Distributed Diode Mixer Circuit With Reactive Isolation Network
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Solution Overview
Problem
Existing double-balanced distributed mixers suffer from poor power handling capability, 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 employing multiple passive diode mixer cores with a reactive high impedance network between nodes, eliminating the need for bias circuits and termination resistors, and utilizing high impedance transmission lines or inductances for improved isolation and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active double balanced distributed mixers are used to achieve good isolation, then port-to-port isolation is improved, but noise performance deteriorates and dynamic range is limited
Solution Approach 1:
The mixer is divided into multiple passive diode mixer cores (first, second, and third mixer cores) distributed along transmission lines. Each core is independently driven by LO and RF signals with appropriate phase relationships, allowing the system to achieve double-balanced isolation characteristics through the combined output of multiple segmented units while maintaining passive operation for low noise.
Solution Approach 2:
Distributed reactive high impedance networks (comprising inductors and capacitors) are introduced as intermediary elements between the mixer cores and along the signal paths. These intermediary components create high impedance at specific frequencies to suppress unwanted signals and improve isolation between ports while allowing the passive diode cores to maintain low noise operation.
2Adaptability or versatility
If single-balanced distributed FET mixers are used for broadband operation, then bandwidth is improved, but port-to-port isolation deteriorates
Solution Approach 1:
The single-balanced structure is segmented into multiple passive diode mixer cores, each contributing to the overall mixing function. The distributed arrangement of these cores along transmission lines with specific electrical lengths enables broadband operation while the balanced configuration of each core maintains good port-to-port isolation.
Solution Approach 2:
Multiple mixer cores are merged in a distributed configuration where their outputs are combined through the reactive high impedance networks. This merging of multiple passive diode cores achieves the isolation characteristics of double-balanced mixers while maintaining the broadband capability through the distributed architecture.
3Reliability
If compensation inductors are added to diode ring mixers to improve linearity, then 3rd order harmonics are reduced, but the design becomes narrowband
Solution Approach 1:
Instead of using a single diode ring with compensation inductors, the mixer is segmented into multiple passive diode mixer cores distributed along transmission lines. This segmentation eliminates the need for frequency-specific compensation inductors while maintaining linearity through the distributed balanced configuration that naturally suppresses harmonics across a broad frequency range.
Solution Approach 2:
The fixed compensation inductors are replaced with a dynamic distributed network of reactive elements (inductors and capacitors) arranged along transmission lines. This dynamic configuration adapts to different frequencies through the distributed nature of the circuit, maintaining linearity performance across a broad reference frequency bandwidth rather than at a single resonant frequency.
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 broad bandwidth operation, with a mixing bandwidth ratio of up to 10:1, and eliminates the need for bias circuits and termination resistors, enhancing dynamic range and power efficiency.
Implementation Method 1
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
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.