NLJD frequency under 800MHz?

[CopperCone]

So looking at the industry, I see that NLJD typically will stimulate between 800 to 4000MHz.

Does anyone know why this lower bound of 800MHz was set? The upper bound I understand, I found it rather finicky to pickup the 12GHz harmonic of stuff (slight movement of objects around the room effects the reading), plus there is heavy attenuation. I feel that above four gigahertz you would need to basically setup a empty room or use an anechoic chamber (so its more like a lab tool).

I can't find anything on the market that does less then 800MHz. I figure there would be benefits of cost, ease of manufacture, etc.

Interference with official bands? Most things wont mix it (is this a frequency when things stop being microwavy)? antenna too big for commercial use (thought it might be hard to make an antenn that does 400, 800 and 1200 MHz? I thought that penetration into objects would be superb, and so would return loss from the emitter being stuck inside of something.

[ahbushnell]

What is NLJD?

[isecus88]

NLJD stands for Non-linear Junction Detector. It is also called harmonic radar. It emits a fundamental wave signal, receives the 2nd, 3rd or even higher harmonic/combined wave echo signals re-radiated from the target, and detects them. It is a Radar system for target judgment, identification and detection. Compared with general fundamental wave radars that only receive fundamental wave signals, harmonic radars can not only obtain fundamental wave channel information from the target, but also obtain 2nd, 3rd and higher information. Besides, Harmonic radar has better clutter suppression than ordinary radar and has stronger filtering capability.

Natural objects generally do not have the ability to re-radiate harmonics, such as mountains, oceans, land, etc., and purely man-made objects such as metal blocks will not produce harmonic radiation. Only the place where two metals combine to produce oxides (MOM) will produce harmonic radiation. Wave radiation, the most representative is the metal oxide and semiconductor PN junction.

In view of this characteristic, NLJD can be used to detect various electronic equipment, explosive electronic control devices, eavesdroppers, recording equipment, etc, no matter they are powed on or off. The NLJD equipment are widely used in public security, confidentiality and other fields.

Hope now it is much clear.

[TimFox]

Good technical journals require that the first time an abbreviatable term is used, it is spelled out.
Later uses in the article can then use the abbreviation.