The File Utility allows you to perform a wide variety of data file tasks. You may list, print, create, edit, and delete .CKT circuit files. While this utility is quite adequate for its intended task, it's not a full featured word processor; it doesn't have features like "search and replace," etc.


When you choose "(2) File Utility" from the Main Menu, either by pressing "2," or by using the "F2" function key, you'll enter the File Utility Menu. The screen display will look as follows:

File Utility Menu

(1) List File

(2) Create File

(3) Edit File

(4) Delete File

(5) Directory

(6) Main Menu

Choose (1 - 6) ?

You may make a selection from the File Utility Menu by entering a number from 1 to 6. You don't have to press <Enter>; these are hot keys and will immediately do what you want.


These two file operations are identical in that you are asked one simple question:   Filename [<Enter>=Quit] ? _

If you want to list the FILTER demo file that exists in the \mwdata2 data sub-directory, simply type FILTER, (no extensions or paths are necessary), and press <Enter> to complete the entry.

You'll then be asked: "Print Logfile (Y/N) <Enter>=No ? _" Please press <Enter> for now.

If you choose the option to 'Print Logfile,' the data will be directed to 'Logfile.txt' within the \mwdata2 sub-directory, and to the screen. Right-click on 'Logfile.txt' to print it, and then DELETE the file; it will re-create when next needed.


Creating a .CKT Data File

When you choose "(2) Create File," from the File Utility Menu, either by pressing "2," or by using the "F2" function key, and then pressing <Enter>, you'll see the following:

            Enter line #  1 : ?_

For practice, lets re-create the file named FILTER. We will need this file later, so follow the instructions carefully. First, here is the schematic of FILTER. It's a 50 ohm 0.5 dB ripple Chebyshev low-pass filter with a 100 MHz bandwidth.


When you create a Sceptre .CKT file, its best to start from the left side. Each element in the file is coded as shown in the Element Library (see Appendix A). If you visit this appendix, use your browser BACK button to return here.

If you look at Appendix A, you'll see that the code for a shunt C capacitor and a series L inductor are, respectively, CAP and IND. Here is what the first two lines of code in the .CKT file will look like:
 
                CAP AA PA 54.3
                IND  BB SE 97.88

The element name, whether it be a capacitor, CAP, inductor, IND, series resistor-capacitor, SRC, etc. is always given first. The second column specifies the element location within the circuit, AA is left of BB, etc. The third column tells Sceptre whether an element is parallel, PA, or series, SE, connected. Finally, the last number, in the fourth column, specifies the element value in ohms, nH, pF, degrees, or a combination.

Since our FILTER circuit has five elements in it, the location code letters will start at AA and end at EE.

In response to the query:

                Enter line # 1 : ?_

Type the first two lines of the file as we did above, and press <Enter> after each entry. The first line will be:

                CAP AA PA 54.3

The second line will be:

                IND  BB SE 97.88

Now enter the remaining three lines in the same manner. Be sure to press <Enter> after typing each line, and to use the correct element values.

After entering the elements in order, from left to right, the next step is to tell Sceptre that we wish to cascade them. The CAX command does this for three or more elements. The CAS command is used for two elements, but its special in that the two elements may be anywhere in the circuit.

Given that we have five elements in this circuit, type the following command in the next line down. Don't forget to press <Enter> to complete the line entry.

                CAX AA EE

All five two-port circuit elements will now be combined and the new network named two-port AA. Here is what we have so far in the FILTER .CKT file:

                CAP AA PA 54.3
                IND  BB SE 97.88
                CAP AA PA 80.88
                IND  BB SE 97.88
                CAP AA PA 54.3
                CAX AA EE

Now that we have described the network to be analyzed, we next must specify the output format. Sceptre has four different output formats: S1, S2, IR, and OR. They are discussed in detail in Appendix C.

For the FILTER example, we'll use the S1 output format. It gives the overall s-parameters of the network, plus gain/loss, and stability data. As you well know, passive networks are always "stable," only active cirucits can be unstable, so the printing of this parameter will be automatically suppressed.

Type the following line into the FILTER .CKT file and then press <Enter>.

                PRI AA S1 50

The PRI is shorthand for PRINT, while the AA tells Sceptre which two-port data to print. S1 is the output code, and 50 ohms is the system reference impedance.

Finally, to complete this .CKT file, type END, (and press <Enter>), and then specify a list of analysis frequencies. If this circuit had contained an active device, a TWO, (short for two-port), we would enter its s-data just after the frequency line.

                END

There are two different ways to enter frequency data. First, we can enter individual analysis frequencies on one line, or, second, we can use the start, stop, step format. The latter is easier, so we'll use it here. Type in the following line:

                10 150 10

This tells Sceptre to analyze the circuit over the range of 10-150 MHz in 10 MHz steps.

All .CKT files have at least four lines. There must be at least one element in the file, a PRI command, an END, and a frequency line. If any file has less than four lines, you'll get an error message.

O.K., here is the complete .CKT file for FILTER:

CAP AA PA 54.3 IND  BB SE 97.88 CAP AA PA 80.88 IND  BB SE 97.88 CAP AA PA 54.3 CAX AA EE PRI AA S1 50 END 10 150 10

At this point, lets save the FILTER circuit file. To tell Sceptre that you're done entering data, just type an extra <Enter>.

You'll now be asked:

            Filename [<Enter>=Quit] ? _

Enter the following at the prompt:

             FILTER

Press <Enter> to complete the line entry.

The file will be saved and you'll be returned to the File Utility Menu. As you see, it's very easy to create a circuit file!

As a precaution, since this is your first time, you might want to list the FILTER file to the screen, and make sure its correct.


Editing Files

When you choose "(3) Edit File" from the File Utility Menu, either by pressing "3" or by using the "F3" function key, you'll see the following:

            Filename [<Enter>=Quit] ? _

Let's edit the FILTER data file we've just created. Type FILTER to edit the file. Here is what you should see on the screen:

Filename:  FILTER # Lines   :   9 (L)  List (D)  Delete (I )   Insert (R)  Replace (S)  Save (Q)  Quit Choose (A-Z)  ? _

You'll notice that the Function Key Menu at the bottom of the screen lists all six choices. It's always a good idea to choose "L = List" first. So press "L" and then <Enter> to list the file.

CAP AA PA 54.3 IND  BB SE 97.88 CAP AA PA 80.88 IND  BB SE 97.88 CAP AA PA 54.3 CAX AA EE PRI AA S1 50 END 10 150 10

Lets try out the "Replace" command, by changing the analysis frequency range. Choose "R" - you'll be asked which line to replace:

            Line # to replace [<Enter>=Quit] ? _

Type "9," since its the number of the frequency line. After you press <Enter> to complete the entry, Sceptre will print:

            Old:   10 150 10
            New: ? _

Type "10 200 10" to change the analysis frequency range to cover 10 to 200 MHz in 10 MHz steps. Save the changes to a new file, FILTER2, by first typing "S," (the "Save" command), and then entering the filename FILTER2.

You now have a good idea on how to use the List, Replace, and Save commands in the Edit Menu. There are just two commands, Delete and Insert, left to cover.

The Delete command should be rather obvious. Just tell Sceptre the line number, but be sure to re-alphabetize the remaining lines manually using "Replace." The Insert command involves a bit more, but not much.

If you choose "Insert" from the Edit Menu, the screen will clear and you'll see the following message and question:

             Caution: If you INSERT a line of s-data you must also INSERT an additional
             analysis frequency! If you don't, an error will occur.

             Insert line between (A,B) [<Enter>=Quit] ? _

If you want to insert a line at the top of the file, enter "0,1" to tell Sceptre that the line is to go just before the first line. If you want to add a line at the bottom, and there were nine lines in the file, (as is the case here), you would type "9,10" to add the new line at the end, in the tenth position. For now, just press <Enter> to return to the Edit Menu.

If you now type "Q" you'll return to the File Utility Menu. Try listing the file FILTER2 by using the "F1" function key, and then, since we don't need it anymore, you can delete it with the "F4" key.


Directory Listings

If you would have chosen "(5) Directory," you would see a listing of all .CKT files in the c:\mwsoft\mwdata2 sub-directory on the screen.

Press "F6" to return to the Main Menu.