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Authors:Pär Rundqvist: Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden
Andrei Vorobiev: Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden
Spartak Gevorgian: Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden \ Microwave and High Speed Electronics Research Center, Ericsson AB, Sweden
Publication title:Microwave power dependent properties of ferroelectric varactors
Conference:GigaHertz 2003. Proceedings from the Seventh Symposium
Publication type: Poster
Article No.:068
Abstract:Ferroelectrics; especially in paraelectric phase; are widely considered for microwave applications. The main feature; that’s makes them attractive for tuneable microwave applications; is the DC field non-linear dependent dielectric permittivity. A large number of tuneable microwave devices and systems have been demonstrated in the past; In general; the microwave power dependence of film parameters is an undesirable effect; however when properly designed; ferroelectric components may be used in harmonic generators and mixers. In this work we report preliminary results of nonlinearity measurements of parallel-plate ferroelectric varactors integrated on Si wafers.

The first reports on experimental investigation of nonlinearities in BaxSr1-xTiO3 based ceramics date back to 1950s and early 1960s. DiDomenico et al report the first successful demonstration of a 3rd harmonic generator in 1962. Recently 2nd harmonic generation was demonstrated [4]; by applying DC bias. Samoilova et al. reported frequency conversion (harmonic generation) experiment in a Coplanar Waveguide (CPW) with a ferroelectric film. Where as Booth et al [6] uses a CPW with Ba0.3Sr0.7TiO3 film; the non-linear capacitance C by using two approaches: i) third harmonic generation; and ii) C(VDC) measurements at microwave frequencies. It was shown that the non-linear capacitance C determined from C(VDC) measurements is in excellent agreement with the one found from third harmonic generation experiment; this leads to the conclusion that ferroelectric devices might be tuned with nanosecond speeds.

To study nonlinearities Kozyrev et al designed a resonator loaded by a ferroelectric capacitor; using both a single signal as well as intermediation distortion; which confirmed previous results. Kozyrev et al also gives a simple theory for estimation of overheating of the ferroelectrics films at high power levels; and it was shown that the power handling capability of a ferroelectric tuneable filter may be as high as 3.5 W. Experiments and more detailed analysis of the microwave heating on nonlinearities are given elsewhere.

In this work; we used simple; on-chip microprobe reflection measurements to determine microwave power dependence of the capacitance of parallel-plate ferroelectric varactors. It is shown that the nonlinear parameters estimated from this experiment are in good agreement with the nonlinear parameters found from C(VDC) measurements at low frequencies. Hence; nonlinear parameters found from simple C(VDC) measurements may be used in the development of microwave devices; such as harmonic generators and mixers.

No. of pages:4
Series:Linköping Electronic Conference Proceedings
ISSN (print):1650-3686
ISSN (online):1650-3740
Publisher:Linköping University Electronic Press; Linköpings universitet

Pär Rundqvist, Andrei Vorobiev, Spartak Gevorgian (2003). Microwave power dependent properties of ferroelectric varactors, GigaHertz 2003. Proceedings from the Seventh Symposium;article=068 (accessed 10/1/2014)