set terminal  pdf color enhanced size 15cm,5cm font "Helvetica,10pt"
set output "sincfilter.pdf"

# om is the product (omega Delta t) 
h(M,om)=(1.0/M)*sin(om*M/2)/ sin(om/2)

decibel(x)=20*log10(abs(x))

set multiplot

# linear plot
set origin 0,0
set size 0.5,1
set xrange [0:1]
set xlabel "{/Symbol w} / {/Symbol w}_S" offset 0,0.7
set ylabel "|h({/Symbol w})|"


plot abs(h(2,2*pi*x))  title "N=2", \
     abs(h(3,2*pi*x))  title "N=3", \
     abs(h(4,2*pi*x))  title "N=4", \
     abs(h(10,2*pi*x)) title "N=10"

# Log plot
set origin 0.5,0
set size 0.5,1

set logscale x
set xrange [0.01:1]
set yrange [-30:0]
set ylabel "|h({/Symbol w})| in dB"


plot decibel(h(2,2*pi*x)) title "N=2", \
     decibel(h(3,2*pi*x)) title "N=3", \
     decibel(h(4,2*pi*x)) title "N=4", \
     decibel(h(10,2*pi*x)) title "N=10"