Featured Engineer

Interview with Charan Langton

Charan Langton

Charan Langton - Manager of Simulation and Analysis at Loral Space Systems

What are your favorite hardware tools that you use?

I like Sony computers, have two PCs on my desk with dual monitors. I started out as a Mac fanatic but had to move to PC because most of the engineering software switched to the PC platform. So now it is PC all the way. I also have in front of me an old (app. 1980) HP 11C hand held calculator, the one with the RPN notation. This little machine runs on its original battery! Most people find that hard to believe that a calculator can run for 30 years on the same battery. But I checked on the Internet and indeed there are others who have the same experience. That’s when HP was king.

What are your favorite software tools that you use?

For my communication simulation work, I use Synopsys’s SPW. I find it easier to use than most other communication systems simulation tools. I have used Matlab/Simulink, SystemView and ADS but at the end come back to SPW to do my work.

For non simulation work I like Matlab and MathCad. For graphics I bounce between Visio and SmartDraw. Neither seems to work perfectly for me. I keep hoping for a really nice graphics program designed for engineering work, but so far I have not found one. I am always upgrading and hoping for graphics Nirvana.

What is the hardest thing you have ever encountered?

One nice thing about communications is that things keep moving forward. New advances keep the field exciting. About ten years ago when Turbo codes and LDPC codes came out, I thought that was it, we have reached Shannon’s limit so what can be next. But like anything in life, the science of communications has many dimensions. Now we have MIMO to take things even further. In this field you have to keep learning. It won’t stay put. Looking back, I would say that understanding and coding the MAP algorithm used in Turbo Codes was probably the hardest thing I have done. But I am sure it won’t be the last. Each new topic seems difficult at first.

What is on your bookshelf?

Engineering comes across as a confounding science when it is not explained well. I am very impressed by engineering authors and professors who can teach engineering without pain. First in this category is the book “Digital Communication” by Bernard Sklar. Many years ago, I took Bernard’s class at Aerospace Corporation. His approach to teaching engineering with examples made the topic intuitive.

Next is “Understanding Digital Signal Processing” by Richard Lyons. I remember hating DSP in college, but Rich made the subject sing. After I read his book, I called him up and we have remained friends for the last 15 years. His book is a model of how good engineering books should be written. I credit him for inspiring me to write my Tutorials.

One recent book that is not as famous as the first two is “Adaptive Filters” by Ali Sayed. For a complex topic, this is a beautifully written book.

For fun I like to read scientific pop; “Prime Obsession” by Bernhard Riemann , “Fortune’s Formula: The Untold Story of the Scientific Betting System That Beat the Casinos and Wall Street” with an appearance by Claude Shannon, “Number: The Language of Science” by Tobias Dantzig.

Also a wonderful book on probability, “Chances Are: Adventures in Probability” by Michael Kaplan and Ellen Kaplan . And then there is my absolute favorite book by mathematician Paul Davies, “The Thread: A Mathematical Yarn”. He writes about traveling all over Europe to trace the correct spelling of Chebychev, of the filter fame. It seems no one agrees on the right way to spell it.

Then, a stock market book “More Than You Know: Finding Financial Wisdom in Unconventional Places” and lastly Boris Akunin’s mysteries. I bought a kindle as soon as it came out (the original) and carry around my 80 or so books, which I claim to be reading all at once.

What has been your favorite project?

I started writing my Tutorials in 1998. It took me so long to write the first tutorial that it seems a wonder that I have written over 24 of them on complextoreal.com. We learn by teaching so I can say that having myself as a student was the great. I feel richer for having written them. I no longer hate DSP. I receive emails from all over the world, it seems that I was able to inspire many to rediscover communications science or at least clear up some of the confusion.

When our kids were young we wrote a book, called The Reading Lesson, for teaching them to read. Lately I have been working on books to teach math verbally without worksheets. Being able to do math in your head is important and the skill is losing out to PCs. I hope my books on Verbal Math can help change that.

Do you have any note-worthy engineering experiences?

I was managing the Shuttle Integration of a satellite while I was at Aerospace Corporation. I used to go to Cape Canaveral for meeting, tests planning etc. At one point, when the satellite was being put in the Shuttle bay, the team was given a chance to take the elevator that looked like a wire cage to take a closer look. At the shuttle the safety Officer took one look at me and would not allow me to go up because 1) I was wearing heels and 2) I was wearing a skirt. I stopped wearing heels after that. I still wear skirts, however.

What are you currently working on?

I am co-writing a book with Bernard Sklar, most likely called “Modern Communications.” Writing engineering books is a very slow process. They don’t come out of inspiration. It feels more like homework.

What direction do you see your business heading in the next few years?

I have been in the satellite business for the last 30 years. I often hear of challengies to satellite systems from fiber, from the internet, from WAN and MAN. But satellites offer something no other channels do. The Satellite link is a pure clean line of sight, the best form of channel you can ask for. Hence, the pristine quality of the signals. BTW, the satellite dish systems deliver better quality signal than cable despite what anyone tells you! Commercial satellite broadcasting systems are here to stay. Satellite capacities are growing both from improved power supplies and also from advances in the communication sciences which now allow far higher bit rates through more bit efficient modulations such as 16APSK.

What challenges do you foresee in our industry?

Challenges have to do with keeping up with the fast advancing science of communications. Being able to build satellite systems that can transmit OFDM signals, 32APSK and other higher order modulations, perhaps even MIMO, is on the horizon.

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