In-loop filters have been comprehensively explored during the development of video coding standards due to their remarkable noise-reduction capabilities.In the early stage of video coding,in-loop filters,such as the d...In-loop filters have been comprehensively explored during the development of video coding standards due to their remarkable noise-reduction capabilities.In the early stage of video coding,in-loop filters,such as the deblocking filter,sample adaptive offset,and adaptive loop filter,were performed separately for each component.Recently,cross-component filters have been studied to improve chroma fidelity by exploiting correlations between the luma and chroma channels.This paper introduces the cross-component filters used in the state-ofthe-art video coding standards,including the cross-component adaptive loop filter and cross-component sample adaptive offset.Crosscomponent filters aim to reduce compression artifacts based on the correlation between different components and provide more accurate pixel reconstruction values.We present their origin,development,and status in the current video coding standards.Finally,we conduct discussions on the further evolution of cross-component filters.展开更多
This paper proposes a novel Gm-C loop filter instead of a conventional passive loop filter used in a phase-locked loop. The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence ...This paper proposes a novel Gm-C loop filter instead of a conventional passive loop filter used in a phase-locked loop. The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence the process variations of passive elements of resistance R and capacitance C can be overcome and the chip area is greatly reduced. Furthermore, the MASH 1-1-1 sigma-delta （ZA） modulator is adopted for performing the fractional division number and hence improves the phase noise as well. Measured results show that the locked phase noise is -114.1 dBc/Hz with lower Gm-C bandwidth and -111.7 dBm/C with higher Gm-C bandwidth at 1 MHz offset from carrier of 5.68 GHz. Including pads and built-in Gm-C filter, the chip area of the proposed frequency synthesizer is 1.06 mm2. The output power is -8.69 dBm at 5.68 CHz and consumes 56 mW with an off-chip buffer from 1.8-V supply voltage.展开更多
An extended state observer(ESO)-based loop filter is designed for the phase-locked loop(PLL)involved in a disturbed grid-connected converter(GeC).This ESO-based design enhances the performances and robustness of the P...An extended state observer(ESO)-based loop filter is designed for the phase-locked loop(PLL)involved in a disturbed grid-connected converter(GeC).This ESO-based design enhances the performances and robustness of the PLL,and,therefore,improves control performances of the disturbed GeCs.Besides,the ESO-based LF can be applied to PLLs with extra filters for abnormal grid conditions.The unbalanced grid is particularly taken into account for the performance analysis.A tuning approach based on the well-designed PI controller is discussed,which results in a fair comparison with conventional PI-type PLLs.The frequency domain properies are quantitatively analysed with respeet to the control stability and the noises rejection.The frequency domain analysis and simulation results suggesti that the performances of the generated ESO-based controllers are comparable to those of the PI control at low frequency,while have better ability to atenuate high-frequency measurement noises.The phase margin decreases slightly,but remains acceptable.Finally,experimental tests are conducted with a hybrid power hardwarein-the-loop benchmark,in which balanced/unbalanced cases are both explored.The obtained results prove the effectiveness of ESO based PLLs when applied to the disturbed GeC.展开更多
This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track t...This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track the phase of BPSK signal in real time. Thus, the maximum date rate can be significantly extended to the half of the carrier frequency(f_(carrier)) with a very compact size compared to prior PLL-based BPSK demodulators. Furthermore, eliminating all the static power in our LPF-less PLL, the energy efficiency is obviously improved. Fabricated in a 40-nm CMOS process, our prototype occupies 0.0012-mm^(2)core active area, and achieves the maximum data rate of 6.78 Mb/s (f_(carrier)/2) at f_(carrier)of 13.56 MHz. The power consumption and energy efficiency is 4.47 μW and 0.66 pJ/bit at 6.78-Mb/s data rate, respectively.展开更多
This paper proposes an area-saving dual-path loop filter（LPF）for low-voltage integrated phase-locked loops（PLLs）.With this LPF,output current of the lowpass-path charge-pump（CP）is B times（B〉1）as great as that...This paper proposes an area-saving dual-path loop filter（LPF）for low-voltage integrated phase-locked loops（PLLs）.With this LPF,output current of the lowpass-path charge-pump（CP）is B times（B〉1）as great as that of the integration-path CP.By adding voltages across these two paths,the zero-capacitance is magnified B times equivalently.As a result,the chip size is greatly reduced.Based on this LPF,a 1.2 V 3.5 GHz-band PLL is fabricated in SMIC 0.18μm RFCMOS technology.Its zero-capacitance is only 1/30 of that in conventional second-order LPFs. Measured data show that,at a frequency of 3.20 GHz,phase noise is–120.2 dBc/Hz at 1 MHz offset,reference spur is–72 dBc,and power is 24 mW.展开更多
By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm i...By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.展开更多
A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conj...A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conjunction with the F-P LD will realize a filter with multiple passbands. By adjusting the wavelengths of the multiple optical carriers, multiple passbands are merged into a single passband with a broadened bandwidth. By varying the number of the optical carrier, the bandwidth can be adjusted. The central frequency can be tuned by adjusting the wavelength of the multiple optical carriers simultaneously. A single-passband filter implemented by two optical carriers is experimentally demonstrated.展开更多
A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the pol...A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.展开更多
A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top ...A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top output with a high extinction ratio. Compared to filters consisting of the conventional Panda polarization maintaining fibre, filters based on a high birefringence photonic crystal fibre loop mirror have better temperature stability. This kind of filter can be expected to be used widely in Wavelength-division-multiplexing(WDM) systems in the future.展开更多
Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, the...Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.展开更多
In the wireless guidance system, the signals that receiver received has obvious Doppler shift for the high dynamic characteristic of the carrier. A new solution of carrier frequency tracking loop with frequency modify...In the wireless guidance system, the signals that receiver received has obvious Doppler shift for the high dynamic characteristic of the carrier. A new solution of carrier frequency tracking loop with frequency modifying system is put forward. The characteristic of cross product auto frequency control and the second order loop filter in this loop are analyzed. The simulation shows that this loop can accomplish frequency tracking well in high dynamic circumstance.展开更多
A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γT filter model, adaptive loop structure mod- el and adaptive loop ban...A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γT filter model, adaptive loop structure mod- el and adaptive loop bandwidth model respectively, are added in the presented tracking loop com- pared with the traditional carrier tracking loop based on the second-order frequency lock loop （FLL） assisting third-order phase lock loop （PLL） loop filter. And the optimization methods for the track- ing bandwidth and the carrier loop order are analyzed. The real-time estimation methods of the dy- namic parameters, the velocity, acceleration and jerk along the line of sight （LOS） between the sat- ellite and the receiver＇ s antenna, and the measurement parameters are discussed based on the pres- ented α-β-γ filter algorithm. A method is introduced to improve the filter＇ s dynamic response to meet high dynamic application by self-adjusted α-β-γ filter coefficient used in the tracking loop. The performance of three cases with different carrier tracking loop is compared by simulation.展开更多
Since the satellite communication goes in the trend of high-frequency and fast speed, the coefficients updating and the precision of the traditional pre-distortion feedback methods need to be further improved. On this...Since the satellite communication goes in the trend of high-frequency and fast speed, the coefficients updating and the precision of the traditional pre-distortion feedback methods need to be further improved. On this basis, this paper proposes dual loop feedback pre-distortion, which uses two first-order Volterra filter models to reduce the computing complexity and a dynamic error adjustment model to construct a revised feedback to ensure a better pre-distortion performance. The computation complexity, iterative convergence speed and precision of the proposed method are theoretically analyzed. Simulation results show that this dual loop feedback pre-distortion can speed the updating of coefficients and ensure the linearity of the amplifier output.展开更多
Suppressing jitter noises in a phase locked loop（ PLL） is of great importance in order to keep precise and continuous track of global positioning system （GPS）signals characterized by low carrier-to-noise ratio（ C...Suppressing jitter noises in a phase locked loop（ PLL） is of great importance in order to keep precise and continuous track of global positioning system （GPS）signals characterized by low carrier-to-noise ratio（ C/No ）. This article proposes and analyzes an improved Kalman-filter-based PLL to process weak carrier signals in GPS software receivers. After reviewing the optimal-bandwidth-based traditional second-order PLL, a Kalman-filter-based estimation algorithm is implemented for the new PLL by decorrelating the model error noises and the measurement noises. Finally,the efficiency of this new Kalman-filter-based PLL is verified by experimental data. Compared to the traditional second-order PLL, this new PLL is in position to make correct estimation of the carrier phase differences and Doppler shifts with less overshoots and noise disturbances and keeps an effective check on the disturbances out of jitter noises in PLL. The results show that during processing normal signals,this improved PLL reduces the standard deviation from 0. 010 69 cycle to 0. 007 63 cycle, and for weak signal processing,the phase jitter range and the Doppler shifts can be controlled within ± 17° and ±5 Hz as against ±25° and ＋ 15 Hz by the traditional PLL.展开更多
This paper introduces an electrical drives control architecture combining a fractional-order controller and a setpoint pre-filter. The former is based on a fractional-order proportional-integral(PI) unit, with a non-i...This paper introduces an electrical drives control architecture combining a fractional-order controller and a setpoint pre-filter. The former is based on a fractional-order proportional-integral(PI) unit, with a non-integer order integral action, while the latter can be of integer or non-integer type. To satisfy robustness and dynamic performance specifications, the feedback controller is designed by a loop-shaping technique in the frequency domain. In particular, optimality of the feedback system is pursued to achieve input-output tracking. The setpoint pre-filter is designed by a dynamic inversion technique minimizing the difference between the ideal synthesized command signal(i.e., a smooth monotonic response) and the prefilter step response. Experimental tests validate the methodology and compare the performance of the proposed architecture with well-established control schemes that employ the classical PIbased symmetrical optimum method with a smoothing pre-filter.展开更多
Sensitivity loop shaping using add-on peak filters is a simple and effective method to reject narrow-band disturbances in hard disk drive （HDD） servo systems. The parallel peak filter is introduced to provide high-g...Sensitivity loop shaping using add-on peak filters is a simple and effective method to reject narrow-band disturbances in hard disk drive （HDD） servo systems. The parallel peak filter is introduced to provide high-gain magnitude in the concerned frequency range of open-loop transfer function. Different from almost all the known peak filters that possess second-order structures, we explore in this paper bow high-order peak filters can be designed to improve the loop shaping performance. The main idea is to replace some of the constant coefficients of common second-order peak filter by frequency-related transfer functions, and then differential evolution （DE） algorithm is adopted to perform optimal design. We creatively introduce chromosome coding and fitness function design, which are original and the key steps that lead to the success of DE applications in control system design. In other words, DE is modified to achieve a novel design for hard disk drive control. Owing to the remarkable searching ability of DE, the expected shape of sensitivity function can be achieved by incorporating the resultant high-order peak filter in parallel with baseline feedback controller. As a result, a seventh-order peak filter is designed to compensate for contact-induced vibration in a high-density HDD servo system, where the benefits of high-order filter are clearly demonstrated.展开更多
Power line(PL)interference is one significant artifact in electrocardiography(ECG)that needs to be reduced to ensure accurate recording of cardiac signals.Because PL interference is non-stationary and has varying freq...Power line(PL)interference is one significant artifact in electrocardiography(ECG)that needs to be reduced to ensure accurate recording of cardiac signals.Because PL interference is non-stationary and has varying frequency,phase,and amplitude in ECG measurement,adaptive techniques are often necessary to track and cancel the interference.In this paper we present a phase-locked loop(PLL)-based adaptive filter to cancel PL interference.The PLL obtains the reference signal that is fed into the adaptive filter to remove the PL interference at the central frequency of 50 Hz.It is found that the technique can effectively cancel PL interference in real ECG signals and,when compared with some existing techniques such as least mean squares(LMS)adaptive filter,the new technique produces better results in terms of signal-to-interference ratio(SIR).展开更多
An efficient way of noise reduction has been presented: A modified Costas loop called as Masterpiece. The basic version of the Costas loop has been developed for SSB SC demodulation, but the same circuit can be applie...An efficient way of noise reduction has been presented: A modified Costas loop called as Masterpiece. The basic version of the Costas loop has been developed for SSB SC demodulation, but the same circuit can be applied for QAM (quadrature amplitude modulation) demodulation as well. Noise sensitivity of the basic version has been decreased. One trick is the transformation of the real channel input into complex signal, the other one is the application of our folding algorithm. The result is that the Masterpiece provides a 4QAM symbol error rate (SER) of 6 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> for input signal to noise ratio (SNR) of <span style="white-space:nowrap;">−</span>1 dB. In this paper, an improved version of the original Masterpiece is introduced. The complex channel input signal is normalized, and rotational average is applied. The 4QAM result is SER of 3 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> for SNR of <span style="white-space:nowrap;">−</span>1 dB. At SNR of 0 dB, the improved version produces 100 times better SER than that the original Costas loop does. In our times, this topic has a special importance because by application of our Masterpiece, all dangerous field strengths from 5G and WiFi, could be decreased by orders of magnitude. The Masterpiece can break the Shannon formula.展开更多
基金supported in part by National Science Foundation of China under Grant No.62031013PCL-CMCC Foundation for Science and Innovation under Grant No.2024ZY1C0040+1 种基金New Cornerstone Science Foundation for the Xplorer PrizeHigh performance Computing Platform of Peking University。
文摘In-loop filters have been comprehensively explored during the development of video coding standards due to their remarkable noise-reduction capabilities.In the early stage of video coding,in-loop filters,such as the deblocking filter,sample adaptive offset,and adaptive loop filter,were performed separately for each component.Recently,cross-component filters have been studied to improve chroma fidelity by exploiting correlations between the luma and chroma channels.This paper introduces the cross-component filters used in the state-ofthe-art video coding standards,including the cross-component adaptive loop filter and cross-component sample adaptive offset.Crosscomponent filters aim to reduce compression artifacts based on the correlation between different components and provide more accurate pixel reconstruction values.We present their origin,development,and status in the current video coding standards.Finally,we conduct discussions on the further evolution of cross-component filters.
文摘This paper proposes a novel Gm-C loop filter instead of a conventional passive loop filter used in a phase-locked loop. The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence the process variations of passive elements of resistance R and capacitance C can be overcome and the chip area is greatly reduced. Furthermore, the MASH 1-1-1 sigma-delta （ZA） modulator is adopted for performing the fractional division number and hence improves the phase noise as well. Measured results show that the locked phase noise is -114.1 dBc/Hz with lower Gm-C bandwidth and -111.7 dBm/C with higher Gm-C bandwidth at 1 MHz offset from carrier of 5.68 GHz. Including pads and built-in Gm-C filter, the chip area of the proposed frequency synthesizer is 1.06 mm2. The output power is -8.69 dBm at 5.68 CHz and consumes 56 mW with an off-chip buffer from 1.8-V supply voltage.
基金This paper was supported by G2elab,Grenoble INP,University Grenoble Alpes,France and School of Engineering,HES-sO,Valais,Switzerlandfunding provided by Haute Ecole Specialisee de Suisse occidentale(HES-SO)
文摘An extended state observer(ESO)-based loop filter is designed for the phase-locked loop(PLL)involved in a disturbed grid-connected converter(GeC).This ESO-based design enhances the performances and robustness of the PLL,and,therefore,improves control performances of the disturbed GeCs.Besides,the ESO-based LF can be applied to PLLs with extra filters for abnormal grid conditions.The unbalanced grid is particularly taken into account for the performance analysis.A tuning approach based on the well-designed PI controller is discussed,which results in a fair comparison with conventional PI-type PLLs.The frequency domain properies are quantitatively analysed with respeet to the control stability and the noises rejection.The frequency domain analysis and simulation results suggesti that the performances of the generated ESO-based controllers are comparable to those of the PI control at low frequency,while have better ability to atenuate high-frequency measurement noises.The phase margin decreases slightly,but remains acceptable.Finally,experimental tests are conducted with a hybrid power hardwarein-the-loop benchmark,in which balanced/unbalanced cases are both explored.The obtained results prove the effectiveness of ESO based PLLs when applied to the disturbed GeC.
基金supported by the National Natural Science Foundation of China under grant 62222409 and 62174153by Key Research Program of Frontier Sciences, CAS, under grant ZDBS-LY-JSC008。
文摘This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track the phase of BPSK signal in real time. Thus, the maximum date rate can be significantly extended to the half of the carrier frequency(f_(carrier)) with a very compact size compared to prior PLL-based BPSK demodulators. Furthermore, eliminating all the static power in our LPF-less PLL, the energy efficiency is obviously improved. Fabricated in a 40-nm CMOS process, our prototype occupies 0.0012-mm^(2)core active area, and achieves the maximum data rate of 6.78 Mb/s (f_(carrier)/2) at f_(carrier)of 13.56 MHz. The power consumption and energy efficiency is 4.47 μW and 0.66 pJ/bit at 6.78-Mb/s data rate, respectively.
文摘This paper proposes an area-saving dual-path loop filter（LPF）for low-voltage integrated phase-locked loops（PLLs）.With this LPF,output current of the lowpass-path charge-pump（CP）is B times（B〉1）as great as that of the integration-path CP.By adding voltages across these two paths,the zero-capacitance is magnified B times equivalently.As a result,the chip size is greatly reduced.Based on this LPF,a 1.2 V 3.5 GHz-band PLL is fabricated in SMIC 0.18μm RFCMOS technology.Its zero-capacitance is only 1/30 of that in conventional second-order LPFs. Measured data show that,at a frequency of 3.20 GHz,phase noise is–120.2 dBc/Hz at 1 MHz offset,reference spur is–72 dBc,and power is 24 mW.
基金Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120the National Natural Science Foundation of China under Grant No 61177059
文摘By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61302026,61275067 and 61575034the Jiangsu Natural Science Foundation under Grant No BK2012432
文摘A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conjunction with the F-P LD will realize a filter with multiple passbands. By adjusting the wavelengths of the multiple optical carriers, multiple passbands are merged into a single passband with a broadened bandwidth. By varying the number of the optical carrier, the bandwidth can be adjusted. The central frequency can be tuned by adjusting the wavelength of the multiple optical carriers simultaneously. A single-passband filter implemented by two optical carriers is experimentally demonstrated.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11274181,10974100,and 10674075)the Tianjin Key Program of Application Foundations and Future Technology Research Project,China (Grant No. 10JCZDJC24300)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120031110033)
文摘A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.
基金supported by the"100 Projects"of Creative Research for the Undergraduates of Nankai University under Grant(BX6-224)
文摘A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top output with a high extinction ratio. Compared to filters consisting of the conventional Panda polarization maintaining fibre, filters based on a high birefringence photonic crystal fibre loop mirror have better temperature stability. This kind of filter can be expected to be used widely in Wavelength-division-multiplexing(WDM) systems in the future.
文摘Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.
文摘In the wireless guidance system, the signals that receiver received has obvious Doppler shift for the high dynamic characteristic of the carrier. A new solution of carrier frequency tracking loop with frequency modifying system is put forward. The characteristic of cross product auto frequency control and the second order loop filter in this loop are analyzed. The simulation shows that this loop can accomplish frequency tracking well in high dynamic circumstance.
基金Supported by the Ministerial Level Foundation(B222006060)
文摘A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γT filter model, adaptive loop structure mod- el and adaptive loop bandwidth model respectively, are added in the presented tracking loop com- pared with the traditional carrier tracking loop based on the second-order frequency lock loop （FLL） assisting third-order phase lock loop （PLL） loop filter. And the optimization methods for the track- ing bandwidth and the carrier loop order are analyzed. The real-time estimation methods of the dy- namic parameters, the velocity, acceleration and jerk along the line of sight （LOS） between the sat- ellite and the receiver＇ s antenna, and the measurement parameters are discussed based on the pres- ented α-β-γ filter algorithm. A method is introduced to improve the filter＇ s dynamic response to meet high dynamic application by self-adjusted α-β-γ filter coefficient used in the tracking loop. The performance of three cases with different carrier tracking loop is compared by simulation.
文摘Since the satellite communication goes in the trend of high-frequency and fast speed, the coefficients updating and the precision of the traditional pre-distortion feedback methods need to be further improved. On this basis, this paper proposes dual loop feedback pre-distortion, which uses two first-order Volterra filter models to reduce the computing complexity and a dynamic error adjustment model to construct a revised feedback to ensure a better pre-distortion performance. The computation complexity, iterative convergence speed and precision of the proposed method are theoretically analyzed. Simulation results show that this dual loop feedback pre-distortion can speed the updating of coefficients and ensure the linearity of the amplifier output.
基金National Natural Science Foundation of China(40671155)National High-tech Research and Development Programof China(2006AA12A108)Research Program of Hong Kong Polytech-nic University(G-U203)
文摘Suppressing jitter noises in a phase locked loop（ PLL） is of great importance in order to keep precise and continuous track of global positioning system （GPS）signals characterized by low carrier-to-noise ratio（ C/No ）. This article proposes and analyzes an improved Kalman-filter-based PLL to process weak carrier signals in GPS software receivers. After reviewing the optimal-bandwidth-based traditional second-order PLL, a Kalman-filter-based estimation algorithm is implemented for the new PLL by decorrelating the model error noises and the measurement noises. Finally,the efficiency of this new Kalman-filter-based PLL is verified by experimental data. Compared to the traditional second-order PLL, this new PLL is in position to make correct estimation of the carrier phase differences and Doppler shifts with less overshoots and noise disturbances and keeps an effective check on the disturbances out of jitter noises in PLL. The results show that during processing normal signals,this improved PLL reduces the standard deviation from 0. 010 69 cycle to 0. 007 63 cycle, and for weak signal processing,the phase jitter range and the Doppler shifts can be controlled within ± 17° and ±5 Hz as against ±25° and ＋ 15 Hz by the traditional PLL.
基金partially supported by the Australian Research Council(DP160104994)
文摘This paper introduces an electrical drives control architecture combining a fractional-order controller and a setpoint pre-filter. The former is based on a fractional-order proportional-integral(PI) unit, with a non-integer order integral action, while the latter can be of integer or non-integer type. To satisfy robustness and dynamic performance specifications, the feedback controller is designed by a loop-shaping technique in the frequency domain. In particular, optimality of the feedback system is pursued to achieve input-output tracking. The setpoint pre-filter is designed by a dynamic inversion technique minimizing the difference between the ideal synthesized command signal(i.e., a smooth monotonic response) and the prefilter step response. Experimental tests validate the methodology and compare the performance of the proposed architecture with well-established control schemes that employ the classical PIbased symmetrical optimum method with a smoothing pre-filter.
基金supported by National Natural Science Foundation of China(Nos.61640310 and 61433011)
文摘Sensitivity loop shaping using add-on peak filters is a simple and effective method to reject narrow-band disturbances in hard disk drive （HDD） servo systems. The parallel peak filter is introduced to provide high-gain magnitude in the concerned frequency range of open-loop transfer function. Different from almost all the known peak filters that possess second-order structures, we explore in this paper bow high-order peak filters can be designed to improve the loop shaping performance. The main idea is to replace some of the constant coefficients of common second-order peak filter by frequency-related transfer functions, and then differential evolution （DE） algorithm is adopted to perform optimal design. We creatively introduce chromosome coding and fitness function design, which are original and the key steps that lead to the success of DE applications in control system design. In other words, DE is modified to achieve a novel design for hard disk drive control. Owing to the remarkable searching ability of DE, the expected shape of sensitivity function can be achieved by incorporating the resultant high-order peak filter in parallel with baseline feedback controller. As a result, a seventh-order peak filter is designed to compensate for contact-induced vibration in a high-density HDD servo system, where the benefits of high-order filter are clearly demonstrated.
文摘Power line(PL)interference is one significant artifact in electrocardiography(ECG)that needs to be reduced to ensure accurate recording of cardiac signals.Because PL interference is non-stationary and has varying frequency,phase,and amplitude in ECG measurement,adaptive techniques are often necessary to track and cancel the interference.In this paper we present a phase-locked loop(PLL)-based adaptive filter to cancel PL interference.The PLL obtains the reference signal that is fed into the adaptive filter to remove the PL interference at the central frequency of 50 Hz.It is found that the technique can effectively cancel PL interference in real ECG signals and,when compared with some existing techniques such as least mean squares(LMS)adaptive filter,the new technique produces better results in terms of signal-to-interference ratio(SIR).
文摘An efficient way of noise reduction has been presented: A modified Costas loop called as Masterpiece. The basic version of the Costas loop has been developed for SSB SC demodulation, but the same circuit can be applied for QAM (quadrature amplitude modulation) demodulation as well. Noise sensitivity of the basic version has been decreased. One trick is the transformation of the real channel input into complex signal, the other one is the application of our folding algorithm. The result is that the Masterpiece provides a 4QAM symbol error rate (SER) of 6 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> for input signal to noise ratio (SNR) of <span style="white-space:nowrap;">−</span>1 dB. In this paper, an improved version of the original Masterpiece is introduced. The complex channel input signal is normalized, and rotational average is applied. The 4QAM result is SER of 3 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> for SNR of <span style="white-space:nowrap;">−</span>1 dB. At SNR of 0 dB, the improved version produces 100 times better SER than that the original Costas loop does. In our times, this topic has a special importance because by application of our Masterpiece, all dangerous field strengths from 5G and WiFi, could be decreased by orders of magnitude. The Masterpiece can break the Shannon formula.
