If Filter - Kenwood TS-990S In-Depth Manual

IF Filter

As the main band limitation filter, the TS‑990S is equipped with roofing filters for the analog stage and the digital IF filter
and AF filter in the DSPs. (In addition to these, the audio peak filter, etc. are also implemented.)
Concerning the filters, the IF filter is placed before the in‑band AGC and the AF filter is placed after the in‑band AGC. In
AM mode, the AF filter is placed in the circuit after demodulation. In FM mode, a demodulation IC is used, thus only AF
filtering is handled in the DSP.
There are three types of filters available, and, with the front panel operation, the filters jointly work and switch to low‑cut,
high‑cut, or the passband width. Only the bands of the roofing filters for the main band can be changed independently
following the configuration.
The IF filter in the DSP constructs the slope tuning in combination with the IIR low‑pass filter and high‑pass filter in SSB
mode, and constructs the function that can adjust the passband width (Width) and the amount of the center frequency
shift (Shift) with bandpass filters for IIR in CW, FSK, and PSK modes. Only in SSB mode, the function to adjust "Width"
and "Shift" can be applied following the configuration, instead of the slope tuning.
In AM mode, the filter constructs the FIR bandpass filter enabling to switch the bandwidth of the bandpass filter upon
adjustment of the high‑cutoff frequency.
SSB IF Filter (Slope Tune\ Medium)
Fig. 59 SSB Slope Tuning (Combination
of the Low‑cut and High‑cut Filters, Filter Shape: "Medium")
Fig. 58 Comparison of Received CW Waveforms of
a Conventional Transceiver to those of the TS‑990S
Frequency (Hz)
KENWOOD Existing Model
Time (S)
TS-990S
Time (S)
(Bandpass Filter, Filter Shape: "Medium")
CW IF Filter (Width/Medium)
Frequency (Hz)
CW Passband Width
DSP 06
35