Changes between Version 50 and Version 51 of Other/Summer/2024/signal

Timestamp:

Aug 6, 2024, 7:01:02 PM (7 weeks ago)

Author:

wesleychen

Comment:

—

Other/Summer/2024/signal

@@ -74 +74 @@
 [[Image()]]
 
-Example of a square wave modulating a sine wave of higher frequency. The square wave switches between 1 and -1 causing the sine wave the flip over and over again.
+Example of a sine wave modulated by a square wave (right). The square wave (middle) switches between 1 and -1 causing the sine wave (left) the flip over and over again.
 
 **BPSK**
 
+What you see above is actually exactly what one signal technique known as BPSK is. BPSK stands for Binary Phase Shift Keying. It can only take on 2 different values every symbol, aka, one bit per symbol. Other methods such as QPSK and QAM can send multiple bits per symbol. It turns out that because of this 1 bit per symbol property, the IQ plot for any BPSK signal is always exactly 2 points. (1, 0) and (-1, 0). I(t) is either -1 or 1 and Q(t) is always 0. So, BPSK signals don't have imaginary components, not that that's relevant as we will be modulating anyways.
+
+[[Image()]]
+
+Below, a BPSK signal has been received, on the top is frequency domain of the signal and on the bottom, the message "hiii".
+
 **OFDM**
+
+OFDM is another signal technique, although this technique "sits" one layer above BPSK. The idea is to split up the bandwidth of a signal into multiple smaller bands and each of those carry data. OFDM stands for Orthogonal Frequency Division Multiplexing and the word "Orthogonal" indicates that the smaller bands do not interfere with each other. Note that the data rate on an OFDM and BPSK signal is the same as the smaller bands on OFDM lead to a slower rates on each channel.
+
+[[Image()]]
 
 **Synchronization**