Negative Gain Antenna Applications

[Ali.Raza]

Hello,

I am working on an Electrically small antenna and the gain is negative. I need to defend this with some applications where negative gain antenna is used.

Can someone guide me about applications of negative gain antenna?

 

[PlanarMetamaterials]

Welcome Ali.Raza,

I don't think "negative gain" is ever specifically sought, but electrically small antennas have numerous applications. You might want to check out a literature review in say, the IEEE journals or magazines.

 

[biff44]

assuming you mean the gain is less than 0 db?

well, electrically small antennas are not that uncommon. automobile am radio stations are electrically small, but work fine. that is because the system gain is high enough for useable audio to be transmitted (albeit requiring hundred killowaatt+ transmitters to get any range).

another feature of electrically small antennas is that they often are NOT resonant structures. So you can have very large bandwidths, but might need to change the type of receiver amplifier to be a voltage gain, or current gain type (to match to either a very high radiation resistance, or a near short circuit from a small loop antenna), instead of using a a 50 ohm input impedance amplifier. An AM radio receiver in your car has a high impedance input voltage gain amplifier in the front end.

so you also need high enough system gain to for the antenna system gain loss.
can you only operate at short distances?
can you direct the transmit beam to track where this small receiver antenna is?
can you expand your modulation bandwidth by A LOT, and employ digital coding gain to the compensate for the antenna loss?
Can you utilize MIMO signal processing to add multiple propagation paths to get more energy into the system input?

 

[volker@muehlhaus]

I need to defend this with some applications where negative gain antenna is used.

Antenna gain is a result of directing radiation, instead of radiating omnidirectional into all directions. So if your antenna has a wide pattern, we don't expect much antenna gain.

Negative gain (negative dB) can be the result of a wide pattern with some internal antenna loss.
A useful number is the antenna efficiency: how much of the input power is actually radiated.

 

[metamaterialantenna]

It can be used on Implantable devices. Please check the following reference

(PDF) A Compact Design for Dual-band Implantable Antenna Applications

PDF | This paper presents the development of a dual-band antenna working at the Industrial, Scientific, and Medical (ISM) band (902-928 MHz, 2.4-2.5... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

 

[Ali.Raza]

It can be used on Implantable devices. Please check the following reference

(PDF) A Compact Design for Dual-band Implantable Antenna Applications

PDF | This paper presents the development of a dual-band antenna working at the Industrial, Scientific, and Medical (ISM) band (902-928 MHz, 2.4-2.5... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

Thank you, Yes was looking for this type of answers

 

[hagster]

Chu–Harrington limit - Wikipedia

en.m.wikipedia.org

Look up Chu limit.

 

[biff44]

if you do not care about the signal propagating far, you can just use coils and transmit in the near field with magnetic coupling.