As a fundamental building block of multirate systems, the downsampler, also known as the decimator, is a periodically time-varying linear system. An eigensignal of the downsampler is defined to be an input signal which appears at the output unaltered or scaled by a non-zero coefficient. In this paper, the eigensignals are studied and characterized in the time and z domains. The time-domain characterization is carried out using number theoretic principles, while the one-sided z-transform and Lambert-form series are used for the transform-domain characterization. Examples of non-trivial eigensignals are provided. These include the special classes of multiplicative and completely multiplicative eigensignals. Moreover, the locus of poles of eigensignals with rational z transforms are identified.

IP (Intellectual Property) reuse plays an important role in modern IC design so that IP Protection (IPP) technique is get concerned. In this paper, we introduce a new efficient watermarking system for IPP on post-layout design stage. The signature (which indicates the designer) is encrypted with a secret key by DES (Data Encryption Standard) to produce a bit string, which is then embedded into the layout design as constraints by using a specific incremental router. Once the design is watermarked successfully, the signature can be extracted accurately by the system. The system also has a strong resistance to the attack on watermarking due to the DES functionality. This watermarking technique uniquely identifies the circuit origin, yet is difficult to be detected or fabricated without our tool. We evaluated the watermarking system on IBM-PLACE 2.0 benchmark suites. The results show the system robustness and strength: the system success probability achieves 100% in suitable time with no extra area and wire length cost on design performances.

This paper describes a method for evaluating the performance of a small magnetic core loop antenna used for radio controlled watches. Recently, amorphous metal core loop antennas are used as built-in small antennas inside a metal case. It is difficult to perform electromagnetic simulation for amorphous core loop antennas because of the complicated laminate structure. Therefore, we modeled the amorphous metal core loop antenna as an equivalent bulk structure having anisotropic permeability property that we can simulate. We analyzed the receiving sensitivity of the amorphous antenna by calculating the antenna factor. The receiving sensitivity degrades remarkably when an antenna is inside a metal case. We performed further simulation to investigate eddy current losses that cause deterioration.

This paper presents the switched-beam slot antenna over the electromagnetic band-gap (EBG) reflector. This antenna is composed of two slot elements fed with a phase difference and the EBG reflector, which is used in order to realize a low profile structure. The radiation characteristics of this antenna are calculated using the FDTD method. Calculations show that the height of the antenna using the EBG reflector is 60 % lower than that of the antenna using a perfect electric conductor (PEC) reflector. The radiation characteristics at the center of the operating frequency band in the EBG reflector are equivalent to that in the PEC reflector. It is shown that the tilt angle of the main beam in the elevation plane varies with the operating frequency, and the variation in the case of the EBG reflector is caused by its frequency-dependent reflection phase. Moreover, the radiation pattern of the fabricated antenna is measured. The results demonstrate that the low profile design can be achieved by using the EBG reflector, and reveal the influence of the EBG reflector on the antenna efficiency.

This paper presents data on a reconfigurable predistorter for compensating the nonlinearity of a power amplifier in a system supporting both multimode and multiband operations. For compensation, the magnitude and phase response of a predistorter should be easy to tune to match that of a nonlinear amplifier that is used in various standards. That is to say, the predistorter should show decreasing magnitude followed by increasing magnitude, and the phase must initially lag and then lead, or lead and then lag, as a function of the increasing power input. In doing so, the power turning point, gain & phase deviation, and phase lead & lag should easily be controlled by the proposed reconfigurable predistorter using a bias control and impedance transformer. These characteristics are provided by the nonlinearity of the FET and the movement of the bias point caused by negative current generation. This proposed predistorter can be adopted for a system that uses Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) 800 MHz, and CDMA 1800 MHz. For example, by adopting this reconfigurable predistorter in a CDMA 1800 MHz, as much as 14 dB improvements in Adjacent Channel leakage Power Ratio (ACPR) at the 4 dB back off power level, can be achieved for the CDMA 1800 MHz signal.

This paper presents design of an alternating-phase fed single-layer slotted waveguide array for a sector shaped beam in the E-plane radiation pattern. A sector beam pattern is very effective for radar applications for detecting obstacles in a certain angular range without mechanical or electronic scanning. The sector shaped beam with 13 degree beam width is synthesized by a cascade of T-junctions in the feed waveguide which excite the radiating waveguides with a longitudinal shunt slot array. In order to realize the required excitation distribution of the radiating waveguides for the sector shaped beam, 30 T-junctions with symmetrical arrangement are designed by tuning a width of the coupling window, an offset of the window, and a width of the feed waveguide cascaded to the subsequent T-junction, respectively. Design and measurement are performed in 60 GHz band. The prototype antenna assembles easily; the slotted plate is just tacked on the groove feed structure and is fixed by screws at the periphery, which is the key advantage of the alternating-phase fed arrays. The measured sector pattern with low sidelobe level agrees well with the predicted one. Validity of the sector beam design as well as the performance of the alternating-phase fed array is confirmed by the measurement.

We investigated the radio propagation characteristics for line-of-sight (LOS) inter-vehicle communication (IVC) at 60 GHz on an actual road with an undulating surface. Radio propagation tests between two moving vehicles were carried out on a test course. From this, it was found that the measured received power on the actual road and the results calculated for a flat road approximately follow logarithmic normal distributions. To investigate this phenomenon in detail, a propagation test between two stationary vehicles on a road was performed. Furthermore, calculations using geometrical optics taking road undulation into consideration demonstrated that undulation in the road can cause variations in the received power that follow a logarithmic normal distribution. Finally, the received power for moving vehicles on an undulating road was calculated using the model.

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.

In this paper, we propose an accurate and scalable S-parameter de-embedding method for RF/microwave on-wafer characterization of silicon MOSFETs. Based on cascade configurations, this method utilizes planar open, short, and thru standards to estimate the effects of surrounding parasitic networks on a MOS transistor. The bulk-shielded open and short standards are used to simulate and de-embed the probe-pad parasitics. The thru standard are used to extract the interconnect parameters for subtracting the interconnect parasitics in gate and drain terminals of the MOSFET. To further eliminate the parasitics of dangling leg in source terminal of the MOSFET, we also introduce the microwave and multi-port network analysis to accomplish the two-port-to-three-port transformation for S-parameters. The MOSFET and its corresponding de-embedding standards were fabricated in a standard CMOS process and characterized up to 40 GHz. The scalability of the open, short, and thru standards is demonstrated and the performance of the proposed de-embedding procedure is validated by comparison with several de-embedding techniques.

A particle for artificial magnetic materials in microwave frequency is proposed. It has simple structure composed of two parallel metal strips and is suitable to make a thin material extending in the transverse plane. In order to grasp the characteristic the effective permeability is formulated in the form of a transmission line. The characteristics of effective permeability are discussed based on the transmission line model for miniaturization and increase of the permeability. After discussing the reflection from materials with negative permeability or negative permittivity, a high impedance material is constituted. Total reflection with zero phase from the material composed of modified magnetic particles is measured in a waveguide.

The average bit erasure probability of a binary linear code ensemble under maximum a-posteriori probability (MAP) decoding over binary erasure channel (BEC) can be calculated with the average support weight distribution of the ensemble via the EXIT function and the shortened information function. In this paper, we formulate the relationship between the average bit erasure probability under MAP decoding over BEC and the average support weight distribution for a binary linear code ensemble. Then, we formulate the average support weight distribution and the average bit erasure probability under MAP decoding over BEC for regular LDPC code ensembles.

This letter proposes a group-based distributed air index (called GDI) using two-leveled groups by partitioning the identifiers of data items to reduce the size of the index. GDI provides both global and local views of data items and multiple pointers to data items in a single access to an index. Simulation results show that GDI outperforms the existing index in terms of multiple data access, energy conservation and data waiting time.

In digital transmission and storage systems, sequences must have attributes that comply with the physical characteristics of the channel. These channel constraints can often be satisfied through constrained sequence coding techniques which avoid use of sequences that violate the given channel constraints. In the design of a constrained code, it is usually helpful to consider the PSD of the encoded sequence in order to ensure that PSD requirements are met, and to obtain an indication of bandwidth, response at dc, average power peaks, and other spectral characteristics of interest. In this paper, we introduce an approach for the construction of finite-state sequential machine (FSSM) modeled encoders to satisfy spectral requirements. This approach involves construction of either a Mealy or a Moore FSSM to represent the encoder, and evaluation of the state transition probabilities and codeword values such that the PSD of the designed code meets a predefined spectral shape. Examples in this paper demonstrate the usefulness of this approach.

The present paper introduces a new construction of a class of binary periodic sequence set having a zero-correlation zone sequence set. The cross-correlation function and the side-lobe of the auto-correlation function of the proposed sequence set is zero for the phase shifts within the zero-correlation zone. The present paper shows that such a construction generates a binary zcz sequence set by using an arbitrary pair of an even-perfect sequence and an odd-perfect sequence. The proposed zcz sequence set reaches the theoretical upper bound of the member size of the sequence set.

A millimeter-wave low-loss, high-isolation and high-power terminated MMIC switch is developed, and the design theory is formulated. Our invented switch is designed based on a non-linear relationship between the parallel resistance of an FET and its gate width. Our measurements of the parallel resistance with different gate width have revealed that the resistance is inverse proportion to a square of the gate width. By using this relationship, we have found the fact that the multiple FET resonators with smaller gate width and high inductance elements realize high-Q performance for the same resonant frequency. Since the power handling capability is determined by the total gate width, our switch circuit could reduce its insertion loss, keeping the high-power performance. We additionally describe the design method of this switch circuit. The relationships between the gate widths of the FETs and the electrical performances are described analytically. The required gate widths of the FETs for handling high power signal are represented, and the design equations to obtain lower insertion loss and higher isolation performances keeping high power capability are presented. To verify this methodology, we fabricated a MMIC switch. The MMIC had insertion loss of 2.86 dB, isolation of 37 dB and power handling capability of more than 33 dBm at 32 GHz.

Transmission characteristics of a left-handed (LH) ferrite microstrip line are significantly affected by the nonuniform DC bias magnetic field in the ferrite substrate (internal magnetic field Hin) caused by the inhomogeneous demagnetizing effect because the strip conductors of these devices must be mounted at the edge of the ferrite substrate. Three dimensional analyses on the LH ferrite microstrip line are performed taking into account the nonuniform internal magnetic field Hin. The analytical results show that the nonuniform internal magnetic field under the strip conductor near the edge of the ferrite substrate is useful for spreading the frequency band of negative permeability and nonreciprocal operation, and for improvement of both the insertion and return losses of the LH ferrite microstrip line. Measured results of more than 20 dB isolation with 2.2 dB insertion loss and 1.33 GHz bandwidth are corresponding well to the analytical results.

Two-Thickness-Method (TTM) based on an open-ended coaxial probe was investigated with an emphasis on uncertainty analysis to perfect this technique. Uncertainty equations in differential forms are established for the simultaneous measurement of complex electromagnetic (EM) parameters in the systematical consideration of various error factors in measurement. Worst-case differential uncertainty equations were defined while the implicit partial derivation techniques were used to find the coefficients in formulation. The relations between the uncertainties and test sample's thicknesses were depicted via 3D figures, while the influence of the coaxial line's dimension on the measurement accuracy is also included based on the same analysis method. The comparisons between the measured errors and theoretical uncertainty prediction are given for several samples, which validate the effectiveness of our analysis.

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.

The trend of microwave circuits has been toward highly integrated systems. Most design tools for designing microwave circuits mounted the linear or the nonlinear devices adopt the fundamental circuit theory using the S matrix on the frequency domain. The harmonic balance method is also used to correspond to the nonlinear circuit. Therefore, the effect of the electromagnetic field, for example, a mutual coupling between sub-circuits through the space is almost disregarded. To calculate these circuits included its surrounding electromagnetic field, the finite difference time domain method combined with the equivalent circuit simulation had been presented as the lumped element FDTD (LE-FDTD) method. In general, even if an analytical target is a linear circuit, the FDTD method requires very long analytical time. In this paper, we propose an efficient LE-FDTD method to reduce the analytical time. We investigate its efficiency to compare with the conventional LE-FDTD method or measurements, consequently, it is confirmed that the proposal method requires only at analytical time of 1/10 compared with the conventional method. We also show that the proposal method is able to analyze characteristics of the active integrated antenna (AIA) which are practicably impossible to analyze by using the conventional method.

MIMO leads to dramatic improvement in channel capacity and/or link reliability of wireless systems. However, a MIMO channel has only one degree of freedom in a keyhole environment. As a result, this environment reduces achievable channel capacity and link quality. This paper proposes a MIMO repeater system, which can realize a multi-stream transmission. Although the averaged channel capacity in the MIMO repeater system is discussed in several published papers, the probability density functions of eigenvalues of correlation matrix are not analyzed. MIMO transmission performance can basically be estimated from eigenvalues of the channel correlation matrix. We derive an approximated formula for the probability density function of all eigenvalues linked to the space diversity. It is shown that the calculated values based on the proposed method agrees very well with the simulated values.