The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Payam Heydari - One of the best experts on this subject based on the ideXlab platform.

  • cmos distributed active power Combiners and splitters for multi antenna uwb beamforming transceivers
    IEEE Journal of Solid-state Circuits, 2007
    Co-Authors: Aminghasem Safarian, Lei Zhou, Payam Heydari
    Abstract:

    This paper presents the design of the first CMOS distributed active power Combiners and splitters with wideband variable delay and gain. These circuits are the key components for use in multi-antenna (MA) ultra-wideband (UWB) point-to-point beamforming communication systems with multiple transmit and receive antennas. Two broadband circuit topologies for each active power combiner and splitter are proposed, one of which being fabricated in a 0.13-mum CMOS process. The proposed fabricated distributed active power combiner and splitter operate across wide range of frequencies that cover the UWB frequency range from 3.1 to 10.6 GHz. The gain of each RF path of the power combiner and splitter is independently controllable from -15 to 6 dB and from -16 to 9.5 dB, respectively. The wideband variable delay of each RF path varies from 32 to 42 ps for the two-stage power combiner, and from 43 to 53 ps for the three-stage power splitter across the UWB frequency range. Supplied from 1.8-V DC voltage, the power combiner and splitter consume 8.5 mA and 11.4 mA, respectively.

  • cmos distributed active power Combiners and splitters for multi antenna uwb beamforming transceivers
    European Solid-State Circuits Conference, 2007
    Co-Authors: Aminghasem Safarian, Lei Zhou, Payam Heydari
    Abstract:

    This paper presents the design of the first CMOS distributed active power Combiners and splitters with wideband variable delay and gain. These circuits are the key components for use in multi-antenna (MA) ultra-wideband (UWB) point-to-point beamforming communication systems with multiple transmit and receive antennas. Two broadband circuit topologies for each active power combiner and splitter are proposed, one of which being fabricated in a 0.13-μm CMOS process. The proposed fabricated distributed active power combiner and splitter operate across wide range of frequencies that cover the UWB frequency range from 3.1 to 10.6 GHz. The gain of each RF path of the power combiner and splitter is independently controllable from -15 to 6 dB and from -16 to 9.5 dB, respectively. The wideband variable delay of each RF path varies from 32 to 42 ps for the two-stage power combiner, and from 43 to 53 ps for the three-stage power splitter across the UWB frequency rang. Supplied from 1.8-V DC voltage, the power combiner and splitter consume 8.5 mA and 11.4 mA, respectively.

  • distributed active power Combiners and splitters for multi antenna uwb transceivers
    European Solid-State Circuits Conference, 2006
    Co-Authors: Aminghasem Safarian, Lei Zhou, Payam Heydari
    Abstract:

    This paper presents the design of CMOS active power Combiners and splitters with wideband variable gain and delay using distributed architectures. The proposed circuits are the key components for use in multi-antenna (MA) ultra-wideband (UWB) communication systems with beamforming. The proposed distributed active power combiner and splitter operate across 1?10.6GHz bandwidth. Power gain of each path of the combiner and splitter is independently controllable from ?15dB to 6dB and from ?16dB to 9.5dB, respectively. The wideband variable delay of each path of the power combiner is 32 to 42 ps, and for each path of the power splitter is 43 to 53 ps across the UWB frequency range. Both power combiner and splitter have been fabricated in a 0.13?m CMOS process. Supplied from a 1.8V power-supply, the 2-stage distributed active power combiner consumes 8.5mA, and the 3-stage distributed active power splitter draws 11.4mA.

R A York - One of the best experts on this subject based on the ideXlab platform.

  • some considerations for optimal efficiency and low noise in large power Combiners
    IEEE Transactions on Microwave Theory and Techniques, 2001
    Co-Authors: R A York
    Abstract:

    This paper examines some relationships between important design parameters in large combiner systems and key performance objectives such as power, efficiency, noise, and graceful degradation. Results are derived for the combining efficiency of general combiner systems, and used to contrast spatial and corporate Combiners and identify optimum combiner topology for a given device technology. The influence of array size on excess phase noise is quantified and shown to decrease with increase numbers of devices. Results are also presented for the degradation in combining efficiency due to statistical variations in amplifier characteristics, appropriate to large Combiners, showing that phase errors are the dominant factor in power degradation.

  • broadband waveguide based spatial Combiners
    International Microwave Symposium, 1997
    Co-Authors: A Alexanian, R A York
    Abstract:

    An array of tapered slotlines is inserted between rectangular waveguides. Results for a 2/spl times/4 active array at X-band are presented, indicating good combining efficiency and thermal properties as well as excellent bandwidth. To increase the device packing density and remove the lower cutoff frequency of the rectangular waveguide a coaxial combiner is also proposed. A radial arrangement of tapered slotlines is placed between two flared coaxial lines. 64 elements are combined with low combining loss over the 5 to 20 GHz band.

Robert W. Heath - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid precoders and Combiners for mmwave MIMO systems with per-antenna power constraints
    2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, 2016
    Co-Authors: Roberto Lopez-valcarce, Nuria Gonzalez-prelcic, Cristina Rusu, Cristian Rusu, Robert W. Heath
    Abstract:

    This paper considers the design of hybrid precoders and Combiners for mmWave MIMO systems with per-antenna power constraints and the additional limitations introduced by the phase-shifting network in the analog processing stage. Previous hybrid designs were obtained using a total power constraint, but in practical implementations per-antenna constraints are more realistic, specially at mmWave, given the large number of power amplifiers used in the transmit array. Assuming perfect channel knowledge, we obtain first an approximation to the alldigital solution for the precoder and the combiner given the per-antenna constraints. Then, we develop a new method for the design of the hybrid precoder and combiner which attempts to match such all- digital approximation. Simulation results show the effectiveness of the proposed approach, which performs close to the all-digital solution.

  • dictionary free hybrid precoders and Combiners for mmwave mimo systems
    International Workshop on Signal Processing Advances in Wireless Communications, 2015
    Co-Authors: Roi Mendezrial, Nuria Gonzalezprelcic, Cristian Rusu, Robert W. Heath
    Abstract:

    The high cost and power consumption of the radio frequency chain and data converters at mmWave frequencies introduce hardware limitations into the design of MIMO precoders and Combiners. MmWave hybrid precoding overcomes this limitation by dividing the spatial signal processing between the radio frequency and baseband domains. Analog networks of phase shifters have been proposed to implement the radio frequency precoders, since they achieve a good compromise between complexity and performance. In this paper, we propose a low complexity hybrid precoding design for the architecture based on phase shifters. The new method is a greedy algorithm based on the orthogonal matching pursuit algorithm, but replacing the costly correlation operations over a dictionary with the element-wise normalization of the first singular vector of the residual. The main advantage is that the design avoids any assumption on the antenna array geometry. Additionally, numerical results show the superiority of the proposed method in terms of achievable spectral efficiency over other previous solutions.

Danny Harnik - One of the best experts on this subject based on the ideXlab platform.

  • ot Combiners via secure computation
    Theory of Cryptography Conference, 2008
    Co-Authors: Danny Harnik, Yuval Ishai, Eyal Kushilevitz, Jesper Buus Nielsen
    Abstract:

    An OT-combiner implements a secure oblivious transfer (OT) protocol using oracle access to n OT-candidates of which at most t may be faulty.We introduce a newgeneral approach for combining OTs by making a simple and modular use of protocols for secure computation. Specifically, we obtain an OT-combiner from any instantiation of the following two ingredients: (1) a t-secure n-party protocol for the OT functionality, in a network consisting of secure point-to-point channels and a broadcast primitive; and (2) a secure two-party protocol for a functionality determined by the former multiparty protocol, in a network consisting of a single OT-channel. Our approach applies both to the "semi-honest" and the "malicious" models of secure computation, yielding the corresponding types of OT-Combiners. Instantiating our general approach with secure computation protocols from the literature, we conceptually simplify, strengthen the security, and improve the efficiency of previous OT-Combiners. In particular, we obtain the first constant-rate OT-Combiners in which the number of secure OTs being produced is a constant fraction of the total number of calls to the OT-candidates, while still tolerating a constant fraction of faulty candidates (t = Ω(n)). Previous OT-Combiners required either ω(n) or poly(k) calls to the n candidates, where k is a security parameter, and produced only a single secure OT. We demonstrate the usefulness of the latter result by presenting several applications that are of independent interest. These include: Constant-rate OTs from a noisy channel. We implement n instances of a standard (2 1)-OT by communicating just O(n) bits over a noisy channel (binary symmetric channel). Our reduction provides unconditional security in the semi-honest model. Previous reductions of this type required the use of Ω(kn) noisy bits. Better amortized generation of OTs. We show that, following an initial "seed" of O(k) OTs, each additional OT can be generated by only computing and communicating a constant number of outputs of a cryptographic hash function. This improves over a protocol of Ishai et al. (Crypto 2003), which obtained similar efficiency in the semi-honest model but required Ω(k) applications of the hash function for generating each OT in the malicious model.

  • on robust Combiners for oblivious transfer and other primitives
    Lecture Notes in Computer Science, 2005
    Co-Authors: Danny Harnik, Moni Naor, Joe Kilian, Omer Reingold, Alon Rosen
    Abstract:

    A (1,2)-robust combiner for a cryptographic primitive P is a construction that takes two candidate schemes for P and combines them into one scheme that securely implement P even if one of the candidates fails. Robust Combiners are a useful tool for ensuring better security in applied cryptography, and also a handy tool for constructing cryptographic protocols. For example, we discuss using robust Combiners for obtaining universal schemes for cryptographic primitives (a universal scheme is an explicit construction that implements P under the sole assumption that P exists). In this paper we study what primitives admit robust Combiners. In addition to known and very simple Combiners for one-way functions and equivalent primitives, we show robust Combiners for protocols in the world of public key cryptography, namely for Key Agreement(KA). The main point we make is that things are not as nice for Oblivious Transfer (OT) and in general for secure computation. We prove that there are no transparent black-box robust Combiners for OT, giving an indication to the difficulty of finding Combiners for OT. On the positive side we show a black box construction of a. (2, 3)-robust combiner for OT, as well as a generic construction of (1, n)-robust OT-Combiners from any (1,2)-robust OT-combiner.

D Kalokitis - One of the best experts on this subject based on the ideXlab platform.

  • a simplified design approach for radial power Combiners
    IEEE Transactions on Microwave Theory and Techniques, 2006
    Co-Authors: Aly E Fathy, Sungwoo Lee, D Kalokitis
    Abstract:

    It is known that a radial power combiner is very effective in combining a large number of power amplifiers, where high efficiency (greater than 90%) over a relatively wide band can be achieved. However, its current use is limited due to its design complexity. In this paper, we develop a step-by-step design procedure, including both the initial approximate design formulas and suitable models for final accurate design optimization purposes. Based on three-dimensional electromagnetic modeling, predicted results were in excellent agreement with those measured. Practical issues related to the radial-combiner efficiency, its graceful degradation, and the effects of higher order package resonances are discussed here in detail