CN103546117B - Two-dimensional piezoelectric photonic crystal radio frequency acoustic wave guide - Google Patents

Abstract

The invention relates to a two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide, the two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide includes a two-dimensional metal lattice arranged on a piezoelectric substrate, the y of the two-dimensional metal lattice is The directional lattice constant is proportional to the x-direction lattice constant such that the passband in the x-direction corresponds to the stopband in the y-direction. The lattice constant in the y direction of the two-dimensional metal lattice is proportional to the lattice constant in the x direction, specifically, the lattice constant in the y direction is 1.5 to 4.5 times the lattice constant in the x direction. The invention can enable the surface acoustic wave in the radio frequency section to efficiently propagate in the x direction in the piezoelectric phononic crystal, and realize effective energy reflection in the y direction, thereby realizing the acoustic waveguide function of the radio frequency section.

Description

A two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide

technical field

The invention relates to the field of piezoelectric devices, in particular to a two-dimensional piezoelectric phonon crystal radio frequency acoustic waveguide.

Background technique

At present, conventional two-dimensional symmetric phononic crystals, that is, the lattice constants in the x-direction and the y-direction are equal, can be used to improve the performance of the resonator, as shown in Figure 1. Since the band gap distribution in the x direction and the y direction obtained by the two-dimensional symmetric phononic crystal is consistent, the sound wave in the band gap realizes total energy reflection in the x direction and the y direction. Therefore, the phononic crystal structure acts as a reflective grid to prevent energy leakage and obtain high-Q resonator performance.

In the existing patent CN200410077471.9 utility model patent "two-dimensional phononic crystal sound insulation structure" and CN200420102759.2 utility model patent "two-dimensional phononic crystal sound insulation structure", CN200910061996.6 utility model patent "a vehicle periodic Damping structure and its vibration and noise reduction method", CN201020198828.X utility model patent "compound three-dimensional phononic crystal automobile exhaust muffler" all involve the application of conventional phononic crystals, using the bandgap characteristics of sound waves propagating in periodic media to For the purpose of sound insulation, noise reduction or noise reduction, these technologies use non-piezoelectric materials, so they are only used in the low frequency field and cannot realize the function of acoustic waveguide.

With the development and maturity of micro-nano-scale processing technology, the application of phononic crystals is no longer limited to the low-frequency band of the macro-scale, but can also be applied to the MHz/GHz radio frequency band. The 2010 IEEE.UFFC:pp.30-37 article "A SAWresonator with two-dimensional reflectors" mentioned a new type of two-dimensional reflective structure surface acoustic wave resonator. The two-dimensional metal lattice in the structure only confines the surface acoustic wave energy in the resonator, improves the resonant Q value of the resonator, and thus improves the performance of the resonator. The surface acoustic wave resonator can be applied to the radio frequency section, but it only uses the dot matrix to complete the limiting function of the surface acoustic wave energy in the x direction and the y direction to realize the performance of the resonator, but cannot realize the function of the acoustic waveguide.

Contents of the invention

The purpose of the present invention is to provide a two-dimensional piezoelectric phononic crystal radio-frequency acoustic waveguide capable of realizing the function of the radio-frequency acoustic waveguide.

In order to achieve the above object, the present invention provides a two-dimensional piezoelectric phononic crystal radio-frequency acoustic waveguide, which is characterized in that it includes a two-dimensional metal lattice arranged on a piezoelectric substrate, and the y direction of the two-dimensional metal lattice is The lattice constant is proportional to the x-direction lattice constant such that the passband in the x-direction corresponds to the stopband in the y-direction.

Further, the lattice constant in the y direction of the two-dimensional metal lattice is proportional to the lattice constant in the x direction, specifically, the lattice constant in the y direction is 1.5 to 4.5 times the lattice constant in the x direction.

Further, the two-dimensional metal lattice adopts metal materials such as aluminum, copper, tungsten, or gold.

Further, the cross-sectional shape of the two-dimensional metal lattice is a circle, a square, an ellipse, or a rectangle.

The invention can enable the surface acoustic wave in the radio frequency section to efficiently propagate in the x direction in the phononic crystal, and realize effective reflection of energy in the y direction, thereby realizing the acoustic waveguide function in the radio frequency section.

Description of drawings

Figure 1 is a schematic structural diagram of a conventional two-dimensional symmetric phononic crystal resonator;

2 is a schematic structural diagram of a two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide according to an embodiment of the present invention;

Figure 3 is a frequency response diagram of a two-dimensional symmetrical aluminum lattice with 36 ⁰ YX lithium tantalate as a piezoelectric substrate;

Fig. 4 is that Y-Z lithium niobate is the two-dimensional symmetrical aluminum lattice frequency response figure of piezoelectric substrate;

Figure 5 is the frequency response diagram of the two-dimensional symmetrical aluminum lattice with 128 ⁰ YX lithium niobate as the piezoelectric substrate

Figure 6 is the frequency response diagram of the two-dimensional symmetrical aluminum lattice of ST-X quartz as the piezoelectric substrate

Fig. 7 is a frequency response diagram of two-dimensional acoustic wave modulation aluminum lattice with 128 ⁰ YX lithium niobate as piezoelectric substrate according to an embodiment of the present invention.

detailed description

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 2 , it is a schematic diagram of the structure of a two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide according to an embodiment of the present invention.

The two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide includes a two-dimensional metal lattice 1 and a piezoelectric substrate 2 . The two-dimensional metal lattice 1 is arranged on the piezoelectric substrate 2 in the form that the lattice constant in the y direction is 1.5 to 4.5 times the lattice constant in the x direction. Among them, the two-dimensional metal lattice can be made of metal materials such as aluminum, copper, tungsten or gold, and its cross-sectional shape is circular, square, elliptical or rectangular.

The pass-band frequency f _{x, p} and the stop-band frequency f _{x, s} of the x-direction of the two-dimensional metal lattice 1 are calculated by formulas (1) and (2),

f _x,p = V _p /a (1)

f _x,s = V _s /a (2)

a is the lattice constant in the x direction of the two-dimensional metal lattice 1, V _p and V _s are the acoustic wave mode velocities corresponding to different passbands and stopbands in the two-dimensional metal lattice 1, and usually have multiple values.

Similarly, the pass-band frequency f _y,p and stop-band frequency f _y,s of the y-direction of the two-dimensional metal lattice 1 are calculated by formulas (3) and (4),

f _y,p =V _p /b (3)

f _y,s = V _s /b (4)

b is the y-direction lattice constant of the two-dimensional metal lattice 1 .

If the lattice constant a in the x direction is equal to the lattice constant b in the y direction, that is, a two-dimensional symmetric metal lattice, the stopband frequency in the y direction corresponds to the stopband frequency in the x direction, that is, f _y,s = V _s /b=V _s /a=f _x,s , so the surface acoustic wave energy is reflected in the x direction and the y direction at the same time, and the acoustic waveguide function cannot be realized.

In order to realize the acoustic waveguide function, it is necessary to change the lattice constants a and b, so that the stop band frequency in the y direction corresponds to the pass band in the x direction. Assuming that a is unchanged and b is changed, the stopband frequency and passband frequency in the x direction will not change, but the stopband frequency and passband frequency in the y direction will change. Adjust b so that the stopband frequency f' _y,s in the y direction corresponds to the passband f _x,p in the x direction, so f _x,p =f' _y,s =V _s /b. From this, formula (5) can be obtained. From formula (5), it can be seen that the ratio of the stop band frequency in the y direction and the pass band frequency in the x direction of the two-dimensional symmetric metal lattice is equal to the lattice constant ratio in the y direction and the x direction.

f _y,s /f _x,p = (V _s /a)/(V _s /b)=b/a (5)

Therefore, adjusting the lattice constant ratio of the two-dimensional metal lattice 1 in the x direction and the y direction according to the ratio of the passband frequency in the x direction and the stopband frequency in the y direction of the two-dimensional symmetrical metal lattice can realize the surface acoustic wave in the piezoelectric phononic crystal. The inner x direction passes through efficiently, and the energy is effectively reflected in the y direction, thereby realizing the function of the acoustic waveguide.

However, the two-dimensional symmetrical metal lattice 1 on the piezoelectric substrate 2 of different materials has different ratios of the passband frequency in the x direction and the stopband frequency in the y direction, so the adjusted ratio of the lattice constant in the x direction to the lattice constant in the y direction is It is also different.

In this embodiment, the piezoelectric substrate 2 is made of lithium tantalate, lithium niobate, and quartz, and the two-dimensional metal lattice 1 is made of metal aluminum. The thickness of the two-dimensional aluminum lattice is in the range of 0.5%λ to 10%λ, where λ is the wavelength of the surface acoustic wave. Within this range, the frequency response distribution of the two-dimensional lattice remains basically unchanged.

Specifically, when the piezoelectric substrate 2 is made of 36 ⁰ YX lithium tantalate, as shown in FIG. 3 , it is a frequency response diagram of a two-dimensional symmetrical aluminum lattice with 36 ⁰ YX lithium tantalate as the piezoelectric substrate. It can be seen that the passband frequency f _x,p with small ripples and high relative amplitude in the x direction is distributed around 0.2, and the stopband frequency value f _y,s in the y direction is distributed between 0.3~0.36, 0.41, 0.65, 0.75, 0.85, It is around 0.9, so the adjusted lattice constant ratio b/a value ranges from 1.5 to 4.5 according to the ratio of the passband frequency in the x direction and the stopband frequency in the y direction.

When the piezoelectric substrate 2 adopts YZ lithium niobate, as shown in FIG. 4 , it is a two-dimensional symmetrical aluminum lattice frequency response diagram of YZ lithium niobate as the piezoelectric substrate. It can be seen from this that the passband frequency f _{x, p} with small ripples and high relative amplitude in the x direction is distributed around 0.22, and the stopband frequency value f _{y, s} in the y direction is distributed around 0.41 ~ 0.48, 0.58, so according to the x direction The adjusted lattice constant ratio b/a ranges from 1.9 to 2.6 after the passband frequency and the y-direction stopband frequency ratio are adjusted.

When the piezoelectric substrate 2 uses 128 ⁰ YX lithium niobate, as shown in FIG. 5 , it is a two-dimensional symmetrical aluminum lattice frequency response diagram of 128 ⁰ YX lithium niobate as the piezoelectric substrate. It can be seen from this that the passband frequency f _x,p with small ripples and high relative amplitude in the x direction is distributed around 0.22, and the stopband frequency value f _y,s in the y direction is distributed between 0.38~0.45, 0.5, 0.55, 0.71, Around 0.84 and 0.9, so the adjusted lattice constant ratio b/a value ranges from 1.7 to 4.1 according to the ratio of the passband frequency in the x direction and the stopband frequency in the y direction.

When the piezoelectric substrate 2 adopts ST-X quartz, as shown in FIG. 6 , it is a two-dimensional symmetric aluminum lattice frequency response diagram of ST-X quartz as the piezoelectric substrate. It can be seen from this that the passband frequency f _{x, p} with small ripples in the x direction and high amplitude is distributed around 0.2, and the stopband frequency f _{y, s} in the y direction is distributed around 0.31, 0.39, 0.5, 0.55, so according to The adjusted lattice constant ratio b/a ranges from 1.6 to 2.6 for the passband frequency in the x direction and the stopband frequency in the y direction.

By adjusting the ratio of the above lattice constants, it can be concluded that the lattice constant in the y direction of the two-dimensional metal lattice 1 on the piezoelectric substrate 2 is 1.5 to 4.5 times the lattice constant in the x direction.

By changing the lattice constant ratio of the two-dimensional metal lattice in the x direction and the y direction on the piezoelectric substrate, the pass band in the x direction corresponds to the stop band in the y direction, so that the surface acoustic wave in the x direction in the two-dimensional piezoelectric phononic crystal Efficiently pass through, and realize effective reflection of energy in the y direction, and finally make the energy propagate in the x direction, thereby realizing the function of the radio frequency acoustic waveguide.

As shown in Fig. 7, it is the frequency response diagram of the two-dimensional acoustic wave modulation aluminum lattice with 128 ⁰ YX lithium niobate as the piezoelectric substrate. The piezoelectric substrate of the two-dimensional piezoelectric phononic crystal radio frequency acoustic waveguide in this embodiment adopts 128 ⁰ YX lithium niobate, the metal lattice adopts aluminum material, the period of the lattice in the x direction is 10 microns, and the real period of the dots in the y direction is 18.6 microns, that is, the lattice constant in the y direction is 1.86 times that in the x direction, and the radius of the columnar metal aluminum lattice is 7 microns. It can be seen from Figure 7 that the frequency 0.21-0.25 is the pass-band frequency for the x direction, and the stop-band frequency for the y direction. Therefore, when the surface acoustic wave frequency is 0.21-0.25, the two-dimensional piezoelectric phononic crystal can realize the surface acoustic wave Waves reflect energy efficiently in the y-direction and propagate efficiently in the x-direction.

The substrate of the two-dimensional piezoelectric phononic crystal radio-frequency acoustic waveguide provided by the present invention adopts piezoelectric materials, and by adjusting the lattice constant ratio of the two-dimensional metal lattice on the piezoelectric substrate in the x direction and the y direction, the The surface acoustic wave propagates in the x direction in the phononic crystal, and realizes energy reflection in the y direction, thereby realizing the function of the acoustic waveguide in the radio frequency segment.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (3)

1. a kind of two-dimensional piezoelectric photonic crystal radio frequency acoustic wave guide, it is characterised in that including the two-dimensional gold being arranged on piezoelectric substrate Category dot matrix, the y directions lattice paprmeter of the two-dimensional metallic dot matrix is proportional to x directions lattice paprmeter so that the passband on x directions Corresponding to the stopband on y directions；

The y directions lattice paprmeter of the two-dimensional metallic dot matrix specially y directions lattice proportional to x directions lattice paprmeter is normal Number is 1.5～4.5 times of x directions lattice paprmeter.

2. two-dimensional piezoelectric photonic crystal radio frequency acoustic wave guide according to claim 1, it is characterised in that the two-dimensional metallic point Battle array adopts metallic material of aluminum, copper, tungsten or gold.

3. two-dimensional piezoelectric photonic crystal radio frequency acoustic wave guide according to claim 1, it is characterised in that the two-dimensional metallic point The shape of cross section of battle array is circular, square, oval or rectangle.