High-Speed Serial Oscillator With Parallel Inductors Against Injection Pulling
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Solution Overview
Problem
Differential L-C oscillator circuits in high-speed transceiver circuits face challenges in achieving good quality factors (Q-factors) and are susceptible to injection pulling, especially as data rates increase, leading to degraded performance and increased jitter.
Innovation Solution
The use of multiple parallel inductors in the oscillator circuit to achieve desired inductance without reducing the quality factor, combined with a variable capacitance element and a current source configuration to mitigate injection pulling by arranging inductors to cancel out magnetic flux vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of inductors is decreased to support higher data rates, then the oscillator can operate at higher speeds, but the quality factor degrades and the oscillator becomes more susceptible to injection pulling
Solution Approach 1:
The patent divides a single inductor into multiple smaller inductors connected in parallel. This segmentation allows the oscillator to operate at higher data rates while maintaining good quality factors, as each smaller inductor has better Q-factor characteristics than a single large inductor would provide at the same total inductance value.
Solution Approach 2:
The patent combines multiple inductors in parallel to achieve the desired total inductance while benefiting from the superior quality factors of smaller individual inductors. The merged configuration also provides magnetic flux cancellation that reduces injection pulling susceptibility.
2Speed
If the size of inductors is decreased to support higher data rates, then the oscillator can operate at higher speeds, but the oscillator becomes more susceptible to injection pulling
Solution Approach 1:
The patent arranges multiple inductors with opposite current directions so that their magnetic flux vectors cancel each other out. This counteracting configuration reduces the net magnetic field external to the oscillator, thereby reducing susceptibility to injection pulling from neighboring oscillators and reducing the oscillator's effect on neighbors.
3Reliability
If multiple parallel inductors are used to maintain quality factor, then the quality factor is improved, but the device complexity increases
Solution Approach 1:
The multiple parallel inductors serve multiple functions simultaneously: they provide the necessary inductance for oscillation, maintain high quality factors for low jitter, and create magnetic flux cancellation to reduce injection pulling. This multi-functionality justifies the increased component count.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves the quality factor of the oscillator and reduces susceptibility to injection pulling, maintaining performance even at high data rates while minimizing the impact on neighboring oscillators.
Implementation Method 1
a capacitance element coupled in parallel with the transconductance circuitry
Implementation Method 2
a first half of the even number of inductors generates a first magnetic flux in a first direction, and a second half of the even number of inductors generates a second magnetic flux in a second direction opposite to the first direction, to mitigate injection pulling
Data Source
AI summary
Transceiver circuitry for coupling a functional circuit to a transmission medium includes a transmit path for coupling between the functional circuit and the transmission medium, a receive path for coupling between the transmission medium and the functional circuit, and clock generation circuitry coupled to at least one of the transmit path and the receive path. The clock generation circuitry includes an oscillator having transconductance circuitry, a capacitance element coupled in parallel with the transconductance circuitry, a plurality of inductors coupled in parallel with the transconductance circuitry and the capacitance element, and with each other, and a current source coupled to the plurality of inductors. The capacitance element may be variable. An even number of inductors are arranged so that half of the inductors generate magnetic flux in a first direction, and half of the inductors generate magnetic flux in a second direction opposite to the first direction.