Custom Search
Over 10000 Pages Indexed
Your Host
Click here to read about RF CafeKirt
Blattenberger

... single-
handedly
redefining
what an
engineering website
should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse
riding business website -
lots of info

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe©

RF Cafe E-Mail

Factor affecting the phase noise in oscillator - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


satish.1979
Post subject: Factor affecting the phase noise in oscillator Posted: Tue Nov 21, 2006 3:59 am

Captain

Joined: Tue Oct 03, 2006 3:03 am
Posts: 11
Location: India
I am interested to know what are the factor which can effect the phase noise of the oscillator other than the Q of the Resonator.


Top

IR
Post subject: Posted: Wed Nov 22, 2006 7:29 am

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello satish,

The other factors which affect phase noise are:

1. The NF of the active device.
2. The offset frequency from the center frequency (At which the phase noise is being measured)
3. The average power through the resonator circuit and active device.
4. The Flicker corner frequency of the active device.
5. Temperature of operation.

These factors are included in the Lesson's formula which defines the phase noise of an osscilator.

Please look at this link which gives a good overview:

http://www.zen118213.zen.co.uk/Systems_ ... eNoise.pdf

_________________
Best regards,

- IR


Top

nubbage
Post subject: Posted: Wed Nov 22, 2006 8:50 am

General


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Satish
The only thing I would add to IR's very comprehensive reply would be the presence of any dissimilar metal contact that can give rise to intermodulation (at very low level, but significant). The spectral noise lines resulting from all the processes mentioned by IR then mix with each other and thus spread component sidebands even further out from the carrier. Thus the slope of dBW/Hz is therefore reduced.


Top

IR
Post subject: Posted: Wed Nov 22, 2006 9:27 am

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Another issue which is more physical rather than electrical is of course PCB layout. You need to follow good PCB layout practices in order to achieve good phase noise performance.

In addition to that, you should apply adequate filtering to the oscillator's supply rails. There is even a special circuit known as "Super Filter" which is made of an NPN transistor including bypass capacitors of several values at both the NPN's base and collector. This circuit reduces the voltage from the supply to the level required by the oscillator. The emitter of the NPN is connected to the supply rail of the active device in the oscillator circuit. The only disadvantage is that you need to provide a higher voltage to the NPN's collector due to the Vce voltage drop. The NPN's DC operating point is set with voltage divider in the base.

I hope that you understood from the description how the circuit looks like and operates.

_________________
Best regards,

- IR



Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel