two examples to show fft/ifft vector command

examples/various/FFT_Leakage.cir

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+FFT_Leakage_tests http://www.idea2ic.com/
+*=========Create_Signal==================
+VTime     VTime  0      DC     0      PWL(   0      0    1      1)
+Vfreq     Vfreq  0      DC     5.5k
+BVAC      IN     0      V  =   sin( 6.283185307179586*V(VFreq)*V(VTime))
+.control
+*TRAN     TSTEP  TSTOP  TSTART TMAX   ?UIC?
+tran      1u     .999m  0       1u
+set       pensize = 2
+linearize
+let       numb2 = length(in)
+print     numb2
+
+*=========Do_FFT_and_Plot_As_dB_Freq==================
+let       ac = in +j(0)
+let       ac_fft=fft(ac)
+let       numb_f2 =  (numb2)/2 -1
+compose   freq   start = 1 stop = $&numb_f2  step =1
+compose   vreal  start = 1 stop = $&numb_f2  step =1
+compose   vimag  start = 1 stop = $&numb_f2  step =1
+let       j = 0
+repeat    $&numb_f2
+let       freq[j] =  freq[j]
+let       vreal[j] = 2*real(ac_fft[j+1])
+let       vimag[j] = 2*imag(ac_fft[j+1])
+let       j = j +1
+end
+plot      dB(abs(vreal+1f)) dB(abs(vimag+1f)) vs freq xlog
+
+*=========Extract_Error_Signal=========================
+let       funBin                 = 5k/1000
+let       unvect                 = unitvec(numb2)
+let       fundspec               = unvect*0 +j(0)
+let       fundspec[funBin]       = real(ac_fft[funBin])        +j(imag(ac_fft[funBin] ))
+let       fundspec[numb2-funBin] = real(ac_fft[numb2-funBin])  +j(imag(ac_fft[numb2-funBin] ))
+let       fund                   = ifft(fundspec)
+let       dc_ofset               = real(ac_fft[0])
+let       thdspec                = ac_fft
+let       thdspec[0]             = 0        +j(0)
+let       thdspec[funBin]        = 0        +j(0)
+let       thdspec[numb2-funBin]  = 0        +j(0)
+let       thd                    = ifft(thdspec)
+plot      norm(in) norm(fund) norm(thd)/2
+
+*=========Calc_Values=========================
+let       rms_Fund               = sqrt(mean(fund*fund))
+let       rms_THD                = sqrt(mean(thd*thd))
+let       THD_percent            = 100*rms_THD/rms_Fund
+let       FREQ_Hz                = VFreq[0]
+echo      "Freq_Hz=$&FREQ_Hz THD_percent=$&THD_percent Fund_rms=$&rms_Fund THD_rms=$&rms_THD "
+
+.endc
+.end

examples/various/FFT_tests.cir

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+FFT_tests http://www.idea2ic.com/
+.control
+set units=degrees
+let a = vector(16)
+*plot a vs a
+set pensize = 2
+*=========Need_a_complex_input====================
+let ac = a+j(0)
+print a ac
+*plot fft(a) vs a
+*plot real(fft(ac)) imag(fft(ac)) vs a
+* fft(a) fft(ac)
+
+*=========DC_Works====================
+let b = unitvec(16)
+let bc = b+j(0)
+*plot fft(b) vs a                             title DC_WORKS
+*print fft(b) fft(bc)
+
+*=========DC_Plus_cos_Remove_AC====================
+let     numb = length(b)
+print   numb
+
+let     indx = 0
+repeat  $&numb
+let     ac[indx]= cos(indx*360/8)+1 +j(0)
+let     indx = indx +1
+end
+
+let     fftac=fft(ac)
+plot    real(fftac)          imag(fftac)  vs a   title DC_Plus_COS
+
+let     fftac[2]=(0,0)
+let     fftac[14]=(0,0)
+let     ifftac = ifft(fftac)
+plot    ifftac ac vs a                        title COS_REMOVED
+
+*=========DC_Plus_cos_Remove_DC====================
+let     indx = 0
+repeat  $&numb
+let     ac[indx]= cos(indx*360/8)+1 +j(0)
+let     indx = indx +1
+end
+
+let     fftac=fft(ac)
+let     fftac[0]=(0,0)
+let     ifftac = ifft(fftac)
+plot    ifftac ac  vs a                       title COS_With_DC_REMOVED
+
+*=========DC_Plus_sin_Remove_AC====================
+let indx = 0
+repeat $&numb
+let ac[indx]= sin(indx*360/8)+1 +j(0)
+let indx = indx +1
+end
+
+let fftac=fft(ac)
+plot real(fftac) imag(fftac)  vs a           title DC_Plus_SIN
+
+let fftac[2]=(0,0)
+let fftac[14]=(0,0)
+let ifftac = ifft(fftac)
+plot ifft(fftac) ac  vs a                       title SIN_REMOVED
+
+*=========DC_Plus_sin_Remove_DC====================
+let indx = 0
+repeat $&numb
+let ac[indx]= sin(indx*360/8)+1 +j(0)
+let indx = indx +1
+end
+
+let fftac=fft(ac)
+let fftac[0]=(0,0)
+let ifftac = ifft(fftac)
+plot ifft(fftac) ac  vs a                        title SIN_With_DC_REMOVED
+
+*=========DC_Plus_cos_Nyqusit_Remove_DC====================
+let indx = 0
+repeat $&numb
+let ac[indx]= cos(indx*360/2)+1 +j(0)
+let indx = indx +1
+end
+
+plot ac vs a                                 title Nyq_COS
+
+let fftac=fft(ac)
+plot real(fftac)  imag(fftac)  vs a           title Nyq_FREQ_COS
+let fftac[0]=(0,0)
+let ifftac = ifft(fftac)
+plot ifft(fftac) ac  vs a                       title COS_With_DC_REMOVED
+*=========DC_Plus_sin_Nyqusit_Remove_DC====================
+let indx = 0
+repeat $&numb
+let ac[indx]= sin(indx*360/2)+1 +j(0)
+let indx = indx +1
+end
+
+plot ac vs a                                title Nyq_SIN
+
+let fftac=fft(ac)
+plot real(fftac)  imag(fftac)  vs a         title Nyq_FREQ_SIN
+let fftac[0]=(0,0)
+let ifftac = ifft(fftac)
+plot ifft(fftac)  ac vs a                      title COS_With_DC_REMOVED
+
+*=========DC_Plus_COS_Remove_One_BIN====================
+let indx = 0
+repeat $&numb
+let ac[indx]= cos(indx*360/8)+1 +j(0)
+let indx = indx +1
+end
+
+let fftac=fft(ac)
+let fftac[2]=(0,0)
+plot real(fftac) imag(fftac)  vs a             title DC_Plus_Cos
+
+let ifftac = ifft(fftac)
+plot ifft(fftac) ac  vs a                       title ONE_BIN_REMOVED
+
+plot real(ifft(fftac)) imag(ifft(fftac))   vs a      title ONE_BIN_REMOVED
+
+.endc
+.end