[FieldTrip] Calculating PAC meets question about narrow band filtering

[赫雨欣]

Hello fieldtripers: 
When I calculated Phase – Amplitude – Coupling, I chose 3-8Hz as phase frequency. And codes for filtering are:
        cfg = [];
        cfg.showcallinfo = 'no';
        cfg.bpfilter = 'yes';
        cfg.bpfreq = [phase_freq-1 phase_freq+1]; 
        cfg.hilbert = 'angle';
        [virtsens_phase] = ft_preprocessing(cfg, virtsens_p);

But, there is an error:
　‘Calculated filter coefficients have poles on or outside the unit circle and will not be stable. Try a higher cutoff frequency or a
　different type/order of filter.’
　
I don’t know how to change my codes. I’m very appreciate that if anybody can help me here.

Best regards,
Emily
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