Interleaved Radar Sub-Arrays for Low-Spurious Pulse Modulation
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Solution Overview
Problem
Microwave frequency pulse transmission systems face challenges in reducing spurious emissions and heat dissipation due to the linearity requirements and inefficiencies in existing modulation methods, particularly with microwave frequency transistors operating in class C, which lead to uncontrollable amplitude oscillations and high heat dissipation.
Innovation Solution
The method involves transmitting two pulse waves with opposing phase shifts through interleaved sub-arrays of radiating elements, using phase shifters to modulate the rising and falling edges of the pulse waves, allowing for efficient amplitude modulation outside the transmission system, thereby reducing heat dissipation and maintaining spectral purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microwave frequency transistors are used for pulse transmission, then transmission efficiency is improved, but spurious emissions increase due to switched edges
Solution Approach 1:
The patent divides the antenna array into two sub-arrays (odd and even elements) that transmit pulse waves with opposite phase shifts. This segmentation allows the harmful switched edges to be distributed and cancelled out in the combined signal, reducing spurious emissions while maintaining transmission efficiency through the microwave frequency transistors.
Solution Approach 2:
The patent applies preliminary phase shifting (±π/2) to the pulse waves before transmission. By pre-modulating the phase of each sub-array, the switched edges generated by the transistors are transformed into controlled phase transitions that cancel harmonics when combined, preventing spurious emissions rather than addressing them after generation.
2Object-generated harmful factors
If power supply modulation is used to reduce spurious emissions, then spectral purity is improved, but device complexity increases due to sophisticated power supply controls
Solution Approach 1:
The patent replaces the mechanical/electrical power supply modulation system with a phase shifting system. Instead of modulating the power supply voltage to control amplitude and reduce emissions, the invention uses phase shifters to modulate the phase of pulse waves, achieving spectral purity through phase cancellation rather than power control, thereby avoiding complex power supply circuitry.
3Manufacturing precision
If linear amplification zone is used for amplitude modulation, then waveform control is improved, but heat dissipation increases and efficiency decreases
Solution Approach 1:
The patent changes the modulation parameter from amplitude (which requires linear operation and causes heat dissipation) to phase. By modulating the phase of pulse waves instead of their amplitude, the system achieves precise waveform control while allowing the transistors to operate in efficient non-linear modes, significantly reducing heat dissipation.
4Productivity
If class C operation is used for microwave frequency transistors, then efficiency is improved, but power supply modulation becomes difficult to control
Solution Approach 1:
The patent replaces power supply modulation with phase shifting modulation. Since class C transistors are efficient but difficult to modulate via power supply, the invention uses phase shifters to control the output, allowing the transistors to operate in efficient class C mode while achieving the required modulation through phase changes rather than power supply changes.
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 simplifies the modulation process, reduces heat dissipation, and maintains spectral purity by applying phase shifts to the pulse waves, overcoming the constraints of linearity requirements and achieving efficient amplitude modulation without the need for complex power supply controls.
Implementation Method 1
two pulse waves are transmitted, each modulated by a phase shift law known as modulation phase shift
Implementation Method 2
the transmitted wave being the combination of said first wave and said second wave
Data Source
AI summary
A wave transmitted by an antenna made up of an array of radiating elements, two pulse waves are transmitted, each modulated by a phase shift law known as modulation phase shift, the phase shifts being in opposition, a first wave being transmitted by a sub-array of radiating elements referred to as odd and the second wave being transmitted by a second sub-array of radiating elements referred to as even, the two sub-arrays being interleaved, the transmitted wave being the combination of the first wave and the second wave.