delay_xbit :
An ideal delay element for xbit-typed signals.

The delay_xbit primitive delays an xbit-typed input signal by a specified amount. The implemented delay is ‘transport delay’, meaning that each input event is propagated to the output with equal delays. Note that the buf_xbit and other xbit-typed logic gate primitives implement inertial delays.

The transport delay is specified by the parameter delay, which must be greater than a unit simulation time step. The parameter init_value defines the initial output value at time=0 (default: x).

The delay_xbit primitive can also add random jitter or phase noise to the output signal. The added random jitter can contain independent jitter as well as accumulated jitter, each of which is specified by the parameter RJ_rms and RJ_kappa, respectively. The parameter RJ_rms defines the RMS value of the independent random jitter, which has fixed statistics regardless of the delay. On the other hand, the parameter RJ_kappa defines the RMS value of the accumulated random jitter, which increases as a square-root function of the delay. The total RMS value of the random jitter added to the output signal can be expressed as:

        Total RMS value of random jitter (RJ) = sqrt(RJ_rms^2 + RJ_kappa^2 * delay).

Alternatively, the added phase noise of the output clock can be specified using the phase noise parameters PN_fcenter, PN_foffset, PN_dbc, PN_fcorner, and PN_floor. Defining these phase noise parameters is equivalent to defining the random jitter parameters satisfying the following relationships:

        RJ_rms = 10^(PN_floor/20) / (2π*sqrt(PN_fcenter)),
        RJ_kappa = 10^(PN_dbc/20) * PN_foffset / PN_fcenter.

Note that the random jitter parameters RJ_rms and RJ_kappa cannot describe the 1/f noise (e.g. flicker noise) being accumulated over the delay, while the phase noise parameters can (PN_fcorner). For more information on these phase noise parameters, please refer to the documentation on the clk_gen primitive. These parameters typically describe the phase noise of an oscillator producing a clock at a certain frequency.

Input/Output Terminals

Name	I/O	Type	Description
out	output	xbit	output signal
in	input	xbit	input signal

Parameters

Name	Type	Default	Unit	Description
delay	real	0.0	second	transport delay
init_value	logic	1’bx	None	initial output value
RJ_kappa	real	0.0	second	RMS accumulated random jitter after 1 second
RJ_rms	real	0.0	second	RMS independent random jitter
PN_fcenter	real	-1.0	Hz	phase noise center frequency
PN_foffset	real	0.0	Hz	phase noise offset frequency
PN_dbc	real	-`INFINITY	dBc/Hz	phase noise measured in dBc/Hz
PN_fcorner	real	0.0	Hz	1/f^3 phase noise corner frequency
PN_floor	real	-`INFINITY	dBc/Hz	phase noise floor measured in dBc/Hz