DESIGN OF ASK FSK PSK RECEIVERS USING ORCAD AND

MULTISIM

SUBMITTED BY: VISHAL MISHRA

111EC0179

AIM:

To design receivers for ASK, FSK and PSK modulated signals.

SOFTWARE USED:

ORCAD 16.6 CAPTURE CIS LITE and NI MULTISIM

THEORY:

Ask Receiver:-

The circuit used here is the asynchronous ASK detector. When the signal passes

through a rectifier we get positive half wave signal. By using low pass filter we can

detect the envelope of the signal.in the circuit first op-amp acts as the amplifier in

inverting configuration to amplify the incoming signal. Diode acts as the rectifier

which converts the signal to a half wave signal. Resistor and the capacitor

combinely forms the low pass filter and acts as envelop detector. Second op-amp

with the combination of pot, resistor, diode, and capacitor forms a comparator.

The entire process can be represented with a simple block diagram.

FSK receiver:

In this SPICE simulation two pass band active filters resonant at the frequencies

corresponding to the mark and space states are used in place of the phase lock loop

(PLL) for data recovery. The input signal is an FSK signal read from a file. This signal

is then applied to two band pass filters tuned to 2 kHz and 4 kHz. The output from

each filter is then rectified. Two low-pass filters, with pass band and stop band edge

frequencies of 100 Hz and 2 kHz, to filter the doubled frequency after squaring, are

then connected to a comparator to recover the original data.

PSK Receiver:

This PSK demodulator contains balanced modulators for recovering data from the

PSK signal by multiplying the band pass PSK signal by an identical carrier. The local

oscillator can have errors in frequency and phase placed to simulate the non-

coherent conditions. The recovered data output signal from the centre-tapped

transformer uses a low-pass filter to remove unwanted high-frequency

components.

CIRCUITS AND OUTPUTS:

ASK RECEIVER:

ASK RECEIVER CIRCUIT

ASK GENERATED SIGNAL

RECOVERED SIGNAL

FSK RECEIVER:

FSK CIRCUIT

FSK GENERATED

FSK FILTER OUTPUT

FSK RECOVERED

PSK RECEIVER:

UPPER HALF OF CIRCUIT

LOWER HALF OF CIRCUIT

PSK CIRCUIT

PSK GENERATED SIGNAL

PSK RECEIVER SIGNAL

CONCLUSION:

The circuits were implemented using the softwares and outputs were as shown. ASK

was implemented in multisim software while PSK and FSK were implemented in

ORCAD.