Signal Duty Cycle Research Articles

Synchronization Scheme for Frame Differential IR-UWB Receivers

Synchronization poses a major challenge in ultra wideband (UWB) systems due to low signal duty cycles in UWB. This study develops an effective synchronization scheme for frame-differential IR-UWB receivers to improve the synchronization speed. The proposed parallel search mechanism reduces the search region of the symbol boundaries to only a single frame duration. Moreover, only one delay element is needed in each branch, since a shared looped delay-line (SLD) is also proposed to lower the implementation complexity of the parallel search mechanism. Simulations and performance analysis show that the proposed scheme achieves a lower mean square error and a higher probability of detection than other alternatives.

Signal transduction in electrically stimulated articular chondrocytes involves translocation of extracellular calcium through voltage-gated channels

To ascertain, using specific inhibitors, the potential role of calcium-related signal transduction pathways in the mechanism of cartilage matrix protein gene induction and metalloproteinase gene suppression by capacitively coupled electric fields. Articular chondrocytes were isolated from adult bovine patellae and cultured in high density for 7 days. To study matrix protein expression, cells cultured in the absence or presence of specific calcium pathway inhibitors were exposed to a capacitively coupled electrical field (60 kHz, 20 mV/cm): for aggrecan 1h at 50% duty cycle and for type II collagen 6h at 8.3% duty cycle. To study metalloproteinase expression in the presence of interleukin 1 beta (IL-1beta), cells were cultured as above but exposed for only 30 min to a 100% duty cycle signal. At harvest, total mRNA was isolated and aggrecan, type II collagen, matrix metalloproteinase (MMP-1, -3 and -13) and aggrecanase [a disintegrin and metalloproteinase with thrombospondin repeats (ADAMTS-4 and -5)] mRNA expression were measured by quantitative real-time polymerase chain reaction (qPCR). (1) In the absence of inhibitors, appropriate electrical stimulation induces a 3-4-fold up-regulation of both aggrecan and type II collagen mRNA and a 3.7-9.6-fold down-regulation of IL-1beta-induced metalloproteinases; (2) the presence of inhibitors alone does not affect any target mRNA levels; (3) inhibitors of intracellular calcium regulation and inositol 1,4,5-triphosphate (IP(3)) formation [8-(diethylamino)octyl-3,4,5,-trimethoxybenzoate hydrochloride (TMB-8) and neomycin, respectively] have no effect on regulation of target mRNA levels by electrical stimulation; and (4) inhibitors of voltage-gated calcium channels (verapamil), calmodulin activation (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride, W-7), calcineurin activity (cyclosporin A), phospholipase C activity (bromophenacyl bromide, BPB) and prostaglandin E(2) (PGE(2)) synthesis (indomethacin) completely inhibit the effects of electrical stimulation. The results are consistent with the effects of electrical stimulation involving a pathway of extracellular Ca(2+) influx via voltage-gated calcium channels rather than from intracellular Ca(2+) repositories; and with downstream roles for calmodulin, calcineurin and nuclear factor of activated T-cells (NF-AT) rather than for phospholipase C and IP(3).

The influence of 70 and 120 kHz tonal signals on the behavior of harbor porpoises ( Phocoena phocoena) in a floating pen

Two harbor porpoises in a floating pen were subjected to five pure tone underwater signals of 70 or 120 kHz with different signal durations, amplitudes and duty cycles (% of time sound is produced). Some signals were continuous, others were intermittent (duty cycles varied between 8% and 100%). The effect of each signal was judged by comparing the animals’ surfacing locations and number of surfacings ( i.e. number of respirations) during test periods with those during baseline periods. In all cases, both porpoises moved away from the sound source, but the effect of the signals on respiration rates was negligible. Pulsed 70 kHz signals with a source level (SL) of 137 dB had a similar effect as a continuous 70 kHz signal with an SL of 148 dB (re 1 μPa, rms). Also, a pulsed 70 kHz signal with an SL of 147 dB had a much stronger deterring effect than a continuous 70 kHz signal with a similar SL. For pulsed 70 kHz signals (2 s pulse duration, 4 s pulse interval, SL 147 dB re 1 μPa, rms), the avoidance threshold sound pressure level (SPL), in the context of the present study, was estimated to be around 130 dB (re 1 μPa, rms) for porpoise 064 and around 124 dB (re 1 μPa, rms) for porpoise 047. This study shows that ultrasonic pingers (⩾70 kHz) can deter harbor porpoises. Such ultrasonic pingers have the advantage that they do not have a “dinner bell” effect on pinnipeds, and probably have no, or less, effect on other marine fauna, which are often sensitive to low frequency sounds.

A 0.65-to-1.4 nJ/Burst 3-to-10 GHz UWB All-Digital TX in 90 nm CMOS for IEEE 802.15.4a

We propose an all-digital UWB transmitter architecture that exploits the low duty cycle of impulse-radio UWB to achieve ultra-low power consumption. The design supports the IEEE 802.15.4a standard and is demonstrated for its mandatory mode. A digitally controlled oscillator produces the RF carrier between 3 and 10 GHz. It is embedded in a phase-aligned frequency-locked loop that starts up in 2 ns and thus exploits the signal duty cycle that can be as low as 3%. A fully dynamic modulator shapes the BPSK symbols in discrete steps at the 499.2 MHz chip rate as required by the standard. The transmitter can operate in any 499.2 MHz band of the standard between 3.1 and 10 GHz, and the generated signal fulfills the emission spectral mask. The jitter accumulation over a burst is below 6 psRMS, which is within specifications. The transmitter was realized in a 1 V 90 nm digital CMOS technology, and its power consumption drawn from a 1 V supply is from 0.65 mW at 3.1 GHz to 1.4 mW at 10 GHz for a 1 Mb/s data rate.

Ornithine decarboxylase activity of L929 cells after exposure to continuous wave or 50 Hz modulated radiofrequency radiation—a replication study

A replication study with some extensions was made to confirm enhancement of ornithine decarboxylase (ODC) activity in murine L929 fibroblasts after radiofrequency (RF) field exposure reported in earlier studies. L929 cells purchased from two cell banks were exposed for 2, 8, or 24 h to continuous wave or DAMPS (burst modulated at 50 Hz, with 33% duty cycle) signals at specific absorption rate (SAR) levels of 2.5 or 6.0 W/kg. Exposures were carried out in Crawford and waveguide chambers, at frequencies 835 and 872 MHz, respectively. The results did not confirm findings of previous studies reporting increased ODC activity in RF-exposed cells. When Crawford cell exposure system was used, ODC activity was either not affected (in the case of 8 or 24 h exposures) or decreased after 2 h exposure at the highest SAR level (6 W/kg). The decrease was most pronounced when cooling with air flow was not used, and is most likely related to increased temperature. The minor methodological differences (use of antibiotics, increased sensitivity of ODC assay) are not likely to explain the inconsistency of the findings of the present and previous studies. Different results were obtained in experiments with the waveguide system that involves more efficient temperature control. In this exposure system, ODC activity was increased after 8 h exposure at 6 W/kg. Further studies are warranted to explore whether this finding reflects a true non-thermal effect. The present study did not provide evidence for modulation-specific effects reported in earlier studies.

Observation of thermal effects due to an optical incident signal and high fluence on InGaAs/InP multiple-quantum-well saturable absorber nonlinear mirrors: evolution of characteristics and time constants

We observe the effects of a temperature increase on the characteristics of an InGaAs/InP multiple-quantum-well (MQW) saturable absorber (SA) in a microcavity provided by an optical input signal under normal incidence. The temperature increase on the nonlinear mirror (NLM) due to an optical signal depends on the energy time filling factor (FF) of this input signal (analogous to the signal's duty cycle, which is the ratio between the repetition period and the pulse duration) and hence depends on the repetition rate of the signal for a given pulse time width. This increase in temperature is mostly responsible for a shift in the reflectivity spectrum of the device toward higher wavelengths. In this experimental study, we show the shift of the resonance cavity versus the optical input power at high FF, and we evaluate the thermal time constant of an Fe-doped InGaAs/InP MQW NLM. Finally, we report the consequences of such thermal effects and high fluence on the reflectivity and contrast of two different InGaAs/InP NLMs when the input signal FF rises up to 25%, which gets close to telecommunication transmission conditions.

Generation of modified duobinary RZ signals by using one single dual-arm LiNbO3 modulator

We will demonstrate a simple method to generate modified duobinary return-to-zero (MD-RZ) signals by using only one single dual-arm Mach-Zehnder LiNbO/sub 3/ modulator (LN-MOD). Different duty cycle signals can be generated only by changing the time delay between two-arm electrical signals added on the LN-MOD. MD-RZ signals show high receiver sensitivity relative to duobinary nonreturn-to-zero signals.

A 50% duty‐cycle correction circuit for PLL output

AbstractWe proposed a circuit for correcting the fluctuations in the duty cycle caused by the increase in the device fluctuations due to the miniaturization of MOS devices and faster operating speeds. This correction circuit uses feedback control consisting of duty‐cycle detection and correction to correct the fluctuations in the duty cycle of a phase‐locked loop (PLL) circuit produced during the manufacturing process. A prototype of the proposed circuit having a 5‐V power supply voltage was fabricated using a 0.6‐µm process and measured. The variations in the duty cycle of the output voltage for an input signal having 20% to 80% duty cycle fluctuations could be suppressed to 0.21%, which is a 1/300 suppression of the input signal duty cycle fluctuations. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(2): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10085

SIGNAL-TO-NOISE RATIO GAIN IN NON-DYNAMICAL AND DYNAMICAL BISTABLE STOCHASTIC RESONATORS

It has recently been reported that in some systems showing stochastic resonance, the signal-to-noise ratio (SNR) at the output can significantly exceed that at the input; in other words, SNR gain is possible. We took two such systems, the non-dynamical Schmitt trigger and the dynamical double wellpotential, and using numerical and mixed-signal simulation techniques, we examined what SNR gains these systems can provide. In the non-linear response limit, we obtained SNR gains much greater than unity for both systems. In addition to the classical narrow-band SNR definition, we also measured the ratio of the total power of the signal to the power of the noise part, and it showed even better signal improvement. Here we present a brief review of our results, and scrutinise, for both the Schmitt-trigger and the double well potential, the behaviour of the SNR gain by stochastic resonance for different signal amplitudes and duty cycles. We also discuss the mechanism of providing gains greater than unity.

Improved light-load efficiency for synchronous rectifier voltage regulator module

DC/DC converter with high efficiency over a wide load range is necessary for many low voltage applications, such as battery supplied systems and micro-processor power supplies-voltage regulator module (VRM). In order to improve the efficiency of low voltage converters, synchronous rectifier technology is widely used. The disadvantage of this technology is low efficiency at light load. This paper proposes a new technology, which utilizes the duty cycle signal, to improve light load efficiency with simple implementation. Since current sensors are not required, high density and high efficiency can be achieved that makes the whole circuit suitable for integration. In the paper, two application examples are given. Experimental results verified that the proposed control schemes significantly improve the efficiency of synchronous rectifier buck converters at light load.

Design, optimization and simulation on microelectromagnetic pump

A four-layer electromagnetic micropump was designed, and its static and dynamic characters were studied from elements to full system. The mechanical model of the electromagnetic actuator was established, and some its geometric structural parameters were then optimized. The deflection of the pump membrane caused by the varying local magnetic driving forces was analyzed in particular by ANSYS FEM. Fluid theory and experiment data were used to analyze the microvalve. Full system model of the micropump and its differential equations were set up on the basis of physical liquid transmission procedure and system function block. Pulse and periodic pulse driving current responses were evaluated. The flow-frequency characteristic shows that the most effective driving frequency is 125 Hz. The effect of driving signal duty cycle and microvalve flow resistance was studied. The transfer function of this full system of micropump was also discussed.

Constant-frequency and frequency-modulated components in the echolocation calls of three species of small bats (Emballonuridae, Thyropteridae, and Vespertilionidae)

The echolocation calls of Rhychonycteris naso (Emballonuridae), Thyroptera tricolor (Thyropteridae), and Myotis riparius (Vespertilionidae) were recorded at the Cãno Palma Field Station in Costa Rica in February 1998. All three species produced echolocation calls at low duty cycle (signal on ~10% of the time). While T. tricolor produced low-intensity echolocation calls that were barely detectable when the bats were <0.5 m from the microphone, the other two species produced high-intensity calls, readily detectable at distances >5 m. Myotis riparius produced calls that swept from about 120 kHz to just over 50 kHz in about 2 ms. We found no evidence of harmonics in these calls. Rhynchonycteris naso and T. tricolor produced multiharmonic echolocation calls. In R. naso the calls included narrowband and broadband components and varied in bandwidth, sweeping from just under 100 kHz to around 75 kHz in over 5 ms. Most calls were dominated by the higher harmonic (ca. 100 kHz), but some also included a lower one (ca. 50 kHz). The calls of T. tricolor were 5-10 ms long and dominated by a single frequency (ca. 45 kHz), sometimes with a ca. 25 kHz component. The echolocation calls of all three species included frequency-modulated and constant-frequency components. While these terms describe the components of the echolocation calls, they do not necessarily describe the bats' echolocation behaviour.

Constant-frequency and frequency-modulated components in the echolocation calls of three species of small bats (Emballonuridae, Thyropteridae, and Vespertilionidae)

The echolocation calls of Rhychonycteris naso (Emballonuridae), Thyroptera tricolor (Thyropteridae), and Myotis riparius (Vespertilionidae) were recorded at the Cãno Palma Field Station in Costa Rica in February 1998. All three species produced echolocation calls at low duty cycle (signal on ~10% of the time). While T. tricolor produced low-intensity echolocation calls that were barely detectable when the bats were <0.5 m from the microphone, the other two species produced high-intensity calls, readily detectable at distances >5 m. Myotis riparius produced calls that swept from about 120 kHz to just over 50 kHz in about 2 ms. We found no evidence of harmonics in these calls. Rhynchonycteris naso and T. tricolor produced multiharmonic echolocation calls. In R. naso the calls included narrowband and broadband components and varied in bandwidth, sweeping from just under 100 kHz to around 75 kHz in over 5 ms. Most calls were dominated by the higher harmonic (ca. 100 kHz), but some also included a lower one (ca. 50 kHz). The calls of T. tricolor were 5-10 ms long and dominated by a single frequency (ca. 45 kHz), sometimes with a ca. 25 kHz component. The echolocation calls of all three species included frequency-modulated and constant-frequency components. While these terms describe the components of the echolocation calls, they do not necessarily describe the bats' echolocation behaviour.

Proliferative and synthetic response of bovine growth plate chondrocytes to various capacitively coupled electrical fields

In vitro monolayer cultures of growth plate chondrocytes isolated from newborn calf costochondral junctions were subjected to capacitively coupled electrical fields for 48 h. In part A, the electrical signal was a 60-kHz sine wave applied at different voltages so as to produce electrical fields at the pericellular level of 7, 20, 50, and 126 mV/cm. Incorporations of [3H]thymidine and [35S]sulfate were assayed to determine the effect of the above fields on cells proliferation and matrix synthesis, respectively. Proliferation was increased by 47% in the 20 mV/cm field whereas the same field decreased [35S]sulfate incorporation by 21%. These changes were significant at p less than 0.05 in both instances. In part B, the 20 mV/cm field was applied in a pulsed fashion to produce daily duty cycles of 100, 25, 2, and 0.25%. Incorporation of [3H]thymidine, [35S]sulfate, and [14C]proline per DNA were assayed. Results indicated that the 100, 25, and 0.25% percent duty cycles showed significantly (p less than 0.01-0.05) increased proliferation, whereas the 0.25% signal (5 ms on/495 ms off for 6 h/day) significantly decreased [14C]proline incorporation. We conclude that the biologic response of cells in vitro is signal specific, and that the total amount of electrical energy required to stimulate the growth plate chondrocyte to increased proliferation is very small since the total time the 0.25% duty cycle signal was only 3.6 min of a 24-h period.

Measurement of Loop Gain with the Digital Modulator

A loop gain measurement technique for switching regulators using a digital modulator is introduced. While the conventional technique injects and measures the analog signals, the proposed digital modulator injects a digital perturbation and measures the resultant duty cycle modulation. Since the duty cycle signal, derived from all feedback loops, provides the ultimate control of a switching regulator, the loop gain defined at the duty cycle modulator is unique. Employing the digital modulator, this loop gain can be measured even with a switching regulator employing the current injected control. Furthermore, this new technique overcomes false measurement problems found in the conventional technique when the feedback signal at the point where the loop gain is measured contains a pulsating nature.

Treatment of sciatic denervation disuse osteoporosis in the rat tibia with capacitively coupled electrical stimulation. Dose response and duty cycle.

We determined the dose-response characteristics of a low-voltage, high-frequency, capacitively coupled electrical signal that reverses an established osteoporosis in a rat tibial model with sciatic neurectomy. The electrical signals were delivered by means of stainless-steel gel-coated electrodes. In the first part of the study, the shape (sine wave) and frequency (sixty kilohertz) of the signal were kept constant while the voltage was varied from 0.01 to ten volts, peak to peak. Control osteoporotic and sham osteoporotic animals showed a mean loss of tibial ash weight of 19 and 17 per cent, respectively, twenty-eight days after sciatic neurectomy plus twelve days of no treatment using sham electrodes. Rats that were subjected to 0.25, 0.50, 1.0, 2.5, and 5.0 volts, peak to peak, for twelve days beginning on the twenty-eighth day after sciatic neurectomy all showed mean losses of tibial ash weight that were significantly less than those of the controls. The rats that had a 0.5-volt peak-to-peak signal showed the least mean loss of tibial ash weight (only 6 per cent). We concluded that a capacitively coupled electrical signal, delivered through gel-coated electrodes, can largely reverse an established disuse osteoporosis due to neurectomy in the rat tibia. In the second part of the study, the duty cycles of a sine-wave, sixty-kilohertz, 0.5-volt peak-to-peak signal were varied (12.5, 50, and 100 per cent on), and the wet, dry, and ash weights were determined and compared with those of unstimulated osteoporotic controls. Only the 100 per cent duty-cycle signal was effective in reversing the loss of bone mass in the neurectomized tibiae.

A digital VOR converter and display unit

This paper describes a method of digital measurement and display of VOR phase signals. These are received by airborne equipment and provide navigational information to the pilot. By means of a phase-locked master frequency, the phase difference between the received signals is converted into a pulse train advancing the display counters. The phase between the two signals (indicating the position relative to the ground transmitter) La displayed as a three-digit number and by one out of 36 circular arranged LED's. Subtraction of the measured angle and a selected one is performed by EX-OR gating of two 50% duty cycle signals derived from pulses whose relative position with respect to a reference pulse represents these angles. Deviation is displayed by a linear array of LED's. By means of a phase-locked master frequency, the phase difference between the received signals is converted into a pulse train advancing the display counters. The phase between the two signals (indicating the position relative to the grou...

Loudness Balances Employing Signals with Unequal Duty Cycles

The alternate binaural loudness balance technique was employed to investigate the effects of duty cycle (the percentage of time the sound is on) upon the perceived magnitude of 1000-Hz pure-tone signals. The reference signal was fixed in the right ear at 50-dB sound-pressure level (SPL). In the left ear, the comparison signal intensity was adjusted via a Békésy audiometer to yield equal interaural loudnesses. The loudness of interrupted signals increased as the signal duty cycle was increased. A low-duty-cycle comparison signal was consistently judged to be softer than an equally intense high-duty-cycle reference signal. Furthermore, a high-duty-cycle comparison signal was consistently judged louder than a low-duty-cycle reference signal of the same intensity. The greatest interaural loudness disparity was observed for the experimental conditions in which the interaural duty-cycle difference (high duty cycle minus low duty cycle) was 80%. During a substantial number of trials, this relationship between duty cycle and loudness increased in magnitude throughout the 4-min balancing period. Duty-cycle-loudness effects were enhanced when a 400-msec silent interval separated alternating tones. The results of this study may be incorporated to assist in the explanation of the occurrence of the type-V Békésy pattern in clinical audiology. In addition, they lead to questions concerning the interpretation of experiments in which interrupted signals are presented for loudness evaluation such as experiments on loudness adaptation.

Influence of Binaural Interaction on the Measurement of Perstimulatory Loudness Adaptation

Perstimulatory loudness adaptation was measured by two techniques which utilized varying amounts of simultaneous contralateral stimulation. In the first experiment a single-SDLB (simultaneous dichotic loudness balance) method was employed with comparison signals of 200- and 2000-msec duration and with an adapting signal of 8 sec. More adaptation was noted when the longer comparison signal was employed. In the second experiment, a modified tracking procedure utilized comparison signal duty cycles of 1623% and 50%. The higher duty cycle yielded a greater magnitude of test-ear adaptation than did the lower duty cycle. The results support the hypothesis that perstimulatory loudness adaptation is dependent on simultaneous binaural stimulation and, in addition, is related to the amount of that stimulation. It is therefore concluded that adaptation is not a monaural or a purely peripheral phenomenon.

Duty Cycle Effects on the Loudness of Repeated Tones

The alternate binaural loudness balance technique was employed to investigate the alleged influence of duty cycle (the percentage of time the sound is on) upon perceived magnitude of 1000-Hz tones. The reference tone was fixed in the right ear at 50 dB SPL. In the comparison ear, the signal intensity was adjusted via the Békésy audiometer to derive equal interaural loudness. The perceived loudness of repeated signals increased as the signal duty cycle was increased. A low-duty cycle comparison tone was consistently judged to be softer than an equally intense reference signal of higher duty cycle. Furthermore, a high-duty cycle comparison signal was consistently judged louder than a low-duty cycle reference signal at equal intensities. The greatest interaural loudness disparity was observed for the experimental conditions in which the interaural duty cycle difference was 80%. During a substantial number of trials this direct relationship between duty cycle and loudness grew in magnitude for the extent of the 4-min balancing period. Duty-cycle-loudness effects were enhanced when a 400-msec silent interval separated alternating tones. These results help explain the occurrence of the type-V Békésy pattern in clinical audiology as well as results on some loudness-adaptation studies.