Building a Microwave Generator - Page 1
Forum section: electronics / projects

author: eurofox
author_rank: Unknown
timestamp: August 18, 2014, 04:06:07 pm
content: For testing purpose I need a RF signal from 4Ghz to 12Ghz.I started to build a simple generator with a VCO at 10Ghz (tunable at +/- 1 Ghz) but only 2 dBm output, since I use a power splitter in my testing configuration the residual level was to lowSince I don't want to spend a fortune on a used "modern" generator nor use a 19 inch monster on my instrument shelf that is anyway not cheap (technology from 20 years ago) I decided to build a small one myself with minimum the requirement 4-12GhzThe easy way to build such a generator is using a YIG oscillator, for people interested in this technology :http://www.microlambdawireless.com/apppdfs/ytodefinitions2.pdfI was lucky to score one on ebay working from 3,2Ghz till 14Ghz for a good price.A YIG oscillator is current driven, the frequency is virtually proportional to the current that flow in the coil.In my case I need 3 supply's:1) Heating : 12VDC 150mA2) Bias : 12VDC 110 mA3) Coil : from 150 to 650 mAI need as well 5VDC to drive the display. Since the frequency is virtually proportional to the current I just add a shunt between the power supply from the coil and a 1K ohm variable resistor in parallel to tune the mV/Frequency.For stability reason I have limited the minimum frequency at 3,5Ghz min and 13,5Ghz max.Output is between 15 and 17dBmOn the picture there is a 10dB attenuator on the frequency meter.

author: German_EE
author_rank: Super Contributor
timestamp: August 18, 2014, 05:53:03 pm
content: Way beyond me, the highest I've ever worked at is 500 MHz and even that was more of an art than a science. Try talking to the people at Minicircuits or Synergy Microwave.www.minicircuits.comhttp://synergymwave.com

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 18, 2014, 06:58:39 pm
content: Quote from: German_EE on August 18, 2014, 05:53:03 pmYou don't need voodoo or a grey beard to use a YIG, it's basically a VCO in a box, you give it the right supply and out comes the RF

author: HighVoltage
author_rank: Super Contributor
timestamp: August 18, 2014, 07:11:39 pm
content: I just looked on ebay for "YIG tuned" and found 66 items, some of them are really low cost.Are you just building it for fun or why are you not buying one of those available for sale?What kind of testing are you planing to do at those high frequencies?

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 18, 2014, 07:28:24 pm
content: Quote from: HighVoltage on August 18, 2014, 07:11:39 pmNot sure what your search showed you but OP stated that he bought a YIG tuned oscillator from ebay.I don't see anything complete in a box with that search term.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 18, 2014, 08:06:53 pm
content: I discovered YIG oscillators & filters a few years ago. They are fun little toys, aren't they?A typical YIG driver is actually a voltage to current converter. Put in 0 - 10 volts and the output current changes to tune the oscillator. The nice thing about a driver like that is that you can have pots to tweak the top and bottom ends to minimize the error.If you want to get fancy, you can use a synthesized controller to lock the YIG to a reference. Very cool!Ed

author: eurofox
author_rank: Unknown
timestamp: August 18, 2014, 08:32:30 pm
content: Quote from: HighVoltage on August 18, 2014, 07:11:39 pmI use of course a YIG "contained" oscillator, I don't build based on the crystal.I need it to test a 11Ghz sampling oscilloscope.

author: eurofox
author_rank: Unknown
timestamp: August 18, 2014, 08:42:43 pm
content: Quote from: edpalmer42 on August 18, 2014, 08:06:53 pmI use a 10 turn precision potentiometer and variable resistors for the low and high limits.I can tune up to 1Mhz resolution, it is quite stable after heating up without feed back.My first idea was to include a variable attenuators but I expected a "small box" and adding attenuators could easily triple the size of the box, I have several SMA attenuators to get the signal level I need.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 18, 2014, 08:53:04 pm
content: Quote from: eurofox on August 18, 2014, 08:32:30 pmYou'll also want a very fast step generator.

author: eurofox
author_rank: Unknown
timestamp: August 18, 2014, 10:28:22 pm
content: Quote from: Alex Eisenhut on August 18, 2014, 08:53:04 pmI need to finish my ultra fast pulse generator (25ps rising edge)I need to check as well the Tektronix 284 pulse generator that I bought

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 19, 2014, 02:14:16 am
content: Quote from: eurofox on August 18, 2014, 10:28:22 pmI also have a 284, as well as a S-52.Here's one for 5$ starting bidhttp://www.ebay.com/itm/Tektonix-S-52-Pulse-Generator-Head-untested-/251617440148?pt=LH_DefaultDomain_0&hash=item3a95917194