VectorStar™ MS4640A Series Microwave Vector Network Analyzers : AutoCal Procedures : Pre-Calibration Instrument Setup
 
Pre-Calibration Instrument Setup
Use this procedure to setup the minimum required instrument configuration parameters:
• Frequency Start
• Frequency Stop
• Number of Points
Any other required measurement parameters must be defined and applied before the AutoCal procedure. This section provides a highlight of typical additional measurement parameters.
Segmented Sweep
If required, segmented sweep must be setup in advance if the calibration needs a custom frequency list. See Frequency-Based Segmented Sweep.
IF Bandwidth (IFBW) and Averaging
IF Bandwidth and Averaging control the digital filtering and post-processing that determine the effective noise floor, the amount of trace noise, and, in some cases, the immunity to interfering signals. The trade-off for improved noise performance is slower sweep speed.
Port Power
Port power is less critical than IFBW or Averaging due to the excellent linearity of the VectorStar MS4640A Series VNA receivers. The AutoCal unit has an absolute maximum power limit of +10 dBm. The preferred calibration power is –10 dBm for improved accuracy at frequencies <100 MHz.
If power adjustments are required, any step attenuator settings must be selected before the calibration. Changes in the step attenuator settings alters both the RF match and the insertion loss in the measurements paths. Power can be changed after a calibration, but an attenuator change after a calibration invalidates the prior calibration.
Example Procedure
This example procedure assumes the VectorStar MS4640A Series VNA is equipped with the Option 070 – 70 kHz Low Frequency Extension and that only Frequency Start, Frequency Stop, Number of Points, and CW Mode settings are required.
1. Determine the values for the minimum setup parameters:
• Frequency Start: 70 kHz
• Frequency Stop: 70 GHz
• Number of Points: 200
• CW Mode: OFF
• Segmented Sweep: Not required
• IFBW: Defaults to 1 kHz
• Averaging: Defaults to no averaging
2. Power up the VectorStar and allow it to stabilize its internal temperature.
3. Navigate to the FREQUENCY menu:
• MAIN | Frequency | FREQUENCY
FREQUENCY Menu - Setting Initial AutoCal Parameters 
1 – FREQUENCY Menu
2 – Start (Frequency) Button before.
3 – Start Field Toolbar with 70.000 kHz set
4 – Start Button after set to 70.000 kHz
5 – Stop (Frequency) Button before
6 – Stop Field Toolbar with 70 GHz set
7 – Stop Button after set to 70 GHz
8 – # (Number) of Points (Frequency) Button before
9 – # of Points Field Toolbar with 200 points set
10 – # of Points Button after set to 200 points. Below, Step Size automatically calculated to 351.758442 MHz.
11 – Center (Frequency) Button automatically calculated to 35.00003500 GHz. Below, Span Button automatically calculated to 69.999930000 GHz.
4. On the FREQUENCY menu, click the Start frequency button (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #2).
• The frequency Start toolbar appears just below the icon toolbar (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #3).
5. Enter the required start frequency number value.
• For this example, set the start frequency value at 70.
6. Enter the required start frequency units.
• For this example, set the units to kilohertz by clicking kHz.
• The Start frequency field button now shows 70.000 kHz (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #4).
Note 
If the MS4640A Series VNA is not equipped with Option 070 – 70 kHz Low Frequency Extension, the lowest available starting frequency is 10 MHz.
7. On the FREQUENCY menu, click the Stop frequency field button (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #5).
• The frequency Stop toolbar appears (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #6).
8. On the Stop frequency toolbar, enter the required frequency number value and units.
• For this example, set the stop value at 70 and click the GHz units button.
• The Stop frequency button now shows 70.000000000 GHz (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #7).
9. The Center and Span display buttons show calculated values based on settings made above (See Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #7 above).
• The Center frequency field button shows a value of 35.000035000 GHz.
• The Span frequency field button shows a value of 69.9999930000 GHz.
10. On the Frequency menu, click the # of Points (Number of Points) button (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #8).
• The # of Points toolbar appears (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #9).
11. On the # of Points toolbar, enter the required number of points.
• In this example, set the # of Points to 200 and then click Enter on the toolbar.
• The # of Points field button shows 200 (Figure: FREQUENCY Menu - Setting Initial AutoCal Parameters – #10).
• The Step Size display button automatically calculates the step size of 351.758442 MHz.
12. Click the CW Mode toggle button so it is set to OFF.
13. The FREQUENCY menu appears with the new settings as shown below.
FREQUENCY Menu – After Settings
14. If optional parameters are required, do any of the following optional procedures described elsewhere in this manual:
• Frequency-Based Segmented Sweep.
• IFBW.
• Averaging
• Power and Attenuation
15. If no optional parameters are required, the AutoCal is ready to proceed.
• AutoCal - Full Two Port - Internal Through.