Wireless lan in the sea
I can enlarge the directivity or the power.
(The part I should design is only the antenna)
The problem I think is the loss tangent and the permittivity of sea water.
The permittivity of sea water is around 80
I'd like to listen to your opinion.
It is possible but acoustic methods are cheaper. One problem is the high power required. Land stations can easily generate MW levels but submarines cannot.
Suppose a typical conductance of sea water of 4 S/m, then the attenuation is over 1000 dB/m at a frequency of 1GHz !!
The typical frequencies used in submarine electromagnetic telecommunication (by Militars) are in the VLF or ELF frequency bands; ant the antennas are very very large...
Hi
yes, very high attenuation of sea water and hence very low frequency, --> crazy long wire antenna. lolz. I heard some research works about using acoustic wave as the signal carrier, and utilize almose same array theory of antenna array, they build up acoustic trans/receiver array and do the singla processing.
Anybody involved in this area can give more details?
Best Regards,
Dear Sir
In almost all underwater communication systems the means of energy transfer is acoustic rather than EM. EM energy is not useable underwater due to very high attenaution. In the book titled "Sonar for practising engineer" by A.D Waite on page XXI titled "Why radar is not used to detect underwtaer targets", the author writes
"EM Losses in the highly conductive sea water are given by 1400f*(1/2) dB/km, where f is in Khz and for just a 100m path in the sea, the losses at 2000 Mhz are 200,000dB!. Even at 30KHz the losses equal 770dB; the sea effectively presents a short circuit to the EM Energy."
I hope that clarifies why cant we use EM enrgy underwater for any purpose. Even in the Echo Sounder and UWTs(Under water Telephones), popularly known as Secondary Sonars the medium is acoustic or sound energy..
Wishing u luck
Ess ESS