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Phase Locked Loop - Experimental Verification & Conclusions

V. Experimental Verification

5.1 Experimental Performance Comparison

The specifications for the Phase-Locked Loop are shown above in Table 5.5.2. The majority of the specifications are within 10% of the factory specifications. Some of the specifications that are not within 10% are due to the fact that the circuit was built on a breadboard. The VCO maximum operating frequency is only 54kHz, while the factory spec is 500kHz. This vast difference is due primarily from the capacitance of the breadboard. The measured output impedance at pin 4 is ten times lower than the factory spec. Although lower output impedance is desired, there is some question to the validity of the factory specifications. The measured square wave rise time is a factor of ten slower than the factory spec. Again this is due to the capacitance of the breadboard. Even with some of the measured specifications being so diverse from the factory specs, the circuit still performed functionally the same as the integrated version.

Table 5.5.2 PLL Measured Specifications versus Factory Specifications

5.2 FM Demodulator

PLLs are commonly used in demodulating signals in a FM receiver. This is why we choose to show that the PLL that we designed and built worked functionally. In order to make the FM signal we connected two function generators together. The first function generator was used to modulate the frequency of the second, which was set to the fee running frequency of the PLL. When we connected the PLL to the FM signal from the frequency generators, the output of the PPL was the original signal from the first function generator.

Figure 5.2.1 Application in FM Demodulation

Figure 5.2.2 LM565 PLL Implemented using Discrete Devices

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