Version 4
SHEET 1 1680 680
WIRE 352 112 272 112
WIRE 592 112 512 112
WIRE 352 144 272 144
WIRE 352 176 272 176
FLAG 592 112 s
FLAG 272 176 f
FLAG 272 144 sq
FLAG 272 112 sd
SYMBOL Stepped_Sine1 432 144 R0
WINDOW 39 -76 72 Left 0
WINDOW 40 -76 100 Left 0
SYMATTR SpiceLine f1={f1} f2={f2} cycles={cycles} kd={kd}
SYMATTR InstName X1
TEXT -24 -120 Left 0 !.tran 0 {Ts} 1n uic
TEXT -16 -72 Left 0 !.param f1=20 f2=20k
TEXT -16 -40 Left 0 !.param cycles=10
TEXT 232 -152 Left 0 ;Test time-optimal stepped frequency source for Swept Sine THD meter.
TEXT 192 280 Left 0 ;.param fmul=2
TEXT -16 40 Left 0 !.param Ts=cycles*1/f1+kd
TEXT -16 0 Left 0 !.param kd=(cycles+3)/f1
TEXT 384 272 Left 0 ;If param fmul is passed <> 2 then\nTs must be readjusted!\n( nonlinear relation Ts(fmul)  )
TEXT 352 -96 Left 0 ;Frequ. is stepped at a factor of fmul : F(n+1)/F(n) = fmul\nStep duration for the 1st step is determined by param kd,\nfollowing steps have duration = cycles/actual_frequency\n \nLast step may have not exactly this duration,\ncheck & adjust Ts !