Yukitoshi Sanada

Accuracy of relative distance measurement with ultra wideband system

Since very short pulse waves are transmitted, UWB systems have excellent accuracy in terms of distance measurement. In order to measure the distance between the terminals, the transmitted pulses have to be synchronized by a delay-lock-loop (DLL) in the receiver. In this paper the performance of the DLL is evaluated. Its performance depends the timing jitter between the local clocks of the terminals.

IQ imbalance compensation scheme in the presence of frequency offset and dynamic DC offset for a direct conversion receiver

A direct conversion architecture reduces the cost and power consumption of a receiver. However, a direct conversion receiver may suffer from direct current (DC) offset, frequency offset, and IQ imbalance. This paper presents an IQ imbalance estimation scheme for orthogonal frequency division multiplexing (OFDM) direct conversion receivers. The proposed IQ imbalance estimation scheme operates in the presence of dynamic DC offset and frequency offset. The proposed scheme calculates IQ imbalance from a simple equation. It employs the knowledge of the preamble symbols of the IEEE 802.11 a/g standards, while it does not require the impulse response of the channel. Numerical results obtained through computer simulation show that the bit error rate (BER) performance for the proposed IQ imbalance estimation scheme has a degradation of about 4 dB with a large DC offset, frequency offset, and IQ imbalance.

Transceiver circuits for pulse-based ultra-wideband

In this paper a single chip CMOS front-end transceiver for ultra-wideband (UWB) radio is presented. This is the first paper to present whole transceiver circuits for pulse based UWB. The transceiver consists of mostly digital circuits except the LNA and mixer which are simulated for 0.18 /spl mu/m CMOS technology. The power consumption of LNA can be reduced by switching the bias current which is the advantage of the discontinuous feature of the pulse based UWB. The receiver design is tested against PVT variations by running Monte-Carlo simulations. As per the results, the power consumption of the transceiver is 0.44 mW at 10 Mpps (pulse per sec) and 2.5 mW at 50 Mpps.

A co-channel interference cancellation technique using orthogonal convolutional codes

This paper proposes a new parallel co-channel interference cancellation technique which utilizes orthogonal convolutional codes. Co-channel interference (CCI) limits the performance of a spread spectrum multiple access communication link. Several CCI cancellation techniques have been proposed to remove this interference. Of particular interest are techniques which do not require the receiver to have knowledge of the cross-correlation between user sequences. These techniques reconstruct the CCI based on the initial decisions regarding the signals from the other users. However, these techniques leave residual interference after cancellation caused by errors in these initial decisions. To improve the initial decisions and reduce the residual interference, our proposed scheme utilizes the error correcting capability of orthogonal convolutional codes. This paper evaluates the performance of this scheme. We show that, given a processing gain of 128 for up to about 40 users, the performance of the proposed CCI canceller approaches the performance of a system without multi-user interference. We also show that the proposed CCI canceller offers an improvement in capacity by a factor of 1.5/spl sim/3 over that of a conventional canceller.

Broadband ferromagnetic resonance of Ni81Fe19 wires using a rectifying effect

The broadband ferromagnetic resonance (FMR) measurement has been carried out by using a rectifying effect in two sets of

A co-channel interference cancellation technique using orthogonal convolutional codes on multipath Rayleigh fading channel

{\text{Ni}}_{81}{\text{Fe}}_{19}

Performance of joint maximum-likelihood decoding for block coded signal streams in overloaded MIMO-OFDM system

wires. One wire is deposited on the middle strip line of the coplanar waveguide (CPW) and another is deposited between two strip lines of the CPW, measuring the FMR induced by in-plane and out-of-plane magnetic fields, respectively. The FMR frequency is defined by detecting the magnetoresistance oscillation due to the magnetization dynamics induced by a radio frequency (rf) field. The magnetic-field dependence of the resonance frequency and the rectification spectrum are analytically interpreted based on our uniform magnetization precession model. These findings reveal that two distinct rectifying signals are anticipated by a rf field and a rf current, which can easily be controlled by engineering the ferromagnetic wire shape and the external field orientation. These fundamental understandings are crucial for future rf device applications in spintronics.

A CMOS impulse radio ultra-wideband transceiver for 1Mb/s data communications and /spl plusmn/2.5cm range findings

This paper proposes and evaluates a new co-channel interference cancellation technique that utilizes orthogonal convolutional codes on a multipath Raleigh fading channel. In a spread spectrum multiple access environment co-channel interference (CCI) limits the performance of the communication link. To remove this interference, several CCI cancellation techniques have been proposed, including a technique that does not require the receiver to have knowledge of the cross-correlation between user sequences. This method leaves residual interference after the cancellation caused by errors in the initial decisions. To reduce the residual interference and improve the initial decisions, the proposed scheme utilizes the error-correcting capability of orthogonal convolutional codes. This paper evaluates the performance of this scheme. Our results show that the proposed CCI canceller offers an improvement in capacity of a factor of 1.5/spl sim/3 as compared with a conventional canceller on a multipath Rayleigh fading channel. The proposed canceller works in the presence of residual interference due to imperfect cancellation. The proposed canceller also has a capacity improvement with the use of soft handoff in a multicell configuration.

Novel initial acquisition scheme for impulse based UWB systems

This paper presents a joint decoding scheme for block coded signals in an overloaded multiple-input multiple-output (MIMO)-OFDM system. In a normal MIMO-OFDM system, symbol detection is carried out over the signals received by multiple antenna elements and is separated from decoding. However, owing to form factor limitation, a mobile terminal may have a limited number of receive antenna elements. Instead of splitting detection and decoding, in this paper, a joint maximum likelihood (ML) decoding in an overloaded MIMO-OFDM system is investigated. Based on ideal interleaving, independence among coded symbols spread over subcarriers is assumed. Thus, the outage capacity improves even though the ergodic capacity remains the same with a single receive antenna. As an example of the proposed system, bit error rate performance of Hamming coded and spatially multiplexed signals with joint ML decoding on a Rayleigh fading channel is investigated. The error rate is evaluated through analysis and computer simulation.

Frequency Offset Estimation Scheme in the Presence of Time-Varying DC Offset for OFDM Direct Conversion Receivers

A CMOS impulse radio ultra-wideband (IR-UWB) transceiver is developed in 0.18/spl mu/m CMOS. It can be used for a 1Mb/s data transceiver, as well as a range finder within an error of /spl plusmn/2.5cm. Chip layout area of a transmitter and a receiver is 0.035mm/sup 2/ and 0.38mm/sup 2/, respectively. Power dissipation for 1Mb/s data communications is 0.7mW for the transmitter and 4.0mW for the receiver. Bit error rate is lower than 10/sup -5/ for ranges of shorter than 95cm, and 10/sup -3/ for 1m distance. For use of the range finder, power dissipation of the transmitter is 0.7/spl mu/W for 1000 measurements per second. Electronic field intensity is lower than 35/spl mu/V/m, in compliance with the regulation for the extremely low power radio station. Digital transmitter and clocked correlator are proposed for reduction in both layout area and power dissipation.