IEC 61726-2015 pdf free download.Cable assemblies, cables, connectors and passive microwave components – Screening attenuation measurement by the reverberation chamber method.
When deciding on a measurement procedure, it shall be recognized that:
— discrete tuning is slow and requires a large number of sample measurements to be taken per revolution of the mode stirrer (200 is a usual value up to 20 GHz). This does, however. result in the acquisition of more accurate measurements:
— averaged power calculation during one revolution of the mode stirrer dramatically decreases the dynamic range of the method. In this case. acquisitions shall be recorded in watts (W) and not in dBm.
The measurement procedure described here is very economical in time, but requires a modern and stable spectrum analyser.
7.2 Measurement of the DUT
7.2.1 General
Depending on the available measurement instruments and the need on dynamic range. there are two possibilities on measurement.
7.2.2 Standard measurement
The standard measurement offers a high dynamic range. especially if power controlled amplifiers are used at the output of the generator.
The synthesized generator is connected to the input antenna and set to deliver a constant power at a fixed frequency. The mode stirrer is set to rotate at a constant speed (for example. 1 revolution every 5 s).
The spectrum analyser is connected to the output of the device under test. Its resolution filter is centred on the emitting frequency of the synthesizer and is fixed (SPAN 0: demodulator mode).
The spot scans the screen during a period which is equal to the time of one revolution of the mode stirrer.
The resulting trace which appears on the screen shows the evolution of the power as a function of the angular position of the mode stirrer.
After one complete revolution of the mode stirrer, the maximum value of the power s recorded,
Screening attenuation is then calculated, taking into account the attenuation of links and insertion loss of the cavity (equation (3)).
The same procedure is repeated for all the required test frequencies.
7.2.3 Fast measurement
For a faster measurement, a spectrum analyser with synchronized tracking generator is used [5J. The resolution bandwidth is set according to the requirements on dynamic range. Furthermore, the maximum hold function has to be used.
To calibrate the chamber set up and to determine the insertion loss, a first measurement is performed in which the spectrum analyser input is connected to the reference antenna and the tracking generator output is connected to the input antenna. The mode stirrer is turning continuously with e.g. 1 revolution every 5 s. The analyser needs to be set into a continuous sweep mode with max hold function.IEC 61726 pdf download.