Flexible PCB Antenna: The Ultimate Guide

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Oakley Mae

The world is going through a series of changes, and with it comes new innovative technologies and devices like a flexible PCB antenna.

These devices are smaller with impressive wireless capabilities. Surprisingly, they offer an almost plug ‘n’ play integration and are pre-tuned to make it easy to add wireless capabilities. 

Moreover, flexible PCB antennas are designed with materials that withstand mechanical deformations like twisting and bending.

Furthermore, you can use antennas for wearable sensing systems, implantable applications, radio frequency identification, and onboard communication.

But there is more to flexible PCB antennas than what you already know. 

This article explores flexible PCB antennas’ benefits, applications, and design.

Table of Contents

What’s A Flexible PCB Antenna

A curled flexible PCB

(A curled flexible PCB)

Flexible PCB antennas, or FPCB antennas, are low-profile, flexible, economical antennas that find a major application in the wireless industry.

This antenna is designed with a polyimide flexible PCB and a conductive copper material. Surprisingly, you can use it to develop different antennas, including dipoles and printed F antennas. 

Moreover, the antenna comes with a coaxial cable where you connect your circuit.

Besides being flexible, the antennas are highly efficient and have reliable characteristics that come in handy when designing wearable and small IoT devices

However, be very careful with flexible antennas since some might lose efficiency when you bend or fold them too far. 

Benefits of FPCB Antennas

Someone holding FPCB

(Someone holding FPCB)

FPCB antennas present some benefits you’ll never find in other products. Check them out below:

Integration Flexibility

With flexible PCB antennas, you’ll get integration flexibility like no other. Since they can easily bend and fold, you can place them coplanar, horizontally, or vertically on the host circuit board.

Moreover, they boast high efficiency and performance levels, making them comparable to SMD antennas. Furthermore, these PCBs aren’t restricted by ground and can operate effectively on a flat, curved, or folded surface. 

Plug In and Play

You can customize these antennas using a bespoke cable length for easy connection to a module and host circuit board. However, note that increasing the cable length will affect the antenna performance. 

No Ground Plane

The ground plane is afforded SMD antennas, thus directly impacting performance. Fortunately, FPCB antennas face no such issues. The flexible circuit board is specifically designed for the antenna you install on it.

Therefore, it presents fewer integration steps, high-performance levels, and saves space. 

Simple Integration

As we highlighted, flexible circuit boards are designed with simple connection systems and flexible characteristics that maTTheate into devices and syst with SMD antennas with SMD antennasems.

Surprisingly, you can bend or have them vertically or horizontally without affecting their performance. Therefore, designers and manufacturers can position them anywhere they see fit. 

Performance Advantages

Flexible PCB antennas provide a high-efficiency level and omnidirectional radiation with similar performance as a terminal antenna. What’s surprising is that they achieve this high-level performance easily.

Moreover, you’ll need less groundwork to optimize these circuit boards to perform their functions. 

Application Diverse

We noted that flexible PCB antennas are used in various devices and applications. For example, you’ll find them in smart meters where you can retrofit them within an existing design.

This way, you’ll not incur costs related to major design projects. 

Moreover, you’ll find them in telematics, where they enable wireless features.

Consequently, they offer an integration and performance advantage over SMD antennas. Finally, you’ll find them in point-of-sale of electronic devices. 

Less Costly Than External Antennas

We like flexible PCB antennas because they cost less than externally mounted antennas. Therefore, you can get high-performance levels without incurring further expenses. 

Faster Time-to-Market

Finally, we found that FPC antennas provide a quicker route to the market while proving cheaper.

This is unlike expensive LDS antennas, especially when you’re not manufacturing them at very high volumes. 

Are FPCB Antennas Perfect for Your Project?

Engineers working on a project

(Engineers working on a project)

Even though FPCB antennas are easier to integrate into electronic devices, you must consider some things while choosing the right option.

For example, although they function effectively with small devices, most designers fold and bend them beyond their limits for highly-compact electronics like wearables, thus reducing performance. 

You must also consider the materials you use for housing. Surprisingly, the antennas function well with relatively thin plastic housing. In most cases, metal housing presents problems. 

Moreover, for all projects, you must mount flexible circuit board antennas away from metal surfaces and components. We recommend at least 20 mm away to allow the antenna room to radiate effectively.

Applications of FPCB Antenna

A mobile device using an FPCB antenna

(A mobile device using an FPCB antenna)

Generally, flexible PCB antennas have become a popular option for new electronic designs thanks to their high-performance levels and easy integration.

Additionally, they reduce the space you need for your antennas and RF circuitry. Therefore, you can employ them in any of the below applications: 

  • Electronic devices having small circuit boards
  • Projects that add wireless capabilities to existing designs
  • Products having small manufacturing volumes or first-generation products
  • Small electronics functioning on cellular frequencies

Designing PCB Antennas

You should design and layout your antenna according to the requirements since it’ll affect the performance of your device.

Surprisingly, some minor details like layer thickness, layer count, and material types that many often ignore impact the antenna performance. Therefore, to have a perfect FPCB design, follow the below guidelines:

  • Positioning your antenna: Generally, we position the antenna based on its radiation level or operation mode. The best position to have your antenna is at the corner of your circuit board. This way, you give it clearance to more spatial directions. 
  • Keep-out area: Avoid placing components in the near field directly around your FPCB antenna. Doing this will expose your antenna to signal interference, thus affecting circuit performance. Also, space the area around your antenna from any metallic objects. 
  • Ground planes: Here, you need to consider the ground plane size on the circuit board. In most cases, the wires you use to communicate to batteries and different devices may alter if you fail to design well. Therefore, using proper ground plane sizes ensures that batteries and wires affect antennas less. For the case of ground-plane dependent antennas, ensure the battery is near the antenna. 
  • Antenna proximity to other circuit board components: The idea is to keep the FPCB antenna away from other PCB components. Keeping components closer to the antenna causes signal interference. Generally, the distance between the components and the antenna depends on the width and height of the component. 
  • Designing transmission lines: The Rf trace carries and delivers the signal. You should design this trace at 50 Ω failure so that the signal-to-noise ratio will degrade. 

FAQ

What are the types of flexible PCB antennae?

You’ll come across many PCB types on the market, including planar inverted-F, monopole, and microstrip patch antennas.

Surprisingly, these antennas use copper, silver, or gold as the conductive and radiating elements, thanks to their high conductivity. 

Does a flexible PCB antenna save space?

Yes! First, you can bend and fold flexible PCBs and the attached antennas to fit in tight spaces. For this reason, you can design them for compact devices.

Moreover, flexible PCB antennas eliminate the need for wires and connectors, thus saving space and reducing assembly costs and time. 

Conclusion

Flexible PCB antennas are finding increased application in the wireless industry thanks to their low profile, flexibility, and affordable price.

These antennas are designed with polyimide flexible PCB and copper materials. However, thanks to their high conductivity, we can sometimes use gold and silver. 

As mentioned, the antennas offer diverse applications, simple integration, integration flexibility, and some performance advantages.