PIM noise mechanism and prevention process of Double Ten Technology

Date:2022/9/27 10:05:41 / Read: / Source:本站

PIM noise mechanism and prevention process of Double Ten Technology
PIM noise is generated by the small arc deformation at the joint end of the microwave component and the oxidation of the metal connection layer
Two main reasons. In the design, manufacture and assembly process of equipment, the materials selected and the design process must be
Pay attention to the above factors. If connection deformation is unavoidable under special circumstances, consider linking the relevant parts to
Microwave strong electric field shielding isolation.
(1) Heat dissipation of the uplink high-power waveguide
When the high power signal is transmitted in the microwave transmission line, the small insertion loss will also produce a large amount
The heat. In the transmission of lokW power, 0.05dB loss of heat generation power is 144.4W, resulting in component
The temperature changes if the two sides of the waveguide connection flange are made of different metal materials and the thermal characteristics of the materials are not
In the same way, there will be a temperature difference under the action of heat. The test shows that the temperature difference within 3℃ will cause a small crack
The slit, though not discernible to the human eye, is enough to cause PIM noise. So on the pedestrian power transmission
Ensure good heat dissipation and keep the temperature difference between components within 3 ° C.
(2) Manufacturing principles of microwave components
RF COMPONENTS prone to PIM NOISE SHOULD BE MANUFACTURED FROM one PIECE OF metal WHENEVER POSSIBLE, SUCH AS BY machining or electrocasting
Technology. Adjustment screws or other metal-to-metal contacts should not be used, and a light wall pin should be used instead of the traditional one
Screw adjustment to avoid sharp edges of many screws in the RF field. For the waveguide filter and its
His complex waveguide element, which cannot be fabricated from a single metal material, can be divided into two pieces along the H-plane of the waveguide
Workers to shape.
When designing the mounting frame for the waveguide and feed components, it is necessary to check and ensure that adequate flange hardware is installed through
In order to ensure that the correct torque is provided when the system is installed.
The waveguide assembly shall be made of oxygen free high conductivity copper (OFHC) material. No other metal materials shall be used.
For large components such as feeds, the deformation caused by gravity deformation should be fully considered. During feed acceptance,
To use the same posture and work, and increase the power of the test, to observe whether the PIM noise
Sound, feed output signal without PIM noise, is qualified.
(3) Fabrication of WR137 waveguide
WR137 waveguide shall be made of copper material with high conductivity and not easily oxidized
Choose brass, on the surface of the flange can not be coated with resistance or other insulating materials, such as chemical film, paint
And so on. When the waveguide and flange are assembled, the melting point of the welding must be higher than the safe temperature.
If oxidation occurs on the joint surface of the waveguide flange, a metal-oxide layer - metal two-pole will be formed
The tube structure, thus under the action of a strong electric field under nonlinear effects, produces a variety of intermodulation components, if these
If the frequency spectrum falls into the receiver band, it will seriously affect the normal operation of the system.
(4) Shielding and assembly technology in strong electric field
The assembly of various microwave components in the microwave high-power transmission channel (inside the waveguide and in the radiation field)
The process must! · Fastidious.
In the bearings of components such as waveguide switches, lubricating with conductive grease. The waveguide is connected in all directions
Torque should be even to ensure seamless connection of waveguides. In the main side, side of the stage, should try to avoid metal bump
And ribbon conductors exposed to strong magnetic fields. The BWG shield cylinder assembly is welded and strong enough
Degree to prevent deformation and bending after a period of time.
In short, in the high-power RF radiation field or the airspace covered by the RF field due to radio wave diffraction, should be
Avoid discontinuities in metal equipment. BWG support rod, sensor installation and wiring, operating platform or ladder
The assembly and so on must conform to the specification.

Author:admin


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