Digital Data Transmission

[Skyferia]

**broken link removed**

Key
01 - Altera DE2 Board (just assume it's an FPGA controlling 02 up to 15)
02 - LCD Module (Hitach HD44780U)
03 - PS/2 Port
04 - N/A
05 - Expansion Header 01 (40 ports; 1x +5V output; 1x +3.3V output; 2x GND; 36 I/O ports)
06 - Expansion Header 02 (40 ports; 1x +5V output; 1x +3.3V output; 2x GND; 36 I/O ports)
07 - PC Keyboard
08 - DAC (component unknown)
09 - Signal Generator
10 - PCB (Transmitter board)
11 - Transmitting antenna
12 - Receiving antenna
13 - Envelope Detector
14 - ADC (component unknown)
15 - LCD Module (Hitach HD44780U)
16 - PCB (Transmitter board)

• Basically when user keys in data using the PC keyboard (07), data is displayed on the LCD Module (02).
  
• When the Return/Enter key on the PC Keyboard is pressed, data is sent to the DAC(08)
  
• The output signal from the DAC (08) is sent through the transmitter(11) and received by the receiver(12).
  
• Signal is asynchronous Amplitude Shift Keying (ASK) (ASK due to transmitting ASCII data bits, or is there a better option?)
  
• The signal generator(09) inputs carrier signal. Frequency band is around 40~41 MHz.
  
• The received signal is sent to the Envelope Detector (13) which demodulates the ASK signal.
  
• The demodulated signal is passed through the ADC (14) and then the output data is sent to the LCD Module (15) to be displayed.
  
• Transmitting distance doesn't matter, lets assume from 15 centimeters to 3 meters.

Questions:

1. Is/are there any mistake(s) in the design?
2. If none for the above, what is a good DAC and ADC to use? An op-amp, perhaps?
3. What is a good and inexpensive component/device for both the transmitter and receiver to use?
4. For the envelope detector, is a diode detector a good option?
5. Any idea on how to power up the transmitter & receiver boards? Using an external power supply, regulated with a voltage/switching regulator a good option?

 

[MikeMl]

How far do you expect to transmit?
What frequncy band?
Why ASK?

 

[Skyferia]

How far do you expect to transmit?

Distance doesn't matter, lets take from 15 centimeters to 3 meters.

What frequncy band?

Around 40~41 MHz

Why ASK?

It's for transmitting ASCII data bits or is there a better method of transmission? If so, please inform.

[I'll update the first post with these information. Thanks for notifying. Airport designator sounds like both fun and complex job.]

 

[kubeek]

It's for transmitting ASCII data bits or is there a better method of transmission? If so, please inform.

ASCII is a table that converts numbers to human writing characters, i don't see any connection with ASK or any other kind of modulation.
You can use ASK if you want, it can be pretty easy to use in this case, but are you sure you want to do your own modulation etc.? You can easily get RF modules that transmit serial data, which could simplify things a lot.

 

[Skyferia]

ASCII is a table that converts numbers to human writing characters, i don't see any connection with ASK or any other kind of modulation.

ASCII characters are each 7-bit data, so basically data is transmitted serially one bit at a time using ASK, from transmitter to receiver, or am I mistaken somewhere?

You can use ASK if you want, it can be pretty easy to use in this case, but are you sure you want to do your own modulation etc.? You can easily get RF modules that transmit serial data, which could simplify things a lot.

I didn't know about the RF modules. Thanks for informing. Could you tell me about them; how it works generally and what components/devices that are available in the market?