JPH01114111A - Mechanical filter - Google Patents

Abstract

PURPOSE:To make an output signal stable and also to improve the S/N by providing an exciting means and a vibrator main body provided with the plural number of 1st vibrators and a 2nd vibrator coupling mechanically loops of the vibration of the 1st vibrators, etc. CONSTITUTION:An exciting means uses a magnet 13 to apply a DC magnetic field orthogonal to a vibrator main body 30 and uses an input transformer 41 to give an AC current through one of the 1st vibrators 31 and excites the main body 30 in a direction orthogonal to the magnetic field and the current through magnetic induction. Then the main body 30 is excited by an input signal given to the means 40 and the vibration of the main body 30 is detected by a vibration detection means 50 and extracted as an output signal. In this case, the main body 30 is divided into the 1st vibrator 31 for excitation and the 1st vibrator 31 for electromotive force detection and the 2nd vibrator 32 couples the lops of the vibrator of the vibrators 31. Since the title filter is isolated electrically but coupled mechanically, a high input component rejection ratio is obtained. Thus, an stable output signal with excellent S/N is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mechanical filter using Vita#R formed on a silicon substrate.

<Prior Art> FIGS. 5 to 7 are explanatory diagrams of the configuration of a conventional example that has been commonly used.

FIG. 5 is an explanatory diagram of the principle configuration, FIG. 6 is a sectional view taken along line A-A in FIG. Figure (B) shows a power supply for applying a reverse bias voltage between the p-type layer and the n+ type layer.

In these figures, 11 is a p-type silicon substrate having (100) impurity, for example, impurity II degree 101s atoms/Cm' or less.

On the surface of this substrate 11, "1+ diffusion V4 (omitted in the figure)" with traces of impurity m degree 1017 is partially formed, and this n
A vibrating beam 12 is formed in a part of the diffusion layer in the <001> direction. Note that this vibrating beam 12 is formed by processing the n10 layer and the 0 layer formed on the substrate 11 using photolithography and under-etching techniques.

13 is located approximately above the center of the vibrating beam 12 and is orthogonal to the vibrating beam 12;
Further, the magnet 14 provided in a non-contact state is a 3+02 film (see 6th fIAI) as an insulating film. 15
a and 15b are metal 'Fj electrodes such as AI, and one end of this metal electrode 15a is n'M+ extending from the beam 12.
It is connected through a contact hole 16a1 provided in the -8io2 layer, and the other end is connected to one end of a comparison resistor R0 and JelaM20, which has a resistance value substantially equal to the resistance value of the vibrating beam 12, via a lead wire. The output of the amplifier 20 is taken out as an output signal, branched off, and connected to one end of the primary coil L+. The other end of this coil L+ is connected to the common line.

On the other hand, the other end of the comparison resistor Ro is connected to the other end of the secondary coil L2 whose middle point is connected to the common line.
The other end of the vibrating beam 12 is connected to a metal electrode 15b formed in the same manner as described above.

In the above configuration, a reverse bias voltage is applied between the p-type m<substrate 10) and the n+-type layer (vibration beam 12) to insulate them, and an alternating current i is applied to the vibration #J beam 12 so that the current dimension and the vibration lR12 resonate. At the frequency, the impedance of the vibrating beam is upper bounded by electromagnetic induction, and an unbalanced signal of 1 g can be generated by the bridge formed by the comparison resistor Ro and L2 whose midpoint is connected to the common line. This signal is amplified by an amplifier 2o and taken out as an output signal.

In the above configuration, the impedance R of the vibrating beam 12 increases according to the natural frequency. This impedance R is
It can be expressed as the following formula.

R: (1/222) ・(1/ (E(JT)v2)
・(AB212/bh')-Q+R0 Here, E: Elastic modulus 9; Gravitational acceleration γ; Density A of the material making up the protein; Constant B determined by vibration [-de]; Magnetic flux density! ; Length of the vibrating beam b; Width h of the vibrating beam e; Thickness Q of the vibrating beam; Sharpness of resonance Ro; DC resistance value According to the above formula [! i! Since the Q of Ile takes a value of several hundreds to tens of thousands, a large amplitude signal can be obtained as the output of the amplifier in a resonant state.

Note that the processing means and shape of the vibrating beam are not limited to those in this embodiment; for example, B (boron) is applied to an n-type silicon substrate.
It is also possible to use a material formed by selective etching with an enlargement of 4×10'' atoms/cm 3 or more.

<Problems to be Solved by the Invention> However, in such a device, the back electromotive force generated in the vibrating beam 12 is detected using an AC bridge, but the components of the input signal cannot be completely detected by the AC bridge. Since it is virtually impossible to suppress the input component, a portion of the input component is transferred to the bridge output.

For this reason, the S/N ratio is poor and stable output Bg cannot be obtained.

The present invention solves this problem.

An object of the present invention is to provide a mechanical filter that can provide a stable output signal with a good S/N ratio.

<Means for Solving the Problems> In order to achieve this object, the present invention provides a vibrator body made of silicon, which is provided on a silicon substrate, and an excitation means for exciting the vibrator body. and a detection means for detecting excited vibrations of the vibrator body, the mechanical filter comprising: two first vibrators having both ends fixed to the substrate and arranged parallel to each other; and the first vibrator. a vibrator body comprising a second vibrator that mechanically couples the antinodes of vibration to each other, and a DC magnetic field orthogonal to the vibrator body is applied to both ends of one of the first vibrators or the two vibrators. an excitation means for passing an alternating current through one end of the first vibrator to excite the first vibrator in a direction perpendicular to the magnetic field and the current by magnetic induction; The mechanical filter includes vibration detection means for detecting the electromotive force generated at the other end of each of the first vibrators.

<Operation> In the above configuration, the vibrator main body is excited by the input signal input to the excitation means. The vibration of the vibrator body is detected by the vibration detection means and taken out as an output signal.

Hereinafter, a detailed explanation will be given with reference to S in the examples.

<Embodiment> FIG. 1 is an explanatory diagram of the basic configuration of one embodiment of the present invention.

In the figure, structures with the same symbols as in FIG. 5 represent the same functions.

Hereinafter, only FIG. 5 and the phase 3i portion will be explained.

30 is a vibrator main body. The vibrator main body 30 has two first vibrators 31 that are fixed to the substrate 11 at both ends and are arranged parallel to each other, and a second vibrator that mechanically couples the vibration crotches of the first vibrators 31 to each other. Add 32 to K1.

Reference numeral 40 applies a DC magnetic field orthogonal to the vibrator body 30 using the magnet 13, and inputs an AC fti current to both ends of one first vibrator 31. A quadrature lance 41 applies a DC magnetic field orthogonal to the vibrator body 30. This is an excitation means that excites in a direction perpendicular to the direction.

The input transformer 41 has its primary side connected to the input terminal 42 . The secondary side is the first one! It is continuous with both 0iil of io child 31.

Reference numeral 50 denotes a vibration detection stage that detects the electromotive force generated at both ends of the other first vibrator 31. In this case, an output transformer 51 is used. The primary side of the output lance 51 is connected to both ends of the other first vibrator 31, and the secondary side is connected to the output terminal 53 via the amplification Fi52.

In the above configuration, the vibrator main body 30 is excited by the input signal input to the excitation means 40.

The vibration of the vibrator body 30 is detected by the vibration detection means 50 and taken out as an output signal.

As a result, the vibrator main body 30 has the first vibrator 31 for excitation.
and a first oscillator 31 for electromotive force detection, and the second oscillator 32 couples the antinode of the vibration of the first oscillator 31, so they are electrically separated. However, since they are mechanically coupled, the input component rejection ratio (S
N ratio) is obtained.

FIG. 2 shows an actual example of the vibrator main body 30, and (A) is a plan view;
([3) is a BB sectional view of (A).

Figure 3 shows the experimental setup.

An input component rejection ratio (S/N ratio) of 30 to 40 dB was obtained.

In the vertical direction of FIG. 3, the peak value is 5 dB, and the center frequency of the peak value is 71551.1 Hz.

FIG. 4 shows another embodiment 2 of the present invention! It is an explanatory diagram of the county structure.

In this embodiment, the secondary side of the input transducer 41 is connected to the same end side of one of the two first oscillators 31, and the output transducer 5
The primary side of the first vibrator 1 is connected to the other same end side of the two first vibrators 31.

In addition, in the above-mentioned embodiment, the second *+h child 32 is P
Although it has been explained that it is made of silicon, it is not limited to this. For example, a conductor such as aluminum is applied to silicon oxide (SiO2) or silicon nitride (SiN'4).
It may also be a MH type.

<Effects of the Invention> As explained above, the present invention provides a vibrator body made of silicon provided on a silicon U plate, an excitation means for exciting the vibrator body, and an excitation device for the vibrator body. In the mechanical filter, the mechanical filter includes two first vibrators whose ends are fixed to the substrate and are arranged parallel to each other; and a second vibrator that is mechanically coupled to the!
& Apply a DC magnetic field orthogonal to the main body of the mover and the pre-main body, and cross it to both ends of one of the first vibrators or to the same end of one of the two first vibrators! 1! Excitation means for applying current to excite the vibrator in a direction perpendicular to the magnetic field and the current by magnetic GR conduction; A mechanical filter is constructed which includes vibration detection means for detecting the generated electromotive force.

As a result, the transducer body is divided into the first transducer for excitation and the first transducer for electromotive force detection, and the second transducer combines the imaging antinode part of the first transducer. Since they are electrically separated but mechanically coupled, a high input component rejection ratio (S/N ratio) can be obtained.

Therefore, according to the present invention, it is possible to realize a mechanical filter that has a good S/N ratio and can provide a stable output signal.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the RF4 rational 2!811@ construction of an embodiment of the present invention, and Fig. 2 is an explanatory diagram of the main part configuration of Fig. 1, where <A) is a plan view, and (B) is a ) B-8 sectional view, Figure 3 is the 1st
FIG. 4 is an explanatory diagram of the main part configuration of another embodiment of the present invention. FIGS. 5 to 7 are explanatory diagrams of the configuration of a conventional example commonly used. 6 is a Δ-Afli plane view of FIG. 5, and FIG. 7 is a diagram showing FIG. 5 as an electric circuit. DESCRIPTION OF SYMBOLS 11... Substrate, 13... Magnet, 30... Vibrator main body, 31... First vibrator, 32... Second vibrator, 4
0... Excitation means, 41... Input cadence, 42...
- Input terminal, 50... Vibration detection means, 51... Output transformer, 52... Amplifier, 53... Output terminal. Figure 1 Figure 2 (A) Figure 5 Figure 6

Claims (1)

[Scope of Claims] A vibrator body made of silicon provided on a silicon substrate, excitation means for exciting the vibrator body, and detection means for detecting the excited vibrations of the vibrator body. In the mechanical filter, two first vibrators having both ends fixed to the substrate and arranged parallel to each other, and a second vibrator mechanically coupling antinodes of vibration of the first vibrators to each other. a vibrator body comprising;
A direct current magnetic field orthogonal to the vibrator body is applied, and an alternating current is passed through both ends of one of the first vibrators or the same end of one of the two first vibrators, and the vibrator is exposed to the magnetic field by magnetic induction. It is equipped with an excitation means that excites in a direction perpendicular to the current, and a vibration detection means that detects an electromotive force generated at both ends of the other first vibrator or at the other same end side of the two first vibrators. Mechanical filter.