Building on NPL’s exprerience in microwave metrology, we can supply bespoke, National Measurement Institution performance, Radio Frequency and Microwave attenuation standards and measurement systems.

Application

Attenuation standards, together with those for noise, impedance and power underpin almost all reliable microwave measurements made today. NPL has developed, as the UK's national facility, coaxial attenuation systems and we are able to use this experience to build bespoke customer systems.

Either series substitution or Voltage Ratio Systems can be provided, which can be either manual or semi-automated in operation. At the heart of the systems is an Inductive Voltage Divider, normally operating at 10 kHz, which is the attenuation reference. The RF signal passed through the attenuator under test is converted to 10 kHz using RF mixers which are selected for their linear performance. Almost uniquely, the device being measured is connected between isolators and impedance matching circuits, meaning that the attenuator is measured under ‘perfect’ conditions and mismatch corrections are not required. This is one of the keys to the low measurement uncertainties available from our systems.

Robust mechanical construction provided both mechanical stability plus low signal leakage, both important to delivering high quality measurements.

Frequency Coverage

As the systems use a low frequency reference attenuator, the measurement frequency range is determined by the mixers, isolating and impedance matching units. At low frequencies the matching is performed using adjustable LRC circuits, but at higher frequencies commercial transmission line tuners are employed. Typical frequency ranges for these units are 1 to 20 MHz, 30 to 50 MHz, 50 to 80 MHz, 80 to 100 MHz, 0.1 to 2 GHz, 2 to 8 GHz, 8 to 18 GHz, 18 to 26.5 GHz, 26.5 to 40 or 50 GHz. 

Dynamic range

The dynamic range of the systems vary with frequency, but can typically measure total attenuation values of 110 dB at 30 MHz, falling to 60 dB at 50 GHz. 

Supported devices

The software and hardware will support the majority of commercial precision attenuators (either fixed or switched) fitted with 7 mm, 3.5 mm, 2.92 or 2.4 mm coaxial connectors.

Manuals and training

NPL is able to deliver not just system components, but full documentation including operating procedures. Training in the system use can be provided, either at NPL or at the user’s laboratory.

Uncertainties

The systems offer state of the art measurement uncertainties and, being developed from our own standards, deliver comparable measurement uncertainties to that available from NPL’s measurement service. Our capabilities have been verified and accredited by the United Kingdom Accreditation Service (UKAS) and our current capability can be found on their website and the BIPM Calibration and Measurement Capability database.