Electricity: circuit makers and breakers – Electrostrictive or electrostatic
Reexamination Certificate
1999-03-08
2001-01-09
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Electrostrictive or electrostatic
C310S311000, C310S323020
Reexamination Certificate
active
06172316
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an antenna-switching device between the output of a transmitting stage and the input of a receiving stage. The invention may particularly be used in mobile telephones.
BACKGROUND OF THE INVENTION
In a system such as a time-division multiple access TDMA cellular radiotelephone, the antenna is alternately to be used at the output of the transmitting circuit or at the input of the receiving circuit. It is thus necessary to isolate these two circuits from each other. Indeed, if the transmitting circuit is not correctly isolated, a significant part of the transmitting power flows into the receiving circuit which is not used at that moment; furthermore, a part of the transmitting power is sent back to its source without even having reached the antenna. Similarly, on the receiving end, a poor isolation relative to the transmitting circuit would lead to losses owing to dissipation or mismatches.
Currently, electrostatic relays such as described, for example, in the document U.S. Pat. No. 5,578,976, are not fast enough and this type of antenna switching device can only be realized for obtaining the desired useful life and rapidity by means of semiconductors such as a PIN diode. But, with such an element, the losses are at least 1 dB because of the series resistance and the current limit imposed thereon (of the order of 1 mA). On the other hand, the compression point of such a switching device is not very high and it thus has a poor linearity.
SUMMARY OF THE INVENTION
It is thus an object of the invention to propose an antenna-switching device remedying the drawbacks described above.
For this purpose, the invention relates to a device that includes a piezoelectric actuator formed by two fixed plates forming a capacitor and by a movable contact of a piezoelectric material. The inside surfaces of the plates are locally metallized so as to form electrical contacts. Further, electrodes are provided so as to supply the movable contact with a control voltage capable of deforming the contact. The deformation occurs between a rest position corresponding to a given part of the plates, and a working position corresponding to another given part of the plates.
The device thus proposed ensures an impedance-controlled high-frequency switching lasting less than 1 ms with very little losses, while the power is kept adapted to the output level of the transmitting circuit, even permitting to support the absence of connection of the antenna for a short while in the case of poor handling by the user. Besides, preserving the characteristic impedance, limits the value of the losses as a result of mismatch and contributes to keeping the power consumption of the device low whose limited weight and mechanical size are also assets.
According to two possible variants of embodiment, the respective lower parts of the inside surfaces form the contacts corresponding to the rest position, and their upper parts form the contacts corresponding to the working position, said movable contact being displaceable in parallel with the inside surfaces of the plates. Alternatively, the plates are formed by a combination of projecting parts, the movable contact being displaceable in transverse direction to the plates between the projecting parts of a plate that correspond to the rest position, and the projecting parts of the other plate that correspond to the working position. According to a third variant of embodiment, the actuator is a piezoelectric motor including. The motor also includes a part that can be deformed by a piezoelectric or a magnetorestrictive effect and a fixed support and, on the other hand, a movable part forming the movable contact. The piezoelectric effect and the mechanical friction between the deformable part and its fixed support and the part forming the movable contact, is provided for provoking alternating deformations of the deformable part along two transversal axes.
REFERENCES:
patent: 3688135 (1972-08-01), Koda et al.
patent: 4811246 (1989-03-01), Fitzgerald, Jr. et al.
patent: 4916349 (1990-04-01), Kornrumpf
patent: 5578976 (1996-11-01), Yao
patent: 5883519 (1999-03-01), Kennedy
patent: 948019 A1 (1999-10-01), None
Halajian Dicran
Scott J. R.
U.S. Philips Corporation
LandOfFree
Antenna switching device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antenna switching device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna switching device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501894