mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-17 09:31:59 -05:00
8cf40e587a
by spec in the GUI thread. Don't use "zero" in spec. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/trunk@130 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
185 lines
5.1 KiB
Fortran
185 lines
5.1 KiB
Fortran
SUBROUTINE xfft2(DATA,NB)
|
|
c
|
|
c the cooley-tukey fast fourier transform in usasi basic fortran
|
|
c
|
|
C .. Scalar Arguments ..
|
|
INTEGER NB
|
|
C ..
|
|
C .. Array Arguments ..
|
|
REAL DATA(NB+2)
|
|
C ..
|
|
C .. Local Scalars ..
|
|
REAL DIFI,DIFR,RTHLF,SUMI,SUMR,T2I,T2R,T3I,T3R,T4I,
|
|
+ T4R,TEMPI,TEMPR,THETA,TWOPI,U1I,U1R,U2I,U2R,U3I,U3R,
|
|
+ U4I,U4R,W2I,W2R,W3I,W3R,WI,WR,WSTPI,WSTPR
|
|
INTEGER I,I2,IPAR,J,K1,K2,K3,K4,KDIF,KMIN,
|
|
+ KSTEP,L,LMAX,M,MMAX,NH
|
|
C ..
|
|
C .. Intrinsic Functions ..
|
|
INTRINSIC COS,MAX0,REAL,SIN
|
|
C ..
|
|
C .. Data statements ..
|
|
DATA TWOPI/6.2831853071796/,RTHLF/0.70710678118655/
|
|
c
|
|
c 1. real transform for the 1st dimension, n even. method--
|
|
c transform a complex array of length n/2 whose real parts
|
|
c are the even numbered real values and whose imaginary parts
|
|
c are the odd numbered real values. separate and supply
|
|
c the second half by conjugate symmetry.
|
|
c
|
|
|
|
NH = NB/2
|
|
c
|
|
c shuffle data by bit reversal, since n=2**k.
|
|
c
|
|
J = 1
|
|
DO 131 I2 = 1,NB,2
|
|
IF (J-I2) 124,127,127
|
|
124 TEMPR = DATA(I2)
|
|
TEMPI = DATA(I2+1)
|
|
DATA(I2) = DATA(J)
|
|
DATA(I2+1) = DATA(J+1)
|
|
DATA(J) = TEMPR
|
|
DATA(J+1) = TEMPI
|
|
127 M = NH
|
|
128 IF (J-M) 130,130,129
|
|
129 J = J - M
|
|
M = M/2
|
|
IF (M-2) 130,128,128
|
|
130 J = J + M
|
|
131 CONTINUE
|
|
|
|
c
|
|
c main loop for factors of two. perform fourier transforms of
|
|
c length four, with one of length two if needed. the twiddle factor
|
|
c w=exp(-2*pi*sqrt(-1)*m/(4*mmax)). check for w=-sqrt(-1)
|
|
c and repeat for w=w*(1-sqrt(-1))/sqrt(2).
|
|
c
|
|
IF (NB-2) 174,174,143
|
|
143 IPAR = NH
|
|
144 IF (IPAR-2) 149,146,145
|
|
145 IPAR = IPAR/4
|
|
GO TO 144
|
|
|
|
146 DO 147 K1 = 1,NB,4
|
|
K2 = K1 + 2
|
|
TEMPR = DATA(K2)
|
|
TEMPI = DATA(K2+1)
|
|
DATA(K2) = DATA(K1) - TEMPR
|
|
DATA(K2+1) = DATA(K1+1) - TEMPI
|
|
DATA(K1) = DATA(K1) + TEMPR
|
|
DATA(K1+1) = DATA(K1+1) + TEMPI
|
|
147 CONTINUE
|
|
149 MMAX = 2
|
|
150 IF (MMAX-NH) 151,174,174
|
|
151 LMAX = MAX0(4,MMAX/2)
|
|
DO 173 L = 2,LMAX,4
|
|
M = L
|
|
IF (MMAX-2) 156,156,152
|
|
152 THETA = -TWOPI*REAL(L)/REAL(4*MMAX)
|
|
WR = COS(THETA)
|
|
WI = SIN(THETA)
|
|
155 W2R = WR*WR - WI*WI
|
|
W2I = 2.*WR*WI
|
|
W3R = W2R*WR - W2I*WI
|
|
W3I = W2R*WI + W2I*WR
|
|
156 KMIN = 1 + IPAR*M
|
|
IF (MMAX-2) 157,157,158
|
|
157 KMIN = 1
|
|
158 KDIF = IPAR*MMAX
|
|
159 KSTEP = 4*KDIF
|
|
IF (KSTEP-NB) 160,160,169
|
|
160 DO 168 K1 = KMIN,NB,KSTEP
|
|
K2 = K1 + KDIF
|
|
K3 = K2 + KDIF
|
|
K4 = K3 + KDIF
|
|
IF (MMAX-2) 161,161,164
|
|
161 U1R = DATA(K1) + DATA(K2)
|
|
U1I = DATA(K1+1) + DATA(K2+1)
|
|
U2R = DATA(K3) + DATA(K4)
|
|
U2I = DATA(K3+1) + DATA(K4+1)
|
|
U3R = DATA(K1) - DATA(K2)
|
|
U3I = DATA(K1+1) - DATA(K2+1)
|
|
U4R = DATA(K3+1) - DATA(K4+1)
|
|
U4I = DATA(K4) - DATA(K3)
|
|
GO TO 167
|
|
|
|
164 T2R = W2R*DATA(K2) - W2I*DATA(K2+1)
|
|
T2I = W2R*DATA(K2+1) + W2I*DATA(K2)
|
|
T3R = WR*DATA(K3) - WI*DATA(K3+1)
|
|
T3I = WR*DATA(K3+1) + WI*DATA(K3)
|
|
T4R = W3R*DATA(K4) - W3I*DATA(K4+1)
|
|
T4I = W3R*DATA(K4+1) + W3I*DATA(K4)
|
|
U1R = DATA(K1) + T2R
|
|
U1I = DATA(K1+1) + T2I
|
|
U2R = T3R + T4R
|
|
U2I = T3I + T4I
|
|
U3R = DATA(K1) - T2R
|
|
U3I = DATA(K1+1) - T2I
|
|
U4R = T3I - T4I
|
|
U4I = T4R - T3R
|
|
|
|
167 DATA(K1) = U1R + U2R
|
|
DATA(K1+1) = U1I + U2I
|
|
DATA(K2) = U3R + U4R
|
|
DATA(K2+1) = U3I + U4I
|
|
DATA(K3) = U1R - U2R
|
|
DATA(K3+1) = U1I - U2I
|
|
DATA(K4) = U3R - U4R
|
|
DATA(K4+1) = U3I - U4I
|
|
168 CONTINUE
|
|
KDIF = KSTEP
|
|
KMIN = 4*KMIN - 3
|
|
GO TO 159
|
|
|
|
169 M = M + LMAX
|
|
IF (M-MMAX) 170,170,173
|
|
170 TEMPR = WR
|
|
WR = (WR+WI)*RTHLF
|
|
WI = (WI-TEMPR)*RTHLF
|
|
GO TO 155
|
|
|
|
173 CONTINUE
|
|
IPAR = 3 - IPAR
|
|
MMAX = MMAX + MMAX
|
|
GO TO 150
|
|
c
|
|
c complete a real transform in the 1st dimension, n even, by con-
|
|
c jugate symmetries.
|
|
c
|
|
174 THETA = -TWOPI/REAL(NB)
|
|
WSTPR = COS(THETA)
|
|
WSTPI = SIN(THETA)
|
|
WR = WSTPR
|
|
WI = WSTPI
|
|
I = 3
|
|
J = NB - 1
|
|
GO TO 207
|
|
|
|
205 SUMR = (DATA(I)+DATA(J))/2.
|
|
SUMI = (DATA(I+1)+DATA(J+1))/2.
|
|
DIFR = (DATA(I)-DATA(J))/2.
|
|
DIFI = (DATA(I+1)-DATA(J+1))/2.
|
|
TEMPR = WR*SUMI + WI*DIFR
|
|
TEMPI = WI*SUMI - WR*DIFR
|
|
DATA(I) = SUMR + TEMPR
|
|
DATA(I+1) = DIFI + TEMPI
|
|
DATA(J) = SUMR - TEMPR
|
|
DATA(J+1) = -DIFI + TEMPI
|
|
I = I + 2
|
|
J = J - 2
|
|
TEMPR = WR
|
|
WR = WR*WSTPR - WI*WSTPI
|
|
WI = TEMPR*WSTPI + WI*WSTPR
|
|
207 IF (I-J) 205,208,211
|
|
208 DATA(I+1) = -DATA(I+1)
|
|
|
|
211 DATA(NB+1) = DATA(1) - DATA(2)
|
|
DATA(NB+2) = 0.
|
|
|
|
DATA(1) = DATA(1) + DATA(2)
|
|
DATA(2) = 0.
|
|
|
|
RETURN
|
|
END
|