A parallel notch filter (PNF) for eliminating a sinusoidal signal whose frequency and phase are unknown, has been proposed previously. The PNF achieves both fast convergence and high estimation accuracy when the step-size for adaptation is appropriately determined. However, there has been no discussion of how to determine the appropriate step-size. In this paper, we derive the convergence condition on the step-size, and propose an adaptive algorithm with variable step-size so that convergence of the PNF is automatically satisfied. Moreover, we present a new filtering structure of the PNF that increases the convergence speed while keeping the estimation accuracy. We also derive a variable step-size scheme for the new PNF to guarantee the convergence. Simulation results show the effectiveness of the proposed method.

A novel high temperature superconducting interdigital bandpass filter is proposed by using coplanar waveguide quarter-wavelength resonators. The CPW resonators are arranged in parallel, and consequently the filter becomes very compact. The filter is a 5-pole Chebyshev BPF with a midband frequency of 5.0 GHz and an equal-ripple fractional bandwidth of 3.2%. It is fabricated using a YBCO film deposited on an MgO substrate. The measured filtering characteristics agree well with EM simulations and show a low insertion loss in spite of the small size of the filter.

A coplanar type lumped-element 6-pole microwave Chebyshev bandpass filter (BPF) of center frequency (f0) 2.0 GHz and fractional bandwidth (FBW) 1.0 % was designed. For the design method, theory of direct coupled resonator filters using K-inverters was employed. Coplanar type lumped-element BPFs are composed of a meander-line L and interdigital C elements. The frequency response was simulated and analyzed using an electromagnetic field simulator (Sonnet-EM). Further, the changes in f0 and FBW of the BPF were also realized by the mechanical tuning method.

Novel microstrip dual-band bandpass filters with controllable fractional bandwidths and good in-between isolation are presented and implemented. A half-wavelength stepped-impedance resonator is firstly characterized, aiming at producing the two resonant frequencies at 2.4 and 5.2 GHz. Two types of coupled microstrip lines in the parallel and anti-parallel formats are then investigated in terms of unified equivalent J-inverter network. Extensive results are derived to quantitatively show their distinctive frequency-distributed coupling performances under different coupling lengths. The coupling degrees of these two coupled lines at the two resonances are properly adjusted to achieve the dual-passband response with varied or tunable bandwidths. In addition, the parallel coupled line is modeled to bring out a transmission zero between the two resonances so as to achieve the good in-between isolation. The three two-stage bandpass filters are initially designed to exhibit their dual-band response with changeable dual-band bandwidths. A three-stage dual-band filter is in final optimally designed and its predicted performance is confirmed in experiment.

We have examined the improvement of filter properties using sapphire and nickel rod trimmers. We measured the resonance frequency of the hairpin resonator in the filter, and examined the difference between the simulated and measured values. When the measured resonance frequency was lower than the simulated frequency, we used a nickel trimmer to increase the resonance frequency, and when high, a sapphire trimmer to decrease the frequency. Our results showed that the use of sapphire and nickel rod trimmers is effective in improving the frequency response of HTS bandpass filters.

In this letter, we present a new numerical design method for 2-D FIR quincunx filter banks (QFB) with low-delay, equiripple magnitude response, and perfect reconstruction (PR). The necessary conditions for the system delay of QFB are derived. The dual affine scaling variant of Karmarkar's algorithm is employed to minimize the peak ripples of analysis filters, and a linearization scheme is introduced to satisfy the PR constraint for QFB. We have included several simulation examples to show the efficacy of this proposed design technique.

The deblocking filter in H.264 is an efficient tool to reduce blocking artifact, but it also blurs the details or retains blocking artifact perceptible in some high-activity areas. In this paper, we improve the filtered pixel classification and filtering schemes used by the deblocking filter in H.264 to keep the sharpeness of real edges and minimize over-smoothing.

The least squares (LS) and the weighted least squares (WLS) algorithms are well known procedures that are used in the design of quadrature mirror filters (QMFs). It is known that these design techniques suffer from pass-band anomaly under certain conditions. A recent method, that overcomes pass-band anomaly for LS QMFs using a frequency sampling design for the initial filter, is extended to WLS design in this letter. A comparison between the modified LS and WLS designs based on experimental results is presented. Although WLS designs have been reported to have superior near-equiripple stop-band performance as compared to LS designs, we find that this is not always true. Specifically, LS designs, with inherent computational and robustness advantages, also have better peak stop-band ripple and transition bandwidth at higher cut-off frequencies than WLS.

An efficient adaptation technique of the delay is introduced for accomplishing more accurate adaptive linear equalization of nonminimum phase channels. It is focused that the filter structure and adaptation procedure of the adaptive Butler-Cantoni (ABC) equalizer is very suitable to deal with a variable delay for each iteration, compared with a classical adaptive linear transversal equalizer (LTE). We derive a cost function by comparing the system mismatch of an optimum equalizer coefficient vector with an equalizer coefficient vector with several delay settings. The cost function is square of difference of absolute values of the first element and the last element for the equalizer coefficient vector. The delay adaptation method based on the cost function is developed, which is involved with the ABC equalizer. The delay is adapted by checking the first and last elements of the equalizer coefficient vector and this results in an LTE providing a lower mean square error level than the other LTEs with the same order. We confirm the performance of the ABC equalizer with the delay adaptation method through computer simulations.

A high quality-factor of active inductor has been implemented by using the 0.18 µm 1P6M CMOS technologies in this work. By adding a feedback resistance and a regulated gain stage transistor into the conventional cascade-grounded approach, the quality-factor and performance of CMOS active inductor can be improved. This novel active inductor demonstrated a maximum quality-factor of 540 and a 3.2 nH inductance at 4.3 GHz, where the self-resonant frequency was 5.4 GHz. An active CMOS bandpass filter was also fabricated including this tunable high quality factor active inductor, performing an insertion loss of 0.2 dB and a return loss more than 32 dB with a tuning range from 3.45 GHz to 3.6 GHz. The input IP3 was -2.4 dBm, and the noise figure was 14.1 dB with a 28 mW dc power consumption.

Although the multiuser detection scheme based on Kalman filtering (K-MUD) proposed by Zhang and Wei, is referred to as a "blind" algorithm, in fact it is not really blind because it is conditioned on perfect knowledge of system parameter, power of the desired user. This paper derives an algorithm to estimate the power of the user of interest, and proposes a completely blind multiuser detection. Computer simulations show that the proposed parameter estimation scheme obtains excellent effect, and that the new detection scheme has nearly the same performance as the K-MUD, there is only slight degradation at very low input signal-to-interference ratios (SIR).

In this paper, we propose a method for detecting and tracking faces in video sequences in real time. It can be applied to a wide range of face scales. Our basic strategy for detection is fast extraction of face candidates with a Six-Segmented Rectangular (SSR) filter and face verification by a support vector machine. A motion cue is used in a simple way to avoid picking up false candidates in the background. In face tracking, the patterns of between-the-eyes are tracked while updating the matching template. To cope with various scales of faces, we use a series of approximately 1/ scale-down images, and an appropriate scale is selected according to the distance between the eyes. We tested our algorithm on 7146 video frames of a news broadcast featuring sign language at 320240 frame size, in which one or two persons appeared. Although gesturing hands often hid faces and interrupted tracking, 89% of faces were correctly tracked. We implemented the system on a PC with a Xeon 2.2-GHz CPU, running at 15 frames/second without any special hardware.

In conventional OFDM systems, the effect of inter-block-interference (IBI) can be completely removed by inserting sufficient redundant symbols between successive transmission blocks. In this paper, based on the reformulated received block symbols of the discrete multirate filterbanks model, a new transceiver model for the cyclic prefix (CP) OFDM systems is proposed, associated with the oblique projector technique (view as the pre-processor for achieving IBI-free). Consequently, a novel ISI-free receiver with the zero-order FIR zero-forcing (ZF) filterbanks equalizer can be devised, under noise-free environment. For performance comparison the bit-error-rate (BER) is investigated for the cases of noisy and noise-free channels. In all cases, viz., the length of CP is shorter or longer than the order of the channel impulse response, we show that the same BER performance compared with the one suggested in [3] can be achieved, under the same assumptions and conditions. Since a simple cascade configuration of the IBI cancellation using the oblique projector followed by the ISI cancellation using the zero-order FIR ZF filterbanks equalizer can be realized for OFDM systems with sufficient or insufficient CP, the complexity of transceiver design can be reduced.

In the letter we extend our previous work, which applies genetic programming to passive filter synthesis tasks. The extended method deals with the tolerance design considerations. Experimental results show that our method can effectively generate filters which outperform those generated by traditional methods. In addition, it provides filter designers with an effective CAD tool to manage the trade-off between manufacturing yield and circuit cost.

The partial projection filter (PTPF) for a given observation operator provides an optimal signal restoration in the presence of both the signal space and observation space noises. However, restoration error by the filter still depends on the observation operator which consists of measurement and sampling processes. In this paper, we determine a sampling operator which minimizes the restoration error by the PTPF. We see that under some assumptions about noise statistics, the restoration error by the PTPF is divided into two terms corresponding to the error arising from the signal space noise and that from the observation space noise. It has been found that although the restoration error due to the signal space noise is independent of the sampling operator, the restoration error arising from the observation space noise can arbitrarily be decreased by increasing the number of sample points in the proposed sampling operator. An illustrative example of optimal sampling in the trigonometric polynomial space is also given.

This paper presents a frequency-controllable image rejection mixer in heterodyne architecture for 2 GHz applications based on TSMC 0.18 µm CMOS technology. The designed mixer uses a notch filter to suppress the image signal and allows precise tuning the image frequencies. An image rejection of 20-70 dB is obtained in a 200 MHz of bandwidth. The simulation results show single-side band (SSB) NF is improved 3.7 dB, the voltage conversion gain of 14.7 dB, improved by more than 4 dB. The circuit operates at the supply voltage of 1.8 V, and dissipates 11.34 mW.

This letter develops convergence analysis of normalized sign-sign algorithm (NSSA) for FIR-type adaptive filters, based on an assumption that filter tap weights are Gaussian distributed. We derive a set of difference equations for theoretically calculating transient behavior of filter convergence, when the filter input is a White & Gaussian process. For a colored Gaussian input and a large number of tap weights, approximate difference equations are also proposed. Experiment with simulations and theoretical calculations of filter convergence demonstrates good agreement between simulations and theory, proving the validity of the analysis.

In our previous work, the hyper H∞ filter is developed for tracking of unknown time-varying systems. Additionally, a fast algorithm, called the fast H∞ filter, of the hyper H∞ filter is derived on condition that the observation matrix has a shifting property. This algorithm has a computational complexity of O(N) where N is the dimension of the state vector. However, there still remains a possibility of deriving alternative forms of the hyper H∞ filter. In this work, a fast J-unitary form of the hyper H∞ filter is derived, providing a new H∞ fast algorithm, called the J-fast H∞ filter. The J-fast H∞ filter possesses a computational complexity of O(N), and the resulting algorithm is very amenable to parallel processing. The validity and performance of the derived algorithm are confirmed by computer simulations.

A novel microstrip dual-mode bandpass filter with ultra-broad stopband is proposed using the aperture-backed stepped-impedance ring resonator (SIRR). This SIRR consists of low-impedance strips in the four bended corners and high-impedance strips in the four straight sides. With the cross-shaped aperture placed on the ground underneath the SIRR, the upper stopband is significantly broadened. In particular, the 2nd resonant frequency of this proposed SIRR is confirmed to exceed the four times of its 1st counterpart. The dual-mode filter with the passband of 7.5% at 1.59 GHz is then designed and implemented, demonstrating the measured stopband of 1.70-5.80 GHz and size reduction of 56.0%.

A new impulse noise detection algorithm is presented, which can successfully remove impulse noise from corrupted images while preserving image details. The impulse detection algorithm is combined with median filtering to achieve noise removal. The main advantage of the proposed algorithm is that it can detect the impulse noise with high accuracy while reducing the probability of detecting image details as impulses. Also, it can be applied iteratively to improve the quality of restored images. It is efficient and low in complexity. Furthermore, it requires no previous training. Extensive experimental results show that the proposed approach significantly outperforms many well-known techniques.