Loop bandwidths (symsync) in what units? #343
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Hello, |
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Good question! All bandwidths are normalized to the sample rate. So, for example, if you are designing a low-pass filter with a normalized cut-off frequency 0.25, this would result in a filter with a pass-band from -0.25 Fs to +0.25 Fs (where Fs is the sampling frequency). The symsync object tries to respect this, but its fusing symbol timing and carrier frequency/phase offset recovery loops. Unfortunately, the tracking performance of this is heavily dependent upon the input data (namely the modulation scheme and the excess bandwidth factor of the matched filter). In general, though, if you want to have the signal "settle" after e.g. 1,000 symbols, you would set your loop filter bandwidth to be on the order of 0.001. |
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Good question! All bandwidths are normalized to the sample rate. So, for example, if you are designing a low-pass filter with a normalized cut-off frequency 0.25, this would result in a filter with a pass-band from -0.25 Fs to +0.25 Fs (where Fs is the sampling frequency).
The symsync object tries to respect this, but its fusing symbol timing and carrier frequency/phase offset recovery loops. Unfortunately, the tracking performance of this is heavily dependent upon the input data (namely the modulation scheme and the excess bandwidth factor of the matched filter). In general, though, if you want to have the signal "settle" after e.g. 1,000 symbols, you would set your loop filter bandwidth…