Monthly Archives: November 2015

What You Need To Know About EMI Antennas

Any electronic device, system or subsystem generates EMI or ElectroMagnetic Interference and is susceptible to EMI generated by others. To allow them to coexist and cooperate, all such electronic devices, systems or subsystems must confirm to specific standards, which limit the amplitude and frequency range of EMI generated and tolerated by each of them.

Testing for such radiated emissions and immunity involves EMI chambers and OATS or Open Area Test Sites. To check for EMI generated, these chambers or OATS will have several types of antenna that can handle a wide range of frequencies. As visits to a full-compliance lab are expensive and time intensive, you may want to do pre-compliance tests, for which, it is a simple matter to set up a temporary antenna in a conference room or basement. This helps in troubleshooting and correcting EMI problems beforehand.

Several factors decide the nature of the antenna you should be using for your tests. The choice for the tests mostly ranges among radiated emissions, radiated immunity, pre-compliance, full compliance, frequency range, power and size of the antennas. The most common EMI test people perform is for checking radiated emissions. Here too, the antenna you use will depend on frequency, size, gain and your budget.

For pre-compliance tests, the most popular antenna is the hybrid. This is also called by names such as Combilog, Biconilog, Bi-log and others. Hybrids are so favored because of their wide frequency range, which easily covers different ranges from 30 MHz to 7 GHz, depending on the model. This is a very big advantage, as you do not need to switch antennas in between the tests, which you have to do if you were using log-periodic or biconical.

For a lab, where precision is more important, using multiple antennas gives an advantage in the performance. Typically, a lab might use a horn antenna for frequencies above 1 GHz, a log-antenna from 1 GHz to 200 MHz and a biconical antenna for frequencies below 200 MHz. However, for pre-compliance tests, hybrids or Bi-log antennas are adequate for makeshift labs.

The size of the antenna you can use depends on the space you have in your makeshift lab. Larger antennas cover a wider frequency range along with better sensitivities as compared to those offered by smaller antennas. Some designs of hybrid antennas come with bent elements, which help to fit them in limited spaces. In general, hybrid antennas are larger than most dedicated antennas.

Antennas are available that allow you to use them for both radiated immunity as well as radiated emission tests. However, for immunity tests, it is important to limit the power you drive into an antenna to get the required field strength. Typically, immunity testing requires larger antenna sizes as compared to those necessary for measurements of emissions alone.

Hybrid antennas usually combine a log-periodic element with a biconical element. This extends the frequency range the antenna covers as compared with that covered by single-type antenna. For example, one of the newest hybrid antennas covers the entire range of 26 MHz to 3 GHz, while being able to handle signal power up to 300 W for immunity tests.

What is Digital Signal Processing?

Initially, when DSP or Digital Signal Processing was introduced over thirty years ago, it involved standalone processing. A single micro-controller handled all the parameters for processing the analog signal and transforming it to its digital value. Evolution in this area has introduced multicore processing elements that now extend the DSP’s range of applications.

Simultaneously, evolvement of software development tools for the DSP now allows expansion for accommodating diverse programmers. Therefore, on one hand you can have voice and image recognition with small, low power, but smart devices, while on the other, it is possible to have real-time data analytics with the multiple core high-performance compute platforms. This way, DSPs offer nearly endless opportunities for achieving low-power processing efficiencies.

Although initial DSPs processed only audio, engineers quickly adapted DSP technology for a wide variety of applications. Today, DSPs are available as standalone or as part of an SoC or System-on-Chip offering full software programmability including all the benefits of software-based products.

DSPs take already digitized signals from the real world, such as audio, video, pressure, temperature or position for further mathematical manipulations. Engineers design DSPs for performing quick mathematical operations such as add, subtract, multiply and divide.

This processing of the signals enables displaying, analyzing or converting information to a signal of another type to be useful. In the real world, several analog products are available to detect and manipulate signals such as pressure, temperature, light or sound. These signals are then passed on to converters such as ADCs or Analog to Digital Converters, which transform the analog signals into a digital format of 1’s and 0’s.

The DSP takes over this stream of digitized information and processes it further. The processed digital information goes back for use in the real world. The DSP does this in one of two ways. It feeds the information in the digital format to instruments capable of handling it. Where that is not possible, the digital signal passes through a second converter or DAC, the Digital to Analog Converter and this converts the digital signal to analog. All this happens at very high speeds.

An MP3 player is a very simple illustration of the concept of DSP. The analog audio, during the recording phase, passes through a receiver containing a microphone and an amplifier. An ADC then converts this analog signal into digital information, before passing it over to a DSP. The DSP processes the digital signal further as defined by its internal algorithm and encodes it as MP3, before saving the file to memory.

While playing back the recorded information, the DSP decodes the file from memory and a DAC converts the digital signal to an analog form. That makes it suitable to output the signal through an amplifier and speaker system. If necessary, the DSP handles other functions such as level control and equalization including user interfacing.

A computer can also use information from a DSP. The computer can use this information to control security, home theater systems, telephones and for compressing video. Compressed signals are more efficient when transmitting. Additionally, the computer can easily manipulate or enhance the signals to improve their quality.

Predict Solar Eclipses with Wolfram on Raspberry Pi

Wolfram Research shows how the Wolfram language, used on a Raspberry Pi or RBPi, can help visualize solar eclipses. With this combination, you can view past and present solar eclipses. The most astounding aspect is the solar eclipses you visualize can be not only total or partial, but also as if seen from Earth, Mars or Jupiter.

Depending on your present geographical location, you may or may not be able to witness a solar eclipse. To recapitulate, solar eclipses are events where the Moon blots out the Sun to observers on the Earth. The Moon may be so positioned it blocks out the entire Sun or a part of it. If the Moon blocks out a part of the Sun, the incident is termed a partial eclipse. In a total eclipse, an observer on the Earth will only see the corona of the Sun as a halo around the Moon as it covers the Sun entirely.

By mathematically tracking heavenly bodies, it is possible to predict when a solar eclipse is likely, if it will be visible from a specific location and whether it will be partial or total. Usually, the media drums up a small hype of the event, predicting local weather conditions, telling people how and when to observe the eclipse while including other relevant details. However, this is only if the eclipse is visible in your area.

For people on the Wolfram Community, geographical hurdles do not exist. Novices, experienced users and developers from all over the world share data and knowledge. The Community discusses the latest solar eclipse with anticipation, observation and data analysis. They also participate in the computations for future and extraterrestrial eclipses.

For example, consider the total solar eclipse that occurred on March 20, 2015. Before the event, Jeff Bryant and Fransisco Rodriguez from Wolfram explained how the community could compute the geographical locations from where the eclipse would be totally or partially visible. Fransisco used GeoEntities to highlight with green those countries that would witness at least partial solar eclipse on the date.

Although they predicted the visibility of the solar eclipse, neither Jeff or Fransisco was able to see even the partial solar eclipse, as the former is in the US and the latter in Peru. In their prediction, the intense red area shows the regions from where the total eclipse would be visible, while the lighter red areas depict regions of visibility of the partial eclipse. Another total solar eclipse is predicted in the next decade, of which, at least a partial phase will be visible from almost all countries of the world.

Wolfram now has a new language function, the TimeLinePlot. This is a great way to visualize a chronological event such as a solar eclipse. With TimeLinePlot, you can specify the last few years and the next few years to plot territories and countries from where a total solar eclipse will be visible. TimeLinePlot complies with ISO 3166-1 when depicting territories and countries. Using the incredible powers of computational info-graphics, Wolfram predicts a spectacular total solar eclipse spanning the US from coast to coast on August 21, 2017.

Phosphorene Challenges Graphene as a Semiconductor

Though silicon has been the basis of semi-conductors for decades, it is facing stiff competition from other materials that promise to deliver several extras to consumers who like to enjoy more flexibility with their gadgets.

For some time, graphene, a one atom thick allotrope of carbon has been under consideration for use in electronic devices because its thin structure allows electrons to travel across it much more rapidly than they would do across silicon. However, graphene has severe limitations, as its conductivity is a little too high to be of much use in electronic devices, which need semi-conductors or materials with medium levels of conductivity. Another newly developed material dubbed phosphorene, which can form identical thin layers and is a semiconductor as well, offers a wider scope in electronics.

Phosphorene particulars

Scientists at the Technical University of Munich (TUM) have prepared a semiconducting material with black phosphorus in which a few phosphorus atoms have been swapped by arsenic atoms. Replacement of the phosphorus atoms with arsenic has caused the band gap to reduce to 0.15eV, which makes the material an effective semiconductor.

Phosphorene or black arsenic phosphorus can form very thin layers like graphene. Unlike silicon, which is hard and brittle, phosphorene is easy to manipulate into different kinds of structures and shapes. This makes possible a great range of electronic devices with considerable mechanical flexibility.

Scientists at TUM have built on technology that allows the fabrication of phosphorene with the application of high pressure. This reduces the production costs considerably. The research workers have been able to fine-tune the band gap exactly according to specific requirements by tweaking the arsenic concentration. According to Tom Nilges, who is heading the research team at TUM this has enabled them to produce a wide range of materials with diverse electronic properties that were not possible earlier.

Field Effect Transistors

American scientists from Yale University and the University of Southern California (USC) have collaborated with the researchers at TUM to build devices like field effect transistors with phosphorene. A group headed by Dr. Liu and Professor Zhou of the Electrical Engineering Department at USC has studied the transistor characteristics.

Infrared Detectors

Further exploration of the material by the scientists revealed that the material when heavily doped with arsenic could be used for infrared detection. For instance, when the arsenic concentration is as high as 83%, the band gap in phosphorene is about 0.15eV. This fact makes it an effective sensor for infrared rays of long wavelengths. Researchers expect that the new substance can be effectively used as Light Detection and Ranging (LIDAR) sensors, which find use in applications for tracing dust particles and pollutants in the atmosphere and as distance sensors in vehicles.

Anisotropic behavior

Another noteworthy feature of phosphorene is its anisotropic nature. Electronic and optical properties of the material were studied using ultra-thin films in two mutually perpendicular, x- and y-axes. It was observed that the properties were different in the two directions.

Phophorene has an edge over other newly discovered thin-layered semiconductors because it is very easy to peel off layers from a parent black phosphorus crystal.

Let Raspberry Pi Track Bats for You

If you live in an area that has fruit trees around, it is likely bats share your space. Bats are furry mammals that flit about at night, feasting on insects and fruits. Although they are not gifted with good eyesight, they locate prey and avoid obstacles using echolocation. They are expert fliers and it is difficult to observe them since they are so silent.

Although humans cannot hear bats, it does not mean these creatures make no noise. In fact, using the process of echolocation, bats produce a considerable amount of sound. However, humans cannot hear them because the sound bats produce has a frequency range beyond human hearing capabilities. Depending on age, humans can hear sounds produced in the frequency range between 20 Hz and 15-20 KHz. Bats can hear and produce sound up to about 110 KHz. That is why a Raspberry Pi or RBPi is necessary to collect process and graphically represent bat calls.

An analysis of bat calls shows the sounds they produce are quite loud and not limited to just one tone. Different breeds of bats produce a variety of sounds, differing just as bird chirping does. For example, their tone may sweep down from a high frequency to a low one, or move around a specific frequency.

Holger and Henrike Korber from Germany have used an RBPi to make a bat detection device. To collect the sound produced by bats, they use an inexpensive microphone of high sensitivity capable of responding to high frequencies. The algorithm they use allows not only a graphical representation of the calls, but also identification of the bat species as well. Additionally, the software allows manipulation of the calls to bring them into frequencies within the human hearing range and create histories of bat activity.

On their site, which translates to Bat Conservation in English, the Korbers offer a list of bat literature. If you can know the German language, you will find a treasure of information on echolocation and acoustic identification of bat species. To read in English, pass the page through Google Translate.

Details of their new WLAN-Raspi-Bat detector are available here. The detector, based on the RBPi Model B+, is wirelessly connected to an external notebook. That allows easy manipulation of the configuration and wireless recording of data. The RBPi bat project uses a UMTS stick for WLAN communication and a modified image of the RBPi OS.

The WLAN-Raspi-Bat detector sends SMS text messages automatically and at freely configurable times. For example, this could be just after the RBPi has booted or just before it shuts down. As the detector is portable, it is important to save on power consumption and data space on the SD Card. To keep the arrangement simple, the Korbers use a simple clock timer to start and shut down the RBPi. As bats venture out only at night, the RBPi can sleep during the day along with the bats.

As the detector communicates wirelessly, there are numerous applications. For example, it is able to operate at locations hard to access, such as in trees up to the canopy and in buildings with difficult access.

How Gesture Sensors are Revolutionizing User Interface

Imagine a scenario where you control almost everything by simply waving your arms and not by punch any buttons or touching a screen. Welcome to the complicated world of gesture controls. Mechanical buttons and switches are subject to the risk of reliability – they also need protection from the environment. When replaced with electrical controls, such as resistive or capacitive displays and buttons, these do bypass the problems faced by mechanical switches. However, to operate, they still need the physical touch of the operator.

By using optical sensors, it is easy to avoid the reliability risk, mechanical complexity and the requirement for physical touch. You can find optical sensors being used as proximity detectors in many applications such as in water and soap dispensers. Apart from the ease of operation, optical sensors provide the primary potential in recognizing user gestures, thereby reducing system complexity and enhancing user functionality. Today, gesture sensors have evolved to revolutionize user interface controls. They offer the ideal combination of functionality, performance and ease of implementation.

For instance, gesture sensor TMG3992 and others offer simple digital interfaces and do not demand significant processing or memory bandwidth to operate. Being interrupt driven, such sensors interact with the system only when they encounter a recognized event. Simple electrical and software designs are enough to implement two and four direction gesture sensing applications. The sensors work easily from behind plastic or glass transparent to infrared light. That means there is no added complexity or reliability risk in incorporating gesture sensors in electronic devices, as most use plastic housings transparent to infrared.

Gesture sensors help the industry in myriad ways. For example, heavy industries use gloves that limit options for user interface. Operators need specialty gloves to operate most capacitive touchscreens, as they do not respond to commonly used gloves. On the other hand, there are no restrictions for gesture sensors to operate with any type of gloves.

Gesture sensors are eminently suitable for recreational applications such as cold weather or aerial sports and industrial applications such as clean room manufacturing, chemical industries and construction. For example, a skier may keep his or her hands warm within gloves and yet operate a smartphone or manipulate a self-mounted camera with ease.

Touchscreens do not work in environments under water. However, divers can make full use of gesture sensors. It is true water attenuates infrared light and restricts the working distance, so you need additional power. However, multiple benefits overcome this minor restriction. Using gesture sensors such as the TMG3992 and similar greatly simplifies the user interface as underwater cameras can do the job, while the TMG3992 replaces several mechanical buttons and switches for a smaller and more reliable interface.

Smartphone designers and manufacturers already include several user interface options offering multiple solutions for different tasks. However, in many situations – such as exercising or cooking – it is inconvenient to touch the phone while performing the tasks. Gesture controls provide the user different ways of interacting with the phone – such as when checking notifications and scrolling through them. For example, the user can identify a caller and select from a variety of options – answer the call with the speaker enabled, ignore the call without a response or ignore the call with a pre-defined text message.

Wing Waves Can Generate Electricity

Scientists around the world are working to perfect technology for generating cost effective electricity from oceans and seas using wings waves. Stephen Wood, an assistant professor of marine and environment systems at the College of Engineering of Florida Institute of Technology is building up on the expertise available to exploit it in a more efficient way.

A set of wing waves, also called sea fans comprise two metal structures shaped like wings. The fans are installed on the floor of the sea. There are some basic requirements for putting up the wings. The sea bottom must be sandy and about 50 feet deep from the water surface. The metal wings must be resilient enough to withstand the constant buffeting of the waves around them. At the same time, they must be flexible so that they can flap back and forth along with the seawater’s swells. The constant motion of the wings is harnessed to produce electricity eventually by rotating a coil of an AC generator in a magnetic field.

The fans are trapezoid shaped with a height of 8 feet and a width of 15 feet. They are manufactured in plants near the ocean or sea to facilitate transportation.

Like wind turbines and windmills, wing wave technology makes for a greener option for production of electricity compared to that provided by thermal power plants using fossil fuels. Clean and Green Enterprise, a firm based in Tallahassee and dealing in renewable energy choices, originally conceived this technology. Terence Bolden, a chief executive of the firm explains that the ocean swells cause the fans to swing by as much as 30 degrees from on either side of their mid positions. The fans take about 10 seconds to complete each sweep. The mechanical energy produced by the wings is passed on to the generator coil. The coil rotates at great speed in a magnetic field to produce electric current.

Wood asserts that wings strategically placed in a square mile can generate close to 1000 units of electric power. This is adequate for lighting up 200,000 homes.

Apart from being an environmentally clean option for generating electric power, wing wave technology affords several other advantages. They can be operated in any seaside area. The fans are designed to perform when the sea is calm and the swells are moderate. When there is a storm and the sea is rough, an automatic locking system renders the fans inoperable. A reasonable level of maintenance ensures that they can be in operation for as long as 20 years. Unlike wind turbines, they do not spoil the natural beauty of coasts as they are submerged under water. The structures do not cause any harm to marine life. It is crucial however, that they are not placed near coral reefs.

The current prototype, installed on offshore Florida coast, is constructed with aluminum. The research group at the university uses it to collect data related to wave motion and other issues regarding power production. The team now plans to replace it with a version made from a composite material that will be less prone to corrosion.