Low-noise amplifiers

Low-noise amplifiers (LNAs) are designed to amplify weak satellite signals while minimising noise. This amplification is essential because GNSS signals arrive at the antenna with very low power levels, often below the noise floor of typical electronic components.

First, LNAs are placed close to the antenna’s feed point to minimize signal loss. This placement reduces the impact of cable attenuation between the antenna and receiver. A well-designed LNA preserves the signal-to-noise ratio (SNR), improving overall system sensitivity.

Next, LNAs use low-noise transistors and components to achieve noise figures typically below 2 dB. Lower noise figures directly improve the receiver’s ability to detect weak signals. This is critical for reliable satellite tracking, especially in challenging environments like urban canyons or dense foliage. Moreover, LNAs must provide adequate gain, usually between 20 and 40 dB. This gain boosts the signal to levels that the receiver’s analog-to-digital converter can process effectively. However, designers balance gain carefully to avoid amplifier saturation or distortion.

Additionally, LNAs include filtering stages to reject out-of-band interference. These filters reduce the impact of unwanted signals such as cellular or Wi-Fi transmissions. Effective filtering protects the GNSS receiver from desensitization and improves position accuracy.

Thermal stability is another important LNA characteristic. Temperature changes can affect gain and noise figure, leading to signal quality variations. High-quality LNAs incorporate temperature compensation circuits to maintain consistent performance.

In conclusion, low-noise amplifiers enhance GNSS antenna performance by amplifying weak signals with minimal noise. These devices enhance signal strength, minimise interference, and facilitate precise satellite navigation in a variety of environments. For instance, surveyors rely on LNAs for precise positioning in urban and forested areas, while autonomous vehicles count on LNAs to sustain continuous GNSS coverage in complex urban environments. In both applications, LNAs improve signal quality, increase reliability, and support critical GNSS performance in challenging conditions.