Total Radiated Power Research Articles

Quadrupolarisability extraction for planar metamaterial scatterers via far-field response

PurposeThe majority of first-principle, homogenisation techniques makes use of the dipole terms of a small particle radiation, and, consequently, the respective dipole polarisabilities. This paper aims to take the next step and propose a new systematic technique for extracting the quadrupolarisability of planar metamaterial scatterers.Design/methodology/approachFirstly, it is assumed that the particle, under study, can be modelled as a set of dipole and quadrupole moments, and by utilising the respective polarisabilities, the far-field response of the scatterer is calculated. Then, the far-field scattering field of the particle is constructed in terms of the dipole and quadrupole moments, which, in turn, are expressed as a function of the unknown polarisabilities. Finally, the desired polarisabilities are retrieved by a system of equations, which involves numerically derived electric field values at specific positions around the scatterer.FindingsThe quadrupolarisability of planar metamaterial particles is extracted, through an easy to use, yet very accurate and efficient methodology. Moreover, the proposed technique is verified via comprehensive comparisons of consequently computed and simulated total radiated power values, which reveal its advantages and applicability limits. Finally, the total radiation power contribution of each calculated, individual multipole is provided, to further investigate the radiation mechanism of all nano-particles under study.Originality/valueThe initial and most important step of extracting a single quadrupolarisability of a planar realistic nano-particle has been performed, herein, for the first time. The addition of the respective quadrupole in the scattering model, shifts the multipole approximation limit upwards in terms of frequency, and, therefore, nano-particles with quadrupole resonances can, now, be precisely represented via polarisabilities for various metamaterial or metasurface applications.

Large-Scale Analysis of the Head Proximity Effects on Antenna Performance Using Machine Learning Based Models

Owing to the variations in subject-specific body morphology and anatomy, the radiation performance of a wireless device in the presence of human body is different across subjects. To quantify the inter-subject variations, a large number of highly realistic human models are required. One recent approach is the fast development of body models directly from medical images with machine learning. In this study, a total of eighteen anatomical head models were developed using a fast machine learning approach and were then adopted for large-scale evaluation of the inter-subject variations in antenna performance. The antenna impedance, return loss (RL), total radiated power (TRP), directivity, radiation patterns, and specific absorption rate (SAR) were investigated. The results show rather large variations in impedance, RL, and SAR across subjects, while TRP, directivity, and radiation pattern are less likely to be affected by internal tissue distributions when compared with homogeneous models.

Implications of Incident Power Density Limits on Power and EIRP Levels of 5G Millimeter-Wave User Equipment

User equipment (UE) is required to comply with the relevant radio frequency (RF) electromagnetic field (EMF) exposure limits, which are of relevance to establish the maximum permissible transmitted power and the maximum equivalent isotropically radiated power (EIRP). Recently, international RF EMF exposure guidelines, such as those published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) as well as by the IEEE, have been updated. In this paper, the implications of the revised incident power density limits are investigated in terms of maximum permissible transmitted power and the maximum EIRP for devices operating in close proximity of the user. A similar analysis is conducted according to the US Federal Communications Commission (FCC) regulation on RF exposure. EMF compliance of UE is studied by means of numerical modelling of patch antenna arrays of different array sizes taking into consideration of possible beam-steering operations, at frequencies ranging from 10 GHz to 100 GHz. The results are compared with the 3rd Generation Partnership Project (3GPP) requirements on the total radiated power (TRP) and EIRP levels. The present implications of the incident power density limits for 5G millimeter-wave UE will give valuable insights to mobile equipment manufacturers, network operators, and standardization bodies.

Average Rician K-Factor Based Analytical Uncertainty Model for Total Radiated Power Measurement in a Reverberation Chamber

Total radiated power (TRP) is commonly accepted as an important figure of merit (FoM) for evaluating the over-the-air (OTA) performance of wireless devices enabled by the emerging fifth generation (5G) mobile communication technology. The statistically homogeneous and isotropic electromagnetic (EM) environment created by a reverberation chamber (RC) makes it an accurate, efficient, and economic testing facility for TRP measurement. In this paper, an improved analytical uncertainty model which is based on the average Rician K-factor (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> ) and the number of independent samples is proposed for TRP measurement using an RC. It has the flexibility to allow different stirring configurations in the calibration stage and the measurement stage, and gives insight into the measurement uncertainty without the tedious and inefficient empirical estimation processes. Estimators of K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> are modelled and analyzed. Specifically, the maximum likelihood estimator (MLE) of K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> is validated by the Monte Carlo simulation, and its unbiased correction is derived accordingly for improved uncertainty model accuracy. Extensive 9-Point estimation measurements are also conducted in order to evaluate the performance of the proposed analytical model.

Coupling Path Visualization and EMI Mitigation for Flyover QSFP Connectors

In this article, the energy parcels concept is used to reveal radiation physics and coupling in the entire structure of flyover quad form-factor pluggable (QSFP) interconnection. Flyover QSFP has better signal integrity than legacy surface mounted printed circuit board QSFP technology. To understand electromagnetic interference aspects, a simulation model was built and correlated to measured total radiated power (TRP) for common mode and differential mode excitations for a frequency range of 1-40 GHz. Further, the energy parcels and their trajectories concept were applied to visualize the coupling path by tracking back the energy parcels from outside of the chassis (quiet side) toward a host board inside the chassis (noisy side). Then, high-density regions of energy parcel trajectories guide where to place the absorbing material efficiently and appropriately. Two locations were examined by filling them with electromagnetic lossy material and improvement was validated by TRP simulation and measurement.

Shortest range length to measure the total radiated power

Total radiated power (TRP) is a key performance metric in over-the-air (OTA) testing of wireless devices. The TRP is evaluated by integration of the power density over a surface enclosing the device under test (DUT). In principle, this total power flow shall be independent from the surface. However, the power received at the instrumentation in a given polarisation typically relates to the intensity of the corresponding component of the impinging E-field. In the far-field, the E-field magnitude and power density are straightforwardly related, but not in the near-field. Therefore, the measured TRP generally depends on the scanned surface and test distance. This study introduces a closed-form expression for the measured power integrated over a surface surrounding the DUT, including the influence of the probe. The formulas are first applied to simulated spherical testing systems, where three different measurement probes coupled to a DUT model radiating at 28 GHz. Results are then validated experimentally in two spherical scanners, using physical samples of one of the modelled probes and the DUT. Both numerical and experimental results confirm the Fraunhofer distance as a lower bound range length for OTA TRP evaluation with negligible influence from the measurement probe.

Design and acceptance test of compact planar monopole antenna for LTE smartphone considering SAR, TRP, and HAC values

SummaryEight different types of compact multiband planar antennas are proposed in this work for covering several long‐term evaluation (LTE) and Wi‐Fi bands in a smartphone antenna design. Gradual inclusion of several sections of a radiator on an inexpensive FR4 substrate is presented for receiving multi‐LTE bands with a handset device. Along with the presently available LTE bands, this antenna design approach also includes upcoming LTE in unlicensed spectrum and LTE licensed‐assisted access. Various techniques such as partial ground, branch line slit, parasitic structure, and meandered lines are used to achieve desired resonant frequencies, bandwidth, matching, and miniaturization. The final type of eight antennas has been implemented in the real‐world mobile phone handset. The interaction between the mobile handset and the human phantom model has been analyzed at few specific frequencies for evaluating specific absorption rate (SAR) and total radiated power (TRP) in a simulated manner. The same type is also studied as a hearing aid compatibility (HAC)–supported wireless device. The simulated results show the SAR and HAC values are at the acceptance level for this proposed design. A prototype model is developed and few parameters are measured for validation.

Over-the-Air Evaluation of the Antenna Performance of Popular Mobile Phones

Mobile terminals have become an integral part of people’s everyday life. The ability of the handset to transmit and to receive power determines how good communication link it can establish. This paper presents results from a comprehensive study on the radio performance, in terms of total radiated power (TRP) and total isotropic sensitivity (TIS), of 16 mobile terminals, common in the Nordic countries, in different use scenarios - free space, talk mode using right and left hand phantom next to head phantom, and data mode with right hand phantom. The phones are tested following the standardized non-invasive procedure for 2G, 3G and 4G communication standards. It is found that there is a large spread in the performance among the tested phones even in free space (up to 9 dB for TRP and up to 5 dB for TIS) and the case is more severe when the user is located next to the handset. The results indicate that the vicinity of the user to the mobile terminal can lead to degradation up to 22 dB in the transmit performance and up to 8 dB in the receive performance.

New design techniques of resistive bolometer system for analysis of total radiated power.

Two design techniques for the field of view (FoV) of a resistive bolometer system for the analysis of the total radiated power have been developed. The first technique is a new concept of the resistive bolometer system having multiple apertures to achieve a large viewing angle with one bolometer channel. The second technique is an optimization technique of the bolometer location in the major radial direction to minimize error of the analysis. Both techniques have been examined with a virtual tokamak device. By a FoV designed with both techniques, the total radiation power of several radiation profiles can be determined within 3% error of the analysis with one bolometer channel.

OTA Evaluation of Mobile Phone Antenna Performance for VoLTE [Measurements Corner

This article compares the over-the-air (OTA) performance of tradit ional voice service and voice-over LTE (VoLTE). We present the results of the OTA measurements of the antenna performance of 22 mobile phones commonly used over the last two years. VoLTE is a feature included in LTE that allows voice service to be delivered as data flows. Traditional studies on LTE include only data service and, therefore, OTA for data service, which is measured with the phone held in the browsing position only by the hand, whereas VoLTE uses the same data channel but with the device held next to the head by a hand. Traditional studies on voice service include only OTA in voice service. The figures of merit (FoMs) taken into account for ranking the devices were the total radiated power (TRP) and the total isotropic sensitivity (TIS), which are related to the transmitter and receiver antenna performance, respectively. Our investigation includes results for talk mode using left- and right-hand phantoms next to the head to calculate the maximum power radiated by the transmitter. To evaluate the sensitivity of the receiver, we considered the performance in talk mode using a right-hand phantom next to the head as well as in data mode using only the hand phantom.

A Substituted Method for TRP Measurement

OTA (Over-the-Air) measurement was carried out on a smart phone for several typical configuration, a substituted method was developed to execute the TRP (Total Radiated Power) test, the TRP results of Bluetooth and Wi-Fi were analyzed that could proven the validation of the new method.

Reduction of EMI Due to Common-Mode Currents Using a Surface-Mount EBG-Based Filter

Common-mode (CM) noise on differential signals can be suppressed by planar electromagnetic bandgap (EBG) technologies. In this study, two new CM filter structures were designed, fabricated, and measured. The filters are based on a previously proposed geometry, a “sandwich-type” EBG structure that resonates at the desired filter frequency; however, the new filters are placed on the top of the PCB as a surface-mount component, instead of being implemented within the PCB stackup. Stripline and microstrip versions of the surface-mount filter are considered. The filters can be easily removed and substituted with another one that is designed to filter a different frequency but maintains the same footprint and external dimensions. In addition, the surface-mount filter allows us to incorporate dc blocking capacitors into the microstrip version of the filter, thus providing two functions in one package. The total radiated power (TRP) of the implemented filter is investigated and discussed. RF absorbing material and traditional shielding are considered to reduce the TRP.

Fast Method for OTA Performance Testing of Transmit–Receive Cofrequency Mobile Terminal

This paper provides a novel method for measuring of a wireless user equipment, when the equipment uses the same frequency for both transmitting and receiving. The proposed method is based on the fact that the total radiated power (TRP) and the total isotropic sensitivity patterns are complementary for transmit–receive cofrequency mobile terminals. Thus, the proposed method only requires a full TRP test and an accurate efficient isotropic sensitivity test to complete a total OTA performance measurement, resulting in improved test accuracy and decreased measurement time compared to the traditional test method defined in the OTA testing standard. The proposed method is suitable for OTA testing of transmit–receive cofrequency and single-input single-output radio systems, such as cellular communication, Wi-Fi, ZigBee, and Bluetooth.

Estimating and Reducing Uncertainty in Reverberation-Chamber Characterization at Millimeter-Wave Frequencies

This contribution provides techniques for accurately characterizing uncertainty when measuring total radiated power (TRP) at millimeter-wave frequencies. The setup is based on the reverberation chamber as a well-known measurement environment capable of performing TRP measurements of wireless devices. We show that by applying various stirring techniques, we can reduce the random component of measurement uncertainty to around 2%. We use a model for estimating the uncertainty for TRP measurements based on the $K$ factor, which is compared with uncertainties calculated from relative power measurements and we show excellent agreement. We perform a significance test to confirm that the uncertainty due to the limited number of mode-stirred samples dominates over the uncertainty due to the lack of spatial uniformity. The observed uncertainty is also compared with an ideal chamber situation and shows good agreement.

MIMO OTA test for a mobile station performance evaluation

The antenna is one of the most important components of mobile stations, since antenna design has a significant effect on mobile station performance and the end user's experience. The industry therefore needs effective test methods to evaluate the mobile station's overall radiated end-to-end performance. Traditional receiver testing used cabled signals which bypass the antennas, but over the air (OTA) testing evaluates the device's overall radiated performance, including the impact of the antennas. Conformance tests for single antenna devices have been in existence since 2001. These tests measure the total radiated sensitivity (TRS) of the receiver and the total radiated power (TRP) of the transmitter. TRS is also known as total isotropic sensitivity (TIS).

EMI Coupling Paths and Mitigation in a Board-to-Board Connector

Cage connectors for optical subassembly I/O modules have been identified as one of the main coupling paths in an optical link at the front-end of switches and routers. In the study presented herein, the simulation model used to study electromagnetic interference coupling physics and mitigation of the optical cage connector was corroborated by comparing the measured and simulated results for the total radiated power (TRP). Currents on the adjacent ground references to the differential signal conductors caused half-wave resonant peaks in the TRP response in the frequency range of 4–18 GHz. At frequencies from 18 to 28 GHz, both full-wave simulation and analytical formulas indicate that the radiation results primarily from the currents on the signal traces. The radiation from the optical cage connector was suppressed with absorbing materials, and the coupling path was verified, together with the optical cage and module enclosure.

COMPACT PRINTED DIVERSITY ANTENNA FOR LTE700/GSM1700/1800/UMTS/WI-FI/BLUETOOTH/LTE2300/2500 APPLICATIONS FOR SLIM MOBILE HANDSETS

A planar, printed multiple-input multiple-output (MIMO) antenna for slim mobile handset is presented. The dual-antenna system, comprises two symmetric antenna elements, is printed on a printed circuit board (PCB) of mobile phone. Each antenna element consists of coupled-fed loop antenna. The loop antenna is formed by a quarter wavelength (at 762MHz) meandered loop strip with end terminal short-circuited to the ground plane. A T-shaped protruded ground is deliberately designed to enhance the impedance matching and decoupled the two closely deposed antenna elements (distance between antenna elements are 0.03λ at 762MHz). The integrity of the T-shaped decoupling structure and coupled-fed loop antenna array covers LTE700 (0.747GHz–0.787 GHz) and WWAN (1.7GHz– 3.04GHz) based on −6 dB reflection coefficient and achieves isolation between elements well below −10 dB over all the operating bands. The application platform is LTE700, GSM1700, GMS1800, UMTS, Wi-Fi, Bluetooth, LTE2300, and LTE2500 bands for the 2G/3G/4G mobile terminals. The effect of user proximity by considering the actual mobile environment is also studied in the form of total radiated power (TRP), specific absorption rate (SAR), diversity performances, and radiation performances. Finally, a prototype is fabricated and tested with network analyser. The measured results are found in good agreement with simulated ones.

Wearable Fabric Reconfigurable Beam-Steering Antenna for On/Off-Body Communication System

This paper presents a comparison of on-body performances between omnidirectional (loop antenna) and reconfigurable beam-steering antennas. Both omnidirectional and reconfigurable antennas were manufactured on the same fabric substrate and operated at the frequency band of the WLAN 802.11a (5.725–5.85 GHz). The reconfigurable antenna was designed to steer the beam directions. In order to implement the beam-steering capability, the antenna used two PIN diodes. The maximum beam directions of three states (states 0, 1, and 2) were steerable in theYZ-plane (h=2°, 28°, and 326°, resp.). The measured peak gains were 5.9–6.6 dBi and the overall half power beam width (HPBW) was 102°. The measured results of total radiated power (TRP) and total isotropic sensitivity (TIS) indicated that the communication efficiency of the reconfigurable beam steering antenna was better than that of the loop antenna. When the input power was 0.04 W (16 dBm), the simulated specific absorption rate (SAR) values of the reconfigurable beam steering antenna on the body were less than 0.979 W/kg (1 g tissue) in all states, satisfying the SAR criteria of the US.

Application of the SAROTA index in real-life scenario

A unique parameter referred to as the SAROTA index which accounts for both the specific absorption rate (SAR) and the over-the-air (OTA) performance of a mobile phone was previously proposed to characterize the real-life exposure. The applicability of the SAROTA index was confirmed using SAR and total radiated power (TRP) data obtained under laboratory conditions wherein the power control (PC) enforced on the mobile phone was implemented artificially. Herein the investigation is extended to measurements conducted for the speech mode of operation in real-life scenarios. Based on the actual PC implemented during the communication with the base station, the instantaneous and average real-life exposure experienced by the mobile phone user is analyzed and compared to the predicted SAROTA index. To capture the PC in real-time, a set of hardware modified phones with embedded network monitoring software are used. The instantaneous uplink transmit power level (TX_LEV) along with various downlink parameters such as the receive signal level (RX_LEV) and received signal quality (RX_QUAL) of the communication link are thus available for performing a comprehensive RF exposure analysis.

Thermal and EMI Performance of Composite Plastic Molded Heat Sinks and Hybrid TIM Materials

Heat sinks are widely used in thermal management of electronics. However, it is also well established that a heat sink can couple and radiate electro-magnetic (EM) energy from the same component that it is cooling. As the frequency of these devices continues to increase, it is more crucial to try to suppress the EM radiation at the source. The component suppliers for thermal management and EMI products have been developing materials that are thermally conductive and also have EM absorbing properties. The thermal and EMI material properties of the additives can change the properties of the final material and they may not always be complementary between thermal and EM absorbing behaviors. In this paper, two such hybrid solutions are investigated to understand the thermal and EM absorbing characteristics and interactions. These are: (1) heat sinks made of composite plastic materials; and (2) hybrid RF/thermal interface materials (HRTIMs). For the heat sink study, three heat sinks of the same physical design (40mm square x 8.25mm tall) but with different materials are tested and analyzed. Two of the heat sinks are molded from two different composite plastics (Materials A and B), while the third one is constructed from aluminum and used as the baseline heat sink for comparison. The results presented in Figure 7 show EMI improvement for composite material heat sinks over the traditional aluminum heat sink. Material A provides a broadband reduction of 2–3 dB power whereas Material B heat sink provides significant reduction at lower frequency range of 1–8 GHz. The thermal performance results are plotted in Figure 11 – Figure 14, and the results show that the composite plastic materials are more suitable for applications that have lower power and power density. For the HRTIMs, two different base materials at different thicknesses are investigated and the material details are given in Table 2 . Similar to the heat sink EMI study, Total Radiated Power (TRP) measurements are performed for the HRTIMs in an Electromagnetic Reverberation Chamber in the frequency range of 5–40 GHz show improvement for material TIM 1. The EMI results are plotted in Figure 9 and Figure 10. For thermal performance characterizations, an ASTM D-5470 compliance test stand (Figure 6) is used. The thermal impedance results of these materials are plotted in Figure 15.