Loop Gain Stability Measurement

Overview

This section introduces an example of how to measurement loop stability for low-frequency amplifier.

Procedure

In this example, the DUT is evaluated by following the steps.

Step	Description
1. Setting the Measurement Conditions	Set the measurement conditions.
2. Executing Calibration	Execute calibration.
3. Connecting the DUT	Connect the DUT.
4. Scaling	Adjust the scale to confirm the result of measurement.

1. Setting the Measurement Conditions

The measurement conditions are defined by following the steps described below.

Setup Description	Key Operation
Presetting	Preset > OK
Setting trace number: 2	Display > Num of Traces > 2 > Allocate Traces > x2
Specifies measurement port: Gain-Phase	Meas > Measurement Port > Gain-Phase The measurement parameters are not specified, because the measurement parameters of both channel are T/R.
Specifies impedance of receiver port: 1 MΩ	Meas > Gain-Phase Setup > T Input Z > 1 MΩ Meas > Gain-Phase Setup > R Input Z > 1 MΩ
Specifies attenuator of receiver port: 20 dB	Meas > Gain-Phase Setup > T Attenuator > 20 dB Meas > Gain-Phase Setup > R Attenuator > 20 dB
Data format: Tr1:LogMag Tr2:Phase	(Tr1) Format > Log Mag (Tr2) Format > Phase
Sweep type: Log Frequency	Sweep Setup > Sweep Type > Log Freq
Start frequency: 100 Hz	Start > 1 > 0 > 0 > x1
Stop frequency: 1 MHz	Stop > 1 > M/u
IF bandwidth auto: ON	Avg > IFBW Auto (Turn it ON.)
IF bandwidth auto limit: 100 Hz	Avg > IFBW Auto Limit > 1 > 0 > 0 > x1
Power: -20 dBm	Sweep Setup > Power > Power > +/- > 2 > 0 > x1

2. Executing Calibration

The THRU response calibration (Gain-Phase) is executed.

Setup Description	Key Operation or Connecting Operation
Connect THRU connection	Connect THRU connection.
Executing the THRU response	Cal > Calibrate > Response (Thru) > Thru > Done

3. Connecting the DUT

Connect the DUT as shown below.

4. Scaling

Set each parameter for the scale setting. It is necessary to specify the trace pressing the Trace Next or Trace Prev before each parameter is specified. The following table is example of setting.

Setup Description	Key Operation
Scale divisions: 10	(Tr1) Scale > Divisions > 1 > 0 > x1 (Tr2) Scale > Divisions > 1 > 0 > x1
Scale/Div: 10 dB/div (Tr1), 45 °/div (Tr2)	(Tr1) Scale > Scale/Div > 1 > 0 > x1 (Tr2) Scale > Scale/Div > 4 > 5 > x1
Reference position: 5 Div	(Tr1) Scale > Reference Position > 5 > x1 (Tr2) Scale > Reference Position > 5 > x1
Reference value: 0 dB (Tr1), 0 °/div (Tr2)	(Tr1) Scale > Reference Value > 0 > x1 (Tr2) Scale > Reference Value > 0 > x1

Example of the loop gain stability measurement screen