Digital Receiver Architecture for Image Rejection and CMOS Integration
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Solution Overview
Problem
Conventional analog super-heterodyne receivers are large, costly, and consume high power due to their analog nature, making them unsuitable for integration into microchips and requiring significant pre-conversion filters and high-quality narrow band IF filters, which limits their compatibility with digital designs and increases power consumption.
Innovation Solution
A digital receiver architecture utilizing complex multiplication with sampling mixers and discrete signal processing to achieve image rejection, allowing for the separation of wanted and image frequencies in the digital domain, which can be followed by complex band-pass filtering to completely remove image frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional analog super-heterodyne receivers are used, then RF reception can be accomplished with fixed intermediate frequency filtering, but the receiver size, cost, and power consumption increase significantly
Solution Approach 1:
The patent replaces the mechanical analog filtering system with a digital signal processing system. The analog super-heterodyne receiver architecture is substituted with a direct conversion receiver that uses digital intermediate frequency processing, thereby eliminating the need for physical filters and reducing power consumption while maintaining reception reliability
Solution Approach 2:
The patent changes the operating parameters by moving the intermediate frequency processing to the digital domain. By performing frequency conversion and filtering operations digitally rather than analog, the system achieves the same functional results with lower power consumption and without requiring large analog filter components
2Reliability
If analog super-heterodyne receivers with narrow band IF filters are used, then image frequency rejection can be achieved, but the receiver cannot be easily integrated onto an integrated circuit
Solution Approach 1:
The patent replaces physical analog filters with digital signal processing algorithms. The narrow band IF filters that are difficult to integrate are substituted with digital filtering operations that can be easily implemented on integrated circuits, maintaining image rejection capability while improving manufacturability
Solution Approach 2:
The digital signal processing architecture provides multi-functionality, allowing the same integrated circuit to perform both frequency conversion and filtering operations. This universal approach eliminates the need for separate analog filter components, making the receiver easily integrable onto a single chip while maintaining reliable image frequency rejection
3Object-affected harmful factors
If significant pre-conversion filters and high quality narrow band IF filters are used, then unwanted interference can be attenuated, but the receiver size and cost increase
Solution Approach 1:
The patent replaces large physical pre-conversion filters and narrow band IF filters with digital signal processing. The attenuation of unwanted interference is achieved through digital filtering algorithms rather than physical filter components, dramatically reducing the receiver size while maintaining the ability to reject interference
Solution Approach 2:
The patent extracts the filtering function from the physical domain and relocates it to the digital domain. By separating the interference rejection function from physical filter hardware and implementing it as a digital signal processing operation, the system achieves the same interference attenuation with minimal physical footprint
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 results in a receiver with higher selectivity, sensitivity, and fidelity, offering lower power consumption and smaller size compared to conventional analog designs, while being more compatible with digital logic devices and enabling efficient image separation and filtering.
Implementation Method 1
A mixer mixes the amplified RF signal with a local oscillator (LO) frequency signal to convert the band-limited RF signals to an IF band along with undesired mixing products
Implementation Method 2
Each digital filter is designed to reject as much as possible of unwanted frequencies, without distorting the desired signal
Data Source
AI summary
A digital communication circuit can be implemented can be implemented in a CMOS, or other IC structure. The digital circuit can utilize negative frequency removers or image frequency removers in the digital domain. The circuit can include mixers, switches, a complex filter, a low noise amplifier and summers. The image frequency can be removed digitally.