What is high frequency ?

[Electrolinux]

I know that the question in my message title may seem weird. The thing is I have to design a sine wave oscillator. It's probably going to be a Colpitts kind, built around a JFET device. I think I know how to do it, at least, I have a few links (epanorama.net and so on) related to it. But the problem is that the operating frequency will be 10 MHz and I don't know if I have to model the transistor with the S or Y parameters. I've read small frequencies go up to 100 KHz and I do know 1 GHz is high-frequency (well, so anybody does !!).

What about a 10 Mhz circuit, then ?

Thanks beforehand

 

[Hero999]

https://en.wikipedia.org/wiki/High_frequency

 

[Electrolinux]

And what about the filter?

Would it be the same for a band pass filter with 10 MHz as the center frequency?

 

[Electrolinux]

I didn't ask the right question

https://en.wikipedia.org/wiki/High_frequency

Thanks for your reply, Hero999. I had already read that page in the wikipedia. I still wonder if I have to make impedance matching, use the Smith Chart and all the techniques for RF design -I have the excellent book RF Circuit Design, by Chris Bowick in front of me-. I guess using all those RF techniques would be the best way to go, but my professor, who has some experience in HF design, told me not to worry about it. He told me I had to bear it in mind only when it comes to the layout (ground plane, power supply plane, and so on).

 

[justDIY]

https://en.wikipedia.org/wiki/High_frequency

this is the first thing that popped into my head:

**broken link removed**

 

[Roff]

The wavelength of 10MHz in air is about 30 meters, so you shouldn't need to worry about impedance matching except when driving an antenna (for optimum power transfer) or long transmission lines (like 3 meters or more). In my experience, Smith charts are mostly useful for looking at port impedances, return loss, etc., so the same thing is true.
As your prof said, pay fairly close attention to layout, including planes, crosstalk, supply decoupling, etc.
For a bandpass filter, you will have to consider stray and device capacitance if you want the design to be predictable.