林 等

This paper presents a miniaturized 4-way power divider with 45° phase differences between output ports. The divider is developed by combining a 90° Lange coupler and broadband 45° power dividers, and is implemented on an FR4 substrate. The measurement results reveal the feasibility of the proposed power divider configuration for effectively reducing transmitter intermodulation.

This paper presents a Lange 3 dB 90° hybrid. The hybrid consists of two 8.34-dB Lange couplers connected in tandem and is implemented on a 4-layer flame resistant laminate, composed of woven fiberglass cloth with an epoxy resin binder (FR4) substrate, by using inner-layer crossovers, instead of conventional bonded crossovers. Owing to its optimized tandem structure and inner-layer crossovers, for operating characteristics within the frequency range 440–760 MHz, the hybrid exhibits a power coupling of 3.5 ± 0.6 dB and return losses greater than 23 dB. Furthermore, isolation and phase difference between the output ports is greater than 29 dB and 90° ± 1°, respectively.

We present a high-speed start-up and low-power encoding circuit for sensor networks. The Manchester code that is currently used for Ethernet (IOBASE-T), non-contact IC card, and RFID requires a phase-locked loop (PLL) because intervals of the state transition change. On the other hand, in the proposed circuit, state transitions occur periodically at the center of a waveform through the use of the encoding method involving several waveforms.

Security is one of the most important factors for success of smart grid services. This paper presents the security requirements for smart grid services in Japan. We consult two major documents for smart grid security in the U.S. and EU, "NISTIR 7628" and CEN's "the Smart Grid Information Security", and discuss the results of the security requirements extracted from these documents.

"Internet of Things" (IoT) requires information to be collected from "anything", "anytime", and "anywhere". In order to achieve this, wireless devices are required that have (1) automatic data acquisition capability, (2) small size, (3) long life, and (4) long range communication capability. One way to meet these requirements is to adopt active Radio Frequency Identification (RFID) systems. Active RFID is more advantageous than passive RFID and enables higher data reading performance over longer distances. This paper surveys active RFID systems, the services they currently promise to provide, technical problems common to these services, and the direction in which research should head in the future. It also reports the results of EPCglobal (EPC: Electronic Product Code) pilot tests conducted on global logistics for tracking ocean/air container transportation using active RFID systems for which we developed several new types of active RFID tags. The test results confirm that our active RFID tags have sufficient capability and low power consumption to well support ocean/air transportation and logistics service.

For the Internet of Things, wireless devices are required that have small size, long life, and long range communication capability. One technology that meets these requirements is the wide-area ubiquitous network. This paper reports the field trials conducted over three years services were remote reading /remote control of gas meters and bicycle management (location estimation /radio reachability). The test results confirm that the network can well support remote monitoring service. © 2012 IEEE.

This article describes the system concept of a wide-area ubiquitous network that connects compact wireless terminals economically and allows communication with objects. It also introduces some services that can be provided on this network, discusses the business areas that the network is expected to support, and gives examples of the network’s usage.

小型の無線端末を経済的に収容し，モノとの通信を実現する広域ユビキタスネットワークのシステムコンセプト，および提供可能なネットワークサービスを紹介するとともに，想定するビジネス領域と具体的な利用方法について紹介します．

Three miniaturized lumped-element power dividers with a filtering function for use in quadrature mixers are described. Simulation results showed that they can be miniaturized, as compared to conventional ones with open/short stubs, while maintaining the filter characteristics. A fabricated 0.95-GHz 0 degrees power divider with a filtering function had a chip size about half that of a conventional lumped-element one. Its insertion loss at 0.95 +/- 0.05 GHz was 4.0 +/- 0.1 dB.

This paper describes a miniaturized in-phase power divider with a DC block function. We first propose three types of miniaturized in-phase power dividers composed of two distributed transmission lines, a resistor, and three capacitors to function as a DC block. Then, we use a simulation to compare the dividers. The simulation results show that. by properly selecting circuit configuration, we both achieve broadband frequency characteristics and miniaturize circuitry as compared to the conventional Wilkinson power divider with two DC block capacitors. Finally, an experimental UHF power divider fabricated to test the design concept is presented. Over the frequency range from 0.44 to 0.66 GHz, the experimental power divider exhibits power splits of -3.2 +/- 0.2 dB, return losses greater than 20 dB. and isolation between output ports greater than 20 dB.

This paper describes miniaturized broadband lumped-element in-phase power dividers. We first propose two types of miniaturized broadband lumped-element in-phase power dividers composed of two inductors, a resistor, and two capacitors. Next, we use a simulation to compare these dividers with conventional power dividers. The simulation results reveal that the proposed lumped-element in-phase power dividers can help miniaturize circuits (by decreasing inductances by about 30%, reducing the number of necessary capacitors by half, and decreasing necessary capacitances by about 30% as compared to conventional lumped-element dividers) and attain broadband frequency characteristics (by increasing normalized operating frequency bandwidths (f/fo) by about 80% as compared to conventional lumped-element dividers).

This paper describes a broadband active terminal circuit and its application to a distributed amplifier. In this study, we first analyzed and compared three types of active terminal circuits using representative circuit configurations, namely, an active terminal circuit with a common-emitter BJT, an active terminal circuit with a Darlington BJT pair, and an active terminal circuit with cascode-connected BJTs. The simulation results showed that the active terminal circuit with cascode-connected BJTs kept the matching condition up to high frequency. After the simulation, we fabricated a distributed amplifier that used an active terminal circuit with cascode-connected BJTs. The RF amplifier achieved a flat gain of 9.7 +/- 1.0 dB over a range of 3-15 GHz.

There are various mobile communication standards in use worldwide. Software defined radio (SDR), which enables the creation of multi-standard terminals, is the one of the best ways to achieve seamless mobile communications. To realize an SDR mobile terminal, it is necessary to minimize terminal size and power consumption. NTT developed an RF chipset for a multi-band transceiver and a signal processing board using a reconfigurable processor. This paper describes its implementation and the performance of the multi-band RF chipset along with the results of an evaluation of the signal processing unit.

We have developed an asset tracking system using long-life active RFID (radio frequency identifica-tion) tags that reports the position of an asset when required. To determine the location of a tag attachedto an asset indoors, such as in stores, warehouses, and offices, we use a high-precision location systemthat is not greatly affected by environmental factors. Experimental results show that the root-mean-square error between the estimated and actual tag positions measured at 77 points is 2.9 m, indicatingthat this locating system is applicable not only to asset tracking but also to other ubiquitous services thatutilize the position of an item or a person indoors.

In a software-defined radio, the RF (Radio-Frequency) front-end must cope with multi-band radio sig-nals. Therefore, we developed a wideband RF chipset for multi-band direct conversion transceivers. Thechipset consists of a wideband quadrature mixer, a wideband low-noise variable-gain amplifier(LNVGA), and a multi-band local oscillator. The mixer achieves its wideband performance through theincorporation of newly developed power dividers. The LNVGA attains its wideband performance with-out the use of reactance elements. It also has high linearity due to a feedback circuit using two anti-seriesfield-effect transistors. The local oscillator is able to cover the frequency bands of three systems, includ-ing a frequency-division duplexing system, while using only two voltage-controlled oscillators.

A broadband RF front-end having a direct conversion architecture has been developed. The RF front-end consists of two broadband quadrature mixers, a multi-band local oscillator, and a broadband low-noise variable gain amplifier (LNVGA). The mixer achieves broadband characteristics through the incorporation of an in-phase power divider and a 45-degree power divider. The in-phase power divider achieves broadband characteristics through the addition of a compensation capacitor. The 45-degree power divider achieves broadband phase characteristics through the addition of a compensation capacitor and a compensation resistor. The local oscillator, which is composed of two VCOs, two frequency dividers, and four switches, can cover three systems including one FDD system. The LNVGA achieves its broadband characteristics without the use of reactance elements, such as inductors or capacitors. In a trial demonstration, when the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a demodulator experimentally demonstrated an amplitude balance of less than 1.6 dB and a quadrature phase error of less than 3 degrees. When the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a modulator demonstrated an image ratio of less than -30 dBc. The local oscillator demonstrated multi-band characteristics, which are able to cover the target frequencies for three systems (PDC, PHS, 2.4 GHz WLAN). From 900 MHz to 2.5 GHz, the amplifier shows a noise figure of less than 2.1 dB and a gain of 28 1.6 dB.

The "person-to-person" communications market is becoming saturated, prompting an interest in the "object-to-object" communications market. "Object-to-object" communications technology uses a large number of mobile devices that transmit information at low speed. It is especially useful in management of distribution systems and warehouse inventories. The attractiveness of the technology from the service provider's standpoint is that we can set the communication unit price per bit high compared with broadband services. In this article, we will introduce a position information service that uses small wireless tags to keep track of objects.

This paper describes a radial open stub and its application to a simple design of a four-element planar Butler matrix. In the first stage of our work, we propose a 45-degree phase shifter composed of an eighth-wavelength delay line and a serial connection of a quarter-wavelength straight line and a quarter-wavelength straight open stub. Next, in order to improve relative-phase characteristics between output ports, we propose a 45-degree phase shifter configuration using a quarter-wavelength radial open stub instead of using a quarter-wavelength straight open stub. It is shown by simulation that relative-phase characteristics of the configuration using the radial open stub are better than that using the straight open stub at the high frequencies, Finally. an experimental UHF-band four-element planar Butler matrix is presented. Over the frequency range from 0.83 to 0.92 GHz. the experimental four-element planar Butler matrix exhibits power splits of -6.51 +/- 0.29 dB, return losses of greater than 13 dB. errors in the desired relative-phase difference between output ports of less that 2 degrees.

A comprehensive analysis of an active balanced frequency doubler is described and proposed as a new concept: tuning the center frequency at which the doubler exhibits its highest performance to extend the usable bandwidth of the device. The concept is validated using a fabricated V-band pseudomorphic high electron-mobility transistor frequency doubler. For this device, a substantial improvement in the usable bandwidth (more than double) is achieved, demonstrating that the proposed concept is particularly suitable for the realization of high spectral purity and widely tunable V-band frequency sources.

A simple design of a four-element planar Butler matrix is presented, comprising half-wavelength open stubs to improve relative-phase characteristics between output ports. Over the frequency range from 0.85 to 0.90 GHz, the experimental matrix exhibits phase errors (in the desired phase differences between output ports) and couplings of within 2degrees and -6.45 +/- 0.25 dB, respectively.

This paper describes a miniaturized monolithic-microwave integrated-circuit (MMIC) analog phase shifter using two quarter-wave-length transmission lines. A conventional analog phase shifter employs an analog phase-shifter topology using a 3-dB 90degrees branch-line hybrid requiring four quarter-wave-length transmission lines. Thus, in the first stage of our study, we present a new analog phase-shifter topology using only two quarter-wave-length transmission lines. The phase shifter here has only one-half as many transmission lines as a conventional analog phase shifter using a 3-dB 90degrees branch-line hybrid, and the circuit can be miniaturized to less than one-fourth as compared to the conventional analog phase shifter. Furthermore, we show that the operating frequency range of the phase shifter is very wide and can obtain large phase variation with small capacitance variation. Next, an experimental Ku-band MMIC analog phase shifter is presented. A phase shift of more than 180degrees and an insertion loss of 3.6 +/- 1.1 dB are obtained at the frequency range from 12 to 14 GHz. The chip size of the experimental MMIC phase shifter is less than 3.0 mm(2).

A broadband radio frequency (RF) front-end for direct conversion transceivers has been developed. The RF front-end consists of a broadband low-noise variable gain amplifier (LNVGA) and broadband quadrature mixers. The LNVGA achieves high linear characteristics by using a feedback circuit and broadband characteristics by not using reactance elements such as inductors or capacitors. The mixer achieves broadband characteristics through the incorporation of a in-phase power divider and a 45-degree power divider. The in-phase power divider achieves broadband characteristics through the addition of a compensation capacitor. The 45-degree power divider achieves broadband phase characteristics through the addition of capacity to increase the resonance point. From 0.9 GHz to 2.6 GHz, the LNVGA shows a noise figure of less than 2.1 dB and a gain of 28+/-1.6 dB. The mixer for a demodulator shows an amplitude error of less than 1.6 dB and a phase error of less than 3 degrees. The mixer for a modulator shows an image ratio of less than -30 dBc.

A wideband direct conversion receiver for multi-band applications is presented. The developed receiver consists of one quadrature downconverter, one low-noise amplifier (LNA), and two voltage-controlled oscillators (VCOs). The key component ICs are fabricated on GaAs and Si substrates. The receiver can receive three different frequency bands, i.e., the 900 MHz band, 1.9 GHz band, and 2.4 GHz band.

This paper describes a small RF front-end for a 1.9-GHz direct-conversion receiver that uses power dividers of a newly developed type. The developed power divider is passive and its chip size is half that of a divider of the conventional type. The fabricated 1.9-GHz gain-controlled RF front-end has a small amplitude error of less than 0.4 dB and a small phase error of less than 3 degrees for an input signal with a power level below -10 dBm.

This paper describes a low-noise distributed amplifier that uses cascode-connected bipolar junction transistors (BJT) terminal circuit. This amplifier has a lower NF compared with a resistance-terminated distributed amplifier, yet has an equivalent frequency characteristic, because the cascode-connected BJTs terminal circuit improves noise performance at low frequencies and keeps the matching condition up to high frequency. The noise figure of the fabricated amplifier was less than 8.3 dB over a range of 0.1-8 GHz, which was about I dB better than that of a conventional distributed amplifier, without deterioration in gain and bandwidth. We obtained a flat gain characteristic of 9.7 +/- 1.0 dB over a range of 3-15 GHz.

In this letter, we present the design and measured performances of a Ka-band frequency doubler fabricated using 0.15 mu m GaAs pseudomorphic HEMT transistors and the three-dimensional (3-D) MMIC technology. Thank to the use of an improved 180 degrees rat-race hybrid, the frequency doubler exhibits high spectral purity over a large bandwidth. Isolation better than 30 dB is achieved on a frequency range from 31.7-36 GHz and fundamental frequency rejection better than 35 dB is achieved between 31.5 GHz and 37.5 GHz. Conversion loss measured at 32.5 GHz is 8.5 dB for an input power of 14 dBm, Both the broadband spectral purity and the small size of 1 mm(2) make it suitable for the realization of high-quality and widely tunable V-band frequency sources. For the future developments of millimeter-wave wireless communication systems, it offers good perspectives toward the fabrication of single-chip V-band transceiver including the frequency source.

A resonant-tunneling high-electron-mobility transistor (RTHEMT) doubler with matching circuits is described. We obtained a large conversion gain even at low input power, which was due to the strong nonlinearity of the RTHEMT. The conversion gain was 1.5 dB for a -10 dBm input signal at 2.4 GHz. Power consumption was only 4 mW, which was one-fifth that of a doubler using a GaAs metal-semiconductor field effect transistor (MESFET). The maximum reflection loss was 6 dB at 2.4 GHz.

This paper describes a monolithic-microwave integrated-circuit (MMIC) active phase shifter using a variable resonant circuit with a large amount of variable phase. We first propose a novel active phase-shifter configuration that uses a variable resonant circuit with second-order all-pass network characteristics. Phase can be changed with a constant amplitude by varying the capacitance or the inductance of the resonant circuit. Next, an experimental MMIC active phase shifter with input active matching is presented, A phase shift of over 100 degrees and an insertion loss of 4+/-1 dB are obtained from 2.2 to 2.8 GHz, The chip size is less than 1.0 mm(2), Finally, an experimental 360 degrees MMIC active phase shifter is presented, Over the bandwidth of 40 MHz at 2.44 GHz, the insertion gain is 2.0+/-0.7 dB and the phase error is within +/-4 degrees when measured in 30 degrees steps.

This paper proposes a novel broad-band MMIC VCO using an active inductor. This VCO is composed of a serial resonant circuit, in which the capacitor is in series with an active inductor that has a constant negative resistance. Since the inductance value of this active inductor is inversely proportional to the square of the transconductance and can vary widely with the FETs gate bias control, a broad-band oscillation tuning range can be obtained. Furthermore, since this active inductor can generate a constant negative resistance of more than 50 Ohm, the proposed VCO can oscillate against a 50-Ohm output load immediately without using additional impedance transformers. We have fabricated the VCO using a GaAs MESFET process. A frequency tuning range of more than 50%, from 1.56 to 2.85 GHz, with an output power of 4.4 +/- 1.0 dBm, was obtained. With a carrier of 2.07 GHz, the phase noise at 1-MHz offset was less than -110 dBc/Hz. The chip size was less than 0.61 mm(2), and the power consumption was 80 mW. This broad-band analog design can be used at microwave frequencies in PLL applications as a compact alternative to other types of oscillator circuits.

This paper presents a novel distortion compensation technique using an active inductor. First, we describe the input-reflection-coefficient characteristics of a GaAs MESFET active inductor when input power increases. We show that the inductor exhibits positive amplitude deviation and negative/positive phase deviation as the input power increases when the biases of the FBTs are set appropriately. The chip size of the fabricated active inductor is less than 0.52 mm(2). Then, we show that third-order intermodulation is improved when the active inductor is used as a predistortion linearizer. Third-order intermodulation was improved over the output range from 14 dBm to 25 dBm, and at the output of 15 dBm, third-order intermodulation was improved approximately by 9 dB when the predistortion linearizer was introduced. The active inductor can thus function as a miniaturized predistortion linearizer by using it in the input matching circuit of a power amplifier. This technique can be applied in the miniaturization of wireless communication devices.

This paper demonstrates millimeter-wave-band amplifier and mixer monolithic microwave integrated circuits (MMIC's) using a broad-band 45 degrees power divider/combiner. At first, we propose a broad-band 45 degrees power divider/combiner, which combines a Wilkinson divider/combiner, 45 degrees delay line, and 90 degrees short stub. A coupling loss of 4.0 +/- 0.2 dB and a return loss and an isolation of more than 19 dB with 45 +/- 1 degrees phase difference was obtained from 17 to 22 GHz for the fabricated K-band MMIC 45 degrees power divider/combiner. Next, a parallel amplifier using the broad-band 45 degrees power divider/combiner, which can be used in a power-combining circuit configuration requiring no isolator, is shown. Comparing the transmitter intermodulation generated in the parallel amplifier using the broad-band 45 degrees power divider/combiner and that generated in the one using the conventional type, the broad-band suppression effect was confirmed. Finally, an application of the broad-band 45 degrees power divider/combiner to a single-sideband (SSB) subharmonically pumped (SHP) mixer requiring no LF switch is shown, In an RF frequency range from 22.89 to 26.39 GHz, the fabricated K-band MMIC mixer achieved (for up-conversion) the good results of more than -13-dB conversion gain and more than 24-dB image-rejection ratio, These contribute significantly to the miniaturization of millimeter-wave communication equipment.

Recently fiber optic links have been applied to radio signal distribution networks and also to signal feeder networks for phased array antennas, because they are able to offer wide bandwidth for achieving the high bit-rates and large capacity needed in the multimedia age. In these networks, a great many modules are needed to convert optical signals to radio signals. In order to reduce the complexity and cost of these modules, direct optical control techniques, which inject optical signals directly into microwave circuits, are very attractive. Thus, this paper proposes a novel optical control technique using tunable inductance circuits. This technique employs direct illumination as a means of optically tuning the inductance. Since the inductance value is inversely proportional to the square of the transconductance, it varies widely when the FET is directly illuminated. With direct illumination, the measured inductance variation in an experimental inductance circuit built with Pseudomorphic AlGaAs/InGaAs/GaAs HEMTs is more than 20 % from 0.5 to 2 GHz. As an application, a direct optically controlled oscillator was fabricated. The measured optical tuning range of the oscillation frequency is more than 19 % with an output power of -5+/-1 dBm. This is a promising technique for a variety of devices, including optically controlled oscillators, filters, phase shifters, and active antennas.

This paper proposes a novel broad-band MMIC VCO using an active inductor. This VCO is composed of a serial resonant circuit, in which the capacitor is in series with an active inductor that has a constant negative resistance. Since the inductance value of this active inductor is inversely proportional to the square of the transconductance and can vary widely with the FETs' gate bias control, a broad-band oscillation tuning range can be obtained. Furthermore, since this active inductor can generate a constant negative resistance of more than 50 Ω, the proposed VCO can oscillate against a 50-Ω output load immediately without using additional impedance transformers. We have fabricated the VCO using a GaAs MESFET process. A frequency tuning range of more than 50%, from 1.56 to 2.85 GHz, with an output power of 4.4±1.0 dBm, was obtained. With a carrier of 2.07 GHz, the phase noise at 1-MHz offset was less than -110 dBc/Hz. The chip size was less than 0.61 mm^2, and the power consumption was 80 mW. This broad-band analog design can be used at microwave frequencies in PLL applications as a compact alternative to other types of oscillator circuits.

A power combining circuit configuration requiring no isolator is presented. As the configuration enables all orders of intermodulation to be reduced, it promises to contribute significantly to the miniaturization of millimeter-wave communication equipment.

This paper proposes a set of three IF-band MMICs for high-speed wireless communication systems. The first of the circuits in this chip set is an MMIC logarithmic limiting receiver amplifier. This amplifier utilizes the self-phase distortion compensation technique, combining a common-source FET and a common-drain FET, to reduce phase distortion. The limiting characteristics were gain of more than 65 dB, 2.2-dBm saturated output power and phase deviation of less than 5 degrees. A logarithmic accuracy of 2 dB and RSSI change coefficient of more than 11 mV/dB were also achieved. Typical power consumption was less than 0.58 W with the supply voltages of +3 V and -2 V. The second of the fabricated circuits is an MMIC transmitter amplifier with more than 24-dB gain at 140 MHz. And the third of the fabricated circuits is an MMIC 90 degrees signal divider and combiner. This MMIC combines a set of amplifiers with a set of dividers having a constant phase difference of 90 degrees. Thus the isolation between the transmission port and the reception port is obtained. The chip size is less than 1/100 that of a commercial 140-MHz-band 90 degrees coupler. At the frequency of 140 MHz, the mean transmission loss is about 2.1 dB for the divider parr and 3.0 dB for the combiner part. Furthermore, in the frequency range of 130 MHz to 150 MHz, signal leakage from the transmission port to the reception port is suppressed by more than 24 dB.