A 20 GHz-band GaAs MMIC receiver module has been developed using 0.15 µm HEMT technology process. It incorporates two front end low noise amplifiers, a double balanced diode mixer, and filters. The RF input frequency ranges 20.1 to 21 GHz and the IF output 1.1 to 2 GHz. Test results show an overall conversion gain of more than 27 dB, and less than a 2.2 dB noise figure. The image-rejection ratio greater than 21 dB has been obtained. The isolation between RF and IF ports is better than 27 dB, and between LO and IF is more than 50 dB.

The relationship between the change in transistor operation regions and the fault behavior of a mixed-signal circuit having a bridging fault was investigated. We also discussed determination of transistors to be observed for estimating the fault behavior. These results will be useful for modeling faulty behaviors and analyzing and diagnosing faults in mixed-signal circuits.

An epoxy-modified urethane rubber mixed with carbon particles is now chosen as the millimeter-wave absorber material in our study. The absorption characteristics of the absorber is measured under temperature changes. The weatherability of our absorber is also clarified based on absorption characteristics, thickness and hardness of the sample. As a result of the temperature characteristics of the absorber, the difference of the maximum absorption frequency under temperature changes is about 1 GHz, however the absorption of 20 dB or more is obtained between 54 and 58 GHz. The result of accelerated artificial exposure test is that 2.8% of the thickness of our sample is shrunk after 1000 hour exposure, and the hardness of rubber is hardened with increasing test time. It is also confirmed that the deterioration of the absorption ranges from 1 to 3 dB, although the absorption of about 20 dB is kept at the frequency range. As a consequence, it is confirmed that the wave absorber using the epoxy-modified urethane rubber mixed with carbon particles has good weatherability including our desired temperature characteristics, and it is suitable for outdoor use.

An analog standard cell layout configuration is proposed for simplifying the design and reducing the man-hours for designing mixed analog-digital LSIs, and analog standard cells are fabricated for A-D and D-A converters with Δ-Σ modulators. This works seeks to implement 2-D cell placement with up-down and left-right mirror rotation and shorter high-impedance analog wiring than conventional 1-D placement in order to obtain high-performance analog characteristics. By considering sensitivity to noise, routing channels have been classified into 4 types: high-impedance analog, low-impedance analog, analog-digital, and digital, and efforts have been made to prevent analog wires from crossing over digital wires. In addition to power and analog ground wires, analog standard cells have built-in analog ground wires with attached wells optimized for shielding. These wires are interconnected to a new isolation cell that separates analog circuits from digital circuits and routing channels. Based on the above layout structure, 46 different types of analog standard cells have been designed. Also, the analog part of Δ-Σ type A-D and D-A converters can be automatically designed in conjunction with interactive processing and chips fabricated by using these cells. It was found that, compared to manual design, one could easily obtain a chip occupying less than 1.5-times the area with about 2/3 the man-days using this approach. In comparison with manual design, it was also found that the S/N ratio could be reduced from about 6 to 7 dB.

High-speed low-power matched filter plays an important role in the fast despreading of spread-signals in wideband code division multiple access (W-CDMA) mobile communications. In this paper, we describe the algorithm and the VLSI-architecture of a complex matched filter chip implemented by our proposed digital-controlled analog parallel operational circuits. The complex matched filter VLSI with variable taps from 4 to 128 is developed for despreading QPSK-modulated spread-signals for W-CDMA communications, which is fabricated by a 2-metal 0.8 µm CMOS technology. The dissipation power of the chip is 225 mW and 130 mW when it operates at the chip-rate of 20 MHz with the supply voltages of 3.0 V and 2.5 V, respectively, and it can be furthermore reduced to 62 mW at chip rate of 10 MHz when the supply voltage is lowered to 2.2 V. The 3-dB cut-off frequency of the fabricated chip is higher than 20 MHz for both 3.0 V and 2.5 V supplies. Comparing to pure digital matched filters, the massive and high-speed despreading operations of the spread-signals are directly carried out in analog domain. As a result, two high-speed analog-to-digital (A/D) converters operating at chip rate are omitted, the inner signal paths and the total dissipation power are greatly reduced.

We report on progress in the development of high current density NbN/AlN/NbN tunnel junctions for application as submillimeter wave SIS mixers. A ultra-high current density up to 120 kA/cm2, roughly two orders of magnitude larger than any reported results for all-NbN tunnel junctions, was achieved in the junctions. The magnetic field dependence and temperature dependence of critical supercurrents were measured to investigate the Josephson tunneling behaviour of critical supercurrents in the high-Jc junctions. We have developed a low-noise quasi-optical SIS mixer with the high-current density NbN/AlN/NbN junctions and two-junction tuning circuits which employ Al/SiO/NbN microstriplines. The tuning characteristics of the mixer were investigated by measuring the response in the direct detection mode by using the Fourier Transform Spectrometer (FTS) and measuring the response in the heterodyne detection mode with the standard Y-factor method at frequencies from 670 to 1082 GHz. An uncorrected double sideband receiver noise temperature of 457 K (12hν/kB) was obtained at 783 GHz.

Non-stationary glint noise is often observed in a radar tracking system. The distribution of glint noise is non-Gaussian and heavy-tailed. Conventional recursive identification algorithms use the stochastic approximation (SA) method. However, the SA method converges slowly and is invalid for non-stationary noise. This paper proposes an adaptive algorithm, which uses the stochastic gradient descent (SGD) method, to overcome these problems. The SGD method retains the simple structure of the SA method and is suitable for real-world implementation. Convergence behavior of the SGD method is analyzed and closed-form expressions for sufficient step size bounds are derived. Since noise data are usually not available in practice, we then propose a noise extraction scheme. Combining the SGD method, we can perform on-line adaptive noise identification directly from radar measurements. Simulation results show that the performance of the SGD method is comparable to that of the maximum-likelihood (ML) method. Also, the noise extraction scheme is effective that the identification results from the radar measurements are close to those from pure glint noise data.

This paper presents two types of two-variable analog filters with maximally flat magnitude-squared attenuation response in the two-dimensional pass region. These are applied in order to obtain five types for the distribution of two-dimensional pass regions with respect to the design of microwave band pass filters consisting of a cascade of commensurate-line filter and lumped LC filter or a cascade of two commensurate-line filters in different propagation times.

Weighted summation (W-SUM) operation of multi-input signals plays an important role in signal processing, image compression and communication systems. Conventional digital LSI implementation for the massive high-speed W-SUM operations usually consumes a lot of power, and the power dissipation linearly increases with the operational frequencies. Analog or digital-analog mixed technology may provide a solution to this problem, but the large scale integration for analog circuits especially for digital-analog mixed circuits faces some difficulties in terms of circuit design, mixed-simulation, physical layout and anti-noises. To practically integrate large scale analog or digital-analog mixed circuits, the simplicity of the analog circuits are usually required. In this paper, we present a solution to realize the parallel W-SUM operations of multi-input analog signals based on our developed digital-controlled analog operational circuits. The major features of the proposed circuits include the simplicity in the circuitry architecture and the advantage in the dissipation power, which make it easy to be designed and to be integrated in large scale. To improve the design efficiency, a Top-Down design approach for mixed LSI implementation is proposed. The proposed W-SUM circuits and the Top-Down design approach have been practically used in the LSI implementation for a series of programmable finite impulse response (FIR) filters and matched filters applied in adaptive signal processing and the mobile communication systems based on the wideband code division multiple access (W-CDMA) technology.

The optimum bias point for a drain mixer operating on low local oscillator (LO) power was investigated. The bias voltage dependence of the required LO power and the conversion gain in the drain mixer was clarified by a simplified nonlinear model which the drain current characteristics around knee voltage is approximated by two straight line segments. It was found that an optimum gate bias voltage Vgs exists for a given applied LO power, and the optimum gate bias voltage moves toward the pinch-off voltage as the injection LO power level decreases. In order to verify the variation of the optimum gate bias voltage, a 60 GHz MMIC drain mixer adopting the optimum gate bias voltage for low LO power level was fabricated. The fabricated drain mixer exhibited a conversion gain of 0 dB with the injection LO power level of 0 dBm. This value of 0 dBm is the best performance yet obtained for a 60 GHz MMIC drain mixer. The measured optimum gate bias voltage was near the pinch-off voltage. This result was in good agreement with the theoretical analysis. The LO power level of a drain mixer has been improved so that it is on a par with that of a gate mixer.

Effective wavelets to solve electromagnetic integral equations are proposed. It is based on the same construction procedure as Daubechies wavelets but with mix-phase to obtain maximum sparsity of moment matrix. These new wavelets are proved to have excellent performance in non-zero elements reduction in comparison with minimum-phase wavelet transform (WT). If further sparsity is concerned, wavelet packet (WP) transform can be applied but increases the computational complexity. In some cases, the capability of non-zero elements reduction by this new wavelets even better than WP with minimum-phase wavelets and with less computational efforts. Numerical experiments demonstrate the validity and effectiveness of the new wavelets.

This paper describes numerical analyses of resistive mixer operation, followed by measured performances of a V-band (50 - 75 GHz) monolithic InP HEMT resistive mixer operable with a very low LO power. Our model assumes that the channel conductance of the InP HEMT can be described by three linear functions according to the applied gate voltage. The calculated results obtained with the model have shown that the LO power level required for mixer operation is determined by the gate bias voltage and that a device with abrupt conductance shifts is suited to low LO power operation for a resistive mixer. It is also shown that conversion loss saturation of a resistive mixer is caused by its channel conductance saturation. A V-band monolithic resistive mixer has been designed and fabricated using Coplanar Waveguides (CPW) and a 0.15 mm InP HEMT with abrupt channel shifts. Good agreement between measured and simulated conversion losses are obtained. A minimum conversion loss of 8.4 dB is achieved at the 55 GHz RF-frequency and the -2 dBm LO power. It also exhibits an excellent IF output linearity to allow the 1 dB compression RF input level to be comparable with LO power, indicating good intermodulation performance. It is demonstrated that the proposed simple model of the channel conductance can easily calculate conversion characteristics of a resistive mixer with high accuracy.

A novel 1470-nm-band (S+ band) wavelength-division multiplexing (WDM) transmission system is described. The first advantage of S+-band transmission is suppression of degradation caused by four-wave mixing (FWM), which has been the dominant impairment factor in WDM transmission systems on dispersion-shifted fibers (DSFs). FWM suppression by using the S+ band instead of the conventional 1550-nm-band (M band) is successfully demonstrated. The second advantage is expansion of the usable bandwidth by using the S+ band together with other wavelength bands. A triple-wavelength-band WDM repeaterless transmission experiment using the S+ band, the M band and the L band (1580-nm-band) is conducted over DSF, and it is shown that degradation due to inter-wavelength-band nonlinear interactions is negligible in the transmission. Moreover, the transmission performance of an S+-band linear repeating system is estimated by computer simulation, and compared with that of other wavelength-band systems. In the experiments, thulium-doped fiber amplifiers (TDFAs) are used for amplification of signals in the S+ band.

A novel 1470-nm-band (S+ band) wavelength-division multiplexing (WDM) transmission system is described. The first advantage of S+-band transmission is suppression of degradation caused by four-wave mixing (FWM), which has been the dominant impairment factor in WDM transmission systems on dispersion-shifted fibers (DSFs). FWM suppression by using the S+ band instead of the conventional 1550-nm-band (M band) is successfully demonstrated. The second advantage is expansion of the usable bandwidth by using the S+ band together with other wavelength bands. A triple-wavelength-band WDM repeaterless transmission experiment using the S+ band, the M band and the L band (1580-nm-band) is conducted over DSF, and it is shown that degradation due to inter-wavelength-band nonlinear interactions is negligible in the transmission. Moreover, the transmission performance of an S+-band linear repeating system is estimated by computer simulation, and compared with that of other wavelength-band systems. In the experiments, thulium-doped fiber amplifiers (TDFAs) are used for amplification of signals in the S+ band.

This paper presents a review of the techniques and models that can be used for the noise performance calculation of active devices under linear and nonlinear operations. In a first part, the modeling techniques and the noise models of FETs, HEMTs, BJTs and HBTs are described. In the second part, a generalization of the impedance field method for the noise modeling in devices under nonlinear periodic operation is proposed. This method can be used for the modeling of microwave and millimeter wave mixers and oscillators.

A complex modular process flow was developed for PRISM technology to permit increased system integration. In order to combine the required functions--submicron CMOS Logic, Nonvolatile Memories, Precision Linear, and Power Drivers--on a monolithic silicon chip, a highly structured, systematic approach to process synthesis was developed. TCAD tools were used extensively for process design and verification. The 60 V LDMOS power transistor and the Flash memory cell built in the technology will be described to illustrate the process synthesis methodology.

We propose and describe a new configuration for splitting and combining operations of high-speed amplitude-modulated optical signals between the two interacting beams by using two-wave mixing in photorefractive Cu-doped (K0.5 Na0.5)0.2 (Sr0.61 Ba0.39)0.9 Nb2O6 (Cu-KNSBN) crystal. These operations are simultaneously achieved by changing the intensity ratio of the two incident beams. We also apply this scheme to a photorefractive pulse shaping in the time domain that consists of two amplitude-modulated beams that are coupled automatically through two-beam interactions in the crystal. Some preliminary experimental results are presented and discussed.

We have demonstrated the single-chip RF front-end GaAs MMIC for the Japanese Personal Handy-phone System. It has a high efficiency HPA, a T/R switch, a LNA and a low-distortion down converter mixer. The IC employs a negative voltage generator for use of single voltage DC power supply. The HPA provides an output power of 21.5 dBm, with an ACPR of 55 dBc and an efficiency of 35%. The LNA has a noise figure of 1.6 dB and a gain of 14 dB with current of 2.3 mA. The newly developed active cascode FET mixer has a high IIP3 of 1 dBm with a high conversion gain of 10 dB and low consumption current of 2.3 mA. The IC is characterized by high performance for RF front-end of PHS handheld terminals. The IC is available in a 7.0 mm6.4 mm1.1 mm plastic package.

This paper describes the distortion characteristics of an even harmonic type direct converter (EH-DC) used in earth stations for CDMA satellite communications. Direct conversion technique is known as a method to simplify circuit topologies of microwave transceivers. In satellite communications, multi carriers which have high and nearly equal level are provided to a quadrature mixer of the EH-DC. Hence, the third-order intermodulation degrades receiving characteristics. In this paper, we show the relationship between the distortion characteristics and noise figure of the EH-DC for CDMA satellite communication systems. Furthermore, we show NPR of even harmonic quadrature mixers caused by the third-order intermodulation. Experimental results in X-band indicate that the proposed EH-DC has almost the same BER characteristics compared with a heterodyne type transceiver.

For given undirected graph G[V,E] and vertices s and t, a minimal s-t separating set denoted by Ec & Vc is a minimal set of elements (edges and/or vertices) such that deletion of the elements from G breaks all the paths between s and t, where Ec and Vc are sets of edges and vertices, respectively. In this paper, we consider a problem of generating all minimal s-t separating sets, and show that the problem can be solved in O(µ(mt(n,n))) time, where m|E|, n|V|, µ is the number of minimal s-t separating sets of G, and t(p,q) is the time needed for finding q lowest common ancestors for q pairs of vertices in a rooted tree with p vertices. Since t(n,n) can be O(n), we can generate all minimal s-t separating in linear time per s-t separating set. However, the linear time algorithm for finding the lowest common ancestors is complicated, so that it is not efficient for a moderate size graph. Therefore, we use an O(nα (n))-time algorithm for finding the lowest common ancestors, and propose an algorithm to generate all minimal s-t separating sets in O(mnα(n)) time per s-t separating set, where α(n) is the pseudo-inverse of Ackermann function.