Electronics World Cover,TOC,and list of posted Popular Electronics articles QST Radio & TV News Radio-Craft Radio-Electronics Short Wave Craft Wireless World About RF Cafe RF Cafe Homepage RF Cafe in Morse Code Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs Twitter LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes AN/MPN-14 Radar 5CCG Notable Quotes App Notes Calculators Education Magazines Software,T-Shirts,Coffee Mugs Articles - submitted by RF Cafe visitors Simulators Technical Writings RF Cafe Archives Test Notes Wireless System Designer RF Stencils for Visio Shapes for Word Search RF Cafe Sitemap Advertising Facebook RF Cafe Forums Thank you for visiting RF Cafe!

VCO Buffers Design Similar to LNA Design ? - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


Philip_WNL
Post subject: VCO buffers design similar to LNA design ? Posted: Thu Oct 30, 2008 2:42 am

Lieutenant

Joined: Thu Oct 30, 2008 2:16 am
Posts: 2
Hi All,

(glad to be member of this well known place)

Having designed a 5GHz differential Pmos cross-coupled negative-gm VCO, I checked the output impedance with a sp analysis (assuming no buffers are connected), it has a real and imaginary part. THEREFORE:

- Should we arrange a matching network (just like in LNA design) at the input of the buffer ?

- In case a reduction of the output amplitude of the VCO is desired, can't we make an impedance MISmatch instead of passive scaling in the VCO core ? in that case, the reflected wave could disturb the VCO right ?

Since noise is also a concern (since phase noise is attempted to be minimize), a VCO buffer start looking pretty much like an LNA (with lower gain thought)

Your comment about these unclear issues are most welcomed. Thanks.


Top

Tony Kurlovich
Post subject: Posted: Mon Dec 15, 2008 11:36 am

Captain


Joined: Thu Oct 19, 2006 6:02 pm
Posts: 7
If the loading output of the VCO significantly changes the VCO, do not do conjugate match. You reduce the signal in the loop and degrade the phase noise that you worked so hard for. The consequence of lightly coupling the buffer to the VCO is broad band flat noise. There is usually more room for flat noise degredation than for close in phase noise degredation.








Posted  11/12/2012

RF Cafe Software

   Wireless System Designer - RF Cafe
Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chartâ„¢ for Visio
Smith Chartâ„¢ for Excel

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2022
Webmaster:
Kirt Blattenberger,
 BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:
 AirplanesAndRockets.com

Try Using SEARCH
to Find What You Need. 
There are 1,000s of Pages Indexed on RF Cafe !

height-line