Introduction  

In the current era of rapid technological advancement, the tide of automotive intelligence is surging. Among them, digital keys, as a highly transformative technology, are gradually revolutionizing the usage model of traditional car keys. By leveraging advanced wireless communication technologies, digital keys enable vehicle owners to unlock and start their vehicles through mobile devices such as smartphones, significantly enhancing convenience. Among the many technologies supporting digital keys, the UWB (Ultra-Wideband) module has become a core technology in the digital key field due to its unique advantages, bringing users unprecedented safety and convenience experiences.  

Overview of UWB Technology  

1. Technical Principles  

UWB is a new type of radio frequency technology that typically operates in the frequency range of 3.1GHz to 10.6GHz. Unlike traditional radio frequency technologies, UWB does not rely on sinusoidal carrier waves for signal transmission. Instead, it transmits information by sending and receiving extremely narrow pulses on the nanosecond or even picosecond scale. Its signal bandwidth is extremely wide, far exceeding that of traditional communication technologies. For example, the signal bandwidth of traditional wireless technologies such as Bluetooth and Wi-Fi is generally within dozens of MHz, while UWB's signal bandwidth can reach hundreds of MHz or even several GHz. This wide-frequency-band characteristic allows UWB to support highly precise time-delay measurements. In terms of ranging, UWB mainly uses the Time of Flight (TOF) method and the Time Difference of Arrival (TDOA) method.  

- Time of Flight (TOF): This method measures the flight time of UWB signals from the transmitter to the receiver. Since the speed of light is known, the distance between two modules can be accurately calculated by multiplying the signal propagation time by the speed of light. For example, when the transmitter sends a UWB pulse signal, the receiver records the time when it receives the signal; the time difference between the two is the signal flight time, from which the distance can be derived.  

- Time Difference of Arrival (TDOA): This method uses the time difference of signal reception by multiple base stations to determine the position of a tag. Multiple base stations simultaneously receive UWB signals from the same tag; since the distances from the tag to different base stations vary, the signal arrival times at each base station also differ. By measuring these time differences, the position of the tag relative to the base stations can be calculated.  

2. Unique Advantages  

- High-Precision Positioning: One of UWB's greatest highlights is its ability to achieve centimeter-level positioning accuracy, which is difficult for traditional positioning technologies such as Bluetooth and Wi-Fi to match. For example, in a parking lot, a car owner using a smartphone equipped with a UWB digital key can accurately know the vehicle's location and easily find it, instead of struggling to search in a large parking lot as with traditional positioning technologies. This high-precision positioning capability in digital key applications can accurately determine the distance between the car owner and the vehicle, providing a solid guarantee for functions such as automatic unlocking and locking.  

- Strong Anti-Interference Capability: UWB signals have a wide frequency spectrum and low signal power spectral density. This enables them to maintain stable ranging performance in complex electromagnetic environments, such as those with multipath effects (where signals undergo multiple reflections and refractions during transmission, causing the receiver to receive signals from multiple different paths) or signal obstructions. In contrast, technologies like Bluetooth are prone to connection instability and signal interruptions when interfered with by other wireless signals. For example, in a complex signal environment like an underground parking lot, a UWB digital key can still operate stably, accurately communicate with the vehicle, and ensure the car owner can unlock the vehicle smoothly.  

- High Security: UWB technology employs multiple protection mechanisms in communication security, such as asymmetric encryption and random number generation. In particular, against relay attacks (where hackers hijack signals through relay devices to simulate the car owner's signals and unlock the vehicle from a distance), UWB's unique ranging and timestamp technologies make it impossible for hijacked signals to pass time validation. Traditional RFID or Bluetooth technologies are vulnerable to signal spoofing due to their weak signals, while UWB's high-precision time-measuring characteristics make it almost impossible to forge or interfere with, greatly enhancing the vehicle's anti-theft capabilities.  

- Low Power Consumption: UWB signals use short pulses to transmit data, consuming less energy in a short time, so the overall power consumption of the module is low. This makes it suitable for battery-powered devices and can extend their usage time. This is very important for digital key applications powered by mobile phone batteries, as it does not significantly shorten the phone's battery life due to frequent use of digital key functions.  

- High-Speed Data Transmission: UWB technology uses very low power and high bandwidth to enable high-speed data transmission over short distances. By sending pulses in a specific pattern, UWB encodes information, featuring low power consumption and strong anti-interference capabilities. It can realize the perception of position, distance, and direction of various smart devices, making fast and stable data interaction between vehicles and digital keys possible.  

Applications of UWB Modules in Digital Keys  

1. Workflow  

In digital key systems, Bluetooth Low Energy (BLE) and UWB technologies typically work together. When a car owner approaches the vehicle, the smartphone first establishes a connection with the vehicle via BLE. The BLE connection is used to initiate digital key communication and perform preliminary user authentication. Once the BLE connection is established, the digital key protocol exchanges messages with the vehicle via BLE. During this phase, a public-key encryption mechanism ensures the identity credibility between the vehicle and the smartphone, preventing identity forgery by hackers. Subsequently, the vehicle activates UWB communication. The smartphone or key card sends an STS signal, and the UWB anchors (sensors) around the vehicle respond in turn. Through these signals, the UWB system can accurately calculate the distance between the car owner and the vehicle.  

- When the car owner approaches the vehicle and the distance calculated by the UWB system meets the preset conditions, the vehicle automatically unlocks. For example, when the UWB digital key is within 1-3 meters (calibratable) of the vehicle, it enters the unlocking zone, the door automatically unlocks, and the turn signals flash and make a sound to welcome the car owner into the vehicle.  

- When the car owner leaves the vehicle and the UWB digital key is 4 meters (calibratable) away from the vehicle, the entire vehicle automatically locks, the turn signal on the side near the key flashes, and a sound is emitted.  

2. Application Scenarios  

- Keyless Entry and Start: The car owner does not need to take out their phone or key. When carrying a UWB digital key and approaching the vehicle, the vehicle can automatically detect and unlock the door. After entering the vehicle, the car owner can start the vehicle directly without inserting a key. For example, when a car owner walks toward the vehicle with both hands full of items, the vehicle automatically unlocks without needing to free their hands to look for the key, and starting the vehicle after getting in is smooth and natural, greatly enhancing the user experience.  

- Precision Vehicle Locating: In large parking lots, car owners can use the high-precision positioning function of UWB through an APP on their phone to quickly and accurately find their vehicle's location. The APP can precisely display the relative position of the vehicle and the car owner on a map, guiding the car owner to the vehicle smoothly and saving time spent searching for the car.  

- Personalized Settings: UWB digital keys can connect to the vehicle's internal system to achieve personalized function customization. For example, when the car owner approaches the vehicle and the vehicle automatically unlocks, the seats, rearview mirrors, etc., can automatically adjust to preset positions according to the car owner's habits, providing a personalized driving environment for the car owner.  

- Digital Key Sharing: The UWB digital keys of some vehicle models have a sharing function, allowing car owners to share digital keys with family members, friends, etc. For example, a car owner can share the digital key with family members via their phone, so family members can use the vehicle without a physical key, which is convenient and fast.