Guohua Zhai

Super High Gain Substrate Integrated Clamped-Mode Printed Log-Periodic Dipole Array Antenna

A compact, low profile, super high antenna gain, and broadband antenna, based on the printed log-periodic dipole array (PLPDA) antenna and the substrate integrated waveguide (SIW) technologies, has been proposed. It is so called substrate integrated waveguide clamped-mode printed log-periodic dipole array (SIW clamped-mode PLPDA) antenna. The arrangement of the dipole elements and feed lines in the SIW clamped-mode PLPDA antenna is designed and optimized. The proposed SIW clamped-mode PLPDA antenna was designed, fabricated, and tested, while a single SIW PLPDA antenna and a 2-element SIW PLPDA array were designed for comparison. The impedance bandwidth and the far-field radiation patterns in both E-plane and H-plane were measured. The measured results show that the performance of the SIW clamped-mode PLPDA antenna is similar to that of the 2-element SIW PLPDA array over the working frequency range 25 GHz-40 GHz, while the proposed antenna has only half the number of dipole elements and feed lines.

Enhanced Isolation of a Closely Spaced Four-Element MIMO Antenna System Using Metamaterial Mushroom

A double-layer mushroom structure is proposed to enhance the interelement isolation of a four-element antenna system, wherein four closely positioned substrate-integrated cavity-backed slot (SICBS) antenna elements are configured for multiple-input multiple-output (MIMO) applications. A wall with a double-layer mushroom structure is positioned in between the four antenna elements. An antenna prototype with a ground plane size of 0.96 λo × 0.96 λo (λo is the free space-wavelength at 2.4 GHz) demonstrates an enhanced interelement isolation of 16 dB for parallel-directed antenna element pairs, while the isolation of the orthogonally directed antenna element pairs remains unchanged over the operating bandwidth (|S11| <; -10 dB) of 2.396 -2.45 GHz. With the enhanced isolation larger than 42 dB between each antenna element pair, the envelope correlation coefficient (ECC) is lower than 0.02 across the operating bandwidth. The simulated and measured results validate the good MIMO diversity performance of the proposed antenna system.

Gain Enhancement of Printed Log-Periodic Dipole Array Antenna Using Director Cell

In this communication, several parasitic dipole elements served as director cell are added to the shorter end of the printed Log-periodic dipole array (PLPDA) antenna for the gain enhancement. This novel antenna is based on the combination of the PLPDA antenna and the quasi-Yagi antenna techniques, so called printed Log-Yagi dipole array antenna (PLYDA). The number and the distribution of the director cell are discussed and optimized. A prototype PLYDA antenna fed by half mode substrate integrated waveguide (HMSIW) is manufactured, as well as a HMSIW PLPDA antenna for comparison. The return loss and far-field radiation patterns were measured and presented in this work. The proposed PLYDA antenna exhibits gain enhancement of 0.2-2 dB in comparison with the equal size PLPDA antenna over the operating frequency range 21-40 GHz. The simulated and measured results are in good agreement, and the gain enhancement using the director cell is verified.

An Approach to 1-to-

In this paper, an approach to 1-to-2n (n = 2,3,4, ...) way microstrip balanced power divider is proposed for the first time. This approach is realized by one balanced-to-single-ended power divider, 2n-1 single-ended-to-balanced power dividers, and 2n-1 - 2 single-ended power dividers. The function of differential-mode power dividing and common-mode suppression can be ensured by the balanced-to-single-ended and single-ended-to-balanced power dividers. The advantage of this approach is that it can reduce the circuit size effectively when comparing with the approach using all the balanced-to-balanced power dividers. The analysis of the balanced-to-single-ended power divider and the single-ended-to-balanced power divider is realized by combining the standard S-parameters, the mixed-mode S-parameters, and the odd- and even-mode equivalent circuits. To verify the theoretical prediction, three prototypes (one balanced-to-single-ended power divider, one single-ended-to-balanced power divider, and one 1-to-4 way balanced power divider) are fabricated and measured. The fabricated 1-to-4 way balanced power divider with the size of 0.75λg × 2λg shows an insertion loss of 0.45 dB at 1.8 GHz, a fractional bandwidth for a 15-dB return loss of 29%, a 20-dB common-mode suppression of 74.6%, and a 20-dB differential-mode isolation (|Sdd32| and |Sdd42|) of 15.1% and 100%, respectively.

2^{n}

A uniplanar millimeter-wave broadband printed log-periodic dipole array (PLPDA) antenna fed by coplanar waveguide (CPW) is introduced. This proposed structure consists of several active dipole elements, feeding lines, parallel coupled line, and the CPW, which are etched on a single metallic layer of the substrate. The parallel coupled line can be optimized to act as a transformer between the CPW and the PLPDA antenna. Meanwhile, this transform performs the task of a balun to achieve a wideband, low cost, low loss, simple directional antenna. The uniplanar nature makes the antenna suitable to be integrated into modern printed communication circuits, especially the monolithic millimeter-wave integrated circuits (MMIC). The antenna has been carefully examined and measured to present the return loss, far-field patterns, and antenna gain.

Way Microstrip Balanced Power Divider

A novel simple approach for designing single-layer printed log-periodic dipole array (PLPDA) antenna fed by conductor-backed coplanar waveguide (CBCPW) is presented. The PLPDA antenna has the merits of wide bandwidth, low profile, and stable radiation pattern, which should be fed by the balanced line. The balanced line, created by the geometric features of the CBCPW, provides a balun with a considerably wide bandwidth with low profile, broad bandwidth, low insertion loss, and so forth. The prototype of the proposed CBCPW-fed printed log-periodic array at Ka band is designed and fabricated; the measured data are in good agreement with the simulated results.

Uniplanar Millimeter-Wave Log-Periodic Dipole Array Antenna Fed by Coplanar Waveguide

A methodology of using five discrete mushroomlike loadings to reduce the mutual coupling of a closely spaced four-element multiple-input multiple-output antenna system is presented in this paper. The occurrence of the loadings concentrates part of the near fields of the substrate integrated cavity-backed slot (SICBS) antenna element and changes the near-field distribution between each antenna elements, so that the mutual coupling between the antenna elements can be greatly reduced. The loaded four-element SICBS antenna system with an overall size of 1.2λ0 × 1.2λ0 × 0.11λ0 (λ0 is the free-space wavelength at the 2.4 GHz) realizes the mutual coupling reduction of 14 dB between the antenna elements along the diagonal lines with identical polarization, while keeping the mutual coupling of the orthogonally placed adjacent elements unchanged over the band of 2.4-2.485 GHz. With the mutual coupling lower than -35 dB between each antenna element pair, the envelope correlation coefficient is less than 0.005 across the operating bandwidth of 2.4-2.485 GHz.

Simplified Printed Log-Periodic Dipole Array Antenna Fed by CBCPW

The effects of mutual coupling on the performance of three 4×4 Ka-band antenna arrays consisting of three types of circularly polarized radiating elements are investigated when their beams scan from -30° to +30° off the boresight. The effects on active reflection coefficient (ARC) and axial ratio (AR) at the scanning beam directions are examined. It is found that to keep desired low ARC and acceptable AR of the beam scanning array, a mutual coupling level should be lower than -20 dB.

Mutual Coupling Reduction of a Closely Spaced Four-Element MIMO Antenna System Using Discrete Mushrooms

This paper presented a single mushroom-liking loading to enhance the isolation between two closely packed substrate integrated waveguide cavity-backed slot (SICBS) antennas. The mushroom inserted between two SICBS antennas blocks and concentrates part of the spaced-fields radiation from one antenna element, so that an inter-between isolation enhancement is achieved. The two-element parallel directed SICBS antennas (side-to-side) with the mushroom structure, wherein the height of mushroom is 0.04 λ0 (λ0 is the free-space wavelength at the central operating frequency), enhances the inter-between isolation by 8 dB over the operating band (|S11|<;-10 dB) of 2.375 GHz-2.415 GHz.

Effect of mutual coupling on Ka-band circularly polarized beam scanning antenna array

In this paper, the mutual coupling reduction of four-element substrate integrated cavity-backed slot (SICBS) antenna system based on two types of metamaterial mushroom structures are studied. In the first case, a double-layer mushroom wall is vertically positioned in between the SICBS antenna elements. In the second design, five double-layer mushroom cells are horizontally positioned above the SICBS antenna elements for mutual coupling suppression. The mushroom structure-loaded four-element SICBS antenna systems achieve ultra-low inter-element mutual coupling of -40 dB over the bandwidth of 2.39-2.45 GHz and 2.386-2.43 GHz (|S11|<;- 10 dB), respectively.