PFD、CP、LPF、VCO、divider电路 verilogA建模

以下是几个基本模块的 Verilog-A 建模示例：

1. PFD (Phase Frequency Detector)

`include "constants.vams"

module pfd (in1, in2, outp, outn, clk);

parameter real kpd = 1;

input in1, in2, clk;
output outp, outn;

analog begin
  real phase_diff, delta_freq, vpd;
  
  phase_diff = (in1 - in2) * 2 * PI;
  delta_freq = phase_diff / tstep;
  vpd = kpd * delta_freq;
  
  outp <+ vpd * clk;
  outn <+ -vpd * clk;
end

endmodule

2. CP (Charge Pump)

`include "constants.vams"

module cp (in1, in2, outp, outn);

parameter real kp = 1;

input in1, in2;
output outp, outn;

analog begin
  real vcp;
  
  vcp = kp * (in1 - in2) / tstep;
  
  outp <+ vcp;
  outn <+ -vcp;
end

endmodule

3. LPF (Low Pass Filter)

`include "constants.vams"

module lpf (inp, outp);

parameter real R = 1e3, C = 1e-9;

input inp;
output outp;

analog begin
  real vlpf;
  
  vlpf = inp - outp / (R * C * s);
  
  outp <+ vlpf;
end

endmodule

4. VCO (Voltage Controlled Oscillator)

`include "constants.vams"

module vco (inp, outp);

parameter real freq = 1e6, kvco = 1;

input inp;
output outp;

analog begin
  real vco_freq, vout;
  
  vco_freq = freq + kvco * inp;
  vout = sin(2 * PI * vco_freq * t);
  
  outp <+ vout;
end

endmodule

5. Divider

`include "constants.vams"

module divider (inp, outp);

parameter integer N = 2;

input inp;
output outp;

analog begin
  real vout;
  
  vout = inp * (mod(floor(t / (1 / (N * f))), N) == 0);
  
  outp <+ vout;
end

endmodule

其中，`constants.vams` 文件包含了 Verilog-A 中需要的常量和函数，如：

real PI = 3.141592653589793;
real e = 2.718281828459045;
real k = 1.38064852e-23;
real q = 1.60217662e-19;
real T = 300;

real s = 1j * w;
real tstep = $timestep;
real f = $f;