When measuring radiation inside the shield box....

[moon.kim]

Hi,

In order to measure the RF power, I measured the RF power by radiating inside the RF shield box.

But there is something strange.

The position between the device's antenna and the measurement antenna (an antenna connected to the spectrum) was kept constant.

However, the measured value changed depending on where in the shield box the test was conducted.

Please refer to the picture below:

Since the device I developed cannot measure the output power in a conducted, I measure it in radiation.

Perhaps it is due to the frequency reflected from the inside.

Is there any way to solve this problem???

[Andreas]

Hi,

 

As Awneil kindly mentions, a shielded box is not necessarily anechoic, especially in the 'box size'. The position of the device and the antenna will change how much is reflected and transmitter within the box and possibly detune the antennas if placed close to the walls.

 

Best regards,

Andreas

[moon.kim]

Hi, Andreas

Sorry. I can't understand Awneil and your advice.

First, The shield box I use is not anechoic.

Does this mean that it is okay if there is a distance of 12.5cm or more from the shield box wall?

awneil said:

Remember: at 2.4GHz, the wavelength is only 12.5cm ...

And you say....

Andreas said:

The position of the device and the antenna will change how much is reflected and transmitter within the box and possibly detune the antennas if placed close to the walls.

You mean it should be placed like this?

[Andreas]

Hi,

 

It's hard to recommend anything without knowing what your goal is, what are you trying to do? 

 

The walls will reflect the radio signals, exact how they reflect and how the signals have to propagate to get to the spectrum analyzer antenna depends on the position of the device and the antenna. Typically I would place the device and antenna not this close to the walls, but as long as you place them similarly for each measurement you should get consistent results.

 

Best regards,

Andreas

[awneil]

moon.kim said:

I can't understand Awneil and your advice

Sounds like you really need to get someone who knows how to do RF measurements to help you with this.

RF work is a specialist area!

[moon.kim]

HI.

Thank you.

I wanted to know how to place the antenna in the shield box so that it is less affected by reflected waves.

Because, Output power was measured low on certain frequency channels depending on device location.

This is because you have to measure a lot of devices and get a uniform result for comparison.

Any way, I guess it's important to keep the antenna and device position constant at all times.

[Andreas]

Hi,

 

 

moon.kim said:

Any way, I guess it's important to keep the antenna and device position constant at all times.

 Exactly. This is an inaccurate way of measuring output power, but if you are able to compare with a golden device it should work ok. This requires that the devices are placed identically each time.

 

Best regards,

Andreas