peizeo effects

I think it's the physical dimesinion that govern the resonant frequency and the orientation of the cut with respect to the crystal structure.

A crystal can be pulled a little way either side of it's resonant frequency, and it may be possible to get resonance at other frequencies (overtones?)

Mr Google should be able to help

Del

Think Del's onto it - it's got a lot to do with the physical dimensions. 100mm sound huge if you're talking MHz. Just my two-penny'th.

Hello terry moloney

I wouldn't think it likely you could achieve such a large frequency range using a SiO₂ wafer.

Piezo crystals have 3 axes, X, Y, Z at right angles to each other.

With a wafer, you have very limited thickness, thus perhaps quite limited range of adjustment.

If you did manage to achieve such a large frequency range, the piezo crystal would not be very efficient at either end of the range.

I'm wondering where you would use such a 100mm wafer, with such a large frequency range, should it be possible.

Advise further, with

Kind Regards....

Everything has already been said, so I won't repeat. Just one more remark,

By increasing the current through the substrate,you will only increase it's mechanical vibrations to produce more or less out-put, but Will not change it's resonating frequency. It can be tweaked a bit though but just few cycles up or down, and even that is not always the case and it depends on the electrical circuit in which it operates.

Wangito.

To learn more, Search Frequency Synthesizers.

Wangito

Hi,

you have a lot of different resonance possibility in a wafer, as in any plate.

1.Bending modes (plate in 2-dimensional bending), these are likely to be in the 10 Hz to 10 KHz region according to mode structure (radial and circumferential modes can be excited, so there are countless frequencies f_r,c with r,c any positive integer. The very high ones are damped too high to be easily excited.

2. Shear modes: shearing in planes perpendicular to the wafer surface, these are very likely in the 10 to 100 KHz region, these too have higher modes (and any direction). Shear modes are also existing in shearing directions in the wafer plane, these are likely to exist in the 100KHz to 10MHz in the fundamental mode and up to above 100MHz in the overtones.

3. Compression-expansion modes: any direction that can be compressed, mostly in plane then low frequency (factor of 1.7 higher than shear modes)

4. surface wave modes: (see SAW-devices) fundamental and higher harmonics,
surface waves exist by coupling elastic energy of a vibrating surface to kinetic energy of the moving mass - as in the cases 1. to 3. but not he entire bulk material is oscillating but only down to a limited depth.
Also in SAWs there are shear and compression type-waves.

5. Some more that I do not really know called Rayleigh waves and Lamb waves????

None of these is tunable by excitation. Silica is a very good and linear and stable elastic material with almost no nonlinearity. Any of these dependent on the direction of the quartz crystallographic axis orientations with respect to the wafer.

Only nonlinear (elastic modulus by strain) materials can be tuned in frequency by changing the level of amplitude.

What do you want to do by exciting a complete wafer? Or may be you have cut the wafer to pieces? If so you can use any of the modes described above and the respective higher harmonics. This will cover your frequency range by discrete frequencies. Oscillations above the 20tieth are difficult to excite and to separate from the next.

Search for a book on quartz crystal oscillators.

There was an early one from Texas Instruments.

It is very likely that your goals will be solvable by easier methods.

RHABE

Whilst a 3 MHz crystal could be pulled to 100 MHz, if what you are after is a crystal locked 100 MHz oscillator, this can be done by taking the crystal locked 3MHz signal, making a square wave of it (overdrive a CMOS gate, then take of second harmonic using a filter, make a square wave of it, etc etc. 5 frequency doubling stages get you to 96 MHz. Maybe you can pull the crystal 4% and get to 100MHz

A similar thing is done to 2.8GHz for a linear accelerator RF driver. They used to use a VHF triode and a couple of doubling/trebling stages, but nowadays they do it in a similar way with solid state.