THz Transmitter Return-Path Gap Coupler for Phase-Locked Power
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Solution Overview
Problem
Current THz signal generation technologies face challenges such as high cost, large form factor, and stringent operation conditions, with insufficient radiated power and limited DC to THz radiation efficiency, and lack of low-noise amplification and phase locking capabilities, hindering the development of portable and miniaturized THz imaging systems.
Innovation Solution
A 130 nm SiGe:C BiCMOS process-based THz transmitter with a return-path gap coupler design achieves high-power generation and efficient phase locking, utilizing a self-feeding oscillator structure for optimal voltage gain and harmonic isolation, and a phase-locked loop for synchronized radiating arrays, enhancing radiated power and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional THz sources (QCL, photoconductive emitters, vacuum electronics) are used, then high-power THz signal generation is achieved, but the system suffers from high cost, large form factor, and stringent operation conditions
Solution Approach 1:
The patent changes the operating parameters by using SiGe HBT transistors with optimized emitter length (Le=4.5×2 μm) and base resistance (RB=4 kΩ) to achieve fmax=280 GHz and BVceo=1.6 V, enabling high-power THz radiation without cryogenic cooling or complex vacuum systems
Solution Approach 2:
The patent replaces mechanical scanning systems and complex vacuum electronics with integrated circuit-based SiGe HBT oscillators that generate THz signals electronically, eliminating moving parts and stringent operational requirements
2Device complexity
If silicon transistor-based THz generators are used, then integration and miniaturization are improved, but radiated power and DC to THz radiation efficiency remain insufficient
Solution Approach 1:
The patent optimizes transistor parameters including emitter length (Le), base resistance (RB), and bias conditions to maximize the DC to THz radiation efficiency, achieving 0.54% efficiency at 320 GHz with 3.3 mW radiated power
Solution Approach 2:
The patent uses SiGe:C BiCMOS composite material structure combining silicon and germanium carbide to achieve superior speed (fmax=280 GHz) and breakdown voltage (BVceo=1.6 V) characteristics that enhance radiation efficiency
3Device complexity
If passive detection using nonlinear devices (Schottky diode, MOSFET) is used in receiver, then integration is improved, but sensitivity is limited
Solution Approach 1:
The patent introduces an on-chip low-noise amplifier as an intermediary stage between the passive detector and subsequent signal processing circuits, amplifying weak THz signals before further processing to enhance overall receiver sensitivity
4Area of stationary object
If mechanical scanning is used for imaging, then imaging coverage is improved, but system miniaturization is hindered and imaging time increases
Solution Approach 1:
The patent replaces mechanical scanning with electronic beam scanning using phased array technology, where the beam direction is controlled by electronic phase shifters without any moving parts, enabling miniaturization and faster imaging
5Power
If phased array with increased number of elements is used, then total radiated power is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The patent divides the THz radiating system into multiple independent oscillator elements that can be independently fabricated and then integrated into an array, simplifying the overall integration process while achieving high total radiated power through coherent combining
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 a record 3.3 mW total radiated power at 320 GHz with 0.54% DC to THz radiation efficiency and fully-integrated phase locking, enabling high-power THz generation and efficient energy use, while reducing system size and increasing sensitivity.
Implementation Method 1
two oscillators (20) operating at a fundamental frequency (f0)... Each oscillator (20) has a feedback path (22)... configured to provide differential coupling at f0 and harmonic extraction at a harmonic of f0 (the radiating frequency)
Implementation Method 2
A return-path gap coupler (30) is disposed in the feedback paths (22) of the oscillators (20). The coupler (30) is configured to be transparent to a signal at f0, and blocking to a signal at a harmonic of f0
Data Source
AI summary
A high-power transmitter with a fully-integrated phase Iocking capability is disclosed and characterized. Also provided herein is a THz radiator structure based on a return-path gap coupler, which enables the high-power generation of the disclosed transmitter, and a self-feeding oscillator suitable for use with the transmitter.