A 874 GHz mixer block integrated spline horn and lens antenna for the ISMAR instrument

In this paper, we present the design of a 874 GHz mixer block-integrated antenna for the ISMAR Instrument. The spline horn antenna with a dielectric lens (Teflon) is used to fulfill the requirement of an on-axis Directivity exceeding 32 dBi. The well designed spline horn offers very high Gaussian Coupling, exceeding 97%. This property of spline horn further helps to achieve very rotationally symmetric beam even after the lens with very low cross-polarization (<; -30 dB) as well as low side-lobe levels (<; -28 dB). The integrated spline horn with lens has far-field Full Width at Half Maximum of 4.2±0.2° over the frequency range of 860 GHz to 890 GHz. The simulated antenna losses are less than 0.5 dB and the antenna input reflection coefficient including the circular to rectangular waveguide (WR1.2) transition is better than -20 dB.