Selectable Local Oscillator Using Sideband Mixing for Fast Frequency Switching
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Solution Overview
Problem
Conventional frequency synthesizers face limitations in frequency bandwidth and speed, making them inadequate for advanced radar and communication systems that require rapid frequency switching and a wide range of frequencies, especially when system requirements change, leading to delays due to the need for custom crystal oscillators.
Innovation Solution
A selectable local oscillator design that generates a selectable frequency signal by mixing and selecting sidebands from multiple input frequency ranges, allowing for a wide range of output frequencies with reduced spurious components and fast switching, eliminating the need for multiple crystal oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional frequency synthesizers use crystal oscillators to provide stable oscillation frequencies, then noise and spurious components are reduced, but frequency bandwidth is limited and switching speed is slow
Solution Approach 1:
The frequency range is divided into multiple discrete frequency ranges, with each range handled by a dedicated signal generator. This segmentation allows each generator to operate within its optimized range while the system as a whole achieves wide frequency coverage and fast switching between ranges.
Solution Approach 2:
The system uses multiple signal generators that can each serve multiple frequency ranges through mixing operations. The generators are designed to be multi-functional, capable of producing signals that can be combined in different ways to cover the entire desired frequency spectrum.
2Reliability
If crystal oscillators are manufactured to meet new frequency requirements, then system performance is maintained, but deployment time increases due to 6-9 month production cycles
Solution Approach 1:
Instead of manufacturing new crystal oscillators with different frequency characteristics, the system changes operational parameters by selecting different combinations of existing signal generators and mixing configurations. This allows rapid adaptation to new frequency requirements without physical manufacturing delays.
Solution Approach 2:
The system uses software-defined frequency selection that copies the stable oscillation characteristics of crystal generators across multiple frequency ranges through mixing, rather than requiring physical copies of crystal oscillators for each frequency.
3Adaptability or versatility
If multiple crystal oscillators are used to cover different frequencies, then frequency switching is enabled, but system complexity and operational complexity increase
Solution Approach 1:
Multiple signal generation functions are merged into a unified system architecture where discrete frequency generators are combined with mixing stages and frequency selection logic. This integration reduces overall system complexity compared to managing multiple independent crystal oscillator systems.
4Reliability
If conventional synthesizers use phase lock loops for frequency generation, then frequency stability is achieved, but switching speed between frequencies is limited
Solution Approach 1:
Multiple signal generators are prepared in advance, each capable of immediately providing signals for its designated frequency range. When frequency switching is required, the system simply selects the pre-prepared signal from the appropriate generator and mixing configuration, eliminating the settling time required by phase lock loops.
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
This design provides a flexible and efficient method to generate a wide range of frequencies quickly, reducing deployment delays and operational complexity by using a single oscillator configuration, while minimizing spurious signals and maintaining low noise levels.
Implementation Method 1
mixing the first selectable frequency signal with the second selectable frequency signal to provide a first mixed product signal having an upper sideband and a lower sideband
Data Source
AI summary
A selectable local oscillator provides an output frequency signal having a selectable frequency within a desired output frequency range. The selectable local oscillator comprises first, second and third signal generators configured to provide first, second and third frequency signals having frequencies in first, second and third input frequency ranges. A first mixer provides a first mixed product signal having an upper sideband and a lower sideband. A frequency selector selects one of the upper and lower sidebands of the first mixed product signal. A second mixer provides a second mixed product signal having an upper sideband and a lower sideband. An output stage selects at least one of the upper and lower sidebands of the second mixed product signal as the output frequency signal.