Variable Frequency Oscillator Mixing for Image Signal Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Superheterodyne receiver circuits face challenges in effectively suppressing image frequency signals, particularly at microwave frequencies, due to component imbalances and phase noise issues with traditional variable frequency oscillators, which can lead to insufficient signal rejection and performance degradation.
Innovation Solution
A variable frequency oscillator circuit utilizing a fixed frequency oscillator, frequency dividers, and mixers to generate a desired frequency signal, with calibration and digital processing to suppress unwanted signals, including image frequencies, through adjustments in mixer operations and the use of a MIMO integrated circuit for enhanced signal rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional variable frequency oscillators are used in superheterodyne receiver circuits, then the circuit can operate at microwave frequencies, but image frequency signals cannot be sufficiently suppressed due to component imbalances and phase noise
Solution Approach 1:
The oscillator signal generation is segmented into multiple frequency components (first frequency f1 and second frequency f2) that are generated separately and then combined. This segmentation allows independent optimization of each frequency component to minimize image frequency interference while maintaining the desired output frequency.
Solution Approach 2:
Different frequency components are assigned different quality characteristics. The first frequency f1 is optimized for low phase noise, while the second frequency f2 is optimized for image frequency suppression. This local quality differentiation resolves the contradiction by allowing each component to excel at its specific function.
2Object-affected harmful factors
If image-reject mixers and quadrature components are used to suppress image frequencies, then some suppression is achieved, but performance degrades due to imbalances within these components
Solution Approach 1:
The harmful image frequency components are extracted and identified separately from the desired signal path. By using multiple frequency components where one component (f2) is specifically designed to carry image frequency information, the system can isolate and suppress these unwanted signals without affecting the main signal path.
Solution Approach 2:
The oscillator uses asymmetric frequency component generation where f1 and f2 have different characteristics and roles. This asymmetry allows the system to optimize each component for its specific purpose, avoiding the symmetry-based limitations of traditional balanced mixers and quadrature components.
3Speed
If frequency mixing is performed to convert received signals to intermediate frequency, then signal conversion is achieved, but unwanted signals at image frequencies are also converted and cannot be separated
Solution Approach 1:
The system performs preliminary frequency separation by generating the oscillator output as multiple distinct frequency components before the mixing process. By pre-organizing the frequency spectrum into designated channels (f1 for desired signal, f2 for image frequencies), the subsequent mixing operation can efficiently convert signals while maintaining separability of image frequencies through digital processing.
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 approach provides improved suppression of unwanted signals, achieving higher signal rejection ratios and reducing phase noise, thereby enhancing the performance of superheterodyne receiver circuits, especially at microwave frequencies.
Implementation Method 1
a fixed frequency oscillator
Implementation Method 2
one or more frequency dividers, arranged to receive the output of the fixed frequency oscillator and generate a signal with a divided frequency
Implementation Method 3
one or more mixers, arranged to mix the outputs of the one or more frequency dividers to generate the oscillating signal of the desired frequency
Data Source
AI summary
A variable frequency oscillator circuit for generating an oscillating signal of a desired frequency, comprising a fixed frequency oscillator; one or more frequency dividers, arranged to receive the output of the fixed frequency oscillator and generate a signal with a divided frequency; and one or mixers, arranged to mix the outputs of the one or more frequency dividers to generate the oscillating signal of the desired frequency. The variable frequency oscillator circuit is arranged to modify the operation of the one or more mixers to suppress any unwanted signals in the generated oscillating signal.