Square Wave

Square Wave generates a real-valued binary time-domain waveform from configurable low and high levels, transition timing, and a manual bit sequence.

Formula

Let:

• $L = \mathrm{Alow}$
• $H = \mathrm{Ahigh}$
• $P = \mathrm{Ttotal}$
• $d = \mathrm{Tdelay}$
• $r = \mathrm{Trise}$
• $h = \mathrm{Thold}$
• $f = \mathrm{Tfall}$

Each bit has duration:

$B = \frac{P}{2}$

For a sequence containing $N$ bits, the sequence duration is:

$D = NB = N\frac{P}{2}$

This Ttotal / 2 bit duration is the Tidy3D RF timing convention. There is no separate Period parameter.

For an isolated 10 pulse beginning at Alow, the local waveform is:

$E(u)= \begin{cases} L, & 0 \le u < d \\ L+(H-L)\dfrac{u-d}{r}, & d \le u < d+r \\ H, & d+r \le u < d+r+h \\ H+(L-H)\dfrac{u-d-r-h}{f}, & d+r+h \le u < d+r+h+f \\ L, & d+r+h+f \le u \le P \end{cases}$

For a 1 to 0 transition in a bit sequence, the falling-edge delay is:

$q=d+r+h-B$

The sequence is composed as follows:

• 0 → 0: remain at $L$.
• 0 → 1: remain at $L$ for $d$, rise during $r$, then remain at $H$.
• 1 → 1: remain at $H$; do not restart the pulse.
• 1 → 0: remain at $H$ for $q$, fall during $f$, then remain at $L$.

InitBit supplies the state before the first sequence bit and is applied only once.

Parameters

Signal delay: Shifts the complete generated waveform once in time.

• Default: 0, Global Unit
• May be positive, zero, or negative
• A negative value starts the simulation partway through the waveform
• Does not change the bit or sequence duration
• Differs from Tdelay, which applies inside each rising transition

Alow: Amplitude representing logical 0.

• Default: 0
• May be signed
• May equal Ahigh

Ahigh: Amplitude representing logical 1.

• Default: 1
• May be signed
• This is the actual waveform level; no additional carrier amplitude is applied

Trise: Duration of a linear 0 → 1 transition.

• Default: 0.1, Global Unit
• Must be greater than zero
• Must satisfy $\mathrm{Tdelay} + \mathrm{Trise} \le \mathrm{Ttotal}/2$

Tfall: Duration of a linear 1 → 0 transition.

• Default: 0.1, Global Unit
• Must be greater than zero

Tdelay: Time spent at Alow before a rising transition starts.

• Default: 0, Global Unit
• Must be nonnegative
• Applies to each 0 → 1 transition
• Does not shift the complete waveform

Thold: High-level plateau duration for an isolated 10 pulse.

• Default: 1, Global Unit
• Must be nonnegative
• Each additional consecutive 1 extends the high plateau by Ttotal / 2

Ttotal: Duration of an isolated 10 pulse.

• Default: 2, Global Unit
• Must be greater than zero
• Each bit lasts Ttotal / 2
• For $N$ bits, the complete sequence lasts $N \times \mathrm{Ttotal}/2$

InitBit: Logical state before BitSequence begins.

• Default: 0
• Options: 0, 1
• Applied only once at waveform startup
• Not reapplied at periodic repetition boundaries

BitSequence: Binary states used to construct the waveform.

• Default: 101010
• Must be a nonempty string containing only 0 and 1
• Leading zeros are preserved
• Consecutive equal bits hold their current level without creating another edge

Periodic: Controls behavior after one complete bit sequence.

• Default: enabled
• Enabled: repeat the complete sequence
• Disabled: generate the sequence once, then hold its final amplitude
• At a repetition boundary, compare the final bit with the first bit
• Equal boundary states do not create another transition
• Changes repetition versus endpoint holding but does not change a manual preview endpoint
• A periodic Auto preview shows two complete sequences
• A non-periodic Auto preview shows one complete sequence followed by a short final-level hold
• Periodic simulation submission requires a resolved finite positive manual Run Time
• A manual Run Time derived from global frequency is valid when it resolves to a finite positive duration

Timing constraints

After converting all time quantities to the same unit, the following conditions must hold:

$\mathrm{Tdelay} + \mathrm{Trise} \le \frac{\mathrm{Ttotal}}{2}$

$\mathrm{Tdelay} + \mathrm{Trise} + \mathrm{Thold} \ge \frac{\mathrm{Ttotal}}{2}$

$\mathrm{Tdelay} + \mathrm{Trise} + \mathrm{Thold} + \mathrm{Tfall} \le \mathrm{Ttotal}$

• Boundary equality is valid
• Invalid values are not clamped or automatically adjusted
• Invalid form drafts remain visible for correction but are not saved
• Preview continues to use the last valid saved waveform

Preview duration is controlled by Run Time. With a finite positive manual Run Time $R$, the preview covers exactly $[0,R]$ and may end inside a bit or transition. Auto Run Time uses a source-defined preview window.