PDM Pulse Timing Adjustment for Accurate Low-Noise VCO Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Voltage Controlled Oscillators (VCOs) in radar systems face accuracy issues due to low resolution analog input voltage, aging, and temperature variations, leading to increased noise from high switching activity.
Innovation Solution
A modulator comprising a bit stream adjuster that divides a PDM clock into a multi-phase clock to adjust pulse duration, increasing the resolution of the PDM stream without raising the frequency of operation, thereby enhancing VCO control accuracy and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching activity is increased to improve VCO control accuracy, then the control precision improves, but the system noise increases
Solution Approach 1:
The patent implements a dynamic switching mechanism where the bit stream adjuster adapts its switching activity based on the required resolution adjustment. By dynamically adjusting the pulse duration through selective switching of bit streams with different weights, the system achieves high control accuracy only when needed, rather than maintaining constant high switching activity, thus reducing overall noise while preserving precision capability.
Solution Approach 2:
The patent changes the parameter of switching activity by implementing a multi-bit stream architecture where different bit streams have different weights. The system selectively activates only the necessary bit streams based on the required resolution adjustment, thereby reducing the overall switching activity and associated noise while maintaining the required control accuracy for VCO frequency adjustment.
2Measurement precision
If the resolution of PDM stream is increased to improve VCO control accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent segments the high-resolution PDM stream generation into multiple lower-resolution bit streams with different weights. Instead of generating one high-resolution stream directly, the system divides it into multiple streams (e.g., MSB, middle bits, LSB) that are processed and adjusted separately, then combined to achieve the final high-resolution output. This segmentation reduces the complexity of each individual processing stage.
Solution Approach 2:
The patent introduces a bit stream adjuster as an intermediary component between the PDM encoder and the VCO control input. This adjuster acts as a mediator that performs resolution adjustment by selectively switching between different weighted bit streams, thereby achieving high-resolution control without requiring the entire system to operate at high complexity. The intermediary handles the complex resolution adjustment task in a dedicated module.
3Measurement precision
If the analog input voltage resolution is increased to improve VCO frequency accuracy, then the measurement precision improves, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the need for high-resolution analog voltage generation with a digital bit stream processing approach. Instead of manufacturing and maintaining high-resolution analog voltage sources (which would be costly and complex), the system uses digital PDM bit streams with different weights that are selectively switched to achieve the desired resolution. This substitution of digital processing for analog precision reduces manufacturing costs while maintaining frequency accuracy.
Solution Approach 2:
The patent changes the parameter of resolution from the analog domain to the digital domain. By implementing resolution adjustment through digital bit stream weighting and switching in the bit stream adjuster, the system achieves high VCO frequency accuracy without requiring costly high-resolution analog voltage generation circuitry. The resolution is achieved through digital signal processing rather than analog component precision.
Data Source
AI summary
A modulator having a pulse density modulator configured to generate from bit stream information a Pulse Density Modulation (PDM) stream based on a PDM clock; and a bit stream adjuster configured to divide the PDM clock into a PDM multi-phase clock, adjust a duration of at least one pulse of the generated PDM stream by selecting a PDM clock phase of the PDM multi-phase clock for sampling the generated PDM stream, and output an adjusted PDM stream.