With connected cars gradually becoming the norm, connectivity choices in the automotive field have increased, all of which require an antenna for communicating. In upcoming automobiles, the connectivity choices include V2X (C-V2X, DSRC etc.), modems (4G-LTE, 5G), GNSS (GPS/GLOSNASS etc.), SDARS, Wi-Fi, and Bluetooth. We will be taking a brief look at the various considerations for the antennas for automotive vehicles.

Antennas can be external or internal. An example of an external antenna is the one located in the shark fin installed at the top of the vehicle. External antennas provide the benefit of better signal coverage for GPS, modems, V2X, and SDARS. A risk factor with external choices though, is the fact that they would be more susceptible to damage caused by accidents. Internal antennas on the contrary, are mounted along with the ECU/hardware. For Wi-F connectivity internal antennas would be preferred for provide hotspot networks catering to all in-vehicle users. External antennas on the other hand, would be more appropriate for Wi-Fi connectivity to existing infrastructure such as a person’s home.

Internal antennas are always collocated in the hardware box along with the radio. For external antennas, coaxial cables usually run from the radios to the antennas outside. If the distance between the radio and antenna is large, it could introduce noise in the cable’s relay. A solution to counteract this applied by the industry, is a Telematics Control Unit (TCU) that hosts all the radios and located on the roof of the car below the shark fin and is integrated with the antennas. TCUs can be interfaced digitally over a Controller Area Network (CAN), Automotive Ethernet etc.; and remote tuners for the digital radio can also be collocated near the antenna. Other locations such as the front of the roof and spoilers can also be utilized.

Another consideration to keep in mind is the issue of wireless co-existence as many of these technologies share the same bandwidth spectrum. Wi-Fi and Bluetooth share the 2.4 GHz space, Wi-Fi and V2X share the 5 GHz space, SDARS and LTE Band 40 share 2.3 GHz space. In some cases, adjacent frequencies are used like LTE Band 41 and Wi-Fi/Bluetooth. The following techniques have been used to address these interferences:

• Protocol Level
  Adaptive Frequency Hopping for Bluetooth/BLE and advertising channel frequencies selected to avoid Wi-Fi. Out of band communication between the wireless chipsets to co-ordinate and implement a co-operative co-existence scheme.
• RF and Antennas
  It would be prudent to provide proper isolation and effective filters to reduce any interference from out-of-band and harmonic signals. By taking inspiration from the mobile industry, their RFFE designs can be also be leveraged here. This will require effective simulation, proper designing, and selection.

Sasken has an extensive expertise and competencies in RF and antenna development. This includes simulation, designing, verification and tuning. We have the ability to uniquely design and tune antennas meeting the operating parameters and physical constraints of customers application needs. Our team is supported with an RF lab with high quality equipment for simulation, design, verification, antenna chambers, RF measurement and performance test tools, etc.

We have over three decades of expertise in communication technologies including the latest 5G spectrum. Sasken is also one of the two exclusive and preferred system integration partners for Qualcomm’s cellular V2X technology. We are also broadening the current generation of connected car solutions to V2X-compliant safety applications by integrating V2X in TCUs.

Learn more about our diverse and comprehensive expertise in the automotive space.

References:
https://smartrak.com/internal-vs-external-antennas/
https://www.continental-automotive.com/en-gl/Passenger-Cars/Vehicle-Networking/Connectivity-Telematics/Antenna-Electronics/Telematic-Antennas
https://car.harman.com/solutions/telematics/smart-conformal-antenna
https://www.qorvo.com/design-hub/blog/top-design-tips-for-the-automotive-rf-front-end