Antenna Measurements

This topic describes how to setup a Keysight Vector Network Analyzer (VNA) to make S21 measurements on an array of antennas. Measurements can be made on up to 100 antenna arrays (Ports) and up to 15 discrete frequencies

Measurement Sequence

1. The VNA is set to a start frequency.

2. As the antenna moves, the VNA responds to each external trigger signal by measuring an antenna port.

3. When all ports are measured, the VNA increments to the next frequency

4. Again the VNA measures all ports, and so forth until all ports are measured at all frequencies in the forward direction.

5. As the antenna begins moving in the opposite direction, the same sequence occurs, except the VNA decrements in frequency until all ports are measured at all frequencies and the VNA is set back to the original start frequency.

Once setup, only external trigger signals are sent to the VNA. After each trigger, measurement data is stored in internal VNA memory.

How to set up the VNA

1. On the System menu click Preset

2. On the Sweep menu point to Trigger then click Trigger

3. In Trigger Source click External

4. In Trigger Scope click Channel

5. Click OK

Forward Sweep

1. On the Trace menu click New Trace

2. Click S21 then Channel Number 1

3. On the Sweep menu point to Trigger then click Trigger

4. In Channel Trigger State check Point Sweep

5. Click OK

6. On the Sweep menu click Sweep Type:then Segment Sweep

7. Click OK

8. On the View menu point to Tables then click Segment Table

9. Do this 15 times - Sweep menu point to Segment Table then Insert Segment

10. For each Segment in the Segment table:

    1. Click State:and select ON

    2. Double click both START and STOP Frequency: (each new segment ascends in frequency)

    3. Double click Points: type Number of Ports (elements)

Reverse sweep

Repeat the following steps for each frequency: (up to 15)

• Increment the channel number (X) Starting with Channel 2

• Decrement the frequency (F)

1. On the Trace menu click New Trace...

2. Click S21 then Channel Number X

3. When a window contains four traces, check Create in New Window.

4. Click OK

5. On the Sweep menu point to Trigger then click Trigger

6. In Channel Trigger State check Point Sweep

7. Click OK

8. On the Sweep menu click Sweep Type:then Segment Sweep

9. Click OK

10. On the View menu point to Tables then click Segment Table

11. In the Segment table

    1. Click State:and select ON

    2. Double click both START and STOP Frequency F

    3. Double click Points: type Number of Ports (elements)