SIW Microwave Receiver Layout for Low-Noise Image Rejection
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Solution Overview
Problem
Microwave receivers for satellite applications face challenges in achieving high performance, miniaturization, and cost-effectiveness due to the need for high gain and low noise while managing thermal noise and out-of-band signals, often requiring bulky and expensive image rejection filters and complex shielding, which increase mass and complexity.
Innovation Solution
A microwave receiver design featuring a multilayer electronic board with integrated low noise amplifiers and image rejection filters using Substrate Integrated Waveguide (SIW) technology, where the image rejection filter is positioned between amplification stages, eliminating the need for external shielding and reducing parasitic couplings, thus minimizing size, weight, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional image rejection filters with metal cavity shielding are used, then out-of-band signal rejection is improved, but device mass and volume increase
Solution Approach 1:
The patent replaces traditional mechanical metal cavity shielding with an integrated PCB-based filtering structure using SIW technology. The image rejection filter is implemented as conductive patterns on PCB layers rather than separate metal enclosures, eliminating the need for bulky mechanical shielding while maintaining signal rejection performance.
Solution Approach 2:
The patent merges the image rejection filter, amplification stages, and shielding functions into a single integrated PCB assembly. The filter structure is formed by conductive layers and vias within the PCB itself, combining multiple previously separate components into one unified structure that reduces overall mass and volume.
2Object-affected harmful factors
If image rejection filter is positioned before first amplification stage, then out-of-band signal rejection is improved, but system noise increases due to filter attenuation in passband
Solution Approach 1:
The patent segments the filtering function across multiple stages: a first image rejection filter before the first amplification stage and a second image rejection filter between amplification stages. This segmentation allows each filter to operate with optimized characteristics, maintaining signal-to-noise ratio while achieving effective out-of-band rejection.
Solution Approach 2:
The patent changes the operational parameters of the filters by implementing them as SIW structures with specific geometric configurations (via hole patterns, conductor trace dimensions) that optimize both passband attenuation and stopband rejection. The filter parameters are tuned to minimize impact on desired signal while maximizing rejection of unwanted frequencies.
3Power
If multiple integrated amplification circuits are connected in cascade to achieve high gain, then amplification performance is improved, but parasitic electromagnetic couplings and oscillations increase
Solution Approach 1:
The patent introduces image rejection filters as intermediary elements between cascaded amplification stages. These filters serve as isolation barriers that block parasitic electromagnetic couplings and prevent oscillations while allowing the desired signal to pass through with proper gain amplification.
Solution Approach 2:
The patent uses the third dimension (vertical layering in multilayer PCB) to separate amplification stages and reduce parasitic couplings. By placing amplifiers on different PCB layers and using via holes for vertical connections, the design minimizes electromagnetic interference between stages while maintaining compact form factor.
4Object-affected harmful factors
If separate metal cavity shielding is used for each integrated circuit, then electromagnetic interference is reduced, but device mass and manufacturing complexity increase
Solution Approach 1:
The patent merges individual component shielding into a unified PCB-based shielding structure. The ground planes, conductive layers, and via walls in the PCB assembly collectively provide electromagnetic shielding for all components without requiring separate metal enclosures for each integrated circuit, simplifying manufacturing and reducing mass.
Solution Approach 2:
The PCB structure serves multiple functions simultaneously: it provides mechanical support, electrical interconnections, signal routing, and electromagnetic shielding. This multi-functionality eliminates the need for separate shielding components and simplifies the overall manufacturing process.
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 design achieves optimal signal/noise ratio with reduced size, weight, and cost, enhancing reliability and simplifying design and manufacturing processes, while maintaining high gain and low noise performance without the need for complex shielding structures.
Implementation Method 1
image rejection filters using Substrate Integrated Waveguide (SIW) technology
Implementation Method 2
the thermal noise superimposed on the signal of interest, partly picked up by the receiving antenna, and partly generated by the components of the receiver itself
Data Source
Figure 1~2a
Figure 3~4
AI summary
The invention concerns a microwave receiver device for satellite applications, suitable to be used in high-speed transmission radio telecommunication systems. The receiver device comprises at least one amplifier (11), an image rejection filter (12) and at least one electronic board (20) supporting the amplifier (11) and the filter (12). The amplifier (11) comprises at least a first amplification stage (11A) and a second amplification stage (11B) and the image rejection filter (12) is positioned between said first (11A) and said second amplification stage (11B).The electronic board (20) comprises at least one dielectric substrate (22, 22A, 22B) and at least two conductive layers (21, 21A, 21B, 21C) each disposed on a surface of the dielectric substrate (22, 22A, 22B) The image rejection filter (12) is integrated in the electronic board (20) and is defined by cavities (25, 125) made in the at least one dielectric substrate (22; 22A, 22B) and delimited by a row (26, 126) of metallized connection holes (27).