Cross-Coupled Compound VCO Core for Lower Millimeter-Wave Phase Noise
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Solution Overview
Problem
RF oscillators in millimeter-wave radar systems face limitations in phase noise performance due to saturation of active devices, which restricts the amplitude of oscillation signals, affecting resolution and accuracy.
Innovation Solution
An oscillator design incorporating a tank circuit and an oscillator core with cross-coupled compound transistors, where each compound transistor includes a bipolar transistor and a field effect transistor (FET) with the FET's source coupled to the bipolar transistor's base, preventing saturation and allowing higher oscillation amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If saturation of active devices is allowed in conventional RF oscillators, then device operation is simplified, but the amplitude of oscillation signal is limited, resulting in poor phase noise performance
Solution Approach 1:
The patent combines a bipolar transistor and a FET into a compound transistor structure where the FET's source is coupled to the bipolar transistor's base. This merging allows the compound transistor to operate without saturation while maintaining simplicity, thereby improving phase noise performance through higher oscillation amplitudes without proportionally increasing device complexity
Solution Approach 2:
The invention uses a composite transistor structure combining two different transistor types (bipolar and FET) to achieve properties that neither transistor type alone can provide. The compound transistor leverages the high transconductance of bipolar transistors and the high input impedance of FETs to achieve high amplitude oscillations without saturation, directly addressing the phase noise performance issue
2Measurement precision
If higher oscillation amplitudes are achieved through compound transistors, then phase noise performance improves, but the circuit structure becomes more complex
Solution Approach 1:
By merging the bipolar transistor and FET into a single compound transistor unit with the FET source coupled to the bipolar base, the circuit achieves higher oscillation amplitudes for improved radar resolution and accuracy while keeping the overall circuit structure relatively simple and manageable
Data Source
AI summary
In accordance with an embodiment, an oscillator includes a tank circuit and an oscillator core circuit having a plurality of cross-coupled compound transistors coupled to the tank circuit. Each of the plurality of compound transistors includes a bipolar transistor and a field effect transistor (FET) having a source coupled to a base of the bipolar transistor.