Nanosecond Pulse Generator Using Diode Opening Switches
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Solution Overview
Problem
Existing pulse generators for electroperturbation of biological cells are limited by their size, repetition rate, pulse duration, and jitter, with spark gap switched transmission lines being physically large and having low repetition rates, and MOSFET switched capacitors unable to generate pulses narrower than 15-20 ns.
Innovation Solution
A pulse generator circuit using a diode as an opening switch and a saturable core transformer to switch a tank circuit between two admittance values, allowing for the generation of pulses with lengths of no more than 3 nanoseconds and amplitudes of at least 1 kilovolt, and a frequency of at least 100 kHz, utilizing a MOSFET and diode array to achieve fast switching and high output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If spark gap switched transmission lines are used to generate ultra-short pulses, then pulse amplitude and speed are improved, but device size and physical footprint increase significantly
Solution Approach 1:
The patent replaces the mechanical spark gap switching system with an electronic switching system using MOSFETs and fast recovery diodes. This substitution eliminates the need for large transmission lines and physical spark gaps, achieving the same ultra-fast pulse generation (rise time < 100 ps) while dramatically reducing device size and enabling integration on compact circuit boards.
2Duration of action of moving object
If spark gap switched transmission lines are used, then ultra-short pulse generation is achieved, but repetition rate remains low
Solution Approach 1:
The electronic switching system using MOSFETs and fast recovery diodes enables repetition rates exceeding 10 MHz, compared to the low repetition rates of spark gap systems. The solid-state components can switch repeatedly at high frequencies without the delays associated with spark gap recharge and breakdown, allowing continuous generation of ultra-short pulses at high productivity.
3Volume of stationary object
If MOSFET switched capacitors are used to generate ultra-short pulses, then device size is reduced, but pulse width cannot be narrower than 15-20 ns
Solution Approach 1:
The patent changes the critical parameter from MOSFET switching speed to diode reverse recovery time. By selecting diodes with extremely fast reverse recovery times (trr < 100 ps), the system achieves pulse widths below 100 ps, overcoming the 15-20 ns limitation of conventional MOSFET switched capacitors while maintaining compact device size.
Solution Approach 2:
The fast recovery diode acts as an intermediary element that enables ultra-short pulse generation. The diode's rapid reverse recovery characteristic directly determines the pulse width, allowing the system to generate pulses narrower than 100 ps without being constrained by MOSFET switching limitations.
4Ease of operation
If conventional pulse generators are used, then basic pulse generation is achieved, but jitter in pulse timing increases
Solution Approach 1:
The solid-state electronic switching system eliminates the timing jitter inherent in spark gap and mechanical switching systems. The deterministic switching characteristics of MOSFETs and fast recovery diodes, controlled by precise electronic timing signals, achieve jitter below 100 ps, enabling high-precision timing applications.
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 enables the generation of extremely short, high-amplitude pulses with low jitter, effectively manipulating biological cells without causing permanent membrane openings, allowing for precise manipulation of intracellular structures like nuclei and mitochondria.
Implementation Method 1
a diode that is configured to operate as an opening switch and that saturates in less than 100 nanoseconds
Implementation Method 2
a saturable core transformer configured to operate as a switch that controls the opening of the diode
Data Source
AI summary
A pulse generator circuit may include a diode configured to operate as an opening switch, a tank circuit in series with the diode having an admittance that is switchable from a first value to a second value that is different from the first value, and a switching system configured to cause the tank circuit to switch between the first value and the second value. The diode may saturate in less than 100 nanoseconds. A saturable core transformer may operate as a switch that controls the opening of the diode. The pulse generator may generate a plurality of pulses, each having a length of no more than 3 nanoseconds and an amplitude of at least 1 kilovolt. Electrodes may be connected to the pulse generator to deliver the plurality of pulses to biological cells.