Bit Error Rate Performance of Quadrature Modulation Transmission Using Reconfigurable Frequency Selective Surfaces

A low-complexity radio transmitter is implemented and evaluated using a novel direct antenna modulation (DAM) technique incorporating a reconfigurable antenna. The antenna uses reconfigurable frequency selective surfaces (FSS) to directly phase modulate a radio frequency carrier wave with a quadrature phase shift keying (QPSK) modulation. A hardware-in-the-loop demonstration of the transmitter in a single in single out (SISO) communications system has been developed. To achieve a BER of 10−4 the proposed system required only 4dBm extra transmit power compared with instrument grade transmission

Frequency Selective Surface Loaded Antenna for Direct Antenna Modulation

A reconfigurable antenna loaded with Frequency Selective Surfaces (FSS) to achieve direct antenna phase modulation is presented and simulated. Placing FSS with integrated varactor diodes into a monopole-fed cavity allows control of the transmitted phase of a carrier signal with a bias voltage. As such, Direct Antenna Modulation (DAM) can be achieved, producing a phase modulator that can be included in a low complexity transmitter. Simulation shows such an antenna can achieve QPSK modulation with between 3.5dB and 4.5dB magnitude variation between constellation points with acceptable phase stability with radiation angle in the antenna 3dB beamwidth

Measurement and Prediction of Pressure Drop in Pneumatic Conveying: Effect of Particle Characteristics, Mass Loading, and Reynolds Number

This paper reports the effect of Reynolds number, mass loading, and particle shape and size on pressure drop in a vertical gas-solids pneumatic conveying line. We isolate the effect of one variable while holding all others constant. A commonly used pressure drop correlation and a state-of-the-art multiphase computational fluid dynamics (CFD) models are then assessed by comparing their predictions to experimental data. Deficiencies in the models and the correlation are identified, and possible modifications are proposed. The most notable deficiency is the inability of both the experimental correlation and the CFD model to accurately predict the pressure drop for gas-solids flow with highly aspherical particles

Neurological complications following extrusion of sodium hypochlorite solution during root canal treatment.

AIM: To report the presentation and management of two cases with neurological complications secondary to the extrusion of sodium hypochlorite solution into the facial soft tissues during root canal treatment. SUMMARY: The clinical features, with particular emphasis on nerve deficit following inadvertent extrusion of sodium hypochlorite, are discussed and its management highlighted. Early and aggressive treatment is advocated following such incidents in order to reduce potentially serious complications. KEY LEARNING POINTS: *Neurological sequelae can follow inadvertent hypochlorite extrusion. *Early recognition may avert a potentially more serious outcome. *Active hospital treatment including intravenous steroids and antibiotics is recommended

A system‐level performance evaluation of a reconfigurable filtenna in the presence of in‐ and out‐of‐band blockers

Direct RF sampling has been suggested as a solution for receivers that are flexible in frequency and across standards, while utilising only a single radio frequency front-end. However there are concerns about their robustness in the presence of out-of-band and in-band blockers. Tunable filtennas offer a solution to this, incorporating filtering into the antenna space while providing rejection of unwanted signals. This paper presents a filtenna containing reconfigurable frequency selective surfaces to provide tunable filtering between 1.44 and 1.95 GHz. The filtenna is characterised as an antenna and a filter, showing minimum 18 dB rejection across the principle beamwidths. It is then implemented in a direct RF sampling receiver and is shown to provide sufficient rejection of blockers to cause no degradation in the received error vector magnitude (EVM) and block error rate (BLER) of LTE signals when subject to 5G NR-compliant blocking signals. The in-band blocker performance is also characterised, showing at most 3 dB degradation in EVM and BLER

Direct antenna modulator for m-QAM applications

This paper introduces a concept for direct antenna modulation using a metasurface based antenna. The antenna can be controlled with the use of an external bias to control both the amplitude and phase of the transmitted signal, in a continuous way, to provide m-QAM direct antenna modulation. The DAM comprises of five metasurfaces, four of which control the transmitted phase through the use of a varactor diode, and the fifth uses a PIN diode to control the transmitted phase. Numerical simulations are presented which show that the transmitted phase can be varied over a 360° range with a amplitude dynamic range of 25dB

Metasurface direct antenna modulators in non-line of sight channels for the Internet of Things

A Direct Antenna Modulation (DAM) transmitter is modelled in wideband channels using Direct Sequence Spread Spectrum (DSSS) as a low-cost, low-complexity solution for the Internet of Things (IoT). Metasurface-based DAM is an emerging technique where a baseband signal is modulated directly onto a radio frequency (RF) carrier wave using a reconfigurable metasurface. This technique removes the requirement of the power amplifier (PA) to amplify complex modulated signals, allowing the use of a simple, energy efficient PA to amplify only the carrier wave. The reduction in power consumption and RF electronics makes DAM an attractive low-cost, low-complexity transmitter technology. This paper discusses the use of a DAM transmitter as an IoT access point transmitter using DSSS to overcome broad-band fading and mitigate the systematic distortion inherent in the technique. Simulation shows DAM to have negligible impairment in 3GPP urban channels compared with ideal modulation when balanced spreading codes are used

Concurrent multiband direct RF sampling receivers

Direct radio frequency (RF) sampling receivers are investigated for use in concurrent multiband reception for mobile broadband (MBB) applications. The recent proliferation of different frequency bands and standards in wireless communications has allowed large increases in mobility and throughput, but the number of receivers in a device is limited by physical space and power consumption. Software Defined Radio (SDR) is increasingly being explored to reduce the number of analog RF components required. This paper examines the use of direct RF digitization, allowing tunable and concurrent reception of multiple bands with a single RF front-end. Full mathematical models of both Nyquist and subband sampling receivers are presented and used to investigate a quadband LTE receiver, which is modeled in Simulink and implemented in a hardware-in-the-loop (HWIL) testbed. Individual bands are simulated to have at worst -95dBm sensitivity for 16-QAM with Nyquist sampling and -83dBm with subband sampling. Desensitization of the receivers due to multiband processing is evaluated theoretically and experimentally, showing a maximum of 3dB degradation, which is within the LTE standard for adjacent band interference

The effect of ADC resolution on concurrent, multiband, direct RF sampling receivers

Connectivity using interband frequencies in 4G and 5G radio access networks, for example, carrier aggregation or dual-connectivity, incurs high receiver complexity and power consumption, in particular, when implemented using multiple radio units. Employing concurrent, multiband, direct RF sampling in a single radio chain architecture reduces the RF component count, leading to lower receiver complexity and power consumption. For this architecture, as the composite signal from multiple concurrent bands is digitized by a common analog-to-digital converter (ADC), the bit resolution critically affects system performance. In this paper, the effect of ADC resolution on the error vector magnitude (EVM) and Block Error Rate (BLER) performance of a concurrent, multiband, direct RF sampling receiver is investigated. Simulation and hardware measurement of a tri-band Long Term Evolution (LTE) system supporting three simultaneously active channels at 888 MHz, 1.92 GHz and 2.52 GHz is evaluated when reducing the ADC resolution from 8 to 3 bits. Interband interference measurements demonstrate that the multiband, direct RF sampling, wideband LTE receiver remains 3GPP compliant at 4-bit ADC resolution with the signal-to-noise-ratio (SNR) desensitization over a single-band receiver limited to 9 dB in the 888 MHz band

Tri-band single chain radio receiver for concurrent radio

The bandwidth available for improving throughputs to future mobile devices at sub-6 GHz frequencies can be increased through aggregating multiple non-contiguous bands, which may be using the same or different radio access technologies to transmit information. However, with conventional radio technology, a complete radio frequency (RF) chain is required for each band, limiting the possible increase due to space and energy consumption restraints in the mobile station (MS). This paper presents and measures a single RF chain radio for concurrent reception of three non-contiguous bands transmitting 16-QAM LTE signals, using a tunable analogue front-end and software defined radio (SDR) techniques. The receiver sensitivity is degraded by only 6dB under worst-case concurrent reception, compared with reception of a single band. This demonstrates that complex signaling techniques can be received concurrently with a single radio chain while meeting the 3GPP standards, opening the way to compact, efficient, multiband receivers for future standards