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Radio frequency (RF), microwave, and millimeter-wave (mmW) multiport interferometric receivers present a competitive solution for the front-end reception of low-power multistandard and multifunction wireless applications. The systematic generation of rectified waves in a conventional direct-conversion interferometric receiver is highly related to temporal and power changes and the number of subsignals in the frequency band of interest. It can cause the receiver to saturate and, thus, requires auxiliary power-hungry tunable amplifiers and a data converter for compensation. This work presents a heterodyne detection in an RF/microwave interferometric receiver, the first of its kind, which separates the desired frequency signals from the rectified wave components with two output ports through a frequency offset. This architecture also makes use of the field-effect transistor (FET)-based power detectors to combine the received and reference signals, which reduces a theoretical multiport junction loss of 6 dB to 3 dB. In this way, the proposed receiver is set to support the development of an ultralow-power concurrent dual-band wireless system using a single wave-correlator circuit. A mathematical model of the proposed system is derived and subsequently prototyped using off-the-shelf components to evaluate its carrier-to-noise power ratio (CNR) and error vector magnitude (EVM) performances, which can be extended for integrated circuits (ICs) implementation, such as CMOS and III–V ICs. The power detectors only require a bias voltage at gate terminals with zero direct current (dc) power consumption for optimum voltage responsivity and CNR performances. The demodulation of various modulated digital signals, including QPSK, QAM-16, QAM-32, and QAM-64, has been successfully demonstrated in the 24- and 28-GHz mmW frequency bands at 4 MSps of the symbol rate with a maximum EVM of 11.43% root-mean-square (rms) free from any postprocessing linearization and calibration.

A self-embedded power-recycling technique in microwave mixers is proposed and presented for radio frequency (RF) and microwave multiple-input multiple-output (MIMO) systems. The novelty of the proposed power-recycling technique stems from a distinct concept of harnessing direct current (dc) signal rectified by mixing elements in the course of a frequency translation. The large-signal model of a nonlinear mixing element coupled with electromagnetic simulations is used to understand and examine the contribution of the dc signal in the overall transceiver energy efficiency. A single-balanced (SB) diode-switching mixer integrated with a diplexer bank is prototyped using off-the-shelf components to validate the power-recycling technique, which can be extended for an IC implementation. The measurement results show that about 30% of the driving signal power is directly present in the form of a dc signal at the power-recycling port under the maximum conversion efficiency condition. Furthermore, wide linear instantaneous bandwidth performance is shown with a resistive termination of sum–product signal in a downconverter.

A low-IF interferometric receiver architecture is proposed and implemented by eliminating two output ports of a conventional calibration-based six-port discriminator to further simplify the structure, and reduce its power consumption and cost in the context of massive internet-of-things (IoT) applications. The costly power-consuming high-speed analog-to-digital converters (ADCs) are thus reduced to a half. A theoretical analysis is presented to formulate an analytical procedure to benefit from a low intermediate frequency (IF) principle and regenerate baseband signals with two observations without any constraint on the input signal and error rate performance of a wireless node. A prototype is implemented in the 24 GHz frequency band and various modulations including QPSK, QAM-16 and QAM-32 have been successfully studied and demonstrated at 1 MSps of symbol rate with maximum error vector magnitude of 7.94 % rms free from a post-processing linearization and calibration. The maximum data rate is fundamentally limited by power detectors which are linked to their rise time.

In the mining industry, communication systems are important for ensuring personnel safety and optimizing the mining processes underground. The need for through-the-air (TTA) in the underground mining industry has been evolved from man-to-man, man-to-machine and machine-to-machine real-time voice, video and data transmission. Reliable communication has always been a challenge in the underground environment due to harsh and dynamic conditions. This article surveys the effect of tunnel geometry and antenna parameters on TTA communication system performance in underground mines. It provides a comprehensive review of measurement campaigns that have been published to date by systematic organization of literature. The open research areas for future investigation are also discussed. Finally, digital system’s findings in the University of Witwatersrand (WITS) mock-mine are presented.

A methodology of modelling and characterizing the latency contribution of front-end architectures to next-generation mobile networks is proposed and presented. An appropriate definition of this term for microwave engineering is given on the basis of a brief literature survey. Electromagnetic simulations and signal processing techniques are used to understand and formulate an analytical procedure to examine the latency contribution of wireless transceivers. Measurement results show that typical homodyne and six-port receiver architectures produce delays in the range of nanoseconds, which may be of significant interest for future ultra-high speed RF-interconnects (RF-I) and wireless massive data transfers whereas the overall latency target in 5G networks is in the range of milliseconds.

A low-power receiver architecture is introduced and studied for simultaneous wireless information and power transfer (WIPT) applications. The concept of WIPT is developed for energy-constrained wireless nodes without compromising the information receiver performance characteristics and the use of digital modulation techniques for 5G-oriented internet-of-things (IOT). With a diplexer-based six-port receiver, it is found that dedicated wireless power transfer is realizable along with simultaneous wireless information transfer. A multiport power recycling method is also deployed which exploits the unwanted harmonic signals generated by power detectors and signal interferers.

When the crown pillar at Lily mine collapsed on 5 February 2016, a lamp-room in a container on surface was engulfed in the sinkhole that formed, trapping three miners who were in the lamp-room at the time. In situations like this, it is imperative to locate and rescue the missing miners before the window of opportunity to find them alive closes. The Wits Mining Institute (WMI) at the University of the Witwatersrand was requested to assist with suggestions, and a conceptual study was undertaken to identify techniques that were likely to be successful. Several techniques that have the potential to locate the position of the container were identified, but the typical noise in the form of steel objects, mine cavities, and a combination of broken and solid rock in a complex geographical and geomechanical environment will pose significant challenges.