MINISTRY OF EDUCATION AND SCIENCE OF RUSSIA
SAINT PETERSBURG STATE ELECTROTECHNICAL UNIVERSITY
«LETI» N.A. V.I. ULYANOVA (LENINA)
Department of microwave electronics
REPORT
on individual homework №2
in the discipline «Microwave electronics»
Topic: Vacuum devices
7.75+0.5а=8.25 балл
Написано достойно, что усвоено – побеседуем на экзамене.
Student gr. 0207 _________________ Malikov B.I.
Teacher _________________ Ivanov V.A.
Saint Petersburg
2023
CONTENT
Task №1 …………………………………………………………………………... 3
Task №2 …………………………………………………………………………. 12
Task №3 …………………………………………………………………………. 17
Task №4 …………………………………………………………………………. 22
Task №5 …………………………………………………………………………. 32
Task №6 …………………………………………………………………………. 37
List of used literature ……………………………………………………………. 49
Task №1
From the presented list, select «your» device according to the rule
.
If your number exceeds the number 11, then
.
For this device, describe:
Construction;
Operating principle using: hydrodynamic approach and formula
,
quantum approach and individual radiation of charged particles.Estimate the size of the device if it operates at a frequency of f = 16 GHz. Power, gain, other parameters - choose yourself, according to the typical parameters of this type of devices, see Products — JSC «NPP «Istok» named after Shokina» (istokmw.ru).
Solving:
Nstudent = 6, accordingly, the device selected for the study is an M-type traveling-wave tube.
1. M-type traveling-wave tube construction:
Рicture 1 – M-type traveling-wave tube construction [1]
An electron gun consisting of a cathode and a control electrode creates a rectilinear electron flow. The electrons emitted by the incandescent cathode K fall into a constant electric field with a voltage of Ey, created by the voltage of the control electrode УЭ, and into a constant magnetic field with induction B, created by an external magnetic system not shown in the drawing. Under the action of these two fields, the electron flow bends the trajectory and moves towards the collector K' in the interaction space between the slowing system of the ЗС and the «cold» cathode of the ХК. As can be seen, a traveling-wave tube of the M type has a «cold» cathode in the place where the incandescent cathode is located in the magnetrons. Аn amplified signal is applied to the input of the slowing system of the ЗС, which excites a slow wave in the ЗС. The decelerating system is under a constant positive potential relative to this cathode. Therefore, the electron flow is affected by a transverse constant electric field of intensity E and a constant magnetic field with induction B. Moving in these crossed fields, the electron flow transfers part of the energy to an electromagnetic wave propagating from the input to the output, so amplification occurs. To eliminate the possibility of self - excitation, an absorber П is located in the decelerating system [1].
Let's consider separately each element of the M-type traveling-wave tube:
1. The electron gun creates an electron stream and introduces it into the interaction space.
2. The retarding system in the M-type TWT has a flat design necessary for interaction with the tape electron flow. It consists of a smooth electrode (cold cathode) and a periodic structure located parallel to it. As the latter, a comb structure and its modifications are often used. The electron flow interacts with the working spatial harmonic of this structure [2].
3. At the beginning and end of the decelerating system there are energy input and output devices, and in its middle of decelerating system – is a concentrated absorber. A concentrated absorber is necessary to eliminate the feedback that occurs due to imperfect matching of input and output devices.
4. The collector is designed to collect spent electrons.
5. Also, the M-type TWT has a magnetic system, usually consisting of permanent magnets and pole tips. To reduce the mass and dimensions of the magnetic system, the decelerating system is often folded into a ring [2].
The efficiency of an M—type traveling-wave tube with a large input signal can be 40-60%. At the same time, in real devices, the gain is 20 - 30 dB. In continuous operation, an M-type traveling-wave tube has an output power of up to several kilowatts, and for pulsed M-type traveling-wave tubes, it can be several megawatts. Currently, M-type traveling-wave tubes are mainly used as high-power output amplifiers [1][2].