Any electronic device or component produces Noise. Its a fact of life. Even a passive resistor when at room temperature has movement of its electrons which results in noise. This is termed as Thermal Noise and the minimum this can be with a system at room temperature is -174dBm/Hz (-174dBm measured in a 1Hz bandwidth).
The noise power in a resistor is given by:
where, k = Boltzmann’s constant in Joules per Kelvin, T = absolute room temp = 293 kelvin, B = Bandwidth, 1 Hz in this example. Then converted to dBm’s.
What is Noise Figure?
Noise Figure is a value that defines the amount of noise that a device adds to a signal that passes through it. When many components are added together in a circuit each component contributes to the overall noise generated. This is important for many types of circuit including transmitters and receivers. In a transmit stage, the noise contributes to degradation of the signal quality. In the receiver, noise limits the sensitivity of the circuit. This makes Noise Figure an important parameter to be measured for many electronic circuits.
Continue reading » » Noise Figure, the Y Factor Method and Uncertainties
A spur in electronics and frequency terms is a signal (normally narrow band but could be modulated) that normally is an unwanted product or side effect of a system that has been designed to perform another function. e.g. a mobile phone transmitter is required to transmit information on a specific band, but may as a side effect transmit signals that are also not wanted.
These unwanted spurs cause many issues for both the system they may be generated in, or other systems that may pick up the spurs and be a victim of their presence. Spurs may be out of the immediate band of interest and affect other neighbouring carriers or transmitters. Conversely spurs may be generated in the band of interest for the device being tested and these may significantly affect the transmit signal quality (EVM) and/or the receiver sensitivity of a system.
Such spurs are exhaustively searched for during design, verification test, EMC or other regulatory testing to prove a product complies with CE marking regulations as well as functions to its own manufacturers specification.
Darren Tipton of Rohde and Schwarz UK gives a short video demo of how to generate and analyse an LTE signal using signal generator SMBV100A and Signal Analyser FSV
Darren Tipton of Rohde and Schwarz UK talks to Radio-Electronics.com and investigates what realtime spectrum analyzers are and how they can be used to find signals other analysers cannot see.
Spectrum analysers are devices that allow us to look at signals in the frequency domain rather than in the time domain. They are frequency selective devices that can be used to analyse characteristics of wanted signals, such as channel power, bandwidth, level and also unwanted characteristics of signals such as unwanted side band power, spurious or other interference.
In many cases a spectrum analyzer can be used to gain more information about a signal such as its phase. Such instruments are normally called vector signal analysers due to this added capability and they are able to perform for example modulation quality or frequency vs time measurements on signals by capturing the signal and post processing it.
In this short article we will discuss the differences between swept and real time spectrum analysers as well as what real time means and what advantages or disadvantages it has over traditional methods.
An interesting interview with Dr Wolfgang Wendler, Spectrum Analyzer Product Manager at Rohde and Schwarz discussing the use of the FSVR Realtime Spectrum Analyzer for analysis of Swept Signal Sources at European Microwave Week 2010.
A spur in electronics and frequency terms is a signal (normally narrow band but could be modulated) that normally is an unwanted product or side effect of a system that has been designed to perform another function. e.g. a mobile phone transmitter is required to transmit information on a specific band, but may as a side effect transmit signals that are also not wanted.
Darren Tipton of Rohde and Schwarz UK talks to 