Browsing by Author "Chung, SJ"

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24GHz active retrodirective antenna array
(1999-10-14)
Hong, TJ
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A 24GHz active Van Atta planar antenna array proposed for increasing the vehicle radar echo in a vehicle collision avoidance system is designed and demonstrated. The antenna array contains two parallel linear sub-arrays. Each sub-array is composed of four receiving microstrip antennas, four transmitting microstrip antennas and four transistor amplifiers. At the angles of -40 degrees < theta < 40 degrees, except those very close to the specular direction (theta = 0 degrees), the measured backscattering field levels of the fabricated array have variations < 3dB and are at least 10dB higher than those of a metal plate of the same size.
A broad-beamed transponder using spatial power combining (SPC) technique
(1997)
Chen, HT
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Chung, SJ
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交大名義發表
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電信工程研究所
;
National Chiao Tung University
This paper presents a new microwave/millimeter-wave transponder using active microstrip antenna array. The array elements are arranged by using the Van Atta retrodirectivity design so that the fields radiated from all the transmitting antennas combine spatially in the wave-incidence direction, which cancel with each other in other directions. The measured returning-field pattern of the transponder is illustrated, which shows good agreement with the calculation pattern.
A distributed-feedback antenna oscillator
(2000-05-01)
Wang, SL
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Chou, YH
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, a new design of the active transmitting antenna array, called the distributed-feedback antenna oscillator, is proposed. The active array is formed by serially connecting several unit cells to a closed loop. Each unit cell contains an amplifier and a two-port antenna, with an overall insertion gain larger than 0 dB and a phase delay equal to a multiple of 360 degrees. The signal traveling on the loop is amplified and radiated in each unit cell. The radiation fields from all the antennas are then combined in free space. A four-element feedback antenna oscillator operating at 10 GHz is demonstrated by using two-port aperture-coupled microstrip antennas. Simulation results show that multiple oscillation modes with different frequencies and different radiation beams may be excited in the antenna oscillator. By experiment, it is found that each oscillation mode can be built by tuning the biases of the oscillator. The measured radiation pattern for each mode agrees very well with the predicted one. For a single-mode operation with a broadside pattern, bandstop filters of a simple geometry are designed and embedded in the oscillator to suppress the unwanted oscillation modes. Finally, the influence of the bias condition on the radiation power of the single-mode oscillator is investigated.
A dual CP slot antenna using a modified Wilkinson power divider configuration
(1998-05-01)
Tseng, WJ
;
Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A dual circularly polarized (CP) slot antenna based on a proposed equal-split Wilkinson power divider is presented, An offset-fed slot antenna, which was analyzed using the method of moments together with a mixed potential integral equation, was used to replace the lumped resistor in the divider. A dual CP slot antenna operating at S-band was designed and demonstrated experimentally. The antenna possessed a return loss bandwidth of 39.3%, an isolation bandwidth of 10% for VSWR <2, and 3-dB axial ratio bandwidth of 28%.
A new dual-band antenna for WLAN applications
(2004)
Wang, YY
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A new phase-shifterless scanning technique for a two-element active antenna array
(1999-02-01)
Chou, YH
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, a new phase-shifterless beam-scanning technique is proposed and demonstrated for a two-element active antenna array. An internal control line with an embedded amplifier is introduced in the array to provide another injection signal other than the mutual-coupling injection signal between antennas. By mixing the effects of the signals from the control Line and mutual coupling, the phase difference between antennas is adjusted by gradually changing the amplifier bias on the control line. A dynamic analysis is presented to explain the scanning mechanism. The measured results showed that, when the control-line amplifier was biased from the off state to fully on state, the radiation pattern of the array was varied smoothly from the out-of-phase mode (with 180 degrees radiation phase difference) to the in-phase mode (with 0 degrees phase difference). During the scanning process, the antenna oscillators were stably locked, with the deviation of the locked frequency lower than 0.35%.
A novel amplifying antenna array using patch-antenna couplers - Design and measurement
(2002-08-01)
Tsai, CH
;
Yang, YCA
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Chung, SJ
;
Chang, K
;
電信工程研究所
This paper proposes a novel amplifying antenna array using the patch-antenna coupler formed by placing one or two open-ended microstrip lines (coupled lines) near and along the nonradiating edge(s) of a patch antenna. An X-band five-element array with broadside 25-dB Chebyshev radiation is demonstrated. When the input signal is fed to the center element, with most of the power radiating from the antenna, part of it is tapped to the coupled lines, amplified by an FET amplifier, and fed to the next antenna element. This process is repeated after all the antenna elements are fed with suitable power. The amplitude distribution of the fields radiated from the antennas is controlled by the coupling coefficient from the patch to the coupled line, which, in turn, is governed by the coupling length and gap between the patch and line. The measured return loss of the designed five-element array is -27 dB at the center frequency of 10 GHz with 2% 10-dB bandwidth. The radiation pattern possesses a transmitting gain of 15.9 dB, a half-power beamwidth of 17degrees, and a sidelobe level of -22 dB.
A novel bi-directional amplifier with applications in active Van Atta retrodirective arrays
(2003-02-01)
Chung, SJ
;
Chen, SM
;
Lee, YC
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電信工程研究所
;
Institute of Communications Engineering
A novel two-port bi-directional amplifier, which may simultaneously amplify the waves coming from both ports, is proposed and demonstrated in this paper. Using this amplifier, a two-element active Van Atta retrodirective array is implemented and compared to a four-element passive array. The bi-directional amplifier is constructed by two identical one-port reflection-type amplifiers and a 3-dB 90degrees hybrid. The reflection-type amplifier is designed using an FET with a single-power-supply configuration. A quarter-wavelength microstrip radial stub is connected to the device's source terminal to narrow down the negative-resistance frequency range so as to avoid oscillation at undesired frequencies. The fabricated bi-directional amplifier provides the transmission gain over the frequency band from 5.76 to 6.88 GHz, with a peak value of 9.1 dB at 6.04 GHz. Printed Yagi antennas with four directors are adopted to build both the active and passive Van Atta arrays. The 3-dB back-scattering beamwidth of the active array is measured as wide as 74degrees. Finally, it is observed from the measurements that, although only half of the antenna elements are used, the active Van Atta array produces a back-scattering field level 4.5 dB,, on average, higher than the passive one does. This verifies the performance of the bi-directional amplifier.
A novel card-type transponder designed using retrodirective antenna array
(2001)
Chung, SJ
;
Chou, TC
;
Chiu, YN
;
電信工程研究所
;
Institute of Communications Engineering
A novel card-type 5.8 GHz passive transponder is designed for possible use in the Dedicated Short-Range Communication (DSRC) systems and/or the RF/ID systems. Four LHCP microstrip antennas are arranged in the transponder by using the Van Atta retrodirective design so that the transponder possesses the advantages of both a high responding signal level and a wide range of responding angles. Measurement results show that the present transponder produces a signal level 12 dB higher than a transponder with single-antenna design, while maintains the same range of the responding angles as the single-antenna one. Finally, by incorporating 8-bit test codes in the beacon (or interrogator) and in the transponder, the downlink and uplink performances of the transponder are demonstrated.
A planar Van Atta array reflector with retrodirectivity in both E-plane and H-plane
(2000-02-01)
Tseng, WJ
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Chung, SJ
;
Chang, K
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電信工程研究所
;
Institute of Communications Engineering
A planar antenna array reflector with retrodirectivity in both the E-plane and the H-plane is analyzed and demonstrated at X band. The reflector consists of six pairs of slot-coupled patch antennas arranged using the Van Atta approach. The total reflected field from the reflector is separated into three primary components; that is, the reradiation field from the patch antennas (RFPA), the scattering field from the patch antennas (SFPA), and the scattering field from the ground plane (SFGP). The first two components are calculated by using the method of moments together with a mixed potential integral equation and the last one is by the physical optics (PO) method combined with the method of equivalent currents (MEC). By tuning the microstrip-line lengths, the total reflected held contributed by the three components is designed to possess a broad-beamed pattern in both the E-plane and the H-plane. The measured patterns show good agreement with the designed ones.
A recursive finite element method (RFEM) for analysis of finite periodic structures in rectangular waveguides
(1996)
Chen, HH
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A retrodirective microstrip antenna array
(1998-12-01)
Chung, SJ
;
Chang, K
;
電信工程研究所
;
Institute of Communications Engineering
A Van Atta retrodirective reflector was designed and developed, using an aperture-coupled microstrip antenna array. This reflector possesses the advantage of reflecting high fields to the source point over a wide range of incidence angles and, owing to the low cost and comformability of the structure, is suitable for applications in intelligent vehicle highway systems (IVHS). An approximate theory associated with the reradiation and scattering principles of the reflector is presented for the purpose of understanding and designing the reflector. The utility of the retrodirective reflector was demonstrated by comparison with a plate reflector and a microstrip antenna array without a feed structure. Finally, a reflector with switches in the middle of the microstrip feed lines was investigated for possible applications in communications and remote identification.
A simple method for blocking parasitic modes in a waveguide-packaged microstrip-line circuit
(1998-12-01)
Chen, HH
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Wang, CL
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A simple structure formed by two metal patches symmetrically deposited at the two sides of the center microstrip is proposed and analyzed for blacking the higher order modes in a waveguide-packaged microstrip-line circuit. The variations (with the patch width) of the effective dielectric constants and field distributions of the modes in the packaged microstrip line with infinitely long side patches were first investigated using the two-dimensional (2-D) finite-element method (FEM) and the method of lines. The results suggested that there exists a range of patch widths at which the held distributions of the higher order modes are totally different from those of the microstrip line without side patches. The scattering of the patches as a function of the patch length and width was then studied using the three-dimensional (3-D) FEM with edge elements. It has been found that by simply choosing appropriate patch sizes, the parasitic higher order mode can be reflected without sacrificing the normal propagation of the dominant mode.
A simple method for blocking parasitic modes in a waveguide-packaged microstrip-line circuit
(1998-12-01)
Chen, HH
;
Wang, CL
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A simple structure formed by two metal patches symmetrically deposited at the two sides of the center microstrip is proposed and analyzed for blacking the higher order modes in a waveguide-packaged microstrip-line circuit. The variations (with the patch width) of the effective dielectric constants and field distributions of the modes in the packaged microstrip line with infinitely long side patches were first investigated using the two-dimensional (2-D) finite-element method (FEM) and the method of lines. The results suggested that there exists a range of patch widths at which the held distributions of the higher order modes are totally different from those of the microstrip line without side patches. The scattering of the patches as a function of the patch length and width was then studied using the three-dimensional (3-D) FEM with edge elements. It has been found that by simply choosing appropriate patch sizes, the parasitic higher order mode can be reflected without sacrificing the normal propagation of the dominant mode.
A small SiP module using LTCC 3D circuitry for dual band WLAN 802.11 a/b/g front-end solution
(2006)
Wu, MC
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
Under the IEEE 802.11a/b/g WLAN specifications, this paper presents a dual-band RF FEM (Front-End Module) on LTCC substrate comprising two diplexers, two band-pass filters and two low-pass filters as a 802.11a/b/g SiP (System-in-Package) solution. To implement, a 5GHz LNA, dual-band DPDT (Double Pole, Double Throw) switch and power detector mounted on the surface of LTCC RF module are also integrated into the proposed module where has only 5.4mm x 4.0mm x 0.9mm in size. On the side of transmitter, the insertion losses of the simulated dual-band FEM are 0.7 and 0.6dB in 2.4-2.5 and 4.9-5.9GHz frequency bands, respectively. The maximum rejection characteristic is -30dB in the second and third harmonic bands. On the side of receiver, the insertion losses are 1.7 and 1.2dB in 2.4-2.5 and 4.9-5.9GHz bands, respectively. The maximum of both the isolation and rejection characteristics is -30dB.
A three-port 180-degree antenna hybrid: Design and applications
(2001-09-01)
Chou, YH
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a novel three-port antenna structure, named 180 degrees antenna hybrid, is proposed and demonstrated. This structure is composed of a Wilkinson power divider with the isolation resistor replaced by an aperture-coupled patch antenna. The equivalent series impedance of the antenna can be adjusted to the required one by properly choosing the dimensions of the patch and the coupling aperture. When a signal is fed to the balanced port of this antenna hybrid, the power is equally split, with equal phases, to the two unbalanced ports. No power is radiated out from the antenna. In the other hand, a signal received from the antenna will be split with equal power but 180 phase difference to the two unbalanced ports. The balanced port is an isolation port. The measurement results showed good agreement with the characteristics to be designed. Three applications of this 180 degrees antenna hybrid are introduced, that is, a balanced mixer, an active transmitting antenna, and a dual-radiation-mode antenna array. The balanced mixer was constructed with diodes directly mounted on the two unbalanced ports of the antenna hybrid. The LO signal is fed from the balanced port and RF signal is received from the antenna. The active transmitting antenna was implemented with feedback configuration. The route from one of the unbalanced port to the balanced port of the antenna hybrid was used as the feedback path. A locking signal may be injected from the other unbalanced port. Finally, through a three-quarter-wavelength microstrip line, the balanced port of the antenna hybrid was connected to another aperture-coupled patch antenna to form a dual-radiation-mode antenna array. The in-phase and out-of-phase radiation patterns of this two-element array can be obtained from two unbalanced ports of the antenna hybrid, respectively.
A wireless video relay system at 28 GHz
(2001)
Hu, CH
;
Wu, HL
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Chang, CY
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Chung, SJ
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電信工程研究所
LMDS (Local Multipoint Distribution Service) system can offer subscribers variety of one-way or two-way broadband services, such as video programming distribution, high speed data transmission, and wireless local loop telephony. LMDS centered around the 28 GHz band is the fastest, most flexible and economical broadband network that can be developed today. From last year, NCTU (National Chiao Tung University) was engaged in a four-year project, co-sponsored by the Ministry of Education and National Science Council, ROC, investigating the advanced millimeter-wave circuits and systems. Part of the work is to be implemented on the LMDS system as a platform. This paper presents some of the preliminary results.
Analysis and application of a two-port aperture-coupled microstrip antenna
(1998-05-01)
Tseng, WJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A two-port aperture-coupled microstrip antenna was analyzed using the method of moments together with a mixed potential integral equation (MPIE), The antenna contains two microstrip-line ports (i.e., a feeding port and a coupling port), The field coming from one microstrip line on the circuit layer is fed into the patch through an aperture on the ground plane, Part of the field is then coupled back to a second microstrip line through another aperture on the same ground. The influences of the stub lengths, along with the positions and sizes of the apertures, on the coupling power and the resonant frequency were investigated. As an application, a feedback antenna oscillator was designed using the present structure where the antenna served not only as a radiator, but also as a feedback resonator. The oscillation was stable and with a clean spectrum at the frequency of 9.79 GHz, which was only 0.2% different from the design one. An effective isotropic radiated power (EIRP) of 39 mW was achieved. The measured cross-polarized fields were at least 15 dB lower than the copolarized ones.
Analysis of a grating metal structure with broad back-scattering field pattern for applications in vehicle collision avoidance system
(2002-01-01)
Chou, YH
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Lin, SJ
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper, grating metal structures with broad and flat back-scattering field patterns are studied for possible applications in a vehicle collision avoidance system. The two-dimensional TE scattering of a planar grating structure and a curved grating structure are analyzed at a frequency of 77 GHz. For the planar structure, the method of moment together with Floquet's theorem is used to solve the induced current and the resultant back-scattering field. Based on the results of the planar structure, the scattering field of the curved grating structure is obtained by using a perturbation method. The influence on the field pattern of the curvature as well as other structure parameters, such as the width and geometry of each period in the grating structure, is investigated.
Analysis of a partially sealed package for microstrip-line circuits
(1998-12-01)
Chen, HH
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A partially sealed package formed by two metal diaphragms with or without an absorber is proposed and analyzed for shielded microstrip-line circuits. The mode-matching method, method of lines, and finite-element method are mixed appropriately to investigate the package. For a specific analysis, an electric current filament and a microstrip-line gap are chosen to simulate, respectively, an active circuit element (CE) and a passive CE to be packaged. The suppression effect of the package on the spurious (higher order) modes and the influence on the dominant mode are fully studied by comparing the excitation and scattering characteristics of the CE's with and without the package.