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antenna performance_how to know by a low-cost and simple way

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shanmei

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In the real application, how can we know what whether antenna receives large energy? The antenna can't connect to VNA to test its reflection in this case.

Is there any chip that can detect the antenna's efficiency? Thanks.
 

Electromagnetic noise reaches the antenna from every direction. You probably want to reject most of that energy so that you can focus on a certain frequency (or range of frequencies). Therefore it's not enough to say 'hook up a sensitive oscilloscope'.

The grid-dip meter is a simple yet useful detector for working with radio frequencies. Nowadays a jfet or transistor provides gain. You change its frequency range by attaching various combinations of coil & capacitor.
 
There is no best antenna. It is as the best rope. It depends on what your needs are.
Have never seen a radio and its antenna which not is measurable by a VNA.
With a VNA can radio TX and RX circuit impedance be measured so it can be matched against antenna impedance for optimal transferring of power in both directions.
An assumed high efficiency antenna can be rather useless if not matched against actual radio impedance.

Assuming impedance matching not is a problem can comparing different antenna radiation pattern be done.
Assume a fixed transmitter at distance.
Most radio chips can read received signal level, RSSI.
Comparing different antennas, all equal well matched to actual radio, can be done by reading RSSI-value for each antenna.
Result will show which antenna that works best for actual local environment and resulting directivity pattern.

There exist a lot of single chip RF receivers and RF detectors or even simple diode detectors connected to a simple voltmeter which can be used to measure amount of power received by an antenna, when it is impedance matched to actual measurement circuit.
It will not tell if result will be same when connected to another receiver then what is used for measurement, as well as if connected to another antenna.
Especially when antenna and ground are much less in size then actual wave-length or with antenna placed internal in an enclosure, can even minor changes in antenna near field have big impact on antenna received signal level and usable bandwidth. Antenna that performed good in free space can behave very poor in a limited space.
 
Antennas have different gain, directional characteristic, impedance and frequency range. Asking only for performance or "received energy" doesn't fully specify your performance metric. It's a big difference if you want maximal power delivered to a fixed load impedance or you have a tunable load.

Also the statement "antenna can't connect to VNA" needs explanation. The most sensible interpretation I can think of is a small mobile antenna that can't be easily connected to a VNA without disturbing the antenna parameters. Firstly I would ask if there aren't options to make useful VNA measurements in such cases. Secondly I would e.g. consider a small battery powered transmitter "chip" to measure the antenna performance.

In any case, please elaborate the question.
 
I use very simple and cheap way of measuring: replacing antenna in commercial devices by my own prototype antenna designs and comparing output from device mixer (amplitude/noises/etc.) Easy to perform if antenna is fed by waveguide / slot or similar transition. Unfortunately it is not always possible to perform.
 
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