RF power measurement in air

[7rots51]

hello

There is a 5.8GHZ transmitter that send signal in all directions,how can I measure the power strenght of RF signals in air ?I want to design a antenna system that locks on transmitter by a servo motor mechanism.

I need helps on this design .


Thanks a lot for your helps.

Bye

 

[adolfchen]

You shall use a horn antenna and spectrum to measore the RF signal.
Don't forget to calculate the pathloss, connector loss and cable loss.
Then you can get a rough value.

 

[flatulent]

monopulse

As far as the servo system for tracking the emitter, you can use the monopulse RADAR method. You have two horns side by side. you put the outputs through a sum and a difference network. You then compare the two signals to get the error signal for your servo loop. The difference signal contain the phase information for the direction of the servo loop.

 

[mr_ghz]

Hi 7rots51,

Create a local-oscillator in the range of about 5.6GHz (e.g. DRO oscillator). The bandpass-filtered input signal from a horn antenna and the LO signal is given to a mixer-diode (balanced, e.g. HSMS-8202). The output-signal is now in the range of 200MHz. This signal can be fed directly to a AD8307 from analog devices. This chip gives you a logarithmical output voltage corresponding to your input power. The sensitivitycan be better tahn -95dBm. You can get samples of this chip directly from analog devices.

Bye

 

[7rots51]

Is there a commercial board that do this task,I want to buy.
I want to buy a board that in one side is connected to antenna and at other side give the signal strenght information.

 

[Velund]

Oops... Never seen such things as a OEM module. Usually it is pretty expensive instruments that have some other functions as well.

Looks like you have to design it yourself or order a custom design from someone.

BTW (to gurus) - is it possible to use doppler direction finder tecniques for this stuff? As I understand, all that is necessary is direction to a transmitter, am I right? If yes, DDF will give MUCH faster result than a rotating horn antenna (but sensitivity is a question).