Early mobile phones were clunky, cumbersome devices that had ostentatiously visible antennas. With increased miniaturization, such features are no longer a standard of smartphones today, but wireless communication devices still require antennas to function.
Smartphones use multiple built-in antennas to transmit and receive radio waves across various frequencies for specific wireless communication tasks. Wi-Fi, Bluetooth, cellular communications, and GPS would not work without the antennas inside smartphones.
The days of clunky brick-sized mobiles with their long antenna are gone, but that doesn’t mean antennas aren’t still crucial to your smartphone’s function. This article will explain what antennas built into smartphones do, where you can find them, and how they came to be so small.
Where are the Antennas in a Smartphone?
Smartphones today have not just one but multiple antennas; a single phone may contain a dozen. Of course, these are no longer of the extended retractable variety. In fact, they are so small you would find it hard to locate them.
At 0.3 square inches (or 1.94 square centimeters), smartphone antennas today are tiny enough to be printed or mounted directly onto the Printed Circuit Boards (PCBs) inside a phone’s body. They may also be printed onto the inside cover of smartphones and connected to PCBs from there.
The antennas on a smartphone are usually located near the top and bottom of a smartphone to facilitate easier wireless transmission. This placement is because electricity-conducting materials like metal impede or interfere with radio waves.
Such miniature antennas are present not only in smartphones but also in many other wireless communication devices, such as:
- Smartwatches
- Laptops
- Wireless media players
- Cameras and speakers
- Sensor-triggered thermostats
- Autonomous vehicles
- Retail barcode readers
- Many other devices incorporated into the Internet of Things (IoT)
Why Is It So Hard To Locate Antennas on Modern Smartphones?
Smartphones today follow the design lead of the trendsetter in the market, Apple. Since the very first iPhone, launched in early 2007, Apple has set the pace, making mobile phones more and more compact and seamless each year. The whole purpose of such devices is to be ever-present but unobtrusive.
Increasingly, most phones look the same. They are all uniformly smooth, made of glass or metal with beveled edges, the bare minimum number of buttons and ports, and maximized screen space.
On most phones, the only way to find your antenna is by locating “antenna lines.” Antenna lines are plastic-lined windows that allow the transmission of radio waves through otherwise metal and glass bodies.
Apple is not fond of them, and they have already patented a specially engineered material that looks metal but does not block radio waves. So, in the future, it will only get harder to locate the components that make up your device.
We discuss smartphone antennas and signal in many of our articles, like “Can A Phone Case Affect Wifi Reception?” and “How To Get Reception On Your Cell Phone In Remote Areas?”
Why Are the Antennas in a Smartphone So Small?
The length of an antenna depends on the wavelength of the signal it encodes or decodes. As these have become smaller over the years, so have antennas. Apart from enhanced engineering capabilities, this is the main reason antenna sizes have shrunk rapidly over the years.
For instance, in the US, the Federal Communications Commission (or FCC)—the authority that auctions spectrum to service providers—began by allotting bands in the 900 megahertz area in the early 1990s.
A typical wavelength that early cellular phones operated on was as high as 11.8 in (30 cm). And antennas needed to be just as long. This period was the era of the chunky handset, noted for its long retractable antennas.
Later, the FCC began providing bands at higher frequencies. Today, 5G signals often use the 3700-4200 megahertz frequency range. Since wavelengths vary inversely with frequency, today’s antennas can be much smaller to perform all the necessary communication functions.
Higher frequencies can also carry more data faster. So, apart from allowing greater miniaturization, consumers can access data at higher speeds more affordably. They are an essential component of the viability of the Internet of Things (IoT).
A final aspect that has allowed antennas to shrink in recent decades is better encoding. Combined with engineering innovations, this means that antennas today need only be a quarter of the wavelength of the signal they carry in length.
What Do the Antennas in a Smartphone Do?
Smartphones are extraordinarily complex devices that perform a wide range of tasks that would have seemed magical just a decade or two ago. And while many aspects make their design so incredible, the variety, array, and size of the antennas in a typical smartphone are among their most remarkable features.
Antennas transmit encoded radio waves or receive and relay them to devices that can decode and act on them. They may even do both. A typical smartphone can contain four or more antennas, and engineers keep adding more as technology improves, especially with 5G and 6G. These perform specific individual functions, including:
- Sending and receiving voice calls and text messages
- Sending or receiving data via the internet
- Communicating wirelessly with other devices, such as media players, computers, cameras, printers, scanners, and card readers
- Communicating with satellites to use GPS-enabled services
- Listening to public radio stations via FM
Cellular Antennas
Cellular antennas are the primary communication antennas on a smartphone. They use a range of frequencies to communicate, with upper and lower limits depending on the technology, the device, and the local availability of the spectrum. Top brands constantly release new bands and smart devices to deliver faster speeds.
Cellular antennas are essential for voice, text, and data communications. You can typically locate the primary cellular antenna near the bottom of a smartphone, which both transmits and receives. A second cellular antenna, located at the other end of the device, only receives radio waves.
The second antenna—known as a Diversity Antenna—samples various alternate signals to the one used by the primary cellular antenna. This antenna helps a device latch on to the strongest available signal in an area.
Because primary antennas transmit radio energy, broadcast regulators have laid stipulations on how much energy they may transmit. Service providers have stringent criteria for energy transmissions as well.
WiFi Antennas
WiFi antennas are the most miniature antennas on a smartphone. They are usually located near the top of a smartphone, close to GPS and Diversity cellular antennas, and connect to the same chips as Bluetooth antennas.
WiFi antennas transmit and receive data across the highest frequencies—5150-5850 megahertz—a smartphone uses, and allow users to send and receive data at the fastest speeds for their particular device. They also use a second frequency band—in the lower 2400-2484 megahertz range—that they share with a smartphone’s Bluetooth antenna.
Bluetooth Antennas
Bluetooth antennas use proprietary technologies to transmit data between devices such as smartphones and wireless speakers. They work across the 2400 to 2483.5 megahertz, which they share with the lower end of the WiFi spectrum. At present, in the best-case scenarios, they can transfer data across distances of more than a kilometer.
GPS Antennas
GPS antennas do not transmit information; they only receive it. GPS antennas also use the narrowest frequency ranges of any of the antennas on a smartphone. As more and more nations put up satellites offering GPS data, the number of bands has increased.
NFC Antennas
NFC or Near Field Communication antennas allow smartphones to communicate with other smartphones and other wireless communication devices. As the name implies, they only work across very short distances. They are also commonly used in devices like smart card readers.
Radio Antennas
Radio antennas pick up publicly available FM radio stations and other communications on the frequencies used by and between these stations. Although many users no longer use the feature, continuing demand from developing economies has kept them coming.
Final Thoughts
Smartphones have several built-in antennas, each specialized for a specific task. Some only receive, others only transmit, and a few send and receive radio waves.
Moreover, radio antennas used in contemporary wireless communication devices are so tiny that manufacturers can print them onto a smartphone’s push button configuration (PCB). They are usually located near the top and bottom of a device to facilitate easier data transmission.
As design engineers prioritize compactness and seamlessness, it is getting harder for non-experts to tell which components go inside a smartphone and where they can find them.
References:
- Gear Patrol: Your Phone Has a Tiny, Crucial Design Detail You’ve Probably Never Even Noticed
- Engadget: Apple invented a material that hides your iPhone’s antenna lines
- MIT School of Engineering: Why don’t cell phones have retractable antennas anymore?
- Antenna Theory: Cell Phone Antenna Design
- Bluetooth: Understanding Bluetooth Range
- Design News: The Challenge of Mobile Phone and Internet of Things (IoT) Antennas