Millimeter wave sensor | TI Millimeter wave radar sensor
This application note covers Millimeter wave sensor basics. It mentions features of Millimeter wave radar sensor from Texas Instruments and Millimeter wave sensor manufacturers or vendors. It mentions benefits or advantages of millimeter wave sensor.
The sensor which operates on millimeter wave frequency band (30 GHz to 300 GHz) is known as millimeter wave sensor. The sensors are divided into two broad categories viz. active sensor and passive sensor. The active sensor emits its own EM waves and receives the reflected EM waves from the object under measurement. The example of active sensor is communication satellite or radar. The passive sensor simply receives EM energy in its field of view and performs measurement using the same. The example of passive sensor is remote sensing satellite or passive motion sensor. The millimeter wave radar sensor falls under active sensor category.
As shown in the figure, there are two parts in the mmwave radar sensor viz. transmitter and receiver. The transmitter part uses synthesizer module to transmit the EM signal at its operational frequency and receives the reflected echo from the object. The radar uses special type of signal called chirp signal. This reflected echo is received by the receiver antenna. This received signal is downconverted using RF mixer which is fed by appropriate LO (Local Oscillator) frequency. After the downconversion the analog IF (Intermediate frequency) signal is low pass filtered and converted to digital signal. The digital signal processing is applied to the converted received digital signal for further analysis.
The transmiter can use different types of waveforms such as pulsed, FSK (Frequency Shift Keying) , CW (Continuous Wave) and FMCW (Frequency Modulated Continuous Waveform). Texas Instruments' mmwave sensors use FMCW for its operation.
Application Note: TI Millimeter wave radar sensor
(Image courtesy: Texas Instruments Incorporated)
Texas Instruments have developed two families of mmwave sensors viz. AWR family and IWR family. AWR mmwave sensors are used for automotive where as IWR mmwave sensors are used for industrial/drones/medical applications.
• The mmwave radar sensor distance or range of the object and performs range resolution to distinguish
between two or more objects.
• It performs velocity measurement by transmitting two chirp signals separated by some time interval (Tc) and measuring phase difference between received echo of these two signals.
• It can also estimate angle of arrival (AoA) by measuring angle of the reflected signal with respect to horizontal plane.
Following are the features of Single-Chip Millimeter wave radar sensor ( IWR1642 ) from Texas Instruments (TI).
• Frequency of operation: 76 GHz to 81 GHz with 4 GHz continuous BW
• Number of channels : 4 receive channels, 2 transmit channels
• Transmit power : 12.5 dBm
• Receiver Noise figure: 15 dB (77 to 81 GHz)
• Phase Noise at 1 MHz: -93 dBc/Hz (77 to 81 GHz)
• Other peripherals : 6 ADC channels, 2 SPI channels, 3 UARTs, CAN, I2C, GPIOs, 2-lane LVDS etc.
Millimeter wave sensor Manufacturers or Vendors
Following table mentions list of Millimeter wave sensor manufacturers or vendors.
|Plextek, London, UK||Low-Cost Millimeter-Wave Radio-Frequency Sensors|
|Novelic, Veljka Dugosevica 54/B5 11000 Belgrade, Serbia||Develops Radar sensors such as Novelic Radar Chip (for 60GHz Band) or off-the-shelf radar chip (for 24GHz or 79GHz band).|
|Pulsar Process Measurement Ltd||mmwave radar sensor, which is non-contacting FMCW radar sensor for level and volume measurement|
|QuinStar Technology, Inc., CA, USA||CW and FMCW radars|
Benefits or advantages of Millimeter wave sensor
As mmwave sensor uses millimeter wave frequency, it has very short wavelength in EM spectrum.
As a result, following are the benefits or advantages of Millimeter wave sensor:
➨It has ability to penetrate various materials such as dry wall, plastic, clothes etc.
➨The mmwaves can be focused/steered using optical techniques similar to light signal.
➨The millimeter waves are highly directional with 1 degree of angular accuracy.
➨Due to large absolute BWs, mmwave sensor can distinguish two very close objects.
Refer advantages and disadvantages of millimeter wave radar >> for more information.