Designing a PCB for a Pet or Animal Tracker: What the Form Factor Actually Constrains

A GPS/GNSS tracker board for a bench-top prototype and one meant to live on a collar for months are, electrically, similar circuits. Mechanically and electromagnetically, they're not the same problem at all. Everything below is driven by one fact: the board has to be small, has to sit close to a moving animal's body, and has to survive outdoors without anyone opening it up to fix a mistake.

Start with the constraint, not the chip

It's tempting to start a tracker design by picking a GNSS module and a radio and laying out a board around them. In practice, the enclosure dimensions, the strap or tag-clip geometry, and the target battery size usually get fixed first, because they're the hardest constraints to change later — and the board has to fit inside whatever envelope they leave. Component selection follows from that envelope, not the other way around.

Antenna placement is usually the hardest part

This is where most of the engineering difficulty in a wearable tracker actually lives, and it's easy to underestimate before you've laid one out.

• GNSS antenna type. A ceramic patch antenna gives reliable performance with a known ground-plane keep-out area, but it has a minimum footprint that competes directly with everything else on a small board. An embedded PCB trace or chip antenna can be smaller and cheaper, but is more sensitive to layout mistakes and to whatever's near it — including the battery, metal snap closures on a collar strap, or a conductive enclosure.
• Body loading. An antenna mounted close to an animal's body — especially a larger animal — experiences RF loading from that body that a free-space antenna datasheet doesn't account for. This can detune the antenna and reduce both sensitivity and radiated efficiency. The practical response is to validate antenna performance in a mounting position and orientation close to the real use case, not just on an open bench.
• Keep-out zones and desense. The GNSS antenna needs clearance from digital switching noise and from the battery. If there's a second radio on the same board — LoRa, LTE-M, or BLE — it needs its own keep-out, and ideally physical separation from the GNSS antenna, so the second radio's transmit power doesn't desense the (much more sensitive) GNSS receive path.

Stack-up and layer count

A simple low-data-rate design can sometimes get away with two layers. In practice, once you're running a GNSS front end, a second radio, battery charging circuitry, and sensor interfaces on the same small board, a four-layer stack-up with a dedicated, unbroken ground plane under the RF front end is usually the more reliable choice — it gives the GNSS section a clean reference plane and keeps noisy digital traces from running directly underneath sensitive RF.

Power supply and battery protection on the board

For a primary (non-rechargeable) lithium cell, the power path is comparatively simple: a low-dropout regulator or a small buck-boost converter, sized for the current the GNSS and radio draw during their active bursts, not just their sleep-state draw.

For a rechargeable lithium-ion or LiPo cell, the board needs a battery protection IC — overcurrent, overvoltage, and undervoltage lockout — as a non-negotiable safety component, plus a charging IC if the device recharges over USB, a pogo-pin dock, or solar. The regulator topology choice (LDO versus buck-boost) is itself a trade-off: an LDO is simpler and lower-noise but wastes the voltage difference as heat, which matters more at the higher currents a GNSS fix or a radio transmission briefly demands.

Component selection: module vs. discrete

A pre-certified GNSS-plus-radio module gets a design to a working prototype faster, carries pre-existing FCC/CE radio certification, and reduces RF layout risk — at a size and per-unit cost premium compared to discrete components. A discrete chipset approach can be smaller and cheaper at volume, but it shifts the RF layout expertise and the certification process onto the project. Which one makes sense depends on the production volume, timeline, and how much RF design margin the team wants to carry — there isn't a universally correct answer.

Designing for the enclosure, not just the board

The board outline, mounting hole positions, and connector placement all need to be decided alongside the enclosure, not after it. Collar- or tag-mounted enclosures often call for potting or conformal coating around the board to manage moisture and vibration — but any specific water- or dust-ingress rating (an IP rating, for example) has to be validated by actual testing on the finished, assembled device. It isn't something a board design can claim on its own, independent of the enclosure it ends up in.

Designing for manufacturability early

A board that works perfectly on the bench can still be painful to build at any volume if panelization, test points for in-circuit or functional test, and component placement for pick-and-place weren't considered during layout. A design-for-manufacturability pass before a layout is finalized — not after the first prototype run — is cheap insurance against rework later.

None of this is exotic by embedded-hardware standards. What makes a tracker PCB design hold up in the field is usually how early the antenna placement, enclosure integration, and manufacturability questions were treated as layout inputs, rather than problems to debug after the first batch of boards comes back.