Yasuyuki Oishi

RF Chipset for Impulse UWB Radar Using 0.13-

A novel ultra-wideband impulse radar architecture for 24-GHz-band short-range radar was developed using 0.13-mum InP high electron-mobility technology. The transmitter part generates an extremely wideband impulse from a pulse generator and then filters it through a bandpass filter. The obtained impulse had a full width at half maximum of 9 ps. Its frequency spectrum spread from dc to over 40 GHz and achieved sufficient flatness in the target band. The power amplifier (PA) for the transmitter had a gain of 15 plusmn0.1 dB, and the low-noise amplifier (LNA) for the receiver had a gain of 40 plusmn1 dB and a minimum noise figure of 1.9 dB. The achieved flatness of integration gain including the PA, LNA, and RF switch was less than plusmn1.2 dB. These RF circuits with gain flatness make a simple matched filter configuration possible without the use of a conventional correlator composed of a local oscillator. An ultra high-speed sample and hold circuit having an ultra-long hold time of more than 3 ns was also developed to detect the output pulses from the matched filter

\mu{\hbox {m}}

An adaptive antenna impedance matching system for mobile communication terminals is proposed. The system adaptively controls two varactors of the pi-network matching circuit detecting the change in the reflection coefficient between the antenna combined with the matching circuit and the RF front end of a transceiver. This system consists mainly of analog circuits and employs only a simple algorithm for convergence, therefore does not need any complicated mathematical formulation for modeling of the system itself as well as its nonlinear control elements. Also the proposed system utilizes only simple digital circuits for timing generation. In this paper, the performance of the adaptive impedance matching system is investigated by simulation. The input impedance of three antennas is alternated assuming the change of the environment due to a human head or a hand and the performance of the impedance matching is compared with fixed capacitance matching systems. As a result, it is found that the input power to the antenna for transmission can be increased by about 2-3 dB per second compared with the fixed capacitance matching system.

InP-HEMT Technology

Multipath clusters in a wireless channel could act as additional channels for spatial multiplexing MIMO systems. However, identifying them in order to come up with better cluster channel models has been a hurdle due to how they are defined. This paper considers the identification of these clusters at the mobile station through a middle ground approach—combining a globally optimized automatic clustering approach and manual clustering of the physical scatterers. By including the scattering verification in the cluster identification, better insight into their behavior in wireless channels would be known, especially the physical realism and eventually a more satisfactorily accurate cluster channel model could be proposed. The results show that overlapping clusters make up the majority of the observed channel, which stems from automatic clustering, whereas only a few clusters have clear delineation of their dispersion. In addition, it is difficult to judge the physical realism of overlapping clusters. This further points to a need for the physical interpretation and verification of clustering results, which is an initial step taken in this paper. From the identification results, scattering mechanisms of the clusters are presented and also their selected first and second order statistics.

An adaptive impedance matching system and its application to mobile antennas

An adaptive impedance matching system is proposed. This system employs only a simple algorithm for convergence, therefore does not need any complicated mathematical formulation for modeling the system itself and its nonlinear control elements. Also, the proposed system utilizes only simple digital circuits, for timing generation, and basic analog circuits. Even with a small range of capacitance for the control element in the matching circuit, there is an improvement in the mismatch by 2-3 dB over an impedance matching circuit with fixed capacitances.

Mobile station spatio-temporal multipath clustering of an estimated wideband MIMO double-directional channel of a small urban 4.5GHZ Macrocell

Abstract A key issue confronting petascale and exascale computing is the growth in probability of soft and hard faults with increasing system size. A promising approach to this problem is the use of algorithms that are inherently fault tolerant. We introduce such an algorithm for the solution of partial differential equations, based on the sparse grid approach. Here, the solution of multiple component grids are efficiently combined to achieve a solution on a full grid. The technique also lends itself to a (modified) MapReduce framework on a cluster of processors, with the map stage corresponding to allocating each component grid for solution over a subset of the processors, and the reduce stage corresponding to their combination. We describe how the sparse grid combination method can be modified to robustly solve partial differential equations in the presence of faults. This is based on a modified combination formula that can accommodate the loss of one or two component grids. We also discuss accuracy issues associated with this formula. We give details of a prototype implementation within a MapReduce framework using the dynamic process features and asynchronous message passing facilities of MPI. Results on a two-dimensional advection problem show that the errors after the loss of one or two sub-grids are within a factor of 3 of the sparse grid solution in the presence of no faults. They also indicate that the sparse grid technique with four times the resolution has approximately the same error as a full grid, while requiring (for a sufficiently high resolution) much lower computation and memory requirements. We finally outline a MapReduce variant capable of responding to faults in ways other than re-scheduling of failed tasks. We discuss the likely software requirements for such a flexible MapReduce framework, the requirements it will impose on users’ legacy codes, and the systems runtime behavior.

An adaptive impedance matching system for mobile communication antennas

SUMMARY This paper experimentally studies and models the angulardelay power spectrum density at the mobile station based on the sitespecific measurement in a macrocell in urban area of Tokyo. The authors first show the azimuth power spectral density at the mobile station. It is decomposed into the “classes” which represent specific contributions within limited azimuth range, as well as the residual. The site-specific propagation mechanism of the classes are next discussed. Finally, the angular-delay PSD models of both classes and residual are proposed and verified. The analysis and modeling in this paper are antenna independent with the full polarimetric information. Consequently, the results are useful to evaluate the performance of arbitrary array antennas with mixed polarization. Due to the rare number of antenna-independent and full-polarimetric measurements, the significant contribution of the angular-delay PSD channel model

Fault-Tolerant Grid-Based Solvers: Combining Concepts from Sparse Grids and MapReduce

A novel ultra wideband impulse radio architecture for 24 GHz-band short-range radar was developed using 0.13 mum InP-HEMT technology. The transmitter part generates an extremely wide band impulse from a pulse generator and then filters it by using a band pass filter (BPF). The obtained impulse shows a bandwidth of over 40 GHz and achieves flatness in the target band. The power amplifier (PA) for the transmitter has a gain of 15 plusmn 0.05 dB, and the low noise amplifier (LNA) for the receiver has a gain of 40 plusmn 1 dB. The achieved flatness of the integration gain including the PA, LNA, and RF-switch is less than plusmn 1.1 dB. These RF circuits with gain flatness make possible a simple matched filter configuration without the use of a conventional correlator composed of a local oscillator

Experimental Analysis and Site-Specific Modeling of Channel Parameters at Mobile Station in an Urban Macrocellular Environment

In this paper, we study a practical design for hybrid space-time block coding (STBC) and spatial multiplexing (SM) with orthogonal frequency division multiplexing (OFDM) systems. The hybrid STBC-SM OFDM systems can achieve both spatial diversity and multiplexing gains simultaneously in frequency selective MIMO channels. For the hybrid designs, zero forcing (ZF) and minimum mean square error (MMSE) linear receivers are derived by a simple transformation. To improve error rate performance, we propose weighted soft decision Viterbi decoding by using the SINR of the transformed equivalent channel matrix. The proposed scheme can mitigate noise enhancement inherent to ZF and MMSE linear detectors. Extensive simulations show that the proposed technique with low complexity exhibit robust performance improvement for different propagation channels and modulations.

An RF Chipset for Impulse Radio UWB Using 0.13 μm InP-HEMT Technology

Results of computer simulation of a direct-conversion FSK (frequency-shift keyed) receiver are reported. The demodulation sensitivity depends strongly on the characteristics of the channel and postdetection filters. The sensitivity is defined as the Eb/No ratio at a bit-error rate of 10/sup -2/. The authors evaluated the dependence of the receiver sensitivity for bandwidth, section order, and filter type as parameters. Sensitivity degradation caused by the local frequency drift was determined. A phase detection technique for this type of receiver, which improves the sensitivity by 2 dB, is proposed.<<ETX>>

Improved Performance for Hybrid STBC and Spatial Multiplexing OFDM Systems with Linear Receivers

We have developed the worlds most compact, energy-efficient transmitter amplifier for IMT-2000 base station systems that uses an adaptive digital predistorter (DPD). The power efficiency is improved by reducing the output back-off (the margin from the saturation point) of power amplifiers and by suppressing the resulting increase in nonlinear distortion with the DPD. This method uses a predistortion technique that estimates the distortion characteristics of amplifiers by using the least mean square (LMS) algorithm, and it adds a complementary signal to the digital baseband signal with a reverse-characteristic of the distortion. The power amplifiers we have developed achieve twice the power efficiency of conventional types. In this paper, we describe the DPD equipment and the experimental results of a DPD transmitter prototype. Currently, IMT-2000 base station systems equipped with the DPD are being shipped worldwide.