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Keysight Technologies
Essential Capabilities of EMI Receivers



Application Note
Contents


Introduction ............................................................................................. 3
CISPR 16-1-1 Compliance ...................................................................... 3
MIL-STD-461 Compliance ...................................................................... 4
Important features not required by CISPR 16-1-1 or MIL-STD-461 ..... 5
Limit lines .......................................................................................... 5
Correction factors ........................................................................... 6
Signal lists ........................................................................................ 6
Tools to aid signal maximization ................................................... 7
Time domain scanning .................................................................... 7
Amplitude Distribution Function (APD) ....................................... 7
Built-in diagnostic tools ................................................................. 8
Spectrum analyzer ...................................................................... 8
Strip chart ................................................................................... 9
Spectrogram ............................................................................. 10
Report generation ......................................................................... 10
Conclusion ............................................................................................. 11
Related literature .................................................................................. 11
Web .......................................................................................................... 11




2
Introduction

Receivers used for EMC compliance testing require certain features and specifications in order to
comply with the appropriate standard. For example, a receiver used for commercial compliance testing
must comply with CISPR16-1-1, while a receiver used for military compliance testing must comply with
MIL-STD-461. Other features, while optional, can be critical for making measurements or providing
analytical capabilities essential for diagnostics. These analytical tools can be valuable in the isolation
and identification of emissions problems.

This application note will discuss what makes an EMI receiver fully compliant and provide an overview
of some of the most useful internal diagnostic tools for quickly and efficiently analyzing and measuring
unwanted emissions. Important features not required by CISPR 16-1-1 or MIL-STD-461 but that are
critical for making measurements will also be discussed.


CISPR 16-1-1 Compliance
CISPR is the "Special International Committee on Radio Interference". The committee provides recom-
mendations used by governmental regulatory agencies to establish regulations pertaining to emissions
and immunity standards. CISPR 16-1-1 is the standards document that describes the requirements for
commercially compliant EMI receivers.

To better understand what is specified in CISPR 16-1-1, we will begin by defining the four CISPR
reference bandwidths (200 Hz, 9 kHz, 120 kHz and 1 MHz). The first 3 bandwidths (6 dB) fit a mask
specified by CISPR, while the 1 MHz bandwidth is defined by its impulse bandwidth, also specified by
CISPR. There are five CISPR bands: A, B, C, D, and E, which fall within the range of 9 kHz to 18 GHz.
Each CISPR band is paired with one of the four CISPR reference bandwidths.

Table 1. CISPR bands and the corresponding reference bandwidths CISPR Band
Bands Frequency range CISPR reference bandwidth
A 9 to 150 kHz 200 Hz
B 150 kHz to 30 MHz 9 kHz
C 30 to 300 MHz 120 kHz
D 300 MHz to 1 GHz 120 kHz
E 1 to 18 GHz 1 MHz


Also specified in CISPR 16-1-1 are four detectors: Peak, Quasi-peak, EMI average and RMS average.
There can be other detectors available as part of the receiver, such as average and negative peak,
but they are not specified by CISPR. If the receiver offers a spectrum analyzer mode, then even more
detectors are made available to the user.




3
CISPR 16-1-1 Compliance (continued)
Of all the detectors, the peak detector enables the fastest possible sweep time. The
peak detector displays the max value of each trace bucket (also known as a frequency
bin) and does not use any type of averaging. This provides good results for CW signals
but does not give a good representation of random noise.
The CISPR-recommended method of measurement suggests measuring with the peak
detector first. If the DUT passes the limit, then the test is done. If the DUT does not
pass, then the user must re-measure using the quasi-peak or EMI average detector.
In addition to the detectors and bandwidths, the receiver must also meet these require-
ments: