Twt pdf

Download PDF. A short summary of this paper. To evaluate thermal and structural aspects of the coaxial coupler and helix assembly with three APBN support rods, related studies of the coupler assembly with ten turn of helix and output wave guide coupler for the Ku-band W space TWT during extreme case of operation, i. Pg; Fe; Ua 1 Introduction waveguide adapter and helix SWS becomes an issue.

Space helix TWT is a vacuum microwave device In helix SWS assembly, ten turns of helix2 are being that is used as high power microwave amplifier in used. Earlier, the design of coupler consisting of 1 communication satellites. The input and output window assembly and transformer section has been coupler play an important role in efficiently coupling done without considering rf connector and helix SWS the microwave power in and out from the helical slow in their real geometrical situations3.

Each of these wave structure SWS of a TWT with minimum components has been simulated by its characteristic reflection and transmission loss. The coupler mainly consists of a coaxial RF window 2 Thermal analysis assembly and RF transformer assembly. The window The objective of thermal analysis is to assess the assembly is basically a metallic sleeve housing a temperature distribution, axial stress, radial stress, ceramic disc with a central hole for the inner hoop stress, and thermal expansions as well as amount conductor and terminated with suitable rf connector.

ANSYS finite welding of the inner conductor of the coaxial line. A transient thermal analysis inside a metalic envelope. The design of coupler is used to determine the temperature distribution as a becomes critical if the design is performed with function of time or heat storage. Table 1 shows the peripherals at one end as it is attached with the helix thermal contact conductance TCC values. SWS while at the other end with the rf connector.

Here, the output coupler of the space helix TWT has 2. A special The helix is heated by the RF power 10 W , which coaxial to wave-guide adapter has been designed for is dissipated because of surface resistivity and by the coupling power to the standard wave-guide WR beam current intercepted by the helix i.

Table 3 shows the ceramic window is taken as heat load, which is temperature distribution at different parts of output estimated by considering low insertion loss in the coupler assembly, when thermal contact conductance is window assembly of W of the tube.

Table 2 shows applied as given in Table 1 with boundary conditions of the heat loads with base plate temperature as well as Table 2. The temperature is applied to the helix, across insulator i.

Ku-band W radiation cooled space helix TWT. The above boundary conditions have been applied. It is clear from the graph that temperature difference across junction is decreasing with Window Cup The Ceramic Window To learn more, view our Privacy Policy.

To browse Academia. Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Mukesh Alaria. A short summary of this paper.

Download Download PDF. Translate PDF. An approach has been developed for the efficient design and analysis of the coaxial couplers in the practical situation. Normally multi-section impedance transformer approach is used for any wide band coupler. For a space helix TWT, coupler should be wide bandwidth and small size.

In this case coupler is matched with helix slow wave structure and the standard ohm connectors. The simulated return loss dB profile for different type of couplers is obtained by using Ansoft HFSS, CST microwave studio and compares those with experimental results.

The tip loss design at sever ends for the input and the output section has been also optimized. Keywords Helix. RF multi-section transformer. WR waveguide 1 Introduction Space helix TWT is a vacuum microwave device that is used as high power microwave amplifier in communication satellites [1]. The input and output couplers play an important role in efficiently coupling the microwave power in and out from the helical SWS of a TWT with minimum reflection and transmission loss.

Coaxial couplers are extensively used in space TWTs of moderate output power up to Watts because of their large bandwidth and small size. As in Ku-band out put power is W, a special coaxial-to-wave guide adapter has been designed for coupling power to the standard wave guide WR through the window assembly as was discussed in the earlier paper [2]. The design of coupler is very critical as one end of it is attached with helix SWS and other end with the rf connector impedance 50 ohm.

Earlier, the design of coupler consisting of window assembly and transformer section has been done without considering the rf connector M. Sinha : A. Bera : V. In the present approach, both the rf connector and the helix SWS were simulated in their real situations with the coupler assembly for space helix TWT.

In this approach a type special coaxial-to-wave guide adapter is attached with the window assembly and the helix SWS with tip loss is attached at the other end of transformer section. Coaxial ceramic window of material The thickness of the alumina window was chosen minimum possible 0. Two steps in the diameter of the central conductor were introduced and their lengths were adjusted for fixed total length to get the best possible VSWR at mid frequency.

The performance was evaluated at end frequencies and the dimensions were adjusted for optimum VSWR over the desired frequency band. The design of impedance matching networks is an important part of microwave tubes. There are several techniques like impedance transformation approach and multi reflection approach are used to design these impedance matching networks. For narrow band application a single- section quarter wave transformer is adequate. Multi-section quarter wave and tapered line transformers are used when a very good matching is required over a broadband frequency [3].

At low frequency the length of a quarter wave multi-section transformer is quite long for some specific applications. For example, at 3. To fulfill the requirements of a space TWT coupler, i. Figure 1 shows the schematic diagram of Ku-band helix TWT. Using theory of impedance transformation for a single section, the transformed impedance at the plane 1 shown in Fig.

The second section transforms this impedance Z01 at the end of second section, i. Source Load 2. In the design of coupler we are using 11 turn of helix SWS attaching at the end of transformer section and port II is declared at the end of helix SWS [5, 6].

In this case rf connector is also attached at the window ceramic side and its end port I is declared at input source. In the helix SWS, there is tip loss attached at four turn of helix other end to prevent backward modes. Here, the tip loss is modeled as resistive loss. Its value should be such that the amount of reflection of waves from it is minimum.