In communications, the frequency range 0.1-30 THz is essentially terra incognita. Recently, research has focused on this terahertz gap, because the high carrier frequencies promise unprecedented channel capacities. Indeed, data rates of 100 Gbit s(-1) were predicted for 2015. Here, we present, for the first time, a single-input and single-output wireless communication system at 237.5 GHz for transmitting data over 20 m at a data rate of 100 Gbit s(-1). This breakthrough results from combining terahertz photonics and electronics, whereby a narrow-band terahertz carrier is photonically generated by mixing comb lines of a mode-locked laser in a uni-travellingcarrier photodiode. The uni-travelling-carrier photodiode output is then radiated over a beam-focusing antenna. The signal is received by a millimetre-wave monolithic integrated circuit comprising novel terahertz mixers and amplifiers. We believe that this approach provides a path to scale wireless communications to Tbit s(-1) rates over distances of >1 km

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Electro-optic modulation at frequencies of 100 GHz and beyond is important for photonic-electronic signal processing at the highest speeds. To date, however, only a small number of devices exist that can operate up to this frequency. In this study, we demonstrate that this frequency range can be addressed by nanophotonic, silicon-based modulators. We exploit the ultrafast Pockels effect by using the silicon-organic hybrid (SOH) platform, which combines highly nonlinear organic molecules with silicon waveguides. Until now, the bandwidth of these devices was limited by the losses of the radiofrequency (RF) signal and the RC (resistor-capacitor) time constant of the silicon structure. The RF losses are overcome by using a device as short as 500 mm, and the RC time constant is decreased by using a highly conductive electron accumulation layer and an improved gate insulator. Using this method, we demonstrate for the first time an integrated silicon modulator with a 3dB bandwidth at an operating frequency beyond 100 GHz. Our results clearly indicate that the RC time constant is not a fundamental speed limitation of SOH devices at these frequencies. Our device has a voltage-length product of only V p L511 V mm, which compares favorably with the best silicon-photonic modulators available today. Using cladding materials with stronger nonlinearities, the voltage-length product is expected to improve by more than an order of magnitude. Keywords: 100GHz; high-speed silicon modulator; nanophotonics; silicon-organic hybrid INTRODUCTION High-bandwidth electro-optic modulators are key components for a variety of applications such as photonic transceivers for long-haul and on-chip communications, 1 radio-over-fiber links, low-noise microwave oscillators 2 and optical frequency comb generation. 3 However, achieving a small footprint, low power consumption, low modulation voltage and high-speed operation 4,5 remains a challenge. Because unstrained silicon does not possess a x (2) -nonlinearity, 6 state-of-the art silicon photonic modulators mainly rely on free-carrier dispersion (a plasma effect) in pin or pn junctions. [7][8][9] Reversed-biased pn junctions are intrinsically faster than forward-biased pin diodes 7 and already enable 50 Gbit s 21 on-off keying with a voltage-length product of V p L528 V mm.10 Unfortunately, such plasma-effect phase modulators produce undesired intensity modulation as well, and they respond nonlinearly to the applied voltage.An alternative approach uses hybrid integration of III-V epitaxy stacks grown on InP substrates, which are subsequently transferred to silicon-on-insulator waveguides to create high-speed electro-absorption modulators.11 Recently, such a device demonstrated a 3-dB bandwidth greater than 67 GHz, representing the fastest modulator realized on a silicon chip to date. Advanced modulation formats such as quadrature amplitude modulation, however, require phase modulators with a linear response and a pure phase modulation, rendering the electro-optic effect (Pockels effect 12 ) partic...

Abstract-In this paper the possibility of designing an OFDM system for simultaneous radar and communications operations is discussed. A novel approach to OFDM radar processing is introduced that overcomes the typical drawbacks of correlation based processing. A suitable OFDM system parameterization for operation at 24 GHz is derived that fulfills the requirements for both applications. The operability of the proposed system concept is verified with MatLab simulations.

Abstract-This paper describes a model for mobile radio channels that includes consideration of directions of arrival and is thus suitable for simulations of the performance of wireless systems that use smart antennas. The model is specified for 13 different types of environments, covering macro-micro-and picocells. In this paper, a hierarchy of modeling concepts is described, as well as implementation aspects that are valid for all environments. The model is based on the specification of directional channel impulse response functions, from which the impulse response functions at all antenna elements can be obtained. A layered approach, which distinguishes between external (fixed), large-scale-, and small-scale-parameters allows an efficient parameterization. Different implementation methods, based on either a tapped-delay line or a geometrical model, are described. The paper also derives the transformation between those two approaches. Finally, the concepts of clusters and visibility regions are used to account for large delay and angular spreads that have been measured. In two companion papers, the environment-specific values of the model parameters are explained and justified.Index Terms-Direction of arrival, mobile radio channel, smart antennas.