Circulator-Based LNA Jammer Isolation for GNSS Receivers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GNSS receivers are susceptible to interference from high power signals, such as jammer signals, which saturate amplifiers and degrade receiver performance, rendering them inoperative at high jammer power levels.
Innovation Solution
The antenna sub-assembly includes a low gain section with band-pass filters and a switch that dynamically switches between a primary filter circuit and an alternative filter circuit based on the presence of jammer signals, filtering out unwanted signals while allowing desired GNSS signals to pass through, thereby preventing amplifier saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If amplifiers are used to amplify weak GNSS signals, then signal strength is improved, but the amplifiers become susceptible to saturation from high power jammer signals
Solution Approach 1:
A circulator is introduced as an intermediary component between the antenna and amplifier. The circulator directs signals in a specific direction (port 1 to port 2, port 2 to port 3, port 3 to port 1), allowing the amplifier to receive GNSS signals from the antenna while isolating it from reverse-direction jammer signals that would otherwise cause saturation. This mediator protects the amplifier without attenuating the desired weak signals.
Solution Approach 2:
The signal path is segmented into different directional components using the circulator. Forward signals (antenna to amplifier) are allowed to pass for amplification, while reverse signals (jammer to amplifier) are directed to a different port and isolated. This segmentation separates useful signals from harmful interference based on their propagation direction.
2Power
If high power jammer signals are present, then amplifier saturation occurs, but the receiver becomes inoperative
Solution Approach 1:
The circulator acts as a mediator that allows the amplifier to operate at high power levels by blocking the harmful jammer signals from reaching it. The circulator's directional coupling特性 enables the amplifier to produce high power output for legitimate GNSS signals while the circulator prevents high power jammer signals from causing saturation by directing them to a different port where they can be dissipated or isolated.
3Object-affected harmful factors
If band-pass filters are used to filter out jammer signals, then interference is reduced, but filter complexity increases
Solution Approach 1:
The circulator serves as a simpler intermediary compared to complex band-pass filter circuits. Instead of using multiple filter stages, resonators, and tuning elements, the circulator provides directional signal routing with a single passive component. This reduces device complexity while still achieving the goal of reducing jammer interference through directional isolation rather than frequency-based filtering.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces interference from high power signals, ensuring the GNSS receiver maintains operational performance even in environments with strong jammer signals, by dynamically filtering out spillover and jammer signals, thus preventing saturation and maintaining accurate positioning.
Implementation Method 1
A circulator is disposed between the antenna and the amplifier. The circulator may be utilized to prevent jammer signals from reaching the amplifier
Implementation Method 2
The antenna sub-assembly of the GNSS receiver utilizes amplifiers to amplify the relative weak signals
Implementation Method 3
The switch is able to switch between a primary filter circuit and an alternative filter circuit
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A low noise amplifier (LNA) assembly comprising a filter circuit for receiving signals from a Mobile Satellite Service (MSS) band and a Radio Navigation Satellite Service (RNSS) band; and an alternative filter circuit configured to filter out a jammer signal.