Uses for Matching Pads

The terms Impedance Matching Pads, resistive impedance transformers, or minimum loss pads all refer to the same RF components that solve a relatively common problem in some applications that have equipment, components, and devices at different standard impedances. For example, many broadcast, TV, and military communication systems use 75 ohms as a standard characteristic impedance, where the bulk of RF test equipment and many other components/devices are at 50 Ohm standards. There are also 93 Ohm standards that often need interconnection with 50 Ohm systems.

Generally, impedance matching pads are coaxial adapters that have a resistive impedance matching network from one impedance standard to another, such as 50 Ohm to 75 ohm. These matching pads may also have connectors that readily connect with common connectors used at the given impedance standards, such as N-type for 50 Ohm and F type for 75 Ohm.

Key Impedance Matching Pad Specifications

• • • Frequency Range/bandwidth
  • • VSWR
  • • Attenuation
  • • Attenuation tolerance
  • • Input Power (CW and Peak)
  • • Connector Standards
  • • Impedance
  • • Industrial/Military standards compliance

Like other inline RF passives, the main specifications for Impedance matching pads are bandwidth, VSWR, attenuation, impedance, and power handling. As Impedance matching pads are designed to reduce reflection and optimize the power transfer between two different interconnect impedance standards, VSWR and attenuation are two of the main specifications. Attenuation tolerance is also often specified, as RF components often have a wide variation in resistance values, and many applications that use impedance matching pads have tight tolerances on output power (such as broadcast).

Depending on the application, the derating curve for the input power may also be included. In particularly high temperature or harsh environments, this may be crucial in preventing damage to the matching pad, as most specifications are given at around ~25C at sea level. Another note is that the resistive nature of impedance matching pads means that they are not suited to DC pass or DC block circuits and may not perform as desired under a DC and RF stimulus.

Learn more about Pasternack’s offering of Impedance Matching Pads