2.0 Digital Signals Flashcards
Non-Return to Zero vs. Return to Zero
NRZ is when the digital pusle does not return to zero during the bit period.
RZ is when the signal returns to zero in the middle of the bit period.
Why would we want to use NRZ or RZ signals?
RZ allows the receiver to use edge detection instead of amplitude detection. This is used where clock synchronization is important because the output changes value instanteously to match the input signal. Clock rate is twice the bit rate so less BW efficient.
NRZ is more efficient on bandwidth because the clock rate only needs to be equal to the bit rate.
What is a Polar Signal? Why would we use it?
When using voltages to recreate the input signal, we use positive and negative values (rather than using 0 volts).
This can better withstand noise and interference because the 0’s still need to pass a threshold comparison.
What is a Unipolar Signal? What are the pros and cons?
This is the simplest and most common, but it is less immune to noise and interference because there is no threshold comparison for 0 inputs.
What are Bipolar Signals? Why would we use them?
This offers immunity to noise and interference AND maintains a balance in the signals.
Because the signal will change with every input change, it updates the clock signal more often. This is useful for clocking and is therefore important for precise applications.
What are Biphase Signals?
It changes phase every clock signal in addition to the regular unipolar and polar signal changes. This is intended to overcome the lack of synchronization found in unipolar and polar signals.
What is Manchester Encoding?
Transitions in the middle of the period.
The direction of the transition determiens if the bit is a 0 or a 1.
1 is low to high.
0 is high to low.
This allows the clock signal to also be extracted from the signal, which means this is useful where precise timing is important.
What is Differential manchester Coding?
1 = first half of the signal equal to the last half of the previous.
0 = first half of the signal opposite to teh last half of the previous.
Each bit has a positive and negative part (it always changes every bit…)
This allows the signal to be inverted and still recover the data.
