This is not the document you are looking for? Use the search form below to find more!

Report home > Technology

Improving System Performance and Frequency Stability with New VCXOs

0.00 (0 votes)
Document Description
Oscillators provide a consistent and stable timing reference for an electronic system or for a module(s) within the system. In some applications, the output frequency of the oscillator needs to be adjusted after the system is in operation.
File Details
  • Added: March, 05th 2012
  • Reads: 76
  • Downloads: 0
  • File size: 169.05kb
  • Pages: 1
  • Tags: clock generators, crystal oscillator, voltage controlled oscillator
  • content preview
Submitter
Embed Code:

Add New Comment




Related Documents

Essentials of System Analysis and Design Valacich 4th Edition Solutions Manual

by: gordonbarbier, 48 pages

Essentials of System Analysis and Design Valacich 4th Edition Solutions Manual

Essentials of System Analysis and Design Valacich 4th Edition Solutions Manual

by: georgesheslers, 48 pages

Essentials of System Analysis and Design Valacich 4th Edition Solutions Manual

Corporate, Partnership, Estate, and Gift Tax with H&R Block TaxCut 2010 Pratt 4th Edition Solutions Manual

by: georgesheslers, 48 pages

Corporate, Partnership, Estate, and Gift Tax with H&R Block TaxCut 2010 Pratt 4th Edition Solutions Manual

2011 Corporate Partnership Estate and Gift Taxation with H&R Block TaxCut Pratt Kulsrud 5th Edition Test Bank

by: georgesheslers, 48 pages

2011 Corporate Partnership Estate and Gift Taxation with H&R Block TaxCut Pratt Kulsrud 5th Edition Test Bank

Black and Decker Drill With Accessories

by: darlenerwallis, 9 pages

In every home, there's a man that wants to fix things by his own. That man may be your father, brother, husband, son or you may know somone who has same attitude.In that case, there's a perfect gift ...

Relationships Between Goal Orientation, Motivational Climate and Perceived Ability with Intrinsic Motivation and Performance in Physical Education University Students

by: shinta, 5 pages

The purposes of the present investigation were to study the relationships between goal orientation, motivational climate and perceived ability with intrinsic motivation, behavioral patterns and ...

Dose-Response Effects of Methylphenidate on Ecologically Valid Measures of Academic Performance and Classroom Behavior in Adolescents With ADHD

by: shinta, 13 pages

The effects of methylphenidate on the academic performance and classroom behavior of 45 adolescents with attention deficit hyperactivity disorder were studied. During a 6-week, ...

Maximizing DB2 Performance and Availability With BMC

by: colin, 8 pages

Maximizing DB2 Performance and Availability With BMC

Web3 And The Next Internet - New Directions And Opportunities For STM Publishing

by: kazunari, 37 pages

Web3 And The Next Internet - New Directions And Opportunities For STM Publishing

Itanium Performance and Availability Build Trust in Taiwan Pension System

by: ronja, 3 pages

Itanium Performance and Availability Build Trust in Taiwan Pension System

Content Preview



Improving System Performance and Frequency Stability with New VCXOs
Oscillators provide a consistent and stable timing reference for an electronic system or for a module(s) within the system.
In some applications, the output frequency of the oscillator needs to be adjusted after the system is in operation. System
designers can use a voltage-controlled oscillator (VCXO) which has the capability to adjust its output frequency.
This frequency tuning technique can be used in many types of equipment including products developed for telecom,
networking, wireless communications, instrumentation, audio/video and FPGA-based applications. One reason to use a
VCXO is when the output frequency needs to be synchonized to an external reference frequency. For example, when
data is transmitted from one end of a system to another (either wired or wirelessly), the data stream must synchronize on
the receiving side. If the data does not match, a VCXO on the reciever side will use the embedded clock information to
adjust or "pul " its frequency to synchronize with the exact frequency of the transitting side.
The VCXO is pulled by changing the control voltage. In quartz-based oscillators, this is typically done by placing a
varactor diode on both sides of the quartz crystal oscillator and changing the capacitance by applying a reverse bias. In
such devices, the total amount of frequency tuning may be limited by the characteristics of the crystal and the varactor
diodes.
In oscillators that use micro electro-mechanical systems (MEMS) technology, a silicon resonator is used instead of a
quartz resonator, and tuning is achieved through use of a phase locked loop (PLL). With any type of VCXO used in a high
performance system, pull range, tuning slope (Kv), phase noise and frequency stability are important design
considerations. Parameters for these key specifications vary considerably depending on the design and technology used
for the timing device.
Pull/tuning range: With quartz devices, the output frequency can only be adjusted up to a couple of hundred parts
per million (+/- 100 to 200 ppm). In MEMS-based oscillators, the device is not limited with quartz crystals that
have a small pull range. The frequency in MEMS VCXOs can be adjusted up to several hundred parts per million
( 25 to 1600 ppm), offering an extremely wide pull range.
Tuning slope/linearity: With quartz devices, the varactor is non-linear and this translates to a non-linear slope in
tuning gain especially close to 0V or Vdd. As voltage increases, frequency should increase at a constant rate.
However, with quartz the slope deviates in the range of +/- 10%. In contrast, MEMS timing devices are extremely
linear and have superior tuning slope consistency in the range of +/- 0.1 to 1%.
Frequency stability: To achieve higher pull range in quartz VCXOs, a lower quality (low-Q) crystal must be used.
Lower Q-factor quartz oscillators have more jitter. This negatively affects frequency stability and phase noise -
two performance characteristics that are very important in applications that use VCXOs. With MEMS devices, this
is not an issue because they do not use quartz crystals.
Temperature drift: Voltage control can be used in temperature-compensated oscillators (TCXOs). Timing devices
with this combined capability are called VCTCOXs. In quartz devices, allowances for temperature drift need to be
made. Temperature drift is a problem with VCXOs since temperature varies over the voltage control range.
Temperature-compensation helps to reduce drift.
In high performance systems, frequency stability and low phase noise are critical and have a direct impact on system
performance. In quartz-based VCXOs, noise in the tuning slope negatively affects phase noise. Quartz devices are less
flexible with limited pull range. Plus they have lower performance in terms of linearity, stability and drift. In contrast,
MEMS-based VCXOs have a much wider pull range without the performance tradeoffs. In addition, MEMS timing devices
across all categories - XOs, VCXOs, TCXOs and clock generators - have much higher reliability and more flexibility with
customizable features. As designers look for new solutions to optimize their systems, they are implementing control
techniques such as those employed in VCXOs, TCXOs, as well as using new MEMS technology to further enhance
performance.


Download
Improving System Performance and Frequency Stability with New VCXOs

 

 

Your download will begin in a moment.
If it doesn't, click here to try again.

Share Improving System Performance and Frequency Stability with New VCXOs to:

Insert your wordpress URL:

example:

http://myblog.wordpress.com/
or
http://myblog.com/

Share Improving System Performance and Frequency Stability with New VCXOs as:

From:

To:

Share Improving System Performance and Frequency Stability with New VCXOs.

Enter two words as shown below. If you cannot read the words, click the refresh icon.

loading

Share Improving System Performance and Frequency Stability with New VCXOs as:

Copy html code above and paste to your web page.

loading