A W-band 8 × 8 slot array antenna is proposed and fabricated by electroforming for high-precision manufacturing. The external mutual coupling between radiating shunt slots is compensated for input impedance matching and a uniform field distribution. The overall antenna aperture area is 473.1 mm 2 with slot spacings of 2.8 mm and 2.64 mm in the transverse and longitudinal direction, respectively. The measured maximum gain is 26.8 dBi and the corresponding antenna efficiency is 81.9% at 94 GHz. The measured impedance bandwidth when the VSWR is less than 2.0 (-10 dB) is 8.3%, with a range from 89.9 to 97.6 GHz.Index Terms-Electroforming, high-efficiency, millimeter wave antenna, W-band, waveguide slot array antenna.

The design method for a standing-wave series slot array antenna with 45 -inclined linear polarization in the Ka-band is presented. The proposed 16 8 planar slot array antenna consisted of arrays with alternating reactance slot pairs that could achieve impedance matching and uniform field excitation, simultaneously. Furthermore, the grating lobes were effectively suppressed with the help of these radiating units due to the one-half guided wavelength slot spacing. An equivalent circuit analysis was done to evaluate the input impedances of the radiating and feeding lines with the impedance recursive formulas as well as the mode voltages of the radiating slot elements. In addition, a wideband transition with a 30.13% bandwidth under the criteria of less than VSWR 1.5:1 was presented to provide the necessary power with the minimal reflection and to prevent the distortion of the radiation patterns. The proposed planar slot array antenna occupied an aperture area of 57.4 51.6 mm. The measured bandwidth, gain, and efficiency were 990 MHz (2.88%), 24.3 dBi, and 53.7%, respectively. Furthermore, the side lobe levels (SLLs) were verified for each cutting plane with and , respectively. The proposed antenna structure was achieved with a substrate integrated waveguide (SIW) with the low costs and lightweight features.Index Terms-Alternating reactance slot pair, slot array antenna, substrate integrated waveguide (SIW) technology.

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