voltage controlled oscillator
The fast emerging wireless technology, such as 5GHz Wireless LAN (WLAN) in US, or High Performance Radio LAN (HIPERLAN) in Europe demands low cost integrated RF transceiver. As an alternative to traditional high cost GaAs, BJT RF technologies, CMOS technology has been proven to be suitable for RF application when the MOS device is scaled down to submicron regime. The benefit of using standard CMOS process is its potential possibility of integrating the whole RF transceiver on a single chip at lower cost. In order to achieve a single chip radio on bulk CMOS, we may face lots of design challenges. One of the challenges is to design an integrated CMOS VCO at microwave frequency with low phase noise. The phase noise of a VCO is a very critical specification for many wireless communication systems. However, different modulation schemes have different phase noise requirements. For 5GHz WLAN, OFDM (Orthogonal Frequency Division Multiplexing) is expected to be the modulation scheme. Since OFDM system performance is very sensitive to phase error, as a result, the phase noise requirement of this system is very stringent even at low offset frequency, such as 10kHz and 100kHz.
Close in carrier phase noise of CMOS VCO is usually dominated by two components. One is thermally induced phase noise, which is originated from thermal noise sources inside a VCO and has 1/f2 characteristics; the other is 1/f induced phase noise, which is due to 1/f noise up-conversion and has 1/f3 characteristics. When deep sub-micron MOS devices are used for high frequency VCO, 1/f induced phase noise could be very significant at 10kHz and 100kHz. In recent years, low phase noise LC type integrated CMOS VCO is a very active research topic. Since phase noise is inversely proportional to Q2, where Q is the loaded Q of an LC tank, thus, increasing Q is the main focus of current research. However, due to the substrate loss of bulk CMOS, the Q factor of on chip inductor and varactor has limited room to improve at microwave frequency. Therefore, further phase noise improvement, particularly the 1/f induced phase noise needs some alternative methods. In this paper, a low frequency feedback concept originated from discrete microwave community was first applied and implemented in high frequency integrated LC CMOS VCOs for 1/f induced phase noise suppression.
Design of VCO
Fully Integrated RF VCO for Wireless Transceivers, International Symposium on Signals, Systems, and Electronics
RF-CMOS Oscillators with Switched Tuning , Custom IC Conf
RF-CMOS Oscillators with Switched Tuning Custom IC Conf, presentation slides
How Phase Noise Appears in Oscillators
A 900 MHz CMOS LC-Oscillator With Quadrature Outputs
Voltage Controlled Oscillator application note, This application note explores the design fundamentals needed to implement a trimless, fixed-frequency, IF voltage-controlled oscillator (VCO) and points out the challenges in guaranteeing proper circuit operation
VCO Phase noise
The term phase noise is widely used for describing short term random frequency fluctuations of a signal. Frequency stability is a measure of the degree to which an oscillator maintains the same value of frequency over a given time
Using a VCXO as a Clock Generator
VCXO (Voltage Controlled Crystal Oscillator) is an oscillator whose frequency is determined by a crystal, but can be adjusted by a small amount by changing a control voltage.
VCXO’s Voltage Controlled Crystal Oscillators
VCXO’s Voltage Controlled Crystal Oscillators, A VCXO (voltage controlled crystal oscillator) is a crystal oscillator which includes a varactor diode and associated circuitry allowing the frequency to be changed by application of a voltage across that diode,
Quartz oscillators free download papers
Introduction to Quartz Frequency Standard
More than one billion (i.e., 109) quartz crystal oscillators are produced annually for applications ranging from inexpensive watches and clocks to radionavigation and spacecraft tracking systems. The fundamentals of quartz oscillators are reviewed in this report, with emphasis on quartz frequency standards (as opposed to inexpensive clock oscillators). The subjects discussed include: crystal resonators and oscillators, oscillator types, and the characteristics and limitations of temperature-compensated crystal oscillators (TCXO) and oven-controlled crystal oscillators (OCXO). The oscillator instabilities discussed include: aging, noise, frequency vs. temperature, warmup, acceleration effects, magnetic field effects, atmospheric pressure effects, radiation effects, and interactions among the various effects. Guidelines are provided for oscillator comparison and selection. Discussions of specifications are also included, as are references and suggestions for further reading
This specification covers the general requirements for quartz crystal oscillators used in electronic equipment. The crystal oscillators covered by this specification are unique due to the fact that these devices must be able to operate satisfactorily in systems under demanding conditions such as: 20 g’s vibration, 100 g’s of shock, 24 hours of salt spray, wide temperature range (e.g., -55°C to +85°C) and low noise under vibration. In addition, these requirements are verified under a qualification system. Commercial components are not designed to withstand these Environmental conditions.
Das Grosse Quarzkochbuch, Bernd Neubig & Wolfgang Briese Feldkirchen: Franzis-Verlag, 1997, in German. Available per chapter at http://www.axtal.com/info/buch.html, merged into one file with complete bookmarks.