Antenna Arrays and Automotive Applications Jaekwang Kwon

Contents Chapter 1. Introduction 1.1.2 Space Diversity System for FM, Digital Terrestrial TV, and RKE/TPMS Devices 1.1.3 Direct Broadcasting Satellite TV 1.2 Antenna Arrays: From Simple Configuration to Advanced Design 1.2.1 Fixed Beam Directional Arrays 1.2.2 Arrays with Simple (ON/OFF) Electronically Switchable Elements 1.2.3 Electronically Controlled Phased Antenna Arrays with Single Output Receiver 1.2.4 Adaptive Antenna Arrays

diversity systems frequency range from 65 to 108 MHz. 1.1.2 Space Diversity System for FM, Digital Terrestrial TV, and RKE/TPMS Device Antennas with two or three elements are widely used for FM broadcasting radio diversity systems frequency range from 65 to 108 MHz. Figure 1.4 demonstrates the conceptual logic of the SIMO system operation in the condition of the multipath fading propagation when the signal received by the antenna system fluctuates due to the multiple reflections from the building and moving cars.

diversity systems frequency range from 65 to 108 MHz. 1.1.2 Space Diversity System for FM, Digital Terrestrial TV, and RKE/TPMS Device Antennas with two or three elements are widely used for FM broadcasting radio diversity systems frequency range from 65 to 108 MHz. Figure 1.4a schematically demonstrates multiple propagation scenario between the radio station and the car Fig. 1.4b, according to this design, the output of the receiver detects the RF signal, and the control logic circuit (according to the specific algorithm) connects either the first or second antenna to the receiver. Figure 1.4c shows the radiation patterns of an RKE antenna located in two different car body places, and Fig. 1.4d demonstrates the combined ‘‘diversity radiation pattern’’

1.1.3 Direct Broadcasting Satellite TV Direct Broadcasting Satellite (DBS) TV steerable beam antenna arrays mounted on the car roof (Fig. 1.2c) operate in microwave Ku-band frequency range Therefore, the system needs to be equipped with a special sensor that provides minimal searching to find the satellite. The tracking process has to keep the maximum radiation antenna pattern at the angle position that corresponds to the satellite angle direction. The main component of the antenna system is a phased array. Today, low cost microstrip antenna array is an excellent candidate for the automotive satellite TV applications.

1.2 Antenna Arrays: From Simple Configuration to Advanced Design A system with fixed beam pointing is the simplest configuration of the directional antenna that provides higher (in comparison with omnidirectional design) gain and lower sidelobe level. 1.2.1 Fixed Beam Directional Arrays Figure 1.5a presents linear array with corporate (parallel) beamforming Fig. 1.5b and Fig. 1.5c shows planar 2 X 2 and 4 X 4 arrays with a parallel feeding network Figure 1.5d demonstrates a linear array with series feeding Network Fig. 1.5e relates to the planar array with combined series–parallel network design. Figure 1.5f shows examples of patch elements forming different types of polarization: linear and circular. It is necessary to note that combining the single elements into the array requires proper matching to provide minimum reflections at the array output.

1.2.2 Arrays with Simple (ON/OFF) Electronically Switchable Elements Each parasitic element is connected to a ground plane via a switch that has two states: ‘‘ON’’ when a corresponding parasitic element is connected to the ground or ‘‘OFF’’ when element is not active (disconnected from the ground). Reconfiguration of the radiation pattern shape is provided by connecting a few parasitic elements to the ground using pin-diode switches with a switching time of a few nanoseconds. Depending on which of the N inputs is accessed, the antenna beam is steered in a specific direction in one plane. But still easier to implement than phased arrays with electronically controlled phase shifters and sophisticated adaptive arrays.

1.2.3 Electronically Controlled Phased Antenna Arrays with Single Output Receiver Figure 1.7a presents popular block diagram of feeding network with electronically controlled phased shifters Figure 1.7b demonstrates prototype example of four element array with two-bit digital pin-diode phase Shifters The space fed array shown in Fig. 1.7c consists of feed antenna, for example, horn, array elements, phase control block, and computer. Illuminated waves pass through the antenna element channels, undergo a phase shift, and radiate into space by the antenna elements represented by the v-shaped symbols on the right of the array (Fig.1.7d). (The reverse occurs for the energy reception) A similar array with a few feedings elements shown in Fig. 1.7d, provides multibeam mode operation or switch regime if the single receiver is connected with one of the feeding elements. Beamforming networks with the electronically controllable elements are shown in Fig. 1.7a–d

1.2.4 Adaptive Antenna Arrays In other words, weight coefficients change the reception pattern dynamically to adjust to variations in channel noise and interference in order to improve the SNR of a desired signal. As the user moves, the beam patterns are continuously updated, adapted to the maximum signals toward the desired sources, forming nulls in the directions of the interference signals. (It is seen that each pattern has nulls in the direction of the other user) Adaptive systems can be designed as analog devices or with a digital beamforming processor, as shown in Fig. 1.8c. Each antenna element has a receiver and analog to digital convertor (ADC). Digitized signals are processed in a digital beamformer (DBF) to create a digital radiation pattern that provides required parameters. These antennas provide the best performances in multipath propagation conditions; however, they are complicated structures, and demand special hardware to regulate amplitude and phase at each array element.

Thank you for your attention