Frequency-adjustable surface acoustic wave device
In telecommunications, a large number of Radio Frequency (RF) bands are used to transmit or receive information. Each band defines a channel for which filtering functions are necessary to restore the information.
Passive surface acoustic wave (SAW) passive frequency filters play a crucial role in radio frequency telecommunication systems. However, these devices do not allow a voltage-controlled adjustment of their working frequency or bandwidth.
The proposed solution is to modify the electrical conditions within the SAW devices in order to vary their operating frequency, i.e. to make SAW filters frequency agile while preserving the integrity of the filtering function. The modification and control of the operating frequencies of the devices is performed by an external electrical control.
Frequency agility allows to consider only one device to investigate several frequency bands for the same filtering functionality.
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Schematic diagram: resonator (in red the transducer, in blue the mirrors). The electrodes of the mirrors are classically connected to ground. Here, we propose a connection of the electrodes of the mirrors or to the ground or in open circuit.
Result on a resonator with change of connections: all DC (all short circuit = all to ground), then 10 electrodes in CO (open circuit), then 30 in CO then 50 in CO then all in CO: we see the shift of the resonator operating frequency.
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