filter 30 is generated. Partially directional coupler 2
2, the reference signal generated by the signal generator 71 and the extracted reference signal are mixed by a mixer 60, and only the DC component of the output of the mixer 60 is output by a low-pass filter 61. The resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 is calculated based on the output voltage V ₀ of the low-pass filter 61, and the dielectric tuning element 212 is calculated based on the calculated resonance frequency f _0. and calculating a moving distance lm should move only calculated moving distance lm by moving the dielectric tuning element 212, the center frequency fc of the band-pass filter 30 is substantially matched to the set frequency f _1. In other words, the stepping motor 33 is driven to move the dielectric tuning element 212 so that the output voltage V ₀ of the low-pass filter 61 becomes 0, whereby the center frequency fc of the band-pass filter 30 becomes equal to the set frequency f. Generally matched to ₁ .

In the automatic tuning type band pass filter 2aa configured as shown in FIG. 8, for example, the components of the transmission signals of the frequencies f ₂ and f ₃ from the transmitters 1b and 1c of the other channels are respectively transmitted to the automatic tuning type band pass filter 2b. , 2c, the directional couplers 22 and 24 are provided, so that the frequency components of the sneak path from the other channel are not input to the mixer 60. Therefore, the above-described tuning processing can be performed without being affected by frequency components wrapping around from other channels as in the conventional example.

[0090] Incidentally, when the frequency f _2, f ₃ of the other channels are sufficiently separated with respect to the frequency f ₁ of the transmission signal outputted from the transmitter 1a, the reflection instead of the directional coupler 22, 24 even when using such distributor signal is output, the mixer 60 after the echo signal of the other channel is passed through a bandpass filter 30 having a large attenuation sufficiently with respect to the frequency f ₁ Since the signal is input to the local oscillation signal input terminal, the level of the DC component related to the frequencies f ₂ and f ₃ of the other channels, which appears in the output of the low-pass filter 61, is very small, and almost always affects the tuning processing. Absent. Therefore, as in the conventional example,
The above-described tuning processing can be performed without being affected by the frequency components of the wraparound from other channels.

In the above-described second embodiment, the data of the set frequency fs is input using the keyboard 81. However, the present invention is not limited to this, and the set frequency fs is input from an external device such as another control circuit. A receiving circuit for receiving data or an interface circuit of the control circuit 50 is provided, and the control circuit 50 outputs the received data of the set frequency fs to the signal generator 71 to generate a reference signal having the set frequency fs. May be configured.

<Other Embodiments> In the above embodiments, the band-pass filter 30 is formed by using the dielectric resonator 31, but the present invention is not limited to this, and the center frequency can be changed. Various other band-pass filters may be used.

In the above embodiment, the A / D conversion circuit 6
3, the resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 is calculated based on the output voltage Vd, and the moving distance lm for moving the dielectric tuning element 212 based on the calculated resonance frequency f _0. And calculate the dielectric tuning element 2
12 is moved by the calculated moving distance lm, the above-described tuning processing is performed. However, the present invention is not limited to this, and the A / D is calculated without calculating the resonance frequency f _0.
The tuning process may be performed by moving the dielectric tuning element 212 based on the output voltage Vd of the conversion circuit 63 so that the output voltage Vd becomes zero.

In the above embodiment, the phase difference Δθ of each signal input to the mixer 60 at the set frequency f _{1 at} which the resonance frequency f ₀ of the dielectric resonator 31 in the band pass filter 30 is to be set. Is 2nπ + π / 2 [rad]
(Where n is an integer), preferably π /
With the delay circuit inserted and adjusted in advance to be 2 [rad], the output voltage V ₀ of the low-pass filter 61 becomes 0
The above tuning process is performed by changing the center frequency fc of the bandpass filter 30 so that However,
The present invention is not limited to this, and the phase difference Δθ of each signal input to the mixer 60 is 2nπ at the set frequency f _{1 at} which the resonance frequency f ₀ of the dielectric resonator 31 in the band-pass filter 30 is to be set. [Rad], preferably 0 [r
ad], the tuning process is performed by changing the center frequency fc of the band-pass filter 30 so that the output voltage V ₀ of the low-pass filter 61 is maximized, with the delay circuit inserted and adjusted in advance. May go. Further, the resonance frequency f ₀ of the dielectric resonator 31 in the band pass filter 30 is described.
In the set frequency f ₁ to be set for the phase difference Δθ is 2nπ + π [rad] next to each signal input to the mixer 60, preferably by inserting the pre-delay circuit so that the [pi or - [pi] [rad] In the adjusted state, the tuning process may be performed by changing the center frequency fc of the band-pass filter 30 so that the output voltage V ₀ of the low-pass filter 61 is minimized.

In the above embodiment, the tuning process is performed digitally using the stepping motor 33.
The present invention is not limited to this, and the tuning process may be performed by controlling the output voltage V ₀ of the low-pass filter 61 to be ₀ using a motor driven by an analog signal.

[0096]

As described above in detail, according to the automatic tuning apparatus for a band-pass filter according to the first aspect of the present invention, a band-pass filter capable of changing a predetermined reference signal and a center frequency. When the reference signal is input to the filter, the signal is passed through the band-pass filter, mixed with a signal output from the band-pass filter, multiplied and output as a multiplication result signal, and the output multiplication result signal is output. Filtering the DC component signal, and controlling the band-pass filter so that the center frequency of the band-pass filter matches the frequency of the reference signal based on the filtered DC component signal. There is an advantage that the center frequency of the band-pass filter can be matched with the frequency of the reference signal and tuned with a simple circuit configuration and with better accuracy than the conventional example.

[0097] Further, a band-pass filter according to claim 1, 2, 3, 4, 5, or 6 and an automatic tuning apparatus according to claim 1, 2, 3, 4, 5, 5 or 6 are provided. A type bandpass filter can be configured.

Further, a plurality of self-tuning band-pass filters according to claim 7 are provided, and the plurality of self-tuning band-pass filters are provided respectively.
Each of the output terminals for outputting signals output from each of the band-pass filters described in 3, 4, 5, or 6 is electrically connected to each other, so that each of the automatic tuning type band-pass filters has a sneak path from another channel. An antenna sharing device capable of performing the above-described tuning operation without being affected by a signal can be configured.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic tuning type bandpass filter according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an antenna sharing apparatus including three self-tuning band-pass filters of FIG. 1;

FIG. 3 is a sectional view of the bandpass filter of FIG. 1;

FIG. 4 is a graph showing a relationship between a position of a dielectric tuning element of the band-pass filter of FIG. 3 and a center frequency.

FIG. 5 is a graph showing a frequency characteristic of a pass loss of the band-pass filter of FIG. 3;

FIG. 6 is a flowchart showing a main routine of a control flow of a control circuit of the automatic tuning band pass filter of FIG. 1;

FIG. 7 is a flowchart showing a subroutine of the fine tuning processing of FIGS. 6 and 9;

FIG. 8 is a block diagram of an automatic tuning type bandpass filter according to a second embodiment of the present invention.

9 is a flowchart showing a main routine of a control flow of a control circuit of the automatic tuning type band pass filter of FIG. 8;

FIG. 10 is a block diagram of a conventional automatic tuning type band pass filter.

[Explanation of symbols]

1a, 1b, 1c transmitter, 2 antenna sharing device, 2
a, 2b, 2c ... automatic tuning type band-pass filter, 20,
22, 24 directional coupler, 30 bandpass filter (BPF), 31 dielectric resonator, 32 motor drive circuit, 33 stepping motor, 50 control circuit, 51
... CPU, 60 ... Mixer, 61 ... Low-pass filter (L
PF), 63: A / D conversion circuit, 71: Signal generator, 8
0: Interface circuit, 81: Keyboard, 211
... dielectric resonator, 212 ... dielectric tuning element.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Kubo 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-1-105601 (JP, A) JP-A 4-156723 (JP, A) JP-A-4-156724 (JP, A)

Claims (8)

(57) [Claims] 1. A predetermined reference signal and a signal output from the band-pass filter through the band-pass filter when the reference signal is input to a band-pass filter capable of changing a center frequency. Mixing means for mixing and multiplying the signals to output a signal of a multiplication result; low-pass filtering means for filtering a DC component signal of the multiplication result signal output from the mixing means; Control means for controlling the band-pass filter so that the center frequency of the band-pass filter matches the frequency of the reference signal based on a DC component signal output from the means. Automatic tuning device for filters. 2. The automatic tuning apparatus according to claim 1, wherein the reference signal is a signal input from an external device, and the automatic tuning device further extracts a part of the reference signal input to the band-pass filter and outputs the extracted reference signal to the mixing means. Coupling means; and second coupling means for extracting a part of a signal output from the band-pass filter through the band-pass filter when the reference signal is input to the band-pass filter and outputting the extracted signal to the mixing means. The automatic tuning device according to claim 1, further comprising: 3. The automatic tuning apparatus further comprises: generating means for generating the reference signal and outputting the reference signal to the mixing means; extracting a part of the reference signal generated by the generating means and outputting the reference signal to the band-pass filter. And a fourth coupling means for extracting a part of the signal output from the band-pass filter after passing through the band-pass filter and outputting the extracted signal to the mixing means. 2. The automatic tuning apparatus according to 1. 4. The automatic tuning apparatus further comprises input means for inputting a center frequency to be set by the bandpass filter, and the control means comprises: 4. The automatic tuning apparatus according to claim 3, wherein said generating means is controlled to generate a reference signal having a center frequency to be set. 5. The automatic tuning apparatus further comprises receiving means for receiving, from an external device, information on a center frequency to be set by the band-pass filter, and the control means sets the setting received by the receiving means. 4. The automatic tuning apparatus according to claim 3, wherein said generating means is controlled to generate a reference signal having the center frequency to be set, based on the center frequency to be set. 6. The band pass filter includes a resonator,
The control means calculates a resonance frequency of the resonator based on a DC component signal output from the low-pass filtering means, and a center frequency of the band-pass filter is calculated based on the calculated resonance frequency. 6. The automatic tuning apparatus according to claim 1, wherein said band-pass filter is controlled so as to match a frequency of a reference signal. 7. A band-pass filter according to claim 1, 2, 3, 4, 5, or 6, and an automatic tuning device according to claim 1, 2, 3, 4, 5, or 6. An automatic tuning type band pass filter. 8. The self-tuning bandpass filter according to claim 7, wherein a plurality of the self-tuning bandpass filters are provided, respectively.
7. An antenna sharing device, wherein each output terminal for outputting a signal output from each band-pass filter according to 5 or 6 is electrically connected together.