Radio Receiver Aliasing Detection via Nyquist Frequency Translation
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Solution Overview
Problem
Existing radio receivers face challenges in efficiently detecting and handling aliasing effects, which can cause interference and loss of information, despite the use of anti-aliasing filters and variable sampling rates.
Innovation Solution
The solution involves performing frequency translation operations on an oversampled baseband signal to estimate and detect aliasing effects by comparing signal levels before and after translation, allowing for the detection of obtruding signals and subsequent adaptation of receiver parameters to mitigate these effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an anti-aliasing filter is applied prior to analog-to-digital conversion, then aliasing effects are reduced, but some aliasing effects still remain and cannot be completely eliminated
Solution Approach 1:
The patent applies preliminary action by performing frequency translation on the oversampled baseband signal before detecting aliasing effects. The frequency translator translates the signal such that content around zero frequency is translated to around the nominal sample frequency and vice versa, allowing detection of aliasing effects that would otherwise be masked. This preliminary transformation enables more reliable detection and handling of remaining aliasing effects.
2Use of energy by moving object
If a lower sampling rate is used, then power consumption is reduced, but aliasing effects become more problematic when undesirable signals are present
Solution Approach 1:
The patent applies dynamics by making the sampling rate variable rather than fixed. The system dynamically adjusts the sampling rate based on detected aliasing effects and signal conditions. When aliasing effects are detected or undesirable signals are present, the sampling rate can be increased to mitigate aliasing, while during normal conditions a lower sampling rate can be used to save power. This dynamic adaptation resolves the contradiction between power consumption and aliasing mitigation.
3Object-affected harmful factors
If the sampling rate is varied to handle aliasing, then aliasing effects can be managed, but the system complexity increases due to rate variation mechanisms
Solution Approach 1:
The patent applies feedback by using the detected aliasing effects information to control the sampling rate variation. The frequency translator and detector form a feedback loop that monitors for aliasing effects and provides this information to control the analog-to-digital converter's sampling rate. This feedback mechanism allows the system to automatically adjust sampling rate based on actual signal conditions, managing aliasing effects while keeping the control logic relatively simple and integrated within the existing receiver architecture.
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 effectively identifies and manages aliasing effects, improving signal reception by allowing for adjustments in filtering and sampling rates, thereby reducing interference and enhancing the accuracy of signal processing.
Implementation Method 1
a mixer arranged to mix a received signal to an analog baseband signal at or close to zero-frequency
Implementation Method 2
a frequency translator arrangement arranged to translate the digital baseband signal around a Nyquist frequency being based on a nominal sample frequency
Data Source
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AI summary
A method of detecting an obtruding signal in a radio receiver, a receiver and a computer program are disclosed. The receiver has a mixer arranged to mix a received signal to an analog baseband signal at or close to zero-frequency, a filter arranged to low-pass filter said analog baseband signal, and an analog-to-digital converter arranged to sample said filtered analog baseband signal at a sample frequency such that a digital baseband signal is formed. The method comprised receiving a radio frequency signal, mixing the radio frequency signal to the analog baseband signal at or close to zero-frequency, low-pass filtering said analog baseband signal, and analog-to-digital converting said filtered analog baseband signal at an over sample frequency such that a digital baseband signal is formed. The method further comprises frequency translating the digital baseband signal around a Nyquist frequency being based on a nominal sample frequency, the nominal sample frequency being a fraction of the oversampling frequency according to the oversampling rate, to form a translated digital baseband signal such that signal content of the digital baseband signal around zero frequency will be translated to around the nominal sample frequency and vice versa in the translated digital baseband signal, determining a first signal level at zero frequency of the digital baseband signal and a second signal level at zero frequency of the translated digital baseband signal, detecting an obtruding signal based on a relation between the first and second signal levels, and outputting an obtruding signal state signal.