Novel Design of a High-gain and Wideband Fabry-Pérot Cavity Antenna Using a Tapered AMC Substrate

A high-gain and wideband electromagnetic bandgap (EBG) resonator antenna with a tapered artificial magnetic conductor (AMC) ground plane is presented. The proposed EBG resonator antenna is comprised of a frequency selective surface (FSS) superstrate with a strip dipole array and an AMC ground plane with tapered rectangular patches. The realized gain and the bandwidth of the antenna can be improved simultaneously by using the tapered AMC where the phase difference of the reflected waves from the patches with different length is within 180° and the destructive interference among them can be considerably reduced. The maximum gain is increased about 2∼3 dB and the bandwidth is improved about 2.5 times compared to when the uniform AMC is used.     

Development of Millimeter Wave Fabry-Pérot Resonator for Simultaneous Electron-Spin and Nuclear Magnetic Resonance Measurement

We report a Fabry-Pérot resonator with spherical and flat mirrors to allow simultaneous electron-spin resonance (ESR) and nuclear magnetic resonance (NMR) measurements that could be used for double magnetic resonance (DoMR). In order to perform simultaneous ESR and NMR measurements, the flat mirror must reflect millimeter wavelength electromagnetic waves and the resonator must have a high Q value (Q?>?3000) for ESR frequencies, while the mirror must simultaneously let NMR frequencies pass through. This requirement can be achieved by exploiting the difference of skin depth for the two frequencies, since skin depth is inversely proportional to the square root of the frequency. In consideration of the skin depth, the optimum conditions for conducting ESR and NMR using a gold thin film are explored by examining the relation between the Q value and the film thickness. A flat mirror with a gold thin film was fabricated by sputtering gold on an epoxy plate. We also installed a Helmholtz radio frequency coil for NMR and tested the system both at room and low temperatures with an optimally thick gold film. As a result, signals were obtained at 0.18 K for ESR and at 1.3 K for NMR. A flat-mirrored resonator with a thin gold film surface is an effective way to locate NMR coils closer to the sample being examined with DoMR.     

Injection-seeding and self-injection-seeding of gain-switched Fabry-Pérot laser diodes

We present a simple model which allows us to predict the spectral behaviour of gain-switched Fabry-Pérot (F-P) laser diodes submitted to a weak quasi-monochromatic cw (or pulsed) injection signal. Different experiments are reported for illustration, some of them being new. The model describes the competition between the injection-driven field and the spontaneousnoise driven field during pulse build-up. The relative amplitudes of the two fields are evaluated at the gains-witching time as well as the spectral content of the injection-driven field. Different types of modal selection are found depending on the injection conditions. In the case of cw injection, there is a wide range of injection frequencies leading to single-mode emission, but two-mode lasing is also predicted for lasers exhibiting strong intrinsic chirp. These results are confirmed in experiments carried out on a 1.5 μm Fabry-Pérot laser driven by different cw dfb injection lasers. In the case of pulsed injection, the laser behaviours are similar but the model also shows the influence of the pulsed-injection arrival time on the mode selection process. This is experimentally illustrated in the case of a pulsed 1.3 μm laser operated in self-injection, the injected signal resulting from a weak spectrally-filtered optical feedback.     

An Analysis of Near Field and Application of a New Comb-shaped Antenna for Radio Frequency Identification

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Design and analysis of an energy-efficient O-QPSK coherent IR-UWB transceiver with a 0.52° RMS phase-noise fractional synthesizer

This paper explores an energy-efficient pulsed ultra-wideband (UWB) radio-frequency (RF) front-end chip fabricated in 0.18-μm CMOS technology,including a transmitter,receiver,and fractional synthesizer.The transmitter adopts a digital offset quadrature phase-shift keying (O-QPSK) modulator and passive direct-phase multiplexing technology,which are energy-and hardware-efficient,to enhance the data rate for a given spectrum.A passive mixer and a capacitor cross-coupled (CCC) source-follower driving amplifier (DA) are also designed for the transmitter to further reduce the low power consumption.For the receiver,a power-aware low-noise amplifier (LNA) and a quadrature mixer are applied.The LNA adopts a CCC boost common-gate amplifier as the input stage,and its current is reused for the second stage to save power.The mixer uses a shared amplification stage for the following passive IQ mixer.Phase noise suppression of the phase-locked loop (PLL) is achieved by utilizing an even-harmonics-nulled series-coupled quadrature oscillator (QVCO) and an in-band noise-aware charge pump (CP) design.The transceiver achieves a measured data rate of 0.8 Gbps with power consumption of 16 mW and 31.5 mW for the transmitter and the receiver,respectively.The optimized integrated phase noise of the PLL is 0.52° at 4.025 GHz.