Depending on the chosen window and mode, the magnitude of the
impulse response in time-domain previously was to low. This can
be explained by looking at the signal processing. For example,
in bandpass mode with normal window, it applies a 101 point Kaiser
window (shape factor 6) and zero-pads to do a 256 point IFFT.
Therefore, the loss is 20*log10(256/sum(kaiser(101,6))) ≈ 14.2 dB.
This change compensates the signal processing losses in bandpass
and lowpass impulse mode depending on the window type, which makes
the time-domain results similar to other VNAs.
Depending on the chosen window and mode, the magnitude of the impulse response in time-domain previously was to low. This can be explained by looking at the signal processing. For example, in bandpass mode with normal window, it applies a 101 point Kaiser window (shape factor 6) and zero-pads to do a 256 point IFFT. Therefore, the loss is 20*log10(256/sum(kaiser(101,6))) ≈ 14.2 dB.
This change compensates the signal processing losses in bandpass and lowpass impulse mode depending on the window type, which makes the time-domain results similar to other VNAs.
See this thread for examples and discussion: https://groups.io/g/nanovna-users/topic/should_the_builtin_tdr_mode/77043091