Monopulse Secondary Surveillance Radar Passive ADS-B Integration
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Solution Overview
Problem
Traditional monopulse secondary surveillance radar systems face limitations in squitter range and surveillance coverage due to their three-channel antenna configuration, leading to issues with aircraft identification and tracking, especially in densely populated areas, where overlapping replies from multiple aircraft cause interference and reduce the effectiveness of Mode S radar systems.
Innovation Solution
Integration of a dedicated auxiliary passive ADS-B squitter receive channel within the interrogators of an active Monopulse Secondary Surveillance Radar system, along with additional omnidirectional ADS-B antennas and a fourth receiver channel, enables real-time passive acquisition of ADS-B and Mode 5 Level 2 equipped aircraft, reducing the need for active Mode S All-Call interrogations and enhancing detection capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a three-channel antenna configuration is used in traditional monopulse secondary surveillance radar systems, then the system structure is relatively simple, but the squitter range and surveillance coverage are limited
Solution Approach 1:
The patent segments the surveillance function into two independent channels: a three-channel monopulse radar system for active interrogation and a fourth omnidirectional channel for passive ADS-B squitter reception. This segmentation allows each channel to be optimized for its specific function, with the passive channel providing full 360-degree coverage without the mechanical constraints of rotating antennas.
Solution Approach 2:
The patent merges active radar interrogation (Mode S All-Call) and passive ADS-B squitter reception into a unified ground-based system. The data from both channels are integrated and processed together, allowing the system to leverage the strengths of both active and passive detection methods while reducing overall system complexity through shared processing infrastructure.
2Reliability
If active Mode S All-Call interrogations are used to acquire aircraft, then real-time detection is achieved, but RF spectrum utilization increases and interference occurs in densely populated areas
Solution Approach 1:
The passive ADS-B squitter reception channel continuously monitors and acquires aircraft information in advance without requiring active radar interrogation. This preliminary acquisition of target data allows the active Mode S All-Call interrogations to be reduced or eliminated in many cases, significantly decreasing RF spectrum utilization while maintaining reliable aircraft detection and tracking.
Solution Approach 2:
Aircraft equipped with ADS-B Out transponders self-announce their position, identity, and other parameters by transmitting unsolicited squitter messages. This self-service approach eliminates the need for ground-based radar to actively interrogate each aircraft, reducing RF energy consumption and spectral interference while providing continuous real-time surveillance data.
3Measurement precision
If the antenna beam width is limited to 3 degrees to maintain narrow beam performance, then radar resolution is improved, but overlapping replies from aircraft in close proximity cause garble and information loss
Solution Approach 1:
The ground-based system universally receives replies from all directions simultaneously through the omnidirectional passive ADS-B antenna, eliminating the directional limitations of the narrow-beam monopulse antenna. This multi-functional approach allows the system to maintain narrow beam precision for active interrogation while using the omnidirectional channel to capture replies from aircraft in close proximity without garble, as each aircraft's squitter transmissions are received independently regardless of direction.
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 configuration improves the probability of detection, extends the range of target acquisition, and enhances situational awareness by merging passive and active technologies, reducing RF spectrum utilization and interference, while providing real-time detection and improved high-elevation aircraft detection within the radar's surveillance volume.
Implementation Method 1
two omni-directional ADS-B antennas...configured to receive unsolicited squittered transmissions spontaneously sent by an aircraft
Implementation Method 2
A Radio Detecting and Ranging (RADAR) system generally consists of a transmitter used to produce an electromagnetic signal, an antenna configured to radiate that signal
Implementation Method 3
radial velocity of the aircraft using the Doppler Effect
Data Source
AI summary
A monopulse secondary surveillance radar is configured to integrate replies to active interrogations and passive squitter reception into a single surveillance system, and includes: a three-channel antenna arrangement; a redundant ADS-B antenna arrangement including a first and second omnidirectional ADS-B antenna, each having a low noise amplifier, and each being integrated with a GPS antenna; and a pair of redundant four-channel interrogators. The three-channel antenna arrangement is configured to transmit interrogations, and to receive corresponding replies from an aircraft transponder. The first ADS-B antenna is coupled to a first of the pair of redundant four-channel interrogators, and the second ADS-B antenna is coupled to a second of said pair of redundant four-channel interrogators, for the monopulse secondary surveillance radar to provide real-time passive detection of ADS-B-equipped aircraft and active radar detection of aircraft to each of the pair of redundant four-channel interrogators.