Reference level: The maximum power value input from the DUT to the instrument. When the input power is greater than this value, the power result may be inaccurate.

Trigger level: The trigger level is the relative value of the reference level based on the reference level. The actual trigger power value is the sum of the reference level and the trigger level.

The reference level value in the figure below is the upper thin line value of 2.01dBm, the trigger level value is -31dBmax (shown in the red box in the figure below), and the trigger power value is the lower thin line value: 2.01-31=-28.99dBm. The WT instrument samples the rising edge level trigger. If the power of the input signal exceeds the trigger power and the noise floor is lower than the trigger power, the signal can be triggered normally.

Channel (Channel): Channel is a further division of frequency bands (the 5G or 2.4G frequency range is subdivided into several small frequency bands, and each frequency band is called a Channel). Data on different transmission channels will not interfere with each other if the channel coverage does not overlap. For example, the picture below: 2.4G is divided into 14 Channels

The relationship between Channel and Trigger: Take DUT transmission: 802.11ac, Bandwidth: 80M, Channel: 42, Power: -10dBm, Trigger level -31dBm as an example.

1: Trigger level value remains unchanged, Channel: 58. At this time, the offset is correct center frequency, but it does not exceed the 120MHz bandwidth, so you can see part of the spectrum and frame power.

2: Trigger level value remains unchanged, Channel: 106. At this time, the center frequency with the correct offset exceeds the 120MHz bandwidth. The trigger is successful, but there is only a power map with the noise floor at this time