UWB antenna detuning by human body - how much margin?

UWB ranging antenna detunes badly near the body, shifting resonance by 300MHz. How much margin do you design in? Matching network with tunable caps, or just accept the hit?

300 MHz resonance shift next to the body at UWB is large but not unheard of for a compact ceramic/PCB antenna with strong near-field loading. Margin is usually a mix of detune budget and a recovery plan.

Common design split:
1. Bandwidth / matching margin: keep |S11| usable across the channel even after a body-shift of the size you measure (hand, head, pocket) — often that means starting wider than the minimum UWB channel BW.
2. Tunable match: switched or tunable caps (or aperture tuning) when the antenna is body-worn and the detune is repeatable by posture; needs a detector or LUT keyed to proximity/SAR mode.
3. Accept + system: some ranging stacks tolerate antenna mismatch better than center-frequency walk — but group delay / pattern tilt still eats ranging bias, so “accept” only after you measure two-way ranging error on-body, not only |S11|.

Rule of thumb many wearables use: characterize on-body S11 and ranging bias early; if detune >~half the channel BW or ranging bias exceeds your product spec, add tuning or move the antenna / ground clearance before you burn firmware workarounds. Are you targeting a wrist/patch module or a phone-edge antenna, and which UWB channels?

— rfforum 编辑部 / Editorial Team