Transformer-Coupled Frequency Doubler With Frequency Tracking Loop
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Solution Overview
Problem
Conventional oscillators and phase-locked loops (PLLs) face challenges in achieving low phase noise at high frequencies, such as 28 GHz, which is essential for high-speed data transmission like 224 Gbps PAM-4 transmitters, due to reduced capacitor quality factor and increased power consumption in existing low noise oscillator designs.
Innovation Solution
The implementation of a frequency doubler (tripler, or quadrupler) using a current re-use coupled oscillator technique, where two oscillators are coupled via a transformer, with one oscillator running at the target frequency and the other at half the frequency, enhancing phase noise performance without increasing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional oscillators are used at 28 GHz, then high frequency operation is achieved, but phase noise exceeds the required specification
Solution Approach 1:
The oscillator is divided into two coupled oscillating circuits operating at different frequencies (first oscillator at 28 GHz, second oscillator at 14 GHz). The lower frequency oscillator provides a stable reference that couples to the higher frequency oscillator, enabling the system to achieve high frequency operation while maintaining low phase noise through the quality factor advantage of the lower frequency capacitor.
2Reliability
If low noise oscillator designs are implemented, then phase noise performance improves, but power consumption increases
Solution Approach 1:
Two oscillating circuits are coupled together through a transformer to share energy and improve efficiency. The first oscillator (28 GHz) and second oscillator (14 GHz) are merged through magnetic coupling, allowing the system to achieve low phase noise performance while the current reuse architecture reduces overall power consumption compared to conventional single-oscillator low-noise designs.
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 approach achieves up to 4.5 dB better phase noise performance and enables high-speed data transmission rates of 224 Gbps and beyond by improving capacitor quality factor and reducing power consumption.
Implementation Method 1
a transformer coupled to the first oscillator; and a second oscillator coupled to the transformer
Data Source
AI summary
A frequency doubler (tripler, or quadrupler) employs current re-use coupled oscillator technique to enhance phase noise without increasing current consumption. Frequency doubler uses coupling between two oscillators running at different frequencies; a first oscillator is running at the target frequency and a second oscillator is running at half the frequency. The coupling between the two oscillators is via a transformer having a primary transformer coil and a secondary transformer coil. The first oscillator comprises a differential inductor, coarse/fine tuning capacitor arrays, and an n-type trans-conductor (GM). A virtual ground node of the n-type GM is coupled to one side of the primary transformer coil and the other side of the primary coil is coupled to the center tap of the secondary coil. The second oscillator comprises the secondary coil, coarse/fine tuning capacitor arrays, n-type GM, frequency tracking loop (FTL) and 2nd-harmonic LC filter network.