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Issue: May 2010

Another Non-Answer On Mobile Phone Radiation

The debate over whether or not the radiation from mobile phones causes cancer has been raging for decades. Tens of millions of dollars and hundreds of studies later, the answer remains: "We don't know."

This was the overall finding from the Interphone study which was released May 18, the largest and most expensive epidemiological study of possible tumor risks associated with mobile phone use ever attempted. Research teams in 13 countries participated in the project coordinated by the International Agency for Research on Cancer (IARC) in Lyon, France.

"The overall conclusion of no increased risk is in accordance with the large body of existing research and many expert reviews that consistently conclude that there is no established health risk from radio signals that comply with international safety recommendations," said Jack Rowley, director of research for the telecoms companies' association GSMA.

The issue is as hotly-debated, politically-charged, and self-serving as any piece of Congressional legislation ever written. It pits industry interests and some academics against other academics. Without evidence that clearly shows a direct link between mobile phone use, cancer, changes in DNA structure, and other maladies, the issue remains contentious. Of course, the only real proof would come from studies in man, which would take decades.

Thus the Interphone results were predictable from Day One. The survey of nearly 13,000 participants found up to 40 % higher incidence of glioma brain tumors among the top 10% of people who used their mobile phone most (30 or more minutes per day. Time spent using handsfree devices was ignored because even a distance of 4 in. from the body reduces the amount of radiation to the brain nearly to zero. The highest risk found was for tumors on the same side of the head as users held their phone, particularly for tumors in the temporal lobe closest to the ear. However, the study also showed that casual users had a lower risk of getting cancer than people who didn't use cell phones at all, leading to the assumption that there were problems in the way studies were conducted.

So $30 million and thousands or hours of research later, the answer remains "we don't know."

Answers to last month's trivia questions  

1. What U.S. state is the eighth largest economic power in the world? California

2. What was an official language in 87 nations and territories, by 1994? English

3. What South Asian city is the planet's biggest feature film producer? Bombay

Greetings {FIRST_NAME},

A Message from Sam Benzacar

More Technical Content On the Way

When asked about his decision to add more and better editorial content to The Wall Street Journal's print and online editions, News Corp. founder Rupert Murdoch recently stated his belief that "content is not just king, it's the emperor of all things electronic." The result we've received from you as we have added more technical information to our newsletter clearly supports that philosophy. So from this issue forward we will be featuring one of more technical topic per month, in sufficient detail to help designer make decisions. This issue focuses on LC filters, and future issues will cover other filter types as well as various other components. We hope you find them useful. 

The Versatile LC Filter

The LC, or lumped element, filter) is perhaps the most common of all electromagnetic filter types. It takes its name from the inductors and capacitors upon which it is based. LC filters can be specified in lowpass, bandpass, bandstop, or highpass configurations and in diplexers and duplexers as well. They are useful over a frequency range of below 100 kHz to slightly above 3 GHz. Key parameters for specifying LC filters include insertion loss, stopband rejection, center frequency, cutoff frequency, bandwidth, Q factor, shape factor, and power handling ability. Table 1 provides the inherent advantages and disadvantages of LC filters.

In an LC filter, capacitors and inductors arranged in either series or parallel resonant circuits result in filters ranging in size from about 0.5 in. at high frequencies to 26 in. at low frequencies. The actual size of a particular LC filter is dictated by the size of these capacitors, inductors, as well as the level of RF power it must withstand.

At below 100 KHz the inductors, and capacitors are very large adding to the already labor intensive type of product.  On the other end of the spectrum the outcome is the opposite where the inductors and capacitors are extremely small, and depending on the specification might end up being impractical.

The performance of LC filters has increased over the years thanks to the development of ferrite materials used to manufacture inductors and the dielectric materials used in capacitors. As a result, high inductor Q factors can be achieved in smaller sizes than with earlier designs.

Anatech Electronics will be exhibiting at the 2010 IEEE MTT-S IMS show from May 25-27 in Anaheim, California at the Anaheim Convention Center.

Come Visit us at booth #1344!

If you would like to obtain a free pass please contact us!

If you have any questions regarding our products, or comments on our newsletter, please email us at: filters@anatechelectronics.com 

Featured Products

Bandpass Filter Serves VHF Applications

The AE164B6933 is a lumped-element bandpass filter that has a 164 MHz center frequency, 1-dB bandwidth of 160 to 168 MHz, insertion Loss of less than 3 dB, in-band ripple of less than 1 dB, return loss greater than 14 dB, and rejection from DC to 130 MHz and 200 MHz to 1 GHz greater than 60 dB. It measures 2.5 x 0.75 x 0.5 in. and has SMA female connectors.

This product is available from our Web store, AMCrf.com.

1706 MHz Lowpass Filter for L-Band Systems

The AE1706L8769 lumped-element lowpass filter has a cutoff frequency of 1706 MHz, insertion loss over its passband of less than 0.6 dB, return loss greater than 18 dB, rejection at 3300 MHz greater than 40 dB and greater than 65 dB at 4800 MHz. It is designed for surface-mount applications and measures 1.5 x 0.5 x 0.4 in.

This product is available from our Web store, AMCrf.com.

Broadband 3-Way Power Divider

The AM1700PD1341-N is a broadband three-way power divider that covers 700 to 2700 MHz with insertion loss less than 0.4 dB, VSWR less than 1.3:1, amplitude balance of 0.2 dB, phase balance of 3 deg., and power handling of 200 W. It has Type-N female connectors.

This product is available from our Web store, AMCrf.com.

10-dB Directional Coupler Covers 300 to 2000 MHz

The AM1150DC867 directional coupler covers 300 to 2700 MHz, with coupling of 10 dB, insertion loss of 0.7 dB, coupling flatness of 0.25 dB, VSWR of less than 1.25:1, and power handling of 50 W. It employs SMA female connectors.

This product is available from our Web store, AMCrf.com.

Trivia Questions 

1. What M-word did Texas citizens choose as a town name that would "attract" folks?

2. What country has been the planet's largest aid donor since 1991?

3. What interstate highway connects Boston and Seattle?

Look for the answers in next month's issue! 

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