For the optimization of dynamic range and bandwidth of digital intermediate frequency receiver(DIFR), main factors affecting them and their relationships are studied. Firstly, the DIFR sensitivity, bandwidth, noise fa...For the optimization of dynamic range and bandwidth of digital intermediate frequency receiver(DIFR), main factors affecting them and their relationships are studied. Firstly, the DIFR sensitivity, bandwidth, noise factor of radio frequency (RF) analog front-end (RFAF), and processing gain of intermediate frequency(IF) sampling are analyzed. Secondly, the constraint relationship of the noise factor of RFAF, the signal-to-noise ratio of ADC and the dynamic range of DIFR are studied. The relationship between the dynamic range and the RFAF gain, and that of the extended dynamic range and the RF AGC(automatic gain control) step are educed and simulated. These results can be used as theory foundations and design references for the implementation and optimization of the large dynamic range and wideband DIFR.展开更多
This paper proposes a novel zero Intermediate Frequency (IF) receiver for Multi-Carrier (MC) Direct-Sequence Code-Division Multiple Access (DS-CDMA) based on multicar-rier mode of cdma2000 system. The proposed receive...This paper proposes a novel zero Intermediate Frequency (IF) receiver for Multi-Carrier (MC) Direct-Sequence Code-Division Multiple Access (DS-CDMA) based on multicar-rier mode of cdma2000 system. The proposed receiver employs direct RF-to-baseband down-conversion, sampling at a rate equal to the bandwidth of the baseband multicarrier signal and complex-valued coefficient FIR filters. This receiver avoids the need for arrays of high Q analog bandpass filters, has a much lower sampling rate half of that of conventional receiver and offers significant savings in hardware implementation. Analytic and simulation results show that the presented receiver performs well for both the AWGN channel and Rayleigh fading channel.展开更多
In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF a...In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF and phase shift time were calculated by using the TMF contact model and the large phase shift of the magnetic field at a higher frequency was conductive to the dispersion process of residual plasma. The arc velocity was higher at 800 Hz than at 400 Hz. It can be inferred that TMF will encourage arc movement at 800 Hz. Moreover, the arc movement has an impact on the arc voltage. Because of the increasing length of the arc column with a high arc velocity, the elongated arc causes the arc voltage to increase. Specifically, the volt-ampere characteristics of the vacuum arc are divided into three stages in this paper. The higher the frequency, the greater the initial rate of rise in the arc voltage and the larger the area surrounded by arc volt-ampere characteristics. The correlations between the arc voltage and the amplitude and frequency of the current are also presented.展开更多
Arc motion and splitting of vacuum arc at intermediate frequency（400-800 Hz） were investigated under transverse magnetic field（TMF）.The experiment was performed on cup-type TMF contacts with contact diameter of 40...Arc motion and splitting of vacuum arc at intermediate frequency（400-800 Hz） were investigated under transverse magnetic field（TMF）.The experiment was performed on cup-type TMF contacts with contact diameter of 40 mm and a contact gap of 4 mm in a single-frequency circuit.With high-speed photography we characterized the arc appearance at different arc currents from 3.3 kA-rms to 10 kA-rms at intermediate frequencies.As arc current increases from3.3 kA-rms to 10 kA-rms the arc appearance changes obviously.When current value is 3.3 kArms（current frequency 400-800 Hz）,there is almost no splitting arc;when the current exceeds5 kA-rms（current frequency 400-800 Hz）,the arc rotates at a speed above 20 m/s,accompanied by an observable splitting arc.The splitting arc could be observed at different frequencies and the arc-voltage had no noises when splitting occurred.The motion direction and the velocity of arc column were studied.Finally,the formation of a split arc was discussed.展开更多
In-phase/quadrature （I/Q） mismatch is a key problem in zero intermediate frequency （ZIF） receiver architectures. Although integration and careful layout can alleviate I/Q mismatch, circuit and system level calibra...In-phase/quadrature （I/Q） mismatch is a key problem in zero intermediate frequency （ZIF） receiver architectures. Although integration and careful layout can alleviate I/Q mismatch, circuit and system level calibrations are also needed due to process variations and variable operating conditions. The amplitude im- balance between I/Q channels was calibrated using a modified R-2R ladder to achieve fine linear-in-dB variable gain. A downconversion mixer working in the 2,4-GHz band was developed for a wireless local area network （WLAN） ZIF receiver using 0.25μm complementary metal-oxide semiconductor （CMOS）. The twostage mixer configuration relaxes the tradeoff between noise and linearity. Experimental results verify the fine linear-in-dB variable conversion gain of the mixer, which can also be used as part of an automatic gain control （AGC）loop.展开更多
In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at ...In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at intermediate frequency(360-800 Hz)was conducted and the results were compared with a butt contact with the same contact diameter(41 mm)and the same material.By analyzing the arc behavior,arc voltage characteristics,arc energy,current interrupting capacity,ablation of the anode contact and condensation of the arc products at a 3 mm gap,the differences in their vacuum arc characteristics were determined.The correlations of their arc energy with the amplitude and the frequency of the current were also achieved.Analysis suggests that the ruled curved contact has strong application potentiality because of its low arc energy,low arc voltage noise and arc voltage peak,light ablation on the surface of the anode contact and high interrupting capacity.展开更多
To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the interm...To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the intermodulation signal and intermediate frequenc y signal.Based on the frequency conversion technology,an exclusion algorithm i s proposed a nd the actual implementation of the algorithm is given.The application resu lts show that the exclusion algorithm can identify the intermodulation signal exactly and eliminate the bad influence on the frequency measurement.展开更多
Objective: the purpose of this study is to study the therapeutic effect of Sanxiang Shuangzhu Powder, a traditional Chinese medicine introduced at medium frequency, on infantile diarrhea, and to provide new ideas and ...Objective: the purpose of this study is to study the therapeutic effect of Sanxiang Shuangzhu Powder, a traditional Chinese medicine introduced at medium frequency, on infantile diarrhea, and to provide new ideas and basic clinical data for treating diarrhea from external use of traditional Chinese medicine. Methods: from 2019 to 2020, a total of 120 patients who met the inclusion criteria of this study were randomly assigned to treatment group A, control group b1 and control group b2, with 40 patients in each group. All children in all three groups received regular western medicine treatment (micro-ecological means of soft salt dehydration and oral rehydration, intravenous moderate dehydration rehydration, antibiotic infection and treatment of fever and vomiting symptoms);Treatment group A: based on the routine internal treatment of traditional Chinese medicine and western medicine with therapeutic instruments, medium-frequency pulse medicine is introduced;Control group b1: routine western medicine treatment;The control group b2: based on the routine treatment of western medicine, was treated with Sanxiang Shuangshu Powder acupuncture. The clinical effects of the three groups of children after the experiment were compared and analyzed. Results: after treatment, the actual comprehensive clinical treatment rate of treatment group was 93.3%, significantly higher than that of control group b1 (56.7%) and control group b 2 (76.7%), P < 0.05. The stool frequency of treatment group was significantly lower than that of control group B1 and control group B2, with significant difference among the three groups (P < 0.05). The total score of TCM symptoms in the treatment group was significantly lower than that in the control group. Conclusion: the implementation of Sanxiang Shuangzhu Powder is effective in the treatment of infantile diarrhea and is worthy of clinical application.展开更多
To determine the feasibility and practicability of interrupt continuous wave (CW) approach proposed for real time simulating radar intermediate frequency(IF) video signal, theoretical analysis and computer simulation...To determine the feasibility and practicability of interrupt continuous wave (CW) approach proposed for real time simulating radar intermediate frequency(IF) video signal, theoretical analysis and computer simulation were used. Phases at two linked points between the end and beginning of adjoined frames are always consistent; the bias Doppler frequency for the time delay of A/D sampling start responds to that for target acceleration. No digital phase compensation is required at continuous points, and the interrupt CW approach has apparently practical values.展开更多
A low noise, high conversion gain down-conversion mixer for WLAN 802.11a applications, which adopts the high intermediate frequency （IF） topology, is presented. The input radio frequency （RF）band, local oscillator...A low noise, high conversion gain down-conversion mixer for WLAN 802.11a applications, which adopts the high intermediate frequency （IF） topology, is presented. The input radio frequency （RF）band, local oscillator（LO）frequency band and output IF are 5.15 to 5.35, 4.15 to 4.35 and 1 GHz, respectively. Source resistive degeneration technique and pseudo-differential Gilbert topology are used to achieve high linearity, and, current bleeding technique and LC resonant loads are used to acquire a low noise figure. In addition, the mixer adopts a common-source transistor pair cross-stacked with a source follow pair（CSSF）circuit as an output buffer to enhance the mixer＇s conversion gain but not deteriorate the other performances. The mixer is implemented in 0.18 μm RF CMOS（complementary metal oxide semiconductor transistor）technology and the chip area of the mixer including all bonding pads is 580 μm×1 185 μm. The measured results show that under a 1.8 V supply, the conversion gain is 10.1 dB; the input 1 dB compression point and the input-referred third-order intercept point are-3.5 and 5.3 dBm, respectively; the single side band （SSB）noise figure （NF）is 8.65 dB, and the core current consumption is 3.8 mA.展开更多
To provide a test platform for Electronic Warfare (EW) system, it is needed to simulate the radar received Intermediate Frequency (IF) signals and radar system functions.This letter gives a description of a radar syst...To provide a test platform for Electronic Warfare (EW) system, it is needed to simulate the radar received Intermediate Frequency (IF) signals and radar system functions.This letter gives a description of a radar system simulation software developed for frequencyphase scanning three-dimensional (3-D) radar. Experimental results prove that the software could be used for system evaluation and for training purposes as an attractive alternative to real EW system.展开更多
The method of using a narrowband filter to realize matched filtering is derived.A novel method of using spectrum sampling to realize matched filtering is presented,and the method can conquer the disadvantages that the...The method of using a narrowband filter to realize matched filtering is derived.A novel method of using spectrum sampling to realize matched filtering is presented,and the method can conquer the disadvantages that the narrowband filter cannot adopt the adaptive scheduling of phased array radars and realize matched filtering for several waveforms.A novel error extraction method is proposed,which uses a time division multipath method to realize the intermediate frequency extraction.This method can save lots of space for vehicle-born radar systems,reduce the influence of amplitude and phase distortion caused by devices,and enhance the system reliability.Simulation results show that the spectrum sampling method is applicable,and the implementation of frequency spectrum sampling is elaborated.展开更多
A GPS IF signal computer simulation method is proposed in this article. The carrier Doppler frequency and the total propagation and delay time can be modeled or calculated with the input GPS satellite ephemeris file. ...A GPS IF signal computer simulation method is proposed in this article. The carrier Doppler frequency and the total propagation and delay time can be modeled or calculated with the input GPS satellite ephemeris file. The simulated GPS IF signal outputs to a text file for post-processing and analysis. The simulation signal spectrum is compared with the received real GPS IF signal spectrum, and the correctness of the simulation result is verified.展开更多
In order to improve the service life of corundum lin- ing.for induction Jitrnace, corundum dry ramming mix was prepared using brown corundum, fu.sed magnesia, and α-Al2O3 micropowder as main starting materials, mul t...In order to improve the service life of corundum lin- ing.for induction Jitrnace, corundum dry ramming mix was prepared using brown corundum, fu.sed magnesia, and α-Al2O3 micropowder as main starting materials, mul the it!fluence of α-Al2O3 micropowder additions （0, 1% , 2%, and 3%, in mass） on properties of corundum dry ramming re.ix was investigated. The results show that after heat treating at 1 600 ~C , with the in-crease of α-Al2O3 addition, the permanent change in di- mensions on heating of the specimens decreases firstly and then increases, bulk density increases, apparent po- rosity decreases, and the crushing strength declines first- Iv and then enhances; when the addition of α-Al2O3 is 2 mass% , the termanent change in dimensions on heating of the specimens i.s relatively small and the crushing .strength decrease.s to 22.8 MPa. The XRD attd SEM reults show that after .firing at 1 600 for 3 h sin, all granular magnesium aluminate spinel form. and is welldistributed, which enhances the density.展开更多
A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to eval...A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to evaluate and determine the processing capability and then construct the parallel processing array for multi-channel signals according to the restriction of operation timing. Using this method, the design of multi-channel digital receiver may be simplified. Finally, a design example was used to show how to apply this method.展开更多
Objective:To evaluate the clinical efficacy of sinew-regulating and bone-setting manipulation(SRBSM)combined with Xiaoyu Jiegu Powder(XYJGP)in treating knee osteoarthritis(KOA).Methods:Sixty patients were randomly div...Objective:To evaluate the clinical efficacy of sinew-regulating and bone-setting manipulation(SRBSM)combined with Xiaoyu Jiegu Powder(XYJGP)in treating knee osteoarthritis(KOA).Methods:Sixty patients were randomly divided into treatment group(30 cases)and control group(30 cases).The treatment group was treated with SRBSM combined with XYJGP and the control group was given intermediate frequency electrotherapy and XYJGP.Visual Analogue Scale(VAS).The Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC),Flexion range of motion of the knee joint,and surface electromyography(sEMG)were used to evaluate and compare the patients'knee function before and after treatment.The efficacy was observed with diagnosis and efficacy standards of TCM.Results:After treatment,compared with the same group before treatment,muscle fatigue and muscle tension decreased,pain was reduced,range of motion of the knee joint was increased,and motor function was improved(P<0.05).The improvement degree of the treatment group was better than that of the control group(P<0.05).The total effective rate of the treatment group was 96.6%(29/30),higher than that of the control group(80.0%),P<0.05.Conclusion:SRBSM combined with XYJGP can effectively reduce the pain of KOA patients,improve the range of motion of the joints,and improve the quality of life of the patients,and its curative effect is better than that of intermediate frequency electrotherapy combined with XYJGP.展开更多
A novel algorithm for digital audio watermarking in wavelet domain is proposed. First, an original audio signal is decomposed by discrete wavelet transform at three levels. Then, a discrete watermark is embedded into ...A novel algorithm for digital audio watermarking in wavelet domain is proposed. First, an original audio signal is decomposed by discrete wavelet transform at three levels. Then, a discrete watermark is embedded into the coefficients of its intermediate frequencies. Finally, the watermarked audio signal is obtained by wavelet reconstruction. The proposed algorithm makes good use of the multiresolution characteristics of wavelet transform. The original audio signal is not needed when detecting the watermark correlatively. Simulation results show that the algorithm is inaudible and robust to noise, filtering and resampling.展开更多
文摘For the optimization of dynamic range and bandwidth of digital intermediate frequency receiver(DIFR), main factors affecting them and their relationships are studied. Firstly, the DIFR sensitivity, bandwidth, noise factor of radio frequency (RF) analog front-end (RFAF), and processing gain of intermediate frequency(IF) sampling are analyzed. Secondly, the constraint relationship of the noise factor of RFAF, the signal-to-noise ratio of ADC and the dynamic range of DIFR are studied. The relationship between the dynamic range and the RFAF gain, and that of the extended dynamic range and the RF AGC(automatic gain control) step are educed and simulated. These results can be used as theory foundations and design references for the implementation and optimization of the large dynamic range and wideband DIFR.
基金Supported by the National Natural Science Founation of China(No.69725001)
文摘This paper proposes a novel zero Intermediate Frequency (IF) receiver for Multi-Carrier (MC) Direct-Sequence Code-Division Multiple Access (DS-CDMA) based on multicar-rier mode of cdma2000 system. The proposed receiver employs direct RF-to-baseband down-conversion, sampling at a rate equal to the bandwidth of the baseband multicarrier signal and complex-valued coefficient FIR filters. This receiver avoids the need for arrays of high Q analog bandpass filters, has a much lower sampling rate half of that of conventional receiver and offers significant savings in hardware implementation. Analytic and simulation results show that the presented receiver performs well for both the AWGN channel and Rayleigh fading channel.
基金supported by Special Scientific and Research Funds for Doctoral Specialty of Institution of Higher Learning (200800060004)National Natural Science Foundation of China (No. 51177004)by the Innovation foundation of BUAA for Ph.D Graduates
文摘In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF and phase shift time were calculated by using the TMF contact model and the large phase shift of the magnetic field at a higher frequency was conductive to the dispersion process of residual plasma. The arc velocity was higher at 800 Hz than at 400 Hz. It can be inferred that TMF will encourage arc movement at 800 Hz. Moreover, the arc movement has an impact on the arc voltage. Because of the increasing length of the arc column with a high arc velocity, the elongated arc causes the arc voltage to increase. Specifically, the volt-ampere characteristics of the vacuum arc are divided into three stages in this paper. The higher the frequency, the greater the initial rate of rise in the arc voltage and the larger the area surrounded by arc volt-ampere characteristics. The correlations between the arc voltage and the amplitude and frequency of the current are also presented.
基金supported by Special Scientific and Research Funds for Doctoral Specialty of Institution of Higher Learning of China(No.200800060004)National Natural Science Foundation of China(No.50877002)the Innovation Foundation of BUAA for Ph.D Graduates of China
文摘Arc motion and splitting of vacuum arc at intermediate frequency（400-800 Hz） were investigated under transverse magnetic field（TMF）.The experiment was performed on cup-type TMF contacts with contact diameter of 40 mm and a contact gap of 4 mm in a single-frequency circuit.With high-speed photography we characterized the arc appearance at different arc currents from 3.3 kA-rms to 10 kA-rms at intermediate frequencies.As arc current increases from3.3 kA-rms to 10 kA-rms the arc appearance changes obviously.When current value is 3.3 kArms（current frequency 400-800 Hz）,there is almost no splitting arc;when the current exceeds5 kA-rms（current frequency 400-800 Hz）,the arc rotates at a speed above 20 m/s,accompanied by an observable splitting arc.The splitting arc could be observed at different frequencies and the arc-voltage had no noises when splitting occurred.The motion direction and the velocity of arc column were studied.Finally,the formation of a split arc was discussed.
文摘In-phase/quadrature （I/Q） mismatch is a key problem in zero intermediate frequency （ZIF） receiver architectures. Although integration and careful layout can alleviate I/Q mismatch, circuit and system level calibrations are also needed due to process variations and variable operating conditions. The amplitude im- balance between I/Q channels was calibrated using a modified R-2R ladder to achieve fine linear-in-dB variable gain. A downconversion mixer working in the 2,4-GHz band was developed for a wireless local area network （WLAN） ZIF receiver using 0.25μm complementary metal-oxide semiconductor （CMOS）. The twostage mixer configuration relaxes the tradeoff between noise and linearity. Experimental results verify the fine linear-in-dB variable conversion gain of the mixer, which can also be used as part of an automatic gain control （AGC）loop.
基金National Natural Science Foundation of China(Nos.51677002,51937004)Civil Aircraft Special Research and Technology Research Project(MJ-2017-S-46)+1 种基金State Key Laboratory of Reliability and Intelligence of Electrical Equipment(No.EERIKF004)Hebei University of Technology and selected from the 1st International Symposium on Insulation and Discharge Computation for Power Equipment.
文摘In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at intermediate frequency(360-800 Hz)was conducted and the results were compared with a butt contact with the same contact diameter(41 mm)and the same material.By analyzing the arc behavior,arc voltage characteristics,arc energy,current interrupting capacity,ablation of the anode contact and condensation of the arc products at a 3 mm gap,the differences in their vacuum arc characteristics were determined.The correlations of their arc energy with the amplitude and the frequency of the current were also achieved.Analysis suggests that the ruled curved contact has strong application potentiality because of its low arc energy,low arc voltage noise and arc voltage peak,light ablation on the surface of the anode contact and high interrupting capacity.
文摘To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the intermodulation signal and intermediate frequenc y signal.Based on the frequency conversion technology,an exclusion algorithm i s proposed a nd the actual implementation of the algorithm is given.The application resu lts show that the exclusion algorithm can identify the intermodulation signal exactly and eliminate the bad influence on the frequency measurement.
文摘Objective: the purpose of this study is to study the therapeutic effect of Sanxiang Shuangzhu Powder, a traditional Chinese medicine introduced at medium frequency, on infantile diarrhea, and to provide new ideas and basic clinical data for treating diarrhea from external use of traditional Chinese medicine. Methods: from 2019 to 2020, a total of 120 patients who met the inclusion criteria of this study were randomly assigned to treatment group A, control group b1 and control group b2, with 40 patients in each group. All children in all three groups received regular western medicine treatment (micro-ecological means of soft salt dehydration and oral rehydration, intravenous moderate dehydration rehydration, antibiotic infection and treatment of fever and vomiting symptoms);Treatment group A: based on the routine internal treatment of traditional Chinese medicine and western medicine with therapeutic instruments, medium-frequency pulse medicine is introduced;Control group b1: routine western medicine treatment;The control group b2: based on the routine treatment of western medicine, was treated with Sanxiang Shuangshu Powder acupuncture. The clinical effects of the three groups of children after the experiment were compared and analyzed. Results: after treatment, the actual comprehensive clinical treatment rate of treatment group was 93.3%, significantly higher than that of control group b1 (56.7%) and control group b 2 (76.7%), P < 0.05. The stool frequency of treatment group was significantly lower than that of control group B1 and control group B2, with significant difference among the three groups (P < 0.05). The total score of TCM symptoms in the treatment group was significantly lower than that in the control group. Conclusion: the implementation of Sanxiang Shuangzhu Powder is effective in the treatment of infantile diarrhea and is worthy of clinical application.
文摘To determine the feasibility and practicability of interrupt continuous wave (CW) approach proposed for real time simulating radar intermediate frequency(IF) video signal, theoretical analysis and computer simulation were used. Phases at two linked points between the end and beginning of adjoined frames are always consistent; the bias Doppler frequency for the time delay of A/D sampling start responds to that for target acceleration. No digital phase compensation is required at continuous points, and the interrupt CW approach has apparently practical values.
基金The Science and Technology Program of Zhejiang Province (No.2008C16017)
文摘A low noise, high conversion gain down-conversion mixer for WLAN 802.11a applications, which adopts the high intermediate frequency （IF） topology, is presented. The input radio frequency （RF）band, local oscillator（LO）frequency band and output IF are 5.15 to 5.35, 4.15 to 4.35 and 1 GHz, respectively. Source resistive degeneration technique and pseudo-differential Gilbert topology are used to achieve high linearity, and, current bleeding technique and LC resonant loads are used to acquire a low noise figure. In addition, the mixer adopts a common-source transistor pair cross-stacked with a source follow pair（CSSF）circuit as an output buffer to enhance the mixer＇s conversion gain but not deteriorate the other performances. The mixer is implemented in 0.18 μm RF CMOS（complementary metal oxide semiconductor transistor）technology and the chip area of the mixer including all bonding pads is 580 μm×1 185 μm. The measured results show that under a 1.8 V supply, the conversion gain is 10.1 dB; the input 1 dB compression point and the input-referred third-order intercept point are-3.5 and 5.3 dBm, respectively; the single side band （SSB）noise figure （NF）is 8.65 dB, and the core current consumption is 3.8 mA.
文摘To provide a test platform for Electronic Warfare (EW) system, it is needed to simulate the radar received Intermediate Frequency (IF) signals and radar system functions.This letter gives a description of a radar system simulation software developed for frequencyphase scanning three-dimensional (3-D) radar. Experimental results prove that the software could be used for system evaluation and for training purposes as an attractive alternative to real EW system.
文摘The method of using a narrowband filter to realize matched filtering is derived.A novel method of using spectrum sampling to realize matched filtering is presented,and the method can conquer the disadvantages that the narrowband filter cannot adopt the adaptive scheduling of phased array radars and realize matched filtering for several waveforms.A novel error extraction method is proposed,which uses a time division multipath method to realize the intermediate frequency extraction.This method can save lots of space for vehicle-born radar systems,reduce the influence of amplitude and phase distortion caused by devices,and enhance the system reliability.Simulation results show that the spectrum sampling method is applicable,and the implementation of frequency spectrum sampling is elaborated.
基金Supported by the Research Fund (2008-2009) of State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensingthe Na-tional 863 Program of China (No2008AA12Z308)
文摘A GPS IF signal computer simulation method is proposed in this article. The carrier Doppler frequency and the total propagation and delay time can be modeled or calculated with the input GPS satellite ephemeris file. The simulated GPS IF signal outputs to a text file for post-processing and analysis. The simulation signal spectrum is compared with the received real GPS IF signal spectrum, and the correctness of the simulation result is verified.
文摘In order to improve the service life of corundum lin- ing.for induction Jitrnace, corundum dry ramming mix was prepared using brown corundum, fu.sed magnesia, and α-Al2O3 micropowder as main starting materials, mul the it!fluence of α-Al2O3 micropowder additions （0, 1% , 2%, and 3%, in mass） on properties of corundum dry ramming re.ix was investigated. The results show that after heat treating at 1 600 ~C , with the in-crease of α-Al2O3 addition, the permanent change in di- mensions on heating of the specimens decreases firstly and then increases, bulk density increases, apparent po- rosity decreases, and the crushing strength declines first- Iv and then enhances; when the addition of α-Al2O3 is 2 mass% , the termanent change in dimensions on heating of the specimens i.s relatively small and the crushing .strength decrease.s to 22.8 MPa. The XRD attd SEM reults show that after .firing at 1 600 for 3 h sin, all granular magnesium aluminate spinel form. and is welldistributed, which enhances the density.
文摘A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to evaluate and determine the processing capability and then construct the parallel processing array for multi-channel signals according to the restriction of operation timing. Using this method, the design of multi-channel digital receiver may be simplified. Finally, a design example was used to show how to apply this method.
基金Key natural fund projects of Anhui provincial department of education(No.KJ2018A0273)。
文摘Objective:To evaluate the clinical efficacy of sinew-regulating and bone-setting manipulation(SRBSM)combined with Xiaoyu Jiegu Powder(XYJGP)in treating knee osteoarthritis(KOA).Methods:Sixty patients were randomly divided into treatment group(30 cases)and control group(30 cases).The treatment group was treated with SRBSM combined with XYJGP and the control group was given intermediate frequency electrotherapy and XYJGP.Visual Analogue Scale(VAS).The Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC),Flexion range of motion of the knee joint,and surface electromyography(sEMG)were used to evaluate and compare the patients'knee function before and after treatment.The efficacy was observed with diagnosis and efficacy standards of TCM.Results:After treatment,compared with the same group before treatment,muscle fatigue and muscle tension decreased,pain was reduced,range of motion of the knee joint was increased,and motor function was improved(P<0.05).The improvement degree of the treatment group was better than that of the control group(P<0.05).The total effective rate of the treatment group was 96.6%(29/30),higher than that of the control group(80.0%),P<0.05.Conclusion:SRBSM combined with XYJGP can effectively reduce the pain of KOA patients,improve the range of motion of the joints,and improve the quality of life of the patients,and its curative effect is better than that of intermediate frequency electrotherapy combined with XYJGP.
文摘A novel algorithm for digital audio watermarking in wavelet domain is proposed. First, an original audio signal is decomposed by discrete wavelet transform at three levels. Then, a discrete watermark is embedded into the coefficients of its intermediate frequencies. Finally, the watermarked audio signal is obtained by wavelet reconstruction. The proposed algorithm makes good use of the multiresolution characteristics of wavelet transform. The original audio signal is not needed when detecting the watermark correlatively. Simulation results show that the algorithm is inaudible and robust to noise, filtering and resampling.
