subroutine avecho(id2,ndop,nfrit,nqual,f1,xlevel,snrdb,db_err,dfreq,width) integer TXLENGTH parameter (TXLENGTH=27648) !27*1024 parameter (NFFT=32768,NH=NFFT/2) parameter (NZ=4096) integer*2 id2(34560) !Buffer for Rx data real sa(NZ) !Avg spectrum relative to initial Doppler echo freq real sb(NZ) !Avg spectrum with Dither and changing Doppler removed integer nsum !Number of integrations real dop0 !Doppler shift for initial integration (Hz) real dop !Doppler shift for current integration (Hz) real s(8192) real x(NFFT) integer ipkv(1) logical ex complex c(0:NH) equivalence (x,c),(ipk,ipkv) common/echocom/nclearave,nsum,blue(NZ),red(NZ) common/echocom2/echo_spread save dop0,sa,sb fspread=echo_spread !### Use the predicted Doppler spread ### inquire(file='fspread.txt',exist=ex) if(ex) then open(39,file='fspread.txt',status='old') read(39,*) fspread close(39) endif width=fspread dop=ndop sq=0. do i=1,TXLENGTH x(i)=id2(i) sq=sq + x(i)*x(i) enddo xlevel=10.0*log10(sq/TXLENGTH) if(nclearave.ne.0) nsum=0 if(nsum.eq.0) then dop0=dop !Remember the initial Doppler sa=0. !Clear the average arrays sb=0. endif x(TXLENGTH+1:)=0. x=x/TXLENGTH call four2a(x,NFFT,1,-1,0) df=12000.0/NFFT do i=1,8192 !Get spectrum 0 - 3 kHz s(i)=real(c(i))**2 + aimag(c(i))**2 enddo fnominal=1500.0 !Nominal audio frequency w/o doppler or dither ia=nint((fnominal+dop0-nfrit)/df) ib=nint((f1+dop-nfrit)/df) if(ia.lt.600 .or. ib.lt.600) go to 900 if(ia.gt.7590 .or. ib.gt.7590) go to 900 nsum=nsum+1 do i=1,NZ sa(i)=sa(i) + s(ia+i-2048) !Center at initial doppler freq sb(i)=sb(i) + s(ib+i-2048) !Center at expected echo freq enddo call echo_snr(sa,sb,fspread,blue,red,snrdb,db_err,dfreq,snr_detect) nqual=snr_detect-2 if(nqual.lt.0) nqual=0 if(nqual.gt.10) nqual=10 ! Scale for plotting redmax=maxval(red) fac=10.0/max(redmax,10.0) blue=fac*blue red=fac*red nsmo=max(0.0,0.25*width/df) do i=1,nsmo call smo121(red,NZ) call smo121(blue,NZ) enddo ! write(*,3001) snrdb,db_err,dfreq,snr_detect,redmax,nqual,nsmo,nclearave,nsum !3001 format('A',5f10.1,4i4) 900 return end subroutine avecho