Analysis of representative products of automotive ultrasonic and millimeter wave radar

Radar systems are usually related to military projects such as airplanes, but they have quickly entered the civilian field, including commercial vehicles. As part of the advanced driver assistance system (ADAS) electronics, millimeter wave (mmWave) radar systems are being integrated into new vehicles to provide a safer driving experience. A fully autonomous “self-driving” car may be years away, and ADAS features such as blind spot detection and collision avoidance can now protect the driver. Low-power, high-frequency radar detection is essential to achieve all target detection, and ultimately can create a safer driving experience.

Radar systems are usually related to military projects such as airplanes, but they have quickly entered the civilian field, including commercial vehicles. As part of the advanced driver assistance system (ADAS) electronics, millimeter wave (mmWave) radar systems are being integrated into new vehicles to provide a safer driving experience. A fully autonomous “self-driving” car may be years away, and ADAS features such as blind spot detection and collision avoidance can now protect the driver. Low-power, high-frequency radar detection is essential to achieve all target detection, and ultimately can create a safer driving experience.

Millimeter wave radar technology, lidar technology and camera are three important sensor technologies to improve ADAS functions. The frequency of automotive radar is still mainly concentrated in 24 GHz, but 77 GHz is now the technology that major manufacturers focus on. A radar integrated circuit (IC) based on frequency modulated continuous wave (FMCW) on millimeter wave frequencies is being launched. The radar can distinguish between stationary targets and moving targets, and detect multiple targets at the same time, and can even calculate the relative speed of the detected vehicle through its Doppler shift.

Under a variety of light and weather conditions during the day and night, as well as in a wide temperature range, the radar can operate with stable accuracy. The sensor fusion performed by the ADAS processor can use data from three types of sensors to create a 3D image of the detected target. The development of sensor fusion technology, especially the use of radar in two frequency ranges, is clearing the way for the generation of 4D radar-based data that can be used for the target range, angle, speed, and elevation required for future autonomous driving control.

ADAS radar receivers, transmitters and transceivers usually use silicon germanium (SiGe) or silicon (Si) BiCMOS and other high-frequency/high-speed semiconductor technologies to implement highly integrated monolithic microwave integrated circuits (MMIC). MMIC usually supports modular functions, with a separate MMIC for transmitting and receiving functions, or as a transceiver, each chip has a single or multiple transmitting and receiving channels.

Whether in 24 GHz or 77 GHz frequency, ADAS radar circuit and system designers can package the main system function modules (such as microprocessor, digital signal processing (DSP) and power supply) in the same IC to save space. The central ADAS processor performs sensor fusion by combining radar data with LiDAR and camera imaging data to create a 360-degree image.

Analysis of representative products of automotive ultrasonic and millimeter wave radar

1. ADAS-equipped vehicles rely on sensor data fusion from radar, LiDAR and camera-based systems to create a 360-degree angle. Target detection field. (Provided by Xilinx)

The MMIC of ADAS millimeter wave radar is suitable for 24 GHz and 77 GHz short-range radar (SRR), and can detect about 20 m, medium-range radar (MRR) is about 60 m, and long-range radar (LRR) is about 200 m or more. The current 24 GHz radar MMIC operates in the industrial, scientific, and medical (ISM) frequency band from 24.00 to 24.25 GHz and has been used in non-automotive industrial and medical applications, including intruder detection and heart rate detectors in warehouses.

Now, government spectrum regulators including the Federal Communications Commission (FCC) and the European Telecommunications Standards Institute (ETSI) plan to release more bandwidths around 24 GHz for ultra-wideband (UWB) radars. Compared with the current level, its target resolution The rate has increased.

As most drivers expect new cars to provide ADAS Electronic solutions to improve safety, the demand for automotive millimeter wave radar solutions is increasing. More semiconductor suppliers, including some 24 GHz ADAS radar ICs already in production, are developing radar ICs for 77 GHz (76 to 81 GHz), 5 GHz bandwidth for SRR, MRR and LRR ADAS applications.

Scanning radar solution

Automotive radar highly integrated ICs for 24 GHz ISM frequency band systems, such as Infineon’s BGT24A series of ADAS radar transceiver and receiver ICs.

Members of the BGT24A series include BGT24ATR11, which is a 24 GHz radar transceiver with one transmitting channel and one receiving channel. BGT24ATR12 has one sending channel and two receiving channels; BGT24AR2 and BGT24AR4 have two and four receiving channels respectively; BGT24AT2 has two sending channels, which can be added to any transceiver to enhance situational awareness. These ICs are packaged in VQFN (Figure 2) and can be easily mounted on the PCB.

Analysis of representative products of automotive ultrasonic and millimeter wave radar

2. The 24 GHz radar sensors of the BGT24A series are MMIC transceivers with different transmitter and receiver combinations. (Provided by Infineon Technologies)

BGT24ATR11 has a single receive and transmit channel MMIC transceiver, designed for frequencies from 24.00 to 24.25 GHz. It has passed AEC-Q100 certification and has been used in many industries and medical applications. The MMIC is based on a 0.18μm bipolar SiG process with a 200 GHz upper frequency, centered on a low-noise, 24 GHz voltage-controlled oscillator (VCO). The phase noise of the VCO is -85 dBc/Hz when offset from the carrier by 100 kHz.

The MMIC transceiver includes a switchable prescaler with 1.5 GHz and 23 kHz outputs. It also provides a 24 GHz local oscillator (LO) output signal, usually 0 dBm, to drive other functions. The transmitting part of the MMIC generates a typical power of +9 dBm to the antenna; the output power can be controlled between 3 and 9 dB.

The transmitter has the fast on/off switching function required for radar use, usually 500 ns, and controls the spurious output to -30 dBm or lower in the off mode. The homodyne receiver supports many different 24 GHz ADAS radar system configurations, with its mid-frequency (dc) ranging from dc to 10 MHz. The 24 GHz radar transceiver is provided in a compact RoHS-compliant VQFN package and consumes 500 mW of power only through a +3.3 V DC power supply.

STMicroelectronics’ STRADA431 has one transmit channel and three single-ended receiver channels. Each channel has its own variable gain amplifier (VGA). It is a 24 GHz ADAS transceiver that meets the requirements of AEC-Q100. It also focuses on low noise 24 GHz VCO construction. The typical phase noise is −75 dBc/Hz offset by 100 kHz relative to the carrier. It is packaged in 6×6mm QFN, powered by +3.3V DC power supply, and controlled by a four-pin SPI interface. MMIC has onboard power and temperature sensors, and its single-channel transceiver can provide +13 dBm differential output power at 24 GHz. It has a switchable/selectable IF filter and has a receiver conversion gain of up to 60dB.

Long-term IC supplier ADI provides 24 GHz ICs for commercial and industrial security systems, which can also be used for ADAS radars. Like many semiconductor suppliers, the company also provides evaluation boards to simplify initial testing of radar chips.

EV-TINYRAD24G radar evaluation module and EV-RADAR-MMIC2 evaluation board are equipped with ADF5901 24-GHz transmitter IC, ADF5904 24-GHz receiver IC and ADF4159 phase-locked loop (PLL) IC. The IC can work with different mmWave antennas together. The evaluation module (Figure 3) is equipped with a phased array antenna with multiple input multiple output (MIMO) configuration, which allows multiple small antenna elements in the array to form an antenna radiation pattern for transmitting and receiving functions .

Analysis of representative products of automotive ultrasonic and millimeter wave radar

3. To facilitate the evaluation, a separate 24 GHz transmitting and receiving IC is installed on the compact EV-TINYRAD24G PCB. (Provided by Analog Devices)

These highly integrated devices implement effective radar functions in a small 5×5 mm LFCSF package. For example, the ADF5901 provides dual 24 GHz radar transmission channels through an onboard power amplifier and a 24 GHz VCO. The VCO also provides LO signals for other receiver functions. The IC contains various digital circuits, such as auxiliary analog-to-digital converters (ADC), as well as temperature sensors and power control circuits for each transmit channel. A simple four-wire interface controls all on-chip registers.

Higher frequency

Since the current available ISM bandwidth of 24 GHz is currently limited to 250 MHz, many circuit and system developers find that the larger available bandwidth around 77 GHz (and the high resolution of smaller wavelengths) is attractive for ADAS radars. Many of the semiconductor processes used in 24 GHz ADAS radar chips support 77 GHz devices with similar transmitter, receiver, and transceiver architectures.

For example, STMicroelectronics manufactures its dual-band, 76 to 77 GHz and 77 to 81 GHz STRADA770M ADAS radar transceivers on SiGe BiCMOS. The miniature transceiver integrates four single-ended 50Ω receiver channels (each channel has a high-resolution ADC) and three single-ended 50Ω transmitter channels. The transmitter channel includes a chirp modulator and a chirp, and a variety of integrated functions are contained in a single wafer-level BGA package with a size of only 9×9 mm.

The STRADA770M radar transceiver includes an integrated low phase noise oscillator designed for use with a 40 or 50 MHz crystal reference. The typical phase noise is −95 dBc/Hz when offset from the 77 GHz carrier by 1 MHz. Transceivers typically provide +13 dBm transmit power in the 76 to 77 GHz range, and +10 dBm transmit power in the 77 to 81 GHz range. It can achieve a receiver conversion gain of up to 75dB and can be adjusted in a 3dB step within a range of 30dB. The densely packed IC has an on-board chirp sequencer and FMCW chirp modulator, as well as a digital slave interface that can be set to SPI or I2C operation. MMIC uses +3.3V DC single power supply.

NXP Semiconductors’ TEF8102 ADAS radar transceiver MMIC (Figure 4) is manufactured on the company’s 20nm RF CMOS process. MMIC contains three sending channels with binary control and output level stabilization functions, and four receiving channels. Each receiving channel has a dedicated 12-bit ADC. The board carrier-shaped generator achieves a typical transmit power of +12 dBm in the range of 76 to 78 GHz, and a typical transmit power of +13 dBm in the range of 78 to 81 GHz. The four receiving channels of the FMCW transceiver can provide serial output data, which benefits from the low noise of the waveform generator. When shifted by 1 MHz from any frequency from 76 to 81 GHz, the typical phase noise is −86 dBc/Hz or higher.

Analysis of representative products of automotive ultrasonic and millimeter wave radar

4. TEF8102 MMIC is a radar transceiver with three transmitting channels and four receiving channels, with a scanning range of 76 to 81 GHz. (Provided by NXP Semiconductors)

The radar transceiver supports SRR, MRR and LRR applications from 76 to 81 GHz, with chirp bandwidths of 0.5, 1.0 and 2.0 MHz/μs, respectively. It is suitable for automatic emergency braking (AEB), adaptive cruise control (ACC), front cross traffic alert (FCTA), rear cross traffic alert (RCTA), parking assist (PA) and blind spot detection (BSD). The transceiver provides 4D radar data required by ADAS vehicles.

Four TEF8102 radar transceiver MMICs can provide enough data for a complete 360-degree inspection. The device can be packaged in a 7.5×7.5 mm embedded wafer level ball grid array (eWLB) package and can be provided on a test board (TEF8102 evaluation board) to simplify system development.

Texas Instruments (TI)’s AWR1243 single-chip FMCW radar transceiver has 3 single-ended transmit channels and 4 single-ended receive channels, covering 76 to 81 GHz. The company offers two versions of the device: for the AWR1243 model, two of the three transmission channels can be operated at the same time; for the AWR1243P model, all three transmission channels can be used at the same time.

The radar MMIC is manufactured using 45nm RF CMOS process, has low power consumption, and the transceiver conforming to the AEC-Q100 standard can accommodate +3.3V and +1.8V DC power supplies. The basis of MMIC is the on-board fractional-N PLL frequency synthesizer, which can command precise chirp generation and synchronization.

When offset from the 76-77 GHz carrier by 1 MHz, the AWR1243 waveform generator exhibits a low typical phase noise of -95 dBc/Hz, and when offset from the 77-81 GHz carrier by 1 MHz, it exhibits -93 dBc/Hz . The typical transmit output power is +12 dBm, the typical receiver conversion gain is 48 dB, the control range is 24 dB, and it can be adjusted in 2 dB steps.

The 77 GHz radar transceiver is designed for use with an external 40 MHz clock source. It has a built-in temperature and power monitoring function, as well as a built-in self-calibration function across frequency and temperature. The transceiver adopts a flip-chip ball grid array (BGA) package with a size of 10.4×10.4 mm. By performing simple programming changes, the transceiver can be used in all three major automotive application types (SRR, MRR and LRR) at frequencies from 76 to 81 GHz.

Some 24 GHz FMCW radar MMIC suppliers are also developing radar MMICs for 77 GHz ADAS applications, such as Analog Devices and Infineon. For example, like its 24 GHz devices, Infineon manufactures its 77 GHz devices on SiGe process. These radar MMICs are still in trial production and are expected to be used in the company’s RASIC product line. They include the RXS816xPL transceiver with three transmit and four receive channels and the RXS8156PLA transceiver with two transmit and four receive channels. Both 77 GHz radar MMICs will be packaged in eWLB.

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