I'm reading code from Paul Muller, which is available from this web site.
However, the part on sj_src is pretty strange. Why in quoted line need to multiply freq and sj_freq twice? Is it a typo?
architecture bhv of sj_src is
constant sj_tau : time := 10ps;
quantity vsj_out across isj_out through sj_out;
quantity vsj_int : voltage;
begin
-- All quantities considered in a 50 Ohm environment
-- Voltage source is 2 * effective voltage
-- sj_amp is considered a PP voltage
-- output signal is centered around Vdd/2=0.0V
Quote: vsj_int == 2.0 * (0.0 + 0.9 * 0.5 * sj_amp * sin(MATH_2_PI*sj_freq*freq*NOW));
vsj_out == vsj_int + isj_out * 50.0;
end bhv;