Undersampled Signal Receiver with Frequency Shifting
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Solution Overview
Problem
In undersampled wireless radio communication systems, low sample rates in analog-to-digital converters lead to aliasing of interfering signals onto the desired signal, necessitating costly narrow band RF filters to separate them, increasing system costs.
Innovation Solution
An apparatus and method that downconverts input signals using a local oscillator and bandpass filter, generates a discrete-time spectrum through undersampling, and employs a signal processor to determine the presence of interfering signals by shifting the local oscillator frequency, allowing for the separation of desired signals from interfering signals without additional cost through periodic analysis and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low sample rate analog-to-digital converters are used, then system cost is reduced, but interfering signals are aliased onto the desired signal
Solution Approach 1:
The patent performs preliminary frequency analysis of the discrete-time spectrum before final signal processing. By analyzing the spectrum in advance and identifying aliased interfering signals, the system can detect their presence and take appropriate processing actions, preventing interference from corrupting the desired signal measurement
Solution Approach 2:
The patent introduces an intermediary analysis step between the analog-to-digital conversion and final signal processing. The frequency spectrum analysis acts as a mediator that identifies interfering signals, allowing the system to distinguish between desired signals and aliased interference without requiring expensive RF filtering hardware
2Object-affected harmful factors
If narrow band RF filters are added to remove interfering signals, then signal separation is improved, but system cost increases
Solution Approach 1:
The patent replaces the mechanical/electrical RF filtering system with a digital signal processing approach. Instead of using physical narrow band RF filters to remove interfering signals, the system uses digital frequency spectrum analysis and processing to identify and separate desired signals from aliased interference, eliminating the need for expensive analog filtering hardware
Solution Approach 2:
The patent changes the operating parameters of the system by using undersampling techniques that deliberately allow aliasing to occur, then compensating through digital processing. By changing from a traditional high-sample-rate approach to controlled undersampling with digital analysis, the system achieves signal separation without requiring expensive RF filters
3Ease of manufacture
If undersampling is performed, then converter cost is reduced, but aliasing of interfering signals occurs
Solution Approach 1:
The patent implements a feedback mechanism where the frequency spectrum of the undersampled signal is continuously analyzed. By monitoring the spectrum for signs of aliased interfering signals and adjusting the processing accordingly, the system maintains signal integrity despite the information loss inherent in undersampling
Solution Approach 2:
The patent introduces an intermediary frequency analysis step that acts as a mediator between the undersampled signal and final processing. This analysis identifies aliased signals and allows the system to distinguish them from desired signals, preventing information loss from corrupting the measurement
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
Effectively separates desired signals from interfering signals within the discrete-time spectrum, reducing the need for costly RF filters and maintaining system performance, thereby lowering overall radio communication system costs.
Implementation Method 1
a signal converter for downconverting an input signal using a local oscillator
Implementation Method 2
a bandpass filter for generating an analog spectrum
Implementation Method 3
an analog-to-digital converter for generating a discrete-time spectrum by undersampling the analog spectrum such that aliasing of communications channel frequencies occurs within the discrete-time spectrum
Data Source
AI summary
Described herein are methods and apparatuses for receiving a desired signal at a signal receiver with an undersampling frequency. A signal converter with a local oscillator frequency, a bandpass filter, and an analog-to-digital converter are used to generate an aliased discrete-time spectrum from an input analog spectrum. In order to determine the presence of interfering signals in the aliased discrete-time spectrum and, if present, separate a desired signal from the interfering signal, the local oscillator frequency is shifted. The original discrete-time spectrum and the resulting shifted discrete-time spectrum are both analyzed to select a local oscillator frequency that does not cause interference with the desired signal when the discrete-time spectrum is generated. The selected local oscillator frequency is then utilized to process the desired signal.