What is the accelerometer?
An electromechanical device that measures acceleration.
- Static: Constant force of gravity by measuring amount of static acceleration due to gravity to find out the angle the device is tilted at with respect to earth
- Dynamic: Caused by movement of the accelerometer by sensing the amount of dynamic acceleration.
What is capacitive accelerometer?
If there are two microstructures next to each other, they have a certain capacitance between them. If an accelerative force moves one of the structures, then the capacitance will change; adding some circuitry to convert from capacitance to voltage makes an accelerometer.
What is MEMS Capacitive Accelerometer?
Micro-machined Electro-Mechanical Systems
C = e_re_o(A/d)
- Have two immovable plates between movable plates to detect smaller acceleration
What are the common types of accelerometers?
- Capacitive
- Piezoelectric
- Piezoresistive
- Hall effect
- Magnetoresistive
Accuracy cost comparison of the types of accelerometers.
Capacitive acceleration sensor has high accuracy and decently low cost.
What is a Gyroscope?
It measures rotational velocity in 3 dimensions: pitch, roll, yaw
- Gyroscope and accelerometer provides 6 degree of freedom motion tracking system
What is a vibrating structure gyroscope?
Coriolis force is proportional to both angular velocity of rotating object and velocity of the object moving towards or away from the axis of rotation.
Coriolis force is felt by the object along the y-axis.
What is the magnetometer/compass?
Measures the strength of earth’s magnetic field and vector points towards the magnetic center of earth - uses hall effect
What is sensor fusion for motion detection?
- Primarily uses Enhanced Kalman filter
- Relies on input from multiple sensors for better sensor calibration, noise compensation, etc.
What are the two types of infrared sensors?
Proximity sensors and ranging sensors.
What is proximity sensors?
Can only detect when an object is within a predetermined range.
What is ranging sensors?
- Provide an analog output or a multiple bit output
- Ranging sensors can determine the actual distance of an object from the sensors
- The triangulation technique uses focused beam emitter and separate receiver array to measure angle.
What are the applications of error correction codes?
- Storage
- Wireless
- Satellite and Space
- Digital Television
- High Speed Modems
What are parity bits?
8th bit for parity
Even parity - make total number of 1 bits even
Odd parity - make total number of 1 bits odd
Use for error detection.
What is cyclic redundancy check (CRC)?
- Data bits to be protected are treated as a binary number
- The binary number is divided by another pre-defined binary number
- The remainder is selected as CRC code
- Receiver checks if CRC matches
- Error detection only
What is hamming code?
Error detection and correction
- One parity bit can tell us an error occurred
- Multiple parity bits can also tell where it occurred.
What is hamming (7, 4)
7 bits total: 4 data bits and 3 parity bits
- Can find and correct 1 bit errors or
- find but not correct 2 bit errors
(Note: review how to calculate)
What is the hamming code syndrome?
- If the syndrome is all zeros, there were no errors
- If there is a 1 bit somewhere, we know it represents an error
What is the hamming code design?
- M bit word with detection/correction takes M=K bit words
- 2^k -1 >= M+K, we can detect, identify, and correct all signal bit errors.
(See example)
What are advanced error correction codes?
- Binary Convolutional Codes (BCC)
- Turbo codes
- Low Density Parity Check (LDPC) codes
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Bluetooth30
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Near Field Communication (NFC)12
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WiFi35
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Wireless Communication Chips36
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Basic Smartphone Components10
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Sample Question Quiz 135
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Cellular Standards (LTE)32
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Global Positioning System (GPS)12
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Sample Question Quiz 228
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Sensors and Error Correction Codes20
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Application Processor Part 156
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Application Processors Part 223
