Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the...Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the simultaneous realization of anti-jamming and high-precision carrier phase difference positioning becomes a dilemmatic problem.In this paper,a distortionless phase digital beamforming(DBF)algorithm with self-calibration antenna arrays is proposed,which enables to obtain distortionless carrier phase while suppressing jamming.Additionally,architecture of high precision Beidou receiver based on anti-jamming antenna arrays is proposed.Finally,the performance of the algorithm is evaluated,including antenna calibration accuracy,carrier phase distortionless accuracy,and carrier phase measurement accuracy without jamming.Meanwhile,the maximal jamming to signal ratio(JSR)and real time kinematic(RTK)positioning accuracy under wideband jamming are also investigated.The experimental results based on the real-life Beidou signals show that the proposed method has an excellent performance for precise relative positioning under jamming when compared with other anti-jamming methods.展开更多
Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.O...Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna.According to the definition of EE,the optimized objective function is formulated with the help of Lagrangian method.By using the Karush-KuhnTucker(KKT)conditions and numerical calculation,considering both the static and dynamic circuit power consumptions,an adaptive energy efficient power allocation(PA)scheme is derived.This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients.Moreover,it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly.Simulation results verify the effectiveness of the proposed scheme.展开更多
In this paper, the asymptotic sum rate of a multi-user distributed antenna system （DAS） is analyzed. To mitigate inter-user interference, minimum mean squared error （MMSE） receivers are utilized to cooperatively p...In this paper, the asymptotic sum rate of a multi-user distributed antenna system （DAS） is analyzed. To mitigate inter-user interference, minimum mean squared error （MMSE） receivers are utilized to cooperatively process received signals in the uplink. It shows that inter-user interference is efficiently mitigated and the uplink sum rate of a multi-user DAS is greatly improved by adopting MMSE receivers. For very large number of users and remote antennas, the asymptotic uplink sum rate of MMSE receivers is derived by using virtue of the random matrix theory, which can be The approximation is verified to be quite accurate by Monte Carlo simply calculated in an iterative way simulations.展开更多
This article describes a new miniaturized omni-directional antenna with quasi-self-complementary structure for wireless communication applications. A novel ground structure composed of five rectangular plates is propo...This article describes a new miniaturized omni-directional antenna with quasi-self-complementary structure for wireless communication applications. A novel ground structure composed of five rectangular plates is proposed to enhance the impedance bandwidth and reduce the antenna size. The proposed antenna is comprised of two patches surrounded by the ground structure. Two metal patches of the antenna are located on two opposite sides of the dielectric substrate. The feed patch is used to excite the radiation patch. This unique design is realized by properly choosing the suitable feed patch shape, selecting similar slot shape on the radiation patch, and tuning their dimensions. The proposed antenna with an extremely small size of 6 mm × 9 mm has an operating impedance bandwidth ranging from 4.5 to 6.1 GHz for S<sub>11</sub> < -10 dB, which also covers the two IEEE 802.11a wireless local area network bands (5.15 - 5.35 GHz and 5.725 - 5.825 GHz). In addition to be very small in size, the antenna exhibits omni-directional radiation patterns in the entire operating bandwidth and low cross polarization. The distortionless time domain performance of the antenna is confirmed by investigation of the phase response and group delay. The obtained results in both frequency and time domain show that the proposed antenna is suitable for use in wireless communication systems.展开更多
Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed...Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.展开更多
In this paper a method that combines transmit antenna selection and reduced-constellation detection in spatially correlated Multi-Input Multi-Output （MIMO） fading channels is presented. To mitigate the performance d...In this paper a method that combines transmit antenna selection and reduced-constellation detection in spatially correlated Multi-Input Multi-Output （MIMO） fading channels is presented. To mitigate the performance degradation caused by the use of antenna selection that is based on correlation among columns, an iterative receiver scheme that uses only a subset of the constellation points close to the expected symbol vahle estimated in the previous iteration is proposed. The size of the subset can adapt to the maximum correlation of the sub-matrix after the simple antenna selection. Furthermore, the error rate performance of the scheme under linear Miniinutn Mean Square Error （MMSE） or Ordered Successive Interference Cancellation （OSIC） for the first run detection and different interleaver lengths is investigated while the transnlit antenna selection is considered. The simulation results show a significant advantage both for implementation complexity and for error rate performance under a fixed data rate.展开更多
It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output(MIMO) communication systems.In this letter,a simple proof is pre...It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output(MIMO) communication systems.In this letter,a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas.The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.展开更多
One of today’s actual problems in the field of antennas is the possibility of developing a small wideband antenna,which can work without grounding.Absence of these antennas can lead to serious problems for example in...One of today’s actual problems in the field of antennas is the possibility of developing a small wideband antenna,which can work without grounding.Absence of these antennas can lead to serious problems for example in case of designing small transceivers for cellular systems.In this article we show a proposed version of these antennas.Today there do not exist theoretical investigations of connections between electromagnetic fields and currents in flat metallic plates.Therefore,the basis of this work is optimization of proposed antenna construction by simulations.展开更多
The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X ...The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X bands,were completed between 2008 and 2012.From 2013 to 2017,four high-frequency receiving systems,including Ku,K,Ka,and Q bands,were constructed and their performance was comprehensively tested.There are three main innovations.(1)A fully movable large radio telescope system with advanced performance and complete functions has been built.(2)An advanced,reliable main reflector adjustment system has been completed,overcoming gravity deformation and creating a large antenna with a main reflective surface accuracy of 0.28 mm(root mean square)for any elevation.(3)Five innovative technologies have been developed to achieve high-precision pointing in any direction within 3″.The TMRT has made a crucial contribution to the orbital measurement and positioning of China’s lunar and deep space probes.Significantly enhancing China's ability to participate in international VLBI observations and radio astronomy,this has facilitated a series of achievements in observational radio astronomical research,in areas such as VLBI,spectral lines,and pulsars.展开更多
A 2 nd transconductance subharmonic receiver for 245 GHz spectroscopy sensor applications has been proposed. The receiver consists of a 245 GHz on-chip folded dipole antenna, a CB（common base） LNA, a 2 nd transcondu...A 2 nd transconductance subharmonic receiver for 245 GHz spectroscopy sensor applications has been proposed. The receiver consists of a 245 GHz on-chip folded dipole antenna, a CB（common base） LNA, a 2 nd transconductance SHM（subharmonic mixer）, and a 120 GHz push-push VCO with 1/64 divider. The receiver is fabricated in f;/f;= 300/500 GHz SiGe:C BiCMOS technology. The receiver dissipates a low power of 288 mW.Integrated with the on-chip antenna, the receiver is measured on-chip with a conversion gain of 15 dB, a bandwidth of 15 GHz, and the chip will be utilized in PCB board design for gas spectroscopy sensor application.展开更多
Chinese Area Positioning System (CAPS) is a transmitted satellite navigation system moved by the Chinese Academy of Sciences. Three basic modes of navigation and positioning with CAPS are given, and then a comparative...Chinese Area Positioning System (CAPS) is a transmitted satellite navigation system moved by the Chinese Academy of Sciences. Three basic modes of navigation and positioning with CAPS are given, and then a comparative analysis is made in this paper. In terms of the principle that the ionospheric delay is at an inverse ratio to the frequency square, a new ionospheric-free positioning method based on a double-antenna CAPS receiver is put forward. Then the hybrid differential observations and the solving equations and algorithms for one epoch and multi epochs are deduced according to the basic principle of the method. The method may remove the global errors in signal emission, propagation, transmission and receiving (e.g., ionospheric delay, hardware delay, and clock error). So it is very convenient for the single-epoch solution and multi-epoch navigation and positioning, and may efficiently improve the precision of real time CAPS navigation. Furthermore, the method can be used not only for the geometric orbit determination of CAPS GEO and IGSO satellites and the navigation and positioning, but also for the estimation of the tropospheric zenith delay, which is useful for the study of water vapor changes in the atmosphere. Polynomials are used in this method to express the tropospheric zenith delay and CAPS satellite orbits within the limited time interval, which reduces the num- ber of unknown parameters and thus speeds the computation.展开更多
基金supported by the Key Research and Development Program of Science&Technology Department of Sichuan Province(2021YFG0155)the Technical Innovation Fund of Southwest China Institute of Electronic Technology(H21004.2).
文摘Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the simultaneous realization of anti-jamming and high-precision carrier phase difference positioning becomes a dilemmatic problem.In this paper,a distortionless phase digital beamforming(DBF)algorithm with self-calibration antenna arrays is proposed,which enables to obtain distortionless carrier phase while suppressing jamming.Additionally,architecture of high precision Beidou receiver based on anti-jamming antenna arrays is proposed.Finally,the performance of the algorithm is evaluated,including antenna calibration accuracy,carrier phase distortionless accuracy,and carrier phase measurement accuracy without jamming.Meanwhile,the maximal jamming to signal ratio(JSR)and real time kinematic(RTK)positioning accuracy under wideband jamming are also investigated.The experimental results based on the real-life Beidou signals show that the proposed method has an excellent performance for precise relative positioning under jamming when compared with other anti-jamming methods.
基金supported by the National Natural Science Foundation of China(Nos.61571225,61571224)the Fundamental Research Funds for the Central Universities+2 种基金the Research Founding of Graduate Innovation Center in NUAA (No.kfjj20160409)the Qing Lan Project of Jiangsu,Shenzhen Strategic Emerging Industry Development Funds(No.JSGG20150331160845693)the Six Talent Peaks Project in Jiangsu Province(No.DZXX-007)
文摘Energy efficiency(EE)of downlink distributed antenna system(DAS)with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account.Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna.According to the definition of EE,the optimized objective function is formulated with the help of Lagrangian method.By using the Karush-KuhnTucker(KKT)conditions and numerical calculation,considering both the static and dynamic circuit power consumptions,an adaptive energy efficient power allocation(PA)scheme is derived.This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients.Moreover,it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly.Simulation results verify the effectiveness of the proposed scheme.
文摘In this paper, the asymptotic sum rate of a multi-user distributed antenna system （DAS） is analyzed. To mitigate inter-user interference, minimum mean squared error （MMSE） receivers are utilized to cooperatively process received signals in the uplink. It shows that inter-user interference is efficiently mitigated and the uplink sum rate of a multi-user DAS is greatly improved by adopting MMSE receivers. For very large number of users and remote antennas, the asymptotic uplink sum rate of MMSE receivers is derived by using virtue of the random matrix theory, which can be The approximation is verified to be quite accurate by Monte Carlo simply calculated in an iterative way simulations.
文摘This article describes a new miniaturized omni-directional antenna with quasi-self-complementary structure for wireless communication applications. A novel ground structure composed of five rectangular plates is proposed to enhance the impedance bandwidth and reduce the antenna size. The proposed antenna is comprised of two patches surrounded by the ground structure. Two metal patches of the antenna are located on two opposite sides of the dielectric substrate. The feed patch is used to excite the radiation patch. This unique design is realized by properly choosing the suitable feed patch shape, selecting similar slot shape on the radiation patch, and tuning their dimensions. The proposed antenna with an extremely small size of 6 mm × 9 mm has an operating impedance bandwidth ranging from 4.5 to 6.1 GHz for S<sub>11</sub> < -10 dB, which also covers the two IEEE 802.11a wireless local area network bands (5.15 - 5.35 GHz and 5.725 - 5.825 GHz). In addition to be very small in size, the antenna exhibits omni-directional radiation patterns in the entire operating bandwidth and low cross polarization. The distortionless time domain performance of the antenna is confirmed by investigation of the phase response and group delay. The obtained results in both frequency and time domain show that the proposed antenna is suitable for use in wireless communication systems.
基金TheNationalNaturalScienceFoundationofChina (No .60 3 90 5 40 ) .
文摘Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.
基金Supported by the National Natural Science Foundation of China (No.60496311)China High-Tech 863 Plan (No.2006AA01Z264).
文摘In this paper a method that combines transmit antenna selection and reduced-constellation detection in spatially correlated Multi-Input Multi-Output （MIMO） fading channels is presented. To mitigate the performance degradation caused by the use of antenna selection that is based on correlation among columns, an iterative receiver scheme that uses only a subset of the constellation points close to the expected symbol vahle estimated in the previous iteration is proposed. The size of the subset can adapt to the maximum correlation of the sub-matrix after the simple antenna selection. Furthermore, the error rate performance of the scheme under linear Miniinutn Mean Square Error （MMSE） or Ordered Successive Interference Cancellation （OSIC） for the first run detection and different interleaver lengths is investigated while the transnlit antenna selection is considered. The simulation results show a significant advantage both for implementation complexity and for error rate performance under a fixed data rate.
基金National Nature Science Foundation of China(No. 60672061)
文摘It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output(MIMO) communication systems.In this letter,a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas.The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.
文摘One of today’s actual problems in the field of antennas is the possibility of developing a small wideband antenna,which can work without grounding.Absence of these antennas can lead to serious problems for example in case of designing small transceivers for cellular systems.In this article we show a proposed version of these antennas.Today there do not exist theoretical investigations of connections between electromagnetic fields and currents in flat metallic plates.Therefore,the basis of this work is optimization of proposed antenna construction by simulations.
基金supported by National Natural Science Foundation of China(12273098).
文摘The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X bands,were completed between 2008 and 2012.From 2013 to 2017,four high-frequency receiving systems,including Ku,K,Ka,and Q bands,were constructed and their performance was comprehensively tested.There are three main innovations.(1)A fully movable large radio telescope system with advanced performance and complete functions has been built.(2)An advanced,reliable main reflector adjustment system has been completed,overcoming gravity deformation and creating a large antenna with a main reflective surface accuracy of 0.28 mm(root mean square)for any elevation.(3)Five innovative technologies have been developed to achieve high-precision pointing in any direction within 3″.The TMRT has made a crucial contribution to the orbital measurement and positioning of China’s lunar and deep space probes.Significantly enhancing China's ability to participate in international VLBI observations and radio astronomy,this has facilitated a series of achievements in observational radio astronomical research,in areas such as VLBI,spectral lines,and pulsars.
基金Project supported by the Zhejiang National Natural Science Foundation of China(No.LQ17F040001)the Key Laboratory Open Project Fund of Southeast University,China(No.K201817)
文摘A 2 nd transconductance subharmonic receiver for 245 GHz spectroscopy sensor applications has been proposed. The receiver consists of a 245 GHz on-chip folded dipole antenna, a CB（common base） LNA, a 2 nd transconductance SHM（subharmonic mixer）, and a 120 GHz push-push VCO with 1/64 divider. The receiver is fabricated in f;/f;= 300/500 GHz SiGe:C BiCMOS technology. The receiver dissipates a low power of 288 mW.Integrated with the on-chip antenna, the receiver is measured on-chip with a conversion gain of 15 dB, a bandwidth of 15 GHz, and the chip will be utilized in PCB board design for gas spectroscopy sensor application.
基金Supported by the Knowledge Innovation Project of the Chinese Academy of Sci-ences (Grant No. KGCX1-21)the National Basic Research Program of China (Grant No. 2007CB815500)+2 种基金the National High Technology Research and Development Program of China (Grant No. 2006AA12z303)the National Natural Science Foun-dation of China (Grant No. 40774009)the Special Project of Taishan Scholars of Shandong Province of China (Grant No. TSXZ0502)
文摘Chinese Area Positioning System (CAPS) is a transmitted satellite navigation system moved by the Chinese Academy of Sciences. Three basic modes of navigation and positioning with CAPS are given, and then a comparative analysis is made in this paper. In terms of the principle that the ionospheric delay is at an inverse ratio to the frequency square, a new ionospheric-free positioning method based on a double-antenna CAPS receiver is put forward. Then the hybrid differential observations and the solving equations and algorithms for one epoch and multi epochs are deduced according to the basic principle of the method. The method may remove the global errors in signal emission, propagation, transmission and receiving (e.g., ionospheric delay, hardware delay, and clock error). So it is very convenient for the single-epoch solution and multi-epoch navigation and positioning, and may efficiently improve the precision of real time CAPS navigation. Furthermore, the method can be used not only for the geometric orbit determination of CAPS GEO and IGSO satellites and the navigation and positioning, but also for the estimation of the tropospheric zenith delay, which is useful for the study of water vapor changes in the atmosphere. Polynomials are used in this method to express the tropospheric zenith delay and CAPS satellite orbits within the limited time interval, which reduces the num- ber of unknown parameters and thus speeds the computation.
