Automotive ultrasonic ranging: Increasing gain may not improve detection distance
June 12, 2012 | Arun T. Vemuri | 222903580
Arun T. Vemuri of Texas Instruments focuses on the subject of automotive ultrasonic ranging and explains why increasing gain may not improve detection distance.
Page 1 of 2As ultrasonic-based distance ranging becomes more prevalent in applications such as blind spot detection, objects at distances greater than six meters (20 ft) have to be detected. The amplitude of the echo signal reflected by objects at far distances is very small. So there is a temptation to increase the amplifier gain, K, in order to detect objects at such distances. In this article, we show that increasing the amplifier gain, K, may not always result in the ability to detect objects at farther distances.
One application for advanced driver assistance systems (ADAS) in a passenger car is ultrasonic-based distance ranging. Ultrasonic sound wave time-of-flight (TOF) is used to calculate distances to objects to assist the driver in parking the car, identifying parking spots, or detecting objects in the drivers blind spot.
In ultrasonic-based ADAS, piezoelectric transducers typically are used to convert the ultrasonic waves into electrical signals. The receiver sensitivity of piezoelectric ultrasonic transducers usually is small, resulting in very small voltages. Figure 1, below, shows a typical signal chain used to process the echo voltage. (For an example of an integrated automotive ultrasonic signal conditioner for automotive park assist systems, see TIs PGA450-Q1)
Figure 1: Using ultrasonic-based echo processing to detect objects deals with noiseboth external (shown) and internal.
This echo signal, which is an AM signal, is corrupted with noise. The noise in Figure 1 is input-referred noise and is the sum of noise from external environment and from all components in the signal chain. This corrupted signal is then amplified by an amplifier with gain K. The amplified signal is digitized using an analog-to-digital converter (ADC). The digitized AM signal is bandpass-filtered.
The bandpass filter (BPF) primarily is used to improve the signals signal-to-noise ratio (SNR). The filtered signal level is compared against a threshold,
Please login to post your comment - click here
- No news
MOST POPULAR NEWS
- CEO interview: Tronics' Langlois makes moves in MEMS
- MEMS imitates logic
- EE Times' annual salary & opinion survey report
- The Filter Wizard: Just add a transistor or clipping me softly
- Europe falls in top 20 chip company ranking for 1H14
- Desktop PCB printer produces working circuit in 30 minutes
- Report: India, China show interest in Korean analog foundry
- Audi moves to 48V supply
- Rohm opens MEMS foundry operation
- How to kill an ultracapacitor
- IMEC offers analog IC design course
- French MEMS foundry preps IPO
- Cambridge Mechatronics signs up Warren East, Foxconn
- mCube forms indoor navigation subsidiary
- A new breed of analog design tools
- Flexible and Low Power Driving of Solenoid Coils
- Automated Macro-Model Extraction Using SPICE Netlist
- Dual 13A μModule Regulator with Digital Interface for Remote Monitoring & Control of Power
- Localized Haptic Feedback for Touch Controls
- Precision Industrial Systems Demand a New Level of Data Conversion Accuracy
- 14-Bit, 4-20 mA, Loop Powered, Thermocouple Temperature Measurement System Using ARM Cortex-M3
- High-Precision Sine/Cosine Interpolation