In many applications — radar, microwave communications, military, aerospace — and during the prototyping and testing phases of development, complex waveguide arrangements are commonly encountered by system designers. Unfortunately, these alignment issues are not foreseen until deadlines are approaching and critical systems must be deployed or tested. To respond to these needs, Pasternack Enterprises is offering 36 high quality, flexible waveguide twist sections, in stock and ready for same-day shipping. Pasternack’s neoprene sleeve “flexguides” cover the waveguide frequency bands from 5.85 to 40 GHz – WR137 to WR28 – in 12", 24" and 36" sections, solving an expanse of waveguide alignment and displacement challenges.
In many installations and test bench scenarios, a precisely designed, rigid waveguide structure with the proper flanges and orientation is not readily available. Lead times of several weeks to months are common to receive the correct part. This is not always convenient in a design, repair or replacement situation. Flexible waveguides at various lengths allow twisting and flexing over a considerable range, which solves many installation problems caused by misalignment. Microwave antenna or parabolic reflector positioning is another example which may require physical adjustment many times to ensure proper alignment. In these applications, flexible waveguides allow a much wider range of alignment possibilities without the cost or lead time for customized parts.
Even rigid waveguide may not provide the necessary features for some installations. For applications that produce vibration, shock or creep, a flexible waveguide may be preferred over a rigid waveguide, as the flexibility can provide isolation to more sensitive waveguide parts. Additionally, where applications have high temperature variability, thermal expansion and contraction can damage even mechanically robust interconnect structures. Flexguide is able to contract and expand slightly to accommodate thermal variations. In situations with extreme thermal expansion and contraction, an additional bend loop can be incorporated to enable greater displacement.
SUPERIOR ELECTRICAL PERFORMANCE
The flexguide models cover the 5.85 to 40 GHz waveguide bands and have WR137 to WR28 flanges. The typical VSWR for the lowest frequency flexguide is 1.05, and the highest frequency model achieves a low VSWR of 1.3. The quality of the waveguide structure results in little change in VSWR over the 12", 24" or 36" lengths. The lowest frequency, 12" waveguide provides 0.07 dB insertion loss (see Figure 1); the same length at the highest frequency achieves 0.6 dB loss. Insertion loss tends to increase linearly with length. Though VSWR and insertion loss may change slightly under different flex and twist configurations, the high quality flexguide construction reduces variation from manipulation.
The malleable conduit structure of the flexguide is superior to many prior implementations of flexible waveguide. The flexguides can bend in both the H- and E-plane, with the higher frequency models able to bend with an E-plane radius as tight as 1" and an H-plane minimum bend radius of 2". The flexguide can twist in both directions, up to 180 degrees for the higher frequency models. The lowest frequency model is capable of a one-time minimum bend radius in the E-plane of 4" and 8" for the H-plane. The maximum twisting capability of the lowest frequency model is a one-time offset rotation of 64 degrees. The maximum operating pressure for the flexguides ranges from 30 to 45 psig. The physical structure that enables this high performance, even under high flex and twisting, is the specialized helically-wound, silver coated brass strip construction. The precision wound strips are then coated in a highly flexible and durable neoprene sleeve. With this construction, the flexguides resist thermal variations in length and size, and they are capable of attenuating vibrational energy without sustaining damage.
Pasternack’s flexguide sections are available in a wide range of rectangular and circular flanges, which are made of solid brass. Several models in the range from 5.85 to 40 GHz are offered with military standard MIL-DTL-3922 (UG) features for flange waveguide interconnect. For the models that cover 5.85 to 12.4 GHz, commercial connector pressurized rectangular (CPR) flanges are available. For pressurized waveguide systems, a flexguide component can reduce stresses on the more rigid pressurized sections, potentially lengthening lifetime and reducing maintenance and service requirements. The complete set ranges from WR137 to WR28, with square cover flanges available for the frequencies from 10 to 22 GHz.
The neoprene rubber material used as the sleeve for the flexguides provides a much more flexible and environmentally resilient sleeve than rubber and PVC sleeve technologies. Even thin neoprene coatings are capable of preventing moisture, acids, corrosives and gas exchange between the membrane and outside environment. Neoprene coatings can withstand many bends, flexures and minor physical abrasions without further splitting and cracking, while flexible waveguide without neoprene can crack and expose the highly corrodible metals of a waveguide body to damaging environmental conditions. Neoprene coatings are stable over time and degrade more slowly than other materials, offering longer waveguide lifetimes in harsh environments.