# Title Team Members TA Documents Sponsor
18 S-band Radar Altimeter
Bobby Sommers
Elliot Rubin
Rayan Nehme
Koushik Udayachandran design_document1.pdf
Currently, hobbyist RC aircraft and civil drones rely on GPS and barometers for altitude measurements. While these methods are reliable and accurate, they may not tell the operator the full story. GPS is a line of sight system and does not work when the receiver is obscured by terrain or buildings. Barometers read air pressure, but will not measure the distance between an aircraft and terrain. A radar altimeter would provide low-flying drones and RC aircraft with accurate altitude measurements relative to terrain.

Solution Overview:
Our solution relies on a FMCW (frequency modulated continuous wave) S-band radar altimeter powered off of an internal battery. The radar altimeter will be mounted to the bottom of the drone and will use the 2.4GHz ISM band in its operation.

Solution Components:

Processing Unit:
The processing unit will consist of a microcontroller, barometric altimeter, and an SD card slot. The microcontroller will calculate the range to terrain based on the doppler shift from the radar and will log this information to the SD card. It will also record the altitude measured via the barometric altimeter to compare with the radar measurement. Finally, the microcontroller will generate the control signal for the FMCW waveform.

Radar Unit:
The radar unit will consist of two submodules: the transmitter and the receiver.

The transmitter performs frequency modulation using a VCO (voltage controlled oscillator) with a tune voltage generated by the microcontroller. This tune voltage is used to sweep the VCO frequency and creates an FM waveform. A PA (power amplifier) is used to increase the transmit power and is connected to the Tx patch antenna. The Rx patch array receives the reflected signal, amplifies it through a LNA (low noise amplifier), down converts it with a mixer, and provides the demodulated signal to the processing unit.

Power Unit:
The power unit consists of a shielded switching converter to provide DC supply voltage to the other units. This DC power will be regulated by a LDO (low dropout regulator) to provide low-noise power to sensitive components such as the LNA and the VCO.

Criterion for Success:
Our radar altimeter should accurately and precisely measure distance within 1m and record measurement data to a SD card for post processing. It should have a minimum range of 20 m.

There are several 24GHz radar altimeters designed for use on UAVs, but they are more expensive and are not targeted to consumers. Development boards from semiconductor companies and vendors such as Adafruit and Seed also operate in the 24GHz band, but have very limited range (<10 m).

Electronic Automatic Transmission for Bicycle

Tianqi Liu, Ruijie Qi, Xingkai Zhou

Featured Project

Tianqi Liu(tliu51)

Ruijie Qi(rqi2)

Xingkai Zhou(xzhou40)

Sometimes bikers might not which gear is the optimal one to select. Bicycle changes gears by pulling or releasing a steel cable mechanically. We could potentially automate gear changing by hooking up a servo motor to the gear cable. We could calculate the optimal gear under current condition by using several sensors: two hall effect sensors, one sensing cadence from the paddle and the other one sensing the overall speed from the wheel, we could also use pressure sensors on the paddle to determine how hard the biker is paddling. With these sensors, it would be sufficient enough for use detect different terrains since the biker tend to go slower and pedal slower for uphill or go faster and pedal faster for downhill. With all these information from the sensors, we could definitely find out the optimal gear electronically. We plan to take care of the shifting of rear derailleur, if we have more time we may consider modifying the front as well.

Besides shifting automatically, we plan to add a manual mode to our project as well. With manual mode activated, the rider could override the automatic system and select the gear on its own.

We found out another group did electronic bicycle shifting in Spring 2016, but they didn't have a automatic function and didn't have the sensor set-up like ours. Commercially, both SRAM and SHIMANO have electronic shifting products, but these products integrate the servo motor inside the derailleurs, and they have a price tag over $1000. Only professionals or rich enthusiasts can have a hand on them. As our system could potentially serve as an add-on device to all bicycles with gears, it would be much cheaper.

Project Videos