How to measure the frequency width?

- Jun 04, 2018 -

How to measure the frequency bandwidth?

Combined with the spectrum analyzer software structure, in the test of occupied bandwidth, the parameters that need to be considered include: frequency, bandwidth, resolution bandwidth, video bandwidth, detection mode, number of points, percentage of occupied power, and x dB. Since the measured transmitter signal is usually noise-like, the video bandwidth should be set to more than 10 times the resolution bandwidth during the test. The detection mode is set to sample or rms detection.

According to the test requirements of the occupied bandwidth measurement, the function points implemented in the function design process mainly include the measurement of the occupied bandwidth and the measurement of the xdB bandwidth.

Occupied bandwidth

According to ITU regulations, occupied bandwidth refers to a bandwidth in which the average power transmitted under its lower frequency limit and above the frequency upper limit is equal to the specified percentage of the total average power of a given transmission.

Normally, β/2 is 0.5%, and the user can also set the desired value. In the calculation, the power P(f) is integrated along the entire bandwidth along the frequency, and the total power ΣP in the entire bandwidth can be obtained, that is, the total power is the area under the P(f) curve; then the total power is obtained. For two frequency points of 0.5% and 99.5%, then the width between these two frequency points concentrates the occupied bandwidth value of 99% of the total power.

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