Microwave Journal
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Making the Connection at EDI CON 2013

March 14, 2013

The Connectivity Workshop and Expert Panel, to be held as a special event within the Electronic Design Innovation Conference (EDI CON 2013) in Beijing this month, will give Chinese RF/microwave engineers an opportunity to learn about various cable, connector and cable assembly technologies in the context of overall high frequency electronic component designand system integration. The combined workshop and panel session will feature individual presentations from some of the world’s leading cable/connector vendors followed by a group panel discussion on the capabilities of today’s RF, microwave and high-speedinterconnects and the challenges of the systems they support.

Speakers from Mitron, Insulated Wire (IW), Times Microwave, Maury Microwave and Southwest Microwave will present various connector technologies and their corresponding electrical and mechanicalcharacteristics. These talks will concentrate on connector performance, examine how cable/connector attributes align to high-frequency application requirements and guide engineers who require help in selecting the appropriate interconnect solutions for the systems and instrumentation equipment they are developing.

Some of the Challenges

Cables are often the last detail considered during system designs and yet as a ubiquitous component in the signal path of any communication system, their performance is critical to the overall health and performance of the system. The ideal cable system must consider factors such as weight, durability, performance and cost. To avoid being the source of a failure, interconnect systems must be engineered to last the life of the product in any environment. Today’s cable systems are increasingly being used in hostile environments, exposed to extreme temperatures, chemicals, abrasion and extensive flexing. Meanwhile, today’s high-frequency applications call for smaller, lighter packaging, that last longer and cost less, especially in satellite communications and navigation systems.

To help workshop attendees better understand how to select the best connector/cable for their application, workshop presenters will discuss the constraints that affect performance, including electrical, mechanical, environmental, and application-specific factors. Presenters will share information regarding the materials and construction used in their cable/connector products, emphasizing the engineering and manufacturing technology behind achieving specific performance requirements. Attendees will learn howmanufacturers use testing and data analysis to qualify their existing products and enhance future ones.

Performance Criteria

Electrical performance is often the leading consideration in cable/connector selection. The workshop presenters will discuss the various ways in which cables may impact signal integrity and thus the overall system performance including impedance mismatch (VSWR), which lead to reflections of microwave energy between modules and devices (reducing signal strength and power added efficiency), insertion loss, which ultimately determines the maximum length of a signal cable, electromagnetic interference (EMI) and crosstalk, which results from unwanted coupling of signals between two transmission circuits.

While the electrical performance may be reliable under ideal conditions, environmental factors such as temperature can play a significant role in impacting how connectors behave in the real-world. For instance, the electrical properties of the material used to support the inner connector ofa coaxial cable is subject to change with temperature and mechanical stress. Presenters will discuss this phenomenon, known as the “Teflon-knee,” and its impact on phase stability over temperature. The workshop will also consider the impact of mechanical stress when cable systems operating at high speeds in tight spaces are exposed to movement, such as in handheld devices or automation and aerospace applications. Random, rolling and torsion type motion can cause severe damage if not properly managed. Presenters will discuss some of the real-world problems that can degrade performance, how to avoid such mishaps through installment best practices and/or better cable selection.

Environmental stress will have a different impact on performance depending on wherecables are used and exposed. Extreme temperatures affect cable materials, with low temperatures making them brittle while high temperatures will cause them to become very soft. Like extreme temperatures, extreme pressures can also have a significant impact on cables. Cables operating in a vacuum may leach oils and additives, which could lead to contamination of a work surface such as a clean manufacturing process for semiconductor chips. Conversely, hydrostatic pressure causes gas or liquids to permeate insulation or cable jackets and can destroy some cable materials. Workshop presenters will look at how these environmental factors and others can significantly shorten the life of a cable, and how to factor such considerations into designing a cable system with the proper technology.

Handling Tips

RF cable assemblies are designed to operate at the highest electrical performance level. High performance cables require special handling procedures to ensure optimum electrical performance. Many of these handling procedures will be discussed by a speaker from Insulated Wire (IW) in the presentation “How to Get the Best Performance Out of Your Cable Assembly.” By taking a few basic preventative measures during cable handling, installers and system assembly technicians can significantly extend the life of their assembly and avoid system failures. The expert from IW will provide tips on how to prevent some common problems such as internal damage caused by compression and how to prevent the cable from bending below its minimum bend radius which would cause the cable to kink and also results in internal damage. To maximize connector performance and lifetime, the presenter will discuss proper torque down procedures, connector orientation and how to avoid assembly twisting, proper cable tie down methods, providing adequate drip loops, weather proofing and working with short cable assemblies.

Connector Types

In addition to integrating modules and subsystems, connectors are also used to launch signals from coax to planar substrates where the surface mount ICs and discrete devices that provide radio functionality reside. With pressure to reduce circuit size and increase functionality, engineers are working with thinner PCB materials often at higher frequencies. Design and test engineers need to be aware of the quality of their electrical interface between planar substrate (microstrip, stripline, etc.) and the connector launch. Poor choice in connector size and shape can lead to undesirable parasitics and unacceptable VSWR, resulting in non-optimal performance, power loss and inaccurate device characterization (when being used as part of a test fixture). For example, substrates that are thinner than 8 mil have line widths that are too small to optimize the launch with a taper for even the smallest connector pin. For substrates that are thicker than 30 mil, line structures can be created that achieve a good match and bandwidth to 50 GHz, but the loss of these lines starts to increase significantly at higher frequencies.

In addition todeveloping better performing products, innovation can also target usability and convenience for the user. Maury Microwave, a leading test solutions provider that also develops interconnect products, will be discussing an innovation that does both. The company’s new China country manager, Nian-min Zhang, will present the new ColorConnectď››precision adapters, which are designed for lab and field use addressing the need for quality, performance, ease-of-identification and ease-of-use. New manufacturing techniques have resulted in improved VSWR specifications bridging the gap between calibration-grade metrology adapters and daily-use lab adapters. Following the proposed IEEE high-frequency connector/adapter color convention, the components are the first commercially available products to offer clear indications of compatibility and intermatability. Zhang will discuss how the product makes it a simple matter to avoid and eliminate damaged equipment, degraded equipment reliability, degraded performance and lengthymaintenance times due to improper mating (and attempted mating) of incompatible adapters.

Addressing Various Applications

Technology trends in circuit miniaturization, wide bandwidths, increased circuit density and functionality, linearity and passive intermodulation requirements are forcing evolution in connector technology. The physical and electrical attributes of connectors are constantly improving, supported by advanced design/analysis capabilities (3D EM simulation such as CST or HFSS) and precision machining.

Cable assemblies and connectors have become specialized for test applications, aircraft, spaceflight, defense and commercial communication applications. Clarifying the specific requirements of these different applications and aligning them to a particular interconnect technology will be a common theme of this special
EDI CON workshop/panel. The workshop will allow presenters to educate attendees with regard to some of these advances and the panel session will allow attendees to ask the experts about their own particular needs and challenges.