Minimum Phase Delay Research Articles

Method for Increasing the Accuracy of a Gyroscope with a Spherical Ball Bearing Suspension

The article is devoted to the development of a method for improving the accuracy of a gyro with a spherical ball bearing suspension operating in the mode of a deflection angle meter of the base on which it is installed. When operating a gyroscope as part of an information-measuring and control system, such an operational characteristic as the accuracy of readings, depending on the noise component of the gyroscope output signal, is of decisive importance. The purpose of the article is to solve the problem of reducing the noise component of the output signal while maintaining a wide bandwidth of the device and a minimum phase delay of the output signal in relation to the measured value. The paper provides an overview of the existing device construction schemes. A mathematical description of the functioning of the gyroscope is presented, on the basis of which the transfer functions for the moment (disturbing, controlling or total) along the direct and cross channels are obtained. Transfer functions are also obtained, which are the ratio of the output signal to the measured value through direct and cross channels. It is noted that the predominant frequencies of the noise component of the output signal correspond to the rotational frequency of the gyroscope rotor, the rotation frequency of the gyroscope rotor and the multiple rotation frequencies of the gyroscope rotor. The structure of the system is proposed in which the signal from the gyroscope angle sensor with a spherical ball bearing suspension is summed up with the output signal of an additional angular velocity sensor according to the corresponding coordinate and then the total signal is smoothed using an aperiodic link of the first order. The results are obtained for determining the parameters of the channel of the angular velocity meter, at which it is possible to compensate for the bandwidth limitations in the channel of the angle measurement due to the time constant of the smoothing filter and at the same time ensure effective suppression of the noise component of the output signal. The proposed construction scheme of the meter provides attenuation of noise components in the output signal of a gyroscope with a spherical ball bearing suspension at a rotation frequency of the gyroscope rotor 250 Hz by 156 times, at a frequency of nutation oscillations of the gyroscope rotor 404 Hz by 256 times, at a frequency of 500 Hz by 316 times, at a frequency of 750 Hz by 474 times, at a frequency of 1000 Hz by 630 times, at a frequency of 1250 Hz by 785 times while maintaining a wide bandwidth of 285 Hz when measuring an angle with a phase lag of the output signal from the measured one close to zero degrees in the bandwidth.

Analog holographic wavefront sensor for defocus and spherical aberration measurement recorded in a photopolymer.

An analog holographic wavefront sensor (AHWFS), for measurement of low and high order (defocus and spherical aberration) aberration modes has been developed as volume phase holograms in a photopolymer recording medium. This is the first time that high order aberrations such as spherical aberration can be sensed using a volume hologram in a photosensitive medium. Both defocus and spherical aberration were recorded in a multi-mode version of this AHWFS. Refractive elements were used to generate a maximum and minimum phase delay of each aberration which were multiplexed as a set of volume phase holograms in an acrylamide based-photopolymer layer. The single-mode sensors showed a high degree of accuracy in determining various magnitudes of defocus and spherical aberration generated refractively. The multi-mode sensor also exhibited promising measurement characteristics and similar trends to the single-mode sensors were observed. The method of quantifying defocus was improved upon and a brief study into material shrinkage and sensor linearity is presented.

Improved Doherty Amplifier Design with Minimum Phase Delay in Output Matching Network for Wideband Application

This letter presents an improved Doherty power amplifier (DPA) for high-efficiency and wideband operations. To achieve the impedance transformations both in the low power region and at saturation, a design approach is proposed to determine the desired minimum phase delays of the carrier and peaking output matching networks, which can simplify the load modulation network of the DPA and extend the bandwidth. For verification, a 1.6-2.2 GHz asymmetric DPA was designed and measured. The designed DPA can deliver an efficiency of 51%-55% at 10 dB back-off power over the whole band. For a 20 MHz LTE signal, an average efficiency of higher than 50% can be achieved at 36 dBm average output power with the linearity of -48 dBc after linearization across the band.

Tracking, Model Matching, Disturbance Decoupling for a Class of Nonlinear Delay Systems

The problem of asymptotic output tracking for nonlinear delay systems is considered in this paper, and a solution is proposed for nonlinear minimum phase delay systems. A theorem is proved which assures the boundedness of the state variables for a class of nonlinear delay systems, when the reference output and its derivatives up to a given order are bounded. Then, the problem of disturbance decoupling is considered for nonlinear delay systems, both in the cases of known and unknown disturbances. A solution is proposed for minimum phase delay systems, under suitable assumptions on the delay relative degrees. Conditions are given that assure boundedness of the state variables. Simulation results on nonlinear delay systems unstable in open loop are also reported showing the effectiveness of the proposed methods.