UWB Antenna System for Digital Key
デジタルキー向け統合UWBアンテナシステム

Background

Tokai Rika, a car key manufacturing leading company for 70 years, is offering a one-stop secure
digital key system from the server to the device.

The doors can be locked and unlocked when
the key is around the car. The engine is started
only when the key is inside.

The digital key can access a car
through NFC when the smartphonebattery is dead.

UWBunitUWB

Multiple use of UWB communications
locates a key accurately, improving safety
and convenience.

NFC for emergencies

Purpose

Cost saving by using fewer UWB units in a smartphone digital key system

OutlineExisting technology
Requires at least one conventional single-antenna UWB unit for each detection area to locate the key.
Inside area
Outside area
Single-antenna
UWB unit
Driver’s door

Back door
Locates thesmartphone

Passenger’s door

Detection areas formed by single-antenna UWB unit

Problems that can occur if area
determination is inoperable
Ex. 1: The doors can be locked fromoutside when the key is left inside.
Ex. 2: The engine can be started when
the driver is outside.

Outline

Developed technology
Our multi-antenna system consists of fewer UWB units because it detects distance and angle(locate the key).
Practical use will be in 2026 or later.
Inside area
Outside area
Multi-antenna UWBunit
Principle of multi-antenna system
Driver’s door
Multi-antenna techniqueenable the estimation ofdistance and angle

Back door
Locates thesmartphone

DistanceAngle

Passenger’s door

Detection areas formed by multi-antenna UWB unit
Patent appliedTechnology

・The multi-antenna detects incoming wave angle.
・The patented multi-antenna technology and the area determination logic improve performance.

Multi-antenna technology (three patents)
Antennas installed close to each other are deteriorated in accuracy by electromagneticbonding.
⇒ Our patented technology enables downsizing and high accuracy by preventing
electromagnetic bonding.
Each antenna has the same current distribution

Principle of angle estimation

Θ-dependent
phase difference
occursIncoming wavesθ
Wave front(same colors in the figure), showing that thecharacteristic change is prevented.

Antenna

Multi-antenna current distribution

Area determination logic (13 patents)
In a car, a wave diffusive environment, the accuracy of angle measurement is poor, causing
false area detection.
⇒ The patented technology enables the detection of proper waves, improving the accuracyof area determination.

The arrival angle of waves is calculated from the phasedifference caused by the angle.

Driver’s door

Interior
Passenger’s door

Back door

Patent applied

Specificati
ons

Ranging accuracy

Distance accuracy: ±15 cm, Angle accuracy: ±5°

Installed function

UWB & BLE transmit and receive circuit, antenna, clock device
incorporated

Conformance UWB

IEEE802.15.4z

Conformance bluetooth

Ver.5.x

CPU core

32-bit ARM Cortex M4 CPU

Memory area

512 kB Flash and 64 kB SRAM

Interface

CAN FDPower supply voltage

12 VDimensions

45 x 85 x 17 mm (target values)

Operating temperature
range-40 to +105 °C

Future use■ Area forming or ranging systems

DronesAutomatic transfer robots

Indoor navigation systems