Generating Binary Phase Shift Keying - Lab Report Example

Normally, each of the phases is encoded equal bits. The demodulator is designed primarily for symbol-set to be used by the modulator. This modulator is used in determining the phase of the signal received mapping it back to the symbol that it represents. It, therefore, requires the receiver to compare the received signal phase to the reference signal. This system is termed as coherent. This paper explores an experimental set up in which an IQ modulator is used to generate the Binary Phase-shift keying while investigating the effect of phase shift on the residual carrier magnitude.

Aims and objectives. A To appreciate the principle of phase shift keying and its relationship with the analogue phase modulation. B. To generate the two-level of phase shift keyed signal and investigate the spectrum and bandwidth associated with it. C. To investigate the demodulation of an FSK signal using the Residual carrier D. To understand the operation of the costals Loop circuit for phase demodulation E. To investigate the demodulation of 90 degree FSK signal using a costals Loop and using Schematic diagram of an IQ modulator connected to Residual carrier Equipment used and Practical configuration In this experiment, the list of apparatus that were used include the sine cosine generator, variable attenuator, multiplier, IQ modulator connected to a residual carrier, costal loop block diagram that has low pass filters and Limiters and the circuits that operate like comparators.

The apparatus were configured as shown below. Schematic diagram of an IQ modulator connected to Residual carrier Schematic circuit of a double costal loop Procedure The frequency counter was opened and used to set the Function Generator Frequency to 15KHz .The phasescope main channel probe was then moved to the 1 carrier input. The phasescope was then opened and while using the Variable phase shift control associated with the Carrier Source, the IQ carrier phase difference was set to 90 degrees.

The phase scope main channel was moved to the phase modulator output monitor point 4 and set to constellation display mode. The signal Level Control was then used in adjusting the amplitude of modulation. This was followed by setting the X expand on the oscilloscope to observe the individual carrier cycles. The spectrum analyzer was opened and used to observe the phase scope. The signal Level Control was then used in adjusting the modulation. The modulation was increased to give a total shift towards 180 degrees, while adjusting the spectrum analyzer.

Finally, with the shift at plus and minus 90 degrees, the oscilloscope display was observed and the instrumentation screen shots were captured. The diagram bellow shows the experimental set up Results The results for this experiment are presented below. - AC p-p set to 0.3v / frequency set at 15kHz. Instead of setting the phases at -90 and +90 degrees, in this experiment -45 and +45 degrees were used since the prior could not be achieved and it is as shown below. Changing the amplitude of the modulation can vary the phase shift.

Concentrating on the blue output (carrier) is switches the phase by 180 degrees The carrier and the sidebands as seen during this experiment. A total phase shift of near to 90 degrees (45 + 45) Spectrum analyser showing the carrier frequency and two sidebands. When the phase shift was put to 180 degrees the carrier frequency on the spectrum analyzer fails to be distinguishable. Second attempt This shows the oscilloscope with the