Agilent 5991-3855EN English 2014-01-30 PDF 827 KB c20140728 [9] free download

File name 5991-3855EN English _ 2014-01-30 _ PDF 827 KB c20140728 [9].pdf

Keysight Technologies EMC Compliance Testing: Improve Throughput with Time Domain Scanning Application Note Introduction Electromagnetic compatibility (EMC) testing requires detailed and exacting methodologies to ensure that all emissions are accurately measured. Long test times impact test facility availability and reduce the number of devices that can be certified--capping the amount of revenue a testing service can generate or the number of new devices a company with internal test capabilities can introduce without the cost of third party testing. To grow revenue without adding the considerable expense of new test site installations, companies must streamline the EMC product test cycle--which includes setup, scan, turntable rotation, and antenna height adjustment time--to maximize the throughput of their existing compliance facilities. Time domain scan is a technology that can reduce receiver scan time significantly, shortening overall test time to help increase revenue and introduce more products to market faster. This application note will provide you with an overview of time domain scan, discuss the test scenarios in which it provides the greatest time savings, and assess the trade-offs between time domain speed and receiver overload protection. Time Domain Scan Reduces Overall Test Tim Both commercial and military testing standards require specific amounts of measurement time, also known as dwell time, for each signal in order to ensure that impulsive signals are appropriately characterized. Time domain scan reduces receiver scan time while maintaining required dwell times. CISPR-based commercial testing can require dwell times up to 1 second for pre-scans and, in the case of emissions with time-varying amplitudes, 15 seconds or more for final measurements. MIL-STD-461 specifies dwell times of between 15 ms and 150 ms per measurement, depending on the frequency range. These dwell times add up when using receivers that employ frequency domain scanning based on stepped or swept local oscillators to collect data in individual resolution bandwidths. Time domain scanning became acceptable for prescans in CISPR 16-1-1:2010 and is acceptable for final measurement in those CISPR standards specifically calling out the use of this version of CISPR 16-1-1. MIL-STD-461 allows the use of any type of measuring device that meets the requirements of the document. How Time Domain Scan Works Time domain scan reduces receiver scan time through the use of high-overlap fast Fourier transforms (FFT) to collect emissions data simultaneously over a frequency span that includes multiple resolution bandwidths (Figure 1). By contrast, in the frequency domain, data is collected in individual resolution bandwidths. The FFT acquisition bandwidths used for time domain scan can be in the range of 1 to 10 MHz or greater, significantly wider than the required CISPR an