# Transform Function Messages

Sometimes you may receive a warning or error message when attempting to create a transfer function. Refer to the list below for the meaning of each of these messages as well as suggested corrective actions.

## 1 port Files Allowed at Source and Load Blocks Only

In 2 port de-embedding, you are only allowed to use 1 port files for Transmitter, Receiver, and Scope / Probe blocks. If you try to use a 1 port file anywhere else, you will get this error.

## 2 port Files Allowed at Source and Load Blocks Only

In 4 port de-embedding, you are only allowed to use 2 port files for Transmitter, Receiver, and Scope / Probe blocks. If you try to use a 2port file anywhere else, you will get this error.

## Calculation Aborted

This error indicates that you chose to abort the transfer function computation before it was written to a file.

## Cannot Read 4 Port Data From a 2 Port File

This error means that you have attempted to load two-port file data into a four-port model block. If you want to define a four-port block with two-port files, you need to use the (2) two-Port or (2) two-Port Differential Block Port Type settings.

## DEFAULT_FREQUENCY_RESOLUTION Value is Too Small

The DEFAULT_FREQUENCY_RESOLUTION value provided in the S-parameter file is too small and yields more than the allowed 100,000 frequency points.

## Files May Only Contain a Single Data Package

Each CITIfile file may only model a single device.

## File Not Found

This indicates that the file is not where you are telling the de-embedding operator it is located or it has the wrong name.

## Impedance of All Ports Must Be the Same

The .citi format allows you to specify a unique port impedance for each port. They must all be the same for de-embedding operators or you will get this error.

## Invalid Data Format (DBANGLE, MAGANGLE, RI only)

You are only allowed to use DBANGLE, MAGANGLE, or RI data value formats with CITIfile files. If you use any other data format, you will get this error message.

## Invalid Data Format (DB, MA, RI only)

You are only allowed to use BE, BD, MA, or RI data value formats with ATF and Touchstone files. If you use any other data format, you will get this error message.

## Invalid File Format

The de-embedding operator could not recognize the indicated S-parameter file format.

## Invalid File Name

This indicates that the file extension is wrong or invalid for the type of file needed.

## Invalid Frequency Units (HZ, KHZ, MHZ, GHZ only)

You are only allowed to use Hz, kHz, MHz, and GHz in your S-parameter file. If you use anything else, you will get this error.

## Invalid Output Name

This means you probably gave the Save As file name an improper file extension.

## Invalid RETURN_LOSS_INTERPRETATION Value

The RETURN_LOSS_INTERPRETATION value in the S-parameter file must be set to either SCOPE, PROBE, SERIES_RLC, SHUNT_RLC, or DEFAULT.

## Less Than 2 Data Points in the File

You must have at least two data points in your S-parameter and transfer function files.

## Signal Amplitude at Measurement Node is Too Small

This message usually means you made a mistake when setting up your measurement circuit (example, placed an open circuit block somewhere between the source and measurement nodes). This may also occur is an S-parameter file in the measurement circuit has a resonant "suck-out" that the transfer function is trying to compensate. This warning indicates that the voltage seen at the measurement node is very small. It could be that your specific setup does indeed cause this to occur and there was no error made, but more often than not you should go back and check your measurement circuit setup.

## Transfer Function Data Must Contain a 0 Hz Point

This is not true for S-parameter function files, but is true for transfer function files.

## Unspecified Error

An internal error was detected by the de-embedding operator. Please contact Keysight Technical Support.

## Unspecified File Read Error

This indicates that the file has an invalid format.

## Unspecified File Write Error

An internal error was detected in the de-embedding operator. Please contact Keysight Technical Support.

## Unstable or Ill-conditioned Circuit Definition

When you get this message it means one of your circuits is invalid. This warning indicates that an infinite voltage is present in the circuit (analogous to an oscillation) or in other words, the gain becomes infinite.

## Warning: File Data Truncated to 100 kpts

This warning means there are too many points in your S-parameter file. You need to reduce the number of points.

## Warning: Frequency Resolution May Be Too Large for Slow Time Constants

This is similar to the warning two above this except that instead of a model's long time delay causing the problem, it is the model's slow time constants. These kind of models require finer frequency resolution. Therefore, you need to have a finer sampling of frequencies in your S-parameter file.

## Warning: Frequency Resolution May Be Too Large for Time Delay

S-parameter models that have long time delays require finer frequency resolution because the model's impulse response needs to be longer. This warning indicates that your S-parameter file may not have enough resolution to accurately represent the modeled device. Therefore, you need to have a finer sampling of frequencies in your S-parameter file.

## Warning: Interpolated S-parameters Limited to 100 kpts

The interpolation performed by the de-embedding operator on your file data resulted in too many points. The de-embedding operator sets the resolution by looking at the separation between the last two points in the file. If these values are too close together, it can cause the resolution to be too fine. The S-parameter file command #DSO DEFAULT_FREQUENCY_RESOLUTION, can force the de-embedding operator to have a different resolution than that specified by the frequency spacing in the file. If you used this command with too fine a resolution, this warning message can occur.

## Warning: Non-uniformly Sampled Data

S-parameter files with uniformly spaced points do not have to be interpreted. If the points are not uniformly spaced, the de-embedding operator attempts to set the resolution by looking at the separation between the last two points in the file. This can result in incorrect data, especially if you are using a pure log sweep, which is not recommended..

## Warning: Transfer Function Appears to Invert Signal

This warning typically happens with 4 port de-embedding. There is one particular non-standard port ordering that can cause the 4 port model to invert the signal polarity. Unfortunately, this uncommon port ordering cannot be corrected with any combination of the Flip Model and 4 Port Numbering controls. Again, it could be that your specific setup does indeed cause signal polarity inversion to occur and there was no error made (for example, if you are modeling an inverting amplifier), but more often than not there is a problem with the S-parameter file port ordering.

## Warning: Transfer Function Gain is Unusually Large

The voltage at the simulation node is extremely high when compared with the voltage at the measurement node, when driven by the same source. This usually indicates an incorrect measurement circuit setup. For example, an open circuit block is placed somewhere that is preventing the source from driving the measurement node. First check your measurement circuit to ensure there are no errors. An S-parameter file in the measurement circuit may have a resonant "suck-out" that the transfer function is trying to compensate. It could also be that your specific setup does indeed cause a large gain in the transfer function.

## Warning: Unrecognized ATF File Version (A.01.00 Only)

This warning indicates that the de-embedding operator does not support the ATF file you are attempting to use. De-embedding operators support only A.01.00 ATF files.

## Warning: Unrecognized CITIfile Version (A.01.00 and A.01.01 Only)

This warning indicates that the de-embedding operator does not support the CITIfile you are attempting to use. De-embedding operators support only A.01.00 and A.01.01 CITIfiles.