Digital signal

About: Digital signal is a research topic. Over the lifetime, 44213 publications have been published within this topic receiving 345279 citations.

Distributed antenna system interface for processing digital signals in a standardized format

Abstract: An interface is provided for processing digital signals in a standardized format in a distributed antenna system. One example includes a unit disposed in a distributed antenna system. The unit includes an interface section and an output section. The interface section is configured for outputting a first complex digital signal and a second complex digital signal. The first complex digital signal is generated from a digital signal in a standardized format received from a digital base station. The output section is configured for combining the first complex digital signal and the second complex digital signal into a combined digital signal. The output section is also configured for outputting the combined digital signal. The combined digital signal comprises information to be wirelessly transmitted to a wireless user device.

Data storage and retrieval structure for a message storage system

Abstract: A message storage system (104) cooperates with a plurality of telephone switching offices (102, 122) to provide a variety of voice storage services to subscribing customers served by the switching offices. Control signals and voice messages are delivered to the message storage system in analog form and converted to digital signals. A processor circuit (111) interprets the control signals and sends work lists to a plurality of microprocessor controlled message controllers (113a through 113n) which in turn each control a plurality of disc transports (114a through 114n), a time multiplex switch (115), and a larger plurality of buffer circuits (116) wherein the messages in digital signal form are speed buffered for storage in the disc transports. The message controllers control the flow of digital data words between the buffer circuits and the disc transports via the time multiplex switch to provide highly efficient mass storage and retrieval of messages.

Infrared intrusion sensor

Abstract: An infrared intrusion sensor comprising an array of infrared detectors (17), infrared collection optics which may include a Cassegrain-style telescope (11, 12), a focal plane scanning device (11, 12, 13), including dither means adapted to repetitively scan the infrared radiation across the detector array, signal process means and local or remote display means. The sensor may incorporate heterodyne detection techniques with a local oscillator signal derived from the scanning frequency of the focal plane scanning device. The sensor has a low false alarm rate and enhanced detection range. Also disclosed is a method of processing signals involving A/D conversion, integration of the digital signals to produce a background signal, phase sensitive detection of the digital signal producing a target signal and comparison of the background and target signals producing a difference signal. This difference signal is then integrated to produce a background noise signal and processed to become a threshold signal which is finally compared to the difference signal to produce an alarm signal.

Nickel-cadmium battery monitor

Abstract: The nickel-cadmium battery monitor is provided with sensors for measuring the battery temperature, the battery voltage and the magnitude of the current being charged to the battery, each of the sensors generating a sensor signal voltage that varies directly with the magnitude of the parameter being measured. The sensor signal voltages from the temperature sensor and the voltage sensor are conditioned and then converted to an analog signal voltage increment the magnitude of which corresponds approximately to the actual magnitude of the battery temperature and battery voltage as measured. The analog signal voltage increments thus obtained cause an analog visual display means to indicate visually the approximate magnitude of the battery temperature and battery voltage as measured. The conditioned analog signal voltages from the temperature sensor and the voltage sensor are also converted to a multibit digital signal which causes a digital visual display means to display in numeric form the actual magnitude of the battery temperature or battery voltage as measured. Charge rate sampling means continuously measures the magnitude of successive samples of the charge current and transmits an alarm signal to a flash alarm means when the rate of increase in the charge current exceeds a predetermined value. The flash alarm means transmits flash alarm signal to the digital visual display means when the temperature of the battery exceeds a predetermined value or when the voltage of the battery falls below or exceeds a predetermined value or when the charge rate sampling means transmits an alarm signal to the flash alarm means.

An adaptive controller for the active absorption of sound

Abstract: An adaptive system is presented that allows a secondary acoustic source to become an active absorber of sound at the end of a closed duct. The system can also be generalized in order to achieve other termination impedances. The system consists of a loudspeaker, two microphones, and signal processing hardware including a digital signal microprocessor. The signals from the microphones are processed to obtain an error signal that represents the difference between the actual and the desired acoustic impedance of the termination. An absorbing termination requires, for example, that the microphone pair acts as a unidirectional probe picking up the sound reflected from the active termination only. This signal is used as the error signal that the digital controller is required to minimize. A simple analysis shows that this can be done adaptively using the ‘‘filtered‐X’’ LMS algorithm. A simple experimental setup is used to obtain an absorbing termination which is shown to work with periodic, random, and transient input signals.