polar gain plot in dB
dbp(ph, g, Rm)
dbp(ph, g) (Rm=40 dB by default)
polar angles over [0,pi]
gain at th (g is in absolute units)
minimum dB level (Rm = 40 dB by default)
dbp(ph, g, Rm) creates polar gain plot in dB. makes polar plot of gdb=10*log10(g) versus th, omnidirectionality in azimuthal angle phi is assumed, gain plot at left side over [-pi,0] is added symmetrically, max-g is assumed to be unity (e.g., as in the output of gain1d), grid circles at Rm/4, 2Rm/4, 3Rm/4 are added and labeled.
add sample pgm