Radar Level Gauge

 

Radar level gauge is an effective tool for non-contacting measurement of the level of liquid or solid in a large-scale tank. To test radar level gauge for measuring the exact distance from radar to surface level in a tank, we use SDR-KIT 980B and 2500B with FMCW signal waveform for short-distance measurement.  The beat frequency, i.e., the frequency difference between the transmitted and the received FMCW signals, is directly proportional to the distance to be measured. By accurately measuring the beat frequency using digital signal processing, the distance can be measured precisely and accurately.

 

level gauge 1

 

The experimental system diagram using SDR-RF 2500B module and SDR-PM 402 processor module, and output/display as shown below. A reflective metal plate was mounted on an adjustable precise positioning table. The distance between the radar and the metal plate is 0.828 m. After precisely adjusting the position of the metal plate by 1 mm stepping, the range reading showing in the GUI did reflect the 1 mm steps.  The test verified that with a 250 MHz signal bandwidth, the 0.6 m range resolution/precision can be improved to more than 1,000 times and a precision of <1.0 mm can be achieved.

 

level gauge 2

level gauge 3

Monitoring Human Heartbeat and Respiration

 

SDR-KIT 580B, 980B, and 2500B can be used for non-contacting monitoring specific biometric modulations, such as heart beat, respiration, arm and leg movements or other biometric patterns induced by human body’s micro movements.  One application is to monitor human sleep pattern for diagnosis of obstructive sleep apnea syndrome (OSAS) or detection of sudden infant death syndrome (SIDS) during sleep.  OSA is a common, widely underdiagnosed condition associated with significant morbidity and mortality. Due to intermittent anatomical blockage of the upper airway, reduction or even cessation of airflow occurs during sleeping, resulting in recurrent oxygen desaturation and sleep fragmentation.

Due to the weakness of biometric modulated signals by heart beats and breathing, any environmental clutter, multipath propagation, undesired direct coupling effect from transmitted energy, system flicker noise, and other causes can overwhelm the biometric signals. Thus, after data recording, effective digital signal processing algorithms for extracting informative biometric signals and estimating physiological parameters must be used.  The respiration and heartbeat signals are extracted separately. 

 

human respiration 1

 

We tested the extraction of human respiration pattern and heartbeat pattern using SDR-KIT 980B centered at 9.8 GHz with 400 MHz bandwidth as below:

 

The respiration pattern and heartbeat pattern are extracted from the respiration processor and the heartbeat processor separately. The extracted respiration pattern shows the respiration period of 2-3 sec and the heartbeat period of around 1 sec.

Environmental Monitoring

 

In this trial, the SDR-KIT 580B operating in FMCW mode was used to monitor the environment, such as surrounding vehicles, pedestrians, and even animals. The antenna was at approximately 4-meter height above the ground monitoring a gas station where vehicles or persons are in and out frequently.

 

Traffic Monitoring

 

In this trial, the SDR-KIT 580B operating in FMCW mode was used to monitor traffic. The antenna was at approximately 8-meter height watching a four-lane road (two lanes heading east and two lanes heading west) with sidewalk on both sides. The antenna is aimed perpendicular to the road to discern vehicles in different lanes.

 

TrackingTraffic

Tracking walking person

 

In this trial, the SDR-KIT 580B was used to track walking persons.  FMCW waveforms allow to measure distances of moving or static objects. A person was walking back and forth inside a room.  The waterfall display in Figure (b) shows walking track of the person. The strong vertical stripes are caused by the returns from the wall.  If the option of background subtraction in the SDR GUI is selected, the wall will be subtracted as shown in the figure below.

 

Two People Walking

 

In this trial, the SDR-KIT 580B was used to track walking person. Two persons were walking in opposite directions. An option of the DC subtraction function in the SDR GUI was enabled.  The Range-velocity map shows two hotspots walking towards opposite directions.

 

TwoPersonWalking

Tracking of Vehicle

 

In this trial, the SDR-KIT 620B was used to track the vehicle. The antenna was mounted at approximately 4 meter height above ground. FMCW modes was used to generate a range-velocity map.  Figure (a) is a snapshot of a moving car towards the line-of-sight and is registered at a range of around 19 meter with a velocity of -4 m/s. Figure (b) is the range-velocity map of the vehicle.

 

TrackingVehicle

 

 

Vehicle Speed

 

In this trial, the SDR-KIT 620B working in CW mode was used to track the speed of the vehicle. A car was running towards the antenna at a speed of about 30 mile per hour (13.4m/s) as shown in the figure (a).  A snapshot of the measured velocity plot from the SDR-GUI is shown in the figure (b). The detected speed was 13.4 m/s, which very well matches to the reading from the speedometer of the car.

 

TrackingSpeed

Image of a Vehicle

 

In this trial, the SDR kit 620B was used for imaging a walking person crossing a parking lot. The experiment was setup as shown in figure (a), where the SDR-KIT is located at 4-meter height above the ground. Figure (b) is range-Doppler image of the walking person showing in its range and cross-range. The torso and swinging foots can be seen.

 

TrackingSpeed

 

 

Image of Person Walking

 

In this trial, the SDR-KIT 620B working in CW mode was used to track the speed of the vehicle. A car was running towards the antenna at a speed of about 30 mile per hour (13.4m/s) as shown in the figure (a).  A snapshot of the measured velocity plot from the SDR-GUI is shown in the figure (b). The detected speed was 13.4 m/s, which very well matches to the reading from the speedometer of the car.

 

ISARImageOfWalkingMan

 

Radar Micro-Doppler Signatures

 

Radar micro-Doppler signatures can be used to identify human activities, such as walking, running or jumping, to monitor and predict human behaviors, and to detect a person at a distance.  Human gait analysis is useful in biomedical engineering, sports medicine, physiotherapy, medical diagnosis, and rehabilitation.  Compared with the visual perception of the human body motion, the radar micro-Doppler method is not affected by distance, variations in lighting, deformations of clothing, and occlusions on the appearance of human body segments.

 

In the micro-Doppler signature of a walking human, each forward leg swing appears as large peaks, and the left and right leg-swing completes one gait cycle.  The body torso motion that is the stronger component underneath the leg swings tends to have a slightly saw-tooth shape because the body speeds up and slows down during the swing as shown. It is possible to classify and identify bodies and their movements based on radar micro-Doppler signatures for human gaiting.

 

The SDR-KIT 980B can be used as a micro-Doppler radar.  The micro-Doppler radar using FMCW waveforms can provide more than 10 dB SNR on a 1 square meter RCS at a distance up to 50 meters.

 

RADAR MICRO-DOPPLER SIGNATURES OF A WALKING PERSON 

 

In this trial, the SDR-KIT 980B with 400 MHz bandwidth was used to capture an approaching walking person starting at a distance about 10 m.

 

MicroDopplerOfWalkingMan

 

 

RADAR MICRO-DOPPLER SIGNATURES OF A RUNNING PERSON

 

In this trial, the SDR-KIT 980B with 400 MHz bandwidth was used to capture an approaching running person starting at a distance about 10 m.

 

MicroDopplerOfRunningMan

 

 
RADAR MICRO-DOPPLER SIGNATURES OF MODEL HELICOPTER 

 

In this trial, the SDR-KIT 980B with 400 MHz bandwidth was used to capture a model helicopter with rotating rotor blades at a distance less than 10 m.

 

MicroDopplerOfHelicopter

 

 
RADAR MICRO-DOPPLER SIGNATURES OF A QUADCOPTER

 

In this trial, the SDR-KIT 2400AD2 with 500 MHz bandwidth was used to measure both radial and angular velocity of a drone quadcopter with rotating rotor blades at a distance less than 0.7 m and a 90-degree radar depression angle. Antennas spacing was set at 5λ.

 

drone-experiment