Gaurish Kapoor, Matthew Morgan, and Andy Saunders

1
Remote Beam Stop for LIDAR

• Group 3
• Gaurish Kapoor, Matthew Morgan, and Andy Saunders
• ECE 397 Senior Design

2
Introduction

• Our system provides a remote way of switching
  on and off the LIDAR beam stop.
• Transmitter
• Receiver
• Control/Signal Processing

3
Benefits and Features

• Convenient remote or computerized control
• Hard switch to turn beam stop on
• three separate channels
• Unique design
• Ability to control power to any device plugged
  into it (within voltage and current limits)
• Digital wireless password
• Reprogrammable MSP430 microcontrollers with
  programming header (JTAG)

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System Overview - Transmitter
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System Overview - Receiver
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Outline

• Control Circuits MSP 430
• RF Transmitter System FSK modulator, RF
  transmitter (Mixer, Oscillator, Antenna)
• RF Receiver System RF receiver, FSK
  demodulation (AC/DC conversion, etc.)
• Control Circuits MSP430, RS-232

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Control Systems (Transmitter)

• Based around the MSP430F2619
• Activated by pushbuttons

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Control Systems (Testing and Verification)
OFF Signal
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Control Systems (Testing and Verification)
continued
ON Signal
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Transmitter Design Overview

• Transistor Switches Eliminated
• Adder
• Oscillators 2.4 GHz, 20 MHz, 27 MHz
• Mixer

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Transistor Switches (Eliminated)

• Used to switch on power to the 20 and 27 MHz
  oscillators.
• Eliminated from the final design due to this
  system being unnecessary.

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Adder Design

• Combines the outputs of the 20 and 27 MHz
  oscillators
• Used to provide protection in the event of both
  oscillators being active at once.

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Adder Verification

• Oscilloscope trace showing the MSP430 bit
  pattern after conversion to analog form.

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Oscillators

• Fox Oscillators were used for 20 and 27 MHz
• These were chosen for their combination of stable
  output, low frequency, and low cost.
• Simple pinout for easy integration into our
  circuits.
• Maxim Oscillators were used for the 2.4 GHz
  oscillators
• Chosen for their low input voltage and tunable
  output frequency.

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Maxim Oscillators Testing and Verification

• Output spectrum of the 2.4-2.5 GHz oscillators
  when tuned to 2.46 GHz
• Effective SNR of approximately 50 dB

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Maxim Oscillators Problems Encountered

• The oscillator needs to be very well shielded to
  minimize interference in the transmitter.
• The output can fluctuate when the board is
  bumped, which is due to the use a potentiometer
  instead of a fixed resistive divider on the
  tuning input of the oscillator.

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Upconverting Mixer

• We chose the AD8343 from Analog Devices
• This chip has the advantages of low power
  consumption and low supply voltage range
• The mixer is broadband, allowing us to use it for
  the transmitter and receiver.

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Upconverting Mixer Verification

• Mixer Output when fed with 20 MHz signal with
  local oscillator at 2.458 GHz
• SNR of approximately 25 dB

Note For this tests, the input low frequency
signal was received from a signal generator with
an output power of 0 dBm.
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Upconverting Mixer Verification (Continued)

• Mixer Output when fed with 27 MHz signal with
  local oscillator at 2.4525 GHz
• SNR of approximately 14 dB

Note For this test, the low frequency signal was
received from a signal generator with an output
power of 0 dBm.
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Combined Testing of RF Transmitter Section

• Connect all of the previously described
  components and check the following on a vector
  signal analyzer
• Output frequencies
• Output power at desired frequencies
• Noise floor

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Combined RF Transmitter Section Testing

• Mixer output when fed with 20 MHz signal with
  local oscillator at 2.449 GHz

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Combined RF Transmitter Section Testing
(Continued)

• Mixer output when fed with 27 MHz signal with
  local oscillator at 2.452 GHz

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Combined RF Transmitter Testing Problems
Encountered

• Considerable bleed-through of the local
  oscillator into the output spectrum
• This can be remedied with considerable shielding
  between the mixer and oscillator
• Output power of desired peaks is too low for
  transmission over any appreciable distance
• This can be remedied with amplification at the
  mixer output.

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Receiver Design

• RF Design
• Mixer impedance matching
• RF oscillator tuning

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Receiver Design

• A/D Design
• Filter Design
• Rectifier Design

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Receiver Testing

• RF Testing
• RF oscillator testing
• Mixer testing
• Wireless Reception Range Testing (using function
  generator)
• A/D Testing
• Filter Testing
• Rectifier Testing

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Receiver Testing

• RF oscillator Testing Results
• Tuned Output 2.45028GHz
• Output Power -13.019dBm
• SNR -13.019dBm (-66dBm) 52.981dB 1986551

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Receiver Testing

• Mixer Testing Results
• Results _at_ 20MHz
• Measured Frequency 19.999MHz
• Output Power -39.2dBm
• SNR -39.20dBm (-66.30dBm) 27.1dB 5131
• Results _at_ 27MHz
• Measured Frequency 27.007MHz
• Output Power -41.69dBm
• SNR -41.69dBm (-66.30dBm) 24.61dB 294.51

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Receiver Design

• Wireless Reception Range Testing

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Receiver Testing

• Filter Test Results
• Lowpass Filter (5 pole)
• Passband Power (20MHz) -10.959dBm
• Stopband Power (27MHz) -39.25dBm
• Attenuation Ratio 28.291dB
  848.37 1
• Highpass Filter (9 pole)
• Passband Power (27MHz) -0.85dB
• Stopband Power (20Mhz) -9.121dB
• Attenuation Ratio 8.271dB 6.719
  1

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Receiver Testing

• A/D Test Results

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Control Systems (Receiver)

• MSP430 serial communication ports
• comparator A
• Relay with BJT switch and DC/DC converter

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Ethics

• FCC regulations
• Reliability

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Further Improvements

• Add Amplification
• Better Impedance Matching
• Better Packaging
• Add Features

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Conclusions

• Working Receiver
• Working AC/DC
• Working Transmitter
• Working MSP code