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Fully homomorphic encryption (FHE) is one of the prospective tools for privacypreserving machine learning (PPML), and several PPML models have been proposed based on various FHE schemes and approaches. Although the FHE schemes are known as suitable tools to implement PPML models, previous PPML models on FHE encrypted data are limited to only simple and non-standard types of machine learning models. These non-standard machine learning models are not proven efficient and accurate with more practical and advanced datasets. Previous PPML schemes replace non-arithmetic activation functions with simple arithmetic functions instead of adopting approximation methods and do not use bootstrapping, which enables continuous homomorphic evaluations. Thus, they could not use standard activation functions and could not employ a large number of layers. The maximum classification accuracy of the existing PPML model with the FHE for the CIFAR-10 dataset was only 77% until now. In this work, we firstly implement the standard ResNet-20 model with the RNS-CKKS FHE with bootstrapping and verify the implemented model with the CIFAR-10 dataset and the plaintext model parameters. Instead of replacing the non-arithmetic functions with the simple arithmetic function, we use state-of-the-art approximation methods to evaluate these non-arithmetic functions, such as the ReLU, with sufficient precision [1]. Further, for the first time, we use the bootstrapping technique of the RNS-CKKS scheme in the proposed model, which enables us to evaluate a deep learning model on the encrypted data. We numerically verify that the proposed model with the CIFAR-10 dataset shows 98.67% identical results to the original ResNet-20 model with non-encrypted data. The classification accuracy of the proposed model is 90.67%, which is pretty close to that of the original ResNet-20 CNN model..., Comment: 12 pages, 4 figures

Recently, Ivanov, Kabatiansky, Krouk, and Rumenko (IKKR) proposed three new variants of the McEliece cryptosystem (CBCrypto 2020, affiliated with Eurocrypt 2020). In this letter, it is shown that one of the IKKR cryptosystems is equal to the McEliece cryptosystem. Furthermore, a polynomial-time attack algorithm for the other two IKKR cryptosystems is proposed. The proposed attack algorithm utilizes the linearity of IKKR cryptosystems. Also, an implementation of the IKKR cryptosystems and the proposed attack is given. The proposed attack algorithm finds the plaintext within 0.2 sec that is faster than the elapsed time for legitimate decryption.

The min-entropy is a widely used metric to quantify the randomness of generated random numbers, which measures the difficulty of guessing the most likely output. It is difficult to accurately estimate the min-entropy of a non-independent and identically distributed (non-IID) source. Hence, NIST Special Publication (SP) 800-90B adopts ten different min-entropy estimators and then conservatively selects the minimum value among ten min-entropy estimates. Among these estimators, the longest repeated substring (LRS) estimator estimates the collision entropy instead of the min-entropy by counting the number of repeated substrings. Since the collision entropy is an upper bound on the min-entropy, the LRS estimator inherently provides \emph{overestimated} outputs. In this paper, we propose two techniques to estimate the min-entropy of a non-IID source accurately. The first technique resolves the overestimation problem by translating the collision entropy into the min-entropy. Next, we generalize the LRS estimator by adopting the general R{\'{e}}nyi entropy instead of the collision entropy (i.e., R{\'{e}}nyi entropy of order two). We show that adopting a higher order can reduce the variance of min-entropy estimates. By integrating these techniques, we propose a generalized LRS estimator that effectively resolves the overestimation problem and provides stable min-entropy estimates. Theoretical analysis and empirical results support that the proposed generalized LRS estimator improves the estimation accuracy significantly, which makes it an appealing alternative to the LRS estimator.

With the ongoing developments in artificial intelligence (AI), big data, and cloud services, fully homomorphic encryption (FHE) is being considered as a solution for preserving the privacy and security in machine learning systems. Currently, the existing FHE schemes are constructed using lattice-based cryptography. In state-of-the-art algorithms, a huge amount of computational resources are required for homomorphic multiplications and the corresponding bootstrapping that is necessary to refresh the ciphertext for a larger number of operations. Therefore, it is necessary to discover a new innovative approach for FHE that can reduce the computational complexity for practical applications. In this paper, we propose a code-based homomorphic operation scheme. Linear codes are closed under the addition, however, achieving multiplicative homomorphic operations with linear codes has been impossible until now. We strive to solve this problem by proposing a fully homomorphic code scheme that can support both addition and multiplication simultaneously using the Reed-Muller (RM) codes. This can be considered as a preceding step for constructing code-based FHE schemes. As the order of RM codes increases after multiplication, a bootstrapping technique is required to reduce the order of intermediate RM codes to accomplish a large number of operations. We propose a bootstrapping technique to preserve the order of RM codes after the addition or multiplication by proposing three consecutive transformations that create a one-to-one relationship between computations on messages and that on the corresponding codewords in RM codes.

Since Cheon et al. introduced an approximate homomorphic encryption scheme for complex numbers called Cheon-Kim-Kim-Song (CKKS) scheme, it has been widely used and applied in real-life situations, such as privacy-preserving machine learning. The polynomial approximation of a modulus reduction is the most difficult part of the bootstrapping for the CKKS scheme. In this article, we cast the problem of finding an approximate polynomial for a modulus reduction into an L2-norm minimization problem. As a result, we find an approximate polynomial for the modulus reduction without using the sine function, which is the upper bound for the approximation of the modulus reduction. With the proposed method, we can reduce the degree of the polynomial required for an approximate modulus reduction, while also reducing the error compared with the most recent result reported by Han et al. (CT-RSA' 20). Consequently, we can achieve a low-error approximation, such that the maximum error is less than 2-40 for the size of the message m/q ≈ 2-10. By using the proposed method, the constraint of q = O(m3/2) is relaxed as O(m), and thus the level loss in bootstrapping can be reduced. The solution to the cast problem is determined in an efficient manner without iteration.

We present a novel code-based signature scheme called modified pqsigRM. This scheme is based on a modified Reed–Muller (RM) code, which reduces the signing complexity and key size compared with existing code-based signature schemes. In fact, it strengthens pqsigRM submitted to NIST for post-quantum cryptography standardization. The proposed scheme has the advantage of the pqsigRM decoder and uses public codes that are more difficult to distinguish from random codes. We use $(U,U+V)$ -codes with the high-dimensional hull to overcome the disadvantages of code-based schemes. The proposed decoder samples from coset elements with small Hamming weight for any given syndrome and efficiently finds such an element. Using a modified RM code, the proposed signature scheme resists various known attacks on RM-code-based cryptography. For 128 bits of classical security, the signature size is 4096 bits, and the public key size is less than 1 MB.

Blockchain systems store transaction data in the form of a distributed ledger where each peer is to maintain an identical copy. Blockchain systems resemble repetition codes, incurring high storage cost. Recently, distributed storage blockchain (DSB) systems have been proposed to improve storage efficiency by incorporating secret sharing, private key encryption, and information dispersal algorithms. However, the DSB results in significant communication cost when peer failures occur due to denial of service attacks. In this letter, we propose a new DSB approach based on a local secret sharing (LSS) scheme with a hierarchical secret structure of one global secret and several local secrets. The proposed DSB approach with LSS improves the storage and recovery communication costs.

This paper makes two major contributions. First, we propose an algorithm to compute a multiplicative inverse modulo $2^{k}$ without using integer division by refining the Arazi–Qi algorithm. We then generalize this algorithm into a scalable algorithm to compute an inverse modulo $2^{kl}$ by iteratively exploiting a $k$ -bit-based process when the inverse modulo $2^{k}$ is given. Because of its scalability, this generalized algorithm can be cost-effectively implemented on hardware and applied to larger modulus operations by iteratively applying a processing unit. Furthermore, we highlight the possibility of the derivation of a binary representation of an inverse $P^{-1}$ in terms of a representation of $P$ and demonstrate this operation for up to eight bits. Second, using this direct relationship, we propose a multi-bit Montgomery inverse algorithm that is at least three times faster than the original version. Finally, we derive various properties of this algorithm and compare it with previous algorithms. This fast calculation of a Montgomery inverse is important for public key cryptographic applications, such as elliptic curve cryptosystems, because the relative speed of calculating a modular inverse for modular multiplication is a critical parameter for deciding which coordinate systems to adopt.

Esmaeili and Gulliver recently proposed a secret key cryptosystem based on error-correcting codes in which a codeword modified by random insertions, deletions, and errors is used as a ciphertext. The secret keys used in this cryptosystem consist of random numbers generated by synchronized random number generators that are implemented using two distinct linear feedback shift registers (LFSRs) in each encryptor and decryptor, respectively. In this letter, we propose a ciphertext-only attack to break the Esmaeili-Gulliver cryptosystem based on LFSRs. The proposed attack requires $O(n)$ consecutive ciphertexts, where $n$ is the number of shift registers in the LFSR, which is the secret key size. The proposed attack consists of two steps, and the time complexity of the first step is linear in the secret key size while the second step is a polynomial-time algorithm.

In this paper, we provide a new third-order bandstop filter (BSF) topology with attenuation control capability. The proposed BSF topology contains inter-resonator coupling structures and it can duplicate the frequency responses of the conventional BSF topology, which does not have inter-resonator couplings. In addition, the proposed topology can control the attenuation level by adjusting the resonant frequency of each resonator, and this characteristic cannot be obtained from the conventional one. Two BSFs utilizing the conventional and proposed topologies are designed, fabricated, and measured to support the presented theory. Two filters have been designed and fabricated employing frequency tunable substrate integrated cavity resonators. The measurement verifies that the BSF utilizing the presented topology is capable of adjusting the attenuation level as well as reproducing the conventional bandstop responses.

In this letter, a new secure information transmission scheme based on polar codes with a pre-shared secret key is proposed. In polar codes, after the channel polarization is induced, good split channels are used to transmit the user message and bad channels are utilized to support the reconstruction of the message by sharing fixed information. If the fixed information in bad channels is secret, an adversary gets difficulty in reconstructing the user message in good channels without knowledge of the fixed information. From this observation, we construct a secure information transmission scheme. By appending pre-/post-processing that imposes a dependency between the transmitted message sub-blocks, the adversary's difficulty can be changed to an intractability, since only partial information can be decodable by attackers. A new class of secret key scheme is developed in such a way.

This letter proposes a new design method for a bandstop filter with two stopbands. Contrary to a conventional method, the presented method allows for achieving two stopbands without increasing the number of the couplings between resonators and the transmission line connecting the input and output ports. In addition, a filter designed using the presented method can not only have different center frequencies but also have different bandwidths by adjusting the resonant frequencies of the resonators. For verification of the proposed approach a dual-stopband filter using four tunable substrate-integrated waveguide resonators has been designed and measured.

As mobile Internet applications supporting real-time communications services are pervasively used, traffic patterns in mobile networks have changed significantly. New mobile Internet applications differ from traditional applications such as web browser and FTP in that they need always-on connectivity and generate a large amount of signaling traffic. The traffic patterns of these new mobile applications lead to frequent change of radio resource control states between connected and idle in the user equipment, consuming device battery power and causing excessive signaling overhead. The growth in signaling has resulted in a traffic surge that has attracted the attention of mobile network operators. In this article, we first explore traffic composition in a 3G network and show that chatty applications such as instant messenger and social network services contribute to the frequent change of radio states. We then describe the mechanism behind the surge in signaling traffic and describe the disastrous outcome when an application server failure and recovery occurs. Lastly, we discuss some remedies to reduce the application signaling traffic and network load in 3G and LTE networks. These remedies include development of network-aware smart applications that consider the mobile network characteristics and introduction of push notification services. We also present related future work and our research directions.

In this letter, we consider the secure network coding problem with no restriction on the network coding vectors. Adeli and Liu proposed a scheme achieving perfect security in a network with network coding. In order to hide a security weakness of their scheme, they imposed a restriction on the linear network code design. However, this restriction can be violated when the random linear network coding is used due to the completely decentralized nature of it. We refine Adeli and Liu's scheme into new one with no restriction and thus remove the security weakness under the computationally bounded adversary assumption.

In this letter, an isolation improvement method between two closely packed planar inverted-F antennas (PIFAs) is proposed via a miniaturized ground slot with a chip capacitor. The proposed T-shaped ground slot acts as a notch filter, and the capacitor is utilized to reduce the slot length. The equivalent circuit model of the proposed slot with the capacitor is derived. The measured isolation between two PIFAs is down to below -20 dB at the whole WLAN band of 2.4 GHz.

In the development of 3D graphic systems for higher resolution and more realistic modeling and rendering, graphic memories also have been playing a critical role to offer the required high bandwidth. Currently, GDDR5 SDRAM's provide with 7Gbps per pin speed [1], reaching their physical limit originated from single-ended signaling nature: noise in reference voltage and power, and channel crosstalk. Especially, the channel crosstalk takes a dominating portion in 7Gbps timing budget, becoming the main barrier for further speed improvement. Although there has been research on crosstalk canceller in memory interface [2], it imposed stringent restrictions on signal ordering and trace length in PCB and package routing, and had limited performance. Therefore, improving the efficiency of DRAM core draws more attention than pin bandwidth now.

A novel printed crossed dipole with broad axial ratio (AR) bandwidth is proposed. The proposed dipole consists of two dipoles crossed through a 90°phase delay line, which produces one minimum AR point due to the sequentially rotated configuration and four parasitic loops, which generate one additional minimum AR point. By combining these two minimum AR points, the proposed dipole achieves a broadband circularly polarized (CP) performance. The proposed antenna has not only a broad 3 dB AR bandwidth of 28.6% (0.75 GHz, 2.25-3.0 GHz) with respect to the CP center frequency 2.625 GHz, but also a broad impedance bandwidth for a voltage standing wave ratio (VSWR) ≤2 of 38.2% (0.93 GHz, 1.97-2.9 GHz) centered at 2.435 GHz and a peak CP gain of 8.34 dBic. Its arrays of 1 t 2 and 2 t 2 arrangement yield 3 dB AR bandwidths of 50.7% (1.36 GHz, 2-3.36 GHz) with respect to the CP center frequency, 2.68 GHz, and 56.4% (1.53 GHz, 1.95-3.48 GHz) at the CP center frequency, 2.715 GHz, respectively. This paper deals with the designs and experimental results of the proposed crossed dipole with parasitic loop resonators and its arrays.

In this letter, a new resonant ground structure (RGS) based on a cavity-backed DGS is proposed. The proposed RGS is similar to a DGS and is modeled by a parallel RLC resonance circuit. Since the proposed RGS utilizes a substrate-filled metallic cavity (SFMC) underneath the DGS, it leads to no back-radiation and high quality factor. The frequency responses and structural parameters are analyzed and verified via simulation and measurement. The quality factor of the proposed RGS with a spiral-shaped defect is larger than that of the DGS with the same defect by a factor of 7.4.

Electromagnetic fields radiated from an intestine-ingested source in the human body model are calculated using the finite-difference time-domain (FDTD) method. The propagation characteristics of the vertically polarized components of the electric fields at the receiving points vertically placed on the model surface are analyzed in the frequency range of 100 MHz to 700 MHz. As the receiving point moves away from the ingested source, the received electric fields show relatively lower attenuation above 400 MHz and generate an unusual dip pattern at a particular frequency below 400 MHz. The above two interesting features may occur due to the surface wave propagating along the boundary of the human body model. The effects of the surface wave are illustrated clearly in the homogeneous circular cylinder as a simplified model of the human body.

Storage systems based on scanning probe microscopy incorporate an array of thermopiezoelectric cantilevers that require charge amplifiers with a wide frequency response but low power consumption. We use an improved frequency compensation method to enhance the in-band frequency response without requiring any additional power. Measurements show that the prototype chip draws the same 68 A at 1.8 V as an unmodified design but has a closed-loop frequency response that is ten times greater. The chip was fabricated in a 0.18-m standard CMOS process, and the charge amplifier core occupies 0.042 mm2.

This letter describes a square patch antenna with a switchable circular polarization (CP) sense. The proposed antenna has four L-shaped slots on the ground plane, and the CP radiation can be generated by current perturbation due to the slotted ground plane. Because the CP sense of the proposed antenna is altered by the current path that is redirected with switched p-i-n diodes on the slots, the CP direction of the proposed antenna can be simply switched between the right-handed and left-handed CPs. As the slot and bias circuits are not placed on the patch side, the proposed antenna has a simple structure and can radiate a CP wave without altering the main beam direction. The experimental results show that antennas have excellent switchable radiation performance at 2.4 GHz.

In this paper, a new composite right/left-handed transmission line (CRLH-TL) with equilateral slots is proposed for efficiency-improved zeroth-order resonant antennas. A 1-D infinitesimal equivalent transmission line circuit model is derived, and the characteristic impedance and dispersive relation are theoretically computed. Based on the isotropic arranged unit cells of the slot-loaded composite right/left-handed transmission line (SL CRLH-TL), 2-D zeroth-order resonators are designed for planar magnetic monopole antenna applications. The SL CRLH-TL provides the zeroth-order resonance with some degradation of the quality factor. Therefore, a highly efficient radiating resonator can be designed with higher gain at the zeroth-order frequency. The theoretical approach was verified by the experimental results. The radiation efficiency was improved by up to 45.6% for the nine-rectangular zeroth-order resonant antenna and 21.4% for the seven-hexagonal zeroth-order resonant antenna without degrading the radiating performance. Moreover, the antenna gains of these two antennas were enhanced by 7.56 and 6.31 dB, respectively, due to the increase of the radiation efficiency.

A full coarse-grid based finite-difference time-domain (FDTD) model is proposed for an efficient analysis of resistively loaded cylindrical antennas driven by coaxial feed lines. In the case of the electrically thin resistive antenna, the thin-wire approximation is applied to the near fields around the antenna. The resistive antenna is equivalently represented by a series connection of piecewisely lumped resistors along the antenna axis. And the coaxial line is replaced by an equivalent source over the feed aperture of the line. Then the corresponding FDTD update equations make it possible to implement the full coarse-grid model without additional grid refinements for the antenna and the feed line. The transient reflected feed voltage and the input impedance of resistive antennas are calculated numerically and compared with those of a full fine-grid.

For the finite-difference time-domain (FDTD) analysis of antennas excited by coaxial lines, an equivalent model of the antenna feed is presented here. Under the quasi-static approximation, the coaxial aperture is simply represented as the equivalent magnetic-frill current and the equivalent load circuit including the effects of the coaxial line. It leads us to a simple modification of the standard FDTD update equation at the aperture without any additional cell modeling of the line. The validity of the proposed model is confirmed by comparing of the FDTD results and the measured data.

In this correspondence, for a positive integer M and a prime p such that M|pn - 1, three families of M-ary sequences using the M-ary Sidel'nikov sequences with period pn - 1 are constructed. Two small families contain [(pn - 1)/2]+M-2 or pn+M-3 M-ary sequences, and both of their maximum magnitudes of correlation values are upper bounded by 2 radic{pn} + 6. The largest family has its maximum magnitude of correlation values upper bounded by 3 radic{pn}+5 and the family size is (M-1)2 (2n-1-1) + M-1 for p = 2 or (M-1)2(pn - 3)/2 + M(M-1)/2 for an odd prime p.

For an odd prime p, n=4k, and d=((p2k+1)/2)2, there are (p2k+1)/2 distinct decimated sequences s(dt+l), 0lesl

A single-feed circular microstrip antenna with reconfigurable polarization capability is proposed. This antenna has a simple structure, which consists of a radiating circular patch, five switches (PIN diode), three matching stubs, and a 50 microstrip feed line. It can be switched between 4 different states: two states (low-frequency and high-frequency) for linear polarization (LP), one state for left hand circular polarization (LHCP) and one for right hand circular polarization (RHCP) by controlling the bias voltage of two PIN diodes. At the same time, three switchable matching stubs are used for matching every polarization state. Simulation results and experimental results show that the proposed antenna demonstrates a low cross polarization level, good impedance bandwidth, and a very good axial ratio in the circularly polarized states.

In this paper, we present several construction methods for low-correlation zone (LCZ) sequence sets. First, we propose a design scheme for binary LCZ sequence sets with parameters (2n+1-2,M,L,2). In this scheme, we can freely set the LCZ length L and the resulting LCZ sequence sets have the size M, which is almost optimal with respect to Tang, Fan, and Matsufuji bound. Second, given a q-ary LCZ sequence set with parameters (N,M,L,epsi) and even q, we construct another q-ary LCZ sequence set with parameters (2N,2M,L,2epsi) or (2N,2M,L-1,2epsi). Especially, the new set with parameters (2N,2M,L,2) can be optimal in terms of the set size if a q-ary optimal LCZ sequence set with parameters (N,M,L,1) is used

A 40-Gb/s duobinary carrier-suppressed return-to-zero (DCS-RZ) signal format generated from phase-modulated (PM) duobinary signals by using a phase modulator and an external intensity modulator is proposed. The transmission performance of the proposed DCS-RZ format is theoretically investigated. The proposed DCS-RZ format can produce a signal bandwidth similar to that produced by the conventional DCS-RZ format generated from conventional duobinary signals using low-pass filters. However, the receiver sensitivities of the proposed DCS-RZ format can be improved by about 2 dB more than those of the conventional DCS-RZ format due to high extinction ratio and nonlinear tolerance. Due to a short pulse of the proposed DCS-RZ format, the tolerance of the first-order polarization mode dispersion (PMD) for the format can be improved by about 1 dB up to the differential-group-delay (DGD) value of 16 ps

For a prime p and positive integers M and n such that M|p/sup n/-1, Sidel'nikov introduced M-ary sequences (called Sidel'nikov sequences) of period p/sup n/-1, the out-of-phase autocorrelation magnitude of which is upper bounded by 4. In this correspondence, we derived the autocorrelation distributions, i.e., the values and the number of occurrences of each value of the autocorrelation function of Sidel'nikov sequences. The frequency of each autocorrelation value of an M-ary Sidel'nikov sequence is expressed in terms of the cyclotomic numbers of order M. It is also pointed out that the total number of distinct autocorrelation values is dependent not only on M but also on the period of the sequence, but always less than or equal to (M/2)+1.

We designed a superparaboloidal solid immersion mirror (SP-SIM) using a tilted parabolic mirror that applied total internal reflection to an optical flying head for near-field recording. As an SP-SIM does not need an objective lens or folding mirror, the height and weight of the optical flying head can be reduced. Using theoretical ray tracing, we found the optimal parameters for rotational symmetric beam intensity on a high-numerical-aperture (NA) focus. The effective NA of the SP-SIM was 1.32 for both the sagittal and meridional focuses. A 408-nm laser source and high refractive index material, NbFD13, was used for the simulation. The minimum spot sizes at full width 1/e/sup 2/ intensity were 237 and 232 nm in the sagittal and meridional directions, respectively, at normal incidence. The size of the beam spot was kept nearly uniform within a maximum 5% deviation as the field angle changed within /spl plusmn/0.15/spl deg/. The SP-SIM measured 0.83 mm/spl times/0.95 mm/spl times/0.27 mm (W/spl times/L/spl times/H) and weighed ca. 0.6 mg.

Microstrip antennas inherently have a high input impedance at resonant frequency. This may not be convenient for some applications. For active integrated antennas, moreover, the radiated power of microstrip antennas needs to be very low at harmonic frequencies. The main goals of this study are impedance matching and harmonic suppression of microstrip antennas. In order to meet these requirements, two one-dimensional (1-D) photonic bandgap (PBG) structures, namely, the defected ground structure (DGS) and the compact microstrip resonant cell (CMRC), are applied to the feed line of microstrip antennas. The characteristic impedance of the microstrip line is controlled by the additional effective inductance of the PBG structure. Without any matching circuits, microstrip antennas can be easily fed by a simple 50 /spl Omega/ microstrip line with a PBG structure at the operating frequency. Additionally, the second harmonic of the proposed antennas is properly suppressed compared to a conventional antenna. Measured results indicate that the two PBG structures are quite effective for harmonic suppression. Therefore, the proposed antennas are suitable for active integrated antennas.

This letter presents a rigorous extension of the concept for the bandstop filter (BSF) with inter-resonator couplings to a higher order filter. We show that a BSF topology with inter-resonator couplings can exhibit the frequency response that a conventional BSF topology without inter-resonator couplings generates. Equivalence between the coupling matrices of the two topologies are shown. As an example, this letter shows that fourth-order BSFs with and without inter-resonator couplings can exhibit identical frequency responses.

For an odd prime p and integers n, m, and k such that n=(2m+1)k, a new family of p-ary sequences of period p/sup n/-1 with optimal correlation property is constructed using the p-ary Helleseth-Gong sequences with ideal autocorrelation, where the size of the sequence family is p/sup n/. That is, the maximum nontrivial correlation value R/sub max/ of all pairs of distinct sequences in the family does not exceed p/sup n/2/+1, which means the family has optimal correlation in terms of Welch's lower bound. The symbol distribution of the sequences in the family is enumerated. It is also shown that the linear span of the sequences in the family is (m+2)n except for the m-sequence in the family.

A novel dual-mode dual-band bandpass filter (BPF) for a single substrate configuration is proposed that uses a balun structure. The outer and inner loop resonators are simultaneously excited by the microstrip line and slotline balun structure. In spite of the microstrip feed network, the proposed dual-mode BPF can achieve dual-band operation. Two proper degenerate modes in the lower and upper passbands can be generated and controlled by installing an inductive cut and a capacitive patch in the corner of two loops, respectively. This letter deals with the analysis and design of the proposed dual-band BPF as well as the experimental validation of the predicted dual-band performance.

A novel ultra-wideband (UWB) bandpass filter (BPF) with improved upper stopband performance using a defected ground structure (DGS) is presented in this letter. The proposed BPF is composed of seven DGSs that are positioned under the input and output microstrip line and coupled double step impedance resonator (CDSIR). By using CDSIR and open loop defected ground structure (OLDGS), we can achieve UWB BPF characteristics, and by using the conventional CDGSs under the input and output microstrip line, we can improve the upper stopband performance. Simulated and measured results are found in good agreement with each other, showing a wide passband from 3.4 to 10.9 GHz, minimum insertion loss of 0.61 dB at 7.02 GHz, a group delay variation of less than 0.4 ns in the operating band, and a wide upper stopband with more than 30 dB attenuation up to 20 GHz. In addition, the proposed UWB BPF has a compact size (0.27?g ~ 0.29?g , ?g : guided wavelength at the central frequency of 6.85 GHz).

The leakage current-voltage characteristics of rf-magnetron sputtered BaTa/sub 2/O/sub 6/ film in a capacitor with the top aluminum and the bottom indium-tin-oxide electrodes have been investigated as a function of applied field and temperature. In order to study the effect of the surface treatment on the electrical characteristics of as-deposited film we performed an oxygen plasma treatment on BaTa/sub 2/O/sub 6/ surface. The dc current-voltage, bipolar pulse charge-voltage, dc current-time, and small ac signal capacitance-frequency characteristics were measured to study the electrical and the dielectric properties of BaTa/sub 2/O/sub 6/ thin film. All of the BaTa/sub 2/O/sub 6/ films in this study exhibited a low leakage current, a high breakdown field strength (3-4.5 MV/cm), and a high dielectric constant (20-30). From the temperature dependence of the leakage current, we could conclude that the dominant conduction mechanism under high electrical fields (>1 MV/cm) is ascribed to the Schottky emission while the ohmic conduction is dominant at low electrical fields (

Roughness effects of neighboring dielectrics on electrical characteristics of thin-film electroluminescent devices were investigated in order to improve the understanding of physics for the devices. Atomic force microscopy analysis reveal that thicker bottom layer of Ta/sub 2/O/sub 5/ shows rougher surface resulting in the rougher surface of ZnS:Pr,Ce layer. It can be easily seen that the dc leakage current increases rapidly with increase of surface roughness. Furthermore, it is notable that the initiation field of Poole-Frenkel current conduction is lowered by increasing surface roughness of Ta/sub 2/O/sub 5/ thin film. Internal charge-phosphor field (Q/sub int/-F/sub p/) analysis and capacitance-ac voltage (C-V) analysis for ITO-Ta/sub 2/O/sub 5/-ZnS:Pr,Ce-Al and ITO-Ta/sub 2/O/sub 5/-ZnS:Pr,Ce-Ta/sub 2/O/sub 5/-Al show that the steady state phosphor field is smaller and C-V curve in transition region is less steep with increase of root-mean-square roughness between lower dielectric and phosphor layer in the alternating current thin-film electroluminescent (ACTFEL) devices. Therefore, we conclude that interface roughness is one of the physical factors to change the electrical performance of ACTFEL device.

Two bandpass filters (BPFs) for ultra-wideband (UWB) applications are proposed using the uniplanar compact- electromagnetic bandgap (UC-EBG) and the foliated UC-EBG (FUC-EBG) structures for size reduction. The sizes of the proposed UWB BPFs are reduced by 20 ~ 22% compared to the conventional one with the microstrip multiple-mode resonator (MMR). Both EBG structures are shown to cause a slow-wave effect, which is required for compactness and the characteristic impedance Zc close to 50 Omega, which is needed for wideband match.

We propose a digital watermarking method for still images in the discrete cosine transform (DCT) domain. The adaptive watermark insertion method is employed to increase the invisibility of the inserted watermark in images, in which variable block-size is adopted depending on the characteristics of the region. Experimental results with several test images show that the proposed watermarking method is robust to several common image processing techniques, including Joint Photographic Experts Group (JPEG) compression, lowpass filtering, multiple watermarking, and cropping.

A novel ultra-wideband bandpass filter (BPF) is presented using a back-to-back microstrip-to-coplanar waveguide (CPW) transition employed as the broadband balun structure in this letter. The proposed BPF is based on the electromagnetic coupling between open-circuited microstrip line and short-circuited CPW. The equivalent circuit of half of the filter is used to calculate the input impedance. The broadband microstip-to-CPW transition is designed at the center frequency of 6.85 GHz. The simulated and measured results are shown in this letter.

In this letter, we describe a novel single polysilicon electrically erasable read-only memory cell with polyfinger capacitor for the control gate (CG). A finger-type capacitor structure with CoSi2 is applied to a floating gate and the CG of the proposed cell. The proposed cell is fabricated by using a 0.18-mum standard logic process. The intergate dielectrics of the proposed cell are formed by a conventional lightly doped drain spacer material that is composed of SiO2 and Si3N4 to avoid any process modification. A Fowler-Nordheim tunneling method is applied for the programming and erasing of the cell. Endurance characteristics of up to 120 000 cycles are demonstrated. The proposed cell shows acceptable data retention characteristics.

Recently, an efficient homomorphic MAC scheme for authentication in network coding is proposed and it is claimed that it achieves a security parameter $1/q^l$ where $l$ is selected according to different security requirements. However, in this paper, we show that there is an attack to make the security parameter $1/q$ instead of $1/q^l$ . And we propose a way to avoid the presented attack.

In this letter, the design flexibility of an elliptic-response open-loop resonator filter is achieved through similarity transformation of the coupling matrix. To verify the proposed method, a compact four-pole elliptic-response bandpass filter is designed using the conventional structure with open-loop resonators. Designed filter has the resonators with very narrow spacing for the required coupling coefficient and it is impossible to implement a filter with wider fractional bandwidth. Two possible configurations to overcome this problem are presented through similarity transformation of the coupling matrix. From this design flexibility, a filter with wider fractional bandwidth is designed with realizable design parameters.

A novel reconfigurable microstrip antenna with switchable polarization sense is proposed. The proposed antenna has a simple structure, consisting of a corner-truncated square radiating patch, four small triangular conductors, and a microstrip line feed. Using independently biased PIN diodes on the patch, it can produce linear polarization, or left- or right-hand circular polarization according to bias voltages. From the measured results, low cross-polarization levels when operated in the linear state and good axial ratios in the circular state are observed.

In this letter, a defected ground structure (DGS) is applied to design a compact microstrip rat-race hybrid coupler. The proposed structure can achieve both a significant reduction of size and harmonic signal. By embedding the DGS section, it is observed that the resonant frequency of the hybrid coupler is significantly lowered, which can lead to a large amount of size reduction for a fixed frequency operation. Besides, the third harmonic signal is suppressed to -30 dB with respect to a conventional rat-race hybrid coupler. In this case, the measured insertion loss is comparable to that of a conventional hybrid coupler.

A microstrip patch antenna using a defected ground structure (DGS) to suppress higher order harmonics is presented. An H-shaped defect on the ground plane with only one or more unit lattices has been utilized and yielded bandstop characteristics. Compared with a conventional microstrip patch antenna without the DGS unit cell, the radiated power of the DGS patch antenna at harmonic frequencies has been drastically decreased.