Design and measurement techniques for next-generation integrated antennas

Better mobile connections possible by including human factor and agility in antennas and their characterizatio

Reverberation chamber enhanced backscattering: high-frequency effects

The need for accurate efficiency measurements at high frequencies of large form-factor devices is ever increasing. In this work, the potential of performing antenna efficiency measurements in an electrically extremely large (up to 250λ) reverberation chamber is investigated and compared to its use at lower frequencies. It is found that there are large deviations in the enhanced backscattering constant at high frequencies. Closer investigation, by introducing a position-dependent enhanced backscattering constant calculation, shows that the deviation mostly occurs at the horn antenna directed at the stirrer. This could be aggravated by the use of a moving wall type of stirrer. The work concludes by demonstrating the potential impact of these deviations on the antenna efficiency. The deviations clearly show the need for more research into these effects

Broadband material characterization method using a CPW with a novel calibration technique

When combining contactless power and data transfer, antennas are often placed near magnetic materials with unknown RF properties. While permittivity measurement methods for dielectric materials at RF frequencies are well established, methods for permeability measurement are relatively scarce and often cumbersome. We propose a versatile and easy-to-use method that is applicable to both dielectric and magnetic materials, which uses a coplanar waveguide structure to measure the complex permittivity and permeability in the 1–16 GHz range. We combine the Nicolson–Ross–Weir algorithm with a robust root selection and a conformal mapping method to extract the permittivity and permeability from the measurement data. Moreover, we propose a novel calibration method that uses a single reference dielectric to increase the accuracy of the measured permittivity significantly, even when measuring magnetic materials

Benchmarking a high-end smartphone’s antenna efficiencies

In an effort to create a benchmark for antenna designs for mobile applications, the total and radiation efficiencies of a modern high-end smartphone’s antennas are measured. To this end, an adapter board is designed that facilitates the connection to a calibrated measurement system. Its shape is chosen to closely resemble the original phone’s dimensions while allowing connection of the antennas via spring fingers to a coaxial measurement system. The characterization of this mock-up is performed in a reverberation chamber, which offers the advantage of an on-average isotropic environment, making it ideal for antenna reflection coefficient and efficiency measurements. The reflection coefficients, total efficiencies, and radiation efficiencies of the mock-up are then measured from 0.75 to 6 GHz. The total antenna efficiencies, not accounting for a possible improvement due to adaptive matching networks, are found to be below 15% up to 4 GHz and up to 25% below 6 GHz. Meanwhile, the radiation efficiencies are up to 15% below 2.5 GHz and up to 40% below 6 GHz. Such antenna efficiency measurements are the first and serve well as a benchmark for future designs and concepts

A new design method for frequency-reconfigurable antennas using multiple tuning components

Frequency-reconfigurable antennas seem a viable solution to achieve better performance and increased flexibility for integrated mobile phone antennas. Due to the lossy nature of many tunable components, the use of multiple combined tuning components in a single design seems attractive, as it can distribute the current over the components. However, many combinations of individual tuning component settings can result in an acceptable input match, while they will significantly vary in terms of radiation efficiency. It is challenging to distinguish between these radiating and nonradiating tuning component settings during the design procedure. In this paper, we propose a method to determine the component settings with the highest efficiency at a desired operating frequency. The method uses a single full-wave simulation, which is combined with circuit-level calculations. We discuss how to apply the method in detail and demonstrate its functionality with an inverted-L antenna sporting three tunable barium-strontium titanate capacitors. It is shown that the method can successfully predict tuning component settings for high antenna efficiency over a 1.4-2.8 GHz tuning band, with total efficiencies up to 35% and radiation efficiencies up to 50%. The method can easily be applied to any desired antenna geometry

Reverberation chamber enhanced backscattering:high-frequency effects

The need for accurate efficiency measurements at high frequencies of large form-factor devices is ever increasing. In this work, the potential of performing antenna efficiency measurements in an electrically extremely large (up to 250λ) reverberation chamber is investigated and compared to its use at lower frequencies. It is found that there are large deviations in the enhanced backscattering constant at high frequencies. Closer investigation, by introducing a position-dependent enhanced backscattering constant calculation, shows that the deviation mostly occurs at the horn antenna directed at the stirrer. This could be aggravated by the use of a moving wall type of stirrer. The work concludes by demonstrating the potential impact of these deviations on the antenna efficiency. The deviations clearly show the need for more research into these effects

Chasing the wave in a reverberation chamber

\u3cp\u3eThe power-delay profile is a critical characteristic of a reverberation chamber. In this paper the power-delay profile is used for the first time to study in high detail how a wave interacts with its environment in a reverberation chamber. This is done by tracking the wave, starting from its creation at the antenna reference plane with the antenna in multiple positions. Starting at the antenna port, three regimes are recognized: very-early-time, early - time and late-time. In the very -early - time the response is dictated by the antenna's behavior and placement affects only the duration of this regime. In the early-time period the wave starts interacting with the environment. Antenna positioning makes a clear difference during this period, and the moving-wall stirrer can easily be distinguished from non-moving parts. During late-time the expected exponential decay is observed. The transition point from early to late behavior is dependent on antenna placement in the room that was used. After chasing the wave traveling at light speed for a kilometer, it is finally caught when the chamber losses cause the power delay profile to decay into noise floor.\u3c/p\u3

How tough are the front-end requirements for 4G-and-beyond handsets?

\u3cp\u3eDue to the interrelation of different stages within the handset receiver, it is often desired to have clear requirements for the RF receiver front-end. However, the LTE standard specifies only the system-level performance, and extracting the receiver's front-end requirements is not straightforward given the complexity of current standards. These front-end requirements are important to make the right technology choice. In this paper a clear overview of the required calculations and their results is given, treating the noise figure, selectivity/blocking and cross- and intermodulation requirements. This avoids the need to perform system-level simulations in the early design stage and provides the designer with insight on the impact of the RF receiver front-end on the system-level performance. The results are related to the technology choice, where it is shown that SiGe and GaAs can achieve both the required sensitivity and linearity. To the best of the authors' knowledge this is the first time that such an overview is given and applied to determine a suitable technology. The requirements for 5G systems are expected to be more stringent, making the already tough requirements for 4G even tougher for future systems.\u3c/p\u3

Wireless receiver architectures towards 5G:where are we?

\u3cp\u3eWith 5G posing different requirements to the mobile (handset) receiver than earlier generations, the receiver architecture needs to be carefully reconsidered. However, an up-to-date and complete overview is not yet available in literature. In this paper such a review of the currently available receiver architectures is provided, as well as an overview of current trends. For the first time, a framework is introduced that allows a systematic classification of architectures. An identification of unexplored possibilities and system-level trade-offs follows. A more flexible, low-power and high-performance receiver architecture than currently applied is needed for 5G, for which this framework becomes a useful tool.\u3c/p\u3