Single-Beam Phased Array Tracking Using Monopulse Beam Jitter
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Solution Overview
Problem
Ground satellite communication terminals require a method for monopulse tracking using a single beam phased array antenna, as they need to quickly point and hand off beams to track satellites in lower Earth orbit, which electronically steered antennas cannot efficiently achieve with traditional methods.
Innovation Solution
The method involves synthesizing summation and difference beams using amplitude and phase control in a phased array antenna, allowing for rapid beam steering and monopulse tracking by jittering the beam within acceptable deviation angles to maintain communication links, thereby eliminating the need for multiple antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single beam phased array antenna is used for tracking, then device complexity is reduced, but tracking accuracy deteriorates
Solution Approach 1:
The patent segments the beam pattern into multiple components by introducing controlled jitters in different directions (azimuth and elevation). The single beam is divided into multiple sampled positions that form a virtual monopulse pattern, enabling differential measurements without multiple physical antennas
Solution Approach 2:
The patent applies dynamic beam steering by continuously jitting the beam position around the nominal tracking point. This dynamic movement creates a time-varying beam pattern that can be processed to extract directional error signals, transforming a static single-beam system into a dynamic tracking system
2Measurement precision
If traditional monopulse tracking is used with multiple feed ports, then tracking accuracy is improved, but device complexity increases
Solution Approach 1:
The patent creates virtual copies of the monopulse measurement capability through digital signal processing. Instead of having multiple physical feed ports that physically sample different parts of the beam, the system digitally synthesizes multiple beam patterns by processing signals from a single feed port with introduced jitters
Solution Approach 2:
The patent replaces the mechanical/physical structure of multiple feed ports with an electronic/digital system. The physical monopulse antenna structure is substituted by an electronic beam steering and signal processing system that achieves the same tracking function through phase and amplitude control
3Productivity
If beam jitter is introduced for tracking, then tracking capability is enabled, but signal stability deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the signal strength at the jittered beam positions and using this information to determine the correct tracking direction. The error signals generated from comparing adjacent beam positions are fed back to adjust the beam pointing, creating a closed-loop tracking system
Solution Approach 2:
The patent applies periodic beam jittering at controlled intervals to sample the signal environment around the nominal beam position. This periodic action allows the system to build up statistical information about signal variations and distinguish between jitter-induced variations and actual tracking errors
Data Source
AI summary
A need exists for a method to do monopulse tracking with a single beam phased array antenna. With a monopulse tracker antenna, the satellite, or moving target, will have a beacon signal that the tracker can acquire. The beacon signal may be a preamble in the transmitted signal from the satellite. The monopulse tracker antennas are scanned over the volume, minimizing the error signal. When the error signal is minimal, the antenna is pointed in the direction of the satellite or moving target. Because the tracker needs to know direction offsets in both azimuth and elevation planes, error signals from both planes are needed. The monopulse tracker antenna maintains a radio frequency link to the beacon signal, causing the antenna to lock in the direction of the satellite when the error signal is minimized to zero.