Third order intermodulation and thermal effects in electro-acoustic devices for communications
Tutor / director / evaluatorCollado Gómez, Juan Carlos
Document typeMaster thesis
Rights accessRestricted access - confidentiality agreement
Mobile devices have evolved very quickly over the years. The tendency is to cover all the wireless applications in a same device, in order to provide the best user experience. The use of microwave resonators is very present in a large number of devices such filters, oscillators and tuned amplifiers. In this type of resonators, the size of the devices is usually directly related to the wavelength of the electromagnetic wave at a certain work frequency. Actually, the use of microwave resonators is not suitable for these devices. Device size at RF and microwave frequencies is a limitation in terms of integration due to their greater size with respect to other integrated components. With the use of acoustic resonators, the size of the devices can be reduced considerably. This type of resonators reduces the phase velocity around 5 five orders of magnitude lower than the electromagnetic wave velocity, due to wave propagation in an acoustic medium. This implies that the wavelength is 5 five orders of magnitude lower, and consequently, the size of the resonator. There are two common techniques in order to implement electro-acoustic resonators: Bulk Acoustic Wave Resonators (BAW) and Surface Acoustic Wave Resonators (SAW). This work focus on BAW resonators. Also, one of the biggest problems in current communication services is the co-existence of different services. High power transmitted signals and out-of-band transmissions can be a source of interferences for a given communication service, and consequently, can provoke losing QoS or even making impossible the signal demodulation. The jamming signals can be mixed with the high power transmitter signal of a transceiver in the antenna or in the first filtering device (duplexer or multiplexer) and provoke harmonics and/or intermodulation products that may fall at the frequency of the receiver channel. That will happen if those passive devices are even slightly nonlinear and will cause desensitization of the receiver. This effect is known as PIM ("passive intermodulation") and is stronger for electro-acoustic devices since they are quite nonlinear. This master thesis is focused in the study of the nonlinear problem in BAW resonators through the design of new measurement systems, in order to measure, characterize and model the nonlinear behaviour of BAW resonators and identify the origin of the nonlinearities.