The use of a tunable power splitter (PS) as a constituent component of a simultaneous wireless information and power transfer (SWIPT) system is discussed. Two varactor diodes are used to achieve a tunable output power ratio P₂ : P₃ varying from 1 : 1 to 1 : 10 under good matching conditions. The SWIPT system that operates at 2.4 GHz consists of a typical patch antenna, cascaded with the tunable PS, and a voltage doubler rectifier. The constituent components were implemented and tested as stand-alone devices and were subsequently combined in a measurement system using interconnectors. The effect of the tunable PS was explored with respect to the SNR measurements on the port that is intended for the information decoding receiver and the DC voltage measurements on the termination load of the rectifier that is connected directly on the energy harvesting port of the tunable PS. A spectrum analyzer is used for the SNR measurements while the input power is controlled using a signal generator. Both wireless power transmission and on-board measurements verify that the harvested energy can be maximized by using the minimum SNR at the information decoding branch at the expense of DC power consumption required for the biasing of the varactor diodes.

Parasitic antenna arrays (PAAs) with a single radio frequency (RF) chain have been used to enable new trends and paradigms for multi-antenna transmission [1]. Significant reduction in hardware complexity, size and cost can be obtained with single-RF PAAs, as only the active element (AE) is directly connected to the voltage through an RF connection. The performance of a PAA can be further enhanced for multi-antenna transmission by increasing its number of active elements, thus creating a multi-active / multi-passive (MAMP) antenna array. The problem of finding the desired tunable loads for parasitic elements (PEs) involves ensuring that the array will radiate. In this letter we provide (for the first time, to our best knowledge), closed-form expressions for the constraints that the parasitic load values of MAMP antenna arrays need to satisfy for the array to radiate.

This article is about better wireless network connectivity. The main goal is to provide wireless service to several use cases and scenarios that may not be adequately covered today. Some of the considered scenarios are home connectivity, street-based infrastructure, emergency situations, disaster areas, special event areas, and remote areas that suffer from problematic/inadequate network and possibly power infrastructure. A target system that we consider for such scenarios is that of an energy-efficient self-backhauled base station (also called a “portable access point—PAP”) that is mounted on a drone to aid/expand the land-based network. For the wireless backhaul link of the PAP, as well as for the fronthaul of the street-mounted base station, we consider newly built multi-active/multi-passive parasitic antenna arrays (MAMPs). These antenna systems lead to increased range/signal strength with low hardware complexity and power needs. This is due to their reduced number of radio frequency chains, which decreases the cost and weight of the base station system. MAMPs can show a performance close to traditional multiple input/multiple output (MIMO) systems that use as many antenna elements as RF chains and to phased arrays. They can produce a directional beam in any desired direction with higher gain and narrow beamwidth by just tuning the load values of the parasitic elements. The MAMP is designed based on radiation conditions which were produced during the research to ensure that the radiation properties of the array were good.

Millimeter-wave communications at 60 GHz offer access to large contiguous spectrum but require accurate propagation models to support reliable system design, as path losses at these frequencies are strongly influenced by buildings, vegetation, balconies, and intervening obstacles. This paper presents path gain models for outdoor-to-balcony and outdoor-to-indoor fixed wireless access (FWA) links at 60 GHz, derived from an extensive measurement campaign conducted in Athens, Greece. Measurements were collected with a street-mast transmitter and receiving nodes placed on balconies or indoors, covering a range of non-line-of-sight (NLOS) geometries representative of residential FWA deployments. Two existing channel models are adapted, tested and shown to predict measured path gain with lower RMS error than existing 3GPP models. Link-budget calculations using the proposed models show that, under the stated assumptions, 60 GHz FWA can deliver gigabit-class service to balcony-mounted receivers at short residential ranges with a 400 MHz deployment bandwidth.