Passive Mixer Receiver Circuit for FDD Intermodulation Reduction
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Solution Overview
Problem
In frequency division duplex (FDD) systems, the inability of duplexers to completely distinguish between transmission and reception signals leads to interference, causing intermodulation issues in the reception frequency domain, particularly when transmission signals pass through down-conversion mixers due to signal mismatches.
Innovation Solution
A receiver circuit incorporating a passive mixer circuit with a transformer and capacitors is used to adjust the center frequency of filtered RF signals, including a first and second coil with a capacitor grounded, to reduce intermodulation by employing a transformer with separate coils and passive mixers connected to each coil end, and a capacitor connected between the coils to manage differential signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a duplexer is used to distinguish between transmission and reception signals, then signal separation is improved, but complete distinction between transmission and reception signals cannot be achieved, causing interference in the reception frequency domain
Solution Approach 1:
The patent extracts and removes the transmission signal component from the reception signal path using a notch filter tuned to the transmission frequency. This extraction approach eliminates the harmful transmission signal interference that the duplexer cannot completely separate, thereby improving reception quality in FDD systems.
2Productivity
If a down-conversion mixer is used to process differential signals, then frequency conversion is achieved, but intermodulation occurs due to mismatch between differential signals
Solution Approach 1:
The patent introduces an intermediary balanced mixer circuit configuration with separate differential signal paths and matching networks. This intermediary structure acts as a mediator to ensure proper matching between differential signals during frequency conversion, preventing intermodulation distortion while maintaining conversion efficiency.
3Manufacturing precision
If intermodulation distortion is reduced in the mixer, then linearity is improved, but device complexity increases due to additional components like transformers and capacitors
Solution Approach 1:
The patent segments the mixer circuit into distinct functional blocks including a balanced mixer section, notch filter section, and separate differential signal paths. This segmentation allows each section to be optimized independently for linearity while managing overall circuit complexity through modular design and clear functional separation.
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 configuration enhances the linearity of the receiver circuit, reducing intermodulation distortion and improving signal-to-noise ratio (SNR) by minimizing second-order intermodulation products, thereby increasing the second-order intercept point (IIP2) performance.
Implementation Method 1
a transformer which includes a first coil and a second coil that is separate from the first coil
Data Source
AI summary
A receiver circuit is provided. The receiver circuit includes an antenna configured to receive a radio frequency (RF) signal; a filter configured to filter the RF signal received by the antenna; and a passive mixer circuit configured to adjust a center frequency of the filtered RF signal to a predetermined frequency. The passive mixer circuit includes: a transformer which includes a first coil and a second coil that is separate from the first coil; a first passive mixer which is directly connected to a first end of the second coil; and a second passive mixer which is directly connected to a second end of the second coil and is separate from the first passive mixer.