LOSSES IN TRANSMISSION LINES

Copper Losses
One type of copper loss is I²R LOSS. In rf lines the resistance of the conductors is never equal to zero. Whenever current flows through one of these conductors, some energy is dissipated in the form of heat. This heat loss is a POWER LOSS. With copper braid, which has a resistance higher than solid tubing, this power loss is higher.
Another type of copper loss is due to SKIN EFFECT. When dc flows through a conductor, the movement of electrons through the conductor's cross section is uniform. The situation is somewhat different when ac is applied. The expanding and collapsing fields about each electron encircle other electrons. This phenomenon, called SELF INDUCTION, retards the movement of the encircled electrons. The flux density at the center is so great that electron movement at this point is reduced. As frequency is increased, the opposition to the flow of current in the center of the wire increases. Current in the center of the wire becomes smaller and most of the electron flow is on the wire surface. When the frequency applied is 100 megahertz or higher, the electron movement in the center is so small that the center of the wire could be removed without any noticeable effect on current. You should be able to see that the effective cross-sectional area decreases as the frequency increases. Since resistance is inversely proportional to the cross-sectional area, the resistance will increase as the frequency is increased. Also, since power loss increases as resistance increases, power losses increase with an increase in frequency because of skin effect.
Copper losses can be minimized and conductivity increased in an rf line by plating the line with silver. Since silver is a better conductor than copper, most of the current will flow through the silver layer. The tubing then serves primarily as a mechanical support.


Dielectric Losses
DIELECTRIC LOSSES result from the heating effect on the dielectric material between the conductors. Power from the source is used in heating the dielectric. The heat produced is dissipated into the surrounding medium. When there is no potential difference between two conductors, the atoms in the dielectric material between them are normal and the orbits of the electrons are circular. When there is a potential difference between two conductors, the orbits of the electrons change. The excessive negative charge on one conductor repels electrons on the dielectric toward the positive conductor and thus distorts the orbits of the electrons. A change in the path of electrons requires more energy, introducing a power loss.
The atomic structure of rubber is more difficult to distort than the structure of some other dielectric materials. The atoms of materials, such as polyethylene, distort easily. Therefore, polyethylene is often used as a dielectric because less power is consumed when its electron orbits are distorted.


Radiation and Induction Losses
RADIATION and INDUCTION LOSSES are similar in that both are caused by the fields surrounding the conductors. Induction losses occur when the electromagnetic field about a conductor cuts through any nearby metallic object and a current is induced in that object. As a result, power is dissipated in the object and is lost.
Radiation losses occur because some magnetic lines of force about a conductor do not return to the conductor when the cycle alternates. These lines of force are projected into space as radiation and this results in power losses. That is, power is supplied by the source, but is not available to the load.

SPECIFYING OR DESIGNING RADIATED MEASUREMENT SYSTEMS

When specifying or designing any measurement receiver system, one should consider that the "system" will include other devices such as antennas, amplifiers, cabling, and possibly filters.Because a receiver's selectivity, the ability to select frequencies or frequency bands, is primarily a function of the receiver's tuner design, and will be chiefly dependent on the individual receiver selection, selectivity will not be specifically addressed in this text. Receiver system

sensitivity, however, presents one of the greatest difficulties, or

challenges, when designing or specifying receiver measurement systems. Therefore, the sensitivity of the two basic types of receiver systems,

one with a pre-amplifier and one without a pre-amplifier, will be addressed in some detail.

Because antennas are not perfect devices and have associated "losses," the following examples will include explanations for these error corrections. As mentioned previously, amplifiers will not only amplify the emissions being measured but they will  also amplify ambient electromagnetic noise. These ambient conditions can drastically change the overall sensitivity of a measurement system. Another potential problem associated with using amplifiers is that they also generate internal electromagnetic noise. Being active devices they will introduce their own internal electromagnetic noise into the receiver system, again having an influence on the total system's noise level, thus, its sensitivity. Some corrections for the above mentioned problems are necessary to accurately calculate both the receiver's signal input sensitivity and (more importantly) the total system's ambient

sensitivity. Without knowing the total measurement system's ambient sensitivity, measurements may not be possible down to anticipated emission levels. In electromagnetic measurement systems terms such as ambient sensitivity, system sensitivity, and receiver sensitivity have been used interchangeably.

More confusing expressions commonly used are terms such as "receiver noise floor," or "system noise floor."

THE RECEIVER AND AMPLIFIER

A receiver is an electro-mechanical device that receives electromagnetic energy captured by the antenna and then processes (extracts) the information, or data, contained in the "signal." The basic function of all receivers is the same regardless of their specific design intentions, broadcast radio receivers receive and reproduce commercial broadcast programming, and likewise, TV receivers detect and reproduce commercial television broadcasting  Programming. Special, or unique, receivers are sometimes needed to detect and measure all types of radiated, or transmitted, electromagnetic emissions. These specialized receivers may be called tuned receivers, field intensity meters (FIMs), or spectrum analyzers.

Radiated emissions that receiver systems may be required to measure can be generated from intentional radiators or unintentional radiators. The information contained in intentionally radiated signals may contain analog information, such as audio, or they may contain digital data, such as radio navigation beacon transmissions. Television transmissions, for example, contain both analog and digital information. This information is placed in the transmitted emission, called the "carrier," by a process called "modulation." Again, there are many different types of modulation, the most common being amplitude modulation (AM) and frequency modulation (FM). Receivers detect, or extract, the information/data from radiated emissions by a process called "demodulation", the reverse of modulation.

Many radiated emissions requiring measurements do not contain any useful information or data at all. As an example, radiated emissions from unintentional radiators, such as computer systems, are essentially undesired byproducts of electronic systems and serve no desired or useful purpose. These undesired emissions can, however, cause interference to communications system, and if strong enough, they can cause interference to other unintentional radiating devices. Radiated signals (if strong enough) can also present possible health hazards to humans and animals. Because these emissions must be measured to determine any potential interference problems or health hazard risks, specialized receiver systems must be used.

An important parameter for any receiver is its noise figure, or noise factor. This parameter will basically define the sensitivity that can be achieved with a particular receiver.

An amplifier, usually called a pre-amplifier, is sometimes required when attempting to measure very small signals or emission levels. Because these devices amplify signals, they will also amplify ambient electromagnetic noise. If improperly used, amplifiers can detract from the overall system's sensitivity as well as possibly causing overloading to the receiver's tuner input stage. Overloading a tuner's input stage is simply supplying a larger signal amplitude than the receiver's tuner input circuitry is capable of handling, thus, saturating the tuner's input stage.

THE ANTENNA

Measuring radiated emissions, or electromagnetic energy, begins with the antenna. Antennas are devices that receive (capture) electromagnetic energy traveling through space. Antennas can also be used for transmitting electromagnetic energy. There are many different types of antennas, some are designed to be "broad-banded," to receive or transmit over a large frequency range, and some are designed to receive or transmit at specific frequencies. In any case, all receive antennas are intended to capture "off-air"electromagnetic energy and to deliver these "signals" to a receiver. For this discussion, electric fields (E) will mainly be addressed.

Because antennas can only capture a small portion of the radiated power, or energy, a correction factor must be added to the detected emission levels to accurately determine the radiated power being measured. The actual power received by an antenna is determined by multiplying the

power density of the emission by the receiving area of the antenna, Ae. This antenna correction factor is called the "antenna factor."

Cutting Costs Sees an Increase in Profits for Dell

Good news recently came out of Dell as the computer company reported that its net income for the last quarter nearly tripled as Dell benefited from lower computer component costs and growth in certain areas of its more profitable product lines.

Dell's shares rose 5% in extended trading, beating analysts' adjusted net income estimates but coming a bit short of revenue estimates. For Dell's first three months, which ended on April 29th, Dell earned $945 million, which equals about $0.49 per share, which was higher than the $341 million, $0.17 per share of last year.

If you exclude one-time items, Dell earned $0.55 per share which easily beat the numbers expected by Wall Street. Analysts polled by FactSet estimated adjusted earnings of $0.43 per share. Revenue rose only 1% to $15.02 billion from $14.9 billion last year, which was short of the predicted $15.4 billion. Product revenue remained the same at $12.1 billion with services revenue rising 6% to $3.0 billion.

Dell's consumer section, which accounts for nearly 20% of the company's revenue, dropped 7% to $3.0 billion as well. Consumer demand also fell more than anticipated and in an interview, CFO Brian Gladden attributed some of the cause to "the market for consumer PCs being saturated in developed countries." He also added that "while tablet computers are still a small portion of the PC market, there's clearly an impact for them on consumer demand for traditional PCs."

Revenue from large enterprises increased by 5% to $4.5 billion with revenue from small and medium-sized businesses increasing 7% to $3.8 billion. Public sector revenue, on the other hand, saw a decline of 2% to $3.8 billion. Dell saw the biggest gain in servers and networking. In this category revenue rose 11% to $2.0 billion. Sales of desktop PCs fell 8% to $3.3 billion with mobile PCs rising 3% to $4.7 billion.

Dell has been working hard to increase their proportion of server computers, data storage devices and technology consulting services sold. According to Dell, these areas are more profitable than the company's base PC business. However, compared with one year ago, most of Dell's product categories accounted for nearly the same percentage of revenue and computers for consumers, and businesses continued to make up over half of Dell's revenue.

However, Dell's gross margin, which is still an indicator of the efficiency of Dell's business, came in at 22.9% which was higher than the 20.4% expected by analysts from Reuters. Dell's strategy of focusing on more profitable areas of business and cutting back on lower-margin offerings is working extremely well according to Gladden.

Andy Hargreaves, an analyst for Pacific Crest, thinks that Dell's gross margin is "impressive" and stated that "Dell should be able to keep it up for now." Hargreaves also stated, "They do have the potential to sustain margins long-term, but in order to do so they have to drive toward more services-oriented businesses."

Taking a look at this current quarter, Dell is predicting that revenue will rise by a percentage in the mid-single digits over the first quarter, slightly faster than its seasonal 2% to 3% growth. Analysts are expecting somewhere around $16 billion. Dell continues to expect revenue to grow 5% to 9% for the full fiscal year which implies a total of $64.6 billion to $67 billion with analysts expecting around $64.4 billion.

Dell saw shares rise $0.86, or roughly 5.4%, to a total of $16.76 in extended trading. The stock finished regular trading down $0.10 to $15.90.

PayPal's Peter Thiel Pays Students to Skip College

Senior year is stressful for a lot of students. Most are concentrated on getting good grades and academic honors so they can get into a good college and have a better life some day. A lot of students do a lot of hard work in order to earn money to go to college. However, two dozen students from around the country will, instead of going to college, be paid to not go to school.

That's right, 24 gifted technical students from around the country will each be given a $100,000 scholarship by San Francisco tech tycoon Peter Thiel with a little catch, that they do not go to college this coming fall. Instead of going to school, these students are receiving the $100,000 so they can chase their dreams for the next two years.

"It seems like the perfect point in our lives to pursue this kind of project," stated Nick Cammarata, a gifted computer programmer who recently got accepted into the esteemed computer science program at Carnegie Mellon's University. He, along with 17-year-old David Merfield, will be working on software designed to upend the standard approach to high school teaching. Merfield is turning down an opportunity to attend Princeton University in order to participate in the scholarship.

Each applicant for the scholarship was asked to design a project to change the world. Thiel personally hand-picked the winners based on these projects. While all the ideas span different disciplines, they all have a high technology angle to them. According to Thiel, "One winner wants to create a mobile banking system for the developing world. Another is working to create cheaper biofuels. One wants to build robots that can help around the house."

This scholarship could not have come at a more interesting, and quite possibly crucial time as the debate over higher education's value is becoming quite heated. There are thousands of new graduates who are swimming in student loan debts and are encountering one of the hardest job markets in decades. Many people are pondering whether or not a college education is worth it given the rising tuitions and diminishing prospects.

"Turning people into debt slaves when they're in college students is really not how we end up building a better society," Thiel added. Thiel made his fortune as co-founder of PayPal shortly after graduating from Stanford Law School. After that he became the first major investor in Facebook. Thiel is adamant in his belief that innovation has become stagnant in the United States and that radical solutions are needed to push civilization forward.

One such effort is the "20 Under 20" fellowship. Thiel believes that the brightest young minds are able to contribute more to society by skipping college and bringing their ideas to the real world right away. However, not everyone can be as fortunate as Thiel and Mark Zuckerberg of Facebook.

Director of Research at Duke University's Center for Entrepreneurship Vivek Wadhwa doesn't agree with Thiel and sees his new program as sending a message that anybody can be Mark Zuckerberg. "Silicon Valley lives in its own bubble. It sees the world through its own prism. Its got a distorted view," Wadhwa stated.

Wadhwa also added, "All the people who are making a fuss are highly educated. They're rich themselves. They've achieved success because of their education. There's no way in hell we would have heard about Peter Thiel if he hadn't graduated from Stanford."

Thiel retorted that the "20 Under 20" should not be judged on the basis of his own education background or the merits of his critique on higher education. Thiel has urged critics to wait and see what these individuals achieve over the next two years.

Studies from the past few years have noted that individuals who received a college degree were laid off during the "Great Recession" at a much lower rate than individuals without college degrees. In addition to that, individuals with college degrees were also more likely to be rehired.

Could this be a new revolution in higher education? Or will the world push these students, as well as their ideas, away due to their lack of college education?

Lockheed-Martin Purchases D-Wave's First Quantum Computer

D-Wave out of Canada has just sold the first of its commercial quantum computers and they sold it to Lockheed-Martin. However, it wasn't as easy as your average sale. Despite the fact that D-Wave managed to make the sale, the company had to do it despite a debate over whether it truly was a quantum computer.

Back in February 2007 D-Wave demonstrated a machine that could solve problems regular computers are incapable of solving, in principle that is. The reason it is only in principle is because the tests run on the computer were not impossible on a regular computer. This created a fair bit of doubt among some that the chip was actually performing quantum-mechanical computations.

The computer works differently than the regular "gate model" of quantum computing where a series of quantum bits can be encoded as either 0, 1 or both simultaneously. D-Wave's machine uses something researchers are calling "adiabatic quantum computing" or "quantum annealing". However, some people disagree that this process is actually, truly quantum computing.

But despite all this, Lockheed-Martin wasn't turned away. The company just recently signed a deal with D-Wave to purchase a quantum computer for an estimated $10 million. This agreement will span multiple years and include system maintenance as well as various other professional services.

As of right now, it is unclear what Lockheed-Martin plans on doing with the computer. However, according to D-Wave's President and CEO Vern Brownell, "Our combined strength will provide capacity for innovation needed to tackle important unresolved computational problems of today and tomorrow. Our relationship will allow us to significantly advance the potential of quantum computing."

This is the second biggest deal the company has signed in the past couple of years with the biggest being a tie-up with Google in order to improve image search algorithms. Despite the fact that D-Wave's technology has not been 100% proven, Lockheed-Martin has still seen it as worthy of a $10 million investment. If anything, it gives them first access to this kind of technology.