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This work proposes a microwave angular displacement sensor with wideband matching based on a wideband impedance transformer. According to the design requirement of the microstrip impedance transformer (load‐to‐source impedance of 250‐to‐50 Ω, centre frequency of 2.40 GHz) with Chebyshev frequency response, the proposed angular displacement sensor is explored for the high bandwidth sensitivity of 11.18 MHz/degree. [ABSTRACT FROM AUTHOR]

This article proposes and presents an innovative approach to realizing the concurrent dual-band transmission with only a single front-end and local oscillator at radio frequency (RF). Fundamentally, the proposed concurrent dual-band front-end is based on the conventional multiport interferometric architecture for single-band operation. Nevertheless, the conventional variable loads are replaced by diode networks with IF input signals to produce the RF signals at their designated center frequencies. Furthermore, due to the linear characteristics of a multiport network, the signals with different data contents will be mixed into both RF channels. To this end, an inverse matrix operation is applied to reversely convert the original data streams before the modulations of IF input signals. As a result, the two original data streams can be effectively modulated into specific RF channels (for transmission) with minimal interchannel interferences based on this configuration. In addition to the theoretical analyses, this innovative concurrent dual-band transmitting front-end has been investigated and verified with $M$ -quadrature amplitude modulation (QAM) signals in simulations and experiments. All outcomes demonstrate excellent performances in concurrent dual-band transmission with significant reductions in both size and biasing power. [ABSTRACT FROM AUTHOR]

This article presents a compact, low-power, yet efficient wireless sensing platform to detect the angular displacement of an object with a reoriented complementary split-ring resonator (RCSRR). This RCSRR sensor belongs to the CSRR family, consisting of a 90° feedline on the stator and slots on the rotor. The reflected signal of the sensor experiences a monolithic phase response to the angular displacement because of its asymmetricity. In the platform, the sensor acts as a variable load of the multiport interferometer. The multiport converts the reflected signal into dc voltage readouts representing the real and imaginary parts of the phase of the reflection coefficient. Moreover, this platform operates at a fixed frequency (i.e., 2.4 GHz), and it requires only a biasing power as low as −30 dBm. This platform prevents ponderous system architecture and power consumption. This innovative wireless sensing platform has been designed, implemented, and tested. The experimental results show good agreement with their theoretical counterparts, and the standard deviation of angular displacement uncertainty is only $10^\prime $. [ABSTRACT FROM AUTHOR]

A distinct usage of the conventional multiport architecture is introduced in this work to explore the compendious scheme of a concurrent dual-band interferometric receiver. Dual RF signals at individual frequency channels are received simultaneously, and only a single low-power local oscillator (LO) source is deployed for frequency translation or conversion to the same intermediate frequency (IF) band. Although these signals are spectrally overlapped, they can be extracted with a simple and efficient algorithm with good channel-to-channel isolations. Compared to the conventional multiport configuration, the power detectors are replaced by analog-to-digital converters (ADCs) to process the signals in this proposed scheme. The underlying physics of the concurrent receiving operation is explained and derived analytically. Some experiments are also presented to investigate various performance indexes, including signal linearity, noise behavior, interchannel interference, and so forth. Lastly, multiple $M$ -quadratic-amplitude modulation (QAM) signals are applied to evaluate the communication behavior of the proposed receiver architecture. Distortions due to frequency drift, channel imbalance, and in-phase and quadrature (IQ) imbalance are studied, and bit-error-rates (BER) are measured and compared with their theoretical counterparts. All obtained results confirm that the proposed interferometric receiver provides good communication performances. [ABSTRACT FROM AUTHOR]

This paper presents the concept and demonstration of harmonic diversity for wireless communication, which makes use of multiple harmonic radio frequency (RF) channels with respect to the carrier frequency. Rather than frequency and space diversities widely used today to improve multipath fading, signal quality and spectral efficiency, the proposed scheme does not require multiple RF transceiver front-ends. The advantages of inherent RF device nonlinear characteristics are harnessed to produce and process harmonics within single transceiver. Even though distinct harmonic channels will exhibit different order of phase shifts, the analysis shows that such phase offsets can be compensated by adjusting the phase of local oscillator (LO) at receiver end. Extending the framework of the Shannon theorem, an M-channel harmonic communication system is shown to reduce the minimum required signal-to-noise ratio (SNR) at the input of receiver by M-times. In addition, this work indicates that the power consumption of transmitter can be significantly reduced up to 66% than the conventional ones. Through the analysis of channel capacity, the harmonic system is proved to outperform the single channel counterpart especially when SNR is low. To validate the correctness of the proposed concept, a series of experiments are carried out to emulate the developed theoretical models. For instance, a three-channel harmonic communication system is prototyped, involving certain RF harmonic components designed for demonstration. The retrieved signal strengths are examined with different phase setting of receiving LO, and various modulation techniques are applied for estimating the system performances. All measured results are in agreement with their simulated counterparts, thereby demonstrating the correctness and usefulness of the proposed theories and techniques for nonlinear communication systems of harmonic diversity. [ABSTRACT FROM PUBLISHER]

In this communication, a novel highly integrated antenna-triplexer on a two-layer printed circuit board is proposed for multiband communication systems. This integrated three-port component operated at triple frequency bands (0.85, 1.65 and 2.45 GHz) simultaneously utilizes a single slot antenna and its rectangular loop as the radiating elements. Good three-port isolations are achieved by the multi-mode excitations including even, odd and bi-directional modes. These modes are intrinsically orthogonal and therefore the isolations are guaranteed. Compared with the conventional counterparts that use additional bandpass filters to assure the port isolations, the proposed antenna-triplexer preserves the simplicity and compactness of the antenna itself, and it is suitable for the practical portable applications. To demonstrate the significance of this new antenna-triplexer, a prototype measured with compact size is implemented and the experimental results show the good agreements with the simulations. The antenna gains of 0.85, 4.00 and 4.23 dBi are obtained and an average isolation in three ports is as good as 22.7 dB at operating frequencies. [ABSTRACT FROM PUBLISHER]

This paper describes a ZigBee-based wireless sensor network node for the ultraviolet (UV) detection of flame. The sensor node is composed of a ZnSSe UV photodetector, a current-sensitive front end including a high-gain current-to-voltage amplifier with 120 dB and a logarithm converter, and a transceiver operated at a 2.4-GHz industrial, scientific, and medical band. A passive photodetector is designed to have a cutoff at 360 nm and convert the UV emission of flame into picoamperes. Including mixed signal processing and ZigBee transmission, the speed of flame detection is as fast as 70 ms. The sensor node consumes only an average of 2.3 mW from a 3.3-V supply. The performance of a prototype sensor node was verified when the luminous flame was imaged onto the sensor node with different angles ranging from -30^\circ to 30 ^\circ and distances of 0.1, 0.2, and 0.3 m enabling effective fire safety applications. [ABSTRACT FROM PUBLISHER]

In this paper, a new capacitively stepped-impedance resonator (CSIR) is proposed to develop the microstrip square-loop dual-mode bandpass filter. Using this new design, simultaneous size reduction and spurious response suppression for the dual-mode bandpass filter can be achieved. An analytical formulation of this novel resonator is given in order to elucidate the spurious frequencies relocation design. Together with this formulation, a generalized dual-mode bandpass filter model is developed so as to ease the analysis of transmission zero and insertion loss. A prototype filter is designed at 900 MHz with 1.5% fractional bandwidth. Significant spurious suppressions up to 33 and 35 dB are measured at 1.8 and at 2.7 GHz, respectively. A circuitry size reduction of 54% is achieved when compared with that of the conventional structure. Moreover, the CSIR allows frequency tuning and, thus, a varactor-tuned filter is designed and a measured tunable center frequency between 1.5-1.62 GHz is demonstrated. Utilizing the proposed structure, not only size reduction, as well as spurious response suppression, but also center frequency tuning can be achieved. [ABSTRACT FROM AUTHOR]

A novel miniaturized parallel coupled-line bandpass filter with suppression of second and third harmonic frequencies is demonstrated in this paper. This new filter is based on the capacitive termination on the conventional parallel coupled line to achieve size minimization, while the spurious responses are eliminated by the over-coupling approach. These features offer the classical parallel coupled-line bandpass filter simultaneous compactness and wide stopband performance. The simulations and measurements of a 900-MHz prototype bandpass filter are presented. The measured results agree well with the simulation. Compared with the conventional parallel coupled-line bandpass filter, the measured second and third spurious responses are suppressed to --64 and --55 dB, respectively. In addition, the circuitry size of the prototype filter can be reduced up to 25 %. [ABSTRACT FROM AUTHOR]

A tilted bi‐sense circularly polarized (CP) antenna and its application for UHF radio frequency identification (RFID) system is proposed. A planar concial monopole working as the electric dipole is designed at first. When a shorting pin is added, a loop radiator would be generated, and thus a pair of orthogonally oriented complementary dipoles is realized. In this way, both right‐handed circularly polarized (RHCP) and left‐handed circularly polarized waves (LHCP) are generated simultaneously in tilted directions within one hemisphere. Then, closed‐form formulas are derived to reveal the tunability mechanism of bi‐sense property and provide a design guideline for system application. It is demonstrated that flare angle of conical monopole has a linear relationship and sine function to CP beam direction and 3‐dB axial ratio (AR) beamwidth, respectively. Finally, antenna prototypes are fabricated and tested for validation. It is also demonstrated that at the tilted direction of θ = ± 45°, a 3‐dB AR bandwidth of 4.9%, and gain up to 5 dB are realized. Comparing with conventional microstrip patch antenna, an enhanced reading range over 5 m can be obtained in the tilted range from 40° to 75° and − 75° to −40° in UHF RFID sytem application. [ABSTRACT FROM AUTHOR]