Stepped Frequency Radar Multi-Port Junction Phase Coherence
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Solution Overview
Problem
Stepped frequency radars face challenges in achieving high fidelity frequency resolution and phase coherence, requiring expensive equipment, and existing ground penetrating and through-the-wall radars have limitations in identifying subsurface objects and detecting motion behind walls with high fidelity.
Innovation Solution
The use of multi-port junctions with a variable-frequency signal source to estimate a complex reflection coefficient, allowing for a low-cost, frequency-stepped radar system that operates without high-power mixing circuitry or high-speed sampling, enabling high spatial and spectral resolution through beam forming and adaptive signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional IF stages with oscillators and mixers are used in stepped frequency radars, then phase coherence and frequency resolution are maintained, but system cost increases significantly
Solution Approach 1:
The patent extracts and eliminates the expensive IF stages, oscillators, and mixers from the radar system. Instead of using traditional down-conversion architecture, the invention directly processes RF signals through a multi-port junction, removing the problematic components while maintaining the essential function of comparing transmitted and received signals.
Solution Approach 2:
The multi-port junction serves multiple functions simultaneously: it acts as a power divider, a signal combiner, and a reference signal source. By making this single component perform the roles previously distributed across multiple specialized components (oscillators, mixers, IF stages), the system achieves the same phase-coherent comparison capability at lower cost.
2Device complexity
If multi-port junctions are used to eliminate IF stages, then system cost is reduced, but the ability to maintain phase coherence for high fidelity mapping may be compromised
Solution Approach 1:
The patent merges the reference signal path and the received signal path within the multi-port junction structure. By combining these signals at the same junction where they were originally divided, the system maintains their phase relationship without requiring separate IF processing chains, thus preserving phase coherence while reducing system complexity.
Solution Approach 2:
The multi-port junction acts as an intermediary that facilitates the comparison between transmitted and received signals. It provides a common reference point and enables the extraction of reflection coefficient information through its multiple output ports, maintaining the phase relationship necessary for high-fidelity mapping without requiring traditional mixing circuitry.
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 approach enables high-fidelity radar mapping and object characterization with reduced system costs, achieving accurate detection and classification of buried objects and motion behind walls, while maintaining phase coherence and high spatial resolution.
Implementation Method 1
the output signals from the multi-port junctions are functions of both the signal source and the returned reflected signal
Implementation Method 2
a variable frequency signal source connected to one port of a multi-port junction with another port of the multi-port junction coupled to an antenna to transmit at least a portion of the signal source output
Implementation Method 3
antenna to transmit at least a portion of the signal source output and receive signals reflected from objects within the transmit beam of the antenna
Implementation Method 4
When the estimated complex reflection coefficient is processed by an Inverse Fourier Transform, then the frequency domain information is converted to time domain information
Data Source
AI summary
In the invention, a four-port junction (10) has a port (12) connected to an RF signal source (14). The four-port junction (10) also has an antenna port (16) coupled to a combined transmit/receive antenna (18). Two ports (20, 22) of the four-port junction (10) develop output power that is applied to an analogue-to-digital converter (24), that is in turn coupled to a central processor (26), that is in turn coupled to a user interface (28).