Jyrki Kaitila

High coupling coefficient Temperature compensated FBAR resonator for oscillator application with wide pulling range

This paper demonstrates two variations of Temperature compensated (TempCo) FBAR resonators with high Kt². One 1.5 GHz non-symmetric stack design TempCo FBAR resonator has a Kt² of 4.28% and linear TCF of 0 ppm/°C. A second, quasi-symmetric stack design 1.5GHz TempCo FBAR resonator has Kt² as high as 5.6% and linear TCF of −6 ppm/°C. Significant Kt² improvement comes from optimal design of stack film, interposer electrode effect and novel process development of a sealant for the oxide to protect it from HF etching. This paper also discusses the trade-off between two parameters (linear TCF vs. Kt²). High Kt² TempCo FBAR resonator is ideal for FBAR oscillator application with wide frequency pulling range.

A 22µW, 2.0GHz FBAR oscillator

We present a 22µW, 2.0GHz FBAR oscillator - the lowest power reported to date for a GHz-range oscillator of this type. Low power consumption is achieved through co-design with a high Rp FBAR resonator and a weakly-forward biased bulk connection. An oscillator with a standard bulk connection was fabricated for comparison. The chip was fabricated in a 0.18µm CMOS process. The weakly-forward biased bulk led to a 41% reduction in power dissipation. The measured phase noise is −121dBc/Hz at a 100kHz offset.