2.4-GHz RF High-Power Amplifier


The SST12CP12 high-power amplifier

The SST12CP12 is a 2.4-GHz RF high-power amplifier that adds support for 256-QAM ultra-high data rate modulation. With its high linear output power, this amplifier significantly extends the range of IEEE 802.11b/g/n WLAN systems while providing excellent power at the maximum 256-QAM data rate. The amplifier is also spectrum-mask compliant up to 28.5 dBm for 802.11b/g communication and utilizes orthogonal frequency-division multiplexing (OFDM) to correct severe channel conditions without using complex equalization filters.

The SST12CP12 power amplifier has a 380mA at 23 dBm low operating current, which enables more transmission channels and a higher data rate for each system. The amplifier also features easy to use 50-Ω on-chip input match and simple output match. In addition, the integrated linear power detector provides temperature stability and immunity to voltage standing wave ratio (VSWR) radio-wave reflection to provide accurate output power control.

The SST12CP12 costs $0.97 each, in 10,000-unit quantities. It ships in a 3-mm × 3-mm × 0.55-mm, 16-pin QFN package.

Microchip Technology, Inc.

Q&A: Alenka Zajić, Communications Specialist

From building RF components for cell phones to teaching signal processing and electromagnetics at Georgia Institute of Technology’s School of Electrical and Computer Engineering, Alenka Zajić has always been interested in engineering and communications. Alenka and I discussed her fascination with a variety of communication technologies including mobile-to-mobile, computer system, energy-efficient, and wireless. She also described her current research, which focuses on improving computer communication.

Alenka Zajić

Alenka Zajić

NAN: Give us some background information. Where are you located? Where and what did you study?

ALENKA: I am originally from Belgrade, Serbia, where I got my BS and MS degrees at the School of Electrical Engineering, University of Belgrade.

After graduating with a BS degree, I was offered a design engineer job at Skyworks Solutions in Fremont, CA, where my job was to create passive RF components (e.g., antennas, filters, diplexers, baluns, etc.) for cell phones.

I was very excited to move to California, but was not sure if I would like to pursue an engineering career or a research/academic career. Since it took about six months to get an H1B visa, I decided to take all the required MS courses in Belgrade while waiting for the visa and all I had to do was finish the thesis while working in California. It was a bigger challenge than I expected, but it worked out well in the end.

While I enjoyed working in the industry, I was always more drawn to research than commercialization of products/innovations. I also enjoy “trying something new,” so it became clear to me that I should go back to school to complete my doctoral studies. Hence, I moved to Atlanta, GA, and got my PhD at the School of Electrical and Computer Engineering, Georgia Institute of Technology.

After graduation, I worked as a researcher in the Naval Research Laboratory (Washington, DC) and as a visiting assistant professor in the School of Computer Science, Georgia Tech, until last year, when I became the assistant professor at the School of Electrical and Computer Engineering, Georgia Tech.

NAN: How long have you been teaching at Georgia Tech? What courses do you currently teach and what do you enjoy most about teaching?

ALENKA: This is my second year at the School of Electrical and Computer Engineering. Last year, I taught introduction to signal processing and electromagnetics for undergraduates. This year, I am teaching electromagnetics for graduate students. One of the most rewarding aspects of university teaching is the opportunity to interact with students inside and outside of the classroom.

NAN: As an engineering professor, you have some insight into what interests future engineers. What are some “hot topics” that intrigue your students?

ALENKA: Over the years, I have seen different areas of electrical and computer engineering being “hot topics.” Currently, embedded programming is definitely popular because of the cell phone applications. Optical communications and bioengineering are also very popular.

NAN: You have contributed to several publications and industry journals, written papers for symposiums, and authored a book, Mobile-to-Mobile Wireless Channels. A central theme is mobile-to-mobile applications. Tell us what fascinates you about this topic.

ALENKA: Mobile communications are rapidly becoming the communications in most people’s minds because they provide the ability to connect people anywhere and at any time, even on the move. While present-day mobile communications systems can be classified as “fixed-to-mobile” because they enable mobility only on one end (e.g., the mobile phone) while the other end (e.g., the base station) is immobile, emerging mobile-to-mobile (M-to-M) communications systems enable mobile users or vehicles to directly communicate with each other.

The driving force behind M-to-M communications is consumer demand for better coverage and quality of service (e.g., in rural areas where base stations or access points are sparse or not present or in disaster-struck areas where the fixed infrastructure is absent), as well as increased mobility support, location-based services, and energy-efficient communication (e.g., for cars moving in opposite directions on a highway that exchange information about traffic conditions ahead, or when mobile devices “gang together” to reach a far-away base station without each of them expending a lot of power).

Although M-to-M is still a relatively young technology, it is already finding its way into wireless standards (e.g., IEEE 802.22 for cognitive radio, IEEE 802.11p for intelligent transportation systems, IEEE 802.16 for WiMAX systems, etc.).

Propagation in M-to-M wireless channels is different from traditional fixed-to-mobile channels. The quality of service, energy efficiency, mobility support, and other advantages of M-to-M communication all depend on having good models of the M-to-M propagation channels.

My research is focused on studying propagation and enabling communication in challenging environments (e.g., vehicle-to-vehicle wireless radio communications, underwater vehicle-to-underwater vehicle acoustic communications, and inside a processor chip). In each of these projects, my work aims not only to improve existing functionality, but also to provide highly useful functionality that has not existed before. Examples of such functionality include navigating people in a direction that will restore (or improve) their connection, voice, or even video between submerged vehicles (e.g., for underwater well-service operations), and use of on-chip transmission lines and antennas to achieve broadcast-type communication that is no longer feasible using traditional wires.

NAN: Your research interests include electromagnetics and computer system and wireless communications. How have your interests evolved?

ALENKA: My research was mostly focused on electromagnetics and its impact on wireless communications until I joined the School of Computer Science at Georgia Tech. Talking to my Computer Science colleagues, I have realized that some of the techniques developed for telecommunications can be modified to improve communication among processors, memory, racks in data centers, and so forth. Hence, I started investigating the problem of improving communication among computers.

NAN: What types of projects are you currently working on?


Two of Alenka Zajić's currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

Two of Alenka Zajićs currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

ALENKA: I have several projects and they all include theoretical and experimental work. Two of my current projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems. I will provide a brief explanation of each project.

Energy-efficient underwater acoustic communications: Many scientific, defense, and safety endeavors require communications between untethered submerged devices and/or vehicles.

Examples include sensor networks for seismic monitoring, analysis of resource deposits, oceanographic and environmental studies, tactical surveillance, and so forth, as well as communications between unmanned or autonomous underwater vehicles (UUVs, AUVs) for deep-water construction, repairs, scientific or resource exploration, defense applications, and so forth. Such underwater sensing and vehicular applications will require energy-efficient underwater communications, because underwater sensor networks and AUVs are highly energy-constrained. They are typically powered by batteries that are very difficult to replace or recharge deep underwater. At the same time, existing wireless communication approaches still provide extremely low data rates, work over very limited distances, and have low energy efficiency. Radio signals and wireless optics have a very limited range underwater, so underwater wireless communications mostly rely on acoustic signals that can travel long distances in water.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Unfortunately, acoustic underwater communications have a narrow available spectrum—propagation delays that are orders-of-magnitude longer than in radio communications—and many sources of signal distortion that further reduce data rates and increase the required transmitted power when using simple modulations and coding. Hence, we are working on characterization of underwater acoustic channels and their implications for underwater-vehicle-to-underwater-vehicle communications and networking.

Electromagnetic side channels in high-performance processors and systems: Security of many computer systems relies on the basic assumption that data theft through unauthorized physical tampering with the system is difficult and easily detected, even when attackers are in physical proximity to systems (e.g., desktops in cubicles, laptops and smartphones used in public spaces, remote data centers used for cloud computing, remotely operated robotic vehicles, aircraft, etc.).

On the other hand, the motivation for attackers keeps expanding. Increasing use of electronic banking provides monetary incentives for successful attacks, while the trend toward computer-controlled everything (e.g., power plants, robotic weapons, etc.) can motivate terrorists and/or rogue states.

Although simple physical attacks (e.g., stealing the system or taking it apart to insert snooping devices) are relatively hard to carry out without significant risk of detection, more sophisticated physical attacks are likely to be explored by attackers as incentives for such attacks grow. Side-channel attacks are especially worrisome, because they circumvent traditional protection measures.

Most side-channel attacks (e.g., power analysis, timing analysis, or cache-based attacks) still require some degree of direct access (i.e., to attach probes, run processes, etc.) that exposes attackers to a significant risk of detection. However, attacks that exploit electromagnetic emanations from the system only require physical proximity. So, increasingly motivated attackers may be able to carry out numerous attacks completely undetected, and several other side channels (e.g., power, timing, memory use, etc.) can “spill over” into the electromagnetic side channel, turning electromagnetic emanations into a very information-rich side channel.

My work in this domain focuses on carrying out a systematic investigation of electromagnetic side channel data leakage, quantifying the extent of the threat, and providing useful insights for computer designers to minimize such leakage.

NAN: Is there a particular electronics engineer or academic who has inspired the type of work you do today?

ALENKA: I have been fortunate to have great mentors (Dr. Antonije Djordjević and Dr. Gordon Stüber) who taught me the importance of critical thinking, asking the right questions in problem-solving, and clearly and concisely stating my ideas and results.

ISM Basics (EE Tip #100)

The industrial, scientific, and medical (ISM) bands are radio frequency ranges freely available for industrial, scientific and medical applications, although there are also many devices aimed at private users that operate in these bands. ISM devices require only general type approval and no individual testing.

Source: Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

Source: Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

The radio communication sector of the International Telecommunication Union (ITUR) defines the ISM bands at an international level. Wi-Fi and Bluetooth operate in ISM bands, as do many radio headphones and remote cameras, although these are not usually described as ISM devices. These devices are responsible for considerable radio communications interference (especially at 433 MHz and at 2.4 GHz).

ITU-R defines the following bands, not all of which are available in every country:

  • 6.765 to 6.795 MHz
  • 13.553 to 13.567 MHz
  • 26.957 to 27.283 MHz
  • 40.66 to 40.70 MHz
  • 433.05 to 434.79 MHz
  • 902 to 928 MHz
  • 2.400 to 2.500 GHz
  • 5.725 to 5.875 GHz
  • 24 to 24.25 GHz

Some countries allocate further ISM bands in addition to those above. ISM applications have the lowest priority within any given band. Many bands available for ISM are shared with other spectrum users: for example the 433 MHz ISM band is shared with 70 cm amateur radio communications.

ISM users must not interfere with other users, but must be able to tolerate the interference to their own communications caused by higher-priority users in the same band. The band from 868 MHz to 870 MHz is often mistakenly characterized as an ISM band. It is nevertheless available to short-range radio devices, such as RFID tags, remote switches, remote alarm systems, and radio modules.

For more information, refer to Wolfgang Rudolph & Burkhard Kainka’s article, “ATM18 on the Air,” 080852, Elektor, 1/2009.

Issue 265: Embedded Systems Abound

I recently read on CNN.com the transcript of an interview (May 9, 2002) with arachnologist Norman Platnick who stated: “You’re probably within seven or eight feet of spider no matter where you are. The only place on earth that has no spiders at all—as far as we know—is Antarctica.” It didn’t take long for me to start thinking about embedded systems and my proximity to them. Is the average person always within several feet of embedded systems? Probably not. But what about 50% or 60% of the time? E-mail me your thoughts.

Circuit Cellar 265, August 2012 - Embedded Development

Embedded systems are becoming ubiquitous. They’re in vehicles, mobile electronics, toys, industrial applications, home appliances, and more. If you’re indoors, the temperature is likely monitored and controlled by an embedded system. When you’re engaged in outdoor activities (e.g., hiking, golfing, biking, or boating), you probably have a few MCU-controlled devices nearby, such as cell phones, rangefinders, pedometers, and navigation systems. This month we present articles about how embedded systems work, and our authors also provide valuable insight about topics ranging from concurrency to project development.

Freescale’s Mark Pedley kicks off the issue with a revealing article about a tilt-compensating electronic compass (p. 16). Now you can add an e-compass to your next MCU-based project.

E-compass technology (Source: M. Pedley, CC265)

Turn to page 24 for an in-depth interview with Italy-based engineer Guido Ottaviani. His fascination with electronics engineering, and robotics in particular, will inspire you.

Have you ever come across a product that you know you could have designed better? Scott Weber had that experience and then acted on his impulse to build a more effective system. He created an MCU-based light controller (p. 32).

The MCU-based light controller is on the right (Source: S. Weber, CC265)

If you want to ensure a microcontroller works efficiently within one of your systems, you should get to know it inside and out. Shlomo Engelberg examines the internal structure of an I/O pin with a pull-up resistor (p. 40).

Bob Japenga continues his series “Concurrency in Embedded Systems” on page 44. He covers atomicity and time of check to time of use (TOCTTOU).

On page 48 George Novacek presents the second part of his series on project development. He covers project milestones and design reviews.

Ed Nisley’s June 2012 article introduced the topic of MOSFET channel resistance. On page 52 he covers his Arduino-based MOSFET tester circuitry and provides test results.

The MOSFET tester PCB hides the Arduino that runs the control program and communicates through the USB cable on the left edge. (Source: E. Nisley, CC265)

If you read Robert Lacoste’s June 2012 article, you now understand the basics of frequency mixers. This month he presents high-level design methods and tools (p. 58).

Jeff Bachiochi wraps up the issue with an examination of a popular topic—energy harvesting (p. 68). He covers PV cell technology, maximum power point tracking (MPPT), and charge management control.

A great way to investigate MPPT for your design is to use an STMicroelectronics evaluation board, such as this STEVAL-ISV006V2 shown in the top of the photo. The smaller cell in the center is rated at 165 mW (0.55-V output at 0.3 A) measuring 1.5” × 0.75”. At the bottom is a Parallax commercial-quality solar cell that is rated at 2.65 W (0.534-V output at 5.34 A) measuring 125 mm. (Source: J. Bachiochi, CC265)

Circuit Cellar 265 is currently on newsstands.

Elektor RF & Microwave App for Android

Elektor has an iPhone/iPad app for several months. And now Android users can have an Elektor app of their own. The Elektor RF & Microwave Toolbox app is perfect for engineers and RF technicians who need easy, reliable access to essential equations, converters, calculators, and tools.

A screenshot of the Elektor RF & Microwave app for Android

The app includes the following handy tools:

1.Noise floor (Kelvin,dBm)
2.Amplifier cascade (NF, Gain, P1db, OIP2, OIP3)
3.Radar equation (2-way path loss)
4.Radio equation (1-way path loss)
5.Power and voltage converter (W,dBm,V,dBµV)
6.Field intensity and power density converter (W/m2, V/m, A/m, Tesla, Gauss,dBm, W)
7.Mismatch error limits (VSWR, Return loss)
8.Reflectometer (VSWR, Return loss)
9.Mitered Bend
10.Divider and Couplers (Wilkinson, Rat race, Branchline , microstrip and lumped)
11.Balanced and und balanced PI and T attenuator
12.Skin depth (DC and AC resistance)
13.PCB Trace calculator (impedance/dimensions)
14.Image rejection (amplitude and phase imbalance)
15.Mixer harmonics (up and down conversion)
16.Helical antenna
17.Peak to RMS (peak, RMS, average, CF)
18.Air Core Inductor Inductance
19.Parallel plate Capacitor
20.PI and T attenuator
21.Ohm’s Law
22.Parallel LCR impedance/resonance
23.Series LCR impedance/resonance
24.Inductor impedance
25.Capacitance impedance
26.Antenna temperature (Kelvin)
27.Radar Cross Section (RCS) calculator (Sphere,Cylinder, flat plate, corners, dBsm)
28.Noise Figure Y-Factor Method
29.EMC (EIRP, ERP, dBµV/m)
30.Noise figure converter (dB, linear, Kelvin)
31.Frequency Band Designations
32.Resistor color code (reverse lookup, 3 to 6 band)
33.Filter Design (Butterworth, Chebyshev, prototype):
34.µ-Filter Design (microstrip, stripline)
35.PCB Trace Width and Clearance Calculator

Visit the Android Market for more information about the Elektor app.

Circuit Cellar does not yet have an app for Android. The Circuit Cellar iPhone/iPad app is available on iTunes.

Screenshots of the Circuit Cellar app

Elektor International Media is the parent company of Circuit Cellar.

RFI Bypasssing

With GPS technology and audio radio interfaces on his personal fleet of bikes, Circuit Cellar columnist Ed Nisley’s family can communicate to each other while sending GPS location data via an automatic packet reporting system (APRS) network. In his February 2012 article, Ed describes a project for which he used a KG-UV3D radio interface rigged with SMD capacitors to suppress RF energy. He covers topics such as test-fixture measurements on isolated capacitors and bypassing beyond VHF.

Photo 2 from the Febuary article, "RFI Bypassing (Part 1)." A pair of axial-lead resistors isolate the tracking generator and spectrum analyzer from the components under test. The 47-Ω SMD resistor, standing upright just to the right of the resistor lead junction, forms an almost perfect terminator. (Source: Ed Nisley CC259)

Ed writes:

Repeatable and dependable measurements require a solid test fixture. Although the collection of parts in Photo 2 may look like a kludge, it’s an exemplar of the “ugly construction” technique that’s actually a good way to build RF circuits. “Some Thoughts on Breadboarding,” by Wes Hayword, W7ZOI, gives details and suggestions for constructing RF projects above a solid printed circuit board (PCB) ground plane.

You can read this article now in Circuit Cellar 259. If you aren’t a subscriber, you can purchase a copy of the issue here.