How to use a Lossless Transmission Line in Spectre Transient analysis

Not entirely surprising that an article on transmission line modelling based on their physical properties doesn’t cover ideal transmission lines (the related article referenced below it does mention the tline component, but advises against using it, mainly for modelling lossy lines though).

if you want a lossless ideal line, use tline from analogLiv and specify the impedance and delay. See “spectre -h tline”, especially the part at the bottom which describes lossless transmission lines. 

Note that one should always be careful with ideal component modelling as these are not what circuit simulators are really best for and can lead to non-physical behaviour (obviously, since a practical transmission line would never be lossless)

Andrew

Thanks a lot Andrew.

As I see, tline has 13 Instance Parameters however, in the edit property form  is having only 9 parameters. Any specific reason for this ? Can we use Add button to add these remaining parameters ?

I think it's historical. The instance parameters which are not available are also available as model parameters (I have a vague recollection that they were only model parameters in the past).

So to use them, you either need to create a copy of the tline component, and add the additional parameters into the CDF and the spectre simulation information in the CDF, or define a model and specifiy them that way. However, they are all related to lossy transmission lines, and the article I mentioned before suggests that you don't use the old lossy tline model to represent lossy transmission lines because it's particularly accurate. You can't just add the additional parameters on the create instance or edit properties form because the spectre netlister wouldn't netlist them anyway.

Regards,

Andrew.

Hi RFStuff,

The Tool Filter in the Schematic will display the properties supported for a particular simulator (e.g. hspiceD, spectre, ams, etc).  

The spectre -h lists 17 parameters.  Not all are available in the analogLib tline.

As Andrew mentioned, the tline parameter has been deprecated - the tline model is based on old technology, and not nearly as accurate as the mtline and rfTlineLib elements.  We strongly recommend using the rfTlineLib for transmission line elements.

best regards,

Tawna

Thanks a lot Andrew.

Thanks Tawna.