Piezoelectric array devices

Details Piezoelectric array devices Piezoelectric array devices

1998-09-03

2001-11-20

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S317000

Reexamination Certificate

active

06320300

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to piezoelectric devices and more particularly to piezoelectric resonators.
BACKGROUND OF THE INVENTION
Radio communication system components, such as transmitters and receivers, include a variety of filters, modulators, mixers, and oscillators for processing both digital and analog signals. Many of these devices have resonators made from discrete circuit components, such as capacitors, inductors, and resistors. The limitations of discrete circuit components in resonators are well known. They exhibit non-ideal, unstable or parasitic behavior. They are also heavy and bulky, impeding light-weight and cost effective designs in radio circuits.
The piezoelectric properties of crystalline structures are also well known. Applying an electric field to a piezoelectric crystal will distort the crystal lattice. Similarly, mechanically deforming a piezoelectric crystal produces an electric field. Piezoelectric crystals also resonate at various frequencies, and they are often used as resonators in radio circuits.
Despite the valued properties of piezoelectric crystals, their use in radio circuits has been substantially limited to oscillators and filters, where they are well suited for introducing frequency stability. Nevertheless, it is a disadvantage that the resonant frequencies of a piezoelectric crystal are fixed at the time of manufacture and that its properties may degrade over time. While the use of crystal resonators has provided performance benefits, it has not reduced the use. of discrete devices in radio circuits, and the potential benefits of piezoelectric properties remains largely untapped.
SUMMARY OF THE INVENTION
In this invention, piezoelectric crystals are arranged to function as variable resonators. In one embodiment, three piezoelectric crystals are arranged as an array, with a center crystal interposed between two outer crystals. The piezoelectric crystals are arranged such that an electrical excitation of the outer crystals causes a mechanical displacement in the outer crystals along an axis common to all three crystals. This displacement squeezes the center crystal, resulting in a shift of the center crystal's resonant frequency. By this arrangement, electric signals input to the outer crystals vary the resonant frequency of the center crystal.
A variable piezoelectric crystal resonator is well suited to radio circuits. In one embodiment, the piezoelectric device of this invention is a resonator in a typical oscillator circuit which then operates as a frequency modulator. A time varying input signal is coupled through a power divider to each of the two outer piezoelectric crystals. The input signal excites the outer crystals causing a mechanical displacement in the outer crystals according to the input signal. In turn, the outer crystals, which are held in mechanically responsive orientation with the center piezoelectric crystal, cause a mechanical displacement in the center crystal, varying its resonant frequency in accordance with the input signal. Because the oscillator's resonant frequency varies as a function of the input signal, application of a time varying input signal produces a frequency modulated signal at the oscillator output.
In another embodiment, the array forms a resonator for a tunable pre-select filter. Instead of a time varying input signal, a DC bias is placed across the outer piezoelectric crystals. The crystals change their dimension in accordance with the bias, thereby applying pressure to the center piezoelectric crystal. The pressure distorts the center crystal causing a shift in its resonant frequency. The center crystal is coupled as a resonator in a filter circuit, as is known in the art. Varying the bias voltage tunes the filter.
The arranged structure is not limited to three piezoelectric crystals. The frequency of the center piezoelectric crystal can be controlled by using multiple outer piezoelectric crystal devices. Each of the outer devices can be excited from DC to any frequency within the physical constraints of the crystals. A multiple crystal arrangement permits using some of the crystals to correct for small instabilities in the center frequency of the center crystal while using others for modulation.


REFERENCES:
patent: 2101272 (1937-12-01), Scott
patent: 2347098 (1944-04-01), Green
patent: 2551848 (1951-05-01), Parker
patent: 2636135 (1953-04-01), Peek, Jr.
patent: 2834943 (1958-05-01), Grisdale et al.
patent: 2945192 (1960-07-01), Szymanski
patent: 3570476 (1971-03-01), Gregg
patent: 4096756 (1978-06-01), Alphonse
patent: 5163436 (1992-11-01), Saitoh et al.
patent: 5217214 (1993-06-01), Takei
patent: 5410205 (1995-04-01), Gururaja
patent: 5825117 (1998-10-01), Ossmann et al.
patent: 6119804 (2000-09-01), Owen

Affiliated with

Also associated with

Rating

Piezoelectric array devices does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Piezoelectric array devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piezoelectric array devices will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2618283