Masaaki Nagahara

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Finite-impulse response (FIR) filters are often preferred to infinite-impulse response (IIR) filters because of their various advantages in respect of stability, phase characteristic, implementation, etc. This article proposes a new method to approximate an IIR filter by an FIR filter, which directly yields an optimal approximation with respect to the H/sup(More)
This paper proposes a min-max design of noise-shaping delta-sigma modulators. We first characterize the all stabilizing loop-filters for a linearized modulator model. By this characterization, we formulate the design problem of lowpass, bandpass, and multi-band modulators as minimization of the maximum magnitude of the noise transfer function (NTF) in fixed(More)
This survey provides a brief introduction to compressed sensing as well as several major algorithms to solve it and its various applications to communications systems. We firstly review linear simultaneous equations as ill-posed inverse problems, since the idea of compressed sensing could be best understood in the context of the linear equations. Then, we(More)
We study feedback control over erasure channels with packet-dropouts. To achieve robustness with respect to packet-dropouts, the controller transmits data packets containing plant input predictions, which minimize a finite horizon cost function. To reduce the data size of packets, we propose to adopt sparsity-promoting optimizations, namely, `1-`2 and(More)
Fractional delay filters are those that are designed to delay the input signals by a fractional amount of the sampling time. Since the delay is fractional, the intersample behavior of original analog signals become crucial. While the conventional design bases itself on the assumption that the incoming analog signals are fully band-limited up to the Nyquist(More)
Fractional delay filters are those that are designed to delay the input signals by a fractional amount of the sampling time. They are widely used in digital communications, speech processing, digital modeling of musical instruments, etc. Since the delay is fractional, the intersample behavior of input signals become crucial. While the conventional design(More)
We investigate a networked control architecture for LTI plant models with a scalar input. Communication from controller to actuator is over an unreliable network which introduces packet dropouts. To achieve robustness against dropouts, we adopt a packetized predictive control paradigm wherein each control packet transmitted contains tentative future plant(More)
We investigate the use of compressive sampling for networked feedback control systems. The method proposed serves to compress the control vectors which are transmitted through rate-limited channels without much deterioration of control performance. The control vectors are obtained by an &#x2113;<sup>1</sup>-&#x2113;<sup>2</sup> optimization, which can be(More)
Despite the existence of methods for a direct optimal design of sampled-data control systems, it is often desired to approximate sampled-data systems with discrete-time ones. This occurs frequently in the context of digital redesign, in which one retains intuition in the continuous-time context. This paper investigates and gives conditions under which such(More)