Frequency Synthesis Method Research Articles

Design and Implementation of a Ka-Band Frequency Source Based on DS+DDS Hybrid Method

Abstract This article proposes a design scheme for a broadband agile frequency conversion Ka-band frequency source, which adopts a mixed frequency synthesis method of DS+DDS. This method combines the advantages of DDS such as fast frequency switching speed, small frequency step, and wide DS frequency bandwidth, and uses segmented filtering to effectively suppress the disadvantage of DDS spurious error. DS adopts an up conversion and double frequency doubling scheme to broaden the frequency band, with simple design and low cost. The deterioration of phase noise is offset by selecting a low phase noise PLL. Actual measurement shows that the output bandwidth of the frequency source is 8GHz, with spurious suppression ≤ −61dBc, frequency switching time ≤ 140ns, output power ≥ 15dBm, step frequency of 1MHz, and phase noise ≤ −100dBc/Hz@1kHz, meet the design requirements.

Синтез системы управления температурным полем углеграфитового теплового узла при выращивании кристаллов лейкосапфиров

This article is devoted to the development of a control system of the temperature field in the carbon graphite thermal unit during the growth of leucosapphire crystals by the horizontal directional crystallization (HDC) method. The paper presents the results of developing a model of automated control system for maintaining the specified temperature conditions at the crystallization front. The work solves the following tasks: the mathematical model of the crystal growth process was developed, analysis and identification of the control object based on the numerical solution, calculation of distributed high-precision controller parameters using frequency synthesis method, computer modeling of a closed-loop control system. Based on the obtained transient characteristics, direct quality indicators of the synthesized control system were calculated, which confirmed that the calculated settings of the corrective device allow to achieve the control objective – maintaining the specified temperature conditions at the crystallization front.

Maximum deviation sliding search based stepped frequency synthesis method for marine vibroseis research

In marine exploration, the shorter emitting time can effectively improve the effects and increase the inversion resolution. In order to reduce the time, stepped frequency synthesis is used for the vibrator in this paper. It can regenerate a wide bandwidth reflect the signal to use multiple narrow bandwidth vibroseis. The effect of phase jump between signals on the peak side lobe ratio of the synthesized signal is analyzed. The reasons for the inaccuracy of phase correction in a practical geological environment are investigated. Finally, the Maximum Deviation Sliding Search method is proposed in this paper. This method is validated to accurately correct the phase of signals in complex subsurface environments. In the experiment, the corrected signal improves the peak partials ratio by 42% and 160% compared with the uncorrected signal.

An ultra-wideband ultra-low phase noise frequency synthesizer

In order to solve the problems of frequency band expansion in direct frequency synthesis method and serious additional deterioration of phase noise in phase-locked frequency synthesis method, a mixer phase-locked frequency synthesizer combining direct analog frequency synthesis and phase-locked frequency synthesis is designed. In order to reduce the frequency multiplication times of the phase detector and optimize the phase noise of the output signal, the frequency synthesizer uses a comb spectrum generator to excite an offset signal with ultra-low phase noise for mixing. In the meantime, the error-lock problem is solved in ultra-wideband mixing phase-locked loop (PLL). An ultra-wideband frequency synthesizer with frequency band 12 GHz–24 GHz and step of 100 MHz is designed in this paper. The experimental test of the frequency synthesizer shows that the phase noise of the frequency synthesizer is better than -116 dBc/Hz@1 kHz at low frequency 12 GHz, and −109 dBc/Hz@1 kHz at high frequency 24 GHz. This phase noise is basically the same as the direct analog frequency synthesis method and is 20 dB better than the conventional phase-locked scheme. The frequency synthesis method has the advantages of ultra-wideband and ultra-low phase noise, and it can be used in the high performance electronic equipment.

A New Method for Evaluating the Bearing Capacity of the Bridge Pile Socketed in the Soft Rock

Aiming at the rock-socketed pile in the soft rock area, this paper studies the inherent constitutive relationship between the vertical restraint stiffness at the pier bottom and the bearing capacity of the pile foundation. A new method to evaluate the bearing capacity of the pile foundation is proposed. Based on the Rayleigh energy method and the Southwell frequency synthesis method, the analytical expression of the vertical vibration fundamental frequency of the pier was calculated, and the constraint stiffness expression of the pier bottom was derived. By investigating the impact of parameters on the bearing capacity coefficient of the pile foundation, the fitting formula of the bearing capacity coefficient was obtained by multiple linear regression. Then, with this method, the vertical fundamental frequency of the pier was obtained through a field dynamic test to calculate the vertical constraint stiffness and evaluate the bearing capacity of the rock-socketed pile in the soft rock area. This method can overcome the shortcomings of the traditional static load test method, such as the high cost, long cycle, and poor representativeness. Finally, this method’s accuracy was verified by comparing field measurements and finite element simulation results. The results show that the difference between the code design constraint stiffness and the constraint stiffness by the frequency synthesis method was about 0.7%, and the bearing capacity difference between the analytical solution and the numerical simulation was small. The new method is accurate and effective.

Multi-Mode Lasers for Self-Forced Opto-Electronic Oscillators in Compact Frequency Synthesizers

Advanced telecommunication, imaging, and remote sensing systems require reliable ultra-high stability local oscillators. Particularly, coherent detection of digital data signals relies on a low aperture jitter of local oscillators in addition to high signal to noise ratio to achieve a very low bit-error-rate (BER). Frequency stabilized local oscillators are required with phase noise of smaller than −120 dBc/Hz at 10 kHz offset carrier and low aperture jitters of below 50 fs for RF sources of 10 GHz. Self-forced opto-electronic oscillation techniques of self- injection locking (SIL) combined with self-phase locking (SPLL) employ low loss long optical delays for frequency stabilizations through comparison of instantaneous signals and delayed versions. A compact design of multi-mode laser (MML) is presented here by employing self-forced oscillation combined with self-mode locking of an MML. Proof of concept of this novel approach is reported using a custom designed InGaAsP/InP chip using Smart Photonics foundry service, where multi-quantum well semiconductor optical amplifiers (SOA), carrier injection based phase modulator (PM), front and back (a common) distributed Bragg reflectors (DBR), and external electro-absorption modulators (EAM) are designed and physically modeled based on the foundry process design kit (PDK). A compact realization of self-mode locked MML with 5 modes to a fixed inter-modal oscillation frequency is presented, where the beat notes of the inter-modal oscillation are generated over X-band to form a frequency stabilized synthesizer. The PM bias control of two MLL lasers with common DBR is used to tune this opto-electronic oscillator from 11 GHz to 13 GHz with a frequency resolution of 110 kHz. Self-forced oscillation techniques of SILPLL combined with self-mode-locking (SML) has provided frequency synthesis with measured phase noise at 10 kHz offset (and aperture jitter) improved from −36 dBc/Hz (58ps) for the free-running MML to −92 dBc/Hz (68 fs) using SILPLL and SML of only 5 correlated modes. Analytical modeling has predicted that increasing the number of self-mode-locking modes from 5 to 13 will result in 18 dB improvement in phase noise. Performance comparison of this opto-electronic frequency synthesis method is made against various commercially available X-band frequency synthesizers that use full electrical solutions.

Low-noise hybrid frequency synthesizers based on direct digital and direct analog synthesis

The research of the possibility of using hybrid frequency synthesizers based on direct digital and direct analog methods of frequency synthesis as heterodynes of modern spectrum analyzers constructed according to the superheterodyne scheme is presented. The main advantages of such synthesizers over traditionally used heterodyne schemes based on direct digital and indirect frequency synthesis methods are shown. The requirements for the heterodynes of the first mixing stages of spectrum analyzers are presented. A block diagram of a wideband heterodyne generating a frequency range from 4000 MHz to 8000 MHz with a step not exceeding 1 Hz is proposed. Formulas for calculating the main frequency ratios in the structure of the heterodyne have been developed. A mathematical model of phase noise power spectral density (PSD) depending on the offset frequency from the carrier is developed. The noise characteristics of the proposed scheme are studied using the model. It is determined that at the output frequency of the heterodyne equal to 4521,4 MHz, the level of phase noise PSD is: minus 90 dBc/Hz at the offset frequency equal to 100 Hz; minus 140 dBc/Hz at the offset frequency equal to 100 kHz. It is shown that the hybrid synthesizer based on direct digital and direct analog synthesis methods has an advantage in the level of phase noise from 5 to 30 dB over the low-noise heterodynes of modern spectrum analyzers at frequencies above 1 kHz from the carrier. Additional advantages of the proposed scheme are a simple architecture, low power consumption and high frequency tuning speed due to the absence of phaselocked loops in the structure of the heterodyne.

Automation of adjustment stages by high-performance semiconductor converters

In this paper, methods of frequency synthesis of semiconductor converter control are proposed, allowing automation of the commissioning stages of high-performance semiconductor frequency converters. Attention is paid to increasing the reliability of the synthesis of the regulation system using the method of synchronous detection of measured signals. It is shown that the proposed frequency synthesis methods allow us to construct a mathematical model of the object being identified. The proposed generalized methods for the synthesis of current control loops, electromagnetic moment, based on the method of experimental frequency characteristics can be useful for technological objects, which allow the study of frequency characteristics without disturbing the conditions of the process. The proposed method has been quite successfully tested on the example of objects of drilling rigs: electric drive for lifting winch and electric drives for drilling pumps. By increasing the reliability of the synthesis of the current control loops and the electromagnetic torque of semiconductor converters, it was possible to significantly expand the uniform transmission band of the current control loop by about 20%. It is established that an experimental technique for determining the frequency characteristics of CCL has been proposed and tested, which makes it possible to evaluate the capabilities of CCLs of various electric drives and indicates the possibilities for expanding the band of uniform transmission of the frequencies of the CCLs under investigation. On the other hand, the extension of the band of uniform transmission of CCL allows increasing the limiting values of the rotational speed of the motor. This allows you to raise the speed of powerful compressor units without the use of multipliers to 6000 - 9000 rpm.

Input signal shaping based on harmonic frequency response function for suppressing nonlinear optical frequency in frequency-scanning interferometry.

Frequency-scanning interferometry (FSI) using an external cavity diode laser (ECDL) is essential for many applications of the absolute distance measurement. However, owing to the hysteresis and creep of the piezoelectric actuator inherent in the ECDL, the optical frequency scanning exhibits a nonlinearity that seriously affects the phase extraction accuracy of the interference signal and results in the reduction of the measurement accuracy. To suppress the optical frequency nonlinearity, a harmonic frequency synthesis method for shaping the desired input signal instead of the original triangular wave is presented. The effectiveness of the presented shaping method is demonstrated through the comparison of the experimental results. Compared with an incremental Renishaw interferometer, the standard deviation of the displacement measurement of the FSI system is less than 2.4 μm when driven by the shaped signal.

Table, Interpolation and Iteration Functional Converters for the Method of Direct Digital Frequency Synthesis

Table, Interpolation and Iteration Functional Converters for the Method of Direct Digital Frequency Synthesis

MAIN DEVELOPMENT PERIODS OF FREQUENCY SYNTHESIZERS

Paper considers frequency synthesis methods, synthesizer’s main parameters and modern ways of increasing frequency synthesizer’s quality.

Design of an experimental platform to investigate the effects of audible sounds on plant growth

An experimental platform was developed to investigate the effects of audible sound (20 Hz to 20 MHz) on plant growth promotion, which included a microcontroller-based embedded system for audible sound adjustment and analysis. The direct digital frequency synthesis (DDFS) method was used to generate various waveforms of sound in the platform. Soundproof glass and mufflers were used to reduce background noise. The developed system was tested on various plants, including hydroponic tomatoes, celery and mung bean. The testing results showed that the developed platform could produce pure tone and mixing audible sound with high stability and accuracy, make octave analysis of the sound under experimental environments, and the background noise in the testing chamber of the platform was lower than 55 dB(A) when the compression engine was working. The developed experimental platform has a great potential on facilitating scientific research on acoustic biology effects on plants and collecting real-time experimental data. Keywords: plant growth, background noise, acoustic biology effect, direct digital frequency synthesis, sound sensor DOI: 10.3965/j.ijabe.20150805.1556 Citation: Cai W M, Zhu S M, Wang N, He H N, Ying B H. Design of an experimental platform to investigate the effects of audible sounds on plant growth. Int J Agric & Biol Eng, 2015; 8(5): 162－169.

A direct digital synthesizer of compound wideband signals

Principles of construction and structural and circuit designs of direct digital synthesizers based on the method of direct digital frequency and signal synthesis are described. The block and circuit diagrams of the direct digital synthesizer of compound wideband signals are presented. This synthesizer is used to synthesize signals with the amplitude, frequency, and phase modulation in a frequency range from 0.001 to 200MHz.

An analog modulated simulation source for X-ray pulsar-based navigation

In this paper a high resolution X-ray simulation source is proposed and designed to verify the navigation based on X-ray pulsar in the simulation experience system. The simulation source consists of an arbitrary signal generator and a grid controlled X-ray tube. According to the grid tube's characteristic curve, the data of the pulsar standard pulse template are converted. Then using the method of direct digital frequency synthesis, the converted data are synthesized to waveforms, called the analog modulated grid voltage. In the grid controlled X-ray tube, the grid voltage changes the number of electrons hitting on the target and controls the X-ray intensity. With an analog modulated pulse profile applied on the tube grid electrode, the tube will emit X-rays which will match photons' statistical distribution and simulate the X-ray pulsar profile extremely well. The properties of Crab pulsar simulation source are tested in X-ray pulsar navigation simulation experience system. The results of the test are as follows: Comparing the tested pulse profile with the standard pulsar profile, we have time correlation coefficient is 0.9774, and frequency correlation coefficient is 0.9853. The X-ray photon flux is 1.90 ph·cm-2·s-1, the pulsed fraction is 76.15%, and the half-width half maximum is 1.879 ms. These results show that the X-ray simulation source has several merits, such as: strong ability to simulate the X-ray, low cost and simple operation. So it is an important means for the improvement of X-ray pulsar navigation.

G100042 車載用モータによる室内異音シミュレータの開発 : 周波数・時間領域逐次型伝達特性合成法の提案

G100042 車載用モータによる室内異音シミュレータの開発 : 周波数・時間領域逐次型伝達特性合成法の提案

A Novel Full Phase-Coherent Frequency Synthesis Method for SFWF Radar Application

A novel method of full phase-coherent synthesis is proposed in this paper, which uses the frequency-converting technology and the phase-locked loop to fulfill the transmission and tracking of the frequency and phase between the main loop and secondary loops. This method, which differs from the traditional converting-filtering scheme, can solve the tradeoff between the frequency difference and the bandwidth of the full phase-coherent outputs, and it can have a high isolation between the outputs. A Ka-band full phase-coherent frequency synthesizer is implemented based on the idea. The measured results show that this novel full phase-coherent frequency synthesis method proposed in this paper is correct. The frequency synthesizer has full phase-coherent characteristics along with a very low phase noise, fast hopping time, high spurious rejection, and very high isolation between the main output and the secondary output.

Human Bioelectrical impedance Measuring Method Based on Principle of Multi-frequency and Multi-segment

In the traditional human bioelectrical impedance measurement methods, measurement approach is simplex and accuracy is low. A multi-frequency and multi-segment human bioelectrical impedance measurement method is proposed, which adopts eight electrodes segments measurement technique and direct frequency synthesis method to produce multi-frequency excitation signal, and then achieves multi-frequency and multi-segment measurement of bioelectrical impedance. The results of experiments show that this method effectively improves the measurement accuracy; the relative error of measured impedance magnitude is less than 1% while the absolute error of phase is less than 1 degree.

A new frequency synthesis method based on "flying-adder" architecture

The "flying-adder" frequency and phase synthesis architecture was presented in papers published by Mair and Xiu in 2000 and Xiu and You in 2002. This architecture contains many excellent features and it can be implemented/integrated easily in a very large scale integration system. However, it has a drawback of inherent jitter on the output frequency, due to the frequency modulation of the output frequency. This brief presents a new frequency synthesis method that eliminates such jitter. The frequency accuracy of this new architecture is studied; subsequently, the frequency error upper bound is found. Furthermore, it leads to the development of a scheme that can be used to derive the frequency error distribution. The comparison to "integer-N" and "fractional-N" phase-locked loop (PLL) based frequency synthesis techniques is also presented.

Frequency domain down-conversion of HDTV using an optimal motion compensation scheme

In the MPEG-2 Test Model 5, the down-conversion of an interlaced sequence is obtained by prefiltering and subsampling each field of the image sequence after it has been fully decoded. Although the quality is very good, the cost of such a system is quite high owing to large memory requirements. As a result, low-resolution decoders have been proposed to reduce some of the costs incurred by this scheme. Here, incoming Discrete Cosine Transform (DCT) blocks are subject to a down-conversion process within the decoding loop; hence, the motion compensation is performed using the down-converted images. In past work, it has been proven that the optimal filters for performing this motion compensation are intimately related to the method of down-conversion. Therefore, the choice of down-conversion filter is viewed as the primary variable affecting the quality of the down-converted sequence when such an optimal motion compensation scheme is considered. In the conventional method of frequency domain down-conversion, the 4 × 4 low-frequency coefficients are extracted from each 8 × 8 block. Two problems arise from this method: First, the discarding of high frequency data will introduce a disturbing amount of drift; and second, severe blocking artifacts will result in areas of large motion. To remedy the drift problem, a new method of down-conversion which better preserves high-frequency data is presented. This method is referred to as frame-based frequency synthesis. Then, to overcome the blocking artifacts, the previous method is extended to a field-based frequency synthesis method. Our simulation results clearly indicate that the amount of drift can be significantly reduced by retaining high-frequency data and that severe blocking artifacts are eliminated by using the field-based method. In addition, the quality achieved by the proposed field-based frequency synthesis is much closer to the high-quality results produced after full-resolution decoding. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 274–282, 1998

Design of a digitally based ΔE measurement system

The magnetic field dependence of Young's modulus is a useful technique for probing the magnetic moment configuration and the anisotropy energy density of magnetostrictive soft magnetic materials. More recently, a high resolution vibrating reed system, based on the closed loop operation of an analogue lock in amplifier (LIA), coupled with an analogue voltage controlled oscillator (VCO) has been used. This system has shown that such measurements are capable of providing new information about subtle domain rearrangements during magnetisation of as-cast amorphous wires. The performance of this system is limited by the use of the analogue components, especially the VCO, to a resolution of a few parts in 10/sup 5/. To overcome this limitation a digital LIA and a function generator which employs digital frequency synthesis methods have been used in a new system. This offers an order of magnitude reduction in noise, with a frequency stability of better than 10/sup -6/ HZ, which can provide a resolution better than 2 parts in 10/sup 6/ for Young's modulus. Example of data obtained are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>