MiniCircuits has a bi phase electronic attenuator that uses a PIN diode ring in what is normally a balance mixer configuration. They range from 8 to 23 US Dollars.
Research Links
- Google: bi phase attenuator site:minicircuits.com
- Comparison of PIN ring with standard Schotky diode ring mixer that shows linearity is much better
- FAQ about electronic attenuators
- Minicircuits model page link#1
- Minicircuits model page linke#2
- Minicircuits model page link #3