Wednesday, December 24, 2014
Monday, December 22, 2014
Ando AQ6317B Optical Spectrum Analyzer for WDM, LD, LED and FBG. Diverse and Accurate. On Sale at BRL Test for $11,900
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● Wide dynamic range for 50 GHz WDM-Signals
The dynamic range is 70 dB at peak ±0.4 nm, and
60 dB at peak ±0.2 nm.
High-resolution measurement achieves wide dynamic
range with 50 GHz spacing WDM system.
● High wavelength accuracy
Provides ±0.02 nm wavelength accuracy at 1520 to
1580 nm, and ±0.04 nm at 1580 to 1620 nm, with
±0.01 nm wavelength linearity, making it especially useful
for high-precision loss wavelength characteristics and
other evaluation of WDM devices.
The wavelength scale indicates both in air and in
● High wavelength resolution
Achieves wavelength resolution of 0.015 nm.
● Versatile analysis functions
Analysis functions for WDM and other optical devices
(LD, LED, FBG, etc.).
● Synchronous sweep
In conjunction with an AQ4321 Tunable Laser Source,
much higher wavelength resolution/wide dynamic range
can be achieved by high-speed synchronous sweep.
● High sensitivity
High sensitivity allows measurement of light at down to
-90 dBm, covering from 1200 to 1650 nm.
● Low polarization dependency
Measurements such as gain of optical amplifier can be
proceeded accurately because polarization dependency
is suppressed as low as ±0.05 dB.
● High-level accuracy
Accurate within ±0.3 dB.
● High power measurement: Max. +20 dBm
Even high-power output from an optical amplifier can
be measured directly without an optical attenuator.
● 9.4-inch color LCD
● Pulsed light can be measured
● Three individual trace memories
Monday, December 8, 2014
Martin Rowe -September 17, 2014
"I keep running into the same EMC problems over and over," EMC Engineer Kenneth Wyatt told an audience of some 40 engineers at a meeting of the Greater Boston IEEE EMC Society. The meeting took place on September 16 at the Bose Corp. headquarters in Framingham, Mass.
"EMC problems appear because many designers don't understand how to design for EMC," said Wyatt. He then spent 90 minutes discussing the causes of EMC problems such as gaps in return planes, cable resonance, shielding, and bonding as well as troubleshooting techniques and tools. Many of the topics Wyatt discussed are covered in The EMC Blog and in his new book EMI Troubleshooting Cookbook for Product Designers: Concepts, Techniques, and Solutions.
Gaps in return planes are one cause of the common-mode currents that produce unwanted emissions. Why? Because current returning to its source has to go around gaps, which lengthens the return path and enlarges the loop that current has to travel. In the video below, Wyatt explains where gaps occur, the emissions problems they cause, and what to do about them.
Wyatt then showed some examples of products that failed compliance tests and why they failed. Take LCD panels, a common problem. There are often gaps between the displays and their enclosures, which can let radiated energy escape. Figure 1, from Wyatt's presentation (download slides) illustrates the problem.
Wyatt explained why LCD displays can be a source of unwanted emissions because LED drivers use LVDS (low voltage differential signaling), which clocks the data at rates approaching 500 MHz and use fast edge speeds. These high frequency, fast edges, tend to couple common-mode currents onto the display cable and housing, which creates emissions that can escape from gaps between the display and enclosure. This is especially true as the length of the gap approaches a half wavelength of a harmonic frequency.
Figure 1. Unwanted emissions can escape from around LCD displays.
Poor bonding of cable through enclosures is another problem. Wyatt showed an industrial application where not only wasn't a cable shield connected to a return or reference location, but cables were routed through an enclosure, leaving gaps. Furthermore connectors used for other cables weren't properly connected. That is, connector shells didn't have solid connections to the enclosure. These and other issue can let emissions from clocks and digital circuits out or let outside emissions in.
Wyatt then demonstrated some of the concepts using a Rhode & Schwarz RTE 1104 oscilloscopewith FFT analysis and near-field probes. Figure 2, taken from Gaps in return planes - yes or no?, shows the test setup where he drove two transmission lines—one where the signal traveled over a gap in a return plane and another that didn't— with a digital pulse stream. The harmonics from the emissions were easy to see when the return trace passed over a gap.
Figure 2. A near-field probe and an oscilloscope using an FFT show how a gap in a return plane can create emissions when carrying digital signals.
To close the presentation, Wyatt showed some of the tools and equipment he uses to troubleshoot EMC problems, be they emissions or immunity. His toolbox included
- Loop probes
- Current probes.
- Log-periodic antennas made from PCBs
- RF generators and circuits that generate test signals such as a chattering relay.
- Gaskets, filters, batteries, connectors, and cables
- Several handheld spectrum analyzers. The EMC Blog contains reviews of these and other troubleshooting products.
The evening even had a mini-trade show. Tektronix was there with the MDO4000 and MDO3000mixed-domain oscilloscopes.
Würth Electronik had a table of EMI filters, chokes, ferrites, and connectors. The company held a raffle at the end of the night, giving away two books and a product kit.