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##

Function: `sp_filters()`

0
`void sp_filters(float m1, float m2, float *ch1, float *ch2,
float fstart, int n, float srate, float f_c, float t_c,
int order)
`

This function generates stationary phase approximations to
binary inspiral chirp waveforms.
Its input and output are similar to `make_filters()`.
The difference is that the chirps are generated in the frequency domain
using the stationary phase approximation.

The arguments are:

`m1`: Input. The mass of body-1 in solar masses.
`m2`: Input. The mass of body-2 in solar masses.
`ch1`: Output. Upon return, `ch1[0..n-1]` contains
the stationary phase approximation to
[Eq. ()]
in the same format as would be returned by a
`realft()` of a time-domain function sampled at rate `srate`.
That is, except for DC and Nyquist frequencies,
`ch1[2*i]` and `ch1[2*i+1]` contain respectively
the real and imaginary parts of
for
.
This function sets `ch1[0]` (DC) and `ch1[1]` (Nyquist) to zero.
The chirp is also set to zero for
and for
(see section for ).
The output `ch1[0..n-1]` has dimensions of 1/Hz.
`ch2`: Output. Upon return, `ch2[]` contains
in the same way that `ch1[]` contains
.
`fstart`: Input. The starting gravitational-wave frequency of the
chirp in Hz. Note: this is twice the orbital frequency!
`n:` Input. The length of the arrays `ch1[0..n-1]` and
`ch2[0..n-1]`.
`srate`: Input. The sample rate, in Hz.
`f_c`: Input. The coalescence frequency , as described in
section . This is the high-frequency cutoff of the
chirps.
`t_c:` Input. The coalescence time, in seconds. Note this is the
time of the *end* of the chirp (see section ).
`order`: Input.
Order of generated chirps in
(twice the post-Newtonian order).

This function assumes that you have already allocated storage for
the chirps.

- Author:
Benjamin Owen, owen@tapir.caltech.edu
- Comments: The
`sp_filters()` function doesn't include
spins yet. It will be simple to add higher-order post-Newtonian
phase terms as they appear in the literature.

** Next:** Example: compare_chirps program
** Up:** GRASP Routines: Gravitational Radiation
** Previous:** Stationary phase approximation to
** Contents**
Bruce Allen
2000-11-19