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Compression of frequency modulated pulses using a high order helically corrugated waveguide

使用高阶螺旋波纹波导压缩调频脉冲

基本信息

批准号：
EP/E058868/1
负责人：
Adrian Cross
金额：
$ 66.05万
依托单位：
University of Strathclyde
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE058868%2F1
关键词：
Compression frequency modulated pulses using

项目摘要

A waveguide can be used to compress frequency-modulated pulses. Consider compression of a quasi-monochromatic pulse with frequency monatonically varying in time from one frequency (w1) to another frequency (w2). This pulse is then propagated down a dispersive medium in which the group velocity of the wave is a function of frequency only. If the wave group velocity in the dispersive medium is an increasing function of frequency, vgr(w2) > vgr(w1), then the tail of the pulse will overtake its leading edge, resulting in pulse shortening and a corresponding growth in the amplitude if the losses are sufficiently low. Compression experiments were first carried out using a smooth metal waveguide and were found attractive because of its capability of handling high power. However a serious drawback of a smooth waveguide as a powerful compressor is its operation very close to the cut-off. In optimum cases, the frequency at the beginning of an input pulse should be only 0.5-1% above the cut-off frequency. If one uses such a compressor at the output of a powerful amplifier, then the low-frequency part of the amplification band will be reflected back to the amplifier resulting in its possible parasitic self-oscillation (RF isolation using unidirectional elements is impossible at very high power). We propose to design and construct a waveguide with a helical corrugation of its inner surface as the frequency dispersive medium, to couple a pair of circularly polarized partial modes of the smooth waveguide having significantly different group velocities. Pulse compression using a 3-fold helically corrugated waveguide using an optimised frequency swept pulse generated by a state-of-the-art programmable Arbitary waveform generator and microwave sweeper will be studied, with the predictions of theory compared to experiment. We propose also to design, build and investigate the use of a larger diameter 5-fold helically corrugated waveguide as the frequency dispersive medium to compress MW frequency swept pulses generated by a gyrotron travelling wave amplifier. The advantage of using a 5-fold helical structure as compared to a 3-fold helical waveguide is that it requires the use of a higher order mode and hence the diameter of the compressor is increased which means that higher peak power radiation can be propagated down the compressor before the electric fields becomes excessively large resulting in RF breakdown. A favourable wave dispersion can be synthesized for the higher-order modes (near cut-off TE2,2 mode which couples to a counter-rotating TE3,1 mode) excited in a 5-fold helical compressor resulting in an increase of the helical waveguide diameter by a factor of 1.5-2 (without significant overlapping of the coupling bands) and correspondingly in an enhancement of its RF breakdown strength. Unique high power (multi-MW), short pulse (~1ns) radiation required in a number of applications will be generated.

波导可用于压缩调频脉冲。考虑压缩准单色脉冲，其频率随时间单调变化，从一个频率（w1）到另一个频率（w2）。然后，该脉冲沿着色散介质传播，在色散介质中，波的群速度仅是频率的函数。如果色散介质中的波群速度是频率的递增函数，vgr（w2）> vgr（w1），则脉冲的尾部将超过其前沿，导致脉冲缩短，并且如果损耗足够低，则幅度相应地增长。压缩实验首先使用光滑的金属波导进行，并发现有吸引力的，因为它的处理高功率的能力。然而，光滑波导作为强大的压缩器的严重缺点是其操作非常接近截止。在最佳情况下，输入脉冲开始时的频率应仅比截止频率高0.5-1%。如果在大功率放大器的输出端使用这种压缩器，则放大频带的低频部分将被反射回放大器，导致其可能的寄生自振荡（在非常高的功率下，使用单向元件的RF隔离是不可能的）。我们提出设计和构造一种内表面为螺旋形的波导作为频散介质，耦合一对具有显著不同群速度的光滑波导的圆偏振部分模。脉冲压缩使用的3倍螺旋波纹波导使用一个最先进的可编程任意波形发生器和微波扫描器产生的优化频率扫描脉冲将进行研究，与理论预测相比，实验。我们还建议设计，建造和研究使用一个更大的直径5倍螺旋波纹波导作为频率色散介质压缩微波频率扫描产生的回旋行波放大器的脉冲。与3重螺旋波导相比，使用5重螺旋结构的优点在于，它需要使用更高阶的模式，因此压缩器的直径增加，这意味着在电场变得过大而导致RF击穿之前，更高的峰值功率辐射可以沿压缩器向下传播。对于在5倍螺旋压缩器中激发的高阶模式（耦合到反向旋转的TE 3，1模式的近截止TE 2，2模式），可以合成有利的波色散，导致螺旋波导直径增加1.5-2倍（没有耦合带的显著重叠），并且相应地增强其RF击穿强度。独特的高功率（多兆瓦），短脉冲（~ 1 ns）辐射所需的一些应用将产生。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Numerical simulations of a co-harmonic gyrotron

共谐波回旋管的数值模拟

DOI：
10.1088/0022-3727/45/6/065105
发表时间：
2012
期刊：
Applied Physics
影响因子：
0
作者：
Constable D
通讯作者：
Constable D

A co-harmonic gyro-oscillator with a novel interaction cavity

具有新型相互作用腔的共谐波陀螺振荡器

DOI：
10.1109/ivelec.2009.5193500
发表时间：
2009
期刊：
影响因子：
0
作者：
Constable D
通讯作者：
Constable D

Free-electron maser based on two-dimensional distributed feedback

基于二维分布式反馈的自由电子脉泽

DOI：
发表时间：
期刊：
影响因子：
0
作者：
Alan Phelps (Author)
通讯作者：
Alan Phelps (Author)

Generation of 3 GW microwave pulses in X-band from a combination of a relativistic backward-wave oscillator and a helical-waveguide compressor

DOI：
10.1063/1.3505825
发表时间：
2010-11
期刊：
Physics of Plasmas
影响因子：
2.2
作者：
V. Bratman;G. Denisov;N. G. Kolganov;S. Mishakin;S. Samsonov;A. Cross;Wenlong He;Liang Zhang;M. McStravick;C. Whyte;A. Young;K. Ronald;C. Robertson;A. Phelps
通讯作者：
V. Bratman;G. Denisov;N. G. Kolganov;S. Mishakin;S. Samsonov;A. Cross;Wenlong He;Liang Zhang;M. McStravick;C. Whyte;A. Young;K. Ronald;C. Robertson;A. Phelps

A novel cylindrical TE(2,1) mode converter.