" RF and Microwave"related to papers

Abstract:Microstrip line and coaxial are the two common transmission lines in microwave systems. The common interconnection method between the two transmission lines at the low frequency band is direct soldering. The coaxial inner conductor is soldered on the metal strip line of the microstrip line. The outer conductor is mounted on the ground plane of the microstrip line. This connection has little effect on the transmission of microwave signals in the low frequency band. In the millimeter wave band, this connection will result in an increase loss of the millimeter-wave signal. Therefore, a millimeter-wave band microstrip coaxial transition structure is designed. This transition structure adds a transition hole structure between the microstrip line and the coaxial, which can effectively reduce the voltage standing wave ratio and insertion loss of the microstrip-to-coaxial transition structure, and improve the performance of the overall system.

Abstract:As one of the core components of the RF power system, the RF power source has a fixed frequency and low conversion efficiency, which has become a bottleneck restricting the development of the RF power system. Aiming at this problem, a design scheme for freely switching the RF power source between dual frequency operation modes is proposed. Direct Digital Synthesizer is used as the RF signal source. The MOSFTE producted by IXYS Company of Germany is used to achieve the amplification of small signals, which improves conversion efficiency and the stability of the output frequency. The method of parallel inductors reduces power loss during switching time. Switching the frequency selection network with a digital-controlled switch achieves adaptation of the system at dual frequencies. At the same time, Multisim simulation is carried out on the proposed scheme and theory. After actual testing, the RF power source can achieve dual frequency selection output of 13.56 MHz and 27.12 MHz at 300 W, and the conversion efficiency can reach 90.1%.

Abstract:A miniaturized ultra-wideband receiving front-end applyingto radio reconnaissance is designed in this paper,which converts RF signal of 0.1 GHz to 18 GHz to intermediate frequency(IF) by preselected filtering, amplifying, mixing, bandwidth filtering and gain controlling. The design scheme of the circuit is introduced first, and the key indicators are analyzed and designed. The front-end is 119 mm×61 mm×9.5 mm in size, with operating frequency of 0.1 GHz~18 GHz and typical gain of 35 dB,which can also be adjusted from 30 dB to 40 dB according to project requirements.

Abstract:In order to solve the difficulty of high density interconnection of multi-chip modules, a kind of microwave interconnection structure based on composite multi-layer printed circuit board(PCB) technology is designed.The optimized multi-layer interconnected structure is only 0.1 dB larger than the insertion loss of ideal microstrip in the 10 GHz~20 GHz, and the VSWR is 0.3. In the 30 GHz~40 GHz range, it is only 0.3 dB larger than the insertion loss of the ideal microstrip, and the VSWR is 0.4, which has good microwave characteristics. This structure has the advantages of simple design and low cost, which can solve the problem of high density interconnection of components.

Abstract:The radar scattering cross(RCS) which represents the echo strength of the target under the incidence wave is one of the most important concepts in the radar stealth. With the characteristics of small(low RCS), slow(low flight speed) and low(low flight height), the RCS of the unmanned aerial vehicle(UAV) in complex electromagnetic environments are affected by the geography, meteorology, non-cooperative radar radiation source and so on. Based upon such conditions, the RCS of the UAV in the complex electromagnetic environments and the influence of the radar echo are presented in this paper. Meanwhile, the research progress on the RCS of the UAV in the complex electromagnetic environments are introduced.

Abstract:Facing on the contradiction between the coding capacity and the tag size in the design of chipless tags, a new chipless tag structure is proposed. The tag is composed of a substrate-integrated waveguide and a complementary split ring on the surface patch. The complementary split ring contains nested inner ring and outer ring. The resonance frequency of the tag can be tuned by adjusting the opening angle of the inner and outer ring of the complementary split ring, in which the outer ring is responsible for a wide range of frequency coarse tuning, and the inner ring is used for a small range of frequency tuning. The tag operates in the frequency range of 4 GHz to 6 GHz, the size is 25 mm×15 mm, and the coding density is as high as 4.86 bit/cm2. The radar cross section curve of the tag is obtained through simulation, and the consistency with the theoretical analysis is verified. Compared with the traditional chipless tag, the structure can improve the coding capacity without increasing the size of the tag, while the substrate-integrated waveguide provides high selectivity for the tag, which keeps the tag with high spectral resolution.

Abstract:Although the uniform theory of diffraction(UTD) could be theoretically applied to arbitrarily-shaped convex objects modeled by non-uniform rational b-splines(NURBS), one of the great challenges in calculation of the UTD surface diffracted fields is the difficulty in determining the geodesic paths along which the creeping waves propagate on arbitrarily-shaped NURBS surfaces. In differential geometry, geodesic paths satisfy geodesic differential equation(GDE). Hence, in this paper, a general and efficient adaptive variable step Euler method is introduced for solving the GDE on arbitrarily-shaped NURBS surfaces. In contrast with conventional Euler method, the proposed method employs a shape factor(SF) ξ to efficiently enhance the accuracy of tracing, and extends the application of UTD for practical engineering. The validity and usefulness of the algorithm can be verified by the numerical results.

Abstract:With the rapid development of modern communication technology, there comes great demand of multi-frequency and broadband antennas of compact size. It is also urgent to solve the problem of the shortage of spectrum resources and low utilization of spectrum. In this paper, the new spectrum reuse resources of orbital angular momentum(OAM) are combined with ultra-wideband antenna technology, a kind of ultra-wideband OAM antenna is designed. The simulation results show that the working band of OAM antenna covers Ku, K and Ka multiple frequency bands, and multiple modes of OAM beam can be generated in the microwave section of the high frequency. The OAM beams of various modes have good rotation and symmetry, and the characteristics of different OAM mode beams are analyzed. Finally, it is found that the same mode OAM beam is generated at different frequency points at different frequency bands, which energy concentration is basically consistent. This indicates the feasibility and effectiveness of the OAM antenna.

Abstract:A miniaturized microstrip bandpass filter is presented. The proposed filter consists of four folded stepped-impedance resonators. As compared with its corresponding conventional uniform-impedance resonator or stepped-impedance resonator counterparts, the folded stepped-impedance resonator can save nearly 50% circuit size since it takes full advantage of its occupied circuit area. Owing to the simultaneous existence of the adjacent and nonadjacent coupling in the proposed bandpass filter, three different cross-coupling path-pairs can be established to generate three different transmission zeros, which can improve the selectivity performance and width of stopband of the proposed filter effectively. Measured results of the prototyped filter agree with its simulations quite well. Meanwhile, the prototyped filter performs roll-off speed of 100 dB/GHz, and its upper stopband can be up to 11.5 GHz with relative rejection over 33 dBc. Compared with some similar works, the prototyped filter achieves electrical-size-reduction of 23%, which can satisfy the requirements of miniaturization of microwave circuits.

Abstract:New requirements of RF test for 5G mobile communication are presented in this paper. Low test cost and small uncertainty of 5G RF indoor test methods are highlighted, which include indoor microwave far field simulation method, indoor real application scene simulation method and passive intermodulation(PIM) testing methods. This paper also emphases on key technologies including planar wave generator based on antenna array and 5G channel model.

Abstract:A 1.5 GHz~2.5 GHz analog complex correlator using “add and square” scheme was designed and implemented for passive millimeter-wave imaging applications. A digital gain and offset control scheme was adopted. The results of single frequency test show that the output amplitude variation is less than 1.5 dB, and the equivalent correlation bandwidth is 0.905 GHz. Meanwhile, the results of broadband noise measurement show that the correlator phase accuracy is better than 2.5°. At last, an experiment under low SNR environment is carried out to evaluate the influence on the signal-to-noise ratio(SNR) brought by different input power. The results show that in the range of -20~-10 dBm, SNR becomes higher as input power increases and SNR is 13 dB when input power reaches -13 dBm.

Abstract:Based on quadrature exciting and receiving technologies, a set of transmitting and receiving bird cage coil was designed and manufactured. The resonance can reach 400 MHz and imaging of atom H can also be attained on the 9.4 T imaging system. The workbench test result indicated that the bird cage coil reached a high Q value and the isolation of the two channels was 20 dB. At the same time, the sample test was conducted whose results showed that the image was of high uniformity, image SNR and clearness. Featuring simple design process and low cost, the birdcage coil has the model significance to the design and manufacturing of RF coils in ultra-high magnetic field imaging.

Abstract:In view of the requirements of multiple frequency bands working systems, such as mobile communication system and the Radio Frequency Identification(RFID) system, a new divisive growing type fractal structure is proposed. The PI type quadrilateral snowflake structure is used to going on divisive growing type fractal iterative calculation, with which implements a highly integrated equivalent composite radiation edge, and designed a divisive growing type fractal microstrip antenna. This antenna can cover the 900 MHz frequency band and 1.9 GHz frequency band of mobile communication system, 2.45 GHz frequency band of the RFID system at the same time. The return loss minimum values of three working frequency bands are all below -20 dB, and the working bandwidth of three working frequency bands are all better than 0.2 GHz. The radiation characteristics of antenna are all have high stability in three working frequency bands. This novel antenna successfully realizes the compatible of mobile communication system and the RFID system, and ready for appalling to mobile communication and remote identification and payment system.

Abstract:In this paper, a GaN wideband power amplifier is designed. A wideband power amplifier of 2~6 GHz based on CREE CGHV60040D chip model is designed, with modeling and electromagnetic field simulation of bonding wire and micro-strip,designing and optimizing load impedance matching in simulation software with the principle of optimal load matching network. The pulse signal measured results show that the broadband power amplifier module has a good performance in the wide band of 1.8~5.5 GHz, thegain is 10~13 dB, the output power is above 43 dBm, and the power added efficiency(PAE) is above 40%.

Abstract:Radio frequency(RF) and microwave makes effective supplement to other security detection methods due to its unique characteristics. This benefit brings rapid progress of research in the field of security application, and has played an important role in the field of import and export of human security, small UAV capture, border security, electronic radio frequency identification(RFID) and other occasions. In today′s more and more complex security environment, RF and microwave technology has become an indispensable part in protecting public safety.