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NARROWBAND DISPLAY
A method of displaying a pulse spectrum where the resolution bandwidth is less than the spacing between the lines (pulse repetition frequency) of the pulse spectrum.
NETWORK ANALYSIS
Measurement technique used to characterize the behavior of electrical networks with the aid of a generator and receiver. The most common measurands in RF engineering are the twoport network parameters, known as the S-parameters.
NOISE BANDWIDTH (NBW)
More accurately: equivalent noise bandwidth. Describes the equivalent bandwidth of a filter for broadband (white) noise and is the bandwidth of a rectangular characteristic filter having the same power transfer function as the selection filter (same area under the curve). The relationship between NBW and the resolution bandwidth (RBW) of a Gaussian filter is approximately:
NBW = 1.2 x RBW
NOISE DISTORTION
This term describes the non-linear behavior of circuits or devices when driven with a broadband noise signal. The resultant signal includes both harmonic distortions and intermodulation products of the various components of the noise signal. The distortion noise is the determining factor for the noise power ratio (NPR).
NOISE FIGURE
A measure of the deterioration of the signal-to-noise ratio as a result of generated internally spurious products. Expressed in linear (F) or logarithmic (F/dB) form. The noise figure is directly related to the noise floor:
Ln = Ltherm x NBW x F
Ln/dBm = Ltherm/dBm + 10 log (NBW/Hz) + F/dB
where:
Ln = noise floor (level)
Ltherm = thermal noise level (–174 dBm pro Hz)
NBW = noise bandwidth
F = noise figure
The noise figure is thus a useful measure of sensitivity.
NOISE FLOOR
The level of broadband noise produced internally by the receiver stages of the analyzer. The noise floor determines the sensitivity and hences the lower end of the dynamic range. The noise floor value is always quoted referred to the input port of the analyzer.
NOISE POWER RATIO (NPR)
A parameter to qualify the behavior in presence of an evenly distributed broadband load: the ratio between the density of a noise input signal to the analyzer and the density of the spurious responses of the analyzer ( û ~ noise floor, û ~ noise distortion, intermodulation noise).
In order to measure the NPR, white noise is injected into the analyzer. Appropriate band limitation filters limit the noise bandwidth to the desired frequency range.
An additionally connected blocking filter (band-stop filter) suppresses the noise in a narrow spectral range. The NPR of the DUT (here: the analyzer) results from the ratio between the level in the noise band and the level measured in the blocking range of the noise squelch.
Measuring the noise power ratio of the analyzer
NORMALIZATION
Digital correction of frequency response error used in network analysis. The measured values of various standards are stored and used as references for the actual measurement.
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