a=[ 20    40    60   100   150   300   500   520   550   600   650   700   710   720  760   800   900
    60    65    70    75    80    92    95    90    85   110   105   105   100    95  105   110   100
];
b= [  20  40   50   80   100    200     400    500      550    740   750     
      65  72   73   80   83      91     100    100       90    110   100      
      ];
f=[10  30  100     1000   ];
sta=[-97 -112 -127  -147   ];
      

% semilogx(f,sta,'m');
% hold on
% semilogx(a(1,:),-a(2,:),'r');
% hold on
% semilogx(b(1,:),-b(2,:),'b');
% grid on
% legend

ax=[20 40 60 70 80 90 100 200 300 400 500 600 700 800 900 1000
   70 74  78 80 83 84 85 92 97 102 102 105 87 100 103 103 ]  ;
  
ay=[ 20 30 40 50 60 70 80 90 100 200 300 400 500 600 700 800 900 1000
     50 52 55 60 62 63 65 66 70  79  83  87   89  91  92  93  94  92 ] ;
semilogx(f,sta,'m');
hold on
plot(ay(1,:),-ay(2,:),'b');
hold on
semilogx(a(1,:),-a(2,:),'r');
hold on
semilogx(ax(1,:),-ax(2,:),'g');

hold on
pd=2;

g=1e-10;

fm=10.^(1:0.1:3)

ssb=20*log10(sqrt(pd)*100e6*g./(2*fm));


semilogx(fm,ssb)
grid
grid