Sensor For Cellular Activity

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High Speed Digital Lab

• Sensor For Cellular Activity

Supervised by Yossi Hipsh Preformed by Assaf
Haim Ohad Fremder
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Presentations Topics

• Projects Goal.
• Introduction to the projects main idea.
• Motivation for the project.
• Suggested Solution
• Theoretical solution.
• Justifications
• Technical details.
• Solution steps
• Questions ?

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Projects Goal
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Introduction to the projects main idea

• Detect existence of cellular activity
• Pin-pointing a location of an existing cellular
  device in a confined location.

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Motivation for the project

• Prevent students inserting cellular devices into
  test rooms.
• Alert for entering the operating room with a
  cellular device.
• Detect cellular activity in an air-plane.
• Find a man in distress inside a building.

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Suggested Solution
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Theoretical solution

• We will use 2 different kinds of detectors
  directional antennas and energy.
• The energy detector will acknowledge cellular
  activity in the area.
• We will place 3 antennas within the room.
• Each antenna will give us the direction from the
  antenna to the cellular device.
  

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Theoretical solution Cont.

• Each antenna actually gives us a direction
  (plane) in which the source can be found, and
  so with 3 crossing directions we will receive a
  single point.
• We need each antenna to give us the direction
  with a 0.5mx0.5m precision.
• To find the direction we decided to use an array
  of two elemental antennas in each antenna.

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Theoretical solution Cont.
LO
Antenna 1
Gain
Gain
BPF
Mixer
BPF
Out
Multiplier
LO
Antenna 2
Gain
Gain
BPF
BPF
Mixer
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Justifications

• The signal modulation does not effect the
  performance of the energy detector, for it
  samples the max amplitude of the signal.
• The directional antennas will not be affected by
  the modulation. Due to the slow rate of
  modulation as against to the high speed of the
  Electro-Magnetic wave.

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Justifications Cont.

• The chosen directional antennas will simply do
  the following
• Each elemental antenna will isolate the frequency
  and multiply it with the output of the other
  elemental antenna.
• The result will be (We are considering a sinusoid
  signal) 2 elements, one will be DC and the other
  AC.
• We will isolate the DC signal which will
  represent the phase difference between the two.

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Justifications Cont.

• Mathematical solution
• Signal 1 A(t)cos(w(t)t b(t) P1)
• Signal 2 A(t)cos(w(t)t b(t) P2)
• When we remove the time dependencies and multiply
  the two elements(A2)/2cos(P1-P2)
  cos(2wt2b P1P2)

DC component
AC Component
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Technical details

• The cellular in Israel is working around two
  major frequencies
• 800-900Mhz
• 1800-1900Mhz
• The signal modulation according to the GSM
  protocol is phased modulation.
• The cellular transmit Power is between 0.25W-0.6W

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Solution steps

• Schedule
• -Finish by 5-10/2
• Finish by 2-9/3
• Finish by 2-9/4
• Finish by 2-9/5
• Finish by the end of the second semester

• Finishing theory
• Find the exact power and frequency transmitted by
  a cell phone.
• Calculate the needed sizes and other properties
  of the antenna
• Building one elemental antenna, testing.
• Building one antenna, testing.
• Setting up 3 antennas.
• Testing.

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Questions ?