Low power for car alarm keyless entry encryption transceiver technology
[ 2012-10-26 | The latest news | Administrator | Read the number of：5262 ]
This paper analyzes the changing means of car theft, and vehicle anti-theft technology development, highlight TI's latest car alarm solutions-DST + transceiver encryption technology and system components to be compatible with the new generation of RF identification (RFID) technology solutions - three-dimensional antenna analog front-end chip for keyless entry works.
Consumers to pursue a higher degree of safety, based on the the transceiver technology of electronic security has become the standard configuration of the motor vehicles in Europe. Immediately Europe, Canada also issued a standard anti-theft system. While in the United States, the installation of security is still a voluntary behavior, but also is becoming a promotional tool for car manufacturers. In addition, after the announcement of the recent report about the Japanese gang crime and car theft, the Japanese car manufacturer facing local products to intensify the installation of security systems.
The upcoming next-generation transceiver has a special diagnostic functions, that is able to get the history of the anti-theft system mandated by reading confidential information in the key. Authorized in the system the number of spare key, a time stamp of the learning process, as well as additional background information, will become an integral part of the safety features of the transceiver.
The special integrated circuit also provides other convenient features, such as keyless entry. This function has been discussed for some time in the automotive industry. After years of automotive safety, and RFID (radio frequency identification) technology development, and finally the antenna structure of multi-channel identification device consumes only a battery (such as key chains, credit cards). With these antenna structure connected to the analog front-end processor for low-frequency applications, the support function is basically nothing to do with the direction of the device, and tiny antenna, power consumption is greatly reduced.
The upgrading of the transceiver
Encryption transceiver for anti-theft devices on the second collection of hair, almost completely replaced the first generation of read-only transceiver. Is an example of TI's digital signature transceiver (DST), query / response technology to ensure the highest degree of safety. The third collection of hair is working the remote keyless entry function with anti-theft device transceiver functions consistency, to reduce costs.
So far can be judged from the analysis of vehicle theft, the transceiver has not been declassified signs, which confirmed that the car market has reached a very high safety standards. The focus now is how to prevent fraud related to the theft of a vehicle.
Through careful research, can be simply attributed to the the following transceiver theft means:
Copy the spare key. A dishonest drivers can be lied to lose the keys to the car dealer to ask for a new key. Assuming that the initial purchase of a car, the driver three keys through twice, he can pretend reported missing and a total of five keys. Their appearance is identical and both contain a valid transceiver. When buying a car, the system is still only accept three keys. In this way, the driver can one effective two keys to the accomplices of crime, be presented to the insurance company for another 3 to make others believe that the anti-theft system is cracked.
Some car manufacturers the commercial central database to keep track of the spare key. One of its advantages is that even if the car is stolen, you can still get the spare key and the key information of the total. This information about the total number of original and spare key. However, to maintain a central database that need high cost and data network, therefore discourage most car manufacturers. DST + TI's fourth collection of hair, it will be history and diagnostic data are dispersed storage in each of the key, making the car manufacturers to avoid the establishment and maintenance of a central database of investment.
2 Car Rental tricks. Rent a car, copying a few mechanical key, remove the original car keys in the transceiver, and stick to the electronic lock near the antenna (such as the dashboard below). Thus, the electronic lock can always detect the "effective" transceiver signal, As the vehicle distance from the mechanical key can be opened, so easily stolen in the future.
This makes the key manufacturers face challenges, they must develop a new method of car keys and transceiver assembly together, so as not to damage the key or the function will not be able to remove the transceiver.
3 A more sophisticated means of theft is also concerned with the lookup. Assumptions can have the keys within a few days or a few hours, can send query signals to the transceiver with advanced professional engineering equipment and read its response, the establishment of a database for the storage of different query response. Then, the thieves could in the car through the database for electronic anti-theft device query signal a correct response, and then fired at least one can query for the correct response signal to open the car. However, the lower the success rate of such means.
DST + provides a mutual authentication process, the agreement guarantee transceiver does not respond to any query signal. Transceiver will verify whether the request signal from authorized base station, therefore, look-up table auto theft means will have no effect.
The fourth collection of hair
Generation transceiver focused on the automotive history tracking stolen after diagnosis, to prevent the "lookup" car theft, and having a greater storage space of the item of data or a car.
Special password-protected storage area, dedicated transceiver allows vendors (such as car manufacturers) to get background information about car keys and security systems. Following characteristics:
A display of the date and time stamp of the learning process;
Step counter can not be reset, the traceability of the system to learn the car keys total number;
Car ID.
Special learning process of new car keys, car manufacturers you can get the information of the security system, the light from the car keys without having to enter the automotive safety system or the use of a central database. This makes it possible to fulfill two functions: 1. Detection of car keys on the security system is still valid, to prevent invalid keys for fraud; 2. Disable the security system to identify the key inserted into the keyhole again and tried to start the engine . This information will be encoded and stored in a dedicated "burglar byte".
More of the functions supported by the mutual authentication protocol of the transceiver. As mentioned earlier, such a security mechanism is denied access to the base station unauthorized. This technical and complex, dedicated to automotive safety key hierarchy combined to ensure that only authorized departments will be able to read confidential data.
A new generation of keyless entry system
To develop the automotive mechanical key, first to develop the keyless entry system. New generation keyless entry system differs from previous remote keyless entry system, it can automatically identify the user is close to or touch the door handle to the driver and open the lock. Radio Frequency Identification (RFID) technology can achieve such a convenience, and to ensure that the system in any case, can correctly identify the driver. Carry the identification of the driver (usually a key chain or credit card-shaped device), contains one or a plurality of RFID devices connected to the antenna. Base station antennas and antenna coupling is near (for example 50cm area) identification device magnetic energy can be achieved without battery backup function. Receiving via base station antenna in the long distance range (e.g. 200cm), the recognition means is amplified and processed data. Figure 1 is a three-dimensional antenna using TI's analog front-end (3D AFE) keyless entry system block diagram.
The magnetic field generated by the magnetic loop antenna may cause the well-known field distribution, and coupled good and totally without coupling region is formed between the antenna of the base station antenna and the identification means. No coupling region, of course does not have any data and energy transfer, the identification means of the keyless entry system in a magnetic field position is random, therefore, must take appropriate measures, to minimize the scope of such a zone.
The rotating magnetic field generated by the base station is a solution, rotating magnetic field generated by orthogonal antennas. However, this method is more complex, and also often subject to the limitations of the small space of the car antenna. Another alternative is relatively simple, i.e. a three-dimensional antenna analog front-end chip, such as the TMS37122. This chip for demodulating the signal from up to three antennas, if the antenna orthogonally placed, can be demodulated from the x, y and z are three coordinates of the data information. Thus, even if the car within the base station antenna is simple, economic type loop antennas, but also no coupling area can be minimum. Regardless of the magnetic field in the identification means in what direction, there is always an antenna able to receive a sufficiently strong signal, covering the desired operating range. In addition, an external microcontroller processing agreement, and in response to the ultra-high frequency (UHF) identity query signal received by three antennas.
Figure 2 is a block diagram of the three-dimensional antenna analog front-end chip-TMS37122. As shown, TMS37122 up with three low quality factor of the antenna circuit is connected. The three antennas can receive the low frequency signal of 125kHz to 135kHz, wherein an antenna channel (RF1) to provide modulation function. This antenna can use a frequency shift keying (FSK) technology to transmit low-frequency data, and therefore compatible with existing transceiver modulation techniques. The modulation function is commonly used in battery backup mode, when the key battery power is low, the base station through a magnetic field for the identification means to provide energy.
Triggering an internal control unit, the low frequency carrier signal is higher than a certain threshold value so as to detect the three input channel RX1, RX2 and rx3. A special agreement the combination channel RXi / select, and in a very wide range of work to ensure that performance is improved.
Internal trigger, the control unit has been monitoring the RF signal of the representative of the wake-up mode, only in the receiver to the storage, in the EEPROM of the device when the wake-up mode signal will be issued on external microcontroller wake-up signal, then the demodulated data is sent to the micro- controller. Further, the carrier clock signal is recovered can be used as the time base of the microcontroller measured, and this technique can minimize the power consumption of the standby power supply.
Keyless entry system, one of the key issues is the detection of the position of the transceivers, especially to distinguish it in the car or outside the car. The TMS37122 devices complex built-in features to provide a solution to the problem.
