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Design and technological features of manufacturing precision waveguide filters frequency range 37…78 GHz

DOI 10.18127/j00338486-201910(15)-08

Keywords:

S.O. Krumlyakov – Post-graduate Student, PJSC «Radiofizika» (Moscow)
E mail: krumlyakov94@mail.ru
O.M. Korobkov – Engineer of the 1st category, PJSC «Radiofizika» (Moscow)
E mail: studiakom@mail.ru
E.G. Molchanov – Head of Sector, PJSC «Radiofizika» (Moscow)
E mail: molchanov@rastr-radio.ru
A.A. Sudarenko – Senior Lecturer, Moscow Aviation Institute (National Research University); Head of Department, PJSC «Radiofizika» (Moscow)
E mail: alex_radian@mail.ru
I.S. Formalnov – Ph.D.(Eng.), Associate Professor, Moscow Aviation Institute (National Research University); Head of Department, PJSC «Radiofizika» (Moscow)
E mail: formalnov@mail.ru
I.A. Yarchak – Senior Lecturer, Moscow Aviation Institute (National Research University); Head of Sector, PJSC «Radiofizika» (Moscow)
E mail: yarchak9@gmail.com


This article describes the design and technological features of manufacturing precision waveguide filters of the frequency range 37−78 GHz (waveguide channel section 5,2×2,6 and 3,6×1,8). As part of this development, an attempt was made to improve the accuracy of manufacturing and, accordingly, the repeatability of the filter parameters, increase their strength, and simplify the adjustment while ensuring the specified radio parameters and reducing their dispersion.
To achieve the above goals, it is advisable to produce filters from a single billet without the use of soldering flanges, and the deviation of the dimensions should be no more: section waveguide – no more than 10 microns; linear dimensions between the links in the group of not more than 10 microns; connecting flange dimensions of not more than 10 microns.
Such accuracy is higher than the requirements of the standard for waveguide tubes [2], which allows for this technology to produce precision waveguide filters with a small spread parameter. These accuracy are achieved due to the rigidity of the filter design and processing on high-precision machining equipment. Silver-plated brass adjusting screws with M1,6 thread are provided to adjust the filter. It was assumed that the influence of metal adjusting screws on the filter parameters would be extremely large, so the adjusting screws were also made of polyamide with a thread M1,6 [3].
The waveguide filter is manufactured as follows: 1) on the lathe drilled technological hole for the manufacture of waveguide channel on the EDM machine; 2) on the EDM machine is formed waveguide channel of the desired cross section. In the manufacture of the channel takes into account the thickness of the subsequent galvanic coating channel M3. CP6. The roughness of the Ra walls is not worse than 1.25 μm, and the radius of rounding between the mating inner walls of the waveguide channel is not more than 70 μm, in contrast to the standard supplied waveguide tubes, where the radius of rounding is 0.3 and 0.2 mm depending on the cross-section; 3) further, in a single technological cycle, on the universal milling machine MAHO MH500C performed overall, connecting flange dimensions and linear dimensions of the filter links (the symmetry planes of the waveguide channel are used as reference planes); 4) installing diaphragm rod (wire) into the drilled holes and soldering.
According to the above technology, three-link band-pass filters of the 40−44 GHz range were manufactured, their radio technical parameters were set up and tested using the R&SZVA50 vector network analyzer. As expected, the influence of metal adjusting screws on the filter parameters was extremely large, they had to be abandoned. Adjusting screws made of polyamide with thread M1,6 showed suitability for accurate and convenient adjustment of filters. Filters made from a solid metal billet, meet the requirements for precision manufacturing and provide a set of radio parameters and a good reproducibility. Such filters have high strength and are more technological in comparison with a brazed design from a waveguide tube of standard section and milled flanges. The use of adjusting screws made of polyamide provided accurate and convenient adjustment of filters.

References:
  1. Bushminskii I.P. Izgotovlenie elementov konstruktsii SVCh. Volnovody i volnovodnye ustroistva. M.: Vysshaya shkola. 1974. 304 s. (in Russian)
  2. GOST 20900-2014. Truby volnovodnye mednye i latunnye pryamougolnye. Tekhnicheskie usloviya. (in Russian)
  3. Lobachev N.Yu. Issledovanie vliyaniya neodnorodnosti (emkostnogo kharaktera) na amplitudno-chastotnuyu kharakteristiku filtra volnovodnogo Ka diapazona pri zamene elementov podstroiki iz provodyashchego materila elementami podstroiki iz dielektrika. Trudy MAI. 2017. № 92. (in Russian) http://trudymai.ru/published.php?ID=77156.
June 24, 2020
May 29, 2020

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