3887 results about "Signal modulation" patented technology

The method and apparatus for information conveyance and distribution to bidirectionally focus or guide a wide spectrum of electromagnetic waves propagated over a possible variety of propagation media, including free space or wireless, surface wave, and cable or wired transmission lines. The apparatus communicates with information devices immediately adjacent to these media wherein the devices, which are not themselves part of the apparatus, may have electromagnetic access to one another. The apparatus maintains adequate signal to noise ratio and low distortion for a possible variety of different signal modulation and encoding types which it can support while permitting transparent, simultaneous communications among a variety of devices. Spread spectrum techniques may be used within the apparatus to mitigate propagation medium distortions and impairments as well as to control access and provide a means for securing information within the corridor and for obtaining revenue. Adapters may be employed to provide either full or half duplex access to the information devices which utilize it.

A method monitors operation of a disk drive. The method includes providing a disk drive which includes a rotating disk and a head having a read transducer in proximity to a surface of the disk and an adjustment mechanism which controllably adjusts an average relative spacing between the read transducer and the surface. The method further includes generating a read-back signal by reading from the surface using the read transducer. The read-back signal includes a high frequency carrier signal having an envelope that is modulated by a lower frequency signal. The method further includes varying the average relative spacing between the read transducer and the surface using the adjustment mechanism. The method further includes analyzing the envelope in the frequency domain and detecting an emergence of at least one frequency component of the envelope within an air bearing resonance range of frequencies.

A transceiver employing a steerable phased-array antenna includes a modem architecture in which signals from each antenna element in the array are independently processed down to the individual baseband channel level, and digital beamforming is performed at baseband. The data rate reduction from IF to baseband permits parallel signal data from multiple antenna elements to be time multiplexed and serially processed at acceptable data rates at baseband with minimal modem hardware requirements. Both for transmit signal modulation and received signal demodulation, the computation of carrier tracking, automatic gain control (AGC)/power-control, and beamforming are shared by the same processing circuitry for all channels when performed at baseband. The resulting baseband circuitry is only incrementally larger than that required for carrier tracking and AGC alone, yet accomplishes independent beamforming for each antenna element on each user channel.

A multiple access, spread-spectrum communication system processes a plurality of information signals received by a radio carrier station over telecommunication lines for simultaneous transmission over a radio frequency channel as a code-division-multiplexed signal to a group of subscriber units. The radio carrier station receives a call request signal that corresponds to a telecommunication line information signal, and a user identification signal that identifies a user to receive the call. The radio carrier station includes a plurality of CDMA modems, one of which provides a global pilot code signal. The modems provide message code signals synchronized to the global pilot signal. Each modem combines an information signal with a message code signal to provide a code division multiplexed signal. The RCS includes a system channel controller is coupled to receive a remote call. A radio frequency transmitter is connected to all of the modems to combine the code division multiplexed processed signals with the global pilot code signal to generate a code division multiplexed signal. The transmitter also modulates a carrier signal with the code division multiplexed signal and transmits the modulated carrier signal through a radio frequency communication channel to the subscriber units. Each subscriber unit includes a CDMA modem which is also synchronized to the global pilot signal. The CDMA modem despreads the code division multiplexed signal and provides a despread information signal to the user. The system includes a closed loop power control system for maintaining a minimum system transmit power level for the radio carrier station and the subscriber units, and system capacity management for maintaining a maximum number of active subscriber units for improved system performance.

Systems, apparatus, and methods for new generations of wireless systems, including multiple standard, interoperable Third-Generation (3G) and Second-Generation (2G), Spread Spectrum CDMA, WCDMA, GSM, Enhanced GSM systems and CSMA, TDMA and OFDM. Bit Rate Agile (BRA), Modulation and Code Selectable processing techniques of Gaussian Minimum Shift Keying (GMSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and of Mis-Matched demodulator filters in which the demodulator filter set is mismatched to the filter set of the signal modulator.

A chaotic communication system employs transmitting and receiving chaotic oscillating circuits. One improvement to first-generation systems is the ability to modulate a nonreactive element in the transmitting circuit, thus increasing modulation bandwidth. Other features include insertion of a gain control amplifier in a chaotic receiver; signal filtering in chaotic transmitters and receivers; use of chaotic modulation techniques for cellular telephony applications; dual-transmitter and receiver systems; a dual receiver synchronization detector; interfaces to communication systems; analog chaotic signal modulation; use of multiple chaotic transmitters and receivers; digital algorithm improvement using a cube-law nonlinear component; a Gb-only receiver; a Gb-only transmitter; and positive slope transmitter and receiver systems.

A low-noise laser diode module comprises a laser diode for emitting light with a wavelength in the range from UV to IR, a drive circuit for injecting electrical current into said diode, and an automatic power control circuit for monitoring and adjusting laser output power using front-facet photodiode external to the laser assembly and a feedback loop. Said drive circuit produces injection current modulated by an RF signal with variable degrees, depending on the wavelength to be stabilized, the desired spectral bandwidths of the laser output, and/or other applications. Said RF signal can be a sine wave, a distorted sine wave, a rectified sine wave, a non-sine wave, a series of narrow pulses, or repetitive shunt. The present invention encompasses a method for producing stable, broadband, and low-coherent laser. The present invention also encompasses a method for producing stable narrowband or single longitudinal mode laser. The present invention further encompasses a compact light source applicable to DPSS lasers, fiber lasers, optical parametric oscillators, low-speckle laser display systems, and seeders, with or without nonlinear frequency conversion processes.

The invention relates to a switching amplifier comprising at least one pulse modulator arranged for modulating at least one input utility signal into at least one pulse modulated signal and at least one switching power stage arranged to establish at least one amplified utility signal on the basis of said at least one pulse modulated signal and a power signal, said power signal being delivered by a tracking power supply at least partly controlled by said at least one input utility signal, characterized in that said switching amplifier is arranged to process said at least one input utility signal according to a correction signal established by a correction signal estimator on the basis of a supply information signal derived from said tracking power supply.

According to the present invention an advantageous switching amplifier enabling use of a tracking power supply is provided. Thereby the many benefits of switching amplifiers can now be obtained together with the benefits of utilizing a tracking power supply. Among many things, this reduces power consumption, reduces EMI noise and enables using more of the dynamic range available for the utility signal during the pulse modulation. The last advantage further renders noise introduced by the power supply and the switching output stage less significant, as the signal-to-noise ratio in the power stage is greatly improved due to the utilization of the full dynamic range enabled by using a tracking power supply.

The invention discloses a modulation mode identification system and method based on a convolutional neural network, which solve the problems of complex feature extraction steps and low identificationrate under a low signal-to-noise ratio in the prior art. The simple feature in the identification system is constructed as a simple feature using a co-directional component and a quadrature componentof a baseband signal as signals, and the simple feature is sent to a convolutional neural network module for identification. The identification method comprises the steps of: modulating a transmittedsignal and performing pulse shaping; performing up-conversion on the transmitted signal and then transmitting the transmitted signal through an additive white Gaussian noise channel; performing pre-processing first by a receiving end to obtain the co-directional component r(t) of the analyzed signal; constructing the simple feature, i.e., constructing the co-directional component r(t) and the quadrature component of the analyzed signal into a two-dimensional matrix; performing feature learning and classification by the convolutional neural network; and sending a modulation method to a demodulation end to obtain a demodulated signal. The method is low in feature design complexity, avoids explicit feature extraction, has high classification correctness, and can be applied to communication systems having high recognition performance requirements.

Sparse signal modulation schemes encode a data channel on a host image in a manner that is robust, flexible to achieve perceptual quality constraints, and provides improved data capacity. The host image is printed by any of a variety of means to apply the image, with sparse signal, to an object. After image capture of the object, a decoder processes the captured image to detect and extract data modulated into the sparse signal. The sparse signal may incorporate implicit or explicit synchronization components, which are either formed from the data signal or are complementary to it.

An active antenna array comprises a plurality of transmission paths, a predistortion modulation signal generator, and a predistortion modulation signal distribution structure. At least two of the plurality of transmission paths comprise a predistortion modulator for modulating a transmission path signal with a predistortion modulation signal generated by the predistortion modulation signal generator and distributed by predistortion modulation signal distribution structure to the at least two of the plurality of transmission paths. A method for predistorting at least two of a plurality of transmission path signals in an active antenna array and computer program products for manufacture and method execution are also claimed.

A photonic integrated circuit (PIC) chip comprising an array of modulated sources, each providing a modulated signal output at a channel wavelength different from the channel wavelength of other modulated sources and a wavelength selective combiner having an input optically coupled to received all the signal outputs from the modulated sources and provide a combined output signal on an output waveguide from the chip. The modulated sources, combiner and output waveguide are all integrated on the same chip.

The present invention is directed to realize a stable and highly-efficient quantum communication without being influenced by the jitter of the heralding signal. In regard to the quantum encryption transmitting apparatus 200, the pulse-driven heralded single-photon source 201 generates a photon pair, outputs one photon of the photon pair, and outputs the other photon of the photon pair as a heralding signal. The timing adjuster 202 synchronizes the heralding signal with a clock signal for pulse driving the pulse-driven heralded single-photon source 201, and outputs as a trigger signal. The quantum communication modulating unit 203 implements the signal modulation to a quantum signal, in timing with the trigger signal, and transmits the quantum signal to the quantum encryption receiving apparatus 300 via the quantum communication path 101. The heralding signal transmitting unit 205 transmits the heralding signal to the quantum encryption receiving apparatus 300 via the heralding signal communication path 102. The clock signal transmitting unit 206 transmits the clock signal to the quantum encryption receiving apparatus 300 via the clock communication path 103.

A class AD audio amplifier system (10) with DC output detection logic (26) is disclosed. The amplifier system (10) includes multiple audio channels (20), each of which includes a pulse-width-modulator (PWM) (24). The DC detection logic (26) includes a sigma-delta modulator (60) and a digital low-pass filter (62) that monitors the PWM output signals from the PWM modulators (24). The sigma-delta modulator (60) operates at a first clock frequency, while the low-pass filter (62) operates at a much lower clock frequency, so that AC audio components, PWM harmonics, and sigma-delta quantization error is suppressed from the DC detection. The modulated filtered signal is compared against a threshold level (THRSH) to determine whether the amplitude of a DC component at the PWM output is sufficiently high to constitute a fault. If so, a fault detection signal (DC_DET) is issued, and the PWM modulators (24) are disabled to prevent unsafe conditions in the system (10).

An inspection method which simplifies an inspection step by eliminating the need to set probes on wiring or probe terminals, and an inspection device for performing the inspection step. A voltage is applied to each of inspected circuits or circuit elements to operate the same. Signal processing is performed on an output from each inspected circuit or circuit element during operation to form a signal (operation information signal) including information on the operating condition of the circuit or the circuit element. The operation information signal is amplified and the amplitude of an alternating current voltage separately input is modulated with the amplified operation information signal. The voltage of the modulated alternating current is read in a non-contact manner to determine whether the corresponding circuit or circuit element is non-defective or defective.