Ken Takei

An Experimental Study of Passive UHF RFID System with Longer Communication Range

Radio-frequency identification (RFID) systems are useful for reducing costs in supply chains. The communication range between the reader and the tag is one of the most important points in the application of RFID to supply chain management. We present results of experiments conducted on our passive RFID prototype system that we designed with the aim of increasing the communication range. It uses an intermittent transmission method to reduce the power consumption of the tag IC. Our results show that the power consumption was reduced to about three-quarters by using intermittent transmission with a duty ratio of 40%. Our experimental results indicate that optimization of the transmitting signal is effective for saving power consumption at tag IC and increasing the communication range.

Polarization angle diversity for highly-reliable machine-to-machine radio

A radio architecture is proposed for the wireless monitoring and control of infrastructure equipment. The proposed architecture is useful for machine-to-machine communication using non line-of-sight waves that are multiply reflected by electromagnetic scatters, i.e., with equipments that is much larger than the radio. The proposed radio transmits the signal, which is expanded by orthogonal codes, on different wireless paths using different polarization directions at different times. This communication approach results in good resistance against outer interferences and unexpected interruption, which enables it to achieve highly-reliable wireless communication. We designed a prototype radio in 400MHz band. Simulation results indicate that 100kHz data could be successfully reconstructed through 46MHz coding/decoding and 93MHz modulation/demodulation. The 5x up-conversion is enabled by the band-pass delta-sigma circuit that contains digital parts in a commercial field programmable gate array. The prototype radio exhibited a carrier to noise ratio of more than 30dB.

Low-noise, Low-distortion Front-end IC For 1.1 -V Paging Receiver

A front-end IC for a 1.1-V, VHF paging receiver has been developed. Using a novel low-noise, low-distortion amplifier, it achieves a high sensitivity of -130 dBm and a low intermodulation sensitivity of -20 dBm while consuming only 1.98 mW. A 2.93-dB noise figure and a +5.0-dBm third-order intercept point are achieved under 50- Omega matching. >

Use of adaptive reactance control in optimum antenna design for transmitting power in near-mid ranges

To transmit power efficiently thought wireless network in the near-mid range, we propose the use of a novel power transmitting system. The system uses the adaptive reactance control and the suitable antenna structure enhancing this control. Simultaneous control of variable reactance attached to both transmitting receiving antennas allows power to be transmitted more efficiently than conventional simple impedance matching between antenna and circuitry. The evaluation function of the newly-derived power transmission efficiency under adaptive reactance control has a further function; it can be used with the numerical trial and error searching method in an antenna structure to identify novel structures that can improve transmission power. Analysis of a design of the proposed system with numerically-found antennas reviles that the system with adaptive reactance control and our antenna transmitted power ten times more efficiently than one that uses a conventional impedance matching method and a conventional antenna such as a dipole and a loop antennas.

Auto Search Algorithm for Antenna Structure by Gradient Method Combined with Method of Moment

We propose a novel antenna design method consisting of the gradient method and method of moment is proposed. An antenna structure is represented by the combination of small segments. By regarding the 0/1 state segment variable as a real parameter, a matrix equation for the gradient method is derived. Fast computation causing of automatic decisions of simultaneous changing segments achieves practical design for various antennas, including large-scale antennas.

Channel estimation in rotating polarization based wireless communication systems

In a slow fading/fixed environment, a deep fade might last for several symbol durations, and all the transmissions during such a deep fade become highly unreliable. Rotating polarization is an RF technique to artificially induce fading in a static environment, and thus reduce the chance of prolonged deep fades. However, this technique makes the channel vary at a high rate and hence increases the complexity of channel estimation. In this paper, we look at channel estimation in systems using rotating polarization. Drawing parallels from MIMO systems, we propose a technique for designing a training sequence that reduces the complexity of channel estimation while providing good performance in an induced fast fading environment. We analyse the performance of the least-squares and minimum mean square error channel estimation techniques with rotating polarization.

Orthogonal code for polarization angle division diversity

The polarization angle diversity uses different angle regions of the polarization to transfer a signal that is multiplied by the special codes in these regions. These special codes have both local and global orthogonalities and are cyclic because the entire region is 360 degrees. The entire code and independent parts of this code both have very weak mutual correlation to their cyclic shift and each other to achieve the global and local orthogonalities. The orthogonal balanced code is proposed as a candidate for this special code. Both the local and global orthogonalities of the proposed code are numerically examined by comparing them with the two codes that are based on M-series. The numerical results indicate that the proposed code not only has both strong local and global orthogonalities but also shows the frequency spectrum whose occupied bandwidth and peak value are respectively very narrow and low. These characteristics ensure usefulness of the code for the polarization angle diversity.

Stochastic analysis for rotating polarization communication with multi-reflection waves in multipath environment

To compensate for the phase fluctuation of the arriving wave that experiences many reflections off conducting surfaces, a wireless communication method using a polarization rotating wave is proposed. The proposed method reduce the phase fluctuation by adaptively controlling the polarization rotating frequency. The proposed method is applied to stochastic models of communication, when that the number of reflections is low and high. The probability distribution function of the received waves is derived in these cases. The bit error rates of the communication are derived by using the proposed method for synchronous and delay detections. The numerical results of the bit error rates indicate that the polarization rotating wave improve communication quality in multipath environment without line-of-sight waves.

Efficient computational design for an antenna with a finite ground plane

An efficient method for computational design for an antenna with a finite ground plane was devised. A matrix equation by means of using voltage flows was formulated by using an inverse-matrix/reverse-equation method within the method-of-moment (MoM) framework. Double-layered -zigzag-indexing for discretized induced currents provides a matrix equation incorporating a small work area. The radiation power expressed by voltage flows that appear only in this area is derived. Matrix equation based on voltage flow and radiation power enables practical computational design of an antenna by using a commercial PC with small memory.

FPC-free LCD panel with capacitive coupling for transmission of signals and power

— A flexible-printed-cable (FPC) free liquid-crystal-display (LCD) panel by using a capacitive-coupling technique has been developed. A QQVGAeight-color image was successfully displayed for the first time without attaching any signal or power cables to the panel. The receiving circuitry and capacitive-coupling electrodes were integrated on the LCD panel using a low-temperature polysilicon (LTPS) fabrication process. In the proposed digital coding method, the receiving circuit converts derivative waveform signals via the capacitive coupling to conventional logic-level signals. The maximum data rate of 2.4-Mbps × 3ch (RGB) was achieved. In addition, LTPS low-capacitance diode bridge and regulator enabled us to obtain stable DC power of 2.4 mW on the panel from the AC-power signal. This study is the first step towards integrating the wireless-communication function on the display panel to achieve a high-value-added flat-panel display (FPD).