RF Receiver Harmonic Generator for Image Rejection Calibration
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Solution Overview
Problem
Existing RF receivers face challenges in effectively calibrating image rejection due to time-varying parameters such as temperature, which can affect the suppression of unwanted spectral content, known as 'image', in wireless communication systems.
Innovation Solution
Incorporating a harmonic generator within the RF receiver to generate a harmonic signal that replaces the input signal during a calibration mode, allowing for precise calibration of image rejection by isolating the antenna from the RF stage and processing only the image signal, thereby adjusting the image suppression circuitry to maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the receiver uses a mixer to downconvert RF signal to IF channel, then the spectral content is converted to a lower frequency suitable for processing, but unwanted spectral content (image) is also downconverted and cannot be easily suppressed
Solution Approach 1:
The patent applies preliminary action by performing image rejection calibration before normal receiver operation. A calibration source generates test signals at known frequencies, allowing the system to pre-adjust the image rejection circuitry (such as filters or mixers) to optimally suppress image frequencies. This preliminary calibration ensures that when actual RF signals are processed, the image suppression is already optimized, preventing the harmful effect of image interference from degrading measurement precision.
Solution Approach 2:
The patent implements feedback by using the calibration source to generate test signals and measuring the receiver's response to these signals. The system monitors the downconverted IF channel output and adjusts the image rejection parameters based on the measured performance. This closed-loop feedback mechanism continuously optimizes the image suppression, ensuring that the calibration adapts to variations in temperature, component aging, or other environmental factors that affect the receiver's frequency response.
2Speed
If the receiver processes signals in real-time without calibration, then processing speed is maintained, but image rejection performance degrades due to time-varying parameters such as temperature
Solution Approach 1:
The patent applies periodic action by implementing calibration at specific intervals during receiver operation. The calibration source is activated periodically to re-calibrate the image rejection circuitry, compensating for drift caused by temperature changes or other time-varying parameters. This periodic recalibration maintains reliable image rejection performance without requiring continuous calibration, thus preserving real-time signal processing speed while ensuring consistent reliability.
Solution Approach 2:
The patent performs calibration in advance during initialization or before critical measurement periods. By pre-calibrating the image rejection parameters using the calibration source, the system ensures optimal performance is established before processing actual signals. This preliminary action prevents performance degradation during operation and maintains both speed and reliability, as the system doesn't need to slow down for continuous calibration.
3Object-generated harmful factors
If the receiver includes image suppression circuitry, then unwanted spectral content is reduced, but the circuitry requires calibration to maintain optimal performance
Solution Approach 1:
The patent implements self-service by designing the calibration source as an integrated component of the receiver that automatically performs calibration without external intervention. The calibration source generates test signals and the system automatically measures and adjusts the image rejection parameters based on these signals. This self-calibrating mechanism reduces device complexity by eliminating the need for external calibration equipment or manual adjustment, while still achieving effective suppression of unwanted spectral content.
Solution Approach 2:
The patent applies universality by designing the calibration source to serve multiple functions: it generates test signals for calibration, provides reference frequencies for frequency synthesis, and can be used for other receiver characterization tasks. This multi-functional approach consolidates what would otherwise require separate dedicated components, reducing overall device complexity while maintaining the ability to effectively suppress unwanted spectral content through proper calibration.
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 enables efficient and adaptive calibration of image rejection, ensuring consistent signal quality across varying environmental conditions by recalibrating the receiver's image suppression circuitry, thereby improving the signal-to-noise ratio and reducing nonlinearities.
Implementation Method 1
the harmonic generator (132) generates a harmonic signal in response to operation of the oscillator (128)
Data Source
AI summary
An RF receiver includes an RF signal reception path to process an input signal for the receiver for a first mode of the receiver; an oscillator; and a harmonic generator. The harmonic generator generates a harmonic signal in response to operation of the oscillator to replace the input signal with the harmonic signal for a second mode of the receiver.