Spectrum Analyzer Noise Floor Subtraction for Dynamic Range Expansion
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Solution Overview
Problem
Spectrum analyzers face a narrowed dynamic range due to increased input levels, which raise the noise floor level caused by the dominant noise of the analog/digital converter, affecting the frequency response and overall signal analysis.
Innovation Solution
A signal analysis apparatus and method that includes noise floor level subtraction means to correct the noise level of the analog/digital conversion means, expanding the dynamic range by subtracting the noise level of the analog/digital converter from the overall noise floor level in a predetermined frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the input level of the mixer is increased, then the signal level is improved, but the noise floor level increases due to dominant ADC noise
Solution Approach 1:
The patent converts the harmful ADC noise into a measurable and correctable parameter. By measuring the noise floor at different attenuation levels and calculating the ADC noise contribution, the system quantifies the harmful effect and then subtracts it from the total noise floor measurement, transforming the ADC noise from an unacceptable interference into a correctable component.
Solution Approach 2:
The patent introduces an intermediary calculation process that separates the total noise floor into two components: analog stage noise and ADC noise. By using the attenuation level as an intermediary variable, the system can distinguish between these noise sources and selectively remove the ADC contribution, allowing the beneficial analog noise to remain while eliminating the harmful digital quantization noise.
2Power
If the variable attenuator gain is increased to raise the mixer input level, then the signal strength is improved, but the dynamic range is narrowed
Solution Approach 1:
The patent transforms the limiting factor (ADC noise) into a calculable and removable component. By identifying and subtracting the ADC noise contribution from the total noise floor, the system recovers the dynamic range that would otherwise be lost, allowing higher signal levels to be processed without permanently sacrificing measurement precision.
3Measurement precision
If the noise floor level is raised by ADC noise dominance, then the measurement sensitivity is reduced, but the frequency response correction becomes less effective
Solution Approach 1:
The patent converts the degrading ADC noise into a correctable offset. By calculating and subtracting the ADC noise contribution from the measured noise floor, the system recovers the true analog stage noise characteristics, which are necessary for effective frequency response correction and maintain measurement sensitivity across the full frequency range.
Data Source
AI summary
To provide a signal analysis apparatus and a signal analysis method which can expand a dynamic range. A spectrum analyzer 1 includes a frequency conversion unit 10 that includes an S-ATT 11 which adjusts the level of an analog input signal and converts the input signal into a predetermined intermediate frequency signal, a V-ATT 21 that adjusts the level of an output signal from the frequency conversion unit 10, an ADC 23 that converts an output signal from the V-ATT 21 into a digital signal, an f-response correction filter 24 that corrects the frequency response of an output signal from the ADC 23, and a noise floor level subtraction unit 25 that subtracts the noise level of the ADC 23 from a noise floor level indicating an overall noise level of the S-ATT 11 to the f-response correction filter 24 in a predetermined frequency band.