| Copyright | (c) Matthew Donadio 19982003 |
|---|---|
| License | GPL |
| Maintainer | m.p.donadio@ieee.org |
| Stability | experimental |
| Portability | portable |
| Safe Haskell | Safe |
| Language | Haskell98 |
DSP.Source.Oscillator
Description
NCO and NCOM functions
Synopsis
- nco :: RealFloat a => a -> a -> [a]
- ncom :: RealFloat a => a -> a -> [a] -> [a]
- quadrature_nco :: RealFloat a => a -> a -> [Complex a]
- complex_ncom :: RealFloat a => a -> a -> [Complex a] -> [Complex a]
- quadrature_ncom :: RealFloat a => a -> a -> [Complex a] -> [a]
- agc :: RealFloat a => Complex a -> Complex a
Documentation
Arguments
| :: RealFloat a | |
| => a | w |
| -> a | phi |
| -> [a] | y |
nco creates a sine wave with normalized frequency wn (numerically
controlled oscillator, or NCO) using the recurrence relation y[n] =
2cos(wn)*y[n-1] - y[n-2]. Eventually, cumulative errors will creep
into the data. This is unavoidable since performing AGC on this type
of real data is hard. The good news is that the error is small with
floating point data.
Arguments
| :: RealFloat a | |
| => a | w |
| -> a | phi |
| -> [a] | x |
| -> [a] | y |
ncom mixes (multiplies) x by a real sine wave with normalized
frequency wn. This is usually called an NCOM: Numerically Controlled
Oscillator and Modulator.
quadrature_nco returns an infinite list representing a complex phasor
with a phase step of wn radians, ie a quadrature nco with normalized
frequency wn radians/sample. Since Haskell uses lazy evaluation,
rotate will only be computed once, so this NCO uses only one sin and
one cos for the entire list, at the expense of 4 mults, 1 add, and 1
subtract per point.
complex_ncom mixes the complex input x with a quardatue nco with
normalized frequency wn radians/sample using complex multiplies
(perform a complex spectral shift)
quadrature_ncom mixes the complex input x with a quadrature nco with
normalized frequency wn radians/sample in quadrature (I/Q modulation)