The optical ZCZ code is a set of pairs of binary and bi-phase sequences with zero correlation zone. An optical M-ary direct sequence spread spectrum (M-ary/DS-SS) system using this code can detect a desired sequence without interference of undesired sequences. However, the bank of matched filters in a receiver circuit may fall into large scale. In this paper, we propose the compact construction of a bank of matched filters for an M-ary/DS-SS system using an optical ZCZ code. This filter bank can decrease the number of 2-input adders from O(N2) to O(N) and delay circuits from O(N2) to O(Nlog 2 N), respectively, and is implemented on a field programmable gate array (FPGA) corresponding to 400,000 logic gates.

A compact open-loop resonator bandpass filter is presented to suppress the spurious passband using compensated compact microstrip resonant cell (C-CMRC) feeding structure. Based on the inherently compact and stopband characteristics of the C-CMRC feeding, the proposed filters shows a better spurious rejection performance than the only open-loop resonator filter. The suppression is -57.4 dB, -49.5 dB, and -43.9 dB at the 2nd, 3rd and 4th harmonic signal separately. All the performance of proposed filters have been verified by the measured results.

This paper proposes a wideband speech coder in which a G.711 bitstream is embedded. This coder has an advantage over conventional coders in that it has a high interoperability with existing terminals so costly transcoding involving decoding and re-encoding can be avoided. We also propose a partial mixing method that effectively reduces the mixing complexity in multiple-point remote conferences. To reduce the complexity, we take advantage of the scalable structure of the bitstream and mix only the lower band of the signal. For the higher band, the main speaker location is selected among remote locations and is redistributed with the mixed lower-band signal. By subjective evaluations, we show that the speech quality can be maintained even when the speech signals are partially mixed.

We previously proposed a new version of TCP, called Inline measurement TCP (ImTCP), in [2],[3]. The ImTCP sender adjusts the transmission intervals of data packets and then utilizes the arrival intervals of ACK packets for available bandwidth estimation. This type of active measurement is preferred because the obtained results are as accurate as those of other conventional types of active measurement, even though no extra probe traffic is injected onto the network. In the present research, we develop a new capacity measurement function and combine it with ImTCP in order to enable simultaneous measurement of both capacity and available bandwidth in ImTCP. The capacity measurement algorithm is a new packet-pair-based measurement technique that utilizes the estimated available bandwidth values for capacity calculation. This new algorithm promises faster measurement than current packet-pair-based measurement algorithms for various situations and works well for high-load networks, in which current algorithms do not work properly. Moreover, the new algorithm provides a confidence interval for the measurement result.

This letter proposes a compact multi-layered bandpass filter exhibiting left-handed and right-handed behaviors in its passband. This filter has a greatly expanded passband from 1.61 GHz to 4.16 GHz (88.4% bandwidth) with a maximum ripple of 1.2 dB and well-suppressed out-of-passbands with transmission zeros at 1.15 GHz and 4.52 GHz. The physical mechanisms are studied with FEM-based full-wave simulations, equivalent circuit analysis and careful experiments.

The development of a small and multiband antenna plays an important role in the rapidly growing mobile communication market. This paper presents the design of a novel small and wideband planar inverted F-antenna which simultaneously covers GSM850/GSM900/DCS1900/IMT2000/WLAN/DMB services. The proposed antenna consists of a main patch with a pair of slits and L-shaped patch, occupying a total volume of 15366 mm3. A very wide impedance bandwidth characteristic was achieved by optimizing both the gap distance between the feed line and L-shaped patch, and also the lengths and widths of a pair of slits on the main patch, which is excited by the modified CPW-fed line. The average gains at the frequencies of 850, 2000 and 2600 MHz were -2.51, -1.42 and -1.68 dBi, respectively. The overall shape of the radiation patterns is suitable for mobile communications.

In the present paper, ImTCP-bg, a new background TCP data transfer mechanism that uses an inline network measurement technique, is proposed. ImTCP-bg sets the upper limit of the congestion window size of the sender TCP based on the results of the inline network measurement, which measures the available bandwidth of the network path between the sender and receiver hosts. ImTCP-bg can provide background data transfer without affecting the foreground traffic, whereas previous methods cannot avoid network congestion. ImTCP-bg also employs an enhanced RTT-based mechanism so that ImTCP-bg can detect and resolve network congestion, even when reliable measurement results cannot be obtained. The performance of ImTCP-bg is investigated through simulations, and the effectiveness of ImTCP-bg in terms of the degree of interference with foreground traffic and the link bandwidth utilization is also investigated.

At present, during the design of sealed electromagnetic relay, the tolerances of design parameters are given with experience. The designer can't provide quantificational reliability index, and the blindness of tolerance distribution also causes unnecessary increase of machining cost. According to the study of electromagnetic force and spring force characteristics of a certain sealed electromagnetic relay with polarized magnetic system, this paper analyzed the influence of main design parameters' tolerances to the tolerance bands of electromagnetic force and spring force characteristics and achieved the strong correlative factors (viz. design parameters) that have obvious effect on tolerance bands of electromagnetic force and spring force characteristics. Then based on the calculation of reliability, the tolerance distribution method of key design parameters was given. This method not only can make the designed product satisfy requirement of reliability, but also reduce the machining cost.

This investigation proposes a modified equivalent circuit of single complementary split-ring resonator (CSRR) in planar transmission media and a dual-mode ring bandpass filter (BPF) that uses periodic CSRRs to suppress the spurious response. The proposed modified equivalent circuit consists of lumped elements that can be easily extracted from the measured S parameters. The proposed dual-mode ring BPF has exhibits a wide stopband characteristic owing to the bandgap resonant characteristic of CSRRs in the harmonic frequency of the dual-mode ring BPF. Good agreement with EM simulation and measurement is demonstrated.

In this letter, we propose a symbol repetition technique combined with parallel channel encoding for multiband orthogonal frequency division multiplexing systems with ultra wideband channels. It can resolve timing asynchronous cochannel interference from another simultaneously operating piconet. Our simulation results demonstrate that the proposed scheme can effectively reduce the effect of the interference.

This paper describes a method for the classification of bank-notes. The algorithm has three stages, and classifies bank-notes with very low error rates and at high speeds. To achieve the very low error rates, the result of classification is checked in the final stage by using different features to those used in the first two. High-speed processing is mainly achieved by the hierarchical structure, which leads to low computational costs. In evaluation on 32,850 samples of US bank-notes, with the same number used for training, the algorithm classified all samples precisely with no error sample. We estimate that the worst error rate is 3.1E-9 for the classification statistically.

We present room temperature current voltage characteristics from SiGe interband tunneling diodes epitaxially grown on highly resistive Si(001) substrates. In this case, a maximum peak to valley current ratio (PVCR) of 5.65 was obtained. The possible integration of a SiGe tunnel diode with a strained Si transistor lead us to investigate the growth of SiGe interband tunneling diodes on Si0.7Ge0.3 virtual substrates. A careful optimization of the layer structure leads to a maximum PVCR of 1.36 at room temperature. The latter value can be further increased to 2.26 at 3.7 K. Our results demonstrate that high quality SiGe interband tunneling diodes can be realized, which is of great interest for future memory and high speed applications.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for a direct sequence ultra-wideband (DS-UWB) communication system is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

A second-order CMOS continuous-time bandpass filter with a tuneable 4-12 MHz center frequency (fc) is presented. The Design has been done by using a new second-order block which is based on Gm-C method. This Gm-C filter achieves a dynamic range of 30 dB for 1% IM3, and Q equal to 58 at 12 MHz, while dissipating only 10.5 mW from 3.3 V power supply in 0.35 µm CMOS process. The on-chip indirect automatic tuning circuit uses a phase-locked loop which sets filter center frequency to an external reference clock.

Ultrahigh-speed continuous-tine delta-sigma modulators (DSMs) have been designed by using a fully-differential comparator consisting of resonant-tunneling diodes (RTDs) and HEMTs. Continuous-time lowpass and bandpass filters using HEMTs have also been incorporated to obtain lowpass- and bandpass-type DSMs, respectively. Circuit simulation assuming 0.1-µm InP-based HEMT and RTD technology has revealed a successful operation of the 2nd-order lowpass DSM at a sampling frequency of 20 GHz. The clock frequency was 10 GHz because of the double sampling function of the present comparator. The 2nd-order bandpass DSM has also been designed with a center frequency of 3 GHz. These results clearly show high potential of the present delta-sigma modulators.

A small microstrip-fed monopole antenna using an L-shaped notch is presented for ultra wideband applications. The proposed antenna, with compact size of 15.521 mm2 including the ground plane, is designed to operate over the frequency band between 3.05 and 10.9 GHz for S11 < -10 dB. Good return loss and radiation pattern characteristics are obtained in the frequency band of interest.

This paper proposes a novel UWB ranging scheme employing 1-bit ADCs and analog window bank for energy collection. For an appropriate 1-bit ADC process DC offset is exploited and removed via performing analog low pass filter. To improve ranging accuracy in presence of ambiguity, dual overlapped window banks designated as primary and auxiliary windows are utilized. Corresponding to the proposed ranging scheme, its performance is verified by conducting simulations in two types of channel conditions. The simulation results show that the proposed ranging scheme performs well even in condensed multipath environment and low SNR situation.

In this paper, we propose a combination-based novel technique of dithered subband coding with spectral subtraction for improving the perceptual quality of coded audio at low bit rates. It is well known that signal-correlated distortion is audible when the audio signal is quantized at bit rates lower than the lower bound of perceptual coding. We show that this problem can be overcome by applying the dithering quantization process in each subband. Consequently, the quantization noise is rendered into a signal-independent white noise; this noise is then estimated and removed by spectral subtraction at the decoder. Experimental results show an effective improvement by the proposed method over the conventional one in terms of better SNR and human listening test results. The proposed method can be combined with other existing or future coding methods such as perceptual coding to improve their performance at low bit rates.

This study investigates a band extension technique for speech data encoded with G.711, the most common codec for digital speech communications system such as VoIP. The proposed technique employs steganography for the transmission of the side information required for the band extension. Due to the steganography, the proposed technique is able to enhance the speech quality without an increase of the amount of data transmission. From the results of a subjective experiment, it is indicated that the proposed technique may potentially be useful for improving the speech quality, compared with the conventional technique.

A baseband transmission scheme for wireless communications has been proposed and examined using a pair of discone antennas for transmission and reception. The wireless baseband transmission scheme radiates a baseband signal stream, such as non-return-to-zero (NRZ), return-to-zero (RZ), or Manchester encoded signals, directly from an antenna. Namely, a carrier in terms of a sinusoidal radio wave or light wave is not used in the transmission. In experiments, baseband pulses generated with a data generator were radiated directly from the discone antenna, and received waveforms were observed with a digital storage oscilloscope. The experiments showed that wireless baseband transmission is realisable when using antennas with a flat amplitude spectrum and a linear phase characteristic, such as discone antennas, over a given band. Manchester encoding is promising for this wireless baseband transmission.