Hello friends, welcome to Engineering Funda family. In this video, I'll explain two-cavity clistron amplifier with great clarity. Before I start with my explanation, let me tell you how many points that I'm going to cover in this video.
Here, I'll cover basics, working, structure, Applegate diagram, and applications of two-cavity clistron amplifier. So let us begin this session with first agenda, that is basics of two cavity klystron amplifier. See two cavity klystron is amplifier which we use it to amplify RF signal.
So one can amplify RF or microwave signal using two cavity klystron amplifier. That amplification is done using principle of velocity modulation. Here we will be modulating velocity of electrons and by having modulation of velocity of electrons, we will be generating electron bunch.
Based on electron bunch, we can amplify signal. That I will explain in Applegate diagram even. Right now consider amplification of RF signal is done based on the principle of velocity modulation.
In the structure of two cavity clistron amplifier, we have two cavities. First cavity is buncher cavity and second cavity is Catcher cavity. Buncher cavity is connected with RF input signal. And catcher cavity is connected with amplified RF output. If you observe the basic structure, then here we have cathode.
Cathode is connected with electron gun. And here we have anode. Anode is connected with collector.
If you observe cathode, that is connected with negative terminal of supply. And if you observe anode which is collector, that is connected with positive terminal of supply. See this cathode will be generating electron beam.
This cathode will be generating electron beam. How? The reason is we are connecting cathode with negative terminal of supply. So negative terminal of supply will generate electrons.
So electron beam is generated over here. And those electron beam that will be moving in this direction. Now question is why? those electrons are moving in that direction. The reason is here we have anode, here we have collector.
That collector is connected with positive terminal. So positive plate will attract electron. So electrons will be accelerated from cathode to collector over here.
And during that acceleration, here we have two cavities. First cavity is buncher cavity that is connected with RF input and second cavity is catcher cavity that is connected with RF output. At RF output we will be having amplified signal. That amplified signal will be there based on the principle of velocity modulation.
That I'll explain in Applegate diagram. Now what I'll do is I'll explain with detailed analysis of structure. So here we have a clistron tube.
That tube will be of glass tube. Right. Here we have first cavity that is buncher cavity.
That buncher cavity is connected with RF input. So this RF input that is weak in terms of strength. Here we have second cavity that is catcher cavity.
That is connected with RF output where we will be having amplified signal. Here we will be connecting supply with this supply negative terminal that is connected with electron gun that is cathode. and positive terminal that is connected with collector that is anode.
So if you observe the basic structure of supply, then this supply is very essential. The reason is this supply is generating electrons over here. Why it is generating electrons? The reason is this supply is connected as per negative terminal over here. So negative terminal will generate electrons over here and those electrons will be moving in this direction.
The reason is this collector which is connected with positive terminal of supply. So it will be attracting electrons. So electron beam that will be moving in this direction, right? Here if you observe, we have drift space in between these two cavities. Here we have drift space.
So electrons will be drifting in this direction, right? It will be drifting in this direction and that drift is happening because of anode. Here if you observe, See we have gap A.
This gap A that belongs to buncher cavity. See with this gap A, we will be providing velocity modulation to electron beam. So whatever electrons which is coming over here, with which we will be providing velocity modulation inside gap A. And here we have gap B. See with this gap B, we will be catching velocity modulated electrons.
Inside gap B, we will be catching velocity modulated electrons. Let me take one example. See this electron gun that is generating electrons over here.
So let us consider first electron is early electron, second electron is reference electron and third electron is late electron. Early electrons means here earlier electron is generated. After some delay reference is generated and after some delay late electron is generated. Right, now what will happen is as and when these electrons are entering inside gap A, there will be velocity modulation. And because of velocity modulation, what will happen?
See this early electron that will be having lower speed. This reference electron that is having bit higher speed compared to early electron speed. And this late electron will be having higher speed because of difference in speed, what will happen is these electrons, they will be coming at the same time over here at catcher cavity. Let me show you how.
You can observe. If you observe these electrons, they are coming at the same instant means there is a generation of bunch of electron and that is happening because of velocity modulation. Here early electron that is traveling by lower velocity.
and late electron that is traveling by higher velocity and that velocity modulation that is happening inside gap a and because of which as and when they travel over here at that time here there will be generation of bunch of electrons and because of bunch of electrons there will be amplification of signal right see here if you don't provide any rf signal in that case there will be same velocity with all electrons which are generated over here. If you consider we don't provide any RF input over here. At that time there will be finite and fixed velocity which will be there with electrons which are moving over here and that velocity will be as per half mv square is equals to eV where V is voltage applied over here with this electron gun based on that one can identify reference velocity that is square root of 2EV divided by m.
Now I'll explain you Applegate diagram by which you will be having more clarity. If you talk about Applegate diagram then here if you observe, see we are applying voltage across gap and that voltage across gap is provided with the use of Buncher cavity. Buncher cavity means, Here we will be applying RF input signal.
So if I say my RF input signal that is somewhat this. Then here we have negative half cycle and here we have positive half cycle. Now in Applegate diagram, here I will be showing position.
Position is there with respect to gap A and gap B. So here you can observe we have location of gap A and here we have location of gap B. And in between gap A and gap B, we have drift space.
So here we have drift space. Drift space means here electrons are drifting towards collector. Now to explain you velocity modulation, here you can observe we have early electron.
That early electron that will be appearing at negative half cycle of input RF signal. Here if you observe we have reference electron. So reference electron that is appearing at zero input signal.
And here we have late electron that is appearing at positive cycle of input RF signal. And as I have told you early electron that is having lower velocity compared to reference velocity. Reference velocity is a velocity when no signal is applied.
So early electron that is having lower velocity compared to reference velocity and late electron that is having higher velocity compared to reference velocity. Based on that you can observe they are moving, they are drifting towards gap B and over here there is a generation of bunch of electrons. And because of there is a bunch of electrons, it will be providing amplified output, right? Here if you observe calculation in terms of delay, then this lead electron that takes lower time to have a travel from gap A to gap B. If you observe reference electrons time duration, then that is bit higher compared to late electron.
And if you observe duration of early electron, so that is bit higher compared to this reference electron. Right. So here based on velocity modulation, delay to arrive from gap A to gap B that is getting changed.
And because of which. Here we are generating electron bunch and as we are generating electron bunch, we are amplifying input signal and this electron bunch that we will be catching at catcher cavity where we will be having amplified output signal. Right.
Here I have explained few applications with this slide. If you talk about first application that is there based on higher gain. One should know, two-cavity klystron amplifier offers very high gain and because of which one can use it in high power RF applications. It is also used in high power pulsed radar system.
In pulsed radar system, for short duration of interval, we need to transmit high power RF signal. To transmit that high power RF signal for short duration of pulse, one can use two-cavity klystron amplifier. It is also used in satellite communication. See in satellite communication we need to transmit signal to very long distance.
And for long distance communication we need to have high power RF signal that could be generated using two cavity klystron amplifier. So that is how few interesting applications are there. I hope you have enjoyed this session. Till if anything that you like to share just note it down in comment section. I will be happy to help you.
Thank you so much for watching this video.