Adaptivity of voltage-controlled oscillators - theory and design

Abstract

Abstract-Analog RF front-end circuits are typically designed to perform one specific task, while key parameters such as dynamic range, bandwidth and selectivity are fixed by the hardware design and not by the communication system in an adaptive way. As a result, today's receiver topologies are designed to function under the most stringent conditions, which increases circuit complexity and power consumption. However, the conditions under which the RF circuits operate are not fixed but vary widely and depend upon a multitude of factors. Therefore, a concept of design for adaptivity is introduced in this paper. It establishes a trajectory for an all-round performance characterization of adaptive oscillators with an explicit qualitative and quantitative description of all the existing relations and tradeoffs among the oscillator performance parameters. As a proof of concept, an 800-MHz adaptive voltage-controlled oscillator is designed with phase-noise tuning range of 7 dB and more than a factor 3 saving in power consumption, suitable for unobtrusive mobile equipment, foreseen to operate in this band.

Adaptive multi-standard circuits and systems for wireless communications

“…Designing for adaptivity [18] is in such a situation a better solution than a "fixed" design practice, which is "blind" and "deaf" for the volatile specifications imposed by the air interface.…”

“…The concept of phase-noise tuning [18] shows explicitly how phase noise and power consumption trade between each other in an adaptive way.…”

“…Thus, frequency-transconductance (C-g m ) tuning [18] is the control mechanism compensating for the change in the VCO LC-tank characteristic (whose conductance is changed due to frequency tuning) by varying the oscillator's bias conditions (i.e., the transconductance g m ).…”

Issues on the design and implementation of radio frequency CMOS LC tank voltage-controlled oscillators

“…In addition to this, the current trend in integrated RF design is toward multi-band multi-standard transceivers and broadband systems. In such systems it is desirable that the LO is sharable amongst the different standards provided on-chip and that it has some level of adaptivity such as the facility of trading-off power consumption for performance ''on the fly'' according to the requirements of the transmission environment or the standard being used [1][2][3][4].…”

A PLL design based on a standing wave resonant oscillator

“…Typical oscillators on a digital IC use some form of Voltage Controlled Oscillator (VCO) [7], [8], [9], [10], [11], and implement a PLL with the VCO in a closed-loop configuration. A phase frequency detector (PFD) determines the phase error, and accordingly either speeds up or slows down the oscillation frequency of the VCO.…”