Transformer Resonator Circuit for Second-Harmonic Noise Trapping
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Solution Overview
Problem
Existing radio frequency (RF) resonator circuits face challenges in frequency stability and phase noise performance due to the Groszkowski effect, which is exacerbated by higher order current components and flicker noise up-conversion, particularly at low supply voltages and high current consumptions.
Innovation Solution
A transformer-based resonator circuit is designed with different inductive coupling factors in differential and common mode excitations, where the common mode resonance frequency is twice the differential mode resonance frequency, providing a resistive path for second harmonics and mitigating the Groszkowski effect, thereby improving frequency stability and phase noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistors are added in series with the sources of the transistors to reduce higher order drain current harmonics, then the Groszkowski effect is mitigated and frequency stability is improved, but the radio frequency oscillator start-up margin is reduced
Solution Approach 1:
The resonator circuit is segmented into primary and secondary circuits with different resonance frequencies. The primary circuit operates at the oscillator frequency while the secondary circuit operates at twice the frequency, allowing separate optimization of frequency stability and start-up characteristics without mutual interference
Solution Approach 2:
The secondary resonator circuit acts as an intermediary element that provides a dedicated path for second harmonic currents. This mediator circuit reduces the Groszkowski effect by trapping harmonics before they can affect the primary oscillation circuit, thereby improving frequency stability without requiring series resistors that would reduce start-up margin
2Object-affected harmful factors
If resistors are added in series with the drain of the transistors to shift impulse sensitivity function and current waveform, then flicker noise up-conversion is reduced, but the phase noise performance in the 20 dB/decade region is degraded particularly at low supply voltages and high current consumptions
Solution Approach 1:
The patent converts the harmful second harmonic currents into a beneficial effect by providing them with a dedicated resistive path through the secondary resonator circuit. This converts what would be harmful harmonic distortion into a useful mechanism for reducing flicker noise up-conversion, while the differential mode resonance maintains phase noise performance
3Reliability
If a transformer-based resonator circuit with different inductive coupling factors in differential and common mode is used, then the common mode resonance frequency can be designed to be twice the differential mode resonance frequency providing a resistive path for second harmonics, but the device complexity increases
Solution Approach 1:
The transformer-based resonator circuit performs multiple functions simultaneously: it provides frequency selection, harmonic trapping, and noise filtering through its primary and secondary circuits. The differential and common mode excitations enable the same structure to serve both the primary oscillation frequency and the second harmonic frequency, reducing the need for separate circuits
Solution Approach 2:
The patent utilizes parameter changes in the transformer's inductive coupling factor between differential and common mode excitations. By designing the transformer with specific coupling characteristics, the resonance frequencies are naturally separated with the common mode frequency being twice the differential mode frequency, providing the desired harmonic trapping without additional complex circuitry
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
The transformer-based resonator circuit effectively reduces flicker noise up-conversion and enhances phase noise performance by trapping second harmonic currents in a resistive path, maintaining frequency stability and improving close-in phase noise characteristics.
Implementation Method 1
a transformer comprising a primary winding and a secondary winding, wherein the primary winding is inductively coupled with the secondary winding
Implementation Method 2
the primary capacitor and the primary winding forming a primary circuit, and a secondary capacitor being connected to the secondary winding, the secondary capacitor and the secondary winding forming a secondary circuit, wherein the resonator circuit has a common mode resonance frequency at an excitation of the primary circuit in a common mode, wherein the resonator circuit has a differential mode resonance frequency at an excitation of the primary circuit in a differential mode
Data Source
AI summary
The invention relates to a resonator circuit, the resonator circuit comprising a transformer comprising a primary winding and a secondary winding, wherein the primary winding is inductively coupled with the secondary winding, a primary capacitor being connected to the primary winding, the primary capacitor and the primary winding forming a primary circuit, and a secondary capacitor being connected to the secondary winding, the secondary capacitor and the secondary winding forming a secondary circuit, wherein the resonator circuit has a common mode resonance frequency at an excitation of the primary circuit in a common mode, wherein the resonator circuit has a differential mode resonance frequency at an excitation of the primary circuit in a differential mode, and wherein the common mode resonance frequency is different from the differential mode resonance frequency.