What is Remote Keyless Entry?

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- everything RF

Feb 17, 2024

A Remote Keyless Entry (RKE) is an electronic lock that controls access to a building or a vehicle using an electronic remote control. It is the upgraded version of a keyless system that uses a fob or a card to perform authorization. It is widely used in automobiles, as it serves the functions of a car key without being inserted into the lock.

RKE systems are based on unidirectional Radio Frequency Transmission from the key fob to the car (A key fob is an RF device that can generate signals and broadcast them to communicate with the vehicle). RF signals in the 315 MHz, 433 MHz, or 868 MHz (depending on the geographic location) are generated when a button on the key fob is pressed. They are received by a receiver in the car, and based on the command received, a lock or unlock operation is performed. 

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How does an RKE (Remote Keyless Entry) System work?.

An RKE System consists of three elements: a Transmitter, a Receiver, and an Antenna.

Block Diagram of a Remote Keyless System 

The Transmitter consists of an RF Transmitter Antenna, CPU, Push Button and a Coin cell to power the system. This action immediately wakes the Central Processing Unit whenever the user presses the pushbutton in a range near the car (5-20 meters). The CPU then sends a data stream to the RF Transmitter. The data stream includes a preamble, command, and rolling code. The RF Transmitter generates a radio signal based on this data and broadcasts it through an antenna. The modulation scheme is Amplitude Shift Keying (ASK), mainly to extend the key fob’s battery life.

The Receiver consists of a Power Supply Block, the RF Receiver, the CPU and a command module. The receiver captures the signals, demodulates them, and transforms the weak signals; it also filters unnecessary signals over the air that are not intended for the system where the receiver belongs. It then sends the signals to the Central Processing Unit of the Receiving module, which then decodes the data and sends the appropriate commands to the command module of the vehicle. 

Challenges of Remote Keyless Entry

  • Cost: RKE Systems are more expensive than traditional key systems, as they require installation and additional hardware. 
  • Battery Operated: RKE Systems require a battery or power source on both ends. This means if the battery runs out the keyless system will not work.
  • Technical Malfunctions: Like any other technical system, the RKE System can also malfunction; if the system malfunctions, it can prevent authorized individuals from gaining access to the vehicle.

Remote Keyless System (RKS)

The Remote Keyless System (RKS) is the mainstream locking technology used in cars today. This system has two parts: the Remote Keyless Entry (RKE) and the Remote Keyless Ignition (RKI). RKE primarily handles the functions of locking and unlocking vehicles. The RKI system handles the engine start-up. The primary advantage of this system is that with a single fob, the user can lock/unlock the car, start the engine, set the alarm system, open the trunk, etc.

What is a Passive Keyless Entry System?

A more advanced keyless technology is the Passive Keyless Entry System and the Passive Keyless Entry and Start System (PKE and PKES). The fob that is part of this system is called Smart Key. This type of system is usually found in luxury brand cars. The user needs to have the fob with him, and the car will be automatically opened when the user pulls the door’s handle. The engine can start by pushing a button on the car. This can be done because the fob constantly releases a signal to communicate with the car.