Banca de DEFESA: VOLKER KIBLE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : VOLKER KIBLE
DATA : 18/06/2021
HORA: 10:00
LOCAL: Salvador
TÍTULO:

SOFTWARE-DEFINED RF REFLECTION COEFFICIENT MEASUREMENT BLOCK BASED ON UNDER-SAMPLING DOWN-CONVERSION

PALAVRAS-CHAVES:

Reflectometer; Power amplifier, impedance matching, A/D Conversion

PÁGINAS: 110
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Elétrica
SUBÁREA: Circuitos Elétricos, Magnéticos e Eletrônicos
ESPECIALIDADE: Circuitos Eletrônicos
RESUMO:

In mobile radio frequency telecommunication devices, the antenna is often subject to

varying surroundings. These change the antenna input impedance and lead to impedance

mismatch with the following blocks, especially the power amplifier. This can cause various

unwanted effects such as nonlinear behavior and possibly damage. Amongst other

possibilities, one solution is an automatic impedance matching system, which acquires

information about the actual antenna input impedance and controls a variable impedance

matching network accordingly to minimize mismatch. The complete information about the

antenna impedance can be gained using a reflectometer. These devices usually comprise various analog hardware components with their respective nonidealities and possibly

energy consumption. These hardware components also need physical space and thus

obstruct miniaturization.

An interesting way to reduce nonidealities and space consumption is by moving a

maximum of the functionality into software. The challenge, in this case, is the high frequency

of the signals, leading to extreme processing requirements. To counteract this, sampling

effects in the inevitable analog-to-digital converter can be exploited. Physical and

mathematical constraints for this operation are found and the design theory of such a

system is presented. Then the validity of the concept is evaluated by computer simulations

and automated measurements on a discrete electronic setup against known references.

Also, once the reflection coefficient information is available in software, its further use for

controlling the variable impedance matching network is of relevance. One possible

algorithm is outlined for future reference.

The validity of the concept and of the according to design theory was proven. Mostly, the

measurement errors were below 2%. In severe mismatch cases, the under-sampling scheme

stopped working, but these cases present a high standard deviation and are thus easily

recognizable. The reason is the non-linear behavior of the unprotected power amplifier.

Various promising remedies are outlined, such as protecting the amplifier, reducing the

transmitted power when necessary, and filtering in the signal path for the generation of the

sample clock. As the system is planned to be part of an automatic impedance matching

system, however, extreme mismatch cases should normally not occur.

The study shows that it is possible to build a vastly software-defined reflectometer for

ultra-high frequency operation using standard, inexpensive hardware components. This

means that it should also be uncomplicated to integrate into a frontend integrated circuit

for any telecommunication system.

MEMBROS DA BANCA:
Presidente - 288125 - ROBSON NUNES DE LIMA
Interno(a) - 3030290 - MAICON DEIVID PEREIRA
Externo(a) à Instituição - BERNARDO REGO BATISTA BARROS DE ALMEIDA LEITE - UFPR
Externo(a) à Instituição - FABRÍCIO GERÔNIMO SIMÕES SILVA
Externo(a) à Instituição - PAULO MÁRCIO MOREIRA E SILVA