Communications Toolbox

rcosine

Design a raised cosine filter

Syntax

• num = rcosine(Fd,Fs);
  [num,den] = rcosine(Fd,Fs,type_flag);
  [num,den] = rcosine(Fd,Fs,type_flag,r);
  [num,den] = rcosine(Fd,Fs,type_flag,r,delay);
  [num,den] = rcosine(Fd,Fs,type_flag,r,delay,tol);
  

Description

num = rcosine(Fd,Fs) designs a finite impulse response (FIR) raised cosine filter and returns its transfer function. The digital input signal has sampling frequency Fd. The sampling frequency for the filter is Fs. The ratio Fs/Fd must be a positive integer greater than 1. The default rolloff factor is .5. The filter's group delay, which is the time between the input to the filter and the filter's peak response, is three input samples. Equivalently, the group delay is 3/Fd seconds.

[num,den] = rcosine(Fd,Fs,type_flag) designs a raised cosine filter using directions in the string variable type_flag. Filter types are listed in the table below, along with the corresponding values of type_flag.

Types of Filter and Corresponding Values of type_flag

Type of Filter	Value of type_flag
Finite impulse response (FIR)	'default' or 'fir/normal'
Infinite impulse response (IIR)	'iir' or 'iir/normal'
Square-root raised cosine FIR	'sqrt' or 'fir/sqrt'
Square-root raised cosine IIR	'iir/sqrt'

The default tolerance value in IIR filter design is 0.01.

[num,den] = rcosine(Fd,Fs,type_flag,r) specifies the rolloff factor, r. The rolloff factor is a real number in the range [0, 1].

[num,den] = rcosine(Fd,Fs,type_flag,r,delay) specifies the filter's group delay, measured in input samples. delay is a positive integer. The actual group delay in the filter design is delay/Fd seconds.

[num,den] = rcosine(Fd,Fs,type_flag,r,delay,tol) specifies the tolerance in the IIR filter design. FIR filter design does not use tol.

See Also

rcosflt, rcosiir, rcosfir, rcosdemo, grpdelay

References

Korn, Israel, Digital Communications, New York, Van Nostrand Reinhold, 1985.

rcosiir

rsdec