Variable-IF Receiver Tuning for Image and Intermodulation Rejection
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Solution Overview
Problem
Current wide tuning range receivers face challenges in achieving optimal performance due to issues like I/Q imbalance, LO leakage, and intermodulation rejection, particularly in superheterodyne architectures, which are costly and difficult to manufacture, and homodyne receivers lack the required dynamic range, making them unsuitable for modern wireless applications requiring frequency agility.
Innovation Solution
A wireless receiver with a programmable IF filter and dual wide-range tunable local oscillators, allowing for superior suppression of LO harmonics and intermodulation, integrated on a single chip with software-defined radio capabilities for flexible frequency tuning across a wide range, enabling compact design and easy manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a superheterodyne receiver structure is used, then image rejection and intermodulation rejection are improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent implements a variable intermediate frequency (IF) that dynamically changes based on the received signal frequency. This dynamic adjustment allows the receiver to maintain optimal image rejection and intermodulation performance across a wide frequency range without requiring complex fixed-frequency filtering for each band, thereby reducing manufacturing complexity while preserving reliability
Solution Approach 2:
The patent changes the IF parameter from a fixed value to a variable value that adapts to different frequency bands. By adjusting the IF according to the center frequency of the received signal, the system achieves consistent performance across wide tuning ranges without requiring multiple fixed-frequency filter designs, simplifying manufacturing
2Ease of manufacture
If a fixed intermediate frequency is used, then filter design becomes simpler, but the receiver cannot adapt to wide frequency ranges effectively
Solution Approach 1:
The patent employs a dynamic IF that automatically adjusts based on the detected signal frequency. This allows a single filter design to effectively cover multiple frequency ranges by adapting its operating point, combining the simplicity of fixed-frequency filter design with the versatility of wide frequency range coverage
Solution Approach 2:
The variable IF mechanism enables a single receiver design to universally handle multiple frequency bands and applications. The same hardware architecture can adapt to different frequency ranges by changing the IF parameter, eliminating the need for multiple specialized receiver designs
3Device complexity
If homodyne receiver structure is used, then architecture simplicity is improved, but dynamic range and performance deteriorate
Solution Approach 1:
The patent introduces an intermediate frequency stage as a mediator between the RF input and baseband output. This IF stage provides frequency translation that separates the mixing function from the detection function, enabling better dynamic range and performance while maintaining relative architectural simplicity through the use of a single conversion stage
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 provides superior image and intermodulation rejection, dynamic range, and linearity, allowing for flexible frequency selection and customization, addressing the limitations of existing receivers by enabling efficient handling of unwanted signals and reducing manufacturing complexity.
Implementation Method 1
mixed with a signal from a second local oscillator (LO) to produce an output signal having a second intermediate frequency (IF)
Data Source
Figure 1
AI summary
A wide tuning range receiver is provided that includes first and second mixers, and first and second local oscillators. The first mixer can mix an input signal with a signal from the first local oscillator and output a signal having a first intermediate frequency, the second mixer can mix the signal having the first intermediate frequency with a signal from the second local oscillator and output a signal having a second intermediate frequency, and, for each input signal frequency, a relationship between the first and second local oscillators can be fixed.