-------------------------------------------------------------------------------
-- Copyright (c) 2001 Mentor Graphics Corporation
--
-- This model is a component of the Mentor Graphics VHDL-AMS educational open 
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-------------------------------------------------------------------------------
-- File       : Lead_Lag_Ztf.vhd
-- Author     : Mentor Graphics
-- Created    : 2002/05/21
-- Last update: 2002/05/21
-------------------------------------------------------------------------------
-- Description: Z-domain Lead-Lag Compensator with electrical connections. 
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version     Author              Description
-- 2002/05/21  1.0         Mentor Graphics     Created    
-------------------------------------------------------------------------------

library IEEE; use IEEE.std_logic_1164.all; use IEEE.math_real.all;
library IEEE; use IEEE.electrical_systems.all;

entity Lead_Lag_Ztf is
	generic (	fp : real := 2000.0;	-- Pole in Hz for 'ztf
				fz : real := 5.0;	-- Zero in Hz for 'ztf
				k : real := 400.0;  -- Normalizing gain
				Fsmp : real := 10.0e3);	-- Sample frequency for 'ztf 
	port 	(	signal clk : in std_logic; -- Clock is used for the Difference equations only
				terminal input: electrical;
				terminal output: electrical);
end entity Lead_Lag_Ztf;
-------------------------------------------------------------------------------
-- Transfer Function is derived from the following using the bilinear transform:
--
--              1 + (s/wz)
--  H(s) = K * ------------
--              1 + (s/wp)
-- 
-------------------------------------------------------------------------------
architecture ztf of Lead_Lag_Ztf is
	QUANTITY vin ACROSS input TO ELECTRICAL_REF;
	QUANTITY vout ACROSS iout THROUGH output TO ELECTRICAL_REF;
	constant T : real := 1.0/Fsmp;	-- Sample period
	constant wz : real := fz*math_2_pi;	-- Pole in rad/s
	constant wp : real := fp*math_2_pi;	-- Pole in rad/s
	constant n0 : real := 2.0 + T*wz; 	-- z0 numerator coefficient
	constant n1 : real := T*wz - 2.0; 	-- z-1 numerator coefficient
	constant d0 : real := 2.0 + T*wp; 	-- z0 denominator coefficient
	constant d1 : real := T*wp - 2.0; 	-- z-1 denominator coefficient
	constant num : real_vector := (n0, n1); 
	constant den : real_vector := (d0, d1);
begin	-- ztf
	vout == k*vin'Ztf(num,den,T);   
end ztf;