RFID READER ANTENNA BASICS – OVERCOMING FADING WITH ANTENNA DIVERSITY

RJ Burkholder, Research Professor of Electromagnetics and RF at The Ohio State University

In the last several blogs I maintained that the antenna is the most important part of a UHF RFID system (see figure below). This is because the computer software, reader, and RFID tag are fairly optimized now, and often outside the control of the system designer anyway. Performance improvements must come from the proper selection of the antenna and its deployment.

image1

A typical UHF RFID inventory system

Before getting into the fine art of antenna deployment, it was first necessary to understand the basic principles of how antennas work and how the electromagnetic field radiated by an antenna fills and penetrates a given space. The main issues are polarization, fading, gain, EIRP (effective isotropic radiated power) and diversity. A good understanding of these issues will aid the designer in selecting the type and number of antennas, and where to put them for optimum performance.

To review, we first explored the most basic characteristic of an antenna, namely, its gain. This number is defined as the directional amplification of the antenna compared with an antenna that radiates equally in all directions (isotropic...

RFID ANTENNA BASICS – GAIN AND EIRP

RJ Burkholder, Research Professor of Electromagnetics and RF at The Ohio State University1

In the last blog I maintained that the antenna is the most important part of a UHF RFID system (see figure below). This is because the computer software, reader, and RFID tag are quite optimized now, and often outside the control of the system designer/integrator. Performance improvements must come from the antenna and its deployment.

image1-300x188.jpg

A typical UHF RFID inventory system

Before getting into the fine art of antenna deployment, it is first necessary to understand the basic principles of how antennas work and how the electromagnetic field radiated by an antenna fills and penetrates a given space. The main issues are polarization, fading, attenuation, gain, maximum EIRP (effective isotropic radiated power) and diversity. A good understanding of these issues will aid the designer in selecting the type and number of antennas, and where to put them for optimum performance.

The most basic characteristic of an antenna is its gain. This number is defined as the amplification of the antenna compared with an antenna that radiates equally in all directions. Hence, the units of gain are often dBi, which means “decibels...

SMART SHELF™ & THE INTERNET OF THINGS

Author: Dr. Den Burnside CTO and Founder of NeWave® Sensor Solutions and Emeritus Professor at the Ohio State University

NeWave® Sensor Solutions was recently interviewed for  the  Discovery Channel’s  new web and Facebook program: “Technology is Changing How We Live ” ,sponsored by DeVry University. NeWave’s Smart Shelf™ was selected by the Discovery Channel  to showcase future technology in “Cashier Free Retailers” and as an excellent example of a smart device enabling the  Internet of Things (IoT).  We recommend opening links in Internet Explorer.

Why is that important? Let’s examine what is the definition of the Internet of Things and the attributes of NeWave’s Smart Shelf.

 “Internet of things
From Wikipedia, the free encyclopedia

Drawing representing the Internet of things

The Internet of things (IoT) is the inter-networking of physical devices, vehicles (also referred to as “connected devices” and “smart devices“), buildings, and other items—embedded...

A NEW PARADIGM FOR ITEM-LEVEL RFID ANTENNAS

Author: RJ Burkholder, Research Professor of Electromagnetics and RF at The Ohio State University

For years RFID system designers have trusted in the old reliable patch antenna to solve all their reader antenna needs. But how reliable is it? If you were to picture the beam, it would look something like a single beam, conical spotlight illumination pattern:

blog-01-01-300x153.jpg

This might be good if you’re looking for tags that are far away and in a specific and known location, but not good for tags that may be close to the antenna but outside the beam. Also, in most portal and item-level applications you don’t want to see tags that are far away, extraneous tags, because that makes it difficult to localize the tags of interest.

What’s the solution? Well, we can crank down the power on the RFID reader, but that doesn’t solve the spotlight problem because the beam simply collapses in the same pattern. We can use more antennas to try and fill in the gaps in the illumination, but that is a Band-Aid solution at best, one never really knows if all the gaps are covered and it becomes a complex and expensive solution. Another possibility is the so-called “near-field antenna” (an oxymoron to antenna designers), but these have a very limited range, too...

RFID READER ANTENNA BASICS – THE WAVE® ANTENNA SOLUTION

RJ Burkholder, Research Professor of Electromagnetics and RF at The Ohio State University

In the last several blogs I explained why the antenna is the most important part of designing a UHF RFID system (seefigurebelow). This is because the computer software, reader, and RFID tag are fairly optimized now, and often outside the control of the system designer anyway. Performance improvements must come from the proper selection of the antenna and its deployment.

image1

Before getting to antenna deployment in RFID system design, it was first necessary to understand the basic principles of how antennas work and how the electromagnetic field radiated by an antenna fills and penetrates a given space. The main issues are polarization, fading, gain, EIRP (effective is otropic radiated power) and diversity. A good understanding of these issues will aid the designer in selecting the type and number of antennas, and where to put them for optimum performance.

To review, we first explored the most basic characteristic of an antenna, namely, its gain. This number is defined as the directional amplification of the antenna compared with an antenna that radiates equally in all directions (isotropic). Gain is closely related to Effective...