Distributed Diode Mixer Topology for Wideband Isolation and Low Noise
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Solution Overview
Problem
Existing double-balanced distributed mixers suffer from poor power handling, low linearity, and noise performance, while single-balanced distributed mixers have low port-to-port isolation, limiting their dynamic range and suitability for broadband applications.
Innovation Solution
A distributed diode mixer circuit using passive diode mixer cores with a reactive high impedance network between nodes, eliminating the need for bias circuits and providing improved isolation and linearity across a broad bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If active double-balanced distributed mixers are used, then port-to-port isolation is improved, but noise performance deteriorates
Solution Approach 1:
The patent replaces active electronic components (transistors, operational amplifiers) with passive diode-based switching elements. This substitution eliminates the need for bias circuits and active devices that generate noise, while maintaining the double-balanced topology's isolation benefits through passive reactive impedance networks.
Solution Approach 2:
The patent employs simple passive diodes instead of complex active devices. These passive components have no moving parts, require no power supply, and provide sufficient switching action for mixing operations, offering a robust and noise-free solution that trades component simplicity for performance.
2Adaptability or versatility
If single-balanced distributed FET mixers are used, then bandwidth is improved, but port-to-port isolation deteriorates
Solution Approach 1:
The patent employs asymmetric reactive impedance networks in the double-balanced topology to achieve both wide bandwidth and high isolation. The asymmetric configuration of inductors and capacitors allows independent optimization of bandwidth and isolation characteristics, overcoming the limitations of symmetric single-balanced designs.
Solution Approach 2:
The mixer is divided into multiple balanced pairs with separate reactive impedance networks for each pair. This segmentation allows each section to contribute to both bandwidth and isolation, with the combined effect providing superior overall performance compared to single-balanced topologies.
3Reliability
If active bias circuits are used in mixers, then mixing operation is improved, but power consumption increases
Solution Approach 1:
The passive diode-based mixer cores self-oscillate and self-mix without requiring external bias circuits or power supplies. The reactive impedance networks provide the necessary feedback and energy storage for sustained oscillation and mixing operation, making the system completely self-sufficient and eliminating all bias-related power consumption.
Solution Approach 2:
The mixer operates through periodic switching action of the passive diodes driven by the local oscillator signal. This periodic on-off switching provides the necessary non-linearity for mixing without requiring continuous DC bias, converting continuous power consumption into periodic energy transfer that occurs only during signal 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
The solution achieves high port-to-port isolation, low noise, and multi-octave bandwidth with reduced power requirements, exceeding previous mixer topologies in dynamic range and compactness, with isolation greater than 34 dB and input IP3 better than 18 dBm from 0.6 to 6 GHz.
Implementation Method 1
uses a compensation inductor between the differential reference (LO) nodes of a diode ring to resonate with the capacitive reactance of the diode ring at the reference (LO) frequency
Implementation Method 2
The local oscillator (LO) frequency or signal is also known as the reference frequency or signal and the higher, radio frequency (RF) frequency or signal is also known as the data frequency signal. Those frequency conversions are realized through the non-linear operations of the mixer cores embedded in the mixer circuits.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A distributed, diode mixer circuit includes a plurality of passive diode mixer cores including at least first and second passive diode mixer cores including doubly-balanced diodes in symmetrical balanced configuration forms, each mixer core having a pair of differential reference nodes driven by the reference signal and a pair of differential nodes driven by the data signal and a reactive impedance network including one or multiple reactive elements or transmission lines connected between the like nodes of each the first and second mixer cores.