Minimum Frequency Shift Research Articles

基于串行最小频移键控的8进制调制的研究

基于串行最小频移键控的8进制调制的研究

The Implementation of MSK Based on DSP and Complex Bandpass Processing

A novel method of minimum frequency shift keying (MSK) which based on digital signal processing (DSP) and complex bandpass processing is proposed in the article. According to the bit value of the input data, the MSK complex bandpass signal is directly produced and then is complex bandpass filtered, the real part of the complex bandpass signal is fetched to achieve the MSK modulation. The receiving signal of MSK is sampled, and then complex bandpass filtered to attain the complex bandpass signal. The complex bandpass signal and conjugate signal of its delayed version and the phase shift factor are multiplied together. According to the imaginary part of the product, the original data is recovered. The design method of complex bandpass filter is introduced also.

Real-time measurement of photocatalytic reactions using a monolithic QCM array

This paper reports a real-time measurement of photocatalytic reactions by using a miniaturized quartz-crystal microbalance (QCM) array. The QCM was miniaturized and integrated on the same quartz plate using microfabrication techniques. Two QCMs were located close to each other, with one of the QCMs used as a reference sensor for the accurate and independent determination of mass change effects and environmental change effects. The QCM output was compensated for frequency shifts induced by ultra violet (UV) irradiation by subtracting the frequency shift of the reference sensor. The minimum detectable frequency shift under the irradiation was within 1 Hz. The measured photodecomposition speed of methylene blue dye on a TiO2-coated QCM agreed well with that evaluated by the standard optical testing method under dry condition. The developed method enabled us to measure the photodecomposition of a surfactant on a TiO2-coated QCM with sub-nanogram mass resolution in real time.

Generation Linewidth of an Auto-Oscillator with a Nonlinear Frequency Shift: Spin-Torque Nano-Oscillator

It is shown that the generation linewidth of an auto-oscillator with a nonlinear frequency shift (i.e., an auto-oscillator in which frequency depends on the oscillation amplitude) is substantially larger than the linewidth of a conventional quasilinear auto-oscillator due to the renormalization of the phase noise caused by the nonlinearity of the oscillation frequency. The developed theory, when applied to a spin-torque auto-oscillator, gives a good description of experimentally measured angular and temperature dependences of the linewidth.

Femtogram mass sensing platform based on lateral extensional mode piezoelectric resonator

This letter introduces a resonant mass sensor that is based on a lateral extensional mode piezoelectric resonator and has a minimum detectable mass of 10−15g at room temperature and atmospheric pressure. The resonator with size of about 200×50×1μm3 has a quality factor (Q) of >1400 at 60MHz, and as small as 0.1ppm shift of its resonant frequency can be detected. The 0.1ppm detection capability corresponds to a mass uncertainty of only about 4.6fg. We have experimentally demonstrated a minimum detectable frequency shift of ∼1.6ppm due to absorption of isopropanol vapor (73fg) on the sidewalls of the parylene-coated lateral extensional mode piezoelectric resonator.

Simple approach to determining the minimum measurable stress length and stress measurement accuracy in distributed Brillouin sensing

A simple approach is proposed for quantifying the errors in measuring the Brillouin frequency shifts associated with stresses whose lengths are shorter than the pulse length. The smallest detectable Brillouin frequency shift is thus determined with respect to the size of the stressed sections and the frequency resolution. The lowest detectable frequency shift is found to be approximately 42% of the Brillouin gain natural linewidth. A worst-case iso-error curve that associates the minimum frequency shift to the length of the stressed region is derived. A minimum resolvable frequency shift and minimum detectable stress length are defined with an approach based on a Rayleigh equivalent criterion.

Micromachined acoustic resonant mass sensor

This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm/sup 2//g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200-300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of 10/sup -9/ g/cm/sup 2/ on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to 10/sup -8/ g/cm/sup 2/ change on the sensor surface.

Criterion for subpulse-length resolution and minimum frequency shift in distributed Brillouin sensors

We introduce a Rayleigh equivalent criterion to measure stressed section shorter than the spatial resolution of a distributed Brillouin sensor. Under this criterion for the worst-case of any given sensing length, the minimum resolvable strain length is 1/2 of the pulse length (w) with Brillouin frequency uncertainty of 5% or 0.8w with 2% frequency uncertainty. This is smaller than the pulse length.

Acute effect of CyA A (Neoral®) on large artery hemodynamics in renal transplant patients

CyA A (CyA) may induce intrarenal vasoconstriction, endothelial dysfunction, and hypertension. There are only two contradictory reports describing the acute effect of CyA on renal resistances measured by color Doppler flowmetry. Therefore, we studied the acute influence of oral CyA on arterial haemodynamics by assessing simultaneous changes in blood pressure, applanation tonometry-derived pulse wave analysis and duplex ultrasound-derived intrarenal resistance indices. Augmentation index (AIx) (difference between the first and second systolic peak on the aortic pressure waveform divided by the pulse pressure = AIx) was determined from contour analysis of arterial waveforms recorded by applanation tonometry using the AtCor device in 18 live-related renal transplants (11 females/7 males, age = 32.0 +/- 8.1 years, transplantation duration = 17.5 +/- 16.1 months, and mean serum creatinine = 133 +/- 70 micromol/L). All studies were performed just before (C0), and 2 hours after (C2) the oral administration of CyA. At the same C0 and C2 moments the resistive index (RI) = (peak systolic frequency shift - minimum diastolic frequency shift)/peak systolic frequency shift, and pulsatility index (PI) = (peak systolic frequency shift - minimum diastolic frequency shift)/mean frequency shift were calculated from Doppler recorded waveforms. Blood pressure and heart rate did not differ significantly at C0 and at C2 serum levels: 134.3/82.9 vs. 128.1/80.0 mm Hg and 72.0 vs. 71.0 beats/min, respectively, despite a marked increase in whole blood concentration (CyA(C0)= 90.8 +/- 45.9 vs. CyA(C2)= 547.4 +/- 251.3 ng/mL) (P= 0.05). Mean AIx fell significantly from 17.2 +/- 13.8 to 12.9 +/- 14.2 (P < 0.0001). There was no correlation between the extent (expressed as absolute or relative change) of the measured alteration in AIx and total administered CyA dose, or increment in blood level between C0 and C2. In support, the intake of CyA did not induce a significant increase in Doppler resistance (RI(C0)= 0.68 +/- 0.08 vs. RI(C2)= 0.70 +/- 0.09) and pulsatility indices (PI(C0)= 1.32 +/- 0.31 vs. PI(C2)= 1.33 +/- 0.28). Finally, three patients were studied twice (>1 week): one under two levels of creatinine, one with no antihypertensives, and a third receiving verapamil initially. All these maintained a significant decrease in AIx at C2 from C0 supporting the reproducibility of the phenomenon. We demonstrate that Neoral CyA acutely improves large arterial compliance function and does not induce an acute rise in intrarenal resistance in stable renal transplant subjects with normal renal function. We speculate that there may be an effect of vitamin E, the diluent vehicle in which CyA is carried (1000 IU/100 mg CyA), shown to improve endothelial function.

New FM Detection Techniques for Scanning Probe Microscopy

New FM demodulation techniques capable of detecting the fast frequency deviation of a cantilever of a noncontact atomic force microscope are proposed and their features were demonstrated by experiments. The techniques entail the frequency conversion of an input FM signal to a pair of zero-Hz-centered signals with a mutual phase difference of 90 deg, differentiation or Hilbert transformation, multiplication and subtraction. Since the center frequency and scale factor are determined by different processes, a high sensitivity, a fast response and a precise center frequency are achievable at the same time. The developed circuitry is capable of detecting a minimum frequency shift of 0.1 Hz. The maximum response bandwidth is 100 kHz.

Analog frequency modulation detector for dynamic force microscopy

A new analog frequency modulation (FM) detector (demodulator) for dynamic force microscopy (DFM) is presented. The detector is designed for DFM by utilizing the FM detection method where the resonance frequency shift of the force sensor is kept constant to regulate the distance between a tip and a sample surface. The FM detector employs a phase-locked loop (PLL) circuit using a voltage-controlled crystal oscillator (VCXO) so that the thermal drift of the output signal is negligibly reduced. The PLL is used together with a frequency conversion (heterodyne) circuit allowing the FM detector to be used for a wide variety of force sensors with the resonance frequency ranging from 10 kHz to 10 MHz. The minimum detectable frequency shift was as small as 0.1 Hz at the detection bandwidth of 1 kHz. The detector can track a resonance frequency shift as large as 1 kHz. We also present some experimental results including the observations of the Si(111)-7×7 reconstructed surface and fullerene molecules deposited on the surface by DFM using this FM detector.

Effects of Aluminum Thickness on the Temperature Characteristics of Leaky Surface Wave Filters on LST-cut Quartz Substrate

The LST-cut of quartz has better frequency-temperature stability than the conventional ST-cut. In this paper, theoretical temperature dependence of the center frequency and insertion loss of SAW filters on LST-cut quartz is compared with experimental results. Theoretical values including effect of the metallization thickness are in very good agreement with experiments. It is found by theoretical calculation that minimum temperature frequency shift and change of insertion loss are exhibited. These results should be applicable for practical temperature stable LST-cut SAW filters.

Identification of Hepatic Cirrhosis by Duplex Doppler Ultrasound Value of the Hepatic Artery Resistive Index

Pulsed Doppler Ultrasound was used to analyze hepatic artery wave forms near the porta hepatis. The Resistive Index (RI) = [peak systolic frequency shift (A)--minimum diastolic frequency shift (B)]/[peak systolic frequency shift (A)] has been calculated from this information. Two populations have been compared; 30 fit hospital staff members, 23 male, 7 female, age mean 37 years and range 19 to 73 years, and 33 cirrhotic potential liver transplant recipients, 16 male, 17 female, age mean 48 years and range 11 to 78 years. The RI was successfully obtained in 94% of the potential transplant patients. There is a significant difference between the RI of the controls (mean = 0.72, SE = 0.2, n = 27) and the cirrhotics (mean = 0.82, SE = 0.2, n = 31), P less than 0.0001. Using a cut off of greater than 0.77 this index has a sensitivity, specificity and overall accuracy of 68%, 70% and 69% respectively.

Vaginosonographic velocimetry of both main uterine arteries by visual vessel recognition and pulsed Doppler method during pregnancy

In 88 pregnant women (7 to 40 weeks' gestation) we performed Doppler velocimetric studies of the uterine artery on its course through the parametrium by means of the newly developed, frontally radiating duplex sector scanner. This device enabled us to visually recognize the vessel and apply the more refined pulsed wave system. In 71 of 88 women, we were able to obtain measurements from both uterine arteries. We found significant differences in the maximum systolic to minimum diastolic frequency shift (AB ratio) up to 4 between the right and left vessels in the first and second trimester. In the third trimester, the differences almost disappeared (mean ± SD AB ratio difference 0.4 ± 0.3) in these uncomplicated pregnancies. We also report our mean values (first, second, and third trimesters) of the AB ratio and the pulsatility index as an average from the right and left side measurements. Both values declined during the course of pregnancy (AB ratio, 5.5, 2.9, and 2.1; pulsatility index, 2.5, 1.7, and 1.3). We conclude that, with some experience, this scanner has the advantage of visually recognizing the vessel under study and allows measurements in both main uterine arteries. The average of the right and left measurements provides a better summary of uterine perfusion. Due to the significant right/left difference in the AB ratio, unilateral measurements of the uterine artery may give erroneous results during the first and second trimesters. Theoretically, the pulsed system provides a “cleaner” signal, but the values are comparable to those of devices that apply a continuous wave system.

Route Guidance System for Automobile Drivers by Speech Synthesis

This paper describes a route guidance system for automobile drivers by speech synthesis and road-vehicle digital communication. The system, included in a computer-aided driving instruction system installed on a training ground, aims to guide a driving trainee along a route fixed by an instructor. The system consists of a personal computer in the control center, on-board computers in each automobile, and inductive loop antennas. At an inductive loop antenna buried in the road and connected to the control center, transmitting the ID number, each automobile receives data code, with which speech data stored in the ROM of the on-board computer are retrieved and edited to a route guidance message. It is outputted in a synthesized female voice by ADPCM. The carrier frequency for the road-vehicle communication from a road is 223.2 kHz and that from a vehicle is 304.8 kHz. Data, modulated by minimum frequency shift keying, are transmitted at 9600 bps. The data frame is based on the HDLC. Experiments by trainees show that the route guidance system by speech synthesis is effective on the training ground.

QPSK, Staggered QPSK, and MSK--A Comparative Evaluation

Bandwidth- and power-efficient quadrature carrier modulation techniques are identified, evaluated, and compared. The modulation techniques include quadrature phase shift keying (QPSK), staggered QPSK (SQPSK), and minimum (frequency) shift keying (MSK). High quality QPSK, SQPSK, and MSK transmitters and receivers were used in the evaluation, along with a computer simulation program which modeled the hardware. Both linear and nonlinear channels were included in the comparative investigation. The agreement between simulated and measured results is shown to be excellent. In the comparison of modulation techniques, the effects of channel filtering (band limiting), nonlinearities, detection techniques, and phase equalization are addressed. The application-oriented results are intended to be an aid in selecting modulation and detection implementations, and in predicting the performance of linear and nonlinear communication systems. For systems with imperfections, data are presented for determination of passive detection filters which can outperform matched integrate and dump (I&D) filters.

Pulse and Spectrum Manipulation in the Minimum (Frequency) Shift Keying (MSK) Format

The minimum (frequency) shift keying (MSK) format is generalized to enable further improvements in the spectrum while retaining the well-known constant envelope property and the excellent communications efficiency of MSK. A specific alternative to MSK is presented, and the spectrum is compared with that of MSK. The theoretical limitations on possible further spectrum improvements are discussed.

The Effect of Tandem Band and Amplitude Limiting on the E&amp;lt;inf&amp;gt;b&amp;lt;/inf&amp;gt;/N&amp;lt;inf&amp;gt;o&amp;lt;/inf&amp;gt;Performance of Minimum (Frequency) Shift Keying (MSK)

Minimum (frequency) shift keying (MSK) is a digital modulation technique which can be viewed either as frequency-shift keying (FSK) with peak frequency deviation precisely equal to \pm(1/4)R_{L} where R L is the link bit rate or as an offset-keyed quaternary phase-shift-keyed modulation. In the absence of bandwidth or amplitude limiting between the modulator and the demodulator, the E_{b}/N_{0} performance of MSK is identical to that of coherently detected binary phase-shift keying (PSK). This paper briefly reviews and defines MSK. It then presents a system model in which a tandem assembly of a transmit band-limiting filter, a hard limiter, and a receive band-limiting filter are interposed between an ideal modulator and demodulator. This model is aimed at simulating actual links (such as spacecraft-to-ground links) in which channel bandwidth (B_{c}) constraints are important, postmodulation filtering at RF is objectionable, and transmission through efficient transmitters which operate as amplitude limiters is a requirement. An analysis then derives the E_{b}/N_{0} degradation due to both bandwidth and amplitude limiting. Band limiting alone causes intersymbol interference on the data carried by each of the quadrature phasors but no interphasor crosstalk under the set of assumptions used. With amplitude limiting also present, an interphasor crosstalk mechanism exists. The average symbol distortion, symbol energy reduction, and noise reduction are derived for several periodic waveforms. For composite systems with 3-dB bandwidth (B_{L}) -to-R L ratios of at least 0.6, the theoretical E_{b}/N_{0} degradation is less than 1 dB. Parametric experimental data are then reported on the postmodulation spectrum of a transmitter with band limiting plus subsequent hard amplitude limiting. Data are also presented on the E_{b}/N_{0} degradation measured using tandem assemblies of a bandlimiting filter, an amplitude limiter, and a second band-limiting filter. The amplitude limiter substantially increases the level of the spectral side lobes beyond the main lobe. It was found that for all significant values of transmit bandpass filtering plus subsequent amplitude limiting, 99 percent of the transmitted energy is contained within B c = 1.1 R L . Further, little E_{b}/N_{0} degradation (tenths of a decibel) was measured if B L was greater than 0.65 R L . A rapid degradation of E_{b}/N_{0} occurred when B_{L} = 0.55 R_{L} . These data apply for the band-band-amplitude-band limited system model. The amplitude limiter placed between the transmit and receive filters caused interphasor crosstalk and distortion of the data symbol shapes as predicted; however, E_{b}/N_{0} degradation caused by the amplitude-limiting effects by themselves (which are a function of B L ) never exceeded 0.3 to 0.5 dB for the cases studied.

A New Frequency-Division Radiotelegraph Multiplex System (MADFAS)

A frequency-division multiplex system (MADFAS) is described for operation at HF with less bandwidth than is commonly allowed. The reduction in required bandwidth is achieved by using oscillators with greater frequency stability, and signaling by FSK with the minimum frequency shift compatible with the keying speed. Details on the design and operational characteristics of the system are presented.

Temperature Effects in Microwave Ferrite Devices

With proper choice of shape, it is possible to minimize the frequency shift of ferromagnetic resonance in microwave ferrite components operating over a wide range of ambient temperatures. Calculations have been made for minimum resonance frequency shift change in saturation moment. Curves relating the resonance frequency shift as a function of saturation magnetization are plotted for several ferrite geometries. Design curves are presented for reducing dependence of resonance frequency on temperature.