50
Video Filter
Figure 36 Video Filter Settings, 300 kHz Signal
Except for average power and VSWR measurements, all WPS measurements rely
on a variable video filter to improve accuracy. This filter can be set to either 4.5
kHz, 400 kHz, or full bandwidth (10000kHz). It should be as narrow as possible
while still being larger than the demodulated signal bandwidth (video
bandwidth). Narrowing the filter limits the noise contribution caused by
interfering signals. Listed below are some common modulation schemes and the
appropriate video filter.
Video Filter
Modulation Type
4.5 kHz
CW Burst (Burst width > 150 μs), Voice Band
AM, FM, Phase Modulation, Tetra
400 kHz
CW Burst (b.w. > 3 μs), GSM, 50 kHz AM, DQPSK
Full Bandwidth 10000kHz
CW Burst (b.w. > 200 ns), CDMA, WCDMA,
DQPSK, DAB/DVB-T
Filter
Too Small
Filter
Too Wide
Correct
Filter
Noise
Signal
