This new software is intended for use in the design of circuits in which the conventional time domain and / or the harmonic balance based simulators are inadequate. Circuits and situations that would greatly benefit from the application of this software have some, or all, of the following characteristics:

	complex, externally defined voltage and / or current source driving waveforms
	signals large enough to cause strongly non-linear operation of the active devices
	the circuit has an inherently, and strongly, non-linear electrical response
	the circuit consists of a mixture of microwave passive elements defined by S parameter data and non-linear active devices
	"transient" phenomenon are of interest, such as the start up of unintentional oscillations, or the phase shift as a function of time in a pulsed microwave circuit

Specific examples of situations in which the use of this new software is appropriate are as itemised next:

	whether an amplifier or other such circuit will unintentionally oscillate, without requiring the user to inject any "oscillation start up pulses";
	the behaviour of a VCO with slow and fast variations in the control voltage (no predictions of phase noise);
	the response of a transient overload protection circuit;
	the level of the harmonics generated in a linear amplifier when the amplifier is driven by a high level input signal;
	the interactions (particularly reflected signals) between MMICs connected through the use of transmission lines;
	the operation of ultra wide band (UWB) circuits, as used in UWB RADAR and other systems;
	the phase shift added to a single frequency input signal as a function of time in a pulsed RF circuit (causing "time varying beam skew" when such circuits are used in a phased array RADAR system), resulting from dispersive effects in the PHEMT. For example, the circuit supply voltage may be pulsed ON for 1 uSec, during which time the circuit functions as a power amplifier operating at around 10 GHz, after which the power is turned OFF for around 2.5 mSec. Such a phase shift will not be indicated through the use of a steady state simulator, such as one based on the use of the Harmonic Balance technique;

The waveforms in a circuit that is operated in a strongly non-linear manner, such as:

	a Step Recovery Diode (SRD) based circuit for impulse generation;
	a Non Linear Transmission Line (NLTL) based circuit;
	a Schottky Barrier Diode (SBD) based signal sampling circuit;

The response of a circuit to complex, base-band, driving signals such as:

	a 10 GBit/sec Non-Return-to-Zero (NRZ) Pseudo Random Bit Sequence (PRBS) as encountered in optical communications modules and circuits;
	a very wide bandwidth noise or pseudo-noise signal (such as WCDMA);
	high bit rate, parallel data bus signals. As an example, in an 8 bit wide, 1 GBit/sec, data bus, the complex electrical characteristics of the 8 coupled microstrip data tracks could be defined through the use of an electromagnetic simulator as a 16 port S parameter data set;

the response of a circuit:

	in an electrically noisy environment;
	to signals picked up from a nearby, high power, RADAR system;
	to impulses picked up from a nearby UWB RADAR system;
	to signals picked up from a nearby, high power, electronic warfare system;
	to an electromagnetic pulse (EMP) from a nuclear explosion, or other such powerful source.

The Impulse software on its own can be used to visualise the response of a passive element or circuit section in the time domain. If the visualisation indicates that part of the response appears to occur before time t=0, then the "non-causal" or "unphysical" response needs to be corrected before the data is used in any simulation. The cause of such an "unphysical" response could result from the over de-embedding of measurement data, or inaccuracies in the closed form mathematical equations used to predict the real and imaginary parts of the circuit response as a function of frequency.

Outline "impulse" Software Specifications

S or Y parameters defined in a data file using the well-known Touchstone ® format.

First frequency point need not be zero: if it is less than 1.0% of the second frequency, the software will assume this to be the zero frequency entry.

The interval between all the adjacent frequency points (with the first point assumed to be at zero Hz) must be the same, and must equal the value of the second frequency point.

Data for structures with from one to 19 ports may be used.

Any of the S or Y parameters may exhibit gain (ie. Smn > 1.0).

Outline "waveform" Software Specifications

Elements supported include:

	resistor
	capacitor
	inductor
	Voltage Controlled Voltage Source with optional use of delay
	Voltage Controlled Current Source with optional use of delay
	d.c. voltage and current sources
	sine wave voltage and current sources
	external waveform controlled voltage and current sources
	Import of 1 to 19 port S or Y parameter data blocks
	Standard SPICE compatible diode model
	TOM, TOM2, TOM3, Cobra and EEHEMT1 GaAs FET models

Software will calculate equivalent circuit model (including noise sources) values for each active device at quiescent bias point.

Software will display bias voltages and currents on the circuit schematic.

Software will generate a data base containing the predicted voltages at each node in the circuit.

Software can be used to superimpose bias plane trajectory on FET IV characteristics.