How to Design a PCB Antenna Types, Calculations & Best Practices

I’ve been designing wireless circuits for over a decade now, and I can tell you that the PCB antenna is often the most underestimated component in any RF design. Engineers spend weeks perfecting their microcontroller code or optimizing power consumption, only to slap on an antenna as an afterthought. The result? Poor range, failed EMC tests, and frustrated customers.

In this guide, I’m going to walk you through everything you need to know about PCB antenna design—from selecting the right type for your application to calculating dimensions and avoiding the rookie mistakes that cost me countless prototype revisions early in my career.

What is a PCB Antenna?

A PCB antenna (also called an embedded antenna, on-board antenna, or printed antenna) is an antenna whose radiating element is etched directly onto the printed circuit board using copper traces. Instead of requiring a separate antenna component or external whip, the antenna becomes part of the PCB itself.

This approach has become incredibly popular in modern electronics for several reasons:

• Cost reduction: No separate antenna component means lower BOM costs
• Space savings: The antenna integrates directly into the board layout
• Manufacturing simplicity: Standard PCB fabrication processes work fine
• Design flexibility: Custom shapes can fit almost any enclosure

The trade-off? PCB antennas typically have lower efficiency and narrower bandwidth compared to dedicated external antennas. But for most IoT, Bluetooth, Wi-Fi, and short-range wireless applications, that trade-off is perfectly acceptable.

Understanding How a PCB Antenna Works

The Relationship Between Wavelength and Antenna Size

The most important equation in antenna design relates wavelength to frequency:

λ = c / f

Where:

• λ (lambda) = wavelength in meters
• c = speed of light (299,792,458 m/s, approximately 3×10⁸ m/s)
• f = frequency in Hz

For a 2.4 GHz Wi-Fi antenna: λ = (3 × 10⁸) / (2.4 × 10⁹) = 0.125 meters = 125 mm. Most practical antennas operate at fractions of this wavelength—typically half-wave (λ/2) at 62.5 mm or quarter-wave (λ/4) at 31.25 mm for 2.4 GHz.

The Ground Plane as the “Other Half”

Here’s something that trips up many new RF designers: a quarter-wave monopole antenna isn’t really just a single element. The PCB’s ground plane acts as a mirror, creating the “missing half” of what’s essentially a dipole antenna. This means your ground plane size and shape directly affect antenna performance.

A ground plane that’s too small will shift the resonant frequency, reduce radiation efficiency, and create unpredictable radiation patterns. For optimal performance, your ground plane should be at least λ/4 (one quarter wavelength) in the dimension parallel to the antenna.

Impedance Matching: The 50-Ohm Standard

Almost all modern RF components are designed around a 50-ohm characteristic impedance. Your antenna, transmission line (feed trace), and RF circuitry all need to match this impedance. The 50-ohm standard became industry practice because it offers a reasonable balance between minimum cable loss (30 ohms) and maximum power handling (77 ohms).

Types of PCB Antennas

Selecting the right antenna topology is the first critical decision in your design. Each type has distinct characteristics that make it suitable for specific applications.

Monopole PCB Antenna

The monopole is the simplest PCB antenna type—essentially a straight trace extending from the ground plane edge. It requires a quarter-wavelength of trace length and relies entirely on the ground plane as its counterpoise. It features an omnidirectional radiation pattern (donut-shaped), simple design, and typical gain of 1-3 dBi. Best for Wi-Fi routers, Bluetooth devices, remote controls, and general IoT sensors.

Dipole PCB Antenna

A dipole consists of two equal-length elements fed at the center. On a PCB, this typically means two traces separated by a small gap. It features a bidirectional radiation pattern, balanced feed, less ground plane dependency, and typical gain of 2-3 dBi. Best for TV broadcasting receivers, Wi-Fi access points, and applications requiring balanced feeds.

Inverted-F Antenna (IFA)

The IFA gets its name from its shape—it looks like an upside-down letter F. It features a compact footprint, lower profile than monopoles, built-in matching through shorting pin, and typical gain of 1-2.5 dBi. Best for smartphones, tablets, space-constrained wearables, and compact IoT modules.

Meandered Inverted-F Antenna (MIFA)

The MIFA is a further evolution of the IFA where the horizontal element is folded in a zigzag pattern. It features very compact design, reduced efficiency compared to straight IFA, sensitivity to nearby components, and typical gain of 0.5-2 dBi. Best for wireless mice, presenters, BLE beacons, and ultra-compact wearables.

Patch (Microstrip) Antenna

Patch antennas consist of a flat rectangular or circular conductive element on one side of the PCB with a ground plane on the opposite side. They feature directional radiation, higher gain (4-8 dBi typical), narrow bandwidth, and larger footprint. Best for GPS receivers, automotive radar, satellite communications, and directional links.

Loop Antenna

Loop antennas form a closed conductive path, sensitive to magnetic fields. They’re very compact for low frequencies, often require a resonating capacitor, and have typical gain of -2 to 1 dBi. Best for NFC, RFID readers/tags, AM radio, and magnetic field sensors.

PCB Antenna Comparison Table

Antenna Type	Size	Bandwidth	Gain (dBi)	Ground Plane	Complexity	Best For
Monopole	Medium	Medium	1-3	Yes	Low	General IoT
Dipole	Large	Medium	2-3	Partial	Low	Wi-Fi AP
IFA	Small	Medium	1-2.5	Yes	Medium	Smartphones
MIFA	Very Small	Narrow	0.5-2	Yes	Medium	Wearables
Patch	Large	Narrow	4-8	Yes	Medium	GPS, Radar
Loop	Very Small	Narrow	-2 to 1	No	Low	NFC, RFID

PCB Antenna Design Calculations

Now let’s get into the math. I’ll walk you through the essential calculations with practical examples.

Step 1: Determine the Operating Frequency

Your target frequency determines nearly everything else. Common ISM bands include:

Band	Frequency	Common Applications
Sub-1 GHz	433, 868, 915 MHz	LoRa, Zigbee, remotes
2.4 GHz	2400-2483.5 MHz	Wi-Fi, Bluetooth, BLE
5 GHz	5150-5850 MHz	Wi-Fi 5/6, 5G NR
GPS L1	1575.42 MHz	GPS receivers

Step 2: Calculate the Wavelength

Using the basic formula, calculate the wavelength in free space. But electromagnetic waves travel slower in a PCB substrate than in free space. You need to account for the effective dielectric constant:

λ_eff = λ₀ / √εr_eff    where    εr_eff ≈ (εr + 1) / 2

For FR4 with εr = 4.4, εr_eff ≈ 2.7, so √εr_eff ≈ 1.64. A 2.4 GHz quarter-wave antenna on FR4: λ₀ = 125 mm, λ_eff = 76 mm, λ/4 ≈ 19 mm.

Antenna Length Reference Table

Frequency	λ₀ (Free)	λ/4 (Free)	λ/4 (FR4)	Typical Length
433 MHz	693 mm	173 mm	106 mm	100-110 mm
868 MHz	346 mm	86.5 mm	53 mm	50-55 mm
915 MHz	328 mm	82 mm	50 mm	47-52 mm
2.4 GHz	125 mm	31.25 mm	19 mm	18-20 mm
5.8 GHz	52 mm	13 mm	7.9 mm	7-8 mm

Note: Actual lengths vary based on substrate thickness, trace width, and proximity to components. Always verify with simulation.

PCB Antenna Layout Best Practices

After designing hundreds of wireless products, here are the layout rules I always follow.

Antenna Placement

Rule #1: Always place the antenna at the PCB edge or corner. This is probably the most important layout decision you’ll make. An antenna placed in the middle of a board, surrounded by ground plane and components, will perform terribly. The corner works best because it provides clearance in five spatial directions and maximum distance from noisy digital circuitry.

Rule #2: Extend the antenna beyond the main PCB if possible. Many successful designs (like the ESP32 modules) have the antenna portion extending past the main board outline. This gives maximum radiation freedom.

Keep-Out Zones and Clearance

Every antenna requires a copper-free zone around and below it. This applies to ALL layers of your PCB.

• 2.4 GHz antennas: Minimum 15 mm clearance from ground plane edge
• Sub-1 GHz antennas: Minimum 20-30 mm clearance
• Lateral clearance: 3-5 mm from antenna edges on all layers

Keep out of the clearance zone: all copper (traces, pours, vias), metal components (USB, shields), large passive components, batteries, LCDs, and mounting hardware.

Ground Plane Design

The ground plane is literally half of your antenna system. Use a solid, continuous ground plane (don’t slice it up with traces). For multi-layer boards, stitch the ground layers together with via fences along the edge. Keep the ground plane edge parallel to monopole antennas, and size the ground plane to at least λ/4 in the critical dimension.

50-Ohm Feed Line Design

The transmission line connecting your RF IC to the antenna must maintain 50-ohm characteristic impedance. Coplanar Waveguide with Ground (CPWG) is the preferred approach for most PCB antennas. For a typical 4-layer, 1.6 mm FR4 board with 1 oz copper: a 50-ohm microstrip is approximately 2.9 mm wide. Always use an impedance calculator to get exact dimensions for your stackup.

Common PCB Antenna Design Mistakes

I’ve made all of these mistakes at some point. Learn from my pain.

Mistake #1: Ignoring the Ground Plane

The most common mistake: designing a beautiful antenna, then placing it on a tiny evaluation board with an inadequate ground plane. The fix: Size your ground plane appropriately from the start. For sub-1 GHz, you need at least 80-100 mm of ground plane length.

Mistake #2: Copper in the Keep-Out Zone

Designers carefully create keep-out zones on the top layer, then route power traces right under the antenna on inner layers. The fix: Create keep-out zones that apply to ALL copper layers.

Mistake #3: Skipping Simulation

“It worked on the reference design” is famous last words. Your board isn’t the reference design. The fix: Simulate your specific layout with your enclosure and components using tools like HFSS or CST.

Mistake #4: Forgetting the Enclosure

An antenna that works perfectly on the bench may fail completely when mounted in a plastic enclosure. Plastic cases shift the resonant frequency downward (typically 50-200 MHz for 2.4 GHz antennas). The fix: Test with the final enclosure and leave room in your matching network to compensate.

Read more PCB Tech Posts:

PCB Antenna Impedance Matching in Detail

Even well-designed antennas rarely hit exactly 50 ohms. Real-world factors like enclosure proximity, battery placement, and PCB manufacturing variations all shift the impedance. Understanding how to match your antenna is crucial for achieving optimal performance.

When You Need a Matching Network

You need impedance matching when your antenna’s measured impedance differs significantly from 50 ohms, your enclosure or nearby components detune the antenna, you’re using a chip antenna (almost always requires matching), or the antenna was designed for a different ground plane size. The general rule: if your return loss (S11) is worse than -10 dB across your operating band, you need matching.

Pi-Network and L-Network Matching

The Pi-network is the most common matching topology for PCB antennas—two shunt capacitors with a series inductor. It can match a wide range of impedances and offers filtering capability. The simpler L-network uses only two components and works well when impedance transformation isn’t too extreme (within 2:1 of 50 ohms).

Component Selection for RF Matching

Use high-Q ceramic capacitors (COG/NPO dielectric) and avoid X7R/Y5V which vary with frequency. Watch for self-resonant frequency (SRF). For inductors, use thin-film or multilayer chip types rather than wire-wound. Check Q-factor at your operating frequency. Typical 0402 components for 2.4 GHz: Murata GJM15 series capacitors, Murata LQW series inductors.

PCB Material Selection for Antenna Design

The choice of PCB substrate material significantly impacts antenna performance. While many designers default to FR4 for cost reasons, understanding when to use specialized materials can make the difference between a working product and one that fails certification.

FR4 vs High-Frequency Laminates

Standard FR4 is adequate for most applications up to about 3 GHz. Its dielectric constant (εr) ranges 4.2-4.5 with loss tangent of 0.02. The main challenge is consistency—εr can vary ±10% between batches. High-frequency laminates like Rogers RO4003C (εr: 3.38, tan δ: 0.0027) offer much better consistency and lower losses at 3-5× the cost. Consider upgrading when operating above 5 GHz, when efficiency requirements exceed 70%, or when manufacturing variation causes yield issues.

EMC and Regulatory Considerations

Designing a great antenna is only part of the challenge. Your product must also pass regulatory testing for the markets you’re targeting. FCC Part 15.247 covers spread spectrum devices (Wi-Fi, Bluetooth) in the US, while CE marking requires ETSI EN 300 328 for 2.4 GHz band in Europe.

Tips for passing regulatory testing:

• Filter harmonics—even a perfect 2.4 GHz antenna radiates at 4.8 GHz and 7.2 GHz if your transmitter generates harmonics
• Shield sensitive circuits and keep noisy digital circuits away from the antenna
• Use proper grounding—poor ground design causes common-mode emissions
• Design for -3 dB below regulatory limits to account for production variation

PCB Antenna Simulation and Testing

Simulation Software Options

Software	Vendor	Solver	Price	Learning
Ansys HFSS	Ansys	FEM	$$$$$	Steep
CST Studio	Dassault	FDTD/FEM	$$$$$	Moderate
FEKO	Altair	MoM	$$$$	Moderate
openEMS	Open Source	FDTD	Free	Steep

PCB Antenna Design Resources

Here are the resources I use regularly for PCB antenna design.

Calculators and Tools

• Pasternack Patch Calculator – pasternack.com/t-calculator-microstrip-ant.aspx
• Saturn PCB Toolkit – saturnpcb.com/pcb_toolkit/
• AppCAD by Keysight – keysight.com/find/appcad
• RF Tools Smith Chart – rf-tools.com/smith-chart

Reference Designs and Application Notes

• Texas Instruments AN-1811 – PCB trace antenna reference designs
• Texas Instruments SWRA117 – 2.4 GHz PCB antenna designs
• STMicroelectronics AN5129 – Low-cost PCB antenna for STM32WB
• Nordic Semiconductor nAN-24 – Antenna design for nRF devices
• Infineon/Cypress AN91445 – Antenna design and RF layout guidelines
• Espressif Hardware Design Guidelines – ESP32/ESP8266 antenna design

Frequently Asked Questions (FAQs)

What is the difference between a chip antenna and a PCB antenna?

A chip antenna is a pre-manufactured, surface-mount component (usually ceramic) that you solder onto your PCB. A PCB antenna is etched directly into the copper layers of the PCB itself. Chip antennas are faster to implement but more expensive and cannot be tuned by changing dimensions. PCB antennas are cheaper, require more design expertise, and can be optimized for specific applications.

How do I calculate the length of a PCB antenna?

The basic formula for a quarter-wave monopole antenna is: L = (c / f) × (1 / 4) × (1 / √εr_eff). For 2.4 GHz on FR4 with εr_eff ≈ 2.7, L = (3 × 10⁸ / 2.4 × 10⁹) × 0.25 × (1 / 1.64) ≈ 19 mm. Always add 5-10% extra length to allow for trimming during tuning.

Why does my PCB antenna need a ground plane?

For monopole and IFA-type antennas, the ground plane acts as the second half of the antenna. It creates an “image” of the quarter-wave element, effectively forming a half-wave dipole. Without an adequate ground plane, resonant frequency shifts unpredictably, radiation efficiency drops significantly, and radiation pattern becomes distorted.

Can I use any PCB material for antenna design?

Technically yes, but material choice significantly affects performance. FR4 (standard PCB material) works fine for 2.4 GHz and below but has higher loss at 5 GHz and above. High-frequency laminates (Rogers, Taconic) offer lower loss and more consistent properties but are 3-10× more expensive. For most IoT and consumer electronics, standard FR4 works adequately up to 6 GHz.

How do I test a PCB antenna without expensive equipment?

While professional testing requires a VNA and anechoic chamber, you can do basic validation with: (1) NanoVNA – low-cost ($50-150) vector network analyzer for S11 measurement, (2) Range testing – measure actual communication distance, (3) Spectrum analyzer – check radiation frequency, (4) Comparison testing – test against a known-good reference antenna. For production validation, send samples to an antenna test lab (typical costs $500-2000).

Conclusion

Designing a successful PCB antenna requires balancing multiple factors: electrical performance, physical constraints, manufacturing cost, and real-world operating conditions. The key principles to remember: start with the right topology, size your ground plane appropriately, maintain proper keep-out zones, design for tunability, simulate before fabrication, and test in the actual enclosure.

PCB antenna design is one of those skills that improves dramatically with experience. Each project teaches you something new about the interplay between theory and practice. Don’t get discouraged if your first designs need multiple iterations—even experienced RF engineers rarely nail it on the first try.

The best PCB antenna designs come from engineers who understand both the electromagnetic fundamentals and the practical realities of manufacturing, cost, and system integration. Keep experimenting, keep measuring, and keep learning.