Secondary Radar ADS-B Detection via Antenna Channel Reuse
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Solution Overview
Problem
Current air traffic control systems using secondary radar and ADS-B technology face limitations in detection range and accuracy due to low antenna gain and increased costs with multiple antennas, leading to reduced ADS-B detection rates and increased pollution in the 1090 MHz spectrum.
Innovation Solution
A method for long-range ADS-B detection using a secondary radar with SUM, DIFF, and CONT channels to detect and locate ADS-B squitters, allowing single squitter positioning and reducing pollution by locking out targets before they enter operational coverage, and correcting distance measurements for ionospheric propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple antennas are employed to cover 360° for dedicated stand-alone ADS-B receiver, then the listening coverage is improved, but the antenna gain decreases and the cost increases
Solution Approach 1:
The patent makes the secondary radar antenna system universal by enabling it to perform both synchronous radar detection and non-synchronous ADS-B reception functions. The existing SUM, DIFF, and CONT patterns designed for radar are reused for ADS-B detection, eliminating the need for separate dedicated ADS-B antennas while maintaining comprehensive 360° coverage and high gain performance
2Area of stationary object
If dedicated stand-alone ADS-B receiver with multiple antennas is used, then the listening coverage is improved, but the specified guaranteed range is limited to 150 Nmi
Solution Approach 1:
The patent leverages the superior performance of secondary radar downlink reception (designed to be more sensitive than uplink transmission) and applies it to ADS-B squitter reception. By using the radar's high-gain SUM pattern (27 dBi) instead of omnidirectional patterns, the system achieves very-long-range ADS-B detection exceeding 250 Nmi, significantly extending the guaranteed range beyond conventional 150 Nmi limitations
3Measurement precision
If two almost consecutive position squitters are required to locate a target in ADS-B mode, then the position accuracy is improved, but the detection rate decreases and the complexity increases
Solution Approach 1:
The patent introduces the secondary radar's azimuth measurement capability as an intermediary to resolve the position ambiguity of single ADS-B squitters. The radar measures the azimuth of received squitters using its SUM and DIFF patterns, then uses this angular information to determine which of the two possible CPR positions is correct, enabling accurate single-squitter location without requiring two consecutive squitters
Solution Approach 2:
The patent changes the parameter used for position determination from relying solely on two consecutive squitters to using a single squitter combined with radar-measured azimuth. This parameter change allows the system to achieve the same positioning accuracy with fewer observations, thereby increasing detection rate and reducing system complexity
4Area of stationary object
If non-synchronous ADS-B listening is performed using omnidirectional control pattern, then the listening coverage is improved, but the gain is reduced to more than 17 dB
Solution Approach 1:
The patent makes the high-gain radar antenna patterns universal for ADS-B detection. Instead of using dedicated omnidirectional patterns with limited gain, the system uses the existing SUM pattern (27 dBi) and CONT patterns for non-synchronous ADS-B reception, achieving both comprehensive coverage and superior gain performance simultaneously
Data Source
AI summary
The secondary radar includes an antenna having a radiation pattern forming a sum channel, designated SUM, a radiation pattern forming a difference channel, designated DIFF, and a pattern forming a control channel, designated CONT, the targets are located by implementing the following steps: detecting ADS-B squitters received via the CONT channel, via the SUM channel and via the DIFF channel; measuring at least the power of the squitters and their azimuth with respect to the radar; the location of a target transmitting ADS-B squitters being computed by exploiting at least the detection of one ADS-B squitter, in light of the latitudinal and longitudinal position of the radar and of the azimuthal measurement with respect to the radar, the position cell, designated the CPR cell, coded in the squitter being selected via the azimuthal measurement.