27-09-2010, 04:56 PM
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ABSTRACT
The RF transmitter is built around the ASIC and common passive and active components, which are very easy to obtain from the material shelf. The circuit works on Very High Frequency band with wide covering range. The Carrier frequency is 147 MHz and Data frequencies are 17 MHz,19 MHz,22 MHz & 25 MHz. It should be noted that ASIC or Application Specific Integrated Circuit is proprietary product and data sheet or pin details or working principles are not readily available to the user.
CIRCUIT DESCRIPTION:
The ASIC Transmitter IC has four inputs and only one output pin. The four inputs are for the frequency range of 17 KHz, 19 KHz, 22 KHz and 25 KHz and four switches are provided for each range. When any one switch is selected, that frequency is added to the Transmitter circuit as data frequency and transmitted in the air. The Crystal X1 with two coupling capacitor provides the working oscillator frequency to the circuit. The Capacitors C6 and C7 are to stabilize the crystal oscillator frequency.
PARTS LIST
SEMICONDUCTORS:
IC ASIC 1
T1 BC 547 NPN Transistor 1
T2 BF 494 NPN Transistor 1
RESISTORS:
R1 & R2 2.7 K Ohm ¼ Watt 2
R3 & R6 330 K Ohm ¼ Watt 2
R4 1 K Ohm ¼ Watt 1
R5 47 K Ohm ¼ Watt 1
CAPACITORS:
C1, C2 0.001 Pico Farad Capacitor 2
C3 & C7 0.022 Pico Farad Capacitor 2
C4 4.7 Pico Farad Capacitor 1
C5 & C6 0.01 Micro Farad Capacitor 2
MISCELLANEOUS:
X1 1.44 MHz Crystal 1
S1 to S4 ON/OFF SWITCHES 4
L1 RF Coil 200mH 1
L2 Aerial or Telescopic Antenna 1
CIRCUIT DESCRIPTION:
The ASIC Transmitter IC has four inputs and only one output pin. The four inputs are for the frequency range of 17 KHz, 19 KHz, 22 KHz and 25 KHz and four switches are provided for each range. When any one switch is selected, that frequency is added to the Transmitter circuit as data frequency and transmitted in the air. The Crystal X1 with two coupling capacitor provides the working oscillator frequency to the circuit. The Capacitors C6 and C7 are to stabilize the crystal oscillator frequency.
PARTS LIST
SEMICONDUCTORS:
IC ASIC 1
T1 BC 547 NPN Transistor 1
T2 BF 494 NPN Transistor 1
RESISTORS:
R1 & R2 2.7 K Ohm ¼ Watt 2
R3 & R6 330 K Ohm ¼ Watt 2
R4 1 K Ohm ¼ Watt 1
R5 47 K Ohm ¼ Watt 1
CAPACITORS:
C1, C2 0.001 Pico Farad Capacitor 2
C3 & C7 0.022 Pico Farad Capacitor 2
C4 4.7 Pico Farad Capacitor 1
C5 & C6 0.01 Micro Farad Capacitor 2
MISCELLANEOUS:
X1 1.44 MHz Crystal 1
S1 to S4 ON/OFF SWITCHES 4
L1 RF Coil 200mH 1
L2 Aerial or Telescopic Antenna 1