Gain bandwidth of microstrip-line-feeding waveguide aperture antenna on LTCC substrate in the millimeter-wave band

Mictostrip-feeding broadband directive antennas [1]-[3] are in highly demand for high bitrate wireless communication systems and automotive UWB radars [4]. We have developed broadband microstrip-to-waveguide transitions composed of a multi-layer substrate [5]. To apply this to the microstrip-line-feeding broadband waveguide aperture antenna, the waveguide transmission line of the transition is replaced by a waveguide with an aperture. Low profile, broad bandwidth and good connection with microwave circuits can be expected by using the antenna with a multi-layer substrate. A novel antenna was proposed to operate over broad frequency bandwidth in the millimeter-wave band [6]. Here, the bandwidth of gain is evaluated as well as the bandwidth of return loss in this work. Important geometrical parameters are indicated to control the resonant frequency and the bandwidth of gain and return loss. Loss causing degradation of gain is discussed from the simulated electromagnetic distribution.