Gain is one of the most important measurements when assessing any type of antenna, including cellular, Wi-Fi®, and global navigation satellite system (GNSS). That’s because gain directly affects the performance and reliability of your device and all of the services that run on it. As a result, gain also affects your device’s competitiveness, revenue potential, and brand reputation. All of this is true whether your device is designed for consumers or businesses, or for mobile or fixed applications.
Gain measures an antenna’s directionality as it relates to the strength of the signal that it’s transmitting or receiving. For example, the gain of a GNSS antenna directly affects the quality of the GNSS signals. A high gain improves the signal-to-noise ratio and reduces Time to First Fix (TTFF).
Gain applies to antennas whether they’re used for receiving, transmitting, or both:
- Receiving: The antenna’s job is to give the receiver as much signal as possible to work with. The more effective it is at pulling in signals weakened by distance or by physical obstructions such as skyscrapers and foliage, the easier it is for the receiver to do its job. This maximizes the device’s battery life because the receiver doesn’t have to use as much power to compensate for poor gain. Gain measures the antenna’s effectiveness and quantifies it in decibels (dB).
- Transmitting: Gain measures the antenna’s effectiveness in converting the electrical energy from the transmitter into a signal. Its gain also is measured in dB.
Gain also is a common way to categorize antennas:
- High-gain antennas are directional, meaning they focus on a specific direction when transmitting or receiving. One example is GNSS receiving antennas pointing up to the sky to maximize reception of satellite signals. High-gain antennas often are called “active” antennas because they use low-noise amplifiers (LNAs) to boost the signal before it’s sent to the receiver. This is particularly valuable for location applications that require high precision and availability because GNSS signals are relatively weak by the time they reach the Earth. But it’s also important to note that a passive antenna can have high gain by virtue of its design. In other words, the addition of an LNA (or an amplifier) is not the only way to maximize gain.
- Low-gain antennas are omnidirectional, which means they receive or transmit signals in all directions. This is ideal for applications where signals need to be received from or transmitted to multiple directions, such as cellular antennas in smartphones and Internet of Things (IoT) devices.
Can You Have Too Much Gain?
Another key consideration is peak gain. Some regions have regulations that limit peak gain for certain radio technologies. For example, in the U.S., the FCC limits gain for Bluetooth®, cellular, and Wi-Fi® to avoid interfering with civilian, military, and research services in the same or adjacent bands. This caveat highlights three important aspects:
- Higher is not always better. When choosing an antenna, don’t focus on gain to the point that it overshadows other, equally important specs, such as efficiency, and the ability for the device to comply with regulations such as the FCC’s Effective Radiated Power (ERP) and Equivalent Isotropically Radiated Power (EIRP) requirements.
- New technologies often affect gain limits. Demand for wireless services is insatiable, which is why governments and standards bodies are searching under every rock for additional spectrum. For example, many 5G cellular bands are in, or adjacent to, the spectrum that was the exclusive home of other services. To ensure peaceful coexistence, 5G has peak gain limits to avoid interference with those incumbents. This aspect will become even more challenging with 6G, which will move into additional bands that no cellular technology has ever occupied.
- Module manufacturers also specify peak gain limits for antennas used with their products. Navigating these requirements can be complex, which is why device OEMs frequently turn to Taoglas for guidance. In the case of embedded antennas, an example is determining how the ground plane, components surrounding the antenna, and device housing all affect gain and the choice of antenna.
Gaining Advantages Through Design
A variety of factors affect an antenna’s gain, including the device’s design, form factor, and installation. For example, if the device uses an embedded antenna, the printed circuit board (PCB) also serves as the ground plane. In a portable device, the ground plane is the virtual, electrical equivalent of the earthen ground system that fixed antennas have, such as for TV and radio stations. The size of the PCB ground plane, as well as the antenna’s location within that space, both affect gain.
Another example is an external antenna mounted on a vehicle’s roof or trunk, which serves as the ground plane. As with PCB ground planes, the size and the antenna’s location within it both affect gain. This is particularly important for GNSS because satellite signals are inherently weak by the time they reach the antenna on vehicle. In those applications, the vehicle’s roof or trunk lid serves as the ground plane to increase the antenna’s gain.
These factors also highlight why antennas and antenna integration are aspects to consider early in the product design process. In the case of embedded antennas, if they’re addressed later, such as after the device’s form factor is finalized, there’s a good chance that the ground plane might not be large enough. Now an extensive, expensive redesign of the product may be necessary, leading to cost overruns and delaying its market launch.
To learn more about how to gain an advantage with antenna gain, speak to Taoglas’ Engineering team by clicking on the button below.
