Direct Phase Modulation Research Articles

Auditory Cortex Tracks Both Auditory and Visual Stimulus Dynamics Using Low-Frequency Neuronal Phase Modulation

Author SummaryWhen faced with ecologically relevant stimuli in natural scenes, our brains need to coordinate information from multiple sensory systems in order to create accurate internal representations of the outside world. Unfortunately, we currently have little information about the neuronal mechanisms for this cross-modal processing during online sensory perception under natural conditions. Neurophysiological and human imaging studies are increasingly exploring the response properties elicited by natural scenes. In this study, we recorded magnetoencephalography (MEG) data from participants viewing audiovisual movie clips. We developed a phase coherence analysis technique that captures—in single trials of watching a movie—how the phase of cortical responses is tightly coupled to key aspects of stimulus dynamics. Remarkably, auditory cortex not only tracks auditory stimulus dynamics but also reflects dynamic aspects of the visual signal. Similarly, visual cortex mainly follows the visual properties of a stimulus, but also shows sensitivity to the auditory aspects of a scene. The critical finding is that cross-modal phase modulation appears to lie at the basis of this integrative processing. Continuous cross-modal phase modulation may permit the internal construction of behaviorally relevant stimuli. Our work therefore contributes to the understanding of how multi-sensory information is analyzed and represented in the human brain.

24-Bit 5.0 GHz Direct Digital Synthesizer RFIC With Direct Digital Modulations in 0.13 $\mu$m SiGe BiCMOS Technology

This paper presents a 24-bit 5.0 GHz ultrahigh-speed direct digital synthesizer (DDS) with direct digital modulation capabilities used in a pulse compression radar. This design represents the first DDS RFIC in over-GHz output frequency range with direct digital modulation capabilities. It adopts a ROM-less architecture and has the capabilities for direct digital frequency and phase modulation with 24 bit and 12 bit resolution, respectively. The DDS includes a 24-bit ripple carry adder (RCA) accumulator for phase accumulation, a 12-bit RCA for phase modulation and a 10-bit segmented sine-weighted digital-to-analog converter (DAC) for phase-to-amplitude conversion (PAC) as well as digital-to-analog conversion. The DDS core occupies 3.0 × 2.5 mm2 and consumes 4.7 W of power with a single 3.3 V power supply. This 24-bit DDS has more than 20,000 transistors and achieves a maximum clock frequency of 5.0 GHz. The measured worst case SFDR is 45 dBc under a 5.0 GHz clock frequency and within a 50 MHz bandwidth. At 1.246258914 GHz output frequency, the 50 MHz narrowband SFDR is measured as 82 dBc. The best Nyquist band SFDR is 38 dBc with a 469.360351 MHz output using a 5.0 GHz clock frequency. This DDS was developed in a 0.13 μm SiGe BiCMOS technology with fT/fMAX = 200/250 GHz and tested in a CLCC-68 package.

Synchronization and Coherent Combining of Two Pulsed Fiber Ring Lasers Based on Direct Phase Modulation

We demonstrate a scalable architecture for coherent combining of pulsed fiber ring lasers based on mutual injection and direct phase modulation. By direct phase modulation in the common arm of two ring lasers, synchronous pulsed lasers can be generated and coherent combining of the two synchronous lasers is obtained. Two pulsed fiber ring lasers are coherently combined with 0.55 μJ pulse energy and 10 μs pulse duration at a repetition rate of 27.5 kHz. Experimental results show that the two fiber ring lasers are phase locked with an invariable phase difference of π and have good temporal synchronization and spatial coherence. The combining efficiency of the two pulsed fiber laser reaches 90% and the fringe contrast is larger than 40%. Neither active phase control nor polarization control is used in our experiment and this method can be extended to combine more beams and higher repetition rate scaling up to higher power.

两路脉冲光纤激光的同步与相干合成

We demonstrate a scalable architecture for coherent combining of pulsed fiber lasers. A new method for generating synchronous pulsed fiber lasers by direct phase modulation is proposed and investigated. It is shown that phase modulated mutually coupled laser array can be a steady synchronous pulsed fiber laser source. The synchronous pulsed fiber lasers are coherently combined with an invariable phase difference of \pa in adjacent lasers. Neither active phase control nor polarization control is taken in our experiment.

Coherent optical vector modulation for fiber radio using electrooptic microchip lasers

Future communication systems will require high data rates and flexible modulation. Direct optical phase modulation of two microchip lasers by information-bearing signals allows for high-rate delivery via fiber to a basestation. At the basestation, the coherent optical signals are combined with a reference in a photodetector to produce a microwave/millimeter-wave carrier with arbitrary M-ary quadrature amplitude modulation, which can then be transmitted over a wireless channel. Rapid tuning of the microwave/millimeter-wave carrier, the modulation scheme, and the data rate is achievable through this method with no fixed oscillators at the basestation, thus providing for flexible architectures. Results show a high-quality carrier and, for 4- and 16-QAM, with data rates to 200 Mb/s. Extensions to higher data rates are discussed.

Investigation of Ba x Sr 1 - x TiO 3 Film-Based Transmission Line for Direct Phase Modulation of Microwave Carrier

Investigation of Ba x Sr 1 - x TiO 3 Film-Based Transmission Line for Direct Phase Modulation of Microwave Carrier

Steered coupled-cavity-backed Hertzian dipole array

This paper presents the operating characteristics of a coupled-cavity-backed Hertzian dipole resonator array excited with mutually injection-locked voltage-controlled oscillators (VCOs). It is demonstrated that microwave spatial power-combined inter-injection locking through mutual coupling of individual antenna oscillators can be obtained with an auxiliary coupling network formed by a cavity iris configuration introduced within a reduced-height waveguide arrangement. As a result, strong mutual-coupling control can be realized and exploited in conjunction with self-injection-locked oscillators in order to achieve direct phase modulation of the locked oscillators. Beam scanning up to 10/spl deg/ off the broadside through locked VCO phase modification has been demonstrated in a three-element array occupying a space of only 0.6 /spl lambda//sub 0//spl times/0.027 /spl lambda//sub o/ at 998 MHz.

Highly sensitive 565 Mb/s DPSK heterodyne transmission experiment using direct current modulation of a DFB laser transmitter

A comparison between external phase modulation and phase modulation obtained through direct current modulation of a multiquantum-well distributed feedback (DFB) transmitter is reported for a sensitive 565 Mb/s differential-phase-shift-keying (DPSK) heterodyne transmission experiment. A limited sensitivity penalty for direct phase modulation is expected from the driving current pulse shape, the transmitter FM response and the receiver characteristics. The experimentally observed 0.5 dB penalty is in agreement with theory and highlights the potential of direct DPSK modulation as compared to both standard DPSK and continuous-phase frequency shift keying (CPFSK) schemes. >

Characteristics of semiconductor laser optical amplifier as phase modulator

Direct phase modulation with the use of an optical amplifier has been investigated. We report on measurements of the phase and amplitude modulation index over a frequency range of 1 GHz and as a function of the bias current

Fibre transmission properties of optical pulses produced through direct phase modulation of DFB laser diode

A scheme for gigabit range modulation without wavelength chirping is proposed. This technique uses the direct phase modulation property of a laser diode, and an optical interferometer with a time delay path. In a 4Gb/s experiment using a distributed feedback (DFB) laser diode with 1.54μm wavelength, the pulses passed through a 102 km nondispersionshifted fibre without being broadened.