WEARABLE TECHNOLOGY
Design considerations when selecting timing components & wireless antennas for wearable applications
By Lawson Williams, Roshan Khobragade and John Ivants, Raltron
Antennas need to hold up under use
Designing wireless antennas for wearable devices is very different from designing antennas for phones, routers, or other conventional electronics because the antenna must operate while it is placed directly on, or very near, the human body. The attached source material emphasises that the body acts as a lossy dielectric, meaning frequency.
One of the most important design considerations is body proximity. In wearables such as smartwatches, rings, glasses, medical patches and smart clothing, the antenna no longer operates in free space. Instead, designers must account for the high water content of human tissue, which can absorb a large portion of the signal and alter performance. This is why wearable antennas must be tested in realistic on-body conditions rather than only in laboratory free-space measurements.
Size and form factor are another major challenge. Wearable products offer very limited space, yet they often need to support wireless standards. Designers often use rings, wristbands, helmets and eyewear. In many cases, the antenna must also support multiband operation, which adds complexity because a single small device may need to handle several frequencies at once. Material selection is equally critical. Because wearables bend, move and are exposed to sweat, washing, rain and temperature The source materials highlight the use of conductive fabrics, silver-coated nylon, stainless-steel thread, polyimide-based antennas for compact devices. These materials help the antenna survive repeated movement and environmental stress while remaining lightweight and comfortable for the user.
16 MAY 2026 | ELECTRONICS FOR ENGINEERS time.
also pay attention to load capacitance, drive level and equivalent series
design process. Wearable antennas must energy into body tissue. At the same time, which is a serious drawback for small devices reason, designers aim to maximise radiation power and sometimes direct energy away from the body with grounding or shielding techniques.
More than frequency and small footprint
Design engineers selecting timing components for wearable devices need to think beyond frequency and footprint when choosing between tuning fork crystals and megahertz crystals. Several practical concerns directly affect battery life, accuracy and long-term reliability in compact, body-worn electronics.
An initial key decision is how to use 32.768 kHz tuning fork crystals for the real-time clock and low-power “heartbeat” of the system. Because this frequency is in the kilohertz range, it runs at roughly one-thousandth the frequency of a typical 32 MHz crystal, allowing the circuit to operate at extremely low power and enabling watches and wearables to run for years on a small battery. The crystal’s temperature–frequency curve is typically with body-worn devices where human body heat keeps the crystal near its turnover temperature, minimising drift in date and
increases and their allowable drive level decreases, so a legacy oscillator circuit that worked with a larger can-type crystal may not start reliably with a tiny surface-mount device. A common mistake is downsizing the crystal without adjusting the load capacitors, which starves the crystal of negative resistance and leads to marginal startup, especially at temperature extremes or low battery voltage.
miniaturisation trends create additional trade-offs. As the package and quartz blank get thinner and smaller, the minimum and the maximum safe drive level drops, so overdriving a small MHz crystal can cause excess power consumption, frequency wearables, where every microamp counts, designers must consciously limit drive level while still providing adequate margin for startup and frequency stability. and related lithographic techniques allow very small tuning-fork and MHz crystals with precise geometries, but they also mean that only a handful of manufacturers supply the tiniest sizes, and the crystals can be mechanically more delicate. Design engineers should engage with crystal experts early, at the schematic and component-selection stage, to choose the negative-resistance margins and ensure that the mechanical package and mounting are compatible with the wearable’s form factor. By treating crystals as critical design elements rather than generic commodities, engineers can achieve longer battery life, better timing accuracy and more robust operation in modern wearable devices.
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