[[RF.Spice A/D]] uses the same Berkeley SPICE and XSPICE simulation engines of its forerunner [[B2.Spice A/D]]. In other words, the high frequency AC analysis is carried out by the same analog and mixed-mode SPICE simulation engines based on nodal admittance analysis, which have been enhanced with additional RF simulation capabilities. As a result, you can mix the RF devices in your circuits with all the other analog and mixed-mode devices of [[B2.Spice A/D]]. You can also mix transmission-line-type RF devices with digital parts and perform mixed-mode time domain simulations.
The concepts of [[Transmission Lines|transmission lines]] and [[Multiport Networks|multiport networks]] are integral to any RF simulation. All the RF devices From a simulation point of [[RF.Spice A/D]] can be divided into two groups: devices based on transmission line modelsview, and devices based on multiple networks. [[an RF.Spice]]'s transmission line models are based on enhanced versions circuit is made up of a collection of SPICE's standard LTRA model. [[Multiport Networks|Multiport multiport networks]] that are characterized and modeled based on their frequency-domain scattering (S) interconnected via [[parametersTransmission Lines|transmission lines]]segments or components. The S-[[parameters]] are tabulated as If the input of your circuit is connected to a function of frequency source and interpolated in between its output is connected to a load, then you can compute all the frequency samplesvoltages and currents at all various circuit nodes, some of which may serve as external or internal ports of your circuit. [[RF.Spice]] performs an AC analysis Or you can calculate the port characteristics of these RF devices the overall network by converting their S-[[parameters]] designating input and output ports to Y-[[parameters]] and using them in conjunction with SPICEâs nodal admittance matrix formalismyour RF circuit.
All the RF devices of [[RF.Spice A/D]] can be divided into two groups: devices based on transmission line models, and devices based on multiple networks. [[RF.Spice]]'s transmission line models are based on enhanced versions of SPICE's standard LTRA model. [[Multiport Networks|Multiport networks]] are characterized and modeled based on their frequency-domain scattering (S) [[parameters]]. The S-[[parameters]] are tabulated as a function of frequency and interpolated in between the frequency samples. [[RF.Spice]] performs an AC analysis of these RF devices by converting their S-[[parameters]] to Y-[[parameters]] and using them in conjunction with SPICEâs nodal admittance matrix formalism. The S-parameter-based RF devices of [[RF.Spice A/D]] are primarily intended for use in two types of [[tests]]:
* AC Frequency Sweep Test
{{Note | S-parameter-based RF devices do not work with âLive Simulationâ or Transient Test as their models normally contain S-[[parameters]] at high frequencies only.}}
From a simulation point of view, an RF circuit is made up of a collection of [[Multiport Networks|multiport networks]] that are interconnected via RF [[Transmission Lines|transmission lines]]. If the input of your circuit is connected to a source and its output is connected to a load, then you can compute all the voltages and currents at all the external or internal ports of the circuit (i.e. at the various circuit nodes). Or you can calculate the port characteristics of the overall network by designating input and output ports to your RF circuit.
== Limitations of RF.Spice A/D ==