[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:03.20,Default,,0000,0000,0000,,>> The last part of our circuit\Nis the diode detector.
Dialogue: 0,0:00:03.20,0:00:05.55,Default,,0000,0000,0000,,We have two diode detectors right here.
Dialogue: 0,0:00:05.55,0:00:08.16,Default,,0000,0000,0000,,One that's designed for 2.4 gigahertz
Dialogue: 0,0:00:08.16,0:00:10.80,Default,,0000,0000,0000,,and the other that's\Ndesigned for 2.6 gigahertz.
Dialogue: 0,0:00:10.80,0:00:13.14,Default,,0000,0000,0000,,The way the diode detector works.
Dialogue: 0,0:00:13.14,0:00:16.27,Default,,0000,0000,0000,,I'm just going to show you\Nthe little circuit right here of these.
Dialogue: 0,0:00:16.27,0:00:19.29,Default,,0000,0000,0000,,The way the diode detector\Nworks is the AC signal comes
Dialogue: 0,0:00:19.29,0:00:22.26,Default,,0000,0000,0000,,out of either one of the band-pass filters.
Dialogue: 0,0:00:22.26,0:00:23.79,Default,,0000,0000,0000,,Remember, we don't know\Nwhich one's going to
Dialogue: 0,0:00:23.79,0:00:26.07,Default,,0000,0000,0000,,have the signal. One or the other will.
Dialogue: 0,0:00:26.07,0:00:28.17,Default,,0000,0000,0000,,But AC signal comes in right here,
Dialogue: 0,0:00:28.17,0:00:31.100,Default,,0000,0000,0000,,goes through a diode and then\Nis integrated by a capacitor.
Dialogue: 0,0:00:31.100,0:00:34.05,Default,,0000,0000,0000,,The original signal that comes in is
Dialogue: 0,0:00:34.05,0:00:36.39,Default,,0000,0000,0000,,the black sine wave that\Nyou see right here.
Dialogue: 0,0:00:36.39,0:00:37.59,Default,,0000,0000,0000,,That is VAC.
Dialogue: 0,0:00:37.59,0:00:40.54,Default,,0000,0000,0000,,Maybe, it's at 2.4 gigahertz in this case.
Dialogue: 0,0:00:40.54,0:00:43.37,Default,,0000,0000,0000,,The diode only allows\Ncurrent to go one way.
Dialogue: 0,0:00:43.37,0:00:47.04,Default,,0000,0000,0000,,So it only allows the positive part\Nof our signal to get through.
Dialogue: 0,0:00:47.04,0:00:49.88,Default,,0000,0000,0000,,The red line right here\Nis the signal when it
Dialogue: 0,0:00:49.88,0:00:53.02,Default,,0000,0000,0000,,goes to the diode and that's\Ncalled halfway rectified.
Dialogue: 0,0:00:53.02,0:00:55.18,Default,,0000,0000,0000,,Rectified means that it's\Nturned right side up.
Dialogue: 0,0:00:55.18,0:00:58.54,Default,,0000,0000,0000,,In this case, only half of\Nthe wave is passed through.
Dialogue: 0,0:00:58.54,0:01:00.75,Default,,0000,0000,0000,,Then, when it goes through this capacitor,
Dialogue: 0,0:01:00.75,0:01:03.94,Default,,0000,0000,0000,,the capacitor integrates\Nor averages that signal.
Dialogue: 0,0:01:03.94,0:01:06.56,Default,,0000,0000,0000,,So the dashed line is the DC voltage
Dialogue: 0,0:01:06.56,0:01:09.69,Default,,0000,0000,0000,,that's going to come out\Nof that capacitor VDC.
Dialogue: 0,0:01:09.69,0:01:12.78,Default,,0000,0000,0000,,Let's see where those are\Nin our diode circuit.
Dialogue: 0,0:01:12.78,0:01:15.30,Default,,0000,0000,0000,,So right here's my diode circuit
Dialogue: 0,0:01:15.30,0:01:18.26,Default,,0000,0000,0000,,VAC comes out of the band-pass\Nfilter at this point,
Dialogue: 0,0:01:18.26,0:01:20.14,Default,,0000,0000,0000,,let's say it's 2.4 gigahertz.
Dialogue: 0,0:01:20.14,0:01:23.18,Default,,0000,0000,0000,,It comes into my system and\Nthere's the diode right there.
Dialogue: 0,0:01:23.18,0:01:26.52,Default,,0000,0000,0000,,You can't see but it's\Na little triangle thing like so.
Dialogue: 0,0:01:26.52,0:01:29.04,Default,,0000,0000,0000,,But there's the diode and that is
Dialogue: 0,0:01:29.04,0:01:31.95,Default,,0000,0000,0000,,half-wave rectified signal.\NHere's the capacitor.
Dialogue: 0,0:01:31.95,0:01:33.53,Default,,0000,0000,0000,,It's just like the capacitors we had on
Dialogue: 0,0:01:33.53,0:01:36.00,Default,,0000,0000,0000,,the amplifier and it goes down to ground.
Dialogue: 0,0:01:36.00,0:01:37.44,Default,,0000,0000,0000,,The ground is underneath.
Dialogue: 0,0:01:37.44,0:01:40.94,Default,,0000,0000,0000,,Here goes down to ground and\Nthen right there is going to be
Dialogue: 0,0:01:40.94,0:01:45.42,Default,,0000,0000,0000,,the DC signal that comes\Nout if it is 2.4 gigahertz.
Dialogue: 0,0:01:45.42,0:01:48.41,Default,,0000,0000,0000,,That signal then can go\Ninto a comparator and be
Dialogue: 0,0:01:48.41,0:01:52.18,Default,,0000,0000,0000,,converted to a zero or a one\Nto be used by the computer.
Dialogue: 0,0:01:52.18,0:01:56.51,Default,,0000,0000,0000,,On this side, we have the same thing and\Nit's designed for 2.6 gigahertz where
Dialogue: 0,0:01:56.51,0:01:59.78,Default,,0000,0000,0000,,the AC signal comes in because the diode is
Dialogue: 0,0:01:59.78,0:02:03.17,Default,,0000,0000,0000,,integrated across the capacitor\Nand comes out as a DC value.
Dialogue: 0,0:02:03.17,0:02:06.23,Default,,0000,0000,0000,,Now, there are some other little parts\Nof this circuit too.
Dialogue: 0,0:02:06.23,0:02:09.29,Default,,0000,0000,0000,,These have short circuited\Nstubs and that impedance
Dialogue: 0,0:02:09.29,0:02:14.14,Default,,0000,0000,0000,,matches these 50 Ohm lines to\Nthe diodes that are not 50 Ohm.
Dialogue: 0,0:02:14.14,0:02:18.11,Default,,0000,0000,0000,,There's 100 Ohm line here and\Nan open-circuited stub that match
Dialogue: 0,0:02:18.11,0:02:22.42,Default,,0000,0000,0000,,the impedance of this particular diode\Nto this particular transmission line.
Dialogue: 0,0:02:22.42,0:02:24.100,Default,,0000,0000,0000,,Another interesting thing\Nthat you can see right here
Dialogue: 0,0:02:24.100,0:02:27.47,Default,,0000,0000,0000,,is because we had a little trouble\Nmatching this particular one.
Dialogue: 0,0:02:27.47,0:02:31.98,Default,,0000,0000,0000,,We actually put two stubs on just to\Nhelp with the impedance matching.
Dialogue: 0,0:02:31.98,0:02:37.26,Default,,0000,0000,0000,,So, that's a picture of\Nour frequency shift keyed system.
Dialogue: 0,0:02:37.26,0:02:40.29,Default,,0000,0000,0000,,Let's look again to see where the\Ninductors and capacitors are.
Dialogue: 0,0:02:40.29,0:02:41.84,Default,,0000,0000,0000,,We've got our antenna right here.
Dialogue: 0,0:02:41.84,0:02:45.00,Default,,0000,0000,0000,,The transmission line is seen\Nas a series of resistors,
Dialogue: 0,0:02:45.00,0:02:47.51,Default,,0000,0000,0000,,inductors, capacitors, and conductors.
Dialogue: 0,0:02:47.51,0:02:51.44,Default,,0000,0000,0000,,We have capacitors right here\Nto block the DC signal from
Dialogue: 0,0:02:51.44,0:02:56.76,Default,,0000,0000,0000,,the AC and an inductor to keep\Nthe AC out of our DC power supply.
Dialogue: 0,0:02:56.76,0:02:59.48,Default,,0000,0000,0000,,We have a surface mount\Nresistor right there in
Dialogue: 0,0:02:59.48,0:03:02.15,Default,,0000,0000,0000,,our 3dB coupler and then\Nwe have a series of
Dialogue: 0,0:03:02.15,0:03:04.64,Default,,0000,0000,0000,,band-pass filters that\Nare made up of a set of
Dialogue: 0,0:03:04.64,0:03:08.32,Default,,0000,0000,0000,,effective resistors,\Ncapacitors and inductors.
Dialogue: 0,0:03:08.32,0:03:12.53,Default,,0000,0000,0000,,Then when we get over to\Nthe diode detector circuit,
Dialogue: 0,0:03:12.53,0:03:17.58,Default,,0000,0000,0000,,a capacitor is used again in order to\Nintegrate my halfway rectified signal.
Dialogue: 0,0:03:17.58,0:03:20.38,Default,,0000,0000,0000,,So we've used a lot of capacitors\Nand inductors in the circuit.
Dialogue: 0,0:03:20.38,0:03:22.36,Default,,0000,0000,0000,,I just thought you might like to see it.