A digitally compensated 1.5 GHz CMOS/FBAR frequency reference

Area of Science:

• Electrical Engineering
• Materials Science
• Physics

Background:

• Quartz crystal oscillators are traditional frequency references but are often bulky and power-intensive.
• Miniaturization and lower power consumption are critical for modern electronic devices.
• Film Bulk Acoustic Wave Resonators (FBARs) offer potential for smaller, more efficient frequency control.

Purpose of the Study:

• To present a temperature-compensated 1.5 GHz FBAR-based frequency reference.
• To demonstrate its feasibility using a standard 0.35 micrometer CMOS process.
• To evaluate its performance as a replacement for quartz crystal references.

Main Methods:

• Implementation of a 1.5 GHz FBAR oscillator within a 0.35 micrometer CMOS fabrication process.
• Integration of temperature compensation circuitry.
• Characterization of frequency drift over a 0-100 degrees C temperature range.
• Measurement of oscillator phase noise.

Main Results:

• Achieved an ultra-small form factor of 0.79 mm x 1.72 mm.
• Demonstrated low power dissipation of 515 microA with a 2 V supply.
• Measured post-compensation frequency drift below +/- 10 ppm over 0-100 degrees C.
• Obtained oscillator phase noise of -133 dBc/Hz at 100 kHz offset.

Conclusions:

• The developed temperature-compensated FBAR oscillator is a viable, compact, and low-power alternative to quartz crystal frequency references.
• CMOS integration enables scalable and cost-effective production.
• The device meets stringent frequency stability and phase noise requirements for advanced applications.