Round-Robin RF Down-Conversion for Multi-Channel IF Sampling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current radio frequency (RF) signal conversion to intermediate frequency (IF) faces challenges such as high-speed sampling requirements, large data processing needs, and image rejection issues, making direct conversion to the digital domain costly and complex, especially for signals like GPS and digital TV signals.
Innovation Solution
A method and system that down-converts RF signals to IF signals using a round-robin FIR filter with dynamically changing coefficients, allowing for simultaneous operation on multiple channels and rejecting unwanted image signals without the need for phase-locked loops, by sampling at a rate higher than the RF frequency and mixing with a second frequency to generate an IF frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct conversion of RF signal to digital signal is performed using high-speed ADC, then conversion speed is improved, but power consumption and data processing burden increase significantly
Solution Approach 1:
The patent segments the RF signal processing into multiple parallel lower-speed ADC channels instead of using a single high-speed ADC. Each channel processes a portion of the signal spectrum at reduced sampling rates, collectively achieving the required overall conversion speed while reducing individual power consumption and data processing burden
Solution Approach 2:
The patent employs dynamic coefficient adjustment in the FIR filter, where filter coefficients are changed at a fixed rate to enable down-conversion of multiple RF channels simultaneously. This dynamic adaptation allows the system to process multiple frequency channels without requiring proportionally higher sampling rates, thereby reducing power consumption
2Device complexity
If conventional FIR filter is used for direct RF-to-digital conversion, then filtering is simplified, but transit time requirements become excessively stringent
Solution Approach 1:
The patent divides the filtering function across multiple parallel processing channels, each operating at relaxed transit time requirements. By segmenting the overall filtering task into parallel sub-tasks, the system achieves the required filtering performance without demanding excessively short transit times in any single stage
Solution Approach 2:
The patent uses periodic coefficient updates in the FIR filter, where coefficients are changed at a fixed rate to enable multi-channel down-conversion. This periodic action allows the filter to adapt to different frequency channels while maintaining manageable transit time requirements through structured coefficient modulation
3Adaptability or versatility
If high-speed ADC operating at 2.5 GS/s is used, then signal conversion capability is improved, but data output rate becomes excessively high requiring complex transport and processing
Solution Approach 1:
The patent segments the high-speed conversion task into multiple parallel lower-speed ADC channels. Each channel operates at a reduced sampling rate (e.g., 250 MS/s instead of 2.5 GS/s), producing proportionally less data per channel. The combined output of multiple channels achieves the required overall conversion capability while keeping individual data rates manageable
Solution Approach 2:
The patent creates a universal down-conversion system that can process multiple RF channels simultaneously through a single integrated architecture. The system uses software-configurable filter coefficients to adapt to different frequency channels, eliminating the need for separate hardware paths and reducing overall system complexity despite handling multiple channels
4Reliability
If conventional heterodyne receiver is used for down-conversion, then image rejection is achieved, but device complexity increases with additional components
Solution Approach 1:
The patent replaces the traditional mechanical/analog heterodyne architecture with a digital signal processing approach. Image rejection is achieved through digital FIR filtering and coefficient modulation rather than through analog mixers and local oscillators, simplifying the physical receiver structure while maintaining or improving image rejection performance
Solution Approach 2:
The patent introduces software-configurable filter coefficients as an intermediary between the ADC and output stages. These dynamically adjustable coefficients act as a mediator that enables flexible frequency selection and image rejection without requiring additional physical components, achieving heterodyne-like functionality through digital processing
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 enables efficient and cost-effective simultaneous down-conversion of multiple RF channels to a narrower IF range, reducing the need for high-speed ADCs and frequency-specific elements, allowing for flexible, software-defined radio operations.
Implementation Method 1
to convert an analog signal to a digital signal, an ADC must sample the analog signal at a rate at least twice as fast as the signal itself
Implementation Method 2
converting the down-converted IF signal into the digital domain. An analog-to-digital converter (ADC) is used to transform the analog IF signal into a digital data stream
Data Source
AI summary
A method and system is disclosed for designing a radio for down-converting RF signals to IF signals by sampling the signals in a round-robin sampling circuit and multiplying the samples by coefficients that are changed at a fixed rate equal to the rate of operation of each of the sampling circuits. The circuit is able to down-convert multiple channels simultaneously to adjacent positions in the IF band, while rejecting unwanted image signals. The method and system avoids the difficulty and cost of directly digitizing the RF signal, allowing each component to operate at a greatly reduced speed. The coefficients are selected to provide the desired transfer function while keeping the output signal centered at a desired frequency.