In the early stages of a products development cycle, Spectrum Analyzers and EMI Receivers are used to perform quick scans after design changes are made and to see if the product will pass compliance testing. EMI test receivers and spectrum analyzers are often categorized as the same because both measure amplitude of signals with respect to frequency. However, both have different units and their workings also prove to be a point of differentiation as well. To efficiently undertake product development, it is important to understand the difference in the workings of both EMI receivers and spectrum analyzers. This article will highlight the points of distinction amongst them and enable you to figure out when one is to be used over the other.
Contents
What is an EMI Receiver 1
What is a Spectrum Analyzer 2
Differences in EMI Receiver and Spectrum Analyzer 2
Conclusion 3
What is an EMI Receiver
Electromagnetic radiation sources, such as motors and machines, are the most common sources of Electromagnetic Interference Receiver, commonly known as an EMI receivers. This is of two types i.e., conducted interference and radiated interference. The coupling of signals on one electrical network to signals on another electrical network via a conductive medium is referred to as conducted interference. While, the interference source linking its signal to another electrical network over space is referred to as radiated interference.
What is a Spectrum Analyzer
A spectrum analyzer, such as ones supplied by LISUN, is a device that evaluates the magnitude of an input signal versus frequency over the instrument’s whole frequency range. Its most common application is to determine the strength of a spectrum of known and unknown signals. To make sure the important timing criteria are not breached, resolution bandwidth, video bandwidth, and sweep time are locked together in most spectrum analyzers. These parameters, on the other hand, can be manually adjusted and even coerced into modes that display erroneous measurements.
Differences in EMI Receiver and Spectrum Analyzer
Both EMI Receivers and Spectrum Analyzers are utilized in the measurement of conducted and radiated emissions originating from electronic devices. These are basic tools for the measurement of radiofrequency signals. These devices showcase a radiofrequency signal’s amplitude on the vertical scale, whereas the frequency is displayed on the horizontal scale.
Because of the similarities of the devices, they are often characterized as being the same. Nevertheless, it is pertinent to understand their differences. Swept spectrum analyzers continually tune the frequency of their local oscillator to cover the frequency range of interest. However, to cover the frequency range of interest, certain EMI receivers execute a stepped sweep, in which the instrument is tuned to fixed frequencies in defined frequency step sizes. Each tuning frequency’s amplitude is measured and saved for later processing or display.
There is no preselection on most swept spectrum analyzers, which is the extra filtering included into the instruments front-end just before the first frequency conversion mixing stage. When measuring low repetition frequency pulses with quasi-peak detection, this frequently results in an insufficient dynamic range, which might lead to erroneous measurement findings. However, preselection is present in EMI receivers.
Some spectrum analyzers do not include a preamplifier. While, EMI receivers typically include a preamplifier after the preselection stage, resulting in a substantially lower noise floor number. As a result, EMI receivers are far better at picking up signals that would otherwise be lost in the noise floor of less sensitive spectrum analyzers.
Engineering needs, budget and compliance requirements are major factors that play a part in which receiver type amongst EMI receiver and spectrum analyzer is best suited for a specific testing. To perform a fully compliant emissions testing, a fully CISPR 16 compliant EMI receiver is to be used. These come with correct intermediate frequency filter bandwidths, a normal absolute amplitude accuracy, dynamic range as well as specific input impedance. Obviously, these kind of EMI receivers are at a higher price point than a spectrum analyzer which doesn’t fully meet CISPR 16 requirements.
However, if you only require to conduct engineering scans and in-house pre-compliance measurements to get an idea of whether your design will pass full compliance testing which will be later done out of house, you can work with a spectrum analyzer instead of a fully compliant but expensive EMC chamber. They normally only have the peak detection function and not the average detection ones which is not an issue in the sense that pre-compliance testing is usually done to figure out if the product will pass full compliance test without actually setting up full equipment according to applicable emissions standards. It will be beneficial for you to know the highest frequency used or even generated in your product so you can appropriately purchase either the EMI receiver or the spectrum analyzer.
Conclusion
EMI receivers and Spectrum Analyzers are similar but different devices that can be used to determine the amplitude versus frequency of RF emissions originating from electronic devices. In conclusion, we can say that to properly perform work related to product development, it is essential to understand the point of differentiation among the two devices. Knowing when to use one device over the other, thus proves to be pivotal in efficient and effective product development.
