RESUMO
In this work, we propose a current-mode dielectric spectroscopy integrated circuit (IC) for the detection of liquids permittivity at microwave frequency range. The current-mode sensing scheme presents wideband operation with enhanced dynamic range compared to conventional voltage-mode sensing approach. A low intermediate frequency (IF) receiver architecture further provides better performances in flicker noise, dc offset, and harmonic mixing that degrade a sensor accuracy in zero-IF receiver architecture. Measured maximum conversion gain is 31.4 dB at 0.4 GHz RF frequency, while the 1dB-compression point ([Formula: see text]) is measured to be -8 dBm at 1 GHz RF frequency. The operation frequency of the proposed spectroscopy IC is from 50 MHz to 4 GHz according to 3 dB bandwidth. The permittivity measurements for propanol across the frequency range of 0.03-10 GHz are performed with root mean square (rms) permittivity error of 0.49. The dielectric spectroscopy IC is fabricated in 28-nm CMOS technology with active area of 0.5 mm × 0.2 mm only, while consuming 13 mW from a 1.2 V supply.
Assuntos
Espectroscopia Dielétrica , Micro-OndasRESUMO
A delta-sigma-modulated intermediate-frequency-over-fiber (IFoF) transmission system assisted by a correlative-level coding technique is proposed and experimentally demonstrated. Unlike conventional delta-sigma IFoF systems with multiple output levels to achieve higher signal quality or larger capacity, a correlative-level encoder is exploited as a second modulator preceded by the delta-sigma modulator. The encoder compresses the bandwidth of the delta-sigma modulated signal by creating a correlation between adjacent signal symbols. As a result, the sampling frequency of the delta-sigma modulator in the proposed system can be increased beyond the transmission bandwidth of the IFoF system, considerably improving the in-band signal quality and the transmission capacity over the conventional multi-level approach. This is because the quantization noise from the delta-sigma modulation in the proposed scheme is more aggressively pushed away from the signal bandwidth with the high sampling frequency. According to experimental results, the proposed link provides at least a 40% larger transmission capacity for similar in-band signal quality or 2.1% better average EVM performance for the same capacity than the conventional four-level pulse-amplitude-modulation delta-sigma IFoF systems.
RESUMO
Two ∆Σ-modulated digital radio-over-fiber (DRoF) transmission systems that employ a multi-pulse Manchester encoder are proposed and experimentally evaluated. With a two-step modulation process comprised of ∆Σ modulation and multi-pulse Manchester encoding, a high frequency replica or image of a ∆Σ-digitized analog communication signal can be transmitted without significant power loss. This is achieved by exploiting the spectral characteristics of the modified Manchester code. For comparative analysis, a conventional ∆Σ-modulation-based DRoF system is also evaluated. Based on the evaluation results, the proposed DRoF systems more significantly improve the reliability and flexibility of the RoF system by providing higher power margins or by making the DRoF system implementation more cost-effective and easier to perform on account of the low-frequency requirement for electronics and optical transceivers.
RESUMO
This paper proposes non-contact heartbeat sensor using LC oscillator for personal healthcare. The signals from chest and wrist are measured using LC oscillator and electrodes. The proposed sensor can detect human heartbeat signal without direct contact to skin and is readily a portable heartbeat monitoring sensor. The capacitive and inductive electrodes are addressed, which are key elements of the sensor circuit.
