From cdcdedfe40fca3b30a0f4cce58c30f50128a8185 Mon Sep 17 00:00:00 2001
From: Joe Taylor <joe@princeton.edu>
Date: Fri, 16 Feb 2024 16:11:01 -0500
Subject: [PATCH] Temporary code (### commented out ###) for calibrating SNR.

---
 lib/superfox/ftrsd3.f90   |  5 +----
 lib/superfox/plotspec.f90 | 39 +++++++++++++++++++++++++++++++++++++++
 lib/superfox/sfoxtest.f90 | 15 +++++++++------
 3 files changed, 49 insertions(+), 10 deletions(-)
 create mode 100644 lib/superfox/plotspec.f90

diff --git a/lib/superfox/ftrsd3.f90 b/lib/superfox/ftrsd3.f90
index 8eeab08a3..a4cbf4d4d 100644
--- a/lib/superfox/ftrsd3.f90
+++ b/lib/superfox/ftrsd3.f90
@@ -143,10 +143,7 @@ subroutine ftrsd3(s3,chansym0,rxdat,rxprob,rxdat2,rxprob2,ntrials0,  &
         endif
      enddo
      call rs_decode_sf(workdat,era_pos,numera,nerr)    !Call the decoder
-     do i=0,NN-1
-        write(60,3101) i,chansym0(i),workdat(i),workdat(i)-chansym0(i)
-3101    format(4i8)
-     enddo
+
      if( nerr.ge.0) then
       ! We have a candidate codeword.  Find its hard and soft distance from
       ! the received word.  Also find pp1 and pp2 from the full array 
diff --git a/lib/superfox/plotspec.f90 b/lib/superfox/plotspec.f90
new file mode 100644
index 000000000..08fab4e64
--- /dev/null
+++ b/lib/superfox/plotspec.f90
@@ -0,0 +1,39 @@
+subroutine plotspec(dat)
+
+  use sfox_mod
+  real dat(NMAX)
+  real s(0:NSPS/2)
+  complex c(0:NSPS-1)
+  integer ipk(1)
+
+  nblks=NZ/NSPS
+  s=0.
+  fac=1.0/NSPS
+  do j=1,nblks
+     ib=j*NSPS
+     ia=ib-NSPS+1
+     c=fac*dat(ia:ib)
+     call four2a(c,NSPS,1,-1,1)
+     do i=0,NSPS/2
+        s(i)=s(i) + real(c(i))**2 + aimag(c(i))**2
+     enddo
+  enddo
+
+  df=12000.0/NSPS
+  ipk=maxloc(s)
+  f0=df*(ipk(1)-1)
+  p_sig_plus_noise=maxval(s)
+  p_noise=0.
+  do i=0,NSPS/2
+     f=i*df
+     if(f.le.2500+df .and. abs(f-f0).gt.0.5*df) p_noise=p_noise + s(i)
+     write(40,1000) f,s(i)
+1000 format(2f10.3)
+  enddo
+  p_sig=p_sig_plus_noise - p_noise*df/2500.0
+  snr=p_sig/p_noise
+  snrdb=db(snr)
+  write(*,1100) snrdb
+1100 format('Measured SNR:',f7.2)
+
+end subroutine plotspec
diff --git a/lib/superfox/sfoxtest.f90 b/lib/superfox/sfoxtest.f90
index a3c94187d..c461ff982 100644
--- a/lib/superfox/sfoxtest.f90
+++ b/lib/superfox/sfoxtest.f90
@@ -114,6 +114,7 @@ program sfoxtest
   call rs_encode_sf(msg0,parsym)            !Compute parity symbols
   chansym0(0:kk-1)=msg0(1:kk)
   chansym0(kk:nn-1)=parsym(1:nn-kk)
+!  chansym0=NQ/2  !### TEMPORARY, for SNR calibration ###
 
 ! Generate clo, the LO for sync detection
   call timer('clo     ',0)
@@ -161,17 +162,17 @@ program sfoxtest
         
         crcvd=0.
         crcvd(1:NMAX)=cshift(sig*cdat(1:NMAX),-nint(xdt*fsample)) + cnoise
-
-        dat=aimag(sig*cdat(1:NMAX)) + xnoise     !Add generated AWGN noise
-        fac=32767.0
-        if(snr.ge.90.0) iwave(1:NMAX)=nint(fac*dat(1:NMAX))
-        if(snr.lt.90.0) iwave(1:NMAX)=nint(rms*dat(1:NMAX))
-
         call timer('watterso',0)
         if(fspread.ne.0 .or. delay.ne.0) call watterson(crcvd,NMAX,NZ,fsample,&
              delay,fspread)
         call timer('watterso',1)
 
+        dat=aimag(sig*cdat(1:NMAX)) + xnoise     !Add generated AWGN noise
+!        call plotspec(dat)     !### TEMPORARY, for SNR calibration ###
+        fac=32767.0
+        if(snr.ge.90.0) iwave(1:NMAX)=nint(fac*dat(1:NMAX))
+        if(snr.lt.90.0) iwave(1:NMAX)=nint(rms*dat(1:NMAX))
+
 ! Find signal freq and DT
         call timer('sync    ',0)
         call sfox_sync(crcvd,clo,nv,f,t)
@@ -248,3 +249,5 @@ program sfoxtest
 
 999 call timer('sfoxtest',101)
 end program sfoxtest
+
+! include 'plotspec.f90'    !### TEMPORARY, for SNR calibration ###