“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.

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 -3.20.2 dB, return losses greater than 20 dB, and isolation between output ports greater than 20 dB.

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 -6.510.29 dB, return losses of greater than 13 dB, errors in the desired relative-phase difference between output ports of less than 2 degrees.

This paper describes a simple design of a broad-band four-way power divider with 45-degree phase differences between output ports. In the first stage of our work, we present a new broad-band 90-degree power divider. The phase error of the power divider here is less than one-tenth of the conventional 90-degree branch-line hybrid. Next, an experimental UHF-band four-way power divider using a broad-band 90-degree power divider and two broad-band 45-degree power dividers is presented. Over the frequency range from 0.86 to 1.06 GHz, the experimental four-way power divider exhibits power splits of -6.420.25 dB, return losses of greater than 15 dB, errors in the desired relative-phase difference between output ports of less than 1 degree, and isolation between output ports of greater than 15 dB. This divider is useful for realizing low distortion and high efficiency amplifiers without the need for an isolator.

Data comparison and trigger skip methods are proposed to extract truly synchronized trigger from a high speed repetitive waveform to be observed on a CRT or to be written in a partially sequential digital sampling storage circuit. So far, there have been no way to automatically extract truly synchronized trigger from the input repetitive waveform in a multi-period sampling system, when an external synchronizing signal is not accompanied. Trigger extraction mechanisms from various kinds of repetitive waveform, for which, especially, a number of triggers can generate during its fundamental period are theoretically analysed. Based on the results, the principle and effectiveness of this system for various types of the waveform are described. The input waveform is taken twice in the sampling storage circuit, and successively taken two sample value streams are compared with each other. These two should agree if both are taken in the same portion of the waveform fundamental period. If they do not agree, it is judged to be due to incorrect trigger extraction, and the trigger skip number is increased. Data taking and comparison is repeated by increasing the trigger skip number untill two successively taken data streams agree with each other. Performance estimation tests of fabricated data comparison and trigger skip circuits were made using computer produces test signal, and the results showed the reliable digital data storage and simple operation.

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. 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 signal divider and combiner. This MMIC combines a set of amplifiers with a set of dividers having a constant phase difference of 90. 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 coupler. At the frequency of 140 MHz, the mean transmission loss is about 2. 1 dB for the divider part 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.

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 50Ω, the proposed VCO can oscillate against a 50Ω 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 4.41.0 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 mm2, 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 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.

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 -51 dBm. This is a promising technique for a variety of devices, including optically controlled oscillators, filters, phase shifters, and active antennas.

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 0power divider with a filtering function had a chip size about half that of a conventional lumped-element one. Its insertion loss at 0.950.05 GHz was 4.00.1 dB.

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 FETs are set appropriately. The chip size of the fabricated active inductor is less than 0.52 mm2. 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 proposes a low distortion technique which reduces transmitter intermodulation. It is shown that one of the third order transmitter intermodulation products generated can be reduced by using a parallel amplifier configuration which includes a 45 divider and a 45 combiner. It is already known that the other third order transmitter intermodulation product can be reduced by using a parallel amplifier configuration using 90 hybrids. Thus, all of the third order transmitter intermodulation can be reduced by combining these configurations. This paper also shows the experimental results obtained with a parallel amplifier using 90 hybrids and one using a 45 divider and combiner in the K-band. The spectra of these amplifiers are compared, and it is found that third order transmitter intermodulation can be reduced by more than 29 dB in the parallel amplifier using the 45 divider and combiner.

An MMIC variable-gain amplifier, which improves the transmission phase deviation caused by gain control, is presented. At first, it is shown that by controlling both the common-gate FET's gate bias voltage and the common-source FET's gate bias voltage, the transmission phase deviation caused by gain control of the variable-gain amplifier using a cascode-connected FET is greatly improved. In this case it is not desirable to control both of the gate bias voltages independently, because of the complexity. Thus we propose two simple gate bias voltage control circuits controlling both of the gate bias voltages, in which only one of the two gate bias voltages is controlled independently and the other is controlled dependently. Then we apply these circuits to the 1. 9-GHz-band variable-gain amplifier using the cascode-connected FET. One of the control circuits is the gate bias voltage control circuit using two resistors. It is confirmed that, by applying the newly proposed circuit, phase deviation is suppressed, from between 0and 30to between 3and 5, with 25-dB gain control. The other circuit is the gate bias voltage control circuit using the FET's nonlinear characteristics. It is confirmed that, by applying the newly proposed circuit, phase deviation is suppressed, from between 0and 44to between 6and 3 with 30-dB gain control. This is a promising technique for reducing the transmission phase deviation caused by gain control of the amplifiers used in active phased array antennas.

A feedforward (FF) network using ΔΣ modulators is investigated to implement a non-binary analog-to-digital (A/D) converter. Weighting coefficients in the network are determined to suppress the generation of quantization noise. A moving average is adopted to prevent the analog signal amplitude from increasing beyond the allowable input range of the modulators. The noise transfer function is derived and used to estimate the signal-to-noise ratio (SNR). The FF network output is a non-uniformly distributed multi-level signal, which results in a better SNR than a uniformly distributed one. Also, the effect of the characteristic mismatch in analog components on the SNR is analyzed. Our behavioral simulations show that the SNR is improved by more than 30 dB, or equivalently a bit resolution of 5 bits, compared with a conventional first-order ΔΣ modulator.

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.

This paper demonstrates a polyimide/alumina-ceramic multilayer MIC analog phase shifter with a large phase shift. First, a novel active inductor, similar to the previously reported active inductor but with a shunt variable resistor inserted in the feedback loop, is proposed for miniaturizing the circuit. The chip size of the fabricated GaAs MESFET active inductor is less than 0. 52 mm2. Next, a low-loss analog phase shifter with a large phase shift is presented. This is constructed in an MIC structure with the active inductors, the varactor diodes and the low-loss polyimide/alumina-ceramic multilayer broad-side coupler. Furthermore, since the amount of the phase shift is the sum of the two individual tuning ranges attributed to the active inductors and varactor diodes, a large phase shift is obtained compared to the case where only the varactor diodes are tunable. Thus, a phase shift of more than 270 within 2-dB insertion loss from 2. 1 to 2. 4 GHz is obtained with the fabricated single-stage reflection-type analog phase shifter. The total power consumption is less than 80 mW.

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/f0) by about 80% as compared to conventional lumped-element dividers).