8 PCB Design Mistakes That Kill Wireless Performance
Wireless is one of those things that makes or breaks a product. Your PCB can be designed perfectly for functionality, but if the wireless doesn’t work reliably, your product is dead in the water.
So in this article, I’m going to show you the 8 most common PCB design mistakes that kill wireless performance.
Mistake #1: Poor antenna placement
The antenna is your product’s lifeline to the outside world. If it’s not placed correctly, nothing else you do will save you.
I’ve seen antennas placed right next to ground planes, crammed under plastic ribs, or even hidden under metal screws. It might look clean mechanically, but wirelessly it’s a disaster.
The antenna usually needs to be at the edge of the board, clear of surrounding metal, and oriented so the radiation pattern can actually escape the enclosure.
Place it in the wrong spot and your range may drop to half, or even less, of what it should be.
Another mistake I often see is designers putting the antenna in a convenient spot on the schematic and then leaving the mechanical team to figure out where it fits in the enclosure. That’s backwards.
The enclosure design and the antenna placement need to be thought through together from the start. Otherwise, you’ll end up with compromises that kill performance.
Think about how the user is going to hold or mount the product too. If a person’s hand is covering the antenna area, their body will absorb the signal and range will suffer.
Same with a product mounted on metal. The environment matters just as much as the PCB layout.
Mistake #2: Incorrect enclosure design
Now technically this one isn’t a PCB mistake, but your enclosure can absolutely make or break your wireless performance, and it does impact the PCB design, so I had to include it here.
Plastic enclosures affect wireless because different plastics have different dielectric constants. A higher dielectric constant can detune the antenna and reduce efficiency.
A fully metal enclosure is much tougher. A continuous metal shell acts like a Faraday cage.
Energy travels along the metal surface to ground instead of passing through it, so signals inside cannot radiate out.
That’s the same reason why a car is safe in a lightning storm. Not because the rubber tires insulate you from ground, but because the car’s metal body carries the current around you rather than through you.
If you must use a metal enclosure, you really have three choices.
First, use an external antenna. This is the best option. Route RF outside the enclosure with an RF connector and a whip, patch, or external PCB antenna.
That bypasses the cage completely and preserves range.
Second, create an RF window. Replace a localized area near the antenna with plastic. Keep this window as large as you can and place it directly in front of the antenna.
At 2.4 gigahertz the wavelength is about 12.5 centimeters. Openings that approach a meaningful fraction of that size improve transmission.
A few centimeters of plastic window is often doable and performs much better than just a few small holes.
This same principle is behind microwave ovens having doors with a fine metal mesh that you can see through.
The holes are tiny compared to the 12.5 microwave wavelength, so microwaves cannot escape. But, visible light, which has a much shorter wavelength, passes through the mesh easily.
Your final option for a metal enclosure is to use slits or perforations in the metal. This is the simplest mechanically since you don’t need a separate plastic part.
But it’s also the worst for performance. Narrow slots and small perforations are much smaller than the RF wavelength, so they only let a small amount of energy leak out. Expect a major hit to range and reliability.
And always tie a metal enclosure to ground. A grounded enclosure shields predictably and reduces self-interference.
A floating metal shell can behave unpredictably and re-radiate noise back into your own RF section.
Mistake #3: Ignoring antenna keep-out zones
Every antenna datasheet shows clear no-go areas around the antenna. These are zones where you cannot have copper pours, vias, or traces.
But I see designers ignore this all the time. A ground pour creeps into the antenna area, or a via drops through the keep-out.
The result is the antenna’s tuned frequency shifts, efficiency drops, and suddenly you’re radiating power where you don’t want it. Respect the keep-out zones. They are not suggestions.
It’s not only about keeping copper away either. Components themselves can mess with performance if they’re too close.
Even a plastic connector or a tall capacitor right in front of the antenna can distort the radiation pattern.
If you’re using a module with an integrated antenna, the manufacturer will often provide layout guidelines with a shaded keep-out box.
Follow those exactly. If you ignore them, you’re throwing away all the work that went into tuning that module.
Mistake #4: No controlled impedance routing for RF traces
The short trace from your RF chip to the antenna doesn’t look like much. But if it’s not designed as a 50 ohm controlled impedance line, you’re asking for trouble.
An impedance mismatch reflects power back into the chip instead of radiating it into the air. That means less range, less reliability, and more frustration.
The tricky part is that controlled impedance depends on your PCB stackup. It’s the trace width, the dielectric thickness, and the copper weight. You can’t just guess.
You need to calculate it or use your PCB manufacturer’s guidelines. Once the PCB is fabricated, you can’t fix it. So get it right before you order.
Mistake #5: Not providing an RF access point
Debugging wireless without access points is a nightmare.
If you don’t leave a place to hook up a test connector, you’ll have no idea if your problem is the antenna, the layout, or just interference from the environment. You’ll be flying blind.
A simple UFL connector or a solder pad for coax can make a huge difference during testing. Even if you never use it in production, you’ll be glad you had it during development.
Here’s why this matters. Let’s say your prototype has poor range. Without a test connector, you don’t know if the problem is the antenna itself or something upstream in the RF chain.
But with an RF connector, you can hook up a known good external antenna and instantly isolate the issue. If performance improves, you know the layout or enclosure is to blame.
If it doesn’t, the problem is likely with the chip, the matching network, or EMI.
Test connectors also let you measure things like return loss with a network analyzer or check output power with a spectrum analyzer.
These measurements are almost impossible without access. Skipping them often means guessing your way through wireless debugging, and that usually ends in frustration and redesigns.
By the way, inside my Hardware Academy you can get help from me and other experts on design challenges like these.
Mistake #6: Wrong ground plane design near the antenna
Ground planes are usually your friend, but not always. Done wrong, they can destroy antenna performance.
A common mistake is cutting out chunks of the ground plane near the antenna or failing to stitch vias properly. This can detune the antenna and create uneven current return paths.
I once reviewed a board where the designer thought more copper near the antenna was safer. Instead, it pulled the resonance down so far that the product wouldn’t even connect to Wi-Fi.
The key is consistency. You want a continuous, solid ground plane with plenty of stitching vias around the antenna feed line and matching network.
Sudden gaps or fragmented ground creates unpredictable currents and degrades radiation efficiency. Think of the ground plane as part of the antenna system, not just a background layer.
If you’re ever in doubt, follow the reference layout from the antenna or module vendor. They’ve already tested what works, and copying their ground strategy will save you headaches.
Mistake #7: Skipping matching network components
That little PI network, which is just a couple of capacitors and an inductor between the RF chip and the antenna, is not optional.
Antennas are never perfect. Their exact impedance depends on your PCB, your enclosure, and even your assembly.
Without a matching network, you’ll have no way to fine-tune them. At the very least, leave space in your layout for the components.
You don’t have to populate them right away, but if you don’t have the footprints, you’ve removed your only tuning option.
I once helped a client whose product had terrible Bluetooth range. The fix was simple, add a matching network and tune it. But since their layout had no space for it, they had to do a complete redesign. That mistake cost them months.
Keep in mind that every time you change the enclosure, change the PCB stackup, or even move the antenna slightly, the tuning may need to be redone.
A matching network gives you that flexibility without having to start from scratch each time.
Mistake #8: Noise coupling into the RF section
Your wireless chip might look fine on paper, but in the real world it’s surrounded by noise sources like switching regulators, digital clocks, and high-speed buses.
All of these create interference that couples into the RF section and kills sensitivity.
Suddenly, your range drops to half, or your product fails radiated emissions testing.
The problem comes from two angles. First is system-level EMI: noisy supply rails, poorly routed return paths, and fast digital edges that radiate into the RF section.
Second is physical placement. If you squeeze your RF section right next to a buck regulator or high-speed bus, you’ve practically guaranteed interference.
Treat the RF section as its own quiet zone. Keep noisy circuits at a distance, filter your supplies, and don’t be afraid to use shielding if needed.
Even a small oversight, like running a clock trace under the antenna feed, can wipe out weeks of careful design work.
