CN109951172A - Piezoelectric filter device - Google Patents
Piezoelectric filter device Download PDFInfo
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- CN109951172A CN109951172A CN201811182466.2A CN201811182466A CN109951172A CN 109951172 A CN109951172 A CN 109951172A CN 201811182466 A CN201811182466 A CN 201811182466A CN 109951172 A CN109951172 A CN 109951172A
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Abstract
The present invention relates to piezoelectric filter devices, are able to use the width that single piezoelectric filter corresponds to passband width.The input side of the piezoelectric filter (2) for four polar forms for making for ambipolar two piezoelectric filter elements cascade to be formed by connecting by the first impedance circuit (5) and the second impedance circuit (6) is different from the impedance of outlet side, and deviate the centre frequency of two piezoelectric filter elements mutually, pass through the first switching switch (3) and the second switching switch (4), switching is directed to the input and output direction of the signal of piezoelectric filter (2), thus the width of the passband width of switching signal.
Description
Technical field
The present invention relates to piezoelectric filter devices used in communication equipments such as commercial wireless devices and portable telephone etc..
Background technique
Piezoelectric filter, the piezoelectric filter of piezoelectric substrate such as using AT cutting quartz plate generally have in piezoelectricity base
One face of plate forms input electrode and output electrode, and corresponding with the input and output electrode total in the formation of another face
The structure of same electrode (grounding electrode).There are two electrodes pair due to clipping piezoelectric substrate tool for this structure, referred to as bipolar
The piezoelectric filter of type has to improve the characteristic of piezoelectric filter by this ambipolar piezoelectric filter cascade connection
Made of four polar forms piezoelectric filter (for example, referring to patent document 1).
However, the communication equipment of piezoelectric filter is stated in use, in such as commercial wireless devices, to efficiently use frequency
For the purpose of section, the confidentiality (secret protection) for improving communication etc., is promoting and turning from previous analog form to digital form
Become.
Patent document 1: No. 3507206 bulletins of Japanese Patent No.
In previous commercial wireless devices, existing can both modes be communicated with digital form in an analog fashion
Commercial wireless devices.But it is possible to wide with the passband that the commercial wireless devices that above-mentioned two ways is communicated have signal
The piezoelectric filter of the narrow digital form of the passband width of the piezoelectric filter and signal of spending wide analog form, to two
Piezoelectric filter switches over.Therefore, the piezoelectric filter and signal of the analog form wide with the passband width that has signal
The narrow piezoelectric filter of digital form the two piezoelectric filters of passband width correspondingly, cost can be improved and be needed
Space.
Accordingly, it is desirable to be able to by single piezoelectric filter, corresponding analog form and digital form.
Summary of the invention
The present invention is in view of the above problem, it is therefore intended that single piezoelectric filter is able to use, to the passband of induction signal
The width of width.
In the present invention, in order to achieve the above object, it constitutes as follows.
That is, piezoelectric filter device of the invention has the piezoelectricity filter that two piezoelectric filter element cascades are formed by connecting
Wave device, described two piezoelectric filter elements are formed with input electrode and output electrode in an interarea of piezoelectric substrate, another
One interarea is formed with the common electrode opposed with the input electrode and the output electrode, described two piezoelectric filter members
The respective centre frequency of part mutually deviates, and the impedance of the input side of the piezoelectric filter and the impedance of outlet side are different,
By switching the input and output direction of the signal for the piezoelectric filter, carry out the width of the passband width of switching signal.
According to the present invention, it deviates the centre frequency of two piezoelectric filter elements mutually, and makes two piezoelectricity filtering
The input side for the piezoelectric filter that the cascade of device element is formed by connecting is different from the impedance of outlet side.Therefore, by switching for pressure
The input and output direction of the signal of electrical filter, so that the filter characteristic of two piezoelectric filter elements is with described
The mode that the deviation of centre frequency becomes larger or becomes smaller deviates.Accordingly, the filter characteristic of two piezoelectric filter elements is synthesized,
Can constriction or widen signal passband width.Moreover, can be only by a piezoelectric filter and a circuit connected to it
It constitutes.Therefore, it can become and be conducive to save space-efficient structure.
Preferably, the piezoelectric substrate is set as two pieces, described two respective input electricity of piezoelectric filter element
Pole, the output electrode and the common electrode are respectively formed in respective one piece of piezoelectric substrate.
According to this structure, input electrode, output electrode and common electrode are formed in individually each piezoelectric substrate, respectively constituted
Piezoelectric filter element.Therefore, disconnected from each other on sound equipment, two piezoelectric filter elements are formed in common piezoelectric substrate
Input electrode, the structure of output electrode and common electrode compare, be able to suppress spuious and improve filter characteristic.
Preferably, have: switch unit, by the way that the input terminal switching of the piezoelectric filter device is connected to the pressure
The input side or the outlet side of electrical filter, and the switching of the output terminal of the piezoelectric filter device is connected to institute
The outlet side or the input side of piezoelectric filter are stated, to switch the input and output direction of the signal.
According to this structure, by controlling switch unit, so as to easily switch the signal for piezoelectric filter
Input and output direction.Be conducive to save space-efficient circuit structure moreover, can become.
Preferably, between the input terminal of the piezoelectric filter device and the switch unit and in the pressure
Between the output terminal and the switch unit of electrical filter device, it is respectively arranged with the impedance for making the input side and institute
State the mutually different impedance circuit of impedance of outlet side.
According to this structure, by impedance circuit, the impedance of the input side and outlet side of piezoelectric filter can be set separately.
Preferably, the piezoelectric substrate is quartz base plate.
According to this structure, so that frequency-temperature characteristic is good.
As described above, according to the present invention, by switching the input and output direction of the signal for piezoelectric filter, so as to
Deviate the filter characteristic of two piezoelectric filter elements in such a way that the deviation of its centre frequency becomes larger or becomes smaller, according to
This, the filter characteristic of two piezoelectric filter elements is synthesized, can constriction or widen signal passband width.
Therefore, pass through single piezoelectric filter, it will be able to the width of the passband width of switching signal, for example, in commercialization
In wireless device, can by the piezoelectric filter device under analog form and digital form both modes dual-purpose.Accordingly, with
The piezoelectric filter of the piezoelectric filter of the analog form for needing the passband width of signal different and digital form the two
The commercial wireless devices of the conventional example of piezoelectric filter are compared, and can reduce cost, and be can be realized and saved space.
Detailed description of the invention
Fig. 1 is the schematic structural diagram of the piezoelectric filter device of one embodiment of the present invention.
Fig. 2 is the longitudinal section view of the piezoelectric filter of Fig. 1.
Fig. 3 is the top view for removing the state after lid of the piezoelectric filter of Fig. 2.
Fig. 4 is the schematic diagram for showing the structure of piezoelectric filter of Fig. 2.
Fig. 5 is with Fig. 1 corresponding outline of the switching for the state behind the input and output direction of the signal of piezoelectric filter
Structure chart.
Fig. 6 is to show switching to be set as digital form or simulation side for the input and output direction of the signal of piezoelectric filter
The figure of filter characteristic when formula, (a) show filter characteristic when digital form, (b) show filter when analog form
Characteristic.
Filter when Fig. 7 is for illustrating that the input and output direction for the signal of piezoelectric filter is digital form is special
The figure of property.
Filter when Fig. 8 is for illustrating that the input and output direction for the signal of piezoelectric filter is analog form is special
The figure of property.
Fig. 9 is to show switching to be set as digital form or simulation side for the input and output direction of the signal of piezoelectric filter
The figure of the filter characteristic in wide area when formula, (a) show filter characteristic when digital form, when (b) showing analog form
Filter characteristic.
Description of symbols
1 piezoelectric filter device
2 piezoelectric filters
3 first switching switches
4 second switching switches
5 first impedance circuits
6 second impedance circuits
7 pedestals
8 first piezoelectric filter elements
9 second piezoelectric filter elements
11 first piezoelectric substrates
12 second piezoelectric substrates
21 first external connection terminals
24 the 4th external connection terminals
27 input terminals
28 output terminals
Specific embodiment
In the following, detailed description of embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 is the schematic structural diagram of piezoelectric filter device 1 involved in one embodiment of the present invention.
The piezoelectric filter device 1 of the embodiment has: piezoelectric filter 2；First switching switch 3 and the second switching are opened
4 are closed, the switch unit switched over as the input and output direction to the signal for the piezoelectric filter 2；And first resistance
Reactive circuit 5 and the second impedance circuit 6, for keeping the impedance of input side and outlet side of piezoelectric filter 2 different.
In the present invention, although being switched over to the input and output direction of the signal for piezoelectric filter 2, it is first
First, on the state in the input and output direction of non-switching signal, signal i.e. as in the past input and output direction premised on, it is right
The structure of piezoelectric filter 2 is illustrated.In addition, Fig. 1 show the input and output direction of non-switching signal state, i.e. with it is previous
The state in the input and output direction of identical signal.
The piezoelectric filter 2 of the embodiment is by two ambipolar piezoelectric filter element cascade connections as described later
Made of four polar forms piezoelectric filter.Here, " cascade connection " refers to the defeated of ambipolar piezoelectric filter element
Electrode is connected to the input electrode of another ambipolar piezoelectric filter element out.
Fig. 2 is the longitudinal section view of the piezoelectric filter 2 of Fig. 1, Fig. 3 be the piezoelectric filter 2 of Fig. 2 remove lid 10 after
The top view of state, Fig. 4 are the schematic diagrames for showing the structure of piezoelectric filter 2 of Fig. 2.
The piezoelectric filter 2 of the embodiment has: pedestal 7 made of ceramics；Two piezoelectric filter elements i.e. first are pressed
Electrical filter element 8 and the second piezoelectric filter element 9, are contained in the pedestal 7；And lid 10, pedestal 7 is carried out airtight
Encapsulation.Lid 10 is such as by Kovar alloy (コ バ ー Le) metal plate constitute.
The pedestal 7 of the embodiment with aluminium oxide etc. for the ceramic multi-layer baseplate of base material by being constituted.In this embodiment,
Pedestal 7 be overlook substantially rectangular flat lower layer 7a, the stage portion for being formed in the formation of the top lower layer 7a middle layer 7b, with
And the upper layer 7c of frame portion this three-decker for being formed in that peripheral part on the 7b of the middle layer formed.In pedestal 7, pass through this three layers of 7a
~7c, constitutes the housing recess 13 with stage portion, and stage portion storage keeps the first piezoelectric filter element 8 and the second piezoelectricity
Filter element 9.
First piezoelectric filter element 8 and the second piezoelectric filter element 9 for example have the quartzy base cut by AT respectively
The first piezoelectric substrate 11 and the second piezoelectric substrate 12 that plate is constituted.
In the upper surface of the middle layer 7b of pedestal 7, the i.e. stage portion of the housing recess 13 of pedestal 7, it is formed with for electrical machine
Keep to tool carrying the first input pad 14, the first o pads 15 and the first ground pad of the first piezoelectric substrate 11
16.Similarly, it is defeated to be formed with the second input pad 17, second for for electricapparatus keeping carrying the second piezoelectric substrate 12
Pad 18 and the second ground pad 19 out.
It is empty respectively in an interarea, that is, back side (lower surface) of the first piezoelectric substrate 11 of the first piezoelectric filter element 8
Open input electrode 111 and output electrode 112 that spacing parallel arranging is formed with rectangle.These electrodes 111,112 are respectively drawn out to the
The opposed corner of one piezoelectric substrate 11 passes through conductive adhesive with above-mentioned first input pad 14 and the first o pads 15
20 connect with distinguishing electrical resistance.
On another interarea, that is, surface (upper surface) of the first piezoelectric substrate 11, be formed with the input electrode 111 and
Grounding electrode, that is, common electrode 113 of the corresponding rectangle of output electrode 112.The common electrode 113 is drawn out to the first piezoelectricity base
Another corner of plate 11 is connect with above-mentioned first ground pad 16 by 20 electrical resistance of conductive adhesive.
It is also same as the first piezoelectric substrate 11 in the second piezoelectric substrate 12 of the second piezoelectric filter element 9, overleaf divide
It is not formed with the input electrode 121 and output electrode 122 of rectangle.These electrodes 121,122 are respectively drawn out to the second piezoelectricity base
The opposed corner of plate 12 passes through 20 electrical resistance of conductive adhesive with above-mentioned second input pad 17 and the second o pads 18
Ground connection.On the surface of the second piezoelectric substrate 12, it is formed with corresponding with the input electrode 121 and the output electrode 122
Grounding electrode, that is, common electrode 123 of rectangle.The common electrode 123 is drawn out to another corner of the second piezoelectric substrate 12,
It is connect with above-mentioned second ground pad 19 by 20 electrical resistance of conductive adhesive.
In the bottom surface of pedestal 7, it is formed with six external connection terminals i.e. first of Fig. 1 and surface installation shown in Fig. 4
~the six external connection terminals 21~26.These external connection terminals 21~26 are (not shown) inside pedestal 7
It is routed (wiring pattern or via hole etc.), it is defeated with the first input pad 14, the first o pads 15, the first ground pad 16, second
It connects with entering pad 17, the second o pads 18,19 electrical resistance of the second ground pad.Therefore, these external connection terminals 21~
26 each electrode via each pad 14~19 and conductive adhesive 20, with the first piezoelectric substrate 11 and the second piezoelectric substrate 12
111~113,121~123 connect with distinguishing electrical resistance.
Specifically, as shown in figure 4, the input electrode 111 of the first piezoelectric substrate 11 and the first external connection terminals 21,
The common electrode 113 of one piezoelectric substrate 11 and the second external connection terminals 22, the output electrode 112 of the first piezoelectric substrate 11 and
Three external connection terminals 23 are separately connected.
In addition, the output electrode 122 of the second piezoelectric substrate 12 and the 4th external connection terminals 24, the second piezoelectric substrate 12
Common electrode 123 and the 5th external connection terminals 25, the input electrode 121 of the second piezoelectric substrate 12 and the 6th external connection terminals
26 are separately connected.
In addition, showing each terminal number (pin number) # of each external connection terminals 21~26 together in Fig. 1 and Fig. 4
1~#6, No. 1 terminal #1 i.e. the first external connection terminals 21 are equivalent to existing input terminal, connect outside No. 4 terminal #4 the i.e. the 4th
Connecting terminal 24 is equivalent to existing output terminal.
The second external connection terminals 22 for being connect with the common electrode 113 of the first piezoelectric substrate 11 and with the second piezoelectric substrate
The 5th external connection terminals 25 that 12 common electrode 123 connects, as shown in Figure 1, being grounded respectively as ground terminal.
The third external connection terminals 23 that are connect with the output electrode 112 of the first piezoelectric filter element 8 and with the second pressure
The 6th external connection terminals 26 that the input electrode 121 of electrical filter element 9 connects are connected to coupling capacitor C3 jointly.
In this way, the input electrode of the output electrode 112 of the first piezoelectric filter element 8 and the second piezoelectric filter element 9
121 interconnect, and composition will be two ambipolar piezoelectric filter elements i.e. the first piezoelectric filter element 8 and the second pressure
The piezoelectric filter 2 of four polar forms made of 9 cascade connection of electrical filter element.
The above are with the input and output side of the state in the input and output direction of non-switching signal, signal i.e. as in the past
The structure of piezoelectric filter 2 premised on.
In this embodiment, as is shown in phantom in fig. 3, make the input electrode of the rectangle of the first piezoelectric filter element 8
111 and output electrode 112 aspect ratio and the second piezoelectric filter element 9 rectangle input electrode 121 and output electrode 122
Aspect ratio it is different, input electrode 111 and output electrode 112 are set as approximate rectangular shape, input electrode 121 and output electricity
Pole 122 is set as the shape of approximating square, it is suppressed that spuious.In addition, the electrode shape of two piezoelectric filter elements 8,9 can also
To be set as identical.
The piezoelectric filter device 1 of the embodiment be used to promote the quotient changed from analog form to digital form
With the wireless set of wireless device, such as outdoor.
In piezoelectric filter device 1 preferably, in order to pass through the corresponding simulation of single piezoelectric filter 2
Mode and digital form, are constituted as follows.
Firstly, the first piezoelectric filter element 8 and the second piezoelectric filter element 9 of composition piezoelectric filter 2 are respective
Centre frequency mutually deviates.In this embodiment, the centre frequency of the first piezoelectric filter element 8 is filtered higher than the second piezoelectricity
The centre frequency of wave device element 9.Here, centre frequency is to be defined as the passband of downside and leading to for upside in the band-pass filter
The frequency of the arithmetic average of band.
It is used for the nominal of the piezoelectric filter device 1 of the present embodiment of the wireless set of outdoor as described above
Frequency is, for example, 50.85MHz.
In contrast, the centre frequency of the first piezoelectric filter element 8 deviates number kHz, example compared with the nominal frequency
Such as it is higher by 1kHz.In addition, the centre frequency of the second piezoelectric filter element 9 compared with the nominal frequency, deviates number kHz, example
Such as low 1kHz out.Therefore, in this embodiment, the centre frequency of the first piezoelectric filter element 8 and the second piezoelectric filter
The centre frequency of element 9 mutually deviates 2kHz.
The adjustment of the centre frequency of above-mentioned piezoelectric filter element 8,9 is for example by for each piezoelectric filter element 8,9
Each electrode 111~113,121~123 part vapor deposition etc. carry out.
Piezoelectric filter device 1 is under analog form and digital form, input of the switching for the signal of piezoelectric filter 2
Outbound course.Therefore, as shown in Figure 1, having above-mentioned first switching switch 3 and the second switching switch 4.
In turn, in piezoelectric filter device 1, the impedance of the impedance and outlet side that make the input side of piezoelectric filter 2 is not
Together.Therefore, piezoelectric filter device 1 has above-mentioned first impedance circuit 5 and the second impedance circuit 6.
First impedance circuit 5 is arranged between the input terminal 27 of the piezoelectric filter device 1 and the first switching switch 3,
Has first resistor R1 and first capacitor device C1.In addition, the output of the piezoelectric filter device 1 is arranged in the second impedance circuit 6
Between terminal 28 and the second switching switch 4, has second resistance R2 and the second capacitor C2.
In this embodiment, the impedance as the first impedance circuit 5 of input side is, for example, 360 Ω // 9pF, as defeated
The impedance of the second impedance circuit 6 of side is, for example, 160 Ω // 5pF out.
First switching switch 3, which has, to be connect with the first external connection terminals 21 of No. 1 terminal (#1) i.e. of piezoelectric filter 2
Travelling contact 3a and the first fixed contact 3b and the second fixed contact 3c.First fixed contact 3b and the first impedance circuit 5 connect
It connects, and is connect with the second fixed contact 4c of the second switching switch 4.The of the switching switch 4 of second fixed contact 3c and second
One fixed contact 4b connection.
Second switching switch 4, which has, to be connect with No. 4 terminal (#4) i.e. the 4th external connection terminals 24 of piezoelectric filter 2
Travelling contact 4a and the first fixed contact 4b and the second fixed contact 4c.First fixed contact 4b and the second impedance circuit 6 connect
It connects, and is connect as described above with the second fixed contact 3c of the first switching switch 3.
In this embodiment, in digital form, by the first switching switch 3 and the travelling contact of the second switching switch 4
3a, 4a are connected to the first side fixed contact 3b, 4b as shown in Figure 1.Accordingly, by the signal from input terminal 27 via the first resistance
Reactive circuit 5 is input to the first external connection terminals 21 of No. 1 terminal (#1) i.e. of piezoelectric filter 2, via the first piezoelectric filter
Element 8 and the second piezoelectric filter element 9, it is defeated from No. 4 terminal (#4) i.e. the 4th external connection terminals 24 of piezoelectric filter 2
Out, it is exported via the second impedance circuit 6 from output terminal 28.
In addition, in analog form, as shown in figure 5, by the first switching switch 3 and the travelling contact of the second switching switch 4
3a, 4a switching are connected to the second side fixed contact 3c, 4c.Accordingly, by the signal from input terminal 27 via the first impedance electricity
Road 5, first switches switch 3 and the second switching switch 4 is input to No. 4 terminal (#4) i.e. the 4th external connections of piezoelectric filter 2
Terminal 24, via the second piezoelectric filter element 9 and the first piezoelectric filter element 8, from No. 1 terminal (# of piezoelectric filter 2
1) i.e. the first external connection terminals 21 export, and export via the second impedance circuit 6 from output terminal 28.
In this way, by switching first switching switch 3 and second switching switch 3,4 come, and switching be directed to piezoelectric filter
The input and output direction of 2 signal, so that switching is directed to, centre frequency is mutually deviated and the first piezoelectricity of cascade connection filters
The input and output direction of the signal of device element 8 and the second piezoelectric filter element 8,9, in digital form, constriction signal leads to
Bandwidth widens the passband width of signal in analog form.Fig. 6 is the piezoelectric filter device 1 shown preferably
In, the figure of filter characteristic when having switched the input and output direction of signal, filtering when showing digital form with (a) of the figure
Device characteristic, filter characteristic when showing analog form with (b) of the figure.In Fig. 6, the longitudinal axis indicates the attenuation of signal
(dB), horizontal axis indicates the frequency (kHz) of signal.1 scale of the longitudinal axis is 1dB, and horizontal axis is (nominal with centre frequency 50.85MHz
Frequency) centered on ± 25kHz range, 1 scale is 2kHz.
In this embodiment, the passband width of signal when digital form is 10kHz/3dB, in contrast, simulation side
The passband width of signal when formula can be widened as 12.5kHz/3dB.
Then, to the input and output direction by switching for the signal of piezoelectric filter 2, to keep the passband of signal wide
Degree variation is illustrated.
Fig. 7 be for illustrate for piezoelectric filter 2 signal input and output direction be digital form when, i.e. by signal
It inputs from i.e. the first external connection terminals 21 of No. 1 terminal #1 of piezoelectric filter 2, connects outside No. 4 terminal #4 i.e. the 4th
The figure of filter characteristic when connecting terminal 24 exports.
Fig. 8 be for illustrate for piezoelectric filter 2 signal input and output direction be analog form when, i.e. by signal
It inputs from No. 4 i.e. the 4th external connection terminals 24 of terminal #4 of piezoelectric filter 2, connects outside No. 1 terminal #1 i.e. the firstth
The figure of filter characteristic when connecting terminal 21 exports.
In figures 7 and 8, (a) show the input side and outlet side of piezoelectric filter 2 impedance it is identical when the first piezoelectricity
The filter characteristic P2 of the filter characteristic P1 of filter element 8 and the second piezoelectric filter element 9.Such as (a) of the Fig. 7, Fig. 8
(a) shown in, the centre frequency of the centre frequency of the first piezoelectric filter element 8 and the second piezoelectric filter element 9 deviates frequency
Rate S deviates 2kHz in this embodiment as described above.
In this embodiment, as described above, the impedance of the input side of piezoelectric filter 2 is greater than the impedance of outlet side.
When the impedance of input side like this is greater than the impedance of outlet side, the filter of the piezoelectric filter element as input side
Wave device characteristic is deviated to the high side of frequency (positive side), and the filter characteristic of the piezoelectric filter element as outlet side is to frequency
Low side (negative side) offset.
Therefore, under digital form, as shown in (b) of Fig. 7, the filter of the first piezoelectric filter element 8 as input side
Wave device characteristic P1 is displaced to the high side of frequency, and the filter characteristic P2 of the second piezoelectric filter element 9 as outlet side is inclined
Move on to the low side of frequency, the deviation of the centre frequency of the first piezoelectric filter element 8 and the second piezoelectric filter element 9 increases
Greatly.
As a result, when the filter characteristic of the first piezoelectric filter element 8 of synthesis and the second piezoelectric filter element 9, such as
Shown in (c) of Fig. 7, the passband width of signal narrows, corresponding with digital form.
In contrast, under the analog form for inverting the input and output direction of signal, as shown in (b) of Fig. 8, as defeated
The filter characteristic P2 for entering the second piezoelectric filter element 9 of side is displaced to the high side of frequency, the first pressure as outlet side
The filter characteristic P1 of electrical filter element 8 is displaced to the low side of frequency, and the first piezoelectric filter element 8 and the second piezoelectricity are filtered
The deviation of the centre frequency of wave device element 9 reduces.
As a result, when the filter characteristic of the first piezoelectric filter element 8 of synthesis and the second piezoelectric filter element 9, such as
Shown in (c) of Fig. 8, the passband width of signal broadens, corresponding with analog form.
The offset of filter characteristic P1, P2 of first piezoelectric filter element 8 and the second piezoelectric filter element 9 can
It is adjusted by the difference of the impedance of the impedance and outlet side of the input side of piezoelectric filter 2.By increasing piezoelectric filter 2
Input side impedance and outlet side impedance difference, be capable of increasing offset.
In this embodiment, since the impedance of the input side of piezoelectric filter 2 is greater than the impedance of outlet side, conduct
The filter characteristic of the piezoelectric filter element of input side is deviated to the high side of frequency, the piezoelectric filter member as outlet side
The filter characteristic of part is deviated to the low side of frequency.
In contrast, contrary to the above when the impedance of the input side of piezoelectric filter 2 is less than the impedance of outlet side, make
Filter characteristic for the piezoelectric filter element of input side is deviated to the low side of frequency, the piezoelectric filter as outlet side
The filter characteristic of element is deviated to the high side of frequency.
Therefore, in this case, by signal from No. 1 i.e. the first external connection terminals of terminal #1 of piezoelectric filter 2
21 inputs become the identical filter with (c) of above-mentioned Fig. 8 when exporting from No. 4 i.e. the 4th external connection terminals 24 of terminal #4
Characteristic, the wide filter characteristic of passband width of signal i.e. corresponding with analog form.In addition, by signal from piezoelectric filter 2
No. 4 terminal #4 i.e. the 4th external connection terminals 24 input, from i.e. the first external connection terminals 21 of No. 1 terminal #1 export
When, become and filter that the passband width of (c) of above-mentioned Fig. 7 identical filter characteristic, signal i.e. corresponding with digital form is narrow
Wave device characteristic.
That is, compared with the above implementation, analog form and digital form phase reversal.
Fig. 9 is when having switched the input and output direction of signal in the piezoelectric filter device 1 shown preferably
The figure of the filter characteristic of wide area, (a) of the figure show filter characteristic when digital form, and (b) of the figure shows simulation side
Filter characteristic when formula.
As shown in figure 9, digital form is identical with the filter characteristic of analog form other than the passband of signal.
As described above, according to the present embodiment, by the input and output for switching the signal for single piezoelectric filter 2
Direction, so as to the width of the passband width of switching signal.Therefore, in the piezoelectric filter device 1 for having present embodiment
Commercial wireless devices in, can by the piezoelectric filter device 1 under analog form and digital form dual-purpose.
Accordingly, the pressure of the piezoelectric filter of the analog form different from the passband width of signal is needed and digital form
The commercial wireless devices of the conventional example of the two piezoelectric filters of electrical filter are compared, and the quantity of piezoelectric filter can be reduced,
Correspondingly, it can reduce cost, and can be realized and save space.
In addition, since the first piezoelectric filter element 8 and the second piezoelectric filter element 9 pass through in individual piezoelectric substrate
11, it 12 is respectively formed electrode 111~113,121~123 and constitutes, therefore is disconnected from each other on sound equipment, become spuious few high-quality
The element of amount.
In turn, since piezoelectric filter 4 is in addition to deviating the centre frequency of ambipolar piezoelectric filter element 8,9 mutually
In addition, there is basic structure same as the piezoelectric filter of existing four polar form, there is no need to substantially change existing quadrupole
The design of the piezoelectric filter of type can be implemented with cheap price.
It, can also be by being respectively formed electrode in single common piezoelectric substrate as other embodiments of the invention
111~113,121~123 constitute each piezoelectric filter element 8,9.
In the above-described embodiment, the area of the electrode 111~113 of the first piezoelectric filter element 8 and the second piezoelectricity are filtered
The area of the electrode 121~123 of wave device element 9 is identical, but as other embodiments of the invention, can also make an electricity
The area of the electrode of filter element is at most small by 40% or so compared with the area of the electrode of another electrical filter element.
For example, making the area of the electrode 111~113 of the first piezoelectric filter element 8 less than the second piezoelectric filter element 9
Electrode 121~123 area when, become the characteristic that fluctuation increases, be capable of the passband width of further constriction signal.
In addition, insertion loss increases, not preferably when the area of electrode being made to be reduced beyond described 40%.
In the above-described embodiment, suitable for signal corresponding with the analog form of commercial wireless devices and digital form
The switching of passband width, but the present invention is not limited to such uses, for example, can be applicable in multiple communication channels with
The switching of the passband width of the corresponding signal of channel with wide channel and narrow bandwidth.
In the above-described embodiment, use quartz base plate as piezoelectric substrate, it is also possible to use with piezoelectric property
Ceramic substrate or polycrystalline substrate.
Claims (8)
1. a kind of piezoelectric filter device has two piezoelectric filter elements cascading the piezoelectric filter being formed by connecting, institute
The interarea that two piezoelectric filter elements are stated in piezoelectric substrate is formed with input electrode and output electrode, in another interarea
It is opposed to be formed with common electrode with the input electrode and the output electrode, wherein
Described two respective centre frequencies of piezoelectric filter element mutually deviate,
The impedance of the input side of the piezoelectric filter and the impedance of outlet side are different,
By switching the input and output direction of the signal for the piezoelectric filter, carry out the width of the passband width of switching signal
It is narrow.
2. piezoelectric filter device according to claim 1, wherein
With two pieces of piezoelectric substrates,
The respective input electrode of described two piezoelectric filter elements, the output electrode and the common electrode are described
Two pieces of piezoelectric substrates are respectively formed.
3. piezoelectric filter device according to claim 1, wherein the piezoelectric filter device has:
Switch unit, by the way that the input terminal switching of the piezoelectric filter device is connected to the described defeated of the piezoelectric filter
Enter side or the outlet side, and the switching of the output terminal of the piezoelectric filter device is connected to the institute of the piezoelectric filter
Outlet side or the input side are stated, to switch the input and output direction of the signal.
4. piezoelectric filter device according to claim 3, wherein
Between the input terminal and the switch unit of the piezoelectric filter device and in the piezoelectric filter device
The output terminal and the switch unit between, be respectively arranged with make the input side impedance and the outlet side resistance
Resist mutually different impedance circuit.
5. piezoelectric filter device according to any one of claim 1 to 4, wherein
The piezoelectric substrate is quartz base plate.
6. piezoelectric filter device according to claim 1, wherein the piezoelectric filter device has:
First impedance circuit is connect with the signal input terminal of the piezoelectric filter device, and has defined impedance；
Second impedance circuit is connect with the signal output terminal of the piezoelectric filter device, and is had than the defined impedance
Low impedance；
First switching switch, connect with first impedance circuit, and when the piezoelectric filter device is digital form, by institute
The input side that the switching of the first impedance circuit is connected to the piezoelectric filter is stated, is analog form in the piezoelectric filter device
When, first impedance circuit switching is connected to the outlet side of the piezoelectric filter；And
Second switching switch, connect with second impedance circuit, and when the piezoelectric filter device is digital form, by institute
The outlet side that the switching of the second impedance circuit is connected to the piezoelectric filter is stated, is analog form in the piezoelectric filter device
When, first impedance circuit switching is connected to the input side of the piezoelectric filter,
It is switched by described two switchings, is the digital form or the analog form according to the piezoelectric filter device,
Switching is directed to the input and output direction of the signal of the piezoelectric filter, to switch the signal in the piezoelectric filter
The width of passband width.
7. piezoelectric filter device according to claim 6, wherein
The piezoelectric substrate is quartz base plate.
8. piezoelectric filter device according to claim 7, wherein
The quartz base plate is that AT cuts quartz plate.
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| JP2017243682A JP7043829B2 (en) | 2017-12-20 | 2017-12-20 | Piezoelectric filter device |
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| Publication number | Publication date |
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| JP7043829B2 (en) | 2022-03-30 |
| CN109951172B (en) | 2023-07-21 |
| JP2019110490A (en) | 2019-07-04 |
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