Antenna system integrated within the set-top-box environment 

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Wireless Local Area Network (WLAN)

In our research work, the Wireless Local Area Network is one of the required applications of the set-top-box. Therefore, the realization of the WLAN antenna on paper substrate in the bibliography is an important reference.
Konstas has presented in 2009 a « green » Z-shaped inkjet-printed monopole antenna topology on a flexible, low-cost photo paper substrate for UHF RFID tags. The paper substrate had thickness of 0.254 mm, a relative permittivity of 3.4 and a loss tangent of 0.08 with overall dimensions 75mm x 100mm, including the feed line. Monopole antenna type was utilized in his research work thank to its broadband characteristics and the use of a ground plane as an extra shield for other electronic components (sensors, power sources, IC) in the system, alleviating the cross-coupling and interference. In order to evaluate the inkjet printing technique, the same antenna was also fabricated with thin adhesive copper tape glued on the paper. Both prototypes (inkjet-printed and copper tape fabricated) showed similar resonant frequency around 900 MHz with a slight difference in bandwidth. The directivity of the inkjet-printed antenna was found 0.2dBi in the simulation. [Konstas 2009].

Ultra-wide-band or multi-frequency antenna

Multi-frequency or ultra-wide-band is an obligatory characteristic of our antenna design in order to ensure the operation of multi-standard and multi-application. Thus, some of the designs below give us ideas to implement our own antenna system.
Shaker et al. from University of Waterloo have demonstrated in 2011 a planar ultra-wideband (UWB) monopole through ink-jetting of conductive inks (3 µm ink thickness, = 9×106-1.1×107 S/m) on commercially available paper sheets (254 µm thickness, tan = 0.06-0.07) up to frequencies above 10 GHz (3-10.5 GHz). The measured pattern was almost uniform (omnidirectional) for the selected frequencies, which is ideal for many UWB applications. The antenna efficiency was better than 80% throughout the whole band. This work was expected to pave the way toward the next-generation of low-cost, environment-friendly ubiquitous UWB sensor networks. [Shaker 2011] Cook et al. from KAUST have developed in 2012 an UWB antipodal Vivaldi antenna (1-11 GHz), inkjet-printed ( = 1.2 x 107 S/m) on lossy paper substrate (loss tangent about 0.06). This antenna exhibited a significantly higher gain up to 7.8 dBi as compared to the others inkjet-printed antennas. His work laid a strong foundation for the fabrication of low-cost, high-gain and wideband antenna on environmentally friendly substrates using the inkjet printing process. [Cook 2012-1].
However, in general, these antennas have a very large size and do not meet the compact requirements in order to be integrated into our set-top-box. Meanwhile, Abutarboush has concentrated on the development of inkjet-printed multi-frequency monopoles on paper substrate with different configurations. These antennas had almost low profile, compact size, light weight and low cost in order to integrate into small and slim wireless devices.
He has first presented a U-slot tri-band monopole antenna on a low-cost paper substrate using inkjet-printing technology with silver nanoparticle ink ( = 1.2×107 S/m). This compact size (12×37.3×0.44 mm3) antenna had a tri-band operation of 1.57, 3.2, and 5 GHz with measured impedance bandwidths of 3.21%, 28.1%, and 36%, respectively enough to cover the GPS, WiMAX, HiperLAN/2, and WLAN bands. The simulated radiation efficiencies were about 55%, 79%, and 71% in the 1.57, 3.2, and 5 GHz bands, respectively. The operating principle is very simple: it has three radiator branches for three resonance frequency and each branch could have a meander line configuration for the miniature purpose. [Abutarboush 2012].

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Wireless sensor nodes

In this subsection, the demonstrated circuit structure is more complex, and the antenna is combined with others components in order to create the completely integrated modules on the paper substrate. Integrating sensors in the RFID tags renders the whole system capable of not only tracking but also providing real-time information about the environment. The ultimate goal is to create an easily deployable intelligent network of RFID-enabled sensors with as low-cost as possible.
Since 2006, the realization of the first highly integrated RFID-enabled wireless sensors on ultimate low-cost synthetic material such as photocopy papers has also been addressed by Vyas et al. from Georgia Tech [Vyas 2008]. The general system level design for this wireless transmitter, which used a dipole antenna for an operation of ISM (Industrial, Scientific, and Medical) frequency band at 904.4 MHz, is presented in Figure 1-55a. The complete wireless sensor system comprised a Microcontroller Unit (MCU), Phase Lock Loop (PLL) module, Power Amplifier (PA), an external crystal oscillator, a temperature sensor and a battery cell for « stand-alone » autonomous operation.

Table of contents :

Introduction
Chapter 1: Context and state of the art
1.1 Introduction
1.2 Context and Objective
1.2.1 Context
1.2.2 Objective
1.3 State of the art of flexible electronics
1.3.1 Technology
1.3.1.1 Flexible substrate
1.3.1.2 Metallization process on flexible substrate
1.3.1.3 Treatment process on paper
1.3.2 Applications
1.3.2.1 RFID tag
1.3.2.2 Wireless Local Area Network (WLAN)
1.3.2.3 Ultra-wide-band or multi-frequency antenna
1.3.2.4 3D antenna
1.3.2.5 Wireless sensor nodes
1.3.2.6 Radar system
1.4 Conclusion about the state of the art and positioning of this thesis
Chapter 2: Characterization of flexible substrate and conductive layer
2.1 Introduction
2.2 Dielectric characterization of flexible substrate
2.2.1 State of the art
2.2.1.1 Two planar transmission lines
2.2.1.2 Microstrip ring resonator
2.2.1.3 T-resonator
2.2.1.4 Cavity resonator
2.2.2 Realized method
2.2.2.1 First tests
2.2.2.2 Dielectric characterization
2.2.3 Discussion
2.2.4 E4D paper
2.3 Characterization of conductive layer
2.3.1 SEM image of ink deposit surface
2.3.2 Printing process on paper
2.3.2.1 Flexography printing
2.3.2.2 Screen-printing
2.3.3 Measurement of thickness and conductivity of ink deposit
2.4 Conclusion of chapter 2
Chapter 3: Antenna realization on flexible substrate
3.1 Introduction
3.2 Patch antenna
3.3 Planar monopole antenna
3.4 Dual-band Wi-Fi monopole antenna (2.4 GHz/5.5 GHz)
3.5 Planar dual-band dipole antenna (2.4 GHz/5.5 GHz)
3.6 Conclusion of chapter 3
Chapter 4: Antenna system integrated within the set-top-box environment 
4.1 Introduction
4.2 RF interconnection to PCB mainboard
4.2.1 Miniature coaxial cables – Available solutions and limitations
4.2.2 Identification of interconnection solutions compatible with paper & flex technologies – State of the art
4.2.2.1 Classical interconnection using conductive glue and assembling techniques
4.2.2.2 Interconnect through direct or pseudo-direct compression techniques
4.2.2.3 ZIF (zero insertion force) connector for RF applications
4.2.3 Investigations: characterization of flexible interconnections using advanced ZIF connectors
4.2.3.1 Interconnection between 2 transmission lines
4.2.3.2 Interconnection from antenna to PCB mainboard
4.2.4 Conclusion
4.3 Antenna system on flexible substrate
4.3.1 Three dual-band Wi-Fi monopole antenna
4.3.2 Three dual-band Wi-Fi dipole antenna
4.4 Conclusion of chapter 4
General conclusions and perspectives
ANNEX A: Measurement of conductivity of ink deposit
ANNEX B: Dielectric properties of ABS plastic
REFERENCES

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