Coaxial connectors are universal interconnect devices, but they also have certain limitations. One of these is power handling, which is a significant consideration in many applications of SMA connectors. SMA connectors come in many variations, including standard, precision, ultra-precision, and special-purpose SMA connectors for high voltage and other applications. While the diversity of SMA connectors means that finding one that meets key technical parameters is relatively easy, it must be noted that the power handling capabilities of these connectors are not necessarily the same.
In some cases, the power handling capability of an SMA connector is not listed in the datasheet. This may be because a given SMA connector can be designed to mate with a range of coaxial cables, where the connector's power handling capability exceeds that of the coaxial cable. Another possibility is that SMA power handling depends on the frequency range and mounting method. Generally, for most connectors and RF components/devices, power handling is a function of frequency. Most RF devices can handle less power at higher frequencies due to increased losses at higher frequencies.
SMA Through-Wall Female Connector, Precision Connector, Solderable Terminal Block, .250 inch Diameter
One of the main reasons for limited power handling is that electrical losses lead to the conversion of electrical energy into heat, and high heat efficiency causes the component materials to overheat. The dielectric spacer between the center and outer conductors of an SMA connector is typically a polymer with a rated temperature just below 200 degrees Celsius (typically 165 degrees Celsius). This is why the rated power is usually a specific number of watts within the specified frequency range at the highest temperature. There are some high-power or extended-power SMA variants that can exceed the power handling capabilities of other SMA connectors from the same manufacturer. Because these ratings and methods vary from manufacturer to manufacturer, careful consideration may be needed to ensure that an SMA connector with appropriate capabilities is selected.
For example, an SMA connector rated only 12 GHz may have a higher power handling capability than an SMA connector rated 26.5 GHz. However, a 26.5 GHz SMA may actually have a higher power handling capability at 12 GHz, just not at its peak frequency. Because SMA connectors operate at frequencies exceeding 30 GHz, with some having a peak operating frequency of only 8 GHz, this adds additional complexity when comparing the power handling of SMA connectors.
SMA Male Low PIM Connector, Soldering Accessory, for Coaxial Cable PE-1/4SFHC, SPP-250-LLPL, SPO-250, SPF-250
Standard frequency SMA connectors may have a continuous wave (CW) power handling capability of 100W at temperatures ranging from ~100°C to 125°C. Precision SMA connectors operating at 26.5 GHz or 30+ GHz may only be able to handle power between 50°C and 75°C. Some SMA connectors have a power handling capability exceeding 200 watts, but depending on the manufacturer, their operating frequency range may be limited to 18 GHz or even 12 GHz. Some manufacturers may list peak power handling with pulse rate and duty cycle instead of CW power handling rate, or list it together with the CW power handling rate.