DIY Gigahertz oscillator

[CCatalyst]

TL;DR Summary

The name says it all. This is going to be a stretch.

Now, I once read in another thread here someone else was trying to make a kilohertz oscillator. The forum members said not to use a breadboard as it would create too much noise. So What do you recommend as an alternative? Or should I just connect the components without the foundation? Also, where can I get an operational amplifier that can handle such high frequencies?

 

[Tom.G]

I think your search for an op-amp at that frequency is a search for pure unobtainium. Though you could probably find some individual transistors that work.

Try this:
https://www.google.com/search?&q=gunn+oscillator+experiment

Also just type gunn oscillator into the Google search box for other suggestions.

Cheers,
Tom

 

[Baluncore]

A breadboard will have many stray inductance and capacitance couplings so it will oscillate at uncontrolled frequencies. The long leads on a breadboard will couple EMI from the world around and modulate the oscillation, reducing the purity and making the signal noisy.

At VHF and below the resonant frequency is set by varying the lumped values of inductance or capacitance. It will need to be physically and thermally stable.

At UHF and above the dimensions of the circuit become critically important. An oscillator at a GHz frequency will be tuned by varying the loading of a short transmission line. The lines will need to by physically rigid and thermally stable, probably needing Invar components or thermal compensation.

Most transistors and op-amps have a specified GBP = Gain Bandwidth Product. That will give you a good idea of the maximum frequency possible, since to oscillate there must be sufficient gain remaining to both overcome resistive circuit losses and provide some output power. Too high a GBP and it will oscillate at other harmonic frequencies. Too little GBP and it will not always start to oscillate.

So What do you recommend as an alternative? Or should I just connect the components without the foundation?

Build your oscillator on an unetched PCB copper ground plane by gluing chips down on their back like dead ants. That way you can ground any point by soldering it to the plane. Surface mount ceramic capacitors stand like tomb stones where supply voltages reach transistors. Strips of single sided PCB are glued to the groundplane, cut to width setting the impedance of transmission lines or interconnections. EMI pickup is reduced by having the circuit close to a ground plane.

 

[berkeman]

Summary:: The name says it all. This is going to be a stretch.

Now, I once read in another thread here someone else was trying to make a kilohertz oscillator. The forum members said not to use a breadboard as it would create too much noise.

That's likely a typo. Kilohertz oscillators are easy to build on breadboards. Even low MHz oscillators can generally be breadboarded. Once you get up into the 10s of MHz and above, you need to use careful prototyping technique, and when you get above about 100MHz and into the GHz range, you need to be simulating and making PCB-level boards.

BTW, just to ask the next obvious question, what are you going to do with this GHz signal? You need to be extremely careful not to allow any electromagnetic interference (EMI) to radiate from your setup and cause interference with any radios in the area. Just think what would happen if you started interfering with local emergency radio frequencies...