Special .IMP/.CKT Files

The three-letter filename extensions .IMP and .CKT stand for, respectively, impedance and circuit. These files can be created by the Calculations Module.

The .IMP extension is automatically appended to files created by SmithMatch, our Smith Chart program, and also by OptiMatch, our match network optimization program. Sceptre, our frequency domain circuit analysis program can write a .IMP file for use by SmithMatch. It is in this way that our programs form a suite; they can talk to each other.

One proviso on files being created for use by either SmithMatch or OptiMatch is that each can have no more than ten lines maximum in it.

.IMP File Format

A .IMP file contains three entries per line. The three entries are, from left to right, frequency, Re(Z), and Im(Z). We used the NE02135A.S2P bipolar transistor data file in the Calculations Module to compute the unilateral input impedance of the device. We then created a .IMP file. The file created by SData+ looks like this:

100.000    42.488    -142.513          500.000   11.884      -24.323        1000.000   10.460        -7.152        1500.000   10.609         0.833        2000.000   10.832         7.129        2500.000   10.896       12.354        3000.000   11.465       16.874        3500.000   12.021       22.716        4000.000   12.428       26.949

If the file is to be used by either SmithMatch or OptiMatch, it is limited in length to ten lines, and the frequency term must be in units of MHz.

When we created this file in SData+ and went to save it as a .IMP file, SData+ caught the fact that the frequency units were in terms of GHz, and asked if we wanted to convert them to MHz, to which we replied "Y."

.CKT File Format

A .CKT file contains nine entries per line.  The nine entries are, from left to right, frequency, S11 Mag/Phase, S21 Mag/Phase, S12 Mag/Phase, and S22 Mag/Phase.

As we did with a .IMP file above, we used the NE02135A data file and opted to create a .CKT file to use with Sceptre. The file created by SData+ looks as follows:

1  TWO  AA  S1  50        2  PRI    AA  S1  50        3  END        4  DATA  100  500  1000  1500  2000  2500  3000  3500  4000  -1        5  DATA  0.840  -36  13.82  156  0.020  73  0.940  -18        6  DATA  0.680  -126  7.18  106  0.080  35  0.510  -53        7  DATA  0.660  -163  4.02  81  0.090  27  0.340  -66        8  DATA  0.650  178  2.75  64  0.100  27  0.310  -74        9  DATA  0.650  163  2.10  52  0.120  30  0.310  -83        10  DATA  0.660  151  1.68  39  0.130  26  0.310  -95        11  DATA  0.660  141  1.46  27  0.140  26  0.330  -106        12  DATA  0.670  129  1.24  17  0.160  26  0.360  -116        13  DATA  0.680  121  1.14  5  0.170  23  0.380  -127

The .CKT file created for Sceptre includes more than just the s-data. It is a complete file, and includes the code which allows Sceptre to do a normal type "S1" analysis. In this case, Sceptre Users will recognize that the file contains two-port s-data over the range of 100-4000 MHz, and that Sceptre is being told to perform an s-parameter gain and stability analysis.

The file structure is such that you can easily edit it within Sceptre. You can add impedance match networks on either side of the "TWO" and create an amplifier. Naturally, using other programs within our MicroWorks Design Suite, i.e., SmithMatch and OptiMatch, you could create and optimize those match networks.