The Type NCD-1 is a classical textbook representation of non-coherent demodulation of bandpass-filtered, envelope-detected ASK and MARK/SPACE FSK in the presence of additive noise. The envelope-detected ASK and FSK (MARK/SPACE) is compared to a variable threshold or the FSK MARK and SPACE can be compared to each other, to determine the bit sent. The Type NCD-1 demodulator board has a built-in RMS power detector that accurately determines the signal power and the noise power all along the demodulation process. Once the input signal and noise power is set for 0-dB input SNR, the noise power on the Type NS-1 Noise Source can be reduced in 1-dB steps to increase the SNR.
The ASK and FSK signals are generated by the Type MOD-1 Signal Modulator board and the Type BER-1 BER Measurement board displays the Bit Error Ratio (BER) as a function of the Noise Power level from the NS-1 Noise Source (therefore sets the SNR).
The Type NCD-1 demodulates pseudorandom ASK and FSK data from the Type MOD-1 Signal Modulator from 4 ~ 64kbps and also allows the 8-bit PCM or CVSD recovered digital audio to be looped back to the Type MOD-1 board for audio quality comparisons as a function of the SNR.
The measured BER of this system matches very closely to that presented in theory and the student will have the opportunity to make these measurements and see the effect of the BER verses the SNR as one varies the detector threshold level to find the optimum setting.
The Type NCD-1 Non-coherent demodulator board requires +/-12 VDC @ 450mA, maximum and derives its power from the Type MOD-1 Signal Modulator board. Power inputs are polarity protected.
The Type NCD-1 Non-coherent demodulator provides:
- Non-coherent bandpass envelope detection of ASK
- Non-coherent bandpass envelope detection of FSK MARK and FSK SPACE
- Selectable, variable or self-threshold, detection
- Data Rates from 4 ~ 64kbps
- On-board noise and signal RMS power measurement
- Connects to Type BER-1 for Bit Error Ratio (BER) display
- Accepts and loops back Data and Clock from Type MOD-1 Signal Modulator for PCM and CVSD CODEC recovered audio comparison under various BER
The Type NCD-1 Non-coherent demodulator comes with:
- Technical Manual that covers Configuration, Operation, General Theory, Block Diagrams, Schematic Diagrams. 79 pages, 31 Figures, 16 Tables. Parts List.
- Two, 3-foot RG-58/BNC 50-ohm cables
- One, 3-foot power cable for connection with Type MOD-1
- 22, 2-pin configuration jumpers
- Type NCD-1 board outline is (width x depth) 9" x 10" (228.6 x 254.0mm)