Improved switched tuning of differential CMOS VCOs

• Varactors for continuous frequency tuning are typically used in LC-oscillators. However, they have some drawbacks for large tuning-ranges, such as high tuning sensitivity causing high sensitivity to noise and disturbances on the control voltage. Furthermore, large metal-oxide-semiconductor (MOS) varactors have high conversion of harmless amplitude noise into harmful phase noise. To reduce these problems a small varactor can be used in combination with MOS-transistors that switch fixed capacitors in and out of the oscillator. The limitations due to the imperfect complementary metal-oxide-semiconductor (CMOS) switches are investigated, and an improved structure for use with the popular differential CMOS LC-oscillator is presented.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

complementary metal-oxide-semiconductor

differential

frequency tuning

oscillator

switched tuning

RF CMOS

(CMOS)

varactor

voltage-controlled oscillator (VCO)

Publication and Content Type

art (subject category)

ref (subject category)