# Integrated Module Antenna for Automotive UWB Application
## 1 Introduction  
Automotive antennas have been widely researched in various configurations and applications, such as AM/FM, GPS, DSRC, LTE, 5G and radar [1, 2, 3, 4, 5, 6, 7]. Recently, the scope has been expanded to automotive UWB, wherein various studies on V2X (vehicle-to-things) communication, smart key localization, radar, and passenger detection sensors are being conducted [8, 9, 10, 11, 12]. In particular, the wide coverage with wide beamwidth antenna is required for communication or localization application. In contrast, the antenna with relatively narrower beamwidth than communication is required for radar or passenger detection sensor applications. However, designing and utilizing individual antennas increase the complexity and cost of developing electronic components for vehicles, which is significant. To solve this problem, integrated antennas have been proposed to perform the various automotive applications. Due to the limited antenna design space of the vehicle, for instance, integrated antennas supporting two or more services (e.g., LTE, GPS, WLAN, WAVE, etc.) have been developed [13, 14, 15, 16]. In [13], substrate-type antennas and metal-type antennas using a ground surface are integrated into the shark pin antenna to support three services at the same time. An L-sleeve L-monopole antenna is proposed to support the multi band for vehicular LTE [14]. The L-shaped structure is solution to realize the compact size of the antenna in the shark-fin while maintaining the broad bandwidth. In [15], two arm structures with different dimensions are used to provide resonances at low andhigh bands of the monopole antenna with compact size in the shark-fin with compact. Four individual antennas for LTE, FM, GPS, and diversity are integrated inside the shark-fin [16]. In particular, the LTE antenna is designed as a modified form of a loop to cover two bands. Furthermore, due to functional parts, such as antenna diversity, and pattern coverage, pattern-switching or reconfigurable antennas are being developed [17; 18]. In [17], active dipole with two parasitic patches and passive dipoles are integrated into single substrate for broad bandwidth. In addition, PIN diode is applied to pattern reconfigurable purpose. An integrated Tri-band/UWB polarization diversity antenna for vehicular networks is proposed [18]. To obtain triple and ultrawideband characteristics, the UWB monopole and modified monopole structures are integrated into one substrate, and each antenna operates in individual modes using multiple PIN diodes. Considering the limited antenna design space of the vehicle, these antennas are solution of reducing the system's complexity and cost. In this paper, the integrated type antenna is proposed for automotive UWB applications. The proposed antenna is combined with UWB localization antenna and rear passenger detection sensor antenna in single UWB module substrate. For the UWB applications, the monopole and patch array is adopted for prototype antenna. Because the wide coverage is required that the antenna can receive the signal at any incident angle in horizontal plane of the vehicle for UWB localization. In contrast, the rear passenger detection sensor requires a relatively narrower beamwidth than the localization antenna for accurate detection. Then, the modified ground stubs and parasitic radiators are applied to the monopole and patch array. Because the combined antenna has a structure in which the monopole and patch array share the ground; due to limited space of the automotive UWB module, mutual influence can degrade the radiation characteristics. The modified stubs are utilized in order to control the phase difference of the current between the shared ground and the antenna. In addition, the parasitic radiators are applied to increase the aperture of the patch array without the increase of the antenna size. In evaluating the performance of the proposed antenna, simulation with CST Microwave studio [19] and measurement results are analyzed.