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First, its sound oscillators for low-frequency audio waves. Then Radio wave oscillators varying from low frequency AM to high frequency Cell-phones. Then microwave oscillators in the giga hertz. What is the highest frequency that electronics can generate and what are the uses?

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    \$\begingroup\$ Does a laser count as (part of) an electronic circuit? A laser diode? How about an x-ray tube? \$\endgroup\$ – The Photon Apr 23 '13 at 16:19
  • \$\begingroup\$ that isn't electricity that u can put through wires \$\endgroup\$ – skyler Apr 23 '13 at 16:20
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    \$\begingroup\$ you might want to edit your question to clarify. \$\endgroup\$ – The Photon Apr 23 '13 at 16:22
  • \$\begingroup\$ I read about a near-THz transistor the other day. The original article is in Dutch, but here is a Google Translate version \$\endgroup\$ – jippie Apr 23 '13 at 18:37
  • \$\begingroup\$ Here's one that's an oscillator rather than an amplifier, also 1.04 THz: ntt-review.jp/archive/… \$\endgroup\$ – The Photon Apr 23 '13 at 19:04
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http://spectrum.ieee.org/semiconductors/devices/transceivers-to-conquer-the-terahertz-frontier/2 is a good read to start from.

There isn't a hard upper limit, but it gets increasingly painful to work with and starts crossing over into the domain of optics and optoelectronics. One of the limits mentioned there is that it takes a distinct amount of time for a signal to travel through a transistor, so transistors become unusable; that article claims this is somewhere in the hundreds of GHz.

Parasitic capacitance also becomes an issue; the higher the frequency, the easier it is for the signal to just leak out through the few pF capacitance between your wire and the nearest other bit of metal. This effect limits the usable frequency of signals on breadboards to a few MHz.

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  • \$\begingroup\$ Any electronic oscillator will have electrons jiggling back and forth. Now according to Special Relativity these electrons cannot move faster than light, not even tiny distances. So there will be an upper limit when the frequency gets so high that electrons are jiggling at relativistic speeds. \$\endgroup\$ – Mr X Sep 14 '16 at 23:11
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According to the Wikipedia article Terahertz radiation, "in this [terahertz] frequency range the generation and modulation of coherent electromagnetic signals ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, and requires new devices and techniques."

This implies that the next lower band, millimeter wave, is the highest where "conventional electronic devices" can be used to produce signals.

Millimeter wave signals have frequencies between 30 and 300 GHz.

Applications include point-to-point wireless communication, imaging (as in airport scanners), and remote sensing.

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  • \$\begingroup\$ This is known as UWB - Ultra Wide Band - in some circles. \$\endgroup\$ – placeholder Apr 23 '13 at 21:15
  • \$\begingroup\$ @rawbrawb, my understanding is UWB means using very short pulses. It may reach to millimeter-wave frequencies but doesn't neccessarily. "Millimeter wave" could also include carrier-based signalling (or remote sensing), which wouldn't be UWB. \$\endgroup\$ – The Photon Apr 23 '13 at 22:00

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