JPH06276050A - Group delay equalizer and filter - Google Patents

Abstract

PURPOSE:To provide the group delay equalizer and filter which satisfy both high selectivity and a low strain rate at the same time. CONSTITUTION:The group delay equalizer is used in combination with a ceramic filter. A piezoelectric resonator X1 is interposed between an input terminal 1 and an output terminal 2. At least two kind of capacitors are provided. One end of the 1st capacitor C1 is connected to the input side of the piezoelectric resonator X1. One end of the 2nd capacitor C2 is connected to the output side of the piezoelectric resonator X1 and the other end is connected to the other end of the 1st capacitor C1 in common. A 3rd capacitor C3 is preferably provided and connected to the piezoelectric resonator X1 in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group delay equalizer and a filter combining a group delay equalizer and a ceramic filter, and more particularly to a group delay equalizer and a filter capable of simultaneously satisfying high selectivity and low distortion. Related to improvement.

[0002]

2. Description of the Related Art For example, in an IF stage of an FM tuner, a group delay equalizer using a ceramic resonator or the like may be used in order to achieve no adjustment and high stability. FM
A filter used in an IF stage of a tuner is required to have a flat group delay (hereinafter referred to as GDT) characteristic because of a demand for a low distortion rate. On the other hand, also in Japan, due to the era of FM multi-station and the development of car audio and the like, a filter having a high ability of eliminating adjacent stations and a high selectivity is required.

In a ceramic filter, if the selectivity is increased, the distortion of the GDT characteristic becomes large, and conversely, the GDT characteristic becomes larger.
There is a problem that the selectivity becomes poor when the characteristics are flattened to secure a low distortion rate, and it is difficult to simultaneously satisfy the requirements of the low distortion rate by the flattening of the GDT characteristics and the high selectivity. Accompany.

As a prior art document aimed at solving such problems, there is JP-A-62-227207.
In this prior art, at least one set of a first resonator that enters in series with the four-terminal transmission line and a second resonator that enters in parallel with the transmission line is provided, and antiresonance of the first resonator is provided. Frequency and second
The resonator has a different resonance frequency, and when combined with a ceramic filter, high selectivity and low distortion can be satisfied at the same time.

[0005]

However, in the above-mentioned prior art, the attenuation effect outside the pass band is low, and the GD
Since the T characteristic is determined only by the resonance frequency and the anti-resonance frequency of the resonator, there is a problem to be solved such that it is difficult to finely adjust the GDT characteristic.

Therefore, an object of the present invention is to provide a group delay equalizer capable of simultaneously satisfying high selectivity and low distortion when combined with a ceramic filter.

[0007]

In order to solve the above problems, the present invention is a group delay equalizer including a piezoelectric resonator and a capacitor, which is used in combination with a ceramic filter, wherein the piezoelectric resonator is , The capacitor is provided between the input terminal and the output terminal, at least two kinds of the capacitors are provided, and one end of the first capacitor is connected to the input side of the piezoelectric resonator, One end of the capacitor is connected to the output side of the piezoelectric resonator, and the other end is commonly connected to the other end of the first capacitor.

Preferably, a third capacitor is included, and the third capacitor is connected in parallel with the piezoelectric resonator.

[0009]

The piezoelectric resonator is inserted between the input terminal and the output terminal, one end of the first capacitor is connected to the input side of the piezoelectric resonator, and the other end of the second capacitor is the piezoelectric resonator. Is connected to the output side of the first capacitor and the other end is commonly connected to the other end of the first capacitor, the signal input from the input end is, like the conventional general group delay equalizer,
A group delay equalizer that outputs a group delay in a certain frequency range including the selected center frequency is obtained. Also, by combining with a conventional ceramic filter, GDT characteristics can be flattened, distortion can be eliminated, and selectivity can be increased.

When the third capacitor is provided, the attenuation characteristic can be controlled by selecting its capacitance value. Therefore, excellent selectivity can be secured.

When the third capacitor is connected in parallel with the piezoelectric resonator, it is possible to easily obtain an upward convex GDT characteristic by selecting the capacitance value of the third capacitor. The GDT characteristic that is convex upward is the reverse of the GDT characteristic of the conventional ceramic filter. Therefore, in combination with the conventional ceramic filter, the GDT characteristic is further flattened,
Distortion can be eliminated and high selectivity can be achieved. Moreover, the attenuation characteristic can be controlled by selecting the capacitance value of the third capacitor. Therefore, excellent selectivity can be secured. It goes without saying that the flattening of the GDT characteristic and the adjustment of the selectivity are performed in consideration of the constant values of the other components, for example, the first capacitor and the second capacitor.

Since the flattening of the GDT characteristics and the adjustment of the selectivity are performed by selecting the capacitance values of the third capacitor and the first and second capacitors, one resonator or a plurality of resonators having substantially the same characteristics is used. Even when using a single resonator, high selectivity and low distortion can be satisfied at the same time.

[0013]

1 is a symbol diagram of a group delay equalizer according to the present invention. 1 is an input terminal, 2 is an output terminal, 3 is a ground terminal, X1 is a piezoelectric resonator, and C1 to C3 are capacitors. The piezoelectric resonator X1 is inserted in series in the transmission path from the input terminal 1 to the output terminal 2. The piezoelectric resonator X1 is made of piezoelectric ceramic. Capacitor C1
At least three kinds of C3 are provided. The first capacitor C1 has one end connected to the input side of the piezoelectric resonator X1, the second capacitor C2 has one end connected to the output side of the piezoelectric resonator X1, and the other end other than the first capacitor C1. Commonly connected to the end. The third capacitor C3 is connected in parallel with the piezoelectric resonator X1. Although the first capacitor C1 to the third capacitor C3 are shown as one in the figure, a plurality of capacitors are configured in series, in parallel, or in combination thereof, and are equivalently shown in FIG.
They can be combined to form the circuit shown in.

As described above, the piezoelectric resonator X1 is inserted in series in the transmission line, one end of the first capacitor C1 is connected to the input side of the piezoelectric resonator X1, and the second capacitor C2 is connected. Since one end is connected to the output side of the piezoelectric resonator X1 and the other end is commonly connected to the other end of the first capacitor C1, it is input through the transmission line like a conventional general group delay equalizer. A group delay equalizer that outputs the delayed signal by group delay in a certain frequency range including the selected center frequency is obtained.

In addition to the above configuration, a third capacitor C3
Is connected in parallel with the piezoelectric resonator X1, the GD which is convex upward by selecting the capacitance value of the third capacitor C3.
The T characteristic can be easily obtained. GDT convex upward
The characteristics are opposite to the GDT characteristics of the conventional ceramic filter, and therefore, in combination with the conventional ceramic filter, G
It can be used as a group delay equalizer that flattens DT characteristics and eliminates distortion.

Moreover, the attenuation characteristic can be controlled by selecting the capacitance value of the third capacitor C3. For this reason,
Excellent selectivity can be secured. The effect of improving the GDT characteristics and selectivity of the group delay equalizer according to the present invention will be specifically described later based on actual measurement data.

Since the flattening of the GDT characteristic and the adjustment of the selectivity are based on the selection of the capacitance values of the third capacitor C3 and the first and second capacitors C2, one resonator or almost one characteristic can be obtained. Even when a plurality of aligned resonators are used, high selectivity and low distortion can be satisfied at the same time.

FIG. 2 is a symbol diagram showing another embodiment of the group delay equalizer according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. In this embodiment, a plurality of piezoelectric resonators X1 and X2 are provided. The number of piezoelectric resonators X1 and X2 is arbitrary and is not limited to the two shown. Each of the piezoelectric resonators X1 and X2 is inserted in series in the transmission path from the input terminal 1 to the output terminal 2, and both ends of the series circuit are guided to the input side and the output side. In the case of this embodiment, a plurality of piezoelectric resonators X
As a result of including 1 and X2, an effect of improving GDT characteristics and selectivity different from the embodiment of FIG. 1 is obtained.

The group delay equalizer represented by the symbol diagrams shown in FIGS. 1 and 2 can be realized as having various concrete structures. An example thereof is shown in FIGS.

FIG. 3 is a plan view showing a specific structure of the group delay equalizer that can be represented by the symbol diagram of FIG. The piezoelectric resonator X1 and the first capacitors C1 to C3 are provided on the same substrate 10. The substrate 10 is a piezoelectric substrate for the piezoelectric resonator X1 and the first capacitor C1.
To ceramic, which acts as a dielectric substrate for C3. Various ceramic substrates are known.
The piezoelectric resonator X1 is composed of vibrating electrodes 41 and 42 formed so as to face the front and back surfaces of the substrate 10.
The vibrating electrode 41 is guided to one end edge side of the substrate 10 by the lead electrode 11 formed on the back surface side of the substrate 10, and the vibrating electrode 42 is guided to one end edge side of the substrate 10 by the lead electrode 12 formed on the front surface side of the substrate 10. Has been.

The first capacitor C1 is composed of an electrode 13 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate. A dielectric layer (not shown) corresponding to the thickness of the substrate 10 exists between the electrodes 13 and 15. The second capacitor C2 is composed of an electrode 14 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate 10. A dielectric layer (not shown) corresponding to the thickness of the substrate 10 exists between the electrodes 14 and 15.

The third capacitor C3 has a capacitance of the electrode 13
Is obtained by the gap g1 provided between the electrode 14 and the electrode 14. The input terminal 1 is fixed to the lead electrode 11 that is electrically connected to the vibrating electrode 41 on the back surface of the substrate 10 and the lead electrode 17 that is electrically connected to the electrode 13 on the surface of the substrate by soldering or other means. The output terminal 2 includes a lead electrode 12 electrically connected to the vibrating electrode 42 on the front surface of the substrate 10 and a lead electrode 16 disposed on the back surface of the substrate 10.
They are fixed to the and by means such as soldering. The ground terminal 3 is fixed to the electrode 15 arranged on the back surface side of the substrate 10.

The illustrated piezoelectric resonator X1 is assumed to be an energy trap type thickness longitudinal mode oscillator. Although not shown, the finished product is covered with synthetic resin or housed in a case so that a vibration space is formed around the piezoelectric resonator X1.

FIG. 4 is a plan view of a group delay equalizer that can be represented by the symbol diagram shown in FIG. Piezoelectric resonator X1
Is composed of vibrating electrodes 41 and 42 formed so as to face the front and back surfaces of the substrate 10. Piezoelectric resonator X2
Is also constituted by vibrating electrodes 43 and 44 formed so as to face the front and back surfaces of the substrate 10. Piezoelectric resonator X1
The vibrating electrode 41 is guided to the one end edge side of the substrate 10 by the lead electrode 11 formed on the front surface side of the substrate 10, and is continuous with the lead electrode 17 formed on the front surface side. The vibrating electrode 43 of the piezoelectric resonator X2 is guided to the one end edge side of the substrate 10 by the lead electrode 12 formed on the front surface side of the substrate 10,
It is continuous with the lead electrode 18 formed on the front surface side. The vibrating electrodes 42 and 44 are electrically connected to each other by the lead electrode 19 formed on the back surface side of the substrate 10.

The first capacitor C1 is composed of an electrode 13 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate, and the second capacitor C2 is provided on the front surface side of the substrate 10. The third capacitor C3 is configured by the electrode 14 and the electrode 15 provided on the back surface side of the substrate 10. The third capacitor C3 obtains the capacitance by the gap g1 provided between the electrode 13 and the electrode 14. The input terminal 1 is connected to the lead electrode 11 electrically connected to the vibration electrode 41 on the surface of the substrate 10, and the output terminal 2 is connected to the lead electrode 12 electrically connected to the vibration electrode 43 on the surface of the substrate 10.
The ground terminal 3 is an electrode 15 arranged on the back side of the substrate 10.
Connected with.

FIG. 5 is a circuit diagram of an IF unit incorporating a group delay equalizer according to the present invention. FIG. 6 is a plan view showing the same concrete structure. In the figure,
The same reference numerals as those in FIG. 4 denote the same components. Reference numeral 4 is a group delay equalizer according to the present invention, R1 and R2 are resistors, IC is an integrated circuit chip including an amplifier circuit and a limiter, and OS1 and OS2 are resonators. The group delay equalizer 4 according to the present invention is inserted before the integrated circuit chip IC. The group delay equalizer 4 may have the structure shown in FIGS. 3 and 4, or may be composed of individual components.

FIG. 6 shows the IF shown in FIG. 5 using individual parts.
It is a top view which shows the specific example at the time of comprising a unit.
Each component is mounted on the substrate 5 and is connected by using a wiring pattern previously formed on the substrate 5. By trimming the capacitors C1 to C3 forming the group delay equalizer 4 and the added resistors R1 and R2, the capacitance value and the resistance value can be adjusted, and the GDT characteristic and the selectivity can be adjusted.

Next, the effect of the present invention will be specifically described by using actual measurement data. The piezoelectric resonators used to obtain the data all have the following characteristics.

Capacitance Cd = 19.5 pF Electromechanical coupling coefficient Kt = 43.3% Mechanical quality factor Qm = 220 FIG. 7 is a measurement circuit diagram used for confirming the function and effect of the third capacitor C3. 8 to 11 show measured data of frequency-GDT characteristics and insertion loss characteristics obtained using the measuring circuit of FIG. In FIG. 7, S is a signal source, Rin is an input resistance, and Rout is an output resistance.
The input resistance Rin and the output resistance Rout have a resistance value of 330Ω. The capacitance values of the first capacitor C1 to the third capacitor C3 were selected as follows in FIGS. 8 to 11.

In FIG. 8, C1 = C2 = 70 pF and C3 is absent. In FIG. 9, C1 = C2 = 70 pF and C3 = 3 pF. In FIG. 10, C1 = C2 = 70 pF and C3 = 5 pF. In FIG. 11, C1 = C2 = 70 pF and C3 = 7 pF Referring to FIGS. 8 to 11, as the capacitance value of the third capacitor C3 increases, the characteristic that is convex on the GDT characteristic is emphasized. Therefore, it can be used as a group delay equalizer that flattens the GDT characteristic and eliminates distortion by combining it with a ceramic filter having a GDT characteristic that is convex downward. Moreover, by a simple operation of selecting the capacitance value of the third capacitor C3, it is possible to control so as to have the GDT characteristic that matches the GDT characteristic of the ceramic filter to be combined.

Regarding the insertion loss IL, the loss on the high frequency side increases as the capacitance value of the third capacitor C3 increases. Therefore, the amount of attenuation on the high frequency side outside the selected frequency can be increased and the selectivity can be improved.

Next, the difference in effect from the conventional ceramic filter will be described with reference to a specific example of the filter using the group delay equalizer according to the present invention in combination with the ceramic filter. FIG. 12 is a symbol diagram of a conventional ceramic filter, FIG. 13 is its frequency-GDT characteristic,
The attenuation amount characteristic IL is shown. FIG. 14 is a symbol diagram of a filter in which the group delay equalizer according to the present invention is combined with a ceramic filter, and FIG. 15 shows its frequency-GDT characteristic and attenuation amount characteristic IL. 12 and 14, the input resistance Rin and the output resistance Rout have a resistance value of 330Ω. The AMP in FIG. 14 is an amplifier circuit.

As is apparent from FIG. 13, the conventional ceramic filter has a distorted characteristic in which the GDT characteristic is convex downward. On the other hand, in the case of the filter using the group delay equalizer according to the present invention, a flat GDT characteristic is obtained as shown in FIG. As for the amount of attenuation, it can be understood that the present invention has a sharper attenuation outside the selected band than the conventional one, and has excellent selectivity.

Next, the relationship between the number of piezoelectric resonators and the characteristics of the group delay equalizer according to the present invention will be described with reference to FIGS.
Will be described with reference to. FIG. 16 is a characteristic measurement circuit diagram of the group delay equalizer according to the present invention using one piezoelectric resonator X1, and FIG. 17 is its frequency-GDT characteristic and attenuation amount characteristic MG.
Is shown. FIG. 18 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using two piezoelectric resonators X1 and X2, and FIG. 19 shows its frequency-GDT characteristic and attenuation amount characteristic.

Referring to FIG. 17 and FIG. 18, as the number of piezoelectric resonators increases, the characteristic of being convex on the GDT characteristic is emphasized. Therefore, in combination with a ceramic filter having a downwardly convex GDT characteristic, the GDT characteristic can be flattened and distortion can be eliminated by selecting the number of piezoelectric resonators according to the degree of downward convexity. . Moreover, by a simple operation of selecting the number of piezoelectric resonators, a GD that matches the GDT characteristics of the ceramic filter to be combined is formed.
It can be controlled to have T characteristics.

Regarding the insertion loss, the loss outside the selected band increases as the number of piezoelectric resonators increases. Therefore, the amount of attenuation outside the selected frequency can be increased and the selectivity can be improved.

Further, it is easy to set the center frequency of the group delay equalizer according to the present invention to be the same as that of the ceramic filter used at the same time from the operating principle. Therefore, the group delay equalizer and the ceramic filter can be formed of the same piezoelectric substrate.

The present invention discloses a technique for improving the GDT characteristics and the selectivity by controlling the capacitance value of the third capacitor C3 and the number of piezoelectric resonators. The first and second capacitors C1, C2 capacitance value and input / output resistance Ri
The GDT characteristics and the selectivity can be improved also by controlling the resistance values of n and Rout. Then, by combining these techniques, desired characteristics can be obtained.

[0039]

As described above, according to the present invention, it is possible to provide a group delay equalizer that can simultaneously satisfy high selectivity and low distortion.

[Brief description of drawings]

FIG. 1 is a symbol diagram of a group delay equalizer according to the present invention.

FIG. 2 is a symbol diagram showing another embodiment of the group delay equalizer according to the present invention.

3 is a plan view showing a specific structure of a group delay equalizer that can be represented by the symbol diagram of FIG. 1. FIG.

4 is a plan view of a group delay equalizer that can be represented by the symbol diagram shown in FIG.

FIG. 5 is an IF incorporating a group delay equalizer according to the present invention.
It is a circuit diagram of a unit.

6 is a plan view showing a specific structure of the IF unit shown in FIG.

FIG. 7 is a measurement circuit diagram used for confirming the action and effect of the third capacitor.

8 is a frequency-GD obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of T characteristic and insertion loss characteristic.

9 is a frequency-GD obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of T characteristic and insertion loss characteristic.

10 is a frequency-G obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a DT characteristic and an insertion loss characteristic.

11 is a frequency-G obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a DT characteristic and an insertion loss characteristic.

FIG. 12 is a symbol diagram of a conventional ceramic filter.

13 is a diagram showing frequency-GDT characteristics and attenuation amount characteristics of the ceramic filter shown in FIG.

FIG. 14 is a symbol diagram of a filter in which the group delay equalizer according to the present invention is combined with a ceramic filter.

15 is a graph showing frequency-GD by the measuring circuit shown in FIG.
It is a figure which shows T characteristic and attenuation amount characteristic.

FIG. 16 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using one piezoelectric resonator.

17 is a diagram showing frequency-GDT characteristics and attenuation amount characteristics obtained by the measurement circuit shown in FIG.

FIG. 18 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using two piezoelectric resonators.

19 is a diagram showing a frequency-GDT characteristic and an attenuation amount characteristic obtained by the characteristic measuring circuit diagram of FIG.

[Explanation of symbols]

 1 Input Terminal 2 Output Terminal 3 Ground Terminal X1, X2 Piezoelectric Resonator C1 First Capacitor C2 Second Capacitor C3 Third Capacitor

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[Procedure amendment]

[Submission date] June 20, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Group delay equalizer and filter

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group delay equalizer and a filter combining a group delay equalizer and a ceramic filter, and more particularly to a group delay equalizer and a filter capable of simultaneously satisfying high selectivity and low distortion. Related to improvement.

[0002]

2. Description of the Related Art For example, in an IF stage of an FM tuner, a group delay equalizer using a ceramic resonator or the like may be used in order to achieve no adjustment and high stability. FM
A filter used in an IF stage of a tuner is required to have a flat group delay (hereinafter referred to as GDT) characteristic because of a demand for a low distortion rate. On the other hand, also in Japan, due to the era of FM multi-station and the development of car audio and the like, a filter having a high ability of eliminating adjacent stations and a high selectivity is required.

In a ceramic filter, if the selectivity is increased, the distortion of the GDT characteristic becomes large, and conversely, the GDT characteristic becomes larger.
There is a problem that the selectivity becomes poor when the characteristics are flattened to secure a low distortion rate, and it is difficult to simultaneously satisfy the requirements of the low distortion rate by the flattening of the GDT characteristics and the high selectivity. Accompany.

As a prior art document aimed at solving such problems, there is JP-A-62-227207.
In this prior art, at least one set of a first resonator that enters in series with the four-terminal transmission line and a second resonator that enters in parallel with the transmission line is provided, and antiresonance of the first resonator is provided. Frequency and second
The resonator has a different resonance frequency, and when combined with a ceramic filter, high selectivity and low distortion can be satisfied at the same time.

[0005]

However, in the above-mentioned prior art, the attenuation effect outside the pass band is low, and the GD
Since the T characteristic is determined only by the resonance frequency and the anti-resonance frequency of the resonator, there is a problem to be solved such that it is difficult to finely adjust the GDT characteristic.

Therefore, an object of the present invention is to provide a group delay equalizer capable of simultaneously satisfying high selectivity and low distortion when combined with a ceramic filter.

[0007]

In order to solve the above problems, the present invention is a group delay equalizer including a piezoelectric resonator and a capacitor, which is used in combination with a ceramic filter, wherein the piezoelectric resonator is , The capacitor is provided between the input terminal and the output terminal, at least two kinds of the capacitors are provided, and one end of the first capacitor is connected to the input side of the piezoelectric resonator, One end of the capacitor is connected to the output side of the piezoelectric resonator, and the other end is commonly connected to the other end of the first capacitor.

Preferably, a third capacitor is included, and the third capacitor is connected in parallel with the piezoelectric resonator.

[0009]

The piezoelectric resonator is inserted between the input terminal and the output terminal, one end of the first capacitor is connected to the input side of the piezoelectric resonator, and the other end of the second capacitor is the piezoelectric resonator. Is connected to the output side of the first capacitor and the other end is commonly connected to the other end of the first capacitor, the signal input from the input end is, like the conventional general group delay equalizer,
A group delay equalizer for delaying and outputting in a certain frequency range including the selected center frequency can be obtained. Also, by combining with a conventional ceramic filter, GDT characteristics can be flattened, distortion can be eliminated, and selectivity can be increased.

When the third capacitor is provided, the attenuation characteristic can be controlled by selecting its capacitance value. Therefore, excellent selectivity can be secured.

When the third capacitor is connected in parallel with the piezoelectric resonator, it is possible to easily obtain an upward convex GDT characteristic by selecting the capacitance value of the third capacitor. The GDT characteristic that is convex upward is the reverse of the GDT characteristic of the conventional ceramic filter. Therefore, in combination with the conventional ceramic filter, the GDT characteristic is further flattened,
Distortion can be eliminated and high selectivity can be achieved. Moreover, the attenuation characteristic can be controlled by selecting the capacitance value of the third capacitor. Therefore, excellent selectivity can be secured. It goes without saying that the flattening of the GDT characteristic and the adjustment of the selectivity are performed in consideration of the constant values of the other components, for example, the first capacitor and the second capacitor.

Since the flattening of the GDT characteristics and the adjustment of the selectivity are performed by selecting the capacitance values of the third capacitor and the first and second capacitors, one resonator or a plurality of resonators having substantially the same characteristics is used. Even when using a single resonator, high selectivity and low distortion can be satisfied at the same time.

[0013]

1 is a symbol diagram of a group delay equalizer according to the present invention. 1 is an input terminal, 2 is an output terminal, 3 is a ground terminal, X1 is a piezoelectric resonator, and C1 to C3 are capacitors. The piezoelectric resonator X1 is inserted in series in the transmission path from the input terminal 1 to the output terminal 2. The piezoelectric resonator X1 is made of piezoelectric ceramic. Capacitor C1
At least three kinds of C3 are provided. The first capacitor C1 has one end connected to the input side of the piezoelectric resonator X1, the second capacitor C2 has one end connected to the output side of the piezoelectric resonator X1, and the other end other than the first capacitor C1. Commonly connected to the end. The third capacitor C3 is connected in parallel with the piezoelectric resonator X1. Although the first capacitor C1 to the third capacitor C3 are shown as one in the figure, a plurality of capacitors are configured in series, in parallel, or in combination thereof, and are equivalently shown in FIG.
They can be combined to form the circuit shown in.

As described above, the piezoelectric resonator X1 is inserted in series in the transmission line, one end of the first capacitor C1 is connected to the input side of the piezoelectric resonator X1, and the second capacitor C2 is connected. Since one end is connected to the output side of the piezoelectric resonator X1 and the other end is commonly connected to the other end of the first capacitor C1, it is input through the transmission line like a conventional general group delay equalizer. the signals, in a range of frequencies including the selected center frequency, the group delay equalizer for delaying and outputting is obtained.

In addition to the above configuration, a third capacitor C3
Is connected in parallel with the piezoelectric resonator X1, the GD which is convex upward by selecting the capacitance value of the third capacitor C3.
The T characteristic can be easily obtained. GDT convex upward
The characteristics are opposite to the GDT characteristics of the conventional ceramic filter, and therefore, in combination with the conventional ceramic filter, G
It can be used as a group delay equalizer that flattens DT characteristics and eliminates distortion.

Moreover, the attenuation characteristic can be controlled by selecting the capacitance value of the third capacitor C3. For this reason,
Excellent selectivity can be secured. The effect of improving the GDT characteristics and selectivity of the group delay equalizer according to the present invention will be specifically described later based on actual measurement data.

Since the flattening of the GDT characteristic and the adjustment of the selectivity are based on the selection of the capacitance values of the third capacitor C3 and the first and second capacitors C2, one resonator or almost one characteristic can be obtained. Even when a plurality of aligned resonators are used, high selectivity and low distortion can be satisfied at the same time.

FIG. 2 is a symbol diagram showing another embodiment of the group delay equalizer according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. In this embodiment, a plurality of piezoelectric resonators X1 and X2 are provided. The number of piezoelectric resonators X1 and X2 is arbitrary and is not limited to the two shown. Each of the piezoelectric resonators X1 and X2 is inserted in series in the transmission path from the input terminal 1 to the output terminal 2, and both ends of the series circuit are guided to the input side and the output side. In the case of this embodiment, a plurality of piezoelectric resonators X
As a result of including 1 and X2, an effect of improving GDT characteristics and selectivity different from the embodiment of FIG. 1 is obtained.

The group delay equalizer represented by the symbol diagrams shown in FIGS. 1 and 2 can be realized as having various concrete structures. An example thereof is shown in FIGS.

FIG. 3 is a plan view showing a specific structure of the group delay equalizer that can be represented by the symbol diagram of FIG. The piezoelectric resonator X1 and the first capacitors C1 to C3 are formed on the same substrate 10. The substrate 10 is a piezoelectric substrate for the piezoelectric resonator X1 and the first capacitors C1 to C3.
It consists of a ceramic that functions as a dielectric substrate for.
Various ceramic substrates are known. The piezoelectric resonator X1 is composed of vibrating electrodes 41 and 42 formed so as to face the front and back surfaces of the substrate 10. The vibrating electrode 41 is the lead electrode 11 formed on the back surface side of the substrate 10.
Is guided to the one end edge side of the substrate 10, and the vibrating electrode 42 is guided to the one end edge side of the substrate 10 by the lead electrode 12 formed on the front surface side of the substrate 10.

The first capacitor C1 is composed of an electrode 13 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate. A dielectric layer (not shown) corresponding to the thickness of the substrate 10 exists between the electrodes 13 and 15. The second capacitor C2 is composed of an electrode 14 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate 10. A dielectric layer (not shown) corresponding to the thickness of the substrate 10 exists between the electrodes 14 and 15.

The third capacitor C3 has a capacitance of the electrode 13
Is obtained by the gap g1 provided between the electrode 14 and the electrode 14. The input terminal 1 is fixed to the lead electrode 11 that is electrically connected to the vibrating electrode 41 on the back surface of the substrate 10 and the lead electrode 17 that is electrically connected to the electrode 13 on the surface of the substrate by soldering or other means. The output terminal 2 includes a lead electrode 12 electrically connected to the vibrating electrode 42 on the front surface of the substrate 10 and a lead electrode 16 disposed on the back surface of the substrate 10.
They are fixed to the and by means such as soldering. The ground terminal 3 is fixed to the electrode 15 arranged on the back surface side of the substrate 10.

The illustrated piezoelectric resonator X1 is assumed to be an energy trap type thickness longitudinal mode oscillator. Although not shown, the finished product is covered with synthetic resin or housed in a case so that a vibration space is formed around the piezoelectric resonator X1.

FIG. 4 is a plan view of a group delay equalizer that can be represented by the symbol diagram shown in FIG. Piezoelectric resonator X1
Is composed of vibrating electrodes 41 and 42 formed so as to face the front and back surfaces of the substrate 10. Piezoelectric resonator X2
Is also constituted by vibrating electrodes 43 and 44 formed so as to face the front and back surfaces of the substrate 10. Piezoelectric resonator X1
The vibrating electrode 41 is guided to the one end edge side of the substrate 10 by the lead electrode 11 formed on the front surface side of the substrate 10, and is continuous with the lead electrode 17 formed on the front surface side. The vibrating electrode 43 of the piezoelectric resonator X2 is guided to the one end edge side of the substrate 10 by the lead electrode 12 formed on the front surface side of the substrate 10,
It is continuous with the lead electrode 18 formed on the front surface side. The vibrating electrodes 42 and 44 are electrically connected to each other by the lead electrode 19 formed on the back surface side of the substrate 10.

The first capacitor C1 is composed of an electrode 13 provided on the front surface side of the substrate 10 and an electrode 15 provided on the back surface side of the substrate, and the second capacitor C2 is provided on the front surface side of the substrate 10. The third capacitor C3 is configured by the electrode 14 and the electrode 15 provided on the back surface side of the substrate 10. The third capacitor C3 obtains the capacitance by the gap g1 provided between the electrode 13 and the electrode 14. The input terminal 1 is connected to the lead electrode 11 electrically connected to the vibration electrode 41 on the surface of the substrate 10, and the output terminal 2 is connected to the lead electrode 12 electrically connected to the vibration electrode 43 on the surface of the substrate 10.
The ground terminal 3 is an electrode 15 arranged on the back side of the substrate 10.
Connected with.

FIG. 5 is a circuit diagram of an IF unit incorporating a group delay equalizer according to the present invention. FIG. 6 is a plan view showing the same concrete structure. In the figure,
The same reference numerals as those in FIG. 4 denote the same components. Reference numeral 4 is a group delay equalizer according to the present invention, R1 and R2 are resistors, IC is an integrated circuit chip including an amplifier circuit and a limiter, and CF1 and CF2 are ceramic filters . The group delay equalizer 4 according to the present invention is inserted before the integrated circuit chip IC. The group delay equalizer 4 may have the structure shown in FIGS. 3 and 4, or may be composed of individual components.

FIG. 6 shows the IF shown in FIG. 5 using individual parts.
It is a top view which shows the specific example at the time of comprising a unit.
Each component is mounted on the substrate 5 and is connected by using a wiring pattern previously formed on the substrate 5. By trimming the capacitors C1 to C3 forming the group delay equalizer 4 and the added resistors R1 and R2, the capacitance value and the resistance value can be adjusted, and the GDT characteristic and the selectivity can be adjusted.

Next, the effect of the present invention will be specifically described by using actual measurement data. The piezoelectric resonators used to obtain the data all have the following characteristics.

Capacitance Cd = 19.5 pF Electromechanical coupling coefficient Kt = 43.3% Mechanical quality factor Qm = 220 FIG. 7 is a measurement circuit diagram used for confirming the function and effect of the third capacitor C3. 8 to 11 show frequency-GDT characteristics and attenuation characteristics obtained by using the measurement circuit of FIG.
The actual measurement data of sex are shown. In FIG. 7, S is a signal source, Rin is an input resistance, and Rout is an output resistance. The input resistance Rin and the output resistance Rout have a resistance value of 330Ω. First capacitor C1 to third capacitor C
The capacitance value of No. 3 was selected as follows in FIGS.

In FIG. 8, C1 = C2 = 70 pF and C3 is absent. In FIG. 9, C1 = C2 = 70 pF and C3 = 3 pF. In FIG. 10, C1 = C2 = 70 pF and C3 = 5 pF. In FIG. 11, C1 = C2 = 70 pF and C3 = 7 pF Referring to FIGS. 8 to 11, as the capacitance value of the third capacitor C3 increases, the characteristic that is convex on the GDT characteristic is emphasized. Therefore, it can be used as a group delay equalizer that flattens the GDT characteristic and eliminates distortion by combining it with a ceramic filter having a GDT characteristic that is convex downward. Moreover, by a simple operation of selecting the capacitance value of the third capacitor C3, it is possible to control so as to have the GDT characteristic that matches the GDT characteristic of the ceramic filter to be combined.

Regarding the attenuation amount ATT , the attenuation amount on the high frequency side increases as the capacitance value of the third capacitor C3 increases. Therefore, it is possible to increase the attenuation amount on the high frequency side outside the pass band and improve the selectivity.

Next, the difference in effect from the conventional ceramic filter will be described with reference to a specific example of the filter using the group delay equalizer according to the present invention in combination with the ceramic filter. FIG. 12 shows a symbol diagram of the conventional ceramic filter CF , and FIG. 13 shows the frequency-GDT characteristic and the attenuation amount characteristic ATT of the same. FIG. 14 is a symbol diagram of a filter in which the group delay equalizer according to the present invention is combined with a ceramic filter CF, and FIG. 15 is its frequency-GD.
The T characteristic and the attenuation amount characteristic ATT are shown. 12 and 14, the input resistance Rin and the output resistance Rout have a resistance value of 330Ω. The AMP in FIG. 14 is an amplifier circuit.

As is apparent from FIG. 13, the conventional ceramic filter has a distorted characteristic in which the GDT characteristic is convex downward. On the other hand, in the case of the filter using the group delay equalizer according to the present invention, a flat GDT characteristic is obtained as shown in FIG. As for the amount of attenuation, it can be understood that the present invention has a sharper attenuation outside the selected band than the conventional one, and has excellent selectivity.

Next, the relationship between the number of piezoelectric resonators and the characteristics of the group delay equalizer according to the present invention will be described with reference to FIGS.
Will be described with reference to. FIG. 16 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using one piezoelectric resonator X1, and FIG. 17 is its frequency-GDT characteristic and attenuation characteristic AT.
T is shown. FIG. 18 shows two piezoelectric resonators X1 and X2.
FIG. 19 is a characteristic measurement circuit diagram of the group delay equalizer according to the present invention using FIG. 19 and shows its frequency-GDT characteristic and attenuation amount characteristic.

Referring to FIG. 17 and FIG. 18, as the number of piezoelectric resonators increases, the characteristic of being convex on the GDT characteristic is emphasized. Therefore, in combination with a ceramic filter having a downwardly convex GDT characteristic, the GDT characteristic can be flattened and distortion can be eliminated by selecting the number of piezoelectric resonators according to the degree of downward convexity. . Moreover, by a simple operation of selecting the number of piezoelectric resonators, a GD that matches the GDT characteristics of the ceramic filter to be combined is formed.
It can be controlled to have T characteristics.

Regarding the attenuation amount , the attenuation amount outside the pass band increases as the number of piezoelectric resonators increases. For this reason, through
It is possible to increase the amount of attenuation outside the overband and improve the selectivity.

Further, it is easy to set the center frequency of the group delay equalizer according to the present invention to be the same as that of the ceramic filter used at the same time from the operating principle. Therefore, the group delay equalizer and the ceramic filter can be formed of the same piezoelectric substrate.

The present invention discloses a technique for improving the GDT characteristics and the selectivity by controlling the capacitance value of the third capacitor C3 and the number of piezoelectric resonators. The first and second capacitors C1, C2 capacitance value and input / output resistance Ri
The GDT characteristics and the selectivity can be improved also by controlling the resistance values of n and Rout. Then, by combining these techniques, desired characteristics can be obtained.

[0039]

As described above, according to the present invention, it is possible to provide a group delay equalizer that can simultaneously satisfy high selectivity and low distortion.

[Brief description of drawings]

FIG. 1 is a symbol diagram of a group delay equalizer according to the present invention.

FIG. 2 is a symbol diagram showing another embodiment of the group delay equalizer according to the present invention.

3 is a plan view showing a specific structure of a group delay equalizer that can be represented by the symbol diagram of FIG. 1. FIG.

4 is a plan view of a group delay equalizer that can be represented by the symbol diagram shown in FIG.

FIG. 5 is an IF incorporating a group delay equalizer according to the present invention.
It is a circuit diagram of a unit.

6 is a plan view showing a specific structure of the IF unit shown in FIG.

FIG. 7 is a measurement circuit diagram used for confirming the action and effect of the third capacitor.

8 is a frequency-GD obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a T characteristic and an attenuation amount characteristic .

9 is a frequency-GD obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a T characteristic and an attenuation amount characteristic .

10 is a frequency-G obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a DT characteristic and an attenuation amount characteristic .

11 is a frequency-G obtained using the measurement circuit of FIG.
It is a figure which shows the measured data of a DT characteristic and an attenuation amount characteristic .

FIG. 12 is a symbol diagram of a conventional ceramic filter.

13 is a diagram showing frequency-GDT characteristics and attenuation amount characteristics of the ceramic filter shown in FIG.

FIG. 14 is a symbol diagram of a filter in which the group delay equalizer according to the present invention is combined with a ceramic filter.

15 is a graph showing frequency-GD by the measuring circuit shown in FIG.
It is a figure which shows T characteristic and attenuation amount characteristic.

FIG. 16 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using one piezoelectric resonator.

17 is a diagram showing frequency-GDT characteristics and attenuation amount characteristics obtained by the measurement circuit shown in FIG.

FIG. 18 is a characteristic measurement circuit diagram of a group delay equalizer according to the present invention using two piezoelectric resonators.

19 is a diagram showing a frequency-GDT characteristic and an attenuation amount characteristic obtained by the characteristic measuring circuit diagram of FIG.

[Explanation of reference numerals] 1 input terminal 2 output terminal 3 ground terminal X1, X2 piezoelectric resonator C1 first capacitor C2 second capacitor C3 third capacitor

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

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[Figure 6]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 7]

[Figure 8]

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[Figure 10]

FIG. 11

[Fig. 12]

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FIG. 14

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FIG. 17

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FIG. 19

Claims (8)

[Claims] 1. A group delay equalizer including a piezoelectric resonator and a capacitor, which is used in combination with a ceramic filter, wherein the piezoelectric resonator is inserted between an input terminal and an output terminal, At least two types of capacitors are provided, one end of the first capacitor is connected to the input side of the piezoelectric resonator, and one end of the second capacitor is connected to the output side of the piezoelectric resonator, A group delay equalizer having the other end commonly connected to the other end of the first capacitor. 2. The group delay equalizer according to claim 1, further comprising a third capacitor, wherein the third capacitor is connected in parallel with the piezoelectric resonator. 3. The piezoelectric resonator according to claim 1, wherein a plurality of the piezoelectric resonators are provided, each of which is inserted in series in the transmission line, and both ends of a series circuit are guided to the input side and the output side. Group delay equalizer. 4. The piezoelectric resonator and the capacitor are
The group delay equalizer according to claim 1, 2 or 3, which is provided on the same substrate. 5. The group delay equalizer according to claim 4, wherein the substrate is a ceramic that functions as a piezoelectric substrate for the piezoelectric resonator and a dielectric substrate for the capacitor. 6. The piezoelectric resonator and the capacitor are
The group delay equalizer according to claim 4, wherein the group delay equalizer is a discrete component and is mounted on the substrate. 7. A filter having a group delay equalizer and a ceramic filter, wherein the group delay equalizer is the filter according to any one of claims 1 to 6 and is connected to the ceramic filter. filter. 8. The filter according to claim 7, wherein the group delay equalizer and the ceramic filter are formed on the same piezoelectric substrate.