Radiation Test of Switching Power Supplies in the Range of 30 MHz to 1000 MHz
When the EUT is placed on the test turntable, the radiation center of the equipment should be as close as possible to the rotation center of the turntable. The distance between EUT and measuring antenna refers to the horizontal distance between the axis of rotation and the measuring antenna.
Regarding the test turntable, if it is a turntable that is higher than the grounding plate, it should generally not be higher than 0.5m above that plane; if it is a turntable that is on the same plane as the grounding plate, the turntable plane must be a metal plane and have a good electrical connection with the grounding plate. Regardless of the type of turntable, non floor standing test specimens should be placed on the turntable at a height of 0.8m from the grounding plate. When the EUT is not placed on the turntable, the distance between the EUT and the measuring antenna refers to the near horizontal distance between the EUT boundary and the measuring antenna.
For the case where the EUT is placed on the turntable, when the measuring antenna is in both horizontal and vertical polarization states, the turntable should rotate at all angles, and the high level of its radiated disturbance should be recorded at each measurement frequency.
The requirement for the antenna in measurement is: within the frequency range of 30-80MHz, the antenna length should be equal to the resonant length of 80MHz; In the frequency range of 80-1000MHz, the antenna length should be equal to the resonant length of the measured frequency. Additionally, an appropriate transformer device should be used to match the antenna with the feed line. Also, a balanced/unbalanced converter needs to be configured to connect with the measurement receiver.
The antenna should be able to be oriented in any direction and measure its vertical polarization and horizontal polarization wave components separately. The height of the antenna center should be adjustable within 1-4m. The proximity of the antenna to the ground should not be less than 0.2m to measure its maximum value.
If the difference between the measurement results using other forms of antennas and those using balanced dipole antennas is within ± 2dB, then other forms of antennas can be used. The commonly used broadband antennas in practice are biconical antennas (30-300MHz) and logarithmic periodic antennas, while other forms of antennas can be used. The commonly used broadband antennas in practice are biconical antennas (30-300MHz) and logarithmic periodic antennas (30-1000MHz). Figure 2 shows a typical arrangement for radiation interference measurement.
