Ah thanks, do you know from which model year that was introduced please? Mine is a 72 plate, so either a 2022 or poss a 2023 MY.
Since launch on all MQBevo vehicles with KESSY (for the UK, unsure on other markets.)
This is taken from the Self Study programme for the A3 8Y but it's applicable to the other brands.
The system measures the distance between the ignition key and the vehicle. This is done by measuring the time a signal takes to travel in the gigahertz frequency.
. The function “Open with convenience key” is only possible and permitted within a defined distance. There is no communication between the key and the vehicle outside the defined area. The technology is called RSAD UWB. This stands for Relay Station Attack Detection via Ultra Wide Band.
At Audi, RSAD modules are referred to as “control units for break-in protection”. These are control units 2 - 5 for break-in protection (J1192 - J1195). They send UWB signals. The distance between the sender and the receiver is determined using the signal travel time and stored in the ignition key.
Put simply, the system measures the time between sending the signal and receiving the response. The time measured is referred to as the time of flight (ToF). If the time measured (a few nanoseconds) is multiplied by the propagation velocity of the radio waves (almost the speed of light), the result is the distance between the vehicle and the key, correct to within a few centimetre
The onboard supply control unit J519 is the central locking system master on the Audi A3 (type 8Y) The entire control system for the central locking functions (including the RSAD control system) is located in the onboard supply control unit.
The entry and start authorisation control unit J518 communicates both with the onboard supply control unit J519 and the four control units for break-in protection J1192 - J1195 via a sub CAN.
J518 also performs the usual tasks:
> Reading in the signals from the capacitive sensors in the door handles
> Activating the entry and start authorisation aerials
> Wake function for the onboard supply control unit J519 via a discrete wire
> Activating the warning lamp for ignition and starter button K267
> Reading in the button signals from entry and start authorisation button E408
The electronics for the UWB technology are only present in the ignition key of vehicles with PR numbers 5F1, 5F4 or 5F8.
However, the UWB distance measurement is not automatically used on these vehicles in all cases. If a vehicle is simply locked with the remote control, no UWB query is made.
On vehicles with UWB distance measurement, the central locking system sends signals in the following frequency ranges:
> If the vehicle is locked or unlocked via the remote control, the key sends its signal in the UHF frequency at either 315 MHz or 433 MHz, depending on the vehicle and country.
> If the central locking system is operated using the convenience key functions, the four aerials (R137, R138, R200, R201) communicate at a frequency of 125 kHz.
> The communication between the four control units for break-in protection and the ignition key takes place in the UWB frequency at either 4 GHz or 6 GHz (frequencies depend on the country).