Variable Sampling Clock for IF Digitizer Aliasing Control
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Solution Overview
Problem
Conventional digitizers face challenges in sampling intermediate frequency signals due to alias effects caused by sampling frequencies lower than the Nyquist frequency, leading to interference from adjacent channels, which deteriorate the desired signal and require additional components for interference suppression.
Innovation Solution
A digitizer with a variable sampling clock system, comprising an analog to digital converter, a sampling frequency generator, and a controller that dynamically adjusts the sampling frequency to prevent aliasing of strong adjacent channel interference and optimize performance, reducing power consumption when no interference is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sampling frequency is reduced below Nyquist frequency, then power consumption is reduced and device complexity is reduced, but adjacent channel interference aliases into desired signal causing deterioration of receiving quality
Solution Approach 1:
The patent implements dynamic sampling frequency adjustment by introducing a controller that selectively changes the sampling frequency based on detected adjacent channel interference conditions. The sampling frequency generator responds to control signals to switch between different sampling rates, making the system adaptive rather than static. This resolves the contradiction by allowing low power consumption at reduced sampling rates when interference is absent, while automatically increasing sampling frequency when adjacent channel interference is detected.
Solution Approach 2:
The patent changes the sampling frequency parameter dynamically based on channel conditions. The controller detects adjacent channel interference and adjusts the sampling frequency parameter accordingly - using higher sampling frequencies when interference is present to prevent aliasing, and lower sampling frequencies when interference is absent to reduce power consumption. This parameter adaptation resolves the technical contradiction between power efficiency and interference rejection.
2Device complexity
If sampling frequency is reduced below Nyquist frequency, then device complexity is reduced by eliminating additional filter components, but alias effect causes overlapping unwanted signals into desired signal spectrum
Solution Approach 1:
The patent uses dynamic sampling frequency adjustment to maintain receiving quality without requiring complex fixed filtering components. By adaptively changing sampling frequency based on interference conditions, the system achieves reliable signal reception while keeping the device structure simple. The controller and sampling frequency generator enable this dynamic adaptation without adding physical filter components.
Solution Approach 2:
The system performs self-adjustment by detecting adjacent channel interference conditions and automatically modifying its own sampling frequency. The controller monitors channel conditions and directs the sampling frequency generator to appropriate rates, enabling the system to maintain reliability through self-regulation rather than requiring complex external filtering components.
3Reliability
If fixed high sampling frequency is used, then adjacent channel interference is prevented from aliasing, but power consumption increases and dynamic range utilization is reduced
Solution Approach 1:
The patent implements dynamic sampling frequency selection that adjusts between high and low sampling rates based on actual interference conditions. The controller detects adjacent channel interference and selectively applies high sampling frequencies only when needed for interference prevention, while using lower sampling frequencies during normal conditions to reduce power consumption. This dynamic approach resolves the contradiction between maintaining reliability and minimizing energy use.
Solution Approach 2:
The patent changes the sampling frequency parameter adaptively based on channel conditions. When adjacent channel interference is detected, the system switches to higher sampling frequencies to prevent aliasing. When interference is absent, it reduces sampling frequency to lower power consumption. This parameter modulation resolves the contradiction between interference prevention and power efficiency.
4Reliability
If fixed high sampling frequency is used, then aliasing is prevented, but dynamic range utilization is reduced due to higher power consumption
Solution Approach 1:
The patent employs dynamic sampling frequency adjustment that adapts to channel conditions. The controller monitors for adjacent channel interference and selectively increases sampling frequency only when interference is present to maintain signal quality. During normal conditions, lower sampling frequencies are used to improve dynamic range utilization and reduce power consumption, resolving the contradiction between signal quality and productivity.
Data Source
AI summary
A digitizer includes an analog to digital converter (ADC), a sampling frequency generator, and a controller. The ADC samples an IF signal to generate a digital signal. The sampling frequency generator is connected to the ADC and provides a sampling clock of variable frequency to the ADC. The controller is connected to the sampling frequency generator and determines frequency of the sampling clock.