The optimal design of an extrapolated impulse response (EIR) filter (in the mini-max sense) is a non-linear programming problem. In this paper, the optimal design of the EIR filter by the semi-infinite programming (SIP) is investigated and an iterative technique for optimally designing the EIR filter is proposed. The simulation experiment validates the effectiveness of the SIP technique and the proposed iterative technique in the optimal design of the EIR filter.

This paper presents a 20 GHz push-push VCO realized by a 10 GHz super-harmonic coupled quadrature oscillator for a quadrature 60 GHz frequency synthesizer. The output nodes are peaked by a tunable second harmonic resonator. The proposed VCO is implemented in 65 nm CMOS process. It achieves a tuning range of 3.5 GHz from 16.1 GHz to 19.6 GHz with a phase noise of -106 dBc/Hz at 1 MHz offset. The power consumption of the core oscillators is 10.3 mW and an FoM of -181.3 dBc/Hz is achieved.

This letter proposes an iterative learning control with advanced output data (ADILC) scheme using an estimation of the impulse response for non-minimum phase (NMP) systems, whose model is unknown, except for the relative degree and the number of NMP zeros. Although the ADILC has a simple learning structure that can be applied to both minimum phase and NMP systems, at least a partial model should be known in order to apply ADILC. Considering this fact, in this letter, we propose a new ADILC method based on the estimation of the impulse response for NMP systems whose model is unknown. An estimation method for the learning matrix and an ADILC scheme are presented for NMP systems.

A method for the specification of weighting functions for a spaceborne/airborne interferometric synthetic aperture radar (SAR) sensor for Earth observation and environment monitoring is introduced. This method is based on designing an optimum mismatched filter which minimizes the total power in sidelobes located out of a specified range region around the peak value point of the system point-target response, i.e. impulse response function under the constraint imposed on the peak value. It is shown that this method allows achieving appreciable improvement in accuracy performance without degradation in the range resolution.

Capacitive feedback VCOs use capacitors that are connected from the output node to the gate of the tail transistor that acts as a current source. Using such feedback results in modulating the current that is used by the oscillator and therefore changes its cyclostationary noise properties which results in a lower output phase noise. This paper presents a mathematical study of capacitive feedback VCOs in terms of stability and phase noise enhancement to confirm stability and to explain the enhancement in phase noise. The derived expression for the phase noise shows an improvement of 4.4 dB is achievable by using capacitive feedback as long as the VCO stays in the current limited region. Measurement results taken from an actual capacitive feedback VCO implemented in a 65 nm CMOS process also agrees with the analysis and simulation results which further validates the given analysis.

In this paper, using the Linear Time Variant (LTV) phase noise model and considering higher order harmonics generated by the oscillator output signal, a more general formula for transformation of the excess phase to the output signal is presented. Despite the basic LTV model which assumes that the total carrier power is within the fundamental harmonic, in the proposed model, the total carrier power is assumed to be distributed among all output harmonics. For the first harmonic, the developed expressions reduce to the basic LTV formulas. Simulation and experimental results are used to ensure the validity of the model.

In this paper, impulse noise removal for digital images is handled. It is well-known that switching-type processing is effective for the impulse noise removal. In the process, noise-corrupted pixels are first detected, and then, filtering is applied to the detected pixels. This switching process prevents distorting original signals. A noise detector is of course important in the process, a filter for pixel value restoration is also important to obtain excellent results. The authors have proposed a local similarity-based filter (LSF). It utilizes local similarity in a digital image and its capability against restoration of orderly regions has shown in the previous paper. In this paper, first, further experiments are carried out and properties of the LSF are revealed. Although LSF is inferior to an existing filter when disorderly regions are processed and evaluated by the peak signal-to-noise ratio, its outputs are subjectively adequate even in the case. If noise positions are correctly detected, capability of the LSF is guaranteed. On the other hand, some errors may occur in actual noise detection. In that case, LSF sometimes fails to restoration. After properties are examined, we propose two effective extensions to the LSF. First one is for computational cost reduction and another is for color image processing. The original LSF is very time consuming, and in this paper, computational cost reduction is realized introducing a search area. Second proposal is the vector LSF (VLSF) for color images. Although color images can be processed using a filter, which is for monochrome images, to each color component, it sometimes causes color drift. Hence vector processing has been investigated so far. However, existing vector filters do not excel in preservation of orderly pattern although color drift is suppressed. Our proposed VLSF is superior both in orderly pattern preservation and color drift suppression. Effectiveness of the proposed extensions to LSF is verified through experiments.

This paper proposes a dual-conduction class-C VCO for ultra-low supply voltages. Two cross-coupled NMOS pairs with different bias points are employed. These NMOS pairs realize an impulse-like current waveform to improve the phase noise in the low supply conditions. The proposed VCO was implemented in a standard 0.18 µm CMOS technology, which oscillates at a carrier frequency of 4.5 GHz with a 0.2-V supply voltage. The measured phase noise is -104 dBc/Hz@1 MHz-offset with a power consumption of 114 µW, and the FoM is -187 dBc/Hz.

The information of channel impulse response (CIR) length and noise variance play an important role in blind identification and equalization of wireless multipath channels. In orthogonal frequency division multiplexing (OFDM) systems, multipath fading channels introduce interference between adjacent symbols which can be prevented by inserting a cyclic prefix (CP) before each symbol. In this letter, we find that the interference power in the cyclic prefix (CP) interval and its variation can be used to estimate the CIR length and noise variance jointly and blindly.

This paper presents the analytical results of the effects of jitter and intersymbol interference (ISI) on a millimeter-wave impulse radio (IR) transceiver, compared with the performance of a developed 10-Gb/s W-band IR-transmitter prototype. The IR transmitter, which is compact and cost-effective, consists of a pulse generator (PG) that creates an extremely short pulse, a band-pass filter (BPF) that shapes the short pulse to the desired millimeter-wave pulse (wavelet), and an optional power amplifier. The jitters of the PG and ISI from the BPF are a hindrance in making the IR transceiver robust and in obtaining excellent performance. One analysis verified that, because of a novel retiming architecture, the random jitter and the data-dependent jitter from the PG give only a small penalty of < 0.5-dB increase in the signal-to-noise ratio (SNR) for achieving a bit error rate (BER) of < 10-12. An alternative analysis on the effect of ISI from the BPF indicated that using a Gaussian BPF enables a transmission with a BER of < 10-12 up to a data rate of 1.4 times as large as the bandwidth of the BPF, which is twice as high as that of a conventional amplitude shift keying (ASK) system. The analysis also showed that the IR system is more sensitive to the ISI than the ASK system and suggested that the mismatching of the skirt characteristics of the developed BPF with those of a Gaussian BPF causes tail lobes following the wavelet, resulting in an on/off ratio of 15 dB and hence, an SNR penalty of 6 dB.

The effective ISFs of differential LC oscillators are derived under the assumption that the drain-to-source current is linearly dependent on the gate-to-source voltage for transistors operated in saturation. Moreover, a new interpretation of phase noise is given by examining the real vector diagram of the carrier signal, upon which the noise voltage induced by the impulse noise current is superimposed. The distinct feature of our vector diagram lies in that the noise voltage is always parallel with the horizontal axis. From the Fourier transformations of the derived effective ISFs, the phase noise of differential LC oscillators can be formulated with physical meanings in the frequency domain. The proposed theory can well describe the translation of the noise spectra when the noises from the LC-tank, the switching transistors, and the tail current source are converted into the phase noise. Theoretical predictions from our formulas agree well with the simulation results.

For an indoor area where a target node is tracked with anchor nodes, we can calculate the priori probability density functions (pdfs) on the distances between the target and anchor nodes by using its shape, three-dimensional sizes and anchor nodes locations. We call it “the area layout information (ALI)” and apply it for two indoor target tracking methods with received signal strength indication (RSSI) assuming a square location estimation area. First, we introduce the ALI to a target tracking method which tracks a target using the weighted sum of its past-to-present locations by a simple infinite impulse response (IIR) low pass filter. Second, we show that the ALI is applicable to a target tracking method with a particle filter where the motion of the target is nonlinearly modelled. The performances of the two tracking methods are evaluated by not only computer simulations but also experiments. The results demonstrate that the use of ALI can successfully improve the location estimation performance of both target tracking methods, without huge increase of computational complexity.

A 0.6-V voltage shifter and a 0.6-V clocked comparator are presented for sampling correlation-based impulse radio UWB receiver. The voltage shifter is used for a novel split swing level scheme-based CMOS transmission gate which can reduce the power consumption by four times. Compared to the conventional voltage shifter, the proposed voltage shifter can reduce the required capacitance area by half and eliminate the non-overlapping complementary clock generator. The proposed 0.6-V clocked comparator can operate at 100-MHz clock with the voltage shifter. To reduce the power consumption of the conventional continuous-time comparator based synchronization control unit, a novel clocked-comparator based control unit is presented, thereby achieving the lowest energy consumption of 3.9 pJ/bit in the correlation-based UWB receiver with the 0.5 ns timing step for data synchronization.

A UWB impulse array antenna (IAA) utilizing a novel electrical scanning system with tapped delay lines is proposed and its usefulness is experimentally verified. The experimental antenna is composed of impulse generators installed in each antenna element and tapped delay lines used for creating transmitting trigger signals, which is a simple circuit configuration. It is shown that the output phase of the transmitting wave can be controlled by controlling the period of the trigger signal, and beam direction can be controlled from -30 deg to +30 deg by changing the trigger frequency from Fc-2 kHz to Fc+2 kHz. Evaluation of this antenna as a short range radar is carried out and distance resolution of 25 cm and angle resolution below 10 deg are obtained.

In this work, a time-of-arrival/time-difference-of-arrival (TOA/TDOA) hybrid relative positioning system based on UWB-IR technology is developed. The system reduces both the complexity of system configuration and the number of wireless transmissions in a positioning sequence. The system performance over various distances between access points is verified by computer simulations and experiments under the assumption that the distance between the access points is less than that between the access point and the target node. For the experiments, the proposed system is implemented with in-house developed UWB transceivers. The experiments confirm that the developed TOA/TDOA hybrid system can detect the relative positions of target nodes (under the condition of two access points 4 m apart) with a measured-angle accuracy of 8.6 degrees.

In this work, an ultra-wideband impulse radio (UWB-IR) transceiver with accurate time-of-arrival (TOA) estimation for a ranging/positioning system was developed for wireless sensor network applications. The system uses an impulse radio characterized by a low duty cycle and direct-sequence spreading, which enable very precise ranging and good receiver sensitivity. An algorithm enabling the TOA of the first-path signal to be measured accurately in a multi-path environment with simple, low-power and low cost implementations was proposed. UWB chips with CMOS 0.18-µm technology and UWB transceiver modules performed that the accuracy of the proposed ranging system is 18.5 cm in a closed space.

In this paper, we present a comparative study on directly aligned multi point controlled wavefront synthesis (DMCWS) and wave field synthesis (WFS) for the realization of a high-accuracy sound reproduction system, and the amplitude, phase and attenuation characteristics of the wavefronts generated by DMCWS and WFS are assessed. First, in the case of DMCWS, we derived an optimal control-line coordinate based on a numerical analysis. Next, the results of computer simulations revealed that the wavefront in DMCWS has wide applicability in both the spatial and frequency domains with small amplitude and phase errors, particularly above the spatial aliasing frequency in WFS, and we clarified that the amplitude error in DMCWS has similar behavior to the well-known approximate expression for spatial decay in WFS; this implies the ease of taking into account estimating the amplitude error in DMCWS. Finally, we developed wavefront measurement system and measured a DMCWS wavefront using our wavefront measurement system and algorithm. The results of measurements clarified the frequency characteristics of a loudspeaker. Also, DMCWS has wide applicability in frequency domains in actual environments. From these findings, we concluded the advantageousness of DMCWS compared with WFS.

This paper presents a systemic analysis for phase noise performances of the series quadrature oscillator (QOSC) by using the time-variant impulse sensitivity function (ISF) model. The effective ISF for each noise source in the oscillator is derived mathematically. According to these effective ISFs, the explicit closed-form expression for phase noise due to the total thermal noise in the series QOSC is derived, and the phase noise contribution from the flicker noise in the regenerative and coupling transistors is also figured out. The phase noise contributions from the thermal noise and the flicker noise are verified by SpectreRF simulations.

This paper presents a systemic analysis for phase noise performances of differential cross-coupled LC oscillators by using Hajimiri and Lee's model. The effective impulse sensitivity functions (ISF) for each noise source in the oscillator is mathematically derived. According to these effective ISFs, the phase noise contribution from each device is figured out, and phase noise contributions from the device noise in the vicinity of the integer multiples of the resonant frequency, weighted by the Fourier coefficients of the effective ISF, are also calculated. The explicit closed-form expression for phase noise of the oscillator is definitely determined. The validity of the phase noise analysis is verified by good simulation agreement.

A new type of digital filter for removing impulsive noise in color images is proposed using interactive evolutionary computing. This filter is realized as a rule-based system containing switching median filters. This filter detects impulsive noise in color images with rules and applies switching median filters only at the noisy pixel. Interactive evolutionary computing (IEC) is adopted to optimize the filter parameters, considering the subjective assessment by human vision. In order to detect impulsive noise precisely, complicated rules with multiple parameters are required. Here, the relationship between color components and the degree of peculiarity of the pixel value are utilized in the rules. Usually, optimization of such a complicated rule-based system is difficult, but IEC enables such optimization easily. Moreover, human taste and subjective sense are highly considered in the filter performance. Computer simulations are shown for noisy images to verify its high performance.