Ring Oscillator Biasing for Controlled Supply Voltage Sensitivity
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Solution Overview
Problem
Ring oscillators in wireless communication systems exhibit poor power supply rejection, which affects their performance in voltage-controlled oscillator (VCO)-based applications, necessitating improved sensitivity to supply voltage for high digital resolution.
Innovation Solution
A method and apparatus are introduced to control the supply sensitivity of a ring oscillator stage by generating bias signals for PMOS and NMOS transistors based on the supply voltage, allowing for triode degeneration biasing and enhanced sensitivity to supply voltage variations, thereby improving the oscillator's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring oscillator is used in a PLL, then the oscillator can generate signals at desired frequencies, but the power supply rejection is poor
Solution Approach 1:
The patent changes the biasing parameters of the ring oscillator by introducing voltage-controlled degeneration resistors that modify the transistor operating points dynamically. This allows the oscillator to maintain stable frequency generation while becoming controllable in its sensitivity to supply voltage variations, resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The patent implements feedback through voltage biasing modules that sense the supply voltage and adjust the degeneration resistor values accordingly. This feedback mechanism allows the system to automatically compensate for supply voltage variations, improving power supply rejection while maintaining the ability to control sensitivity when needed.
2Measurement precision
If the ring oscillator is made highly sensitive to supply voltage for VCO-based quantizer, then digital resolution increases, but power supply rejection deteriorates
Solution Approach 1:
The patent makes the oscillator's sensitivity dynamic rather than fixed. By using voltage-controlled degeneration resistors, the system can switch between high sensitivity mode (for high digital resolution in VCO-based quantizer) and low sensitivity mode (for better power supply rejection), allowing optimal performance for different operational requirements.
Solution Approach 2:
The patent changes the electrical parameters of the oscillator by adjusting the degeneration resistor values through voltage control. This enables the system to optimize the trade-off between measurement precision and power supply rejection based on the specific application requirements.
3Device complexity
If traditional biasing is used, then the circuit is simple, but supply sensitivity control is insufficient
Solution Approach 1:
The patent introduces voltage biasing modules as intermediary components between the power supply and the ring oscillator. These modules act as mediators that provide precise control over the oscillator's supply sensitivity without requiring complete redesign of the basic oscillator circuit, thus maintaining relative simplicity while achieving superior control.
Data Source
AI summary
A method and apparatus for controlling a supply sensitivity of a ring oscillator stage are provided. The apparatus is configured to generate, via a voltage biasing module, a first bias signal for a PMOS biasing module based on a supply voltage and a second bias signal for a NMOS biasing module based on the supply voltage, bias, via the PMOS biasing module, triode PMOS degeneration of the inverting module based on the first bias signal, bias, via the NMOS biasing module, triode NMOS degeneration of the inverting module based on the second bias signal, receive an input via an inverting module, and output, via the inverting module, an inverted version of the received input based on the biased triode NMOS degeneration and the biased triode PMOS degeneration.