In this paper, we propose a leakage-resilient and proactive authenticated key exchange (called LRP-AKE) protocol for credential services which provides not only a higher level of security against leakage of stored secrets but also secrecy of private key with respect to the involving server. And we show that the LRP-AKE protocol is provably secure in the random oracle model with the reduction to the computational Diffie-Hellman problem. In addition, we discuss about some possible applications of the LRP-AKE protocol.

A novel low insertion-loss and wideband microstrip bandpass filter has been designed and tested. The basic configuration of this novel dual-mode filter is a square ring resonator with direct-connected orthogonal feed lines, and dual-perturbation elements are introduced within the resonator at symmetrical location. The effects of the size of the perturbation element are studied. A new filter having wider bandwidth and transmission zeros are presented. The proposed filter responses are in good agreement with the simulations and experiments.

Transmission line metamaterials on coplanar waveguide with series-capacitive and shunt-inductive distributed loading in periodical intervals are characterized using our developed fullwave self-calibrated method of moments. Firstly, the two effective per-unit-length transmission parameters, i.e., complex propagation constant and characteristic impedance, are numerically extracted. The results provide a straightforward insight into the forward- and backward-wave propagation characteristics in several distinctive bands, including the left- and right-handed stopbands and passbands. In particular, it is demonstrated that in the whole left-handed passband, the propagation constant has purely negative phase constant while the characteristic impedance has only positive real quantity. Next, varied left- and right-handed passbands are studied in terms of lower/higher cut-off frequencies based on ideal equivalent circuit model and practical distributed CPW elements, respectively. Of particular importance, the left-handed and right-handed passbands find to be able to be directly connected with a seamless bandgap under the condition that normalized inductance and capacitance of loaded CPW inductive and capacitive elements become exactly the same with each other. Finally, the 9-cell metamaterial circuits on CPW with actual 50 Ω feed lines are designed and implemented for experimental validation on the derived per-unit-length parameters.

Bandpass filters with broad bandwidth (up to 70%), very wide upper stopband (nearest spurious passband occurs up to five times of passband center frequency (f0)), good stopband rejection performance (better than -30-40 dB in the whole stopband region), and matching with the conventional low cost printed circuit board process with low dielectric constant substrates are proposed in this paper. The proposed filters are designed using parallel-coupled vertically installed planar stepped-impedance resonators (VIPSIRs), which adopt the inherent nature of very tight coupling of VIP coupled line and extremely high impedance of VIP line. The extremely tightly coupled line enables the proposed filters having very wide passband and the extremely high impedance of VIP line leads to extremely large low-to-high impedance ratio that pushes the nearest spurious passband up to 5f0. Both VIP coupled line and VIP high impedance line are analyzed and characterized by the design charts. The design procedures based on the design charts are verified by several experimental examples. The measured results agree very well with the simulated ones.

In this paper, an inverse S-shaped slotted ground structure (S-SGS) is proposed and analyzed. The S-SGS generates dual attenuation poles that can be easily controlled by its structure parameters. The equivalent circuit of the S-SGS consists of lumped elements that can be extracted from the measured S parameters. Moreover, several S-SGS cells are applied to form a miniaturized lowpass filter (LPF), which has a smaller area and a wider stopband in comparison to previous works.

New microstrip bandpass filters with extended stopband bandwidths are proposed by using new asymmetric stepped-impedance hairpin resonators (ASIHRs). The size of the proposed resonators has been reduced around 16%, comparing with the conventional stepped-impedance hairpin resonators (SIHRs) structure. The first bandpass filter is a combination of differ resonators with the same fundamental frequency but differ in harmonic frequencies, resulting in improved suppression spurious responses in stopbands. Furthermore, another bandpass filter uses the ASIHRs periodically loaded on a microstrip line to improve stopband characteristics. The proposed filters not only have compact size of resonators, but also provide improved upper stopband characteristics. The proposed filters provide 20 dB rejection levels in the stopband up to 6f0. The measured filters responses agree very well with the simulated expectations.

A periodically loaded ultra wideband (UWB) bandpass filter based on the electromagnetic band-gap (EBG) concept is presented. Compact wideband filters with steep transition bands can be designed easily using this novel methodology. Unit cells in the EBG circuit model are realized by capacitive and inductive parallel loading of a transmission line. These unit cells are cascaded to realize bandpass filters whose bandwidth depends on the reactive loading of unit cells. The number of unit cells determines the steepness of the band edges of the filter. The main advantage lies in the fact that the size of unit cells can be small because electrical length of transmission line segments in unit cells can be chosen arbitrarily, hence the final filter structure becomes small in size. A microstrip filter with 60% bandwidth is designed and the physical size is compared with a conventional wideband bandpass filter designed with quarter wavelength admittance inverters.

This study presents a class of miniature parallel-coupled bandpass filters with good selectivity and stopband rejection. Capacitive terminations are introduced to the conventional anti-parallel coupled-lines, and lumped-element K-inverters are employed, to achieve both size reduction and spurious suppression. Additionally, the capacitive cross-coupling effect can be introduced to obtain three transmission zeros to enhance the selectivity. Suitable equivalent-circuit models, along with design formulae, are also established. Specifically, via design examples, this work demonstrates the feasibility of proposed filter structures in microstrip configuration. Compared to the conventional parallel-coupled filters, the proposed filters exhibit over 60% size reduction, improved selectivity, and wider stopbands up to four times the center frequency.

In this paper, a notch-band implemented UWB bandpass filter was proposed. The filter was realized by integrating a full ultra-wideband bandpass filter using broadside coupling structure with a bandstop filter using in-line open stub. The in-line open stub was installed in the removed area in the broadside coupled microstrip conductors, which demonstrated a narrow notch-band performance. The proposed filters were designed based on the electromagnetic simulation and fabricated using a wet etching system. Parameter study of length dependence of the notch-band was carried out. The first resonant frequency of the in-line stub appears when the length is approximately equal to one quarter of the guided wavelength. Based on this fact, the notch-band can be adjusted to almost any specified band in the UWB passband. A three-section notch-band implemented filter demonstrated good characteristics: its full frequency bandwidth form 2.8 GHz to 10.2 GHz, good insertion loss of 0.6 dB and 1.0 dB at the centers of the first and second bands respectively, and flat and small group delay of less than 0.40 ns over main pass band, and a large attenuation stopband about 55 dB at 5.63 GHz. A lowpass filter was also introduced in order to improve the out-band performance, by which the measured results show an excellent attenuation better than 30 dB from 10.4 GHz to 17.8 GHz.

Owing to simple structure, low cost and high performance, NRD-guide millimeter wave circuits have attracted much attention in recent years. In this paper, a variety of NRD-guide passive components are reviewed with emphasis on design techniques and performance estimation in the 60 GHz frequency band where the license-free advantage is available. The passive components to be discussed here include compact bends, wideband hybrid couplers, practical three-port junctions, versatile E-plane filters, and effective feeding structures for lens antennas. Some of them are employed to construct millimeter wave transceivers. Eye patterns observed at 1.5 Gbps confirm the potential ability of the fabricated NRD-guide transceivers for high bit-rate, wireless applications.

In this paper, class DE inverter with second order constant K band-pass filter is proposed. In the proposed inverter, the band-pass filter is used instead of the resonant filter in class DE inverter presented at the previous papers. By using band-pass filter, two important results can be gotten. One is the sensitivity of the output voltage to the operating frequency is suppressed by using band-pass filter. The other is that zero voltage switching operation appears when the operating frequency is lower than the nominal frequency. Moreover, it keeps the advantage of class DE inverter with resonant filter, that is, high power conversion efficiency under high frequency operation because of class E switching. The laboratory experiments achieve 90.4% power conversion efficiency under 1.98 W output power and 1.0 MHz operation.

A new method is presented in order to improve the transient response of distributed amplifiers. The method is based on fitting the parameters of the distributed amplifier to those of a predesigned lowpass filter. Analytical expressions are derived to show the performance of the new structure. Three distributed amplifiers are designed based on the proposed method and it has been shown that the new method can significantly improve the transient response of the amplifier. It has been shown that the new method can improve the other characteristics of the distributed amplifier too. The effects of parasitic and lossy elements has also been considered and it has been shown that such effects doesn't violate the generality of the proposed theory.

Accurate values for occurrence probabilities of the template used in the overlapping template matching test included in NIST randomness test suite (NIST SP800-22) have been analyzed. The inaccurate values used in the NIST randomness test suite cause significant difference of pass rate. When the inaccurate values are used and significance level is set to 1%, the experimental mean value of pass rate, which is calculated by use of random number sequences taken from DES (Data Encryption Standard), is about 98.8%. In contrast, our new values derived from a set of recurrence formulas for the NIST randomness test suite give an empirical distribution of pass rate that meets the theoretical binomial distribution. Here, the experimental mean value of pass rate is about 99%, which corresponds to the significance level 1%.

In this paper, we propose a PON-based access network based on conventional TDM-PON architecture for the smooth, economical and effective transition to the future optical access network. We also propose a dynamic MAC protocol for wavelength channel and bandwidth allocation in the TDM-PON subscriber networks, which can provide enhanced network scalability and flexibility, and greater adaptability to the increasing number of subscribers in TDM-PON. In the proposed dynamic MAC protocol, several key functions are manifested, such as multiple wavelength channel utilization and dynamic allocation of multiple time-slots to a user depending on SLA between OLT and ONUs to meet QoS requirements. A dedicated control channel is used for delivering the request and status information between OLT and ONUs. We evaluate the performances of the proposed MAC protocol thru a statistical queuing analysis and numerical simulations. In addition, through simulations using various traffic models we verify the superior performance of the proposed approach by comparing it with conventional TDM-PONs.

In this letter, the fabrication of a compact and high performance semi-lumped coplanar waveguide low-pass filter (CPW-LPF) on high resistivity silicon (HRS) substrate at millimeter wave is proposed. The design procedure and the equivalent circuit of the proposed semi-lumped CPW-LPF is discussed. The filter structure of is very simple but its performances is fairly good. This designed filter at cutoff frequency fc of 31 GHz has very good measured characteristics including the low insertion loss, sharp rejection and low group delay, due to the reduced substrate loss of HRS. Experimental results of the fabricated filter show a good agreement with the predicted results.

This paper presents a novel dual-band comb-line filter using a pair of hybrid resonators. The resonator consists of a half-wavelength stripline resonator short-circuited at both ends and a quarter-wavelength resonator of coplanar waveguide that is nested in the half-wavelength resonator. Numerical calculations by an electromagnetic simulator clarify the characteristics of dual-frequency resonance of the hybrid resonator when the structural parameters are changed. The surface current density on the resonator is also investigated at the resonant frequencies. A typical model of the resonator is fabricated and its resonance frequency characteristics are measured.

Reliability-based hybrid ARQ (RB-HARQ) is a kind of incremental-redundancy ARQ recently introduced. In the RB-HARQ, the receiver returns both NAK signal and set of unreliable bit indices if the received sequence is not accepted. Since each unreliable bit index is determined by the bitwise posterior probability, better approximation of that probability becomes crucial as the number of retransmissions increases. Assuming the systematic code for the initial transmission, the proposed RB-HARQ scheme has the following two features: (a) the sender retransmits newly encoded and interleaved parity bits corresponding to the unreliable information bits; (b) the retransmitted parity bits as well as the initial received sequence are put all together to perform the message passing decoding i.e. the suboptimal MAP decoding. Finally, simulation results are shown to evaluate the above two features.

This paper presents an ultra-wideband (UWB) bandpass filter using a combination of broadside-coupled structure and lumped-capacitor-loaded shunt stub resonator. The broadside-coupled microstrip-to-coplanar waveguide structure provides an ultra-wide bandpass filtering operation and keeps a good stopband at lower frequencies from DC at the same time. The lumped-capacitor-loaded shunt stub resonator creates two transmission zeros (attenuation poles which can be located at the outsides of the two bandedges of the UWB bandpass filter to improve the out-band performance by selecting a suitable combination of the length of the shunt stubs and the capacitance of the loaded chip capacitors. The filter was designed based on electromagnetic simulation for broadside-coupled structure, microwave circuit simulation and experiments for determining the transmission zeros. The filter was fabricated on a one-layer dielectric substrate. The measured results demonstrated that the developed UWB bandpass filter has good performance: low insertion loss about 0.46 dB and low group delay about 0.26 ns at the center of the passband and very flat over the whole passband, and less than -10 dB reflection over the passband. The implemented transmission zeros, particularly at the low frequency end, dramatically improved the out-band performance, leading the filter satisfy the FCC's spectrum mask not only for indoor but also for outdoor applications. These poles improved also the skirt performance at both bandedges of the filter. A lowpass filter has been also introduced and integrated with the proposed bandpass filter to have a further improvement of the out-band performance at the high frequency end. The filters integrated with lowpass section exhibit excellent filter performance: almost satisfying the FCC's spectrum mask from DC to 18 GHz. The developed UWB bandpass filter has a compact size of 4 cm1.5 cm, or 4.8 cm1.5 cm with lowpass section implemented.

A rectangular waveguide compatible NRD guide E-plane bandpass filter is proposed for 55 GHz band OFDM applications. The NRD guide E-plane bandpass filter is constructed by inserting a metal foil array in the E-plane of NRD guide. Simulation, fabrication, and handling of the filter are not difficult because each resonator is constructed by a couple of metal foils of a simple shape. A Chebyshev response 5-pole bandpass filter with a very narrow bandwidth of 550 MHz is designed and fabricated at 55 GHz band. Simulated and measured filter performances agree well with the design specifications. Insertion loss of the fabricated filter is found to be around 2.0 dB. Although temperature stability of the fabricated filter are found to be within manageable level, the adoption of cyclo olefin polymer can be one of solution for the temperature stability improvement.

A design method for an ultra-wideband bandpass filter (BPF) with four coupled lines has been developed. For demonstration purposes, 50 Ω-matched self-complementary antennas integrated with the ultra-wideband, differential-mode BPF with four coupled lines, a notch filter, and a low-pass filter (LPF) were prepared and tested. An optimized structure for a single-stage, broadside-coupled and edge-coupled four-lines BPF was shown to exhibit up to 170% fractional bandwidth and an impedance transformation ratio of 1.2 with little bandwidth reduction, both analytically and experimentally. Using the optimized structure, 6-stage BPFs were designed to transform the self-complementary antenna's constant input impedance (60πεe- 1/2(Ω)) to 50 Ω without degrading bandwidth. In addition, two types of filter variations--a LPF-embedded BPF and a notch filter-embedded BPF--were designed and fabricated. The measured insertion loss of both filter systems was less than 2.6 dB over the ultra-wideband (UWB) band from 3.1 GHz to 10.6 GHz. The filter systems were embedded in the wideband self-complementary antennas to reject unnecessary radiation over the next pass band and 5-GHz wireless LAN band.