Basic Question

[ukalyan]

Hi ,
This might be a basic question to most of you
I have an RFID reader and an antenna.
The reader has a maximum power output of 200mw.
The antenna has a maximum RF power of 10w.
If I connect the reader to the antenna, what will be the general RF power of the Antenna.

Thanks.

 

[IRstuff]

maybe 200 mW?

TTFN

 

[logbook]

Well of course a more directive antenna (higher gain) will put more power out in a particular direction. You then use "effective isotropic radiated power" as a useful measure. Google on EIRP for more info.

You will only get 200mW total power out of the antenna if the antenna is lossless and matched to the reader. Therefore you are unlikely to get as much as 200mW output from the antenna.

 

[nmnm87]

Read , antenna theory book , balanis , u must first have no reflection from the antenna to the RFID , and in other words u must match the outputimpedance of the RFID to the input impedance of the antenna , what is ur antenna , dipole monopole and what is ur operation frequnecy

 

[K7FE]

The output of the antenna can NEVER exceed the power applied to it in a true 3D omni directional pattern. If you have a antenna that is rated for a million watts and you feed it with 200 mw, the power out of the antenna will be 200 mw, less losses in feed line and antenna efficiency. So as others have said, the power out of your antenna will be typically a little less than 200 mw.*

Effective radiated power may be increased beyond 200 mw in a particular direction thru the use of “gain” antennas which focus or compress the radiated signal in a particular direction at the expense of other directions in a manor similar to optics. My assumption is that your reader is portable and you are looking for an omni directional pattern, providing a signal in all directions much like a candle illuminates a room as opposed to a flashlight which provides light in a narrow beam in one direction.

*(Assuming the feed line has low losses and the antenna is a resonate 1/4 wave or half wave antenna at the frequency of operation and the feed line is matched to the antenna on one end and the reader on the other.)

Good luck.