Crossed-Field Amplifier Anode Cathode Geometry for Spurious Emission Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Crossed-field amplifiers produce spurious emissions due to fluctuations in electron density caused by spent electrons not having enough time to diffuse into a uniform stream before reentering the input section, interfering with communication systems like radars.
Innovation Solution
The geometry of the cathode and anode is modified to reduce electron velocity and increase diffusion, such as by increasing the anode-to-cathode spacing and altering the cathode radius, which disperses electrons and reduces the peak amplitude of spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the drift section length is short, then the device length is reduced, but spurious emissions increase due to insufficient electron diffusion time
Solution Approach 1:
The patent applies local quality by creating a non-uniform electric field in the drift section through specific electrode configurations. The electric field strength varies spatially, with stronger fields near the cathode and weaker fields further away, allowing localized control of electron diffusion rates to reduce spurious emissions without requiring a long drift section.
Solution Approach 2:
The patent changes physical parameters including electric field strength, magnetic field strength, and their ratios to optimize electron diffusion. By adjusting these parameters, the patent achieves sufficient electron diffusion in a shorter drift section, reducing spurious emissions while maintaining compact device dimensions.
2Speed
If the electric field strength is increased, then electron acceleration and gain are improved, but spurious emissions increase due to reduced diffusion time
Solution Approach 1:
The patent employs dynamic control of the electric field through time-varying voltages applied to the electrodes. The electric field strength is modulated to accelerate electrons during the interaction phase for gain, then reduced during the drift phase to allow diffusion, thereby reducing spurious emissions while maintaining electron velocity when needed.
Solution Approach 2:
The patent uses periodic modulation of the electric and magnetic fields to control electron behavior in cycles. During interaction cycles, fields are configured for electron acceleration and energy transfer; during drift cycles, fields are adjusted to promote diffusion, reducing spurious emissions while maintaining overall electron velocity and gain.
3Power
If the magnetic field strength is increased, then electron rotation and energy transfer are improved, but device complexity and power consumption increase
Solution Approach 1:
The patent designs the magnetic field system to serve multiple functions: generating the crossed field for electron rotation, controlling electron confinement in the interaction region, and influencing electron diffusion in the drift section. This multi-functionality reduces the need for separate control systems, thereby reducing device complexity while maintaining output power.
Solution Approach 2:
The patent combines the magnetic field generation with the structural components of the device, integrating magnet elements into the housing or support structures. This merging of functions reduces the number of separate components and simplifies the overall device architecture while maintaining the required magnetic field strength for electron rotation and energy transfer.
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 modifications significantly reduce spurious emissions, with peak amplitudes decreased by about 6.5 dB, while maintaining adequate output power, although there is a minor efficiency penalty due to electron loss.
Implementation Method 1
The cathode of the CFA emits electrons as a result of primary (thermionic) or secondary emission, or both
Implementation Method 2
Under the influence of the crossed electric and magnetic fields, the electrons emitted from the cathode rotate around the cathode and form a thin region of high electron density near the cathode surface, known as a hub
Implementation Method 3
The anode can be configured to emit electrons to the cathode
Data Source
AI summary
Various crossed-field amplifiers (CFAs) are disclosed herein. In one embodiment, the geometry of the cathode and/or the anode reduces the velocity of the electrons as they travel near the anode drift block to increase the distribution of the electrons in the drift gap. In another embodiment, an abrupt geometric change to the cathode at the beginning or the end of the anode drift block can disperse the electrons, thereby increasing the rate of mixing and diffusion. By increasing the distribution of the electrons, the peak amplitude of spurious emissions produced by a CFA can be reduced.