Custom Waveguide Straights, Bends, Twists, and Flanges

The waveguide sections offered by SAGE Millimeter cover the frequency range of 8.2 to 325 GHz. These sections include waveguide straights, bends, twists, mode transitions and flange adapters. The waveguide sections are designed for full-band operations from X-band to WR-03. Other lower frequency waveguides may be available upon request.

Standard waveguides offered by SAGE Millimeter use copper with gold plated surfaces and brass flanges. These waveguide sections are manufactured with high precision machining to ensure high quality and ruggedness. They also offer low insertion loss and can be utilized for system integration in subassemblies and test set-ups.

Figure 1. Waveguide Straight Sections

Rectangular and Circular Waveguide Basis
Depending on which field is perpendicular to the direction of wave propagation, waveguide transmission lines are classified in Transverse Electric (TE) and Transverse Magnetic (TM) modes. Transverse Electric and Magnetic (TEM) mode, when both electric and magnetic fields are perpendicular to the direction of travel, typical of coaxial components, cannot be achieved using waveguides as it requires two conducting mediums.

Rectangular waveguides support TE and TM modes. The commonly used rectangular waveguide mode is TE10, which is the dominant mode as it gives nonzero field expression with the lowest cut-off frequency for respective waveguide dimensions.

The dimensions of the circular waveguide are related to which waveguide mode the waveguide is operating in. The fundamental mode is TE11 and the higher order mode is TE01. As the electric field is perpendicular to the waveguide wall in TE01 mode, there is no conductive loss during wave propagation. Therefore, TE01 mode is widely used in the industry for low loss and high-power transmission.

Waveguide Flanges
Standard flanges offered by SAGE Millimeter for different frequency bands shown in Table 1 are designated for brass and cover flanges only. “U” is the flange designator assigned to the waveguide size. For example, flange UG-383/U is assigned to WR-22. When the same flange is used for another band, the “M” designator is added. For example, flange UG-383/U-M is used for the WR-19 waveguide. The “M” designator is also used to represent the flanges with circular waveguides. There is a push in the industry to use UG-599/U (a square shaped flange for the WR-28 waveguide) for WR-22 and WR-19 applications.

Table 1. Technical Flange References for Rectangular Waveguides

BandWaveguide DesignatorFrequency Range (GHz)Historic Flange
XWR-908.2 to 12.4UG-39/U
KuWR-6212.4 to 18.0UG-419/U
WR-5115.0 to 22.0MIL-F-3922/70-010
KWR-4218.0 to 26.5UG-595/U
WR-3422.0 to 33.0UG-1530/U
Ka (A)WR-2826.5 to 40.0UG-599/U
Q (B)WR-2233.0 to 50.0UG-383/U
UWR-1940.0 to 60.0UG-383/U-M
VWR-1550.0 to 75.0UG-385/U
EWR-1260.0 to 90.0UG-387/U
WWR-1075.0 to 110UG-387/U-M
FWR-0890.0 to 140UG-387/U-M
DWR-06110 to 170UG-387/U-M
GWR-05140 to 220UG-387/U-M
WR-04170 to 260UG-387/U-M
WR-03220 to 330UG-387/U-M

Customization in Waveguide Sections and Flanges
Apart from standard insertion lengths offered on the website, for waveguide straight sections, custom sections are available from 0.5 inches to 6 feet (12.7 mm to 1.8288 meters). The maximum length of the waveguide sections is determined by its frequency. An increase in frequency means a decrease in waveguide dimensions, therefore at higher frequencies there are more manufacturing constraints. In addition to customized lengths, SAGE Millimeter offers custom materials (Stainless steel, Aluminum, and OFHC: Oxygen-Free High Thermal Conductivity Copper), and surface finishes (Silver plated, high temperature black paint coating exterior, Rhodium plated, etc.).

Figure 2. 90° Waveguide Bend and 90° Waveguide Twist

In addition to standard 45° and 90° bends and 45° and 90° twists, SAGE Millimeter also offers customized bends and twists. Table 2 displays selected customized waveguide sections offered by SAGE. A single section accommodating multiple bends and twists with arbitrary angles are offered upon request. Detailed drawings and STEP files are encouraged while submitting the RFQ. Note that waveguide bends and twists are only available for rectangular waveguides. For circular waveguides, only machined straight sections are available.

Figure 3. Custom Waveguide Bends and Twists

All waveguide sections have flange customization options such as anti-cocking flange, choke flange, and grooved (O-ring and EM Gasket) flange. The standard flanges are prone to leakage, increased insertion loss, and discontinuity. Issues caused by inconsistent mating can be prevented by using anti-cocking flanges shown in Figure 4 (a).

Table 2. Customizations Offered by SAGE Millimeter for Waveguide Sections

CategoryCustomizationsCompatible Waveguides
Bends and Twists • Section Length
• Bend/Twist Angle
• Twist Direction
• Combined E-H Plane Bends and Twists
• Rectangular
Flanges • Anti-Cocking
• Choke
• Groove (O-Ring)
• Rectangular
• Square
• Circular
Flange Materials • Brass
• Aluminum
• Copper
• Rectangular
• Square
• Circular
Surface Finishes • Gold Plated
• Silver Plated
• Rhodium Plated
• High Temperature Black Paint Coating Exterior
• Rectangular
• Square
• Circular
Waveguide Materials • Stainless Steel
• Aluminum
• OFHC
• Rectangular
• Square
• Circular

Figure 4 (b) shows grooved ‘O’ ring flanges that are primarily used for environmental and/or pressure sealing. This flange can be used together with standard flanges [1]. Moreover, grooved flanges can further be customized with a choke with the addition of an inner groove. As shown in Figure 5, the inner groove is a quarter wavelength in radius as well as depth. The choke creates a good electrical connection between two sections that permits energy transmission with little reflection or loss [2].

Figure 4 (a). Waveguide Mode Transition with Anti-Cocking Flange
Figure 4 (b). Flexible Section with Grooved ‘O-Ring’ Flange

Figure 5. Waveguide Choke Flange

Cover, choke or grooved flanges can be used with EM gaskets to provide shielding and pressure sealing. Gaskets are used for applications which require low flange leakage, low insertion loss, minimum out gassing and maximum heat transfer. For waveguides to be used in thermal-vacuum conditions, SAGE Millimeter is may offer flanges with a pressure inlet and pressure windows on a case by case basis. Pressure windows are used to isolate pressurized sections and non-pressurized sections, provide protection against contaminants and offer sealing at high pressures such as 35-40 psi. To pressurize waveguide systems with clean air or other gases, on request, SAGE Millimeter offers 1/8” NPT female pressure inlet on flanges.

References

  1. http://www.giwaveguide.com/flange-types/
  2. https://www.radartutorial.eu/03.linetheory/tl13.en.html

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