Wataru Tsujita

Bio: Wataru Tsujita is an academic researcher from Mitsubishi Electric. The author has contributed to research in topics: Antenna (radio) & Terahertz radiation. The author has an hindex of 6, co-authored 54 publications receiving 178 citations. Previous affiliations of Wataru Tsujita include Advanced Technology Center.

Parameter Estimation of Hybrid Sinusoidal FM-Polynomial Phase Signal

Abstract: This paper considers parameter estimation of a hybrid sinusoidal frequency modulated (FM) and polynomial phase signal (PPS) from a finite number of samples. We first show limitations of an existing method, the high-order ambiguity function (HAF), and then propose a new method by adopting the high-order phase function which was originally designed for the pure PPS. The proposed method estimates parameters of interest from peak locations in the time-frequency rate domain, which are less perturbed by the noise than peak values used by the HAF-based method. Numerical evaluation shows the proposed method can handle the hybrid FM-PPS signal with low sinusoidal frequency and improve estimation accuracy in terms of mean squared error for several orders of magnitude.

Metamaterial absorber for THz polarimetric sensing

Abstract: THz encoders have distinct advantages for position sensing compared with other types of encoders, such as those based on optical and inductive sensors. A polarization-dependent metamaterial absorber reflects one polarization while absorbs the other, which makes it an ideal building block for the barcode of a THz encoder system. In this paper, we present the design, fabrication, and experiments of a THz polarization-dependent metamaterial absorber, and its application to a polarimetric sensing system.

Travel distance measurement device

Abstract: A travel distance measurement device includes a transmitting antenna that is disposed in a vehicle and emits a transmission signal, as a radio wave, toward a ground surface, a receiving antenna that is disposed in the vicinity of the transmitting antenna, and receives a radio wave reflected from the ground surface and acquires a reflection signal, and a distance calculator (an IQ demodulator and a phase conversion integrator) that calculates the travel distance of the vehicle on the basis of the phase of the acquired reflection signal.

Vehicle inclination detection device

Abstract: In this vehicle inclination detection device (1), a reception unit (200) is provided with a switch (601) that alternatingly switches an input signal from a first reception antenna (201) and a second reception antenna (202) and outputs the input signal to a quadrature detector (701). Using the same line, the quadrature detector (701) performs quadrature detection on an oscillation signal from an oscillator (101) and the two received signals from the switch (601).

Train-position detection device

Abstract: Based on a ratio between Doppler frequencies calculated from a plurality of reception signals outputted by a receiver, a position detector calculates a relative position of a plurality of antennas in a mobile wireless apparatus to a stationary wireless apparatus. A train position detector calculates a position of a train from the calculated relative position, a placement position of the stationary wireless apparatus and placement positions in the train of the plurality of antennas.

The Global Positioning System

Abstract: This research study explores the Global Positioning System (GPS), its history, and the process of discovery needed to create the most accurate GPS possible, as well as the contemporary applications of GPS technology. Starting with the first satellite in space, GPS has been a work in progress. Originally pursued by the military for improvements to military tactics, GPS has become integrated into the everyday lives of millions of people around the world. How GPS determines location is a dichotomy, with simplistic theory and complex application. Many factors go into GPS to provide a consistent, accurate location. The orbital planes the satellites are placed in provide 24/7 coverage globally, the L-band frequencies used were chosen specifically for the characteristics they possess, and the multiple atomic clocks installed on each satellite provide incredible accuracy down to the nanoseconds, which is quintessential in GPS accuracy. The applications in GPS are far reaching and more applications are continually being discovered. With as far as GPS technology has progressed, there are still several factors that degrade the signal and are a challenge to overcome. Many of these challenges can be corrected efficiently, however, others, such as scintillation and total electron content variability in the ionosphere, create major hurdles to overcome. Luckily, there are many programs that aid in the correction process of these hurdles. The History of GPS According to R. Saunders’ article ​A Short History of GPS Development,​ The Global Positioning System (GPS) has a long history of trial and error and refinement and improvement. It’s purpose has shifted from being a military strategic asset to commonplace among the general public with its use in traveling, farming, and even banking. The beginning of GPS, introduced with a simple idea, can be traced back to the Soviet Union in the late 1950’s. In 1957, the Soviet Union made history with successfully launching the first satellite in space. To track the satellite Sputnik, Physicists and Scientists at John Hopkins University’s Applied Physics Laboratory listened to the beeps Sputnik’s signals produced. They noticed that the beeps had a Doppler Effect or Doppler Shift as the satellite passed by. Much like the sound a siren makes as a fire truck approaches, then as it passes, the sound of the siren seems different. The change in timing between the beeps let the scientist know Sputnik’s location. This led to the idea of reversing that process, to give a location on the Earth. Using radio frequencies to determine location in a two dimensional plane had been around since WWII, but using satellites would push this technology into the three dimensional realm. The United States Navy, Army, and Air Force all began developing their own GPS satellites in the 1960’s, but this was no small task. In the early 1960’s, the Navy launched its first Transit Satellite. The failure of this satellite, however, was due to

A new technique for instantaneous frequency rate estimation

Abstract: This letter introduces a two-dimensional bilinear mapping operator referred to as the cubic phase (CP) function. For first-, second-, or third-order polynomial phase signals, the energy of the CP function is concentrated along the frequency rate law of the signal. The function, thus, has an interpretation as a time-frequency rate representation. The peaks of the CP function yield unbiased estimates of the instantaneous (angular) frequency rate (IFR) and, hence, can be used as the basis for an IFR estimation algorithm. The letter defines an IFR estimation algorithm and theoretically analyzes it. The estimation is seen to be asymptotically optimal at the center of the data record for high signal-to-noise ratios. Simulations are provided to verify the theoretical claims.

Liquid crystal display device and manufacturing method therefor

Abstract: To provide a liquid crystal display device of high image quality, and a manufacturing method therefor. A polymerizable compound in a liquid crystal composition is polymerized in a state that liquid crystal molecules present in a gap between a pixel electrode and at least either one of signal electrodes and scanning electrodes are tilted in a direction from the at least either one of the signal electrodes and the scanning electrodes toward the pixel electrode. Preferably, the amount of the polymerizable compound remaining in the liquid crystal phase after the polymerization is not more than 0.05 parts by weight per 100 parts by weight of the liquid crystal. In a seal section surrounding the liquid crystal layer, a second seal wall is preferably provided at a position opposite to the liquid crystal injection inlet in the non-display section.

On refining polynomial phase signal parameter estimates

Abstract: Newton algorithms are commonly used in the final “refinement” stage of parameter estimation for sinusoids and higher order phase polynomial signals Such parameter estimation scenarios arise commonly in radar applications where the radial target velocity (which is possibly time-varying) must be estimated The author and coworkers have previously proposed an elegant and efficient alternative to a Newton gradient search type algorithm based on filtering and phase unwrapping A statistical and computational analysis of this filtering/phase unwrapping method is presented here The analysis shows the algorithm to be computationally efficient and much less sensitive to the accuracy of the initial guesses for the parameters than a Newton algorithm A first-order statistical analysis of the filtering/phase unwrapping algorithm is performed, and guidelines are derived for the required accuracy of the initial estimates Simulations are presented to confirm the analysis