The world of electronics and electronic interconnections is changing again, this time beyond the "smaller, faster, cheaper" issues of the past two decades. Today's landscape is more complex and reflects the sophistication of the new electronics solution set. Specifically, it involves: (A) increases in the use of higher frequencies due to the seemingly insatiable appetite for bandwidth, (B) reduced reflections that go along with the use of higher frequencies, and (C) a change in emphasis from high power to low loss.

The demand for bandwidth continues with no end in sight. The "killer application" for bandwidth, the internet, is pressing the industry for new higher capacity delivery systems. Data transmission via telephone technology has moved from 56k modems to ISDN and on to G-lite and XDSL technologies. The CATV industry is closing up HFC loops to enable high bandwidth data delivery to homes via cable modem. On the horizon, wireless approaches such as satellite and LMDS portend to crack the puzzle. All of these solutions involve the attendant problems of crosstalk, return loss, and attenuation.

Nowhere is the need for seamless interconnections more apparent than in the issue of matched impedance. Briefly, impedance mismatch is a significant source of return loss, or reflection. Designs that emphasize "controlled" impedance have resulted. In earlier times you could ignore the impedance mismatch of a connector if the length of the male-female pair was less than ¼ wavelength of the harmonic frequency. Now that "wanna-be" bandwidth needs in the 100 Mbps range are a reality, the corresponding frequency (assuming alternate mark inversion coding and the use of the 5thharmonic waveform for a rapid rise time "square" wave) is 2.5 GHz. At this frequency, the quarter wave interval is 0.4 inches, well within the physical geometry of a conventional connector.

The third issue is that of power versus loss, of particular importance in wireless applications. Traditional solutions in signal-to-noise ratios involve increased power. As wireless "cells" shrink to handle more traffic in a given area, the number of sites used to cover that area goes up and the result is a change to using lower power levels for signal acquisition and repeating. When power levels drop, the task of separating signal from background noise increasingly involves low loss characteristics. Low signal levels require low loss transmission lines to achieve the high signal-to-noise relationship.

These issues are not unrelated. Fundamentally, today's wire lines have become transmission lines. Since connectors are in-line with the rest of the transmission, they must perform with similar low loss characteristics. We are at the leading edge of a trend that may separate the "shapers" from the "participants" in the connector business. Take a hard look at your interconnect source. Ask questions about return loss levels of -20 dB or better (in fiber optic technology it should be -50dB or better). See if they know what VSWR means. Get on board with a "shaper" of technology and use your supplier base as enabling technology to service your customers. Your customers will appreciate your reliance on technology-rich solutions to address their performance issues, and you will achieve distinctive competence. The electronics business doesn't get better than this.

Credits: Dale Reed has been active in high frequency issues, particularly microwave printed circuit board design, for 12 years prior to joining Trompeter Electronics as VP Marketing in 1997. Trompeter manufactures and markets RF connectors in coax, triax, and twinax technologies for the military/aerospace, telephony, and broadcast markets worldwide. He can be reached at dale.reed@trompeter.com.