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Analog Designs    Digital Designs

 

Analog Transmitter Designs

  • The following schematics are the analog FM/AM transmitters considered when making our final design selection.
  • We used the following criteria to pick these circuits:
    •  low supply voltage
    •  small size (low number of components)
    •  availability of components
  • Our focus was on the schematics containing tunnel diodes because they had the fewest number of components.  However, we did not obtain acceptable results from any of the tunnel diode circuits.

     

1) "Olive Martini" FM Transmitter (88-108 MHz)

  • low suppy voltage (1.34V)

  • 9 components (excluding mic): 1 tunnel diode (1N3716), 1 PN2222 transistor

  • We ordered this schematic from Information Unlimited online.  They refer to it as the “Olive Martini FM Transmitter” because it can be constructed to be so small.

  • We had trouble interfacing the microphone with the rest of the circuit.  The microphone and circuit appeared to work separately, but we didn’t see any input from the microphone reflected on the output of the circuit.

2) FM transmitter (88-108 MHz)

  • low supply voltage (1.25V)
  • 9 components: 1 tunnel diode (1N3716), 1 germanium diode (1N34A), and 1 transistor

3) FM transmitter (88-108 MHz)

  • low supply voltage (1.25V)

  • 10 components: 2 tunnel diodes, no transistors

  • We constructed this circuit, but could not get it working.

4) FM transmitter (88-108 MHz)

  • 1.4V supply voltage

  • least # of components: 8 total, 1 tunnel diode, no transistors

  • We were initially very excited about this design, but we could not find a data sheet for the Philco T-1925 tunnel diode. We assembled this circuit using the 1N3716 tunnel diode, but did not have any success.

6) FM transmitter (88-108 MHz)

  • 1.4V supply voltage

  • 13 components: 1 transistors, 1 tunnel diode (1N3716)

  • We did not construct this circuit because it has a relatively high number of components.

7) FM transmitter (88-108 MHz)

  • 1.4V supply voltage

  • 13 components: 2 transistors, no tunnel diode

  • We did not construct this circuit because it has a relatively high number of components.

8) 3V FM transmitter (88-108 MHz)

  • Mark built this circuit, but could not get it to work properly.

  • Note that the supply voltage for this circuit is 3V, therefore it would require two 1.5V hearing aid batteries.

 

9) AM transmitter (530-1700 kHz)    Back to top

  • 1.4V supply voltage

  • 10 components: 1 crystal oscillator, 1 tunnel diode (1N653)

  • Crystal oscillator stabilizes the transmission frequency

  • We did not construct this circuit because of the size of the crystal oscillator.

 

 

Digital Transmitter Designs   Back to top

1)  Digital design using a purchased integrated RF transceiver module operating at 900MHz or 2.4GHz.  A block diagram of this design is shown below.

  • Requires few parts.

  • Large transmission distance, low power, and small in size.

  • Relatively difficult to implement in the allotted time of 4 months.

The following tables contain specifications for three digital modules that could work for this type of design.

 

 

2Digital design using individual IC components consisting of an amplifier, an analog-to-digital converter (CODEC), a microcontroller, and an RF transceiver operating in the 300-500MHz range.  A block diagram of this design is shown below.

  • All ICs are available from a single supplier, Xemics.

  • Large transmission distance, low power, and small in size.

  • More components adds to difficulty of implementation and overall power consumption.

     

 © Team AudioVibe - University of Idaho 2004-2005

Questions or concerns: audiovibe@uidaho.edu