Discrete-time, second-order section, direct-form I transposed filter
Hd = dfilt.df1tsos(s) returns a discrete-time, second-order section, direct-form I, transposed filter, Hd, with coefficients given in the s matrix. The filter states for this object are stored in a filtstates object.
Hd = dfilt.df1tsos(b1,a1,b2,a2,...) returns a discrete-time, second-order section, direct-form I, tranposed filter, Hd, with coefficients for the first section given in the b1 and a1 vectors, for the second section given in the b2 and a2 vectors, etc.
Hd = dfilt.df1tsos(...,g) includes a gain vector g. The elements of g are the gains for each section. The maximum length of g is the number of sections plus one. If g is not specified, all gains default to one.
To display the filter states, use this code to access the filtstates object.
Hs = Hd.states % Where Hd is the dfilt.df1 object and double (Hs) % Hs is the filtstates object
The matrix is
Specify a second-order sections, direct-form I, transposed discrete-time filter with coefficients from a sixth order, lowpass, elliptical filter using the following code:
[z,p,k] = ellip(6,1,60,.4); % Obtain filter coefficients [s,g] = zp2sos(z,p,k); % Convert to SOS Hd = dfilt.df1tsos(s,g)