Interference Rejection - Kenwood TS-890S In-Depth Manual

07 DSP

Interference Rejection

Interference signals such as pulse noise and beats may affect the IF-AGC and suppress the desired signals. In such
cases, eliminating the interference signals in the preceding stage to the AGC can highlight the signal behind the
interference signals.
Similar to the IF filter, interference rejection is a function that is placed before in-band AGC to eliminate specific
interference signals. Two types of interference rejection via digital signal processing are available on the TS-890S: noise
blanker and notch filter.
● Noise Blankers
The TS-890S has two noise blankers, NB1 and NB2. NB1 is the noise blanker for the analog circuit. NB2 is the noise
blanker for digital signal processing. NB2 offers two modes, Type A and Type B, which can be employed for different
situations. It is also possible to combine the use of NB1 and NB2.
NB2 Type A monitors the envelope of RX signals and performs blanking on the pulse noise when there are changes in
the signal level beyond a certain level.
NB2 Type B is a new blanking technique that is based on the IF-AGC technology to enhance the accuracy of pulse noise
detection. it allows blanking even when there is only a slight signal level difference between the desired signal and pulse
noise signal. The diagram below shows how an audio signal suppressed by the IF-AGC operation can be highlighted
when the pulse noise is eliminated by NB2 Type A or Type B.
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Time (s)
Time (s)
Fig. 39 Effect of NB2 Type A
Time (s)
Time (s)
Fig. 40 Effect of NB2 Type B