Compact Microwave Imaging Receiver Architecture
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Solution Overview
Problem
Microwave radiometers implemented on silicon integrated circuits face challenges due to increased receiver noise figure and deteriorated imaging resolution caused by fluctuations in receiver gain, which existing architectures attempt to address but often require lossy and difficult-to-implement components like couplers and accurate terminations.
Innovation Solution
A compact, balanced microwave imaging receiver architecture that uses two 90° couplers and high-gain amplifiers, followed by phase splitters and SPDT switches to minimize noise and coupler count, allowing for efficient implementation on silicon with reduced noise penalty and accurate Dicke switch functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an SPDT Dicke switch is placed in front of the amplifier to compensate for gain variations, then the imaging resolution is improved by making ΔT independent of receiver gain variations, but the receiver noise figure increases and Tsys increases, deteriorating the imaging resolution
Solution Approach 1:
The patent inverts the conventional Dicke switch architecture by placing the SPDT switch after the amplifier instead of before it. This reversal allows the switch to operate at lower power levels where silicon switches have lower noise figures, while still achieving the desired gain variation compensation. The amplifier processes the full-power signal first, then the switch directs the amplified signal to different paths (antenna or reference load) without introducing the noise penalty associated with switching at high power levels.
Solution Approach 2:
The patent introduces an intermediary approach by using the amplifier as a buffer between the antenna/input and the Dicke switch. This intermediary element allows the switch to operate in a lower-noise regime while still performing its function of comparing antenna and reference signals. The amplifier acts as a mediator that isolates the noisy switch from the sensitive antenna input.
2Measurement precision
If a balanced topology is used to reduce noise, then the imaging resolution is improved, but the device complexity increases due to requiring at least four couplers and accurate terminations
Solution Approach 1:
The patent extracts the essential functionality of the balanced topology (noise reduction through differential processing) while removing the complex components (multiple couplers and precise terminations). By using a single coupler combined with phase splitters and an in-phase/quadrature detector, the patent achieves the noise reduction benefits of balanced detection without requiring the full complement of couplers and terminations specified in traditional balanced topology designs.
Solution Approach 2:
The patent makes the single coupler perform multiple functions: it serves as the primary signal splitting element, enables balanced detection when combined with phase splitters, and provides the reference signal path. The phase splitters and detector further multi-functionalize the system by enabling both phase comparison and amplitude detection capabilities from the same coupler output, reducing the total component count while maintaining balanced topology benefits.
3Object-affected harmful factors
If hybrid ring couplers are used to implement balanced topology, then the noise performance is improved, but the ease of manufacture decreases due to lack of balanced topology and difficulty of silicon implementation
Solution Approach 1:
The patent replaces the mechanical/physical hybrid ring coupler structure with an electrical implementation using standard silicon-compatible components. Instead of relying on the physical geometry and routing of hybrid rings that are difficult to fabricate on silicon, the patent uses conventional couplers combined with electronic phase splitters and active detector circuits. This substitution maintains the noise reduction benefits while achieving compatibility with standard silicon CMOS or bipolar fabrication processes.
Data Source
AI summary
A system and method is shown for receiving microwave/millimeter-wave signals. The system and method are balanced and can be effectively implemented on a silicon substrate using single pole double throw switches.