The multimode modem uses a clock signal to generate digitized signals over time, in sinusoidal format (carrier wave). From this digitized sinusoid, the modulation process is applied using different methods for each scheme, implemented through specific internal blocks to perform modulations ASK (switching the amplitude of the sine wave), FSK (switching the frequency of the sine wave through a digital signal modulator) and PSK (phase coding). In the demodulation stage, these three modulation schemes are analyzed to recover the original information, manifesting as '0' or '1' values that reflect the data signal already restored after the process.
The multimode modem has the following inputs and outputs:
Apply a “clock” of 40~50 MHz. Then, apply a “reset” signal of logic level “1” to synchronize the modem system and then make the “reset” signal a logic level “0”. After that, select the type of modulation to be used, as per the sequence below:
Sel = "01" <= ASK modulation and demodulation
Sel = "10" <= FSK modulation and demodulation
Sel = "11" <= PSK modulation and demodulation
After selecting the modulation type, the modulated signal is expressed at the “mod_out” output, and the demodulated signal at the “demod_out” output.
oscilloscope or signal analyzer
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | clock | mod_out_0 | |
| 1 | reset | mod_out_1 | |
| 2 | sel_0 | mod_out_2 | |
| 3 | sel_1 | mod_out_3 | |
| 4 | mod_out_4 | ||
| 5 | mod_out_5 | ||
| 6 | mod_out_6 | ||
| 7 | demod_out |