Injection-Locked Tank Oscillator for Nanosecond Frequency Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional phase-locked loops (PLLs) have significant locking times (microseconds) and are unable to provide 'locked' signals with response times in the nanosecond and/or sub-nanosecond range, limiting their applicability in generating ultra-wide band transmit pulses or providing clocks for analog-to-digital converters.
Innovation Solution
An electronic oscillator circuit with a tank circuit, first and second current controllers, and cross-coupled pair circuits to inject current through the tank circuit, allowing for fast response times and low-power operation, using injection locking to achieve oscillations at predetermined frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase-locked loops are used to generate and lock periodic signals, then signal stability is achieved, but locking time becomes too long (microseconds instead of nanoseconds)
Solution Approach 1:
The patent extracts the frequency control function from the traditional PLL feedback loop and implements it through direct current injection into the tank circuit. The injection current source applies a current at the desired frequency directly to the tank circuit, forcing it to oscillate at that frequency without requiring the lengthy phase alignment process of conventional PLLs. This separates the frequency determination function from the amplitude stabilization function, achieving fast frequency locking while maintaining signal stability.
Solution Approach 2:
The patent applies preliminary action by pre-generating the injection current at the desired frequency before it is needed by the tank circuit. The injection current source is configured to provide current at the target frequency in advance, so when applied to the tank circuit, the oscillations immediately lock to the correct frequency without requiring real-time phase adjustment. This preliminary preparation of the injection signal eliminates the iterative locking process of traditional PLLs.
2Device complexity
If conventional oscillators are used, then circuit simplicity is maintained, but response time is too slow for nanosecond-range applications
Solution Approach 1:
The patent replaces the mechanical feedback-based frequency control mechanism of traditional oscillators with an electrical direct-injection approach. Instead of using complex feedback loops with phase detectors and variable frequency dividers, the invention uses a simple current injection mechanism where an injection current source directly applies current at the desired frequency to the tank circuit. This substitution of the control mechanism achieves nanosecond-range response times while keeping the overall circuit relatively simple.
3Speed
If high-power signals are used to achieve fast locking, then response time improves, but power consumption increases
Solution Approach 1:
The patent applies partial action by injecting current only for the brief duration needed to establish oscillations at the correct frequency, rather than continuously driving the oscillator at high power. The injection current source provides current pulses synchronized with the tank circuit's oscillation cycle, applying just enough energy to force the frequency lock and then maintaining it with minimal power. This partial injection approach achieves fast locking without the continuous high-power consumption that would be required by alternative methods.
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 oscillator achieves fast response rates (nanosecond range) and low-power operation, enabling generation of ultra-wide band transmit pulses and providing clocks for analog-to-digital converters with improved spectral compliance.
Implementation Method 1
the tank circuit oscillates at its natural resonant frequency (determined by the sizes of the inductor and the capacitor)
Implementation Method 2
when a current is injected at an injection frequency close to (or having an Nth harmonic component close to) the natural resonant frequency of the tank circuit, the frequency of the oscillating signal in the tank circuit is 'pulled' to the injection frequency
Data Source
AI summary
An electronic oscillator circuit comprising: a tank circuit comprising an inductor and a capacitor, wherein the inductor and the capacitor each have a first terminal connected to a first side of the tank circuit and a second terminal connected to a second side of the tank circuit; a first current controller; and a second current controller; wherein the first current controller is connected to the first side of the tank circuit; wherein the second current controller is connected to the second side of the tank circuit; wherein the first current controller is arranged such that it can act as a current source for the tank circuit; wherein the second current controller is arranged such that it can act as a current sink for the tank circuit; wherein the first current controller and the second current controller are configured such that when the first current controller and the second current controller are in a first state, an injected current flows from the first current controller to the second current controller through the tank circuit; and when the first current controller and the second current controller are in a second state, no current is injected into the tank circuit. The injection of current in this way allows energy to be injected to the tank circuit, which forces oscillations in the tank circuit at a predetermined frequency different to the natural resonant frequency of the tank circuit.