Short Range Device platform for NFC and RFID wireless Telecommunications

Abstract

In this thesis, it is analyzed in detail aspects related to compact RFID radio communications design,

and its interaction with di erent sort of elements starting from passive tags, the most widely used

interface in RFID world. Ending with application of RFID sensor semi-passive tags, where a new sort

of technologies are emerging in this interesting eld.

With the idea of facilitating the introduction of such RFID sensing new technologies, we have developed

and RFID reader that is very compact in design, and uses the mobile phone as the main human

interface. For that purpose, the reader has to comply with compact small factor, such as small planar

integrated antennas, very low power consumption and compact front end. Also must take special care

of interference. The mobile phone is a device that includes so many radio sources, that we must ensure

our radio can coexist with them, without being a ected by their interference and, without a ecting

them.

In addition to the previous interference analysis, and design demonstration for RFID front-end, we

have include some new concepts to mention:

Analysis of limitations in read ranges for UHF-RFID technologies.

Apply HF-RFID (such as NFC) not only for communications, but also for energy transfer.

Optimization of NFC front-end when using radio for both communication (with mobile phone)

and sending energy to remote sensors (charge remote battery).

Prove of concept using our designed RFID sensing devices.

Demonstrate new concepts of NFC-energy transfer for RFID sensors.

In order to help better understand the presented concepts, there are some analytical demonstrations

explained in detail, with particular numerical examples being applied to our design, that have the

intention to be taken as reference formulation and values for design.

Some concepts are explained based on simulations. In particular chapter 2 includes a system simulation

that faces with di erent temporal and frequency e ects. There are electromagnetic simulations (for

antenna simulation), with electrical simulation (front-end devices) and system simulations (include

RFID modulation and coding aspects). In chapter 3 many interaction e ects between coils and RFID

antennas are evaluated in detail. Also include the new concept that is used to optimize simultaneously

communications and energy transfer between our NFC device and a new made RFID sensor tag.

There are many explanations on how the energy transfer circuit works, based on di erent con gurations

between primary and secondary circuits (transmitter and receiver), and optimization techniques.

While chapter 4 and 5 are dedicated to hardware design, for reader in HF and UHF frequencies,

as well as passive-sensor tag design. Measurements are taken not only showing the possibility to use

NFC as a means for very short distance communications between our designed reader with the mobile

phone, but also to transfer energy to new ultra-low power RFID sensors.