In this thread I want to demonstrate the use of SVA1015X for analysis of a number of antennas I have hoarded over the years.
In another thread I built and tuned a 315 MHz J-Pole antenna to get 500m range with a key-fob remote and in doing so learned getting maximum antenna emissivity at the fundamental frequency was paramount to getting good results.
https://www.eevblog.com/forum/rf-microwave/antenna-project-log/Recent demonstrations of SVA1015X to customers doing various wireless projects have shown the 'off the shelf' commercial antennas they have selected couldn't be considered as optimal for their intended frequencies and their wireless range expectations are therefore generally not met.
As antennas have the useful property of reciprocity we can sweep them with a signal and find their transmission properties which are also very close to their receptive properties. We can get basic information with a spectrum analyser and a reflection bridge but not the degree of info that can be acquired from a VNA.
2.4 GHz SMA WiFi antenna analysis
While I can't fully sweep a 2.4 GHz antenna with a 1.5 GHz VNA let's look at a full 1.5 GHz sweep and see what info arises.
The subject:
It should be noted that this antenna connected directly to the S11 port has its performance impacted by adjustments of the VNA due to proximity effects and it need be connected more remotely to reduce them for accurate repeatable measurements.
Emissivity, aka Log Mag
Where we look for the largest dip in the trace that represents the greatest absorption of energy from the feedline/transmitter and the frequencies this might occur at.
Interestingly here it's at ~1/2 of 2.4 GHz that this antenna is designed for.
Well could this antenna be useful at 1.28 GHz ?
We need to check the SWR to look for efficiencies:
Results of 1.6 and 1.2:1 indicate it might useful however how will they match the optimal 50 Ohm impedance we always seek ?
A Smith chart will give us the info of impedance and inductive or capacitive match/mismatch.
Overlay all these results using a trace for each measurement and we can see the full picture.
We need remember all these results are with a full 100 Khz-1.5 GHz sweep which is not what we would normally do.
Instead we would narrow the sweep considerably and set the center frequency to the frequency of interest.
Next up, some antennas under 1 GHz.