Yoshitaka Tsunekawa

Interference reduction between SDD linear array antennas using end-fire arrangement

This paper proposes a self-interference reduction method exploiting antenna arrangement and beamforming for space division duplex (SDD) relay station. When transmitting (Tx) and receiving (Rx) linear array antennas are placed in end-fire arrangement, spatial correlation between Tx and Rx increases. This causes rank degeneracy of the channel matrix between Tx and Rx. With this channel, almost all the self-interference inside SDD relay station can be reduced by forming beam to the nearly-zero space at Tx. Simulation results show that there is the optimum element spacing of linear array, and that the proposed method greatly improves channel capacity of SDD relay system, which is higher than that of the time division duplex (TDD) system.

Pressure/photo sensor utilizing polymer magnetic composite

A polymer magnetic composite (PMC) is a flexible thick film and is composed of a ferrite powder with variable possible Curie temperatures, polymer and solvent. It is found that high and low Curie temperature PMCs can be used for pressure and photosensors, respectively. The set up combined with the PMC and a pressure element acts as a pressure sensor. The device, painted with a radiant flux absorbent on the surface of the PMC, responds to the visible rays. The pressure and light signals are read out by a Hall element in noncontact with the PMC. >

Fast FDTD analysis of MIMO channel using spread spectrum technique

This paper proposes fast FDTD (Finite-Difference Time-Domain) analysis method that uses simultaneous excitation for multi-antenna systems. In this method, spread spectrum technique is employed for maintaining the orthogonality among the excited signals. Excitation signals are generated by multiplying the spreading codes that are different to each other. By assigning the different spreading codes to all transmitting antennas, the channels from multiple transmitting antennas to receiving antenna(s) can be calculated simultaneously. The simulation of a 2×2 multi-antenna system shows that the results of the proposed method agree well with those of the conventional method even though its computation speed is two times higher than that of the conventional method.

Use of load modulation for interference control between primary and secondary systems

Controlling interference from the secondary system to the receiver of the primary system is important issues when the secondary system uses the same frequency band in the area of television broadcast system. The reason includes that the secondary system cannot know the interference channel to the primary receiver, which does not have a transmitter. In this paper, we propose the interference control method between primary receiver and secondary system, where a load modulation scheme is introduced to the primary receiver. In this method, the signal from the transmitter station is scattered by switching load impedance at the primary receiver. Also, the secondary system estimates the reflected wave from receiver and estimates the interference suppression weights. Based on the simulation, it is shown that the proposed method is effective in controlling interference between primary receiver and secondary system.

Multi-antenna decoupling technique exploiting MISO channel on neighboring antennas

In this paper, a novel decoupling technique suitable for a compact array antenna is proposed. In this technique, an orthogonal excitation weight in MISO channel between 2 × 1 antennas are utilized. The simulation results demonstrate the excellent isolation and matching characteristics can be obtained when the proposed decoupling technique is applied to a compact three inverted-F array. Also, the proposed technique offers high radiation efficiency over the broad bandwidth.

Accuracy of MIMO Channel Capacity Equation Based Only on -Parameters of MIMO Antenna

Since the evaluation of multiple-input multiple-output (MIMO) antennas requires full information of its complex radiation patterns as well as propagation channels, its design procedures and analyses are cumbersome and complicated in general. In this letter, the accuracy of a closed-form capacity formula for mean MIMO channel capacity is investigated, where the S-parameter of the antenna is needed but the antenna must be lossless. Numerical analyses show that this formula gives mean channel capacity with a good accuracy when the signal-to-noise ratio is sufficiently high.

Fast estimation algorithm for living body radar

The authors have proposed a direction estimation method of the living-body using array antenna in multi-path environment. However, this method has a problem that takes time as several tens of seconds. In this paper, we present a fast algorithm for estimating living-body direction. The experiment showed that the proposed method works well in estimating living-body direction with high accuracy in multi-path environment even when the observation time is less than conventional method.

Evaluating impact of tag element spacing on bit-error-rate performance using passive MIMO testbed

In this study, we experimentally assessed the impact of tag element spacing on Bit-Error-Rate (BER) performance of passive Multiple-Input Multiple-Output (MIMO), which uses multiple antennas at both Radio Frequency Identification (RFID) tag and its reader to improve data-rate of the backscattering load modulation. Since a small RFID tag needs miniaturized multiple antennas, the antenna element spacing must be narrow. However, no studies have evaluated the effect of the element spacing in passive MIMO. This paper experimentally reveals the relationship between the BER and the element spacing using own-developed passive MIMO testbed. From the experimental result, it is shown that the passive MIMO with 0.2-wavelength spacing yields feasible BER (<; 10-2) at 1 m communication distance even with realistic noise power (> -90 dBm).

Performance of miniaturized 6-port MIMO antenna using orthogonal polarization

In this paper, miniaturized 6-element MIMO (Multiple-Input Multiple-Output) antenna using T-shaped inverted-F antenna and reactance-loaded notch antenna is experimentally evaluated. Combination of T-shaped inverted-F antenna and reactively loaded notch antenna offers both miniaturization and orthogonalization of antenna elements. The experimental results showed good matching and low mutual coupling characteristics. Furthermore, MIMO channel capacity was evaluated and it is found that the proposed antenna significantly outperforms monopole-array in capacity.

Experimental evaluation of matching method based on image impedances for near field MIMO

In this paper, a novel matching method for near field MIMO is proposed. A concept of image impedance matching is extended to 2×2 MIMO. A proposed matching network was fabricated and tested. The measurement results indicated the proposed matching network offers a high channel capacity since it significantly improves SNR in near field MIMO scheme.