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This work presents a printed Ka-band dipole array antenna with wide bandwidth for millimeter-wave communication applications. The operating band of the proposed antenna ranges from 27.8–38.2 GHz exhibiting a wide bandwidth of 10.4 GHz. A balun structure is designed with interlaced U-shaped bending lines on the upper and lower metal layers to feed the dipole differentially. Parasitic trapezoidal patches are exquisitely placed adjacent to the driven dipoles for coupling, which can enhance bandwidth significantly through multiple resonances. The low-frequency radiation is mainly contributed by the resonance of the dipole, while the high-frequency radiation is affected by both the dipole and the parasitic trapezoidal patch. Due to the trapezoidal patch, the equivalent path length of the resonant current becomes shorter, thus supporting high-frequency resonance. A prototype of the proposed 1 × 2 dipole array antenna was fabricated for validation. The measured –10-dB impedance bandwidth is up to 27.8∼38.2 GHz (or 31.5%) and the realized gain is as high as 8 dBi, which is suitable for advanced millimeter-wave communication applications. [ABSTRACT FROM AUTHOR]

In this work, three designs of textile antennas, namely, a rectangular microstrip patch antenna, annular slot antenna, and planar inverted-F antenna (PIFA), operating in the 2.45 GHz WLAN band were developed for smart clothing applications. Conductive textile, a copper-plated polyester fabric, was used for fabricating antenna radiators and grounds. An insulating neoprene fabric with a thickness of 4 mm and a permittivity of 1.5 was used for preparing the substrates. The textile patch antenna achieved a maximum gain of 5.96 dBi and a bandwidth of 4.6%. The annual slot antenna showed a moderate gain and bandwidth of 2.9 dBi and 13.1%, respectively. The PIFA achieved the widest bandwidth of 31% but the smallest gain of 1.2 dBi. Furthermore, the performance deterioration of the proposed antennas under various bending conditions was analyzed to evaluate their suitability for wearable applications. Moreover, two 2 × 2 patch and slot antenna arrays were assembled to increase gain and bandwidth. The measured results proved that the developed antenna designs provide superior performance.

A 79-GHz wide-beam patch antenna and 1×8 antenna array with low cross-polarization levels are presented for automotive radar applications. A substrate-integrated-waveguide slot-coupled scheme was employed to reduce the cross-polarization level of the patch antenna. Two parasitic elements were added to the main patch to form a three-element subarray for beamwidth enhancement. The simulated E-plane half-power beamwidth (HPBW) of the patch antenna is 148°, and the cross-polarization level is 32.5 dB less than the co-polarization level at the boresight direction. For further gain enhancement, a 1×8 patch array was designed and fabricated. The measured results show that the proposed design can offer a wide HPBW of 144° and a low cross-polarization level of 28.3 dB less than the co-polarization level at 79 GHz. [ABSTRACT FROM AUTHOR]

Parallel-coupled line filters with Chebyshev pass-bands are synthesized based on the insertion-loss functions derived by converting the composite ABCD matrices of all coupled stages. With the synthesis, both the electromagnetic simulation and measurement results have accurate in-band response and bandwidth. Simultaneous equations for Chebyshev filters of order N < 9 are derived for determining geometric parameters of the coupled stages. The tradeoff between circuit bandwidth and ripple level is discussed. In experiments, three planar or quasi-planar structures, including the coupled-line with aperture in the ground plane, the three-line microstrip, and the broadside-coupled lines, are employed to realize the end stages for implementing the high coupling levels. Experimental filters of order up to nine with fractional bandwidth of 30% or 40% are fabricated and measured. The results show good agreement with predictions by the theory and simulation. Index Terms--Bandpass filters, Chebyshev response, insertion-loss function, parallel-coupled line filter, strong coupling.

Insertion loss (IL) functions are derived for synthesis of microstrip parallel-coupled line bandpass filters with maximally flat responses. The derivation is performed by successively multiplying the ABCD matrices of all coupled stages. Simultaneous equations for determining linewidth and line spacing of the coupled stages are established by total Q ([Q.sub.T]) of the filter specification and comparing the IL function with the canonical form. The results are provided for filters of order N [less than or equal to] 6. Two filters with fractional bandwidths [DELTA] = 30% are synthesized and demonstrated by simulation using a full-wave software package. In addition, two filters with [DELTA] = 40% and 50% are fabricated. Tapped line inputs are employed to these two circuits since some linewidths or gaps are beyond the fabrication resolution. The measured results show very good agreement with the theoretical responses. Index Terms--Insertion loss (IL) function, maximally flat response, parallel-coupled line filter, Q-distribution method, tapped line.

A millimeter‐wave broadband E‐plane out‐of‐phase power divider integrated with transition from a rectangular waveguide to substrate integrated waveguides (SIWs), is proposed. Two SIW cavities and two I‐shaped coupling apertures are used to achieve out‐of‐phase or differential signal division with broadband impedance matching. Owing to the symmetrical structure, a pair of differential signals with a phase difference less than 180° ± 0.1° and an amplitude imbalance less than 0.01 dB can be achieved. For measurement, a back‐to‐back test is fabricated and measured in Ka‐band by multilayer PCB fabrication process. The experimental results show that the insertion loss of a single transition is less than 0.65 dB within the 10‐dB impedance bandwidth from 26.9 to 38.6 GHz. [ABSTRACT FROM AUTHOR]