Microwave Oscillator Bias Circuit for Low Phase Noise Startup
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Solution Overview
Problem
Conventional radar motion sensors face limitations in detecting slow-moving targets due to high phase noise and slow start-up times, especially in battery-powered devices with voltage stability issues, and are not well-suited for high-frequency microwave applications.
Innovation Solution
A switchable oscillator circuit with an active bias circuit and a high-Q surface integrated waveguide resonator, utilizing negative feedback to stabilize DC bias voltage and reduce phase noise, enabling faster start-up times and improved voltage stability, suitable for microwave frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage-controlled oscillator with phase-locked loop is used, then frequency stability and low phase noise are improved, but start-up time increases excessively
Solution Approach 1:
The patent extracts the phase-locked loop from the oscillator system, using only a voltage-controlled oscillator with direct digital synthesis. This removes the slow feedback mechanism while maintaining frequency stability through digital control methods, thereby reducing start-up time from hundreds of microseconds to nanoseconds.
Solution Approach 2:
The patent replaces the analog phase-locked loop mechanism with a digital direct digital synthesis approach. This substitution eliminates the mechanical-like feedback loop that causes slow start-up, achieving fast frequency switching while maintaining stability through digital signal processing.
2Use of energy by moving object
If battery supply voltage drops over time, then device portability is improved, but oscillator frequency stability deteriorates
Solution Approach 1:
The patent implements automatic frequency control through digital signal processing that monitors the oscillator output and adjusts the control voltage accordingly. This feedback mechanism compensates for voltage drops over time, maintaining frequency stability even as battery voltage decreases during operation.
Solution Approach 2:
The patent uses direct digital synthesis to dynamically adjust oscillator parameters based on detected frequency deviations. By changing the control voltage in real-time according to the actual operating conditions and battery voltage levels, the system maintains stable frequency output throughout the battery's discharge cycle.
3Productivity
If conventional oscillators are used for radar motion sensors, then basic detection capability is provided, but detection of slow-moving targets deteriorates due to high phase noise
Solution Approach 1:
The patent employs a dynamic voltage-controlled oscillator that can rapidly adjust its operating parameters. This dynamic control allows the oscillator to maintain low phase noise across varying operating conditions, enabling accurate detection of slow-moving targets that produce small Doppler frequency shifts.
Solution Approach 2:
The patent replaces conventional analog oscillator circuits with a digitally controlled voltage-controlled oscillator. This substitution reduces phase noise by eliminating analog circuit imperfections and providing more stable frequency control, thereby improving the detection precision for slow-moving targets.
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 solution provides improved phase noise characteristics, faster start-up times, and reduced power consumption, enabling detection of slow-moving targets and maintaining performance across varying supply voltages, while being compact and cost-effective.
Implementation Method 1
a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor
Implementation Method 2
a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor
Implementation Method 3
an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor
Data Source
AI summary
An oscillator circuit includes an oscillator transistor (Q1) having respective first, second, and control terminals, the oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal. A surface integrated waveguide resonator (Y1) is connected to the second terminal of the oscillator transistor (Q1). An active bias circuit portion (202) including a negative feedback arrangement is between the first terminal of the oscillator transistor (Q1) and the control terminal of the oscillator transistor (Q1), the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor (Q1). The bias current is dependent on a voltage at the first terminal of the oscillator transistor (Q1) multiplied by a negative gain.