Switched-Core FET Ring Mixer for Wideband LO Linearity
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Solution Overview
Problem
Current passive mixer circuits in RF systems have limited linear ranges, leading to unacceptable 1 dB compression points and third intercept points, especially for high-amplitude RF and IF signals, resulting in issues like LO signal loss, parasitic loading, narrow-banding, and non-linearities.
Innovation Solution
A multi-LO band switched-core frequency mixer is introduced, featuring a single FET ring with multiple mixer cores and LO paths, which connects to a common RF and IF port, utilizing separate LO transformers and LO select logic to operate across multiple frequency bands, reducing setbacks like LO signal loss and non-linearities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-core mixer is used, then the device complexity is low, but the LO operating frequency band is limited and linearity is poor
Solution Approach 1:
The mixer is divided into multiple independent mixer cores (first mixer core, second mixer core, etc.), each optimized for specific frequency bands. Each core has its own LO transformer and switching network, allowing independent operation and selection based on the desired frequency band, thereby extending the overall LO operating frequency band while maintaining manageable complexity through modular design
Solution Approach 2:
The multiple mixer cores share common RF and IF ports, and are controlled by a unified switching mechanism based on LO select logic. This allows a single mixer device to perform multiple frequency conversion functions across different frequency bands, achieving multi-functionality without requiring separate mixer circuits for each band
2Power
If high-amplitude RF and IF signals are used, then the signal processing capability is improved, but the 1 dB compression point and third intercept point become unacceptable due to limited linear range
Solution Approach 1:
Each mixer core is designed with specific quality characteristics optimized for its designated frequency band and signal amplitude range. The switching network selectively connects the appropriate mixer core based on the input signal characteristics, ensuring that high-amplitude signals are always processed by a core operating within its optimal linear range, thereby maintaining both high power handling capability and acceptable linearity
3Device complexity
If passive mixer circuits are used, then the circuit simplicity is maintained, but LO signal loss and parasitic loading occur
Solution Approach 1:
The mixer employs dynamic switching between multiple mixer cores based on the LO frequency band and signal conditions. This dynamic selection allows the system to switch to a mixer core with optimal characteristics for the current operating conditions, minimizing LO signal loss and parasitic loading by avoiding operation in suboptimal frequency ranges where such losses are exacerbated
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 multi-LO band switched-core frequency mixer extends the LO operating frequency band while maintaining high linearity, overcoming narrow frequency-band limitations of single-core mixers and ensuring optimal performance across multiple frequency bands.
Implementation Method 1
a single field-effect transistor (FET) ring having a first mixer core and a second mixer core
Implementation Method 2
a first local oscillator (LO) transformer connected to the single FET ring and a second LO transformer connected to the single FET ring
Implementation Method 3
Frequency mixers include electrical circuits configured to create new frequencies from two signals applied to the frequency mixer. For example, frequency mixers may be utilized to shift signals from one frequency range to another (e.g., heterodyning the signals)
Data Source
AI summary
A frequency mixer is disclosed. In an implementation, the multi-LO band switched-core includes a single field-effect transistor (FET) ring having a first mixer core and a second mixer core. The first mixer core and the second mixer core configured to connect to a radio frequency (RF) port and an intermediate frequency (IF) port. The frequency mixer also includes a first local oscillator (LO) transformer and a second LO transformer. The first LO transformer is configured to furnish a first LO signal occurring in a first limited range of frequencies to the first mixer core, and the second LO transformer is configured to furnish a second LO signal occurring in a second limited range of frequencies to the second mixer core.