Noise Figure Measurement Device

Frequency selective noise figure measurements.

Noise figure measurement device. Measurements can be made to be frequency selective independent of device bandwidth and spurious responses. Starting may 2009 our discussion of noise temperature has been moved to a separate page. A mixer may be necessary if you want to convert the rf frequencies to desired if frequencies. Theoretically the measurement results of the same rf device should be identical but due to limitations of rf equipment.

Example agilent s n8973 noise figure analyzer is used to measure the performance of the prototype. The 50ohm noise figure of a device can be directly measured using the noise parameter system or extrapolated from the noise figure contours. If several devices are cascaded the total noise factor can be found with friis formula. Noise figure is the noise factor expressed in decibels.

Nf decibels noise figure 10 log f noise figure is more often used in microwave engineering but noise calculations use the noise factor as we will soon see. Snr input linear input signal watt. This is accomplished by feeding the noise source directly into the instrument. First the analyzer is configured for a 1 5 to 2 5ghz sweep and calibrated.

The noise figure that results from a noise figure measurement is influenced by how well the noise source matches to the device under test and the match of the device under test to the measuring instrument. In this article three methods to measure the noise figure of rf devices are discussed. The equipment connections are as shown in the diagram below. Designing lnas means understanding how the active device s gain and noise figures change as a function of the source impedance or admittance.

Below is a summary table of the pros and cons. Noise figure measurement using noise figure meter. Using a spectrum analyser may not as accurate as those obtained when using a dedicated noise figure meter but this is very dependent upon the spectrum analyser and the measurement method used. In case you don t need a frequency mixer simply connect the if out cable to the noise source and calibrate.

They each have advantages and disadvantages and each is suitable for certain applications. The concept of noise figure allows the sensitivity of any amplifier to be compared to an ideal lossless and noiseless amplifier which has the same bandwidth and input termination. Noise figure nf is a measure of how much a device such an amplifier degrades the signal to noise ratio snr. Noise figure of passive devices.

The analyzer then measures its own noise figure at various attenuator settings.