<< Graphics`Graphics`

dB[z_] = 20 Log[10, Abs[z]];      

    dg[z_] = Im[Log[z]]/Degree;

example 6.11    phase lead    p.115

gs = (s + 1)/(α s + 1 )
gωτ = gs /. 
          s ->  I τω /. α -> 0.1

LogLinearPlot[{ dB[gωτ], 
        dg[gωτ]}, {τω, 0.1, 100}, 
      PlotRange -> {{0.1, 100}, {0, 60}}, 
      PlotStyle -> {Hue[0.9], Hue[0.7]}, GridLines -> Automatic, 
      PlotPoints ->  1000]

ωtab = {0, 0.1, 0.5, 1, 2, 5, 10, 20, 30, 40, 50, 
          100};
nω = Length[ωtab]

gωτ

zu1 = 
      ParametricPlot[{Re[gωτ], 
          Im[gωτ]}, {τω, 0.1, 100}, 
        PlotRange ->  {{0, 10}, {0, 6}}, PlotStyle ->  Hue[0.9], 
        AspectRatio ->  Automatic]

p10 = 
        Table[{Re[gωτ], 
              Im[gωτ],  τω} /. τω ->  ωtab[[i]], {i, nω}];
zu2 = LabeledListPlot[p10]

Show[zu1, zu2]