4. Local Oscillator

The local oscillator we used, SI5351-AB-GT clock generator was selected largely due to the fact that Dr. Frohne has used this chip with success. this chip uses a 25Mhz Crystal per the specifications of the datasheet. Using this chip we were able to reach a maximum frequency of 200 Mhz.

In our first revision, our schematic used the incorrect pinouts causing initial errors in our local oscillator, this issue is outlined further in the Closed Issues Section and our final schematic is updated to remedy this error

Unfortunately, we can not listen up to frequencies up to 200 Mhz. Since we need to produce a signal 90 out of phase, to do this we made a 2-bit Johnson Counter using a dual D flip-flop I.C. This allows us to listen to frequencies up to 50 Mhz! This Oscillator is the limiting factor in our frequencies so in the future implementation of this radio it would be nice to either of the following methods

• replace this with an oscillator that goes higher than 200 MHz
• implement the oscillator to use CLK0 and CLK1 and add a delay in software, this would effectively give us a range up to 200MHz

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