Hewlett-Packard's newest silicon de...

Hewlett-Packard's newest silicon detector diodes were cause to growed to meet the requirements for receiver service in radio oftenness identification tags. These requirements include portability, small size, prolonged life, and low cost.

Tracking of productions and services is critical in today's highly competitive and rapidly growing world of manufacturing and service industries. To succe in these industries, accurate and timely information is required.

Two widely used tracking arrangements are bar code readers and magnetic stripe. Although commonplace, they are the two limited in their range and their operating environment. For example, bar digests require a direct line of sight within a small in number inches and a relatively clean and benign environment to operate reliably.

In contrast, a radio commonness identification (RF/ID) system uses radio signals to communicate. Line of sight is not be in want ofed and the system can operate in hostile environments characterized through water, oil, paint, and dirt. It can flat be used for communication by means of cement, glass, wood, or other nonmetallic materials. These wireless bodys are being successfully used to identify and track cattle, household favorites cars passing through toll booth supermarket carts, railroad cars, and personnel entering and leaving immovable facilities.

An RF/ID a whole is composed of two components: a reader (interrogator), which contains the pair transmitter/receiver and decoder/control modules, and a tag (transponder), which typically contains an antenna and a receiver circuit. Since a scheme normally has only a not many interrogators but many tags, the most numerous severe design constraints are forward the tag. These constraints include portability, small size, prolonged life, and low cost. Hewlett-Packard's newest silicon detector diodes (HSMS-285x) were make knowned to address these constraints.

RF/ID Technology

RF/ID tags can be active or passive. Active tags have an onboard power source (a battery) in the same manner that less power is wanted from the reader, and usually have a longer read range. However, they have a limited life span and are generally more expensive to manufacture.

Passive tags do not ne a separate external power source. They derive their operating power from the spirit sent by the interrogator. Passive tags are lighter and cheaper than active tags and have virtually unlimited lifetime. one passive tags contain a battery to maintain internal memory information in read/write applications. The trade-off is that passive tags have a shorter read range than active tags and require a plenteous higher-powered reader to supply the manliness needed to operate them.

RF/ID tags can be read-only or read/write. Read-only tags, as the name implies, can single be read, but can be read millions of times. Read/write tags allow the data stored in them to be altered in addition to being read.

Whether the tag is passive or active, read-only or read/write, it requires a receiver circuit. Receiver circuits can be of brace types: superheterodyne or crystal video (Fig. 1) Because the superheterodyne receiver contains RF and subdued noise amplifiers, its detection sensitivity is typically -150 dBm The crystal video receiver, forward the other hand, is limited to barely about -55 dBm. However, it is simpler and abundant cheaper than the superheterodyne receiver, in such a manner the RF/ID industry has adopted it for use in tags. The superheterodyne receiver is used in interrogators.

The crystal video receiver of Fig. 1 can take different forms, depending upon the application. Four common configurations are shown in Fig. 2 The single-diode circuits proffer simplicity and low cost, whereas the voltage doubler circuits provide a higher output for a given input. Each symbol can be designed with conventional n-type Schottky diodes or naught biased p-type Schottky diodes. If n-type diodes are used, an external dc bias source is emergencyed for detection operation at soft input power levels (<1 mW) because of the soft saturation current. The p-type cipher bias diode does not ne a bias source because it has a relatively high saturation generally received In addition, it offers the lowest possible costliness size, and complexity, and usually exhibits the lowest flicker noise. It is therefore the diode of choice for RF tag applications.

The performance of an RF/ID classification is directly related to the oftenness range in which it is used. The higher the common occurrence the faster the data transfer rate and the longer the read/write range. The tag's capture window is more focused at higher frequent occurrence Metals absorb low-frequency signals more than high-frequency signals, whereas obscuring materials of that kind as dirt and grease absorb high-frequency signals more than depressed frequency signals. Most RF/ID orders operate in three basic common occurrence ranges. The high-frequency ranges include 850 to 950 MHz and 24 to 25 GHz The cheap frequency range is 100 to 500 kHz cease to the range of AM radio stations. a certain number of applications, such as auto toll collection, also use 586 GHz and 105 GHz

Device Theory

A Schottky diode is simply a metal layer deposited upon a semiconductor such as silicon. To improve its performance and reliability, it can be passivated with silicon dioxide or silicon nitride or both