Digital Sweep Spectrum Analyzer Up-Down Frequency Conversion
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Solution Overview
Problem
Existing swept spectrum analyzers with analog components are not stable and provide less accuracy compared to fully digital solutions, and they require longer analysis time for frequency conversion.
Innovation Solution
A digital sweep type spectrum analysis system with up/down frequency conversion that quantizes complex analog input signals into three levels and uses a block of 9-to-1 multiplexers, registers, and adders to perform equivalent complex multiplication without real multiplications, forming up-shifted and down-shifted complex signals, which are then processed by accumulators and analyzed for spectral estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional down frequency conversion is used, then frequency spectrum measurement is achieved, but analysis time is long
Solution Approach 1:
The patent implements dynamic up/down frequency conversion by controlling the local oscillator to sweep through frequency ranges, enabling the system to adaptively convert signals both upward and downward in frequency. This dynamic approach allows simultaneous processing of multiple frequency components, reducing analysis time while maintaining measurement accuracy.
Solution Approach 2:
The patent maintains continuous frequency conversion operations by implementing a seamless up/down conversion process. The local oscillator continuously sweeps through frequency ranges, and the signal processing chain operates without interruption, ensuring continuous spectrum analysis and reducing total analysis time compared to traditional sequential down-conversion methods.
2Device complexity
If analog components are used in spectrum analyzer, then device complexity is reduced, but stability and accuracy deteriorate
Solution Approach 1:
The patent replaces analog/m mechanical signal processing components with digital signal processing operations. The frequency conversion and spectrum analysis are performed using digital multiplexers, adders, and accumulators, eliminating the need for complex analog mixing and filtering hardware while improving stability and accuracy.
Solution Approach 2:
The patent changes the operational parameters of the frequency converter by implementing digital control of the local oscillator frequency and using digital signal processing techniques. This allows precise control of conversion parameters and eliminates analog component tolerances and drift, improving both reliability and measurement accuracy.
3Measurement precision
If multiplication operations are used for frequency conversion, then frequency spectrum measurement is achieved, but computational complexity increases
Solution Approach 1:
The patent segments the complex multiplication operation into separate processing paths for in-phase and quadrature components. By using 9-to-1 multiplexers to selectively route signals and combiners to sum the components, the system performs frequency conversion without requiring general-purpose multipliers, reducing computational complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces intermediate signal paths with multiplexers and combiners that mediate between the input signal and the frequency conversion process. These intermediaries enable the system to perform frequency conversion through selective signal routing and addition rather than direct multiplication, simplifying the computational requirements.
Data Source
AI summary
System for digital sweep type spectrum analysis with up/down frequency provides measurements of frequency spectrum of complex analog baseband input signal. The signal is quantized into three levels with fs based on the bandwidth of the input signal. Four multiplexers, a first block of registers and a block of adders perform operations equivalent to complex multiplication of the quadrature components. Two complex signals with up and down shifted spectrum are produced by the adders. The quadrature components are inputted to the accumulators with reset, which act as low-pass filters and accumulate several samples at a constant frequency fLO of the local oscillator. Levels of two accumulated complex samples are estimates of input signal spectrum in two frequency points +fLO and −fLO. A sweep controller changes a frequency of the local oscillator from zero up to fs/2. Estimates of the input signal spectrum are generated sequentially in range −fs/2 to +fs/2.