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RF Technology hands-on training. Participant : Diaconu Alexandra Supervisor: K. Verlamov D. Belozerov Labor a tory : University Centre. Used equipment:. В6-9 selective microvoltmeter. SRS SG384 RF generator. AKIP 4115/5A Oscilloscope.
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RF Technology hands-on training Participant: Diaconu Alexandra Supervisor: K. Verlamov D. Belozerov Laboratory: University Centre
Used equipment: В6-9 selective microvoltmeter SRS SG384 RF generator AKIP 4115/5A Oscilloscope KEYSIGHT E5071C Vector Analyzer (VA) Power meter
Introduction • First Labsweredevoted to the determination of the wave length in various transmission lines. • Three measurement lines are covered: • Waveguide (P1-7) • Coaxial (P1-34) • Planar (P1-17) Р1-34 coaxial line Р1-7 waveguide line Р1-17 planar line
Wave types in waveguides: Н-waves (transverse electric, ТЕ) — Н vector has both longitudinal and transverse components, and E vector has only the transverse one. E –waves (transverse magnetic, TM) — Е vector has both longitudinal and transverse components, and H vector has only the transverse one. E H A lot of TE and TM wave types exist. Indexes m and n are used for different field modes notation (TEmn , TМmn).
Standing wave When the short-circuiting plug is installed at the end of the transmission line, the standing wave is formed in the waveguide. I.e. forward wave in the waveguide will be totally reflected from the load.
Diaphragms Reactive dowel Diaphragms are the thin metal plates with an aperture, placed in the waveguide section. Diaphragms are being used as reactive elements for resistances matching or as filter resonant circuits elements. • Metal rod with the r radius inserted to the waveguide through the wide wall • Used in RF technics for the narrow band matching (ZW = ZL only for narrow frequency band) • When ℎ<𝜆/4 and 2𝑟≪𝜆/4 — capacitive behavior • When ℎ≈𝜆/4 — short circuit • When ℎ>𝜆/4 — inductive behavior
Small Inductive Diaphragm Open Waveguide Measurements using Vector Analyzer Match load Capacitive Diaphragm Big Inductive Diaphragm
Directional coupler (DC) • A device used to branch off part of the power of the forward or reflected wave from the main RF transmission line. • Consists of two waveguide segments that have a common thin wall (wide or narrow). • The wall separating the waveguides has holes that serve as coupling elements; through these holes a small part of the power is branched off from the primary waveguide to the secondary one. • The number of holes, their shape and size determine the characteristics of the coupler. • Used in accelerators to power several elements from one source, to determine the incident power in the main waveguide (by measuring the power in the branch waveguide).
The simplest waveguide directional couplers are those with a single coupling element. Such DCs are usually made of rectangular waveguides with an H10 wave connected through a small hole. The most common design of a DC with a single coupling element is the Bethe-hole directional coupler. A round hole in the middle of the common wide wall of two waveguides is used as a coupling element.Can be used to measure the power in the primary waveguide. When joining waveguides of different cross sections, a reflected wave may occur. To avoid it, special connectors are used.
Phase shifter Phase shifter is a device intended for smooth or discrete change of the phase of an electromagnetic wave. It is used in accelerators to shift the phase of devices powered from a single source but operating on different phases. I used in my laboratory work a dielectric phase shifter. • Before being mounted on the accelerator, the phase shiftermust be calibrated. • For this purpose, a shortcircuitor is used —a movable short-circuiting plug (piston) with a scale. • A short circuitor allows compensating the phase change with aphase shifterby moving the piston. • Using the short circuitor scale, it is possible to determine how far the phase has shifted.
Attenuator An attenuator is a device intended for reducing the power of electromagnetic waves propagating along the RF transmission line. In my laboratory work I used the adjustable attenuator.
Before being installed on the accelerator, the attenuator must be calibrated. • This lab work was devoted to the calibration by successive substitution: comparison of the attenuation by the reference and calibrated attenuators.
Model of the flat-top dee of the DC280 with coupling like on cyclotron U-400M This model is used for training,to tune the frequency and adjust the matching on the cyclotron using rotative loop coupling. The frequency range of Model of the flat-top dee of the DC280 : fа = 70÷200 MHz
Conclusion: • I learned how to calibrate the equipmentand how to perform various physical mesurements. • I made different determination of the wave length in various transmission lines. • With the help of diaphragms and reactive dowel I mesured SWR(standing wave ration) andTWR (traveling wave ration). • I have worked with directional coupler(DC), phase sifter, attenuator, equipment which will be used for the linear accelerator. • I learned how to tune the frequency and adjust the matching on the cyclotron using rotative loop coupling.
