Car key enables bi-directional communications

September 15, 2015 // By Christoph Hammerschmidt
Radio keys for cars could soon look rather old: NXP has introduced a chip family that turns the key not only into a bidirectional communications device for much higher distances than today.

Mantra RF is NXP’s new chip family aiming at car key applications. Bridging several hundred metres, the devices enable car users to establish a bidirectional communications link to their vehicle. Possible functions could be reading out the battery status or tank content remotely, or they can make sure that windows are closed and doors locked. Car electronics designers can enable the key to read out specific status data that facilitate maintenance. The key can remotely start the engine and even the heating or air conditioning can be activated. BMW has already implemented a key based on NXP’s new chip: At IAA, the carmaker showcases a new key that is equipped with a small display where the user can see his vehicle’s status notifications.

NXP's new Mantra RF family gives designers a high flexibility to implement specific car key solutions. For high resolution click here .

Developed for relatively sophisticated vehicles, the Mantra family offers specific RF sensitivity and blocking properties that translate into high resistance to interference as well as interception-free reception. In addition, two circuitry design concepts have been implemented in the chips: First, the Mantra family is currently the only chip family in the automotive electronics realm with a triple receiver, enabling the device to receive on three different channels at the same time. This feature makes sure that no signals get lost, leading to high system robustness at low power consumption. Second, the new concept enables the integration of multiple receiver units into the car access module to reduce overall system costs. Examples are the RF receivers for the tyre pressure monitoring system, for car diagnosis data and vehicle management. To fend off unauthorised access attempts, the Mantra family is equipped with advanced security and authentication features.

The chip can transmit and receive on multiple radio bands between 315 and 950 MHz. Two separate RF inputs enable antenna diversity. Since the device is microcontroller-based it offers the