General Wireless

cHTML cHTML was developed by NTT DoCoMo as the wireless language to use in programming the wireless devices that are served by their wireless Internet access service, i-mode. cHTML ( Compact Hypertext Markup Language) is a subset of HTML, but cHTML ... [full story]

An Example Wireless Sensor Network Transceiver Integrated Circuit (IC) This appendix describes a short-range, low-power 2.4-GHz Industrial, Scientific, and Medical (ISM) band transceiver designed for the emerging IEEE 802.15.4 wireless standard supporting star and mesh networking (Exhibit 1). When combined with ... [full story]

Signal Processing Worksystem (SPW) The Signal Processing Worksystem (SPW) from Cadence Design Systems, Inc., San Jose, California, (http://www.cadence.com) is a system-level design tool originally designed for the development of digital signal processing (DSP) algorithms and hardware. The increased use of DSP ... [full story]

OPPORTUNITIES FOR FUTURE DEVELOPMENT One is tempted to state that, since the technology is only now emerging from academic research into commercial application, all areas of wireless sensor networks represent opportunities for future development. However, some areas merit particular attention. Opportunities for ... [full story]

THE IEEE 1451.5 WIRELESS SMART TRANSDUCER INTERFACE STANDARD The development of wireless sensor network technology and standards is not being driven solely by the communications interface. Manufacturers, implementers, as well as users of sensors have expressed a desire for wireless connectivity.[7] ... [full story]

THE ZIGBEE ALLIANCE As noted previously, the IEEE 802.15.4 standard does not standardize the higher communication protocol layers, including the network and application layers. To assure interoperability between devices operating the IEEE 802.15.4 standard, the behavior of these layers must be ... [full story]

THE IEEE 802.15.4 LOW-RATE WPAN STANDARD As noted in Chapter 1, the scope of the IEEE 802.15.4 task group, as defined in its original Project Authorization Request, is to "define the PHY and MAC specifications for low data rate wireless connectivity ... [full story]

Once an ESD Event Occurs, Limit Discernable Effects Despite all efforts to the contrary, an ESD event may still occur. If it produces physical damage, little can be done in most cases except replacement of the affected component or the entire ... [full story]

Reaching the Integrated Circuit Protecting an integrated circuit from an electrostatic discharge is difficult because the structures in an integrated circuit have very limited power dissipation capabilities and overvoltage survival abilities. Once a discharge reaches the package of an integrated circuit, ... [full story]

Once Inside, Design Paths for the Discharge to Travel If, despite the best efforts of the designer, the discharge arrives on the circuit board, one is in a significantly more difficult position. the charge will want to redistribute on all metal ... [full story]

Prevent Discharges from Entering or Exiting the Housing The fundamental rule, and paradoxically the rule most easily overlooked by electrical design engineers, is to prevent electrostatic discharges from entering or exiting the housing of the network node. This can be accomplished ... [full story]

PRODUCT DESIGN TO MINIMIZE ESD PROBLEMS Several strategies can be employed to improve the robustness of a wireless sensor network node to an ESD event. Many of them concern the mechanical and industrial design of the node, and only tangentially involve ... [full story]

Performance Standards ESD resistance may be specified at two levels: the product level and the component level. Product level performance standards are typically much higher than those of the components from which the product is made. Product level standards may reach ... [full story]

Detailed Requirements of an ESD Standard A large number of ESD standards and test methods are available.[18], [19] It is instructional to consider the requirements of a particular standard in more detail. The IEC 61000–4–2 standard, from the International Electrotechnical Commission ... [full story]

Human Body, Machine, and Charged Device Models Another way of modeling the ESD event is by an equivalent circuit model (Exhibit 2). To model a discharge from a human body, an RC network consisting of a capacitor discharging through a resistor ... [full story]

The Double Exponential Pulse The waveform of an electrostatic discharge current has a 10 to 90 percent rise time of perhaps 150 ps to a peak amplitude of perhaps 10 Amperes, then falling off gradually with time.[12] The length of the ... [full story]

MODELING AND TEST STANDARDS For design, development, and testing of ESD-resistant devices and systems — just a part of a complete ESD control program[11] — the ESD event must be modeled. Two basic approaches are used: an analytical model, describing the ... [full story]

THE EFFECTS OF ESD ON ICS Generally, ESD can damage an IC in two ways: thermal effects due to the energy of the discharge applied to the small geometries of active devices or interconnects, and overvoltage effects, in which a MOS ... [full story]

Charge Redistribution Because a spark is an electrostatic effect, and does not conduct a DC current, a return DC path to the source is not needed to support it. See Exhibit 1a. Exhibit 1: Charge Redistribution Suppose a voltage V ... [full story]

Air Breakdown The charge redistribution associated with an ESD event usually, although not always, includes an air discharge because the event itself lasts only nanoseconds, but most physical movement of electronic products occurs on much longer time scales. It is, therefore, ... [full story]

The Triboelectric Effect It was discovered in antiquity that, when certain dissimilar materials were rubbed together, what we now call an electrostatic field was generated between them. One of the materials becomes more positive with respect to the other. This phenomenon ... [full story]

PHYSICAL PROPERTIES OF THE ELECTROSTATIC DISCHARGE The phenomenon of electrostatic discharge has been studied extensively in the last three decades, largely due to its increasingly important economic effect on the semiconductor industry, and several excellent texts are available on the subject ... [full story]

Electrostatic Discharge 10.1 INTRODUCTION This chapter reviews the problem of electrostatic discharge (ESD) as it affects wireless sensor network nodes, and the importance of proper electrical, mechanical, and product design in its control. Similar to electromagnetic compatibility (EMC) problems, ESD problems often ... [full story]

Get to Know the IC Designer Much insight can be gained into many EMC problems if the operation of the integrated circuits involved is understood and appreciated. Knowing, for example, which internal function is supplied by which Vdd and Vss pins ... [full story]

The Fallacy of Shields Shields have their uses, although they are unpleasant in most factory production processes, expensive, and often a quality problem; however, the engineer should remember that there is no ground in most wireless sensor network nodes. In most ... [full story]

Physical Separation Because both inductive and capacitive coupling are functions of distance, distance can also be used to aid the investigation of an EMC problem. If the product design includes multiple circuit boards, a ribbon cable connection between two boards may ... [full story]

Software to Control Specific MCU Functions Many times, the source of the difficulty can be understood, or at least the testing made easier, if the microcomputer controlling the network node can be programmed to independently control specific functions. These functions may ... [full story]

Substitution Substitution is a powerful method to isolate EMC problem causes and cures. For example, one of the most telling substitutions to make to resolve a receiver desensitization problem is to remove the antenna and measure sensitivity "conducted" (i.e., with the ... [full story]

The "Hole in the Bucket" Principle The "hole in the bucket" principle refers to a leaky bucket — all holes must be repaired before the bucket stops leaking. Similar to the bucket, a network node may have more than one EMC ... [full story]

DETECTIVE/CORRECTIVE TECHNIQUES Despite one's best efforts, EMC problems will still occur on occasion. The product engineer can therefore benefit from knowledge of ways to analyze EMC problems and possible correction techniques. The following list of analysis and correction techniques is not ... [full story]

EMC-Aware Layout Procedure When modifying an existing design, with components of known characteristics and systems of known performance, it is usually not necessary to make an exhaustive EMC analysis; however, when starting a new design, possibly in a new market, incorporating ... [full story]

Things to Look for After the Schematics Are Done but Before the Layouts Are Started Before starting a layout, it is wise to spend a few minutes examining the electrical schematic to identify potential EMC threats and potential EMC victims. After ... [full story]