Reliable detection of the licensed user signal is a pre-requirement for avoiding interference to the licensed user in a CR network. Cooperative spectrum sensing (CSS) is able to offer improved sensing performance compared to individual sensing. In this paper, we propose a robust soft combination rule based on the Kullback-Leibler divergence (KL-divergence) for CSS. The proposed scheme is able to obtain a similar sensing performance compared to that of maximum gain combination (MGC) without requiring signal to noise ratio (SNR) information. In addition, the proposed scheme protects the sensing process against common types of malicious users without a malicious user identification step. The simulation results demonstrate the effectiveness of the proposed scheme.

In this paper, a novel microstrip hairpin-line bandpass filter which employs a modified Minkowski fractal shape is proposed. Although conventional hairpin-line filters are popular for RF front ends, they suffer from undesired spurious responses located at the second harmonic, which causes asymmetry in the upper skirt band. By proper design, the second harmonic of fractal filters can be significantly suppressed through the use of fractal shape. To validate this novel geometry, the proposed filters are fabricated and measured. Simulated results are in good agreement with measured results.

In this paper, the performance of a low duty factor (DF) hybrid direct sequence (DS) multiband (MB)-pulsed ultra wideband (UWB) system is evaluated over realistic propagation channels to highlight its capability of interference mitigation. The interference mitigation techniques incorporated in the DS-MB-UWB system is a novel design that includes the utilization of the frequency-agile multiple sub-band configuration and the coexistence-friendly low DF signaling. The system design consists of a Rake type receiver over multipath and multi-user channel in the presence of a coexisting narrowband interferer. The propagation channels are modeled based on actual measurement data. Firstly, by suppressing the power in the particular sub-band coexisting with the narrowband signal, performance degradation due to narrowband interference can be improved. It is observed that by fully suppressing the sub-band affected by the narrowband signal, a typical 1-digit performance improvement (e.g. BER improves from 10-3 to 10-4) can be achieved. Secondly, by employing lower DF signaling, self interference (SI) and multi-user interference (MUI) can be mitigated. It is found that a typical 3 dB improvement is achieved by reducing the DF from 0.5 to 0.04. Together, the sub-band power suppression and low DF signaling are shown to be effective mitigation techniques against environment with the presence of SI, MUI and narrowband interference.

Adaptive interference suppression strategies based on the transform domain approach are proposed for a satellite on-board filter bank under tone-type interferences. In the proposed methods, the three kinds of algorithms to compute the threshold level are jointly employed with the notch filter or the clipper. Simulation results show that the proposed schemes significantly improve performance under interfering environments, compared to the no suppression case.

In this paper, a geometric source separation system using nonnegative matrix factorization (NMF) is proposed. The adaptive beamformer is the best method for geometric source separation, but it suffers from a “target signal cancellation” problem in multi-path situations. We modified the HALS-NMF algorithm for decomposition into bases, and developed an interference suppression module in order to cancel the interference bases. A performance comparison between the proposed and subband GSC-RLS algorithm using a MATLAB® simulation was executed; the results show that the proposed system is robust in multi-path situations.

Impulsive noise interference is a significant problem for the Integrated Services Digital Broadcasting for Terrestrial (ISDB-T) receivers due to its effect on the orthogonal frequency division multiplexing (OFDM) signal. In this paper, an adaptive scheme to suppress the effect of impulsive noise is proposed. The impact of impulsive noise can be detected by using the guard band in the frequency domain; furthermore the position information of the impulsive noise, including burst duration, instantaneous power and arrived time, can be estimated as well. Then a time-domain window function with adaptive parameters, which are decided in terms of the estimated information of the impulsive noise and the carrier-to-noise ratio (CNR), is employed to suppress the impulsive interference. Simulation results confirm the validity of the proposed scheme, which improved the bit error rate (BER) performance for the ISDB-T receivers in both AWGN channel and Rayleigh fading channel.

In this paper, a rat-race hybrid coupler based on an open complementary split ring resonator (OCSRR) is presented. By embedding the OCSRR in the microstrip transmission line, slow-wave effect is introduced to achieve size reduction. The proposed rat-race coupler size is 37% smaller than the conventional rat-race coupler. Besides, the proposed coupler provides better third harmonic suppression up to 35 dB. The simulated results are compared with the measured data and good agreement is reported.

To reduce the error of channel estimation caused by noise, a novel noise suppression method based on the degree of confidence is proposed in this paper. The false alarm and false dismissal probabilities, corresponding to noise being taken as part of channel impulse response (CIR) and part of the CIR being mis-detected as noise, respectively, are also investigated. A false alarm reduction method is therefore presented to reduce the false alarms in the estimated CIR while the mis-detection ratio still remains low. Simulation results show the effectiveness of the proposed method.

In this paper, we present a sequentially rotated array antenna with a rectangular patch MSA fed by an L-probe. Since it's important to decrease couplings between patch elements in order to suppress the cross-polarization level, rectangular patches with aspect ratio of k are adopted. We investigate the cross-polarization level of the sequential array and discuss the relationship between the cross-polarization level and the mutual coupling. As a result, the bandwdith of the antenna element is obtained 14.6% when its VSWR is less than 1.5, and the directivity and cross-polarization level of a 4-patch sequential array are 10.8 dBic and 1.7 dBic, respectively, where k=0.6 and the patch spacing of d=0.5 wave length. These characteristics are 5.6 dB and 5.8 dB better than the corresponding values of a square patch sequential array antenna.

Numerous noise suppression methods for speech signals have been developed up to now. In this paper, a new method to suppress noise in speech signals is proposed, which requires a single microphone only and doesn't need any priori-information on both noise spectrum and pitch. It works in the presence of noise with high amplitude and unknown direction of arrival. More specifically, an adaptive noise suppression algorithm applicable to real-life speech recognition is proposed without assuming the Gaussian white noise, which performs effectively even though the noise statistics and the fluctuation form of speech signal are unknown. The effectiveness of the proposed method is confirmed by applying it to real speech signals contaminated by noises.

A planar miniaturized branch-line coupler with harmonic suppression property for UHF band applications is presented in this paper. By properly synthesizing the LC-tanks that employ artificial transmission lines, two pairs of quarter-wavelength branch-lines to respectively meet characteristic impedances of 35.4 and 50 ohms can be obtained with the coupler. For the operating band, it can achieve good 3 dB power division with a 90° phase difference in the outputs of the through and coupled arms. The coupler also has a small area of 20.5(L)18(W) mm2, corresponding to 0.11 λg0.1 λg at 922 MHz. Compared with conventional couplers, the proposed design not only offers a wide bandwidth of more than 230 MHz within 1° or 1 dB, but also works with additional harmonic suppression for achieving better performance. Therefore, the proposed branch-line coupler with a compact size is well suitable for power division application.

An area efficiency hybrid decoupling scheme is proposed to suppress the charge pump noise during F-N tunneling program in non-volatile memory (NVM). The proposed scheme is focused on suppressing the average noise power in frequency domain aspect, which is more suitable for the program error reduction in NVMs. The concept of active capacitor is utilized. Feed forward effect of the amplifier is firstly considered in the impedance analysis, and a trade-off relation between in-band and out-band frequency noise decoupling performance is shown. A fast optimization based on average noise power is made to achieve minimum error in the F-N tunneling program. Simulation results show very stable output voltage in different load conditions, the average ripple voltage is 17 mV with up to 20 dB noise-suppression-ratio (NSR), and the F-N tunneling program error is less than 5 mV for a 800 µs program pulse. A test chip is also fabricated in 0.18 µm technology. The area overhead of the proposed scheme is 2%. The measurement results show 24.4 mV average ripple voltage compared to 72.3 mV of the conventional one with the same decoupling capacitance size, while the noise power suppression achieves 15.4 dB.

A balanced push-push frequency doubler has been demonstrated in 0.25-µm SOI (Silicon on Insulator) SiGe BiCMOS technology operating from 22 GHz to 29 GHz with high fundamental frequency suppression and high conversion gain. A series LC resonator circuit is connected in parallel with the differential outputs of the doubler core circuit. The LC resonator is effective to improve the fundamental frequency suppression. In addition, the LC resonator works as a matching circuit between the output of the doubler core and the input of the output buffer amplifier, which increases the conversion gain of the whole circuit. A measured fundamental frequency suppression of greater than 46 dBc is achieved at an input power of -10 dBm in the output frequency band of 22-29 GHz. Moreover, maximum fundamental frequency suppression of 66 dBc is achieved at an input frequency of 13 GHz and an input power of -10 dBm. The frequency doubler works at a supply voltage of 3.3 V.

A broadband balanced frequency doubler has been demonstrated in 0.25-µm SOI SiGe BiCMOS technology to operate from 22 GHz to 30 GHz. The measured fundamental frequency suppression of greater than 30 dBc is achieved by an internal low pass LC filter. In addition, a pair of matching circuits in parallel with the LO inputs results in high suppression with low input drive power. Maximum measured conversion gain of -6 dB is obtained at the input drive power as low as -1 dBm. The results presented indicate that the proposed frequency doubler can operate in broadband and achieve high fundamental frequency suppression with low input drive power.

In this article, a simple structure of the Wilkinson power divider which can suppress the nth harmonics of the Wilkinson power divider is proposed. By replacing the quarter wavelength transmission lines of the conventional Wilkinson power divider with the equivalent P-type transmission lines, a compact power divider which can suppress the nth harmonic is achieved. Design equations of proposed P-type line are achieved by ABCD matrices. To verify the design approach, the proposed power divider is designed, simulated (by ADS, CST Studio, and Sonnet simulators), and fabricated at 1 GHz to suppress the fifth harmonic. The proposed structure is 46% of the conventional Wilkinson power divider, while maintaining the characteristics of the conventional Wilkinson power divider at the fundamental frequency. The insertion losses at the fifth harmonic are larger than 35 dB. Furthermore, the second to seventh harmonic are suppressed by least 10 dB. Here is an excellent agreement between simulated results and measured results.

The biggest challenge in multi-cell MIMO multiplexing systems is how to effectively suppress the other-cell interference (OCI) since the OCI severely decrease the system performance. Cooperation among cells is one of the most promising solutions to OCI problems. However, this solution suffers greatly from delay and overhead issues, which make it impractical. A coordinated MIMO system with a simplified cooperation between the base stations is a compromise between the theory and practice. We aim to devise an effective resource allocation algorithm based on a coordinated MIMO system that largely alleviates the OCI. In this paper, we propose a joint resource allocation algorithm incorporating intra-cell beamforming multiplexing and inter-cell interference suppression, which adaptively allocates the transmitting power and schedules users while achieving close to an optimal system throughput under proportional fairness consideration. We formulate this problem as a nonlinear combinational optimization problem, which is hard to solve. Then, we decouple the variables and transform it into a problem with convex sub-problems that can be solve but still need heavy computational complexity. In order to implement the algorithm in real-time scenarios, we reduce the computational complexity by assuming an equal power allocation utility to do user scheduling before the power allocation. Extensive simulation results show that the joint resource allocation algorithm can achieve a higher throughput and better fairness than the traditional method while maintains the proportional fairness. Moreover, the low-complexity algorithm obtains a better fairness and less computational complexity with only a slight loss in throughput.

A new comprehensive method to suppress the spurious modes in a BPF is proposed taking the multi-strip resonator BPF as an example. It consists of disturbing the resonant frequency, coupling coefficient and external Q of the higher-order modes at the same time. The designed example has shown an extraordinarily good out-of-band response in the computer simulation.

A novel approach is proposed for miniaturizing the unit cell size of electromagnetic bandgap (EBG) structures that suppress power plane noise. In this approach, open stubs are introduced into the shunt circuits of these EBG structures. Since the stub length determines the resonant frequencies of the shunt circuit, the proposed structures can maintain the bandgaps at lower frequencies without increasing the unit cell size. The bandgap frequencies were estimated by dispersion analysis based on the Bloch theorem and full-wave simulations. Sample boards of the proposed EBG structures were fabricated with a unit cell size of 2.1 mm. Highly suppressed noise propagation over the estimated frequency range of 1.9-3.6 GHz including the 2.4-GHz wireless-LAN band was experimentally demonstrated.

The design of microstrip bandpass filters using stepped-impedance resonators (SIRs) is examined. The passband center frequency for the WCDMA-FDD (uplink band) Japanese cellular system is 1950 MHz with a 60-MHz bandwidth. The SIR physical characteristic can be designed using a SIR characteristic chart based on second harmonic suppression. In our filter design, passband design charts were obtained through the design procedure. Tchebycheff and maximally flat bandpass filters of any bandwidth and any number of steps can be designed using these passband design charts. In addition, sharp skirt characteristics in the passband can be realized by having two transmission zeros at both adjacent frequency bands by using open-ended quarter-wavelength stubs at input and output ports. A new even-mode harmonics suppression technique is proposed to enable a wide rejection band having a high suppression level. The unloaded quality factor of the resonator used in the proposed filters is greater than 240.

This paper proposes an optimized phase rotation sequence method for side lobe suppression by complementing and regulating the side lobe suppression sequence set. The sequence set is efficiently enhanced through the quadratically constrained least square model. The theoretical suppression performance of our method is discussed. Furthermore, our scheme is also suitable for cognitive radio, which is analyzed in the simulation part. The simulation results confirm the effectiveness of our schemes.