Digital & Communication Technology Real antennas aren’t 50 ohms
Ronald Wilting, CEO at Forefront RF, explains why this matters for the next generation of connected devices
For decades, the RF industry has lived by a simple assumption: everything is 50 ohms. Filters, duplexers, amplifiers, switches; almost every component in a mobile front-end is designed, tested, and validated under ideal 50 Ω lab conditions. This standardisation made engineering easier. It simplified test benches, enabled datasheet comparability, and allowed handset designers to mix and match components from different vendors. However, there’s one problem with this model: Real antennas are rarely 50 Ω. Not in free space. Not in the hand. Not in a smartwatch chassis. Not on a crowded IoT board. Moreover, as devices continue to shrink, band counts continue to multiply, and power budgets tighten, the cost of idealising them as 50 Ω keeps rising.
Antenna impedance is a moving target, constantly shifting with frequency, user grip, head and body proximity, chassis materials, ground plane size and manufacturing tolerances. In real devices, antenna impedance regularly sweeps around a VSWR of 2:1 to 4:1.
26 December/January 2026
This is not a corner case; it is the dominant operating condition. Yet almost all front-end components are still measured and specified at 50 Ω. Indeed, this widening gap between lab conditions and real-world antenna behaviour has become one of the most overlooked bottlenecks in mobile RF design.
SAW duplexers, the workhorses of low-band RF front ends, are particularly sensitive to mismatch. To illustrate this, we measured a Band 28 SAW duplexer at five impedance points: one at 50 Ω and four evenly spaced around a 3:1 VSWR circle. This is the environment a real antenna presents during everyday use.
These were the results:
Under ideal 50 Ω conditions, insertion loss sits around 2 dB.
Under realistic 3:1 mismatch conditions, insertion loss increases by several dB, depending on the phase angle.
Passbands warp and ripple. Isolation degrades.
In other words, the duplexer’s loss increases dramatically, even though the antenna hasn’t changed at all. This is the missing piece in many system evaluations. Degraded efficiency is often blamed on the antenna, but a significant portion originates inside the duplexer itself.
Around 10 years ago, companies like Qualcomm and EPCOS (TDK) introduced adaptive antenna tuning to combat mismatch effects. These circuits dynamically adjust the antenna to pull it closer to 50 Ω under varying conditions, providing important benefits including:
Higher receive sensitivity Less wasted PA power Improved user experience in weak-signal scenarios
However, there are also fundamental limitations: more components, complex control software, larger footprint, increased power consumption, and most importantly, they do not solve the root cause. They attempt to pull the antenna toward 50 Ω rather than making the duplexer tolerant of real antenna impedance. This works, up to a point, but in wearables, IoT devices, and other small form factor platforms, the space and power budgets for extensive tuning networks are rapidly shrinking.
One emerging direction is to focus, not on forcing the antenna to behave like 50 Ω, but on increasing the duplexer’s ability to dynamically adapt to real-world impedance conditions. A tunable duplexer achieves this by adjusting its impedance transformation dynamically, thus maintaining stable insertion loss even as the antenna moves through a wide range of operating states.
Components in Electronics
www.cieonline.co.uk
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