T&M Designline Top Ten articles for 2011

As we come to the end of another year we take a look back at what the readers of the Test & Measurement Designline were attracted by this year.

1. Oscilloscopes and ENOB
For scopes with bandwidth in the GHz range, one quality metric involves characterizing a scope’s analog-to-digital converter (ADC) using effective number of bits (ENOB).  Joel Woodward and Brig Asay of Agilent Technologies explore that when selecting which scope to use, how important is ENOB and how effective is ENOB at predicting a scope’s measurement accuracy?

2. Design and implementation of a low cost MCU based current loop calibration device
Abdulkadir Çakır, Fırat Yücel and Hakan Çalış discuss the design and implementation of a low cost microcontroller based current loop calibration device to test and calibrate systems that communicate via 4-20 mA current loop standard. The device they have designed has 0.001 mA resolution on the current sourcing. It is also both capable of measuring and providing requested current between the range of 4 and 20 mA either automatically in the format of step or ramp based function or manually by entering current value via a numerical keypad.

3. Blood glucose meter design
A glucometer is a medical device for measuring levels of glucose concentration in the blood, depending on the level, administration of an hypoglycemiant drug might be required for the patient. A glucometer will use a test strip to interact with a patient’s drop of blood. Cuauhtemoc Medina Rimoldi describes how a glucometer works.

4. Perfect timing: performing clock division with jitter and phase noise measurements
As clock speeds and communication channels run at ever higher frequencies, accurate jitter and phase noise measurements become more important, even as they become more difficult and expensive to manage. Howell Mitchell of Silicon Labs describes some practical pointers and observations to assist in situations where clock signals have been divided down from higher frequency voltage-controlled oscillators (VCOs).

5. Jitter and timing analysis in the presence of crosstalk     
Serial data standards continue to proliferate, providing dramatic improvements in PC and Server system performance. Testing these higher speed standards for evidence of jitter is critical for long-term stability and to achieving the objective of a good Bit Error Ratio (BER) in the design. Chris Loberg of Tektronix says effective analysis begins with selecting the right instruments and have a good understanding of instrument noise, rise time and factors such 3rd, 4th, 5th harmonic performance.

6. A measurement approach for IQ offset and imbalance of LTE mobile devices
Imperfect analog front-ends of mobile devices cause transmit signals to be non-ideal. Typically, the signal processing for inphase and quadrature (IQ) components is likewise affected. On the one hand, the undesirable zero‐offsets of both digital‐to‐analog converters lead to the IQ offset, and on the outstays her hand, the IQ imbalance originates from an imperfect up‐conversion of the baseband signal. Christian Kuhn of Rohde & Schwarz explains an estimation of the IQ offset has to take into account the special structure of the physical layer of LTE, which is defined in the 3GPP physical layer specification TS 36.211.

7. DSOs: The banner specs tell only part of the story
Dan Strassberg says a scope’s performance in capturing anomalous waveforms depends on little-known and often poorly understood characteristics. The headline specifications may fail to reveal much of the information you need about important aspects of its behavior. Depending on how you plan to use the scope, you might discover that the headline specifications fail to reveal much of the information you need about important aspects of the instrument’s behavior.

8. Hunting noise sources in wireless embedded systems
When integrating a radio chip or module into a typical embedded system, a common and often frustrating task designers face is tracking down and eliminating noise and spurious signals. Darren McCarthy of Tektronix explores tips and techniques for hunting noise sources using a new type of instrument called the mixed domain oscilloscope.

9. Vector network analyzers aid breast cancer screening research
High speed vector network analyzers are being used by Bristol University spin-out Micrima for the clinical trials of their revolutionary breast cancer screening technique. The technique ,which avoids exposing women to X-ray radiation, is fast and inexpensive. It is also expected to be better at identifying breast cancer in younger women.

10. Understanding the impact of digitizer noise on oscilloscope measurements
Noise can make it difficult to make measurements on a signal in the millivolt range, such as in a radar transmission or a heart-rate monitor. Noise can make it challenging to find the true voltage of a signal, and it can increase jitter, making timing measurements less accurate. It also can cause waveforms to appear “fat” in contrast to analog oscilloscopes. Jim Lim of Tektronix exp;lains how you can use ENOB (effective-number-of-bits) testing to more accurately evaluate the performance of digitizing systems, including oscilloscopes.