RU2475901C2 - Method to seal waveguide microwave devices - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: in the method to seal waveguide microwave devices the entire internal volume of devices after assembly of internal elements is filled with granules of foam polystyrene, previously foamed in a water environment to loose density, which is equal to apparent density of foam polystyrene in devices, and then they are foamed directly inside devices.

EFFECT: achievement of high extent of dust and moisture protection of waveguide systems without change in their characteristics, in particular, a standing wave ratio, increased vibration and shock resistance due to additional fixation of ferrite, dielectric or other elements placed inside wave-guiding channels.

Description

The invention relates to radio engineering and can be used for sealing antenna, waveguide, nonreciprocal and other microwave devices.

In the practice of microwave devices (I.V. Lebedev, Technique and microwave devices. Edited by N.D.Devyatkov, Moscow, Vysshaya Shkola, 1970, pp. 156-157), small-sized sealing windows containing a dielectric plate and an installed on one side of it is a metal diaphragm, vacuum-tightly welded to each other and the walls of the sealed waveguide.

Known waveguide microwave window canned type (SU 1725685 A1, publ. 28.02.1994), a sealing window (RF patent No. 2400873, IPC H01P 1/08, publ. 09/27/2010) containing dielectric walls with compensating elements (diaphragms, disks and etc.).

The disadvantages of these devices are the high complexity and cost of manufacture, the deterioration (growth) of the VSWR (standing wave coefficient), caused by the phenomena of reflection at the interface of the waveguide medium (air, vacuum) with a dielectric constant of 1, and the material of the dielectric partition (quartz, fluoroplast, polycarbonate) with a dielectric constant of more than 2, as well as additional dispersion and reflection from the fastening elements of these windows.

A known method of sealing using a sealing section with a foam liner (Handbook of radio relay communication. Edited by SV Borodich, Moscow, "Radio and communication", 1981, pp. 67-68). Foams have a dielectric constant of less than 2, and their use in the design of the sealing waveguide section provides better alignment with the path. Therefore, in this solution, the correct selection of the shape and material of the foam liner can partially solve the problem of deterioration of VSWR. However, the proposed design of the sealing waveguide section is complex, time-consuming, difficult to implement in waveguide devices of small cross sections (millimeter range) and also contains fasteners that degrade the performance (VSWR) of the device.

In addition, all of the listed devices, performing the function of dust and moisture protection of waveguide paths, do not concern the solution of the problem of increasing the reliability of fastening ferrite and dielectric elements located in some waveguide nodes and devices to create structures that are resistant to shock and vibration.

The closest in technical essence to the proposed technical solution is a method of filling the elements of the body of the waveguide module with special foam, is given in the patent for the invention "Waveguide detector module of the millimeter wavelength range" (RF patent No. 2345450, IPC H01P 1/00, publ. 01.27.2009 )

The essence of the method lies in the fact that the body of the device consists of two halves, each of which, before installing the internal elements of the device (in this case, a diode with a Schottky barrier), is filled with PEN-01 powder using simple equipment. As a result of exposure in the oven for 2 hours at 80 ° C and for 6 hours at 120 ° C, foaming of the powder occurs and the waveguide channels are filled with foam. Next, the diode is mounted and the device is assembled. This solution provides moisture protection and resistance to shock.

The disadvantage of this method is the need to fill with foam plastic each part of the body of the product separately. In addition, for the subsequent installation of internal elements, foaming must be performed in a snap-in providing cavities for these elements. Thus, for each new device requires special equipment, the manufacture of which increases the cost of manufacturing the device. In the event that several elements are attached to the waveguide path, sealing according to the principle described in the invention RU 2345450 (fixing elements on the connector line of the waveguide path) can either complicate the design of the device itself and the equipment for foaming, or may not be possible at all.

The technical result of the invention consists, firstly, in achieving a high degree of dust and moisture protection of waveguide systems without changing their characteristics, in particular the standing wave coefficient (VSWR), and secondly, in increasing their vibration and shock resistance due to the additional fastening of ferrite, dielectric or other elements placed inside the waveguide channels, thirdly, in the absence of the need to complicate and / or change the design of the device (windows, additional connectors) for its sealing, fourthly, in the absence of due to the need to manufacture special equipment for foaming, fifthly, the ability to seal complex microwave devices with many internal elements, which is impossible in other ways while maintaining a high degree of dust and moisture protection, as well as vibration and shock resistance.

The technical result is achieved in that the entire internal volume of the devices after installation of the internal elements is filled with polystyrene foam granules pre-foamed in an aqueous medium to a bulk density equal to a given apparent density of polystyrene foam in the devices, and then foamed directly inside the devices.

From considerations of minimizing losses and reflection phenomena, the requirements for the foam -ε≤1,2 and tg δ≤1 · 10 ^-3 follow. Expanded polystyrene with an apparent density of less than 0.15 g / cm ³ , which can be obtained from expandable post-styrene, in particular PSV-SU grade (TU 2214-097-05766575-2002), fully meets these requirements.

It was experimentally established that the best results in uniformity of filling of waveguide devices, in reducing insertion losses of microwave energy and in eliminating the likelihood of shifting elements installed in waveguide channels are achieved by introducing expanded polystyrene foam into the product before foaming (hereinafter, the product means a finished microwave device with already mounted internal elements), pre-foaming operations.

In order to eliminate small non-foaming particles and large particles with a high porophore content that cause inhomogeneities in the final material, the initial powder of expandable polystyrene granules was sieved through brass grids to obtain a particle fraction from 0.5 to 1.0 mm in size. A portion of the sifted material was brought to a bulk density close to the calculated apparent density of polystyrene foam in the product. This avoids the redistribution of granules during the final foaming of expanded polystyrene in the product, which eliminates mechanical pressure on the elements installed in the waveguide channels. The pre-foaming operation was performed by briefly (about 5 seconds) immersing the granules in boiling water, followed by cooling in cold water. Next, the pre-expanded granules were dried (over calcined silica gel) and used to fill the products.

A portion of pre-expanded polystyrene foam was calculated by the formula:

P = V Where P is the mass of pre-expanded polystyrene foam (g), V is the volume of the filled device (cm ³ ), ρ is the set density of polystyrene foam in the product (0.1-0.15 g / cm ³ ).

Granules of pre-expanded polystyrene were placed as evenly as possible in the product to be filled. Next, the open channels of the product were plugged with technological covers, and the product was heated to a temperature of 100 ° C. During heating, the granules of the material soften, expand and melt together, forming after cooling a single monolithic foam with a uniform cellular structure, which firmly fixes ferrite, dielectric or other elements placed inside waveguide channels. The product was cooled to room temperature in a vacuum to reduce the shrinkage of polystyrene foam.

By this method, sealing waveguide sections with a cross section of 2.2 mm × 1 mm and a length of 100 mm were made, Y — circulator splitters, ferrite switches filled with polystyrene foam.

Measurements in the operating frequency band on a panoramic swivel meter of type P2-65 showed that filling the waveguides leads to an increase in losses of not more than 0.05 dV.

For circulators and ferrite switches, after filling with expanded polystyrene (with pre-foaming), the value of direct losses increased by no more than 0.1 dB, the change in the value of reverse losses was less than 2 dB, and the VSWR increased by no more than 0.1. The achieved indicators did not change after the thermo-wet tests of group 2.1.1 GOST. PB 20.39.304, as well as after exposure to transport vibroloads and shock loads with acceleration up to 1000 g in three mutually perpendicular directions.

Claims (1)

A method of sealing waveguide microwave devices, characterized in that the entire internal volume of the devices after mounting the internal elements is filled with polystyrene foam granules pre-foamed in an aqueous medium to a bulk density equal to a given apparent density of polystyrene foam in the devices, and then foamed directly inside the devices.