Frequency Synthesizer Reference Switching for Fast Startup Stability
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Solution Overview
Problem
Conventional frequency synthesizers face challenges in achieving stable frequency stability over the entire period of service immediately after power activation, particularly when using OCXO, which takes time to stabilize, and TCXO, which has poor long-term stability.
Innovation Solution
A frequency synthesizer design incorporating a reference signal generation circuit with a first oscillator (TCXO) for initial stabilization, a second oscillator (OCXO) for long-term stability, weight converters to adjust output weights, and a control unit to prioritize the TCXO initially and then OCXO, with an option for an external high-stability reference signal to ensure rapid stabilization and phase noise improvement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OCXO is used as reference signal, then long-term frequency stability is improved, but stabilization time after power activation increases
Solution Approach 1:
The reference signal generation is segmented into two phases: initial phase using TCXO for quick stabilization, and subsequent phase using OCXO for long-term stability. This temporal segmentation allows each oscillator to operate in its optimal performance window, resolving the contradiction between fast startup and long-term stability.
Solution Approach 2:
The system dynamically switches between TCXO and OCXO based on operational phase. A control unit monitors the startup state and automatically transitions from TCXO to OCXO, making the reference signal source adaptive to different operational requirements rather than static.
2Loss of time
If TCXO is used as reference signal, then stabilization time after power activation is reduced, but long-term frequency stability deteriorates
Solution Approach 1:
TCXO performs preliminary stabilization during the initial phase after power activation, providing adequate frequency stability for startup operations. This preliminary action allows the system to become operational quickly while the OCXO prepares to take over for long-term stability.
Solution Approach 2:
The control unit acts as an intermediary that manages the transition from TCXO to OCXO. It monitors the startup process and seamlessly transfers the reference signal function from TCXO to OCXO, ensuring continuous operation without manual intervention.
3Reliability
If multiple oscillators are used to improve frequency stability, then device complexity increases
Solution Approach 1:
The patent merges TCXO and OCXO into a unified reference signal generation system with automatic switching. Instead of requiring separate independent systems, the oscillators are combined under single control, sharing common circuitry and management logic, which reduces overall system complexity while maintaining dual-oscillator benefits.
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 enables quick stabilization of the frequency synthesizer during power activation and maintains stable frequency over a long period, while also allowing for the use of an external reference signal to enhance stability and prevent frequency fluctuations.
Implementation Method 1
a first oscillator (TCXO) having such characteristics that a frequency thereof stabilizes shortly after power activation
Implementation Method 2
a second oscillator (OCXO) having such characteristics that a frequency thereof is more unstable than that of the first oscillator immediately after the power activation and that the stability of the frequency thereof is higher than that of the first oscillator after the elapse of a fixed time
Data Source
AI summary
A frequency synthesizer in which a satisfactory frequency stability can be obtained over the entire long period of service immediately after power activation is disclosed. The reference signal generation circuit includes an OCXO, a TCXO, weight converters which regulate weights with respect to outputs, and an adder which adds up the outputs from the weight converters to output the added output as a reference signal. The CPU controls weight converters B and C so that the weight of the TCXO is set to 100% and the weight of the OCXO is set to 0% at the time of the power activation, so that the weight of the OCXO gradually rises, and so that the weight of the TCXO is set to 0% and the weight of the OCXO is set to 100% after preset time, whereby the frequency can quickly be stabilized after the power activation.