Procedure
For lab 12 the class was instructed to use Multisim to construct circuit in order to analyze an RF mixer/IF amplifier system. The components needed were (2) BF904, 1N4148 diode, an LM386-3 Op-Amp, (2) 33uH inductors, (7) resistors (sizes 4.7Ω, 10Ω, 22kΩ (4) and 100kΩ), 12 capacitors in various sizes and types and a 5kΩ potentiometer. Once the circuit was built, test equipment was added which consisted of 2 low voltage DC power supply, 3 function generators and a dual-trace oscilloscope.
After the circuit was built and running there were 7 test points that the oscilloscope was hooked up to in order to see the variation of the sine wave.
Results
In Figure 12-1 at TP 1, we had the frequency set at 1.2 MHz and the amplitude was set at 50 mVp on Function Generator 1. The frequency was set at 1.7 MHz and the amplitude was set at 50mVp on Function Generator 2. The Timebase Scale was set at 20 μs /Div, Channel A Scale was set at 50mV/Div, and Channel B Scale was set at 5V/Div on the Oscilloscope. The settings of the two Function Generators and the scales on the Oscilloscope resulted in the hump form, which is known as the AM Modulation.
In Figure 12-2 at TP2, the Function Generators 1 and 2 and the Oscilloscope Scales (Timebase, Channel A, and Channel B) were set up the same way as Test Point 1. The results showed the hump or AM Modulation moving faster than Test Point 1and a thicker distorted band was forming. The small thick distorted band of the waveform could have been because of the two capacitors being used were.1 μF and the two resistors being used were 22 kΩ in the RF Mixer and the settings on the two Function Generators and the scales on the Oscilloscope.
In Figure 12-3 at TP3, the Function Generators 1 and 2 and the Oscilloscope Scales (Timebase, Channel A, and Channel B) were set up the same way as Test Point 1 and 2. The results for Test Point 3, the AM Modulation was a lot smaller in size as this was the end of the RF Mixer.
In Figure 12-4 at TP4, the Function Generators 1 and 2 and the Oscilloscope Scales (Timebase, Channel