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 low
Since 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 4-12Ghz
The 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 150mA
2) Bias : 12VDC 110 mA
3) Coil : from 150 to 650 mA
I 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 17dBm
On the picture there is a 10dB attenuator on the frequency meter.