Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Forums Magazine Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Anritsu Alliance Test Equipment Amplifier Solutions Anatech Electronics Axiom Test Equipment Berkeley Nucleonics Bittele Centric RF Conduct RF Copper Mountain Technologies Empower RF everything RF Exodus Advanced Communications Innovative Power Products ISOTEC KR Filters Lotus Systems PCB Directory Rigol RF Superstore San Francisco Circuits Reactel RFCT TotalTemp Technologies Triad RF Systems Windfreak Technologies Withwave LadyBug Technologies Wireless Telecom Group Sponsorship Rates RF Cafe Software Resources Vintage Magazines Thank you for visiting RF Cafe!

mixer noise figure measurement - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2010 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts.

NOTICE: The original RF Cafe Forum is available again for reading, and the new RF Cafe Blog is an active board.

-- Amateur Radio

-- Anecdotes, Gripes, & Humor

-- Antennas

-- CAE, CAD, & Software

-- Circuits & Components

-- Employment & Interviews

-- Miscellany

-- Swap Shop

-- Systems

-- Test & Measurement

-- Webmaster

pigger

Post subject: mixer noise figure measurement

Unread postPosted: Sat Jul 10, 2004 2:03 am

we are measuring mixer noise figure. supposedly, it should be a smooth curve, but we saw lots of very high spurs along that curve. Has anybody here met this situation before? can anybody help me to analyze what happened?

Thanks in advance

Top

Guest

Post subject:

Unread postPosted: Sat Jul 10, 2004 12:32 pm

How are you measuring the noise figure? Are you using an automated noise figure meter that supplies both the reference signal and the LO, or are you supplying an external LO and just measuring noise floor difference from input to output, or some other method?

- Kirt B. :smt024

Top

pigger

Post subject:

Unread postPosted: Sat Jul 10, 2004 3:07 pm

we use the automated noise figure meter (actually, a VNA with noise figure measurement function) with both the ref noise source and LO

Anonymous wrote:

How are you measuring the noise figure? Are you using an automated noise figure meter that supplies both the reference signal and the LO, or are you supplying an external LO and just measuring noise floor difference from input to output, or some other method?

- Kirt B. :smt024

Top

pigger

Post subject:

Unread postPosted: Sat Jul 10, 2004 3:37 pm

I think I didn't make it clear.

I use a VNA ( just like an automated noise meter, I guess, Y-factor method) to measure the mixer noise figure. I swept the RF and LO frequency and fix the IF. VNA supplies the noise (or signal) and LO signal.

The phenomenon is at certain freq, there would be very high spurs instead a smooth curve. And "noise figure overload" would also be shown on the VNA.

Top

Kirt Blattenberger

Post subject:

Unread postPosted: Sat Jul 10, 2004 8:25 pm

Offline

Site Admin

User avatar

Joined: Sun Aug 03, 2003 2:02 pm

Posts: 308

Location: Erie, PA

Assuming that your tester is not injecting spurious signals into your DUT, it is posible that you are generating a mixer spur that falls inside the measurement band. That can definitely cause an erroneous NF reading.

You might want to try backing off the mixer input power. If possible, connect the mixer output to a spectrum analyzer and look to see if there are discrete spurs stepping across the output band as the input steps.

Kirt B. :smt024

Top

Profile

DW

Post subject:

Unread postPosted: Sun Jul 11, 2004 6:32 pm

Few things to check:

1.) are you filtering your output such that only your IF (assuming a downconversion) is getting through?

2.) Make sure there are no other pieces of equipment in the area that are on.

3.) Make sure the LO and RF 10 MHz signals synced up. Not having these synced up can induce some drift which can mess up some measurements.

4.) If its an active circuit or there are amplifiers around the mixing circuit, check for oscillations/spurs.

BR,

DW

Top

pigger

Post subject:

Unread postPosted: Wed Jul 14, 2004 2:32 am

I don't see any obvious spurs when there are no RF and LO signal coming in. but I will try backing off the input power.

Kirt Blattenberger wrote:

Assuming that your tester is not injecting spurious signals into your DUT, it is posible that you are generating a mixer spur that falls inside the measurement band. That can definitely cause an erroneous NF reading.

You might want to try backing off the mixer input power. If possible, connect the mixer output to a spectrum analyzer and look to see if there are discrete spurs stepping across the output band as the input steps.

Kirt B. :smt024

Top

pigger

Post subject:

Unread postPosted: Wed Jul 14, 2004 2:35 am

I am not filtering the mixer IF output, and I also guess maybe it's the LO leakage or RF leakage who disturbed the NF measurement. But generally is it normal to use a filter, or it is a must when measuring NF.

DW wrote:

Few things to check:

1.) are you filtering your output such that only your IF (assuming a downconversion) is getting through?

2.) Make sure there are no other pieces of equipment in the area that are on.

3.) Make sure the LO and RF 10 MHz signals synced up. Not having these synced up can induce some drift which can mess up some measurements.

4.) If its an active circuit or there are amplifiers around the mixing circuit, check for oscillations/spurs.

BR,

DW

Posted  11/12/2012

DC-70 GHz RF Cables - RF Cafe
everythingRF RF & Microwave Parts Database - RF Cafe
Innovative Power Products Passive RF Products - RF Cafe
Amplifier Solutions Corporation (ASC) - RF Cafe
Exodus Advanced Communications Best in Class RF Amplifier SSPAs

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free

 

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024

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 World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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