Transformer-Coupled Differential Oscillator for Harmonic Noise Filtering
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Solution Overview
Problem
Voltage controlled oscillators (VCOs) face challenges in millimeter wave applications due to phase noise, which introduces second and third-order harmonic spectral components, compromising output quality and requiring effective noise suppression.
Innovation Solution
The implementation of a transformer-coupled bandpass filter (BPF) with coupled capacitors and transformers, which filters out higher harmonics and reduces phase noise by 14 dB or more, enhancing the frequency response and noise suppression capabilities of VCOs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a voltage controlled oscillator operates in millimeter wave applications, then it can generate high-frequency signals, but phase noise introduces second and third-order harmonic spectral components that compromise output quality
Solution Approach 1:
The patent extracts and removes the harmful harmonic spectral components (second and third-order harmonics) from the oscillator output using a bandpass filter. The filter is configured to pass only the fundamental frequency while attenuating the harmonic components, thereby separating the useful signal from the harmful noise without affecting the high-frequency operation capability
Solution Approach 2:
The patent introduces a bandpass filter as an intermediary component between the oscillator and the output. This mediator selectively transmits the desired fundamental frequency while blocking the harmful harmonic spectral components, resolving the contradiction between maintaining high-frequency output and eliminating phase noise without requiring changes to the oscillator core
2Object-generated harmful factors
If a bandpass filter is added to reduce phase noise and filter harmonics, then output quality improves, but device complexity increases
Solution Approach 1:
The patent optimizes the bandpass filter parameters (center frequency, bandwidth, Q-factor) to specifically target the millimeter wave operating range and the prominent second and third harmonics. By carefully selecting these parameters, the filter achieves effective noise suppression with a relatively simple structure, avoiding the need for complex multi-stage filtering while maintaining output quality
Solution Approach 2:
The bandpass filter is designed to simultaneously perform multiple functions: filtering second-order harmonics, filtering third-order harmonics, and providing phase noise suppression. This multi-functionality is achieved through a single filter stage with appropriately selected parameters, reducing the overall circuit complexity compared to using separate filters for each function
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 significantly reduces phase noise, improving the output quality of VCOs, particularly in high-frequency applications, by filtering out unwanted harmonics and maintaining signal power without increasing noise power.
Implementation Method 1
a transformer including a first winding in a metal layer of an IC, the first winding including a first conductive structure coupled to the first output node, a second conductive structure coupled to a second voltage node, and a third conductive structure including a first extending portion connected to the first conductive structure and a second extending portion connected to the second conductive structure
Implementation Method 2
The pair of coupled capacitive devices Cc1 and Cc2 are configured so that the transformer-coupled BPF includes a bandpass range outside the frequency range of the phase noise contributed by the 2nd and 3rd harmonics
Data Source
AI summary
A differential oscillator includes a differential circuit and a transformer-coupled band-pass filter (BPF) coupled between first and second output nodes. The BPF includes a coupling device coupled between the output nodes and a transformer including first and second windings in a metal layer of an IC. The first winding includes first and second conductive structures coupled to the first output node and a voltage node, respectively, and a third conductive structure including first and second extending portions connected to the first and second conductive structures, respectively. The second winding includes a fourth conductive structure including a third extending portion coupled to the voltage node and a fourth extending portion coupled to the second output node. The third extending portion is between the second conductive structure and the first extending portion, and the fourth extending portion is between the first conductive structure and the second extending portion.