Characterisation of an aperture-stacked patch antenna for ultra-wideband wearable radio systems

This paper presents, for the first time, the time-domain characteristics of an aperture-stacked patch antenna (ASPA) for ultra-wideband (UWB) wearable devices. The methodology of antennas characterization for UWB radio systems is also outlined. The antenna operates within the 3-6 GHz frequency band. Time- and frequency-domain characteristics of this antenna are presented in transmission mode (Tx), receiving mode (Rx) and for 2-antenna (Tx-Rx) system. The pulse driving the antenna has duration of 0.65 ns. In the Tx mode, pulses radiated in different directions of the H-plane have very similar shapes. Fidelity factors are as high as 91.6-99.9%. For 2-antenna system, pulses received in normal and end-fire-like directions have the fidelity of 69.5%. As it was found, antenna does not behave "reciprocal" comparing Tx and Rx modes. For normal propagation direction, radiated pulse is the 2nd derivative of the input waveform, but in the Rx mode, received pulse is the 1st derivative of the incident plane wave. This antenna can be used for transmission of short-pulses, even 0.65-1 ns in duration. It is also small (patch planar dimensions 32/19 mm) and compact. Microstrip configuration allows further integration of active devices on the same board. Taking into account above results we can say that ASPA is a good candidate for UWB non-invasive wireless body area network (WBAN) applications

External modulation method for generating accurate linear optical FMCW

Frequency modulation continuous wave (FMCW) lasers are key components in modern optical imaging. However, current intracavity modulation lasers do not exhibit low-frequency jitter rate and high linearity due to the inherent relaxation oscillations. Although this may be compensated in a direct modulation laser diode using an optoelectronic feedback loop, the available sweep speed is moderately small. In this letter, a special external modulation method is developed to improve the performance of FMCW. Since only the first sideband optical field is used during the entire generation process, phase noise is kept to a minimum and is also independent of the sweep speed. We demonstrate that the linearity and jitter rates do not deteriorate appreciably when the sweep speed is changed over three orders of magnitude, even up to the highest sweep speed of 2.5 GHz/ μs

Experimental Investigation Of Ultrawideband Wireless Systems: Waveform Generation, Propagation Estimation, And Dispersion Compensation

Ultrawideband (UWB) is an emerging technology for the future high-speed wireless communication systems. Although this technology offers several unique advantages like robustness to fading, large channel capacity and strong anti-jamming ability, there are a number of practical challenges which are topics of current research. One key challenge is the increased multipath dispersion which results because of the fine temporal resolution. The received response consists of different components, which have certain delays and attenuations due to the paths they took in their propagation from the transmitter to the receiver. Although such challenges have been investigated to some extent, they have not been fully explored in connection with sophisticated transmit beamforming techniques in realistic multipath environments. The work presented here spans three main aspects of UWB systems including waveform generation, propagation estimation, and dispersion compensation. We assess the accuracy of the measured impulse responses extracted from the spread spectrum channel sounding over a frequency band spanning 2-12 GHz. Based on the measured responses, different transmit beamforming techniques are investigated to achieve high-speed data transmission in rich multipath channels. We extend our work to multiple antenna systems and implement the first experimental test-bed to investigate practical challenges such as imperfect channel estimation or coherency between the multiple transmitters over the full UWB band. Finally, we introduce a new microwave photonic arbitrary waveform generation technique to demonstrate the first optical-wireless transmitter system for both characterizing channel dispersion and generating predistorted waveforms to achieve spatio-temporal focusing through the multipath channels

The SST Multi-G-Sample/s Switched Capacitor Array Waveform Recorder with Flexible Trigger and Picosecond-Level Timing Accuracy

The design and performance of a multi-G-sample/s fully-synchronous analog transient waveform recorder I.C. ("SST") with fast and flexible trigger capabilities is presented. Containing 4 channels of 256 samples per channel and fabricated in a 0.25 {\mu}m CMOS process, it has a 1.9V input range on a 2.5V supply, achieves 12 bits of dynamic range, and uses ~160 mW while operating at 2 G-samples/s and full trigger speeds. With a standard 50 Ohm input source, the SST's analog input bandwidth is ~1.3 GHz within about +/-0.5 dB and reaches a -3 dB bandwidth of 1.5 GHz. The SST's internal sample clocks are generated synchronously via a shift register driven by an external LVDS oscillator, interleaved to double its speed (e.g., a 1 GHz clock yields 2 G-samples/s). It can operate over 6 orders of magnitude in sample rates (2 kHz to 2 GHz). Only three active control lines are necessary for operation: Reset, Start/Stop and Read-Clock. Each of the four channels integrates dual-threshold discrimination of signals with ~1 mV RMS resolution at >600 MHz bandwidth. Comparator results are directly available for simple threshold monitoring and rate control. The High and Low discrimination can also be AND'd over an adjustable window of time in order to exclusively trigger on bipolar impulsive signals. Trigger outputs can be CMOS or low-voltage differential signals, e.g. 1.2V CMOS or positive-ECL (0-0.8V) for low noise. After calibration, the imprecision of timing differences between channels falls in a range of 1.12-2.37 ps sigma at 2 G-samples/s.Comment: 9 pages, 16 figures, 1 tabl

A Multi-CAP Visible-Light Communications System With 4.85-b/s/Hz Spectral Efficiency

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into m subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and m, where m = {10, 8, 6, 4, 2, 1} subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of m, respectively

Coherent modulation up to 100 GBd 16QAM using silicon-organic hybrid (SOH) devices

We demonstrate the generation of higher-order modulation formats using silicon-based inphase/quadrature (IQ) modulators at symbol rates of up to 100 GBd. Our devices exploit the advantages of silicon-organic hybrid (SOH) integration, which combines silicon-on-insulator waveguides with highly efficient organic electro-optic (EO) cladding materials to enable small drive voltages and sub-millimeter device lengths. In our experiments, we use an SOH IQ modulator with a {\pi}-voltage of 1.6 V to generate 100 GBd 16QAM signals. This is the first time that the 100 GBd mark is reached with an IQ modulator realized on a semiconductor substrate, leading to a single-polarization line rate of 400 Gbit/s. The peak-to-peak drive voltages amount to 1.5 Vpp, corresponding to an electrical energy dissipation in the modulator of only 25 fJ/bit

Experimental photonic generation of chirped pulses using nonlinear dispersion-based incoherent processing

“© 2015 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"We experimentally demonstrate, for the first time, a chirped microwave pulses generator based on the processing of an incoherent optical signal by means of a nonlinear dispersive element. Different capabilities have been demonstrated such as the control of the time-bandwidth product and the frequency tuning increasing the flexibility of the generated waveform compared to coherent techniques. Moreover, the use of differential detection improves considerably the limitation over the signal-to-noise ratio related to incoherent processing.The research leading to these results has received funding from the national project TEC2011-26642 ( NEWTON) funded by the Ministerio de Ciencia y Tecnologia and the regional project GVA PROMETEOII2013/012.Rius Mercado, M.; Bolea Boluda, M.; Mora Almerich, J.; Ortega Tamarit, B.; Capmany Francoy, J. (2015). Experimental photonic generation of chirped pulses using nonlinear dispersion-based incoherent processing. Optics Express. 23(10):13634-13640. https://doi.org/10.1364/OE.23.013634S13634136402310Yao, J. (2010). Arbitrary waveform generation. Nature Photonics, 4(2), 79-80. doi:10.1038/nphoton.2009.276Li, M., Azaña, J., Zhu, N., & Yao, J. (2014). Recent progresses on optical arbitrary waveform generation. Frontiers of Optoelectronics, 7(3), 359-375. doi:10.1007/s12200-014-0470-yCapmany, J., & Novak, D. (2007). 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Photonic Generation of Chirped Millimeter-Wave Pulses Based on Nonlinear Frequency-to-Time Mapping in a Nonlinearly Chirped Fiber Bragg Grating. IEEE Transactions on Microwave Theory and Techniques, 56(2), 542-553. doi:10.1109/tmtt.2007.914639Chi, H., & Yao, J. (2007). All-Fiber Chirped Microwave Pulses Generation Based on Spectral Shaping and Wavelength-to-Time Conversion. IEEE Transactions on Microwave Theory and Techniques, 55(9), 1958-1963. doi:10.1109/tmtt.2007.904084Chao Wang, & Jianping Yao. (2010). Large Time-Bandwidth Product Microwave Arbitrary Waveform Generation Using a Spatially Discrete Chirped Fiber Bragg Grating. Journal of Lightwave Technology, 28(11), 1652-1660. doi:10.1109/jlt.2010.2047093Chao Wang, & Jianping Yao. (2009). Chirped Microwave Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Sagnac Loop Mirror Incorporating a Chirped Fiber Bragg Grating. Journal of Lightwave Technology, 27(16), 3336-3341. doi:10.1109/jlt.2008.2010561Li, M., & Yao, J. (2011). Photonic Generation of Continuously Tunable Chirped Microwave Waveforms Based on a Temporal Interferometer Incorporating an Optically Pumped Linearly Chirped Fiber Bragg Grating. IEEE Transactions on Microwave Theory and Techniques, 59(12), 3531-3537. doi:10.1109/tmtt.2011.2169078Bolea, M., Mora, J., Ortega, B., & Capmany, J. (2012). Nonlinear dispersion-based incoherent photonic processing for microwave pulse generation with full reconfigurability. Optics Express, 20(6), 6728. doi:10.1364/oe.20.006728Dorrer, C. (2009). Statistical analysis of incoherent pulse shaping. Optics Express, 17(5), 3341. doi:10.1364/oe.17.003341Park, Y., & Azaña, J. (2010). Ultrahigh dispersion of broadband microwave signals by incoherent photonic processing. Optics Express, 18(14), 14752. doi:10.1364/oe.18.01475