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Bend Radiuses of U.FL Cables' Coax Types: 1.13, 1.32, 1.37, RG174, RG178

George Hardesty
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Bend Radiuses of Coaxial Cable Types for U.FL Cables

Using very thin and flexible coax for U.FL cables is often necessary, even though the more flexible options have the most signal loss.

The more flexible the coax, the more signal loss among the options. However, it is often required or essential to use very thin and flexible coax for two reasons:

  1. In tight spaces (inside cases and enclosures), a thin coax option is often necessary. Sometimes, the limited size of ports requires using the most flexible 1.13 coax, or 1.32 or 1.37.
  2. Thicker coax may make the U.FL connector pop off the jack: When connecting the U.FL connector to a jack on a mini-PCI card or board, the tight space often requires the use of 1.13, 1.32 or 1.37mm coaxial cable because it is very thin and flexible. Very thin cable is typically needed in tight spaces inside enclosures, so the U.FL connector will snap down on the jack without popping off.

rg178-coax-for-ufl-cables

The five coax types in the table below are the only five types that can be used with U.FL connectors. All thicker coax types are too large in diameter to be used with U.FL. 1.13 coax, or 1.32 or 1.37 are known as micro or mini-coax.

Flexibility and bend radius will affect the performance of U.FL cable assemblies when they are routed and used in radio frequency circuits. The minimum bend radius of a coaxial cable is the minimum radius at which it can be bent without physical damage or impairing its performance. It is usually around five times the outer diameter of the coax (though this is not hard and fast).

Coaxial cable Bend radius (mm/in) Diameter (mm/in) Max. frequency (GHz)
1.13 aka 1.13mm  4.5 / 0.177 1.13 / 0.04 6
1.32 aka 1.32mm 5.5 / 0.216 1.32 / 0.051 6
1.37 aka 1.37mm 9 / 0.354 1.37 / 0.053 6
RG 174 coax 9.9 / 0.393 2.79 / 0.11 6
RG 178 coax 10.16 / 0.4 1.83 / 0.072 3

Comparison of shielding characteristics; 1.33mm, 1.32mm, 1.37mm, RG-174

Exceeding the bend radius limit will cause:

  • The cable to become kinked
  • Disruption of the concentric layered structure of the cable
  • Displacement of the inner conductor
  • Warping of the outer braided shielding
  • Impedance changes within the cable
  • Discontinuities along the length of the cable that cause an increase in VSWR, signal loss, and reflections
  • Degraded overall performance of the radio frequency circuit in which the bent cable is used

This means that coaxial cable with increased flexibility is a favorable selection in settings where a low bend radius is critical for reliable routing. As the cable is passed, it often has to bend around fixed structures that can create a corner in the cable if it is not adequately flexible. The table at the top of the page compares the bend radius of the five coax cables and the diameter and maximum frequency range for a quick comparison.

See a list of all of our articles about U.FL cables and connectors.

The U.FL connector by Hirose is a lightweight micro-miniature coaxial cable connector known for its low profile (mated height of only 2.5 millimeters) and consistent performance at microwave frequencies up to 6 GHz. It consists of a male jack, usually PCB-mounted, and a female plug forming a reliable mechanical and electrical connection confirmed by a tactile click sensation. The small mounting area of this ultra-small surface-mounted coaxial connector makes it ideal for applications where wireless connectivity is required within a device.

ROHS Complaint: Data-Alliance.net

All coaxial cable featured is manufactured in compliance with the European Union's Restriction of Hazardous Substances (RoHS) legislation, its international equivalents, and existing Conflict Minerals legislation, including Section 1502 of the Dodd-Frank Act.

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