When choosing a global navigation satellite system (GNSS) antenna, one top consideration is whether to use a passive or active model. This critical choice directly affects the performance, battery life, reliability, and market potential of the device and the services that rely on it. We created a helpful guide on the application design priorities you should consider, which you can view on the left of the page. While these considerations are useful indicators, the decision is much more complex. We'll explore this further below.
A passive GNSS antenna doesn’t include any front-end circuitry and doesn’t require a power source like a battery. It only consists of the element that receives the GNSS signals. Active GNSS antennas include an integrated Low-Noise Amplifier (LNA) that boosts the signal before it’s passed to the receiver. Taoglas active GNSS antennas also have front-end filtering, which removes out-of-band signals and noise to improve signal quality. Below, we’ll explore the top design considerations for when you might need an active antenna.
One key consideration is whether you want a standard GNSS or a high-precision solution. What's the difference? Standard GNSS provides meter-level accuracy, which is suitable for most general navigation applications. In contrast, high-precision GNSS can achieve centimetre-level accuracy, which is essential for more demanding applications and requires an active antenna. With their integrated Low-Noise Amplifiers (LNA) and filtering, active antennas provide the higher gain needed to achieve such precision. Standard GNSS is sufficient for general navigation applications like smartphones, car navigation systems, and recreational GPS devices. High-precision GNSS is used in applications requiring extremely accurate positioning, such as land surveying, precision agriculture, autonomous vehicles and precision timing solutions.
When designing GNSS solutions, it is important to decide early in the integration process whether to use an active or passive antenna. If this choice is left too late, you may need to use an active solution, whereas you might have managed with a lower-cost passive antenna if it had been considered earlier in the design process. Passive antennas, which lack integrated electronics and require no power, offer easier integration in embedded systems. However, in environments with obstructed sky views, such as urban areas, active antennas—featuring higher gain through an integrated Low-Noise Amplifier (LNA) and front-end filtering—may be necessary to ensure signal accuracy and precision. If the antenna is considered late in the design process, opting for an active antenna might be required to achieve the desired performance. However, this can increase costs and development time. Therefore, early consideration of antenna requirements is essential. It not only saves you time and money, but also makes your development process more efficient and productive, allowing you to focus on other aspects of your GNSS solution. There is a lot to consider; click the button below to read more about antenna integration.
The following active circuit block diagrams are commonly used to switch from a passive antenna solution to an active solution. The complexity of the active circuit design depends on the number of GNSS bands used (single vs. dual vs. multi-band), the antenna type, and the number of feeds (outputs) the antenna has. Taoglas has designed front-end active circuit modules that can be used for dual and multi-band GNSS antennas with different feeds and configurations. These modules can be designed onto the device PCB alongside the antenna to reclaim valuable real estate and save designers up to two years of complex design. View them at the links below: • TFM.110A • TFM.120A • TFM.100A • TFM.100B
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