Hi,
I currently noticed my research setup has different voltage standing wave ratio (VSWR) for the RF antenna (<1.5:1) and front-end (<=2:1). Please recommend a component to add inline to possibly fix the mismatch issue.
Thank you.
Hello @jotshaw,
Are the VSWR values referenced in your post measurements you have taken or are they specifications for the RF antenna and front-end devices in your test setup? Do the RF antenna and front-end have the same impedance?
Hi @ScottRaeker , thanks for the reply.
The setup has different VSWR for the RF antenna (<1.5:1) and front-end (<=2:1.5). Please recommend a component to add inline to possibly extend the antenna’s VSWR to (<=2:1) or front-end (<=2:1). The impedance for both is 50 ohms (same).
Regards,
John Bagshaw
Hello @jotshaw,
My understanding, based on the VWSR article VSWR, is that a VSWR of 2 or less is considered a good antenna match so seems like your setup should be OK since both are 50 ohms impedance.
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@jotshaw I agree with Scott. My previous work “in the field”, 2:1 would cause only a minimal loss of performance on the system. Field tuning (trimming) of the antenna length might get it closer to a perfect match.
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Not my specialty, but I don’t believe one tries to match VSWR specs between devices, but rather one should try to minimize VSWR in a system (with 1:1 being perfect, with no reflected waves). The VSWR numbers you specify probably refer to the worst-case values measured under some set of specified conditions. To minimize VSWR, one must match the impedances of the antenna and your front end device. However, having them both be specified at 50 Ohms would only get you part way, as the characteristics of the cable, board trace, and/or connector used all affect the actual impedance of the system.
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Thanks for the replies.
I tried the connections with another RF antenna within the VSWR of the front-end and it worked as expected.
That led me to finding out how to adjust the VSWR for the front-end to fall in the range of the RF antenna.
As the impedance are the same, a promising solution might be how to reduce/trim the VSWR of the front-end to fit the antenna’s VSWR.
Someone suggested pi and T filtering.
Your thoughts and recommendations are highly appreciated.
Regards,
John Bagshaw