Campbell 21X Manuel de l'opérateur télécharger pdf (Page 114)

01:

02:

amount of

at the different

frequencies but

do not

any

phase

information.

originaltime

varying signalcan

be

by

taking the Inverse

Fourier

magnitude ahd

phase

results.

PROGRAMMING

The

FFT

Instruction

is

a Processing

Instruction

and will

not

dutput

data to final

memory or any

data

storage

device.

FFT results

are transferred

to Final Meniory

by setting the Output

Flag

and

sampling thQ

input

locations which contain the

FFT results.

Referring

to

Table 5,

the thirteenth

through the

$eventeenth

instructions

illustrate

one method

bf

transferring the

data from input

memory to

fifial

memory.

PAR.

DATA

NO.

TYPE

DESCRIPTION

Log base 2 of

N, where N is the

number

of samples

in

the original

data;

e.9.,

this

parameter

is 11

for

2048

samples

or

12 for 4096

samples.

Maximum

is 13

or 8192.

FFT Option

X0

=

No

Taper

0X

=

Power

Spectra

1X

=

Pss;

g

X1

=Taper

lmaginary

2X=Yag6ilude&Phase

Log base 2 of the

number

of

adjacent bins

to average; e.9., this

parameter

is 3

for averaging 8

adjacent bins.

Input location containing the

first

value in the originaltime

series.

After

this

program

has executed,

this

location will contain the first

spectral

bin or

bin average of the

result.

Multiplier for scaling

FFT results.

Input

storage

locations: Greater

than or equal

to the

number of

values in the

original

time

series

data.

lntermediate storage

locations:

2 +

(.125.

N)

SECTION 10.

PROCESSING

INSTRUCTIONS

Execution

time

in seconds:

REAL

AND IMAGINARY

=

.00065*N*LOG2 of

N +

.58

MAGNITUDE

AND

PHASE

=

.00077*N*LOG2

of

N + 1.66

POWER

SPECTRA

=.00066*N*LOG2

of N

+ .45

PARAMETER 1

is

an integerfrom

1 to 13. The

number 2, raised

to the

power

of

Parameter

1, is

equal

to

the

number of

data

values

in the

originaltime

series data, N.

For example,

if

Parameter

1=13, then N=8192.

Maximum value

for Parameter

1 is 13

(8192).

PARAMETER 2, the

FFT

Option,

is a two digit

parameter.

The

first

digit specifies

which

results

are

to be

generated

and

the second

digit

specifies

whether or not a

"taper" is applied.

First

Digit: A

"0" in the

first

digit specifies that

the FFT result be

expressed as the

power

spectra.

Bin averaging is allowed

with this

option. A

"1"

in the

f irst

digit

specifies

that the

FFT result be expressed as the

real and

imaginary

components.

Bin averaging

is

not

allowed

with

this

option. A "2"

in

the

first

digit

specifies that the

FFT

result be

expressed as

the magnitude and

phase

components.

Bin

averaging is not allowed

with this option.

Second Digit: A

"0" in

the second

digit specifies

that no taper

be applied, whereas a

"1"

specifies

that

a taper

be applied. lf the

original data set

is

not known to be

periodic

with an integral number

of

periods

in

the

data

set,

then

it is necessary to

apply a taper

to the beginning and end

of

the

data. The taper

that is

applied

is

a

four

term

Blackman-Harris as

specified

by

Fredric

J.

Harris, Proceedings of the

IEEE,

Vol. 66,

No.

1,

January 1978. When the taper

is used,

the

21X

applies a correction by

multiplying

the

results

by

the ratio of the

variance

before

the

taper

to

the

variance

after

the taper.

The

variance

ratio

is

saved

only

when

the

power

spectra option

is selected. The

variance ratio is

saved in input location

(N/2)+B,

where B is the

location

(Parameter

4) that contained

the first

value

of the original time

series data.

PARAMETER 3 specifies

how many of the

resulting spectral

bins

(if

any) are to

be

averaged.

Bin averaging

is

only

allowed when

FP

03:

04:

05:

10-7

1 2 ... 109 110 111 112 113 114 115 116 117 118 119 ... 190 191

Commentaires sur ces manuels

Pas de commentaire