Key Design Considerations for Selecting the Right RF Antenna

Display portlet menu

Key Design Considerations for Selecting the Right RF Antenna

smartphone showing alarm feature

By Matt McWhinney, Business Development Manager, Molex

When faced with the need to make design decisions, system engineers are challenged with multiple options, any of which can have a major impact on the effectiveness of the wireless performance. There are many considerations when selecting RF antennas for wireless electronic devices. Some design choices may already be constrained, based on the overall system design. Basic choices that a system designer may make include:

  • What frequencies (often determined by what wireless protocol – e.g., Wi-Fi, BlueTooth, Cellular, GPS, NFC etc.) are needed?
  • What modem / transmitter will be used?
  • How much power will be available for the system? (e.g., Impacts antenna choices and wireless performance)
  • How much data throughput / speed is needed?
  • How much efficiency (Antenna gain) is required?
  • Where does the antenna need to be and even potentially what orientation(s) will the device be for wireless operation (e.g., Mobile or fixed?)
  • Where will the antenna be located on the PCB? (e.g., Cabled to the PCB but inside or connected to the device? External to the device?)
  • How much flexibility exists with the overall system design to modify antenna choices (e.g., location, size, type, number of antennas in the system). For example, if an antenna is positioned too close to metal, an LCD, a battery or another device component, it may not work at all. However, if the antenna is a few millimeters away from those components, it may work fine.

Today, an overwhelming majority of antennas are not visible externally – either they are on the PCB or internally cabled to the device. The days of the external ‘walkie talkie’ antennas are distant memories when with most new wireless devices due to the efficiencies of RF electronics and the pervasiveness of wireless networks around us.

There are, of course, other considerations. Efficiency can vary by antenna type (e.g., monopole, dipole, slot, PIFA, panel, etc.) and today’s wireless devices employ many different antenna designs. That’s important because smartphones, wearable electronics, other wireless devices and the growing demand for broadband connectivity are driving the use of more cellular, Wi-Fi™ and Bluetooth® antennas. The Internet of Things (IoT) and machine-to-machine (M2M) technology are also leading to additional wireless deployments that are expected to increase productivity and efficiency while evaluating the measurement applications, quality control, decision-making and customer relationship management.

Applications for wireless devices are incredibly diverse, ranging from industrial applications to smart home devices and surveillance systems. Wi-Fi antennas are showing up on refrigerators, door bells and various other home appliances.

Choosing an Antenna
When evaluating antennas for a wireless device, the first step is always to determine if a standard, off-the-shelf antenna is suitable. Off-the-shelf antennas offer a great advantage in terms of aiding in quick time to market. Being able to quickly identify, prototype, and measure one or more antennas for a system can assure that the right choice is made and quickly – reducing overall product risk. Additionally, because their cost is amortized over large production runs, standard antennas are typically the lowest-cost option. However, today’s device designs are more complex and compact, and device manufacturers are forcing more antennas into smaller and complex geometries surrounded by unfriendly materials and objects. There may be times, however, where a custom device may be the best or only option for the application.

The Starting Line
After the frequency or frequencies and basic wireless architecture parameters have been determined, device manufacturers typically begin the design process by selecting one or more appropriate standard antennas for evaluation, which are available for virtually every allocated frequency. Based on diverse manufacturing and RF technologies, standard antennas offer high performance and ease of integration for wireless applications in the industrial, consumer, medical and automotive markets, among others. Standard antennas can perform well for less cost and risk than a custom solution and offer shorter lead times for bringing wireless products to market.

Once the antenna is selected, engineered and mounted into the prototype device, ideally there is some testing for performance in an anechoic chamber. If the antenna does not work, then either the design is modified, or another antenna is tried.

Calling on Custom
However, if a standard antenna does not work effectively, designers can utilize the design expertise of experienced antenna suppliers. The supplier may be able to customize an existing standard solution, providing the system designer with what they need, cost-effectively, and quicker than going through a ground up new design process, for a full custom antenna. Customizations of existing antennas may range from changing cable lengths or connectors on the antenna cables; to making small changes to the antenna pattern to ‘tune’ the antenna so, that it can match the performance need of the application.

The design process typically begins with the device manufacturer sharing a CAD model of the proposed product with the antenna supplier. Software is used to simulate antenna performance based on the properties of the device, the enclosure and any surrounding metal, measuring parameters such as return loss and efficiency. Based on that information, the supplier builds a prototype antenna to test it and then adjusts the design as needed.

For example, one custom project included a cellular antenna plated on the plastic device enclosure. A small number of prototypes were created and tested, and it was determined that they needed to be several millimeters shorter to compensate for the effect of the plastic enclosure. Using calipers and a sharp knife, the radiating arms were trimmed to the appropriate length based on the wavelength of the signal the device was designed to pick up. The tested, shortened antenna design went into full production.

There are many technologies that are used to produce custom antennas – one of the most common involves plating conductive antenna ‘traces’ on plastic and is called Laser Direct Structuring (LDS). LDS is used to make antennas in many 4G cell phones and other compact devices that could not support any other type of standard internal antennas. Generally, higher volumes are needed to justify the effort to use LDS and other custom antenna technologies.

Test, Retest, and Re-Retest
Once selected and designed into the system, it is very smart to test to see how effective the antenna is. Antenna design is iterative in nature. This is true with both design of the actual antenna element and can be true even when designing in an off-the shelf antenna into a system. Ask RF engineers if changing a particular antenna parameter would improve the design and they will typically say “There’s no way to know. We have to test it.” In other areas of applied science, engineers might be willing to provide an educated guess to a similar question, but with RF, antenna sensitivity to surroundings and typically razor-tight performance margins make actual testing the product the only answer – then testing it again and again, if needed.

Designers never begin a device development project hoping it will require a custom design; standard off-the-shelf RF antenna solutions are always preferred due their lower cost and short lead times. However, when a custom antenna is needed, the design and testing resources of an experienced antenna supplier are vital in creating a solution that works effectively for today’s complex, often small wireless devices.

Finally, it is worth noting that with nearly all RF devices, some type of approval is required with the full system for release to commercialization. All the previously mentioned antenna testing is not only important to ensure adequate device performance and happy end users, but it may be necessary to get FCC approval for the device. In the event that the device is used in a cellular network, it will be necessary for the device to pass the requirements of all carrier RF requirements. Generally, the higher the speed of a device on a 4G network, the more demanding and challenging this certification process is – e.g., a Smartphone is required to go through more extensive testing and validation than a LTE enabled home surveillance base-station. Devices with well-designed antennas that have gone through iterative cycles of antenna performance testing, will fare through finished product RF validation and testing such as carrier or FCC testing.

In summary, the more attention that can be given to making smart antenna choices early in the design process, the better the wireless performance will be. About the author: Matt McWhinney is a business development manager at Molex. Matt has a degree in electrical engineering, enjoys working with innovative customers and is a technology enthusiast of smart and power electronics.

Wi-Fi and Bluetooth are trademarks or registered trademarks and are the property of their respective owners.

Related Articles
AI at the edge computing solutions
Why artificial intelligence at the edge matters
April 10, 2020
AI at the edge will have profound effects on many industries, including transportation, defense, manufacturing and healthcare to name a few. How will AI at the edge change these industries, and why does it matter?
Three men standing in stairwell talking
Spending on design up front can save you from long-term pain
March 20, 2020
Spending money in the early phase of development may be painful, but problems with quality, production runs and backers can be far more painful.
interior of autonomous car
The State of Automotive Only Starts with Autonomous Driving
March 6, 2020
Learn how the state of automotive spans a variety of applications, from electrication to in-cabin AI.
view from autonomous vehicle as it interprets street signs
Somewhere Between the Flintstones and the Jetsons
March 6, 2020
Learn more about developing adaptable automotive automation with Xilinx
man wearing virtual reality headset with graphic overlays
How LoRaWAN and AI at the Edge Revolutionize the IoT
January 3, 2020
Learn how LoRaWAN and artificial intelligence (AI) at the edge can revolutionize the internet of things by reducing data transmission and improving latency.
woman with diabetic monitory
Connectivity Among Major Analog Design Considerations in Health Wearables
December 9, 2019
Development of very low powered analog body sensors, digital microcontrollers, and innovative power and battery management circuits are driving the growth of wearable healthcare products.
metal nut in venier calipers measuring tool
Is best in class the only consideration for your analog design?
December 9, 2019
It’s easy to seek out the absolute top of the line when it comes to a design. Whatever the “best” part is, is probably what’s going to be the most compelling for your design, right?
two robotic arms
Decreasing Time to Design in the Industrial Internet of Things
April 23, 2019
The huge potential for innovation in industrial IoT (IIoT) offers the promise of significant productivity gains, operational efficiency and bottom line revenue increases, but only if it’s enabled by a supply chain based on reliability, stability an
automobile with sensors collecting information
We’re All Part of the Automotive Evolution
April 23, 2019
ADAS (Advanced Drive Assist Systems) and its evolution into full autonomy could see the end of road-based fatalities, injuries and incidents. Technology is now providing the solutions that can help the automotive industry achieve Vision Zero within j
test car colliding with object
Transportation Safety: 5 Protocols & Processes to Know
April 4, 2019
A dynamic range of protocols can help make our transportation technology safer.
cargo ship at port
Transportation Trends in Commercial & Non-Passenger Vehicles
March 29, 2019
Some of the most exciting technology trends shaping transportation are for commercial vehicles.
futuristic city scene
The Car: A Rolling Smart Device
February 5, 2019
Be it for streaming your favorite music, sending emails or getting real-time information on traffic jams: cars have long since played host to mobile internet—and will continue to via diagnostics, hotspots and ADAS.
man using tablet computer in industrial setting
5 of the best artificial intelligence use cases
January 3, 2019
AI’s upgraded algorithms make predictive analytics, parse data, and help businesses make smarter decisions from the boardroom to the factory floor.
Wi-Fi router on desk
How wireless communication protocols make or break designs
November 11, 2018
The design process includes many critical decisions for engineers, such as which wireless communications protocol to use.
group of professionals in a meeting
How startups can integrate with design partners
November 9, 2018
While it might feel like the rubber truly meets the road at the manufacturing stage, the design process is truly where creators’ great ideas take shape. It’s also where you’ll make major decisions that impact your production and deployment.
vibration enabled vests hanging on rack
The future of music is for everyone—even the deaf
November 9, 2018
How Avnet helped an award-winning tech incubator take one of the most complex wearables from “possibly” to “possible”
Crowd watching live rock band playing on stage
How the Deaf Experience Music—Then and Now
November 8, 2018
When you think of experiencing music, what comes to mind? The sound. But sound is vibrations—and the key to how Avnet created a wearable to allow deaf and hard of hearing people to listen to live music.
Thee men standing around a computer monitor
The 3 IoT Security Fundamentals Startups Need to Know
November 6, 2018
In a startup environment, when funding sources—or lack thereof—are looming every day, security might not be on the top of your mind. Here are 3 reasons why it should ... and what to consider about security.
Electronic body suits hanging on racks
3 Lessons for Hardware Creators from a Desert Music Festival
September 25, 2018
When a creator has a big idea, they often need a big partner to help them make it happen. Music: Not Impossible was no exception.
Graphic of a green car flying in the air
Autonomous vehicles are the future
April 9, 2018
Autonomous vehicles do not just replace the driver, helmsman or pilot, but have the potential to create completely new business models worth billions.
Interior of European self-driving car
Meeting Next-Generation Automotive Design Challenges
April 2, 2018
As the automotive industry advances toward Level 5 fully autonomous vehicles, automotive engineers will have to continue driving more functionality out of vehicle subsystems that deliver safety, infotainment, and other features.
young man and woman inspecting equipment in computer datacenter
Buy or build your IoT infrastructure?
By Michael Lamp   -   March 6, 2018
Read about the questions many businesses face when starting to create plans for an IoT project.
Combine on a field
The story of Swift Navigation
January 11, 2018
Autonomous functionality is set to disrupt industries from automotive to agriculture and robotics. There’s just one problem: GPS technology needs to catch up.
Man using a soldering tool to work on a circuit board
What’s A Lead Time – And Why Should You Care?
December 19, 2017
Learn how effective management of lead times and partnering with a distributor can help you keep promises.
person modifying settings on audio mixer console
VGAs Manage, Optimize RF Signal-Chain Ranging
December 18, 2017
The variable-gain amplifier (VGA) is a critical part of the RF receiver signal chain. Its function is to solve the problem of received RF signals having more dynamic range than the analog-input circuitry can accommodate.
futuristic automobile interior
How all programmable technology revolutionizes embedded vision
December 14, 2017
Autonomous driving is just the start of EV solutions. Learn how all-programmable is revolutionizing embedded vision.
person holding smartphone on coffee table
3 levels of Qi testing
November 14, 2017
See how the Qi Sniffer and Qi Certified Product Testers can help you test and certify your Qi products.
microprocessor chip being examined by worker
Zynq SoMs Decrease Customer Development Times and Costs
March 8, 2017
Xilinx’s Zynq®-7000 All Programmable (AP) System-on-Chip (SoC) provides a new paradigm for embedded system design.
close-up of orange car headlights
Automotive LEDs Deliver Greater Design Flexibility for Safety, Style and Efficiency
March 7, 2017
LED lighting has been making major inroads into the automotive market for two key reasons: safety concerns and energy consumption.
puzzle piece put in place
An Overview of FPGAs: The Solution to Countless Design Challenges
March 7, 2017
The field-programmable gate array as a primary processing element offers many design, debug, and production benefits with few, if any, downsides.
woman on laptop with smart phone and smart watch
Will HaLow Open the Door for More Intelligent Systems?
March 7, 2017
Reporting on the recent announcement of the “long-awaited Wi-Fi HaLow standard for products incorporating IEEE 802.11ah wireless networking technology,” Jim Hunter of Tech Crunch explains why this new standard may pave the way for more connected
man drawing schetch of an electric car attached to a battery
Technologies and Components for Designing Electric Vehicles
March 6, 2017
Hybrid electric vehicles (HEVs) such as the Toyota Prius and the Chevy Volt and electric vehicles (EVs) such as the Nissan Leaf, BMW i3 and Tesla Model S are growing in popularity amid concern for global warming.
tablet with iCloud image and IoT icons
Finding the Best Wireless Option for Your IoT Design
March 6, 2017
The Internet of Things (IoT) relies on a facile communications framework able to move data easily between embedded "things" and systems located at higher levels of the IoT hierarchy. For designers, a diverse set of wireless connectivity options...
military plane taking off
Defense/Aero Spinoffs Remain an Exceptional Source for Breakthrough Technology
March 5, 2017
Yes, automatic across the board cuts within the Department of Defense (DoD) will put the squeeze on many within the defense/aerospace supply chain.
self-driving car at intersection
Top 5 Tech Trends in Advanced Driver Assistance Systems
March 4, 2017
Advanced driver assistance systems (ADAS) promise to enhance vehicle safety by helping to simplify the driving process, reducing sources of driver distraction and inattention that often lead to accidents. With ADAS support, drivers and their passenge
truck driver, highway and IoT icons
Getting Started in Automotive Smart Vision Design
March 4, 2017
Advances in embedded vision technology have heightened interest in applying smart vision solutions for automotive safety.
rear view camera on car dash with image of child riding a toy
Top 5 Myths in Automotive Vision: Designing Embedded Vision Systems Is Easier Than You Think
March 3, 2017
Vision has always occupied a special place in information science and popular culture. One does not need to be an engineer to appreciate the vast bandwidth available in normal human vision. Most people understand that the common saying “a picture i
hand navigating smart car dasboard
Automotive Electronics: Top 5 Tech Trends of Tomorrow’s Smart Cars
March 3, 2017
In the United States alone, motor vehicles travel well over four trillion miles each year according to the U.S. Department of Transportation.* To gain a sense of this distance, consider that while it takes light approximately eight minutes to travel
blue sketch of a car
Gesture Recognition, Proximity Sensors Drive Advances in Automotive Infotainment
March 3, 2017
Safety must remain paramount when designing interactive interfaces for automotive applications, including guarding against distracted driving.
Man navigating an IoT car dashboard
The Internet of Things is Driving The Internet of Autos
February 14, 2017
In the early 1900s Henry Ford made the automobile affordable and accessible. But what he really did was offer people connection. Rural residents could connect with more urban areas to sell crops and buy supplies.
Related Events
Architecture & Key Components of a 48 V Electric System
Date: May 14, 2020
Location: Webinar
3 Ways to Make Your System More Robust
Date: December 4, 2019
Location: Webinar
Ultra96 Technical Training Courses
Date: January 14, 2020
Location: Multiple Locations