| Uniform Distributed RC Model (URC) |
The model of the Uniform Distributed RC lines is identified by the type specifier URC.
| .MODEL <model name> URC [model parameters] |
| Parameter | Description | Units | Default | Example |
| K | Propagation Constant | 2 | 1.2 | |
| FMAX | Maximum Frequency of interest | Hz | 1.0G | 6.5Meg |
| RPERL | Resistance per unit length | Ω/m | 1000 | 10 |
| CPERL | Capacitance per unit length | F/m | 1.0e-15 | 1pF |
| ISPERL | Saturation Current per unit length | A/m | 0 | |
| RSPERL | Diode Resistance per unit length | Ω/m | 0 |
The URC model is derived from a model proposed by L. Gertzberrg in 1974. The model is accomplished by a subcicuit type expansion of the URC line into a network of lumped RC segments with internally generated nodes. The RC segments are in a geometric progression, increasing toward the middle of the URC line, with K as a proportionality constant.
The URC line is made up strictly of resistor and capacitor segments unless the ISPERL parameter is given a non-zero value, in which case the capacitors are replaced with reverse biased diodes with a zero-bias junction capacitance equivalent to the capacitance replaced, and with a saturation current of ISPERL amps per meter of transmission line and an optional series resistance equivalent to RSPERL ohms per meter.
The number of lumped segments used, if not specified for the URC line device, is determined by the following formula:
.MODEL MURC URC RPERL=50 CPERL=5pF