[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:03.66,Default,,0000,0000,0000,,>> Okay. Now let's talk\Nabout the antenna block.
Dialogue: 0,0:00:03.66,0:00:05.88,Default,,0000,0000,0000,,The antenna right here is what's
Dialogue: 0,0:00:05.88,0:00:08.08,Default,,0000,0000,0000,,used to receive the signal\Nin the first place.
Dialogue: 0,0:00:08.08,0:00:11.52,Default,,0000,0000,0000,,The antenna is a 2.4 or 2.6
Dialogue: 0,0:00:11.52,0:00:15.22,Default,,0000,0000,0000,,gigahertz antenna so they can receive\Nboth of the possible frequencies.
Dialogue: 0,0:00:15.22,0:00:19.38,Default,,0000,0000,0000,,They come into this antenna which\Nis a quarter of a wavelength long,
Dialogue: 0,0:00:19.38,0:00:24.06,Default,,0000,0000,0000,,and underneath there's copper\Nunderneath each of these strips.
Dialogue: 0,0:00:24.06,0:00:28.08,Default,,0000,0000,0000,,So, that this thing right here is\Na microstrip as a transmission line.
Dialogue: 0,0:00:28.08,0:00:31.53,Default,,0000,0000,0000,,Now, the transmission lines are\Nnormally modeled like this.
Dialogue: 0,0:00:31.53,0:00:35.80,Default,,0000,0000,0000,,Their model is a combination of\Nresistors, inductors, capacitors,
Dialogue: 0,0:00:35.80,0:00:39.34,Default,,0000,0000,0000,,and conductors G so that\Neach little distance
Dialogue: 0,0:00:39.34,0:00:42.92,Default,,0000,0000,0000,,along this transmission line can\Nbe assumed to be a resistive,
Dialogue: 0,0:00:42.92,0:00:46.09,Default,,0000,0000,0000,,capacitive, inductive, conductive network.
Dialogue: 0,0:00:46.09,0:00:47.64,Default,,0000,0000,0000,,So that's a transmission line.
Dialogue: 0,0:00:47.64,0:00:51.95,Default,,0000,0000,0000,,Okay now, as the signal is\Nreceived by this antenna,
Dialogue: 0,0:00:51.95,0:00:54.74,Default,,0000,0000,0000,,the antenna has\Na particular input impedance.
Dialogue: 0,0:00:54.74,0:00:58.52,Default,,0000,0000,0000,,On the other side, the amplifier has\Na particular input impedance as well,
Dialogue: 0,0:00:58.52,0:01:01.08,Default,,0000,0000,0000,,and these two impedances\Nneed to be matched at
Dialogue: 0,0:01:01.08,0:01:04.54,Default,,0000,0000,0000,,the stub and they wouldn't be and\Nso we have to manually match them.
Dialogue: 0,0:01:04.54,0:01:08.93,Default,,0000,0000,0000,,This thing right here is an open-circuited\Nstub that's used to impedance match
Dialogue: 0,0:01:08.93,0:01:11.63,Default,,0000,0000,0000,,the antenna to the transmission line and
Dialogue: 0,0:01:11.63,0:01:14.70,Default,,0000,0000,0000,,then the amplifiers also matched\Nto this transmission line.
Dialogue: 0,0:01:14.70,0:01:18.08,Default,,0000,0000,0000,,This particular transmission line\Nis a 50 Ohm transmission line.
Dialogue: 0,0:01:18.08,0:01:21.24,Default,,0000,0000,0000,,So, we need this antenna\Nto be matched to 50 Ohm's.
Dialogue: 0,0:01:21.24,0:01:22.61,Default,,0000,0000,0000,,The way we do it is we have
Dialogue: 0,0:01:22.61,0:01:27.54,Default,,0000,0000,0000,,a particular distance here and a\Nparticular length of the stub.
Dialogue: 0,0:01:27.54,0:01:30.29,Default,,0000,0000,0000,,It's literally just a little stub\Nof copper that we
Dialogue: 0,0:01:30.29,0:01:33.23,Default,,0000,0000,0000,,cut with scissors and stuck down,
Dialogue: 0,0:01:33.23,0:01:35.09,Default,,0000,0000,0000,,this literally stuck it right down there
Dialogue: 0,0:01:35.09,0:01:37.16,Default,,0000,0000,0000,,so it's touching this transmission line.
Dialogue: 0,0:01:37.16,0:01:39.90,Default,,0000,0000,0000,,The length of the stub is\Ngoing to make it either
Dialogue: 0,0:01:39.90,0:01:43.30,Default,,0000,0000,0000,,capacitive or inductive depending\Non the length of the stub.
Dialogue: 0,0:01:43.30,0:01:46.97,Default,,0000,0000,0000,,Remember that inductors and\Ncapacitors create phase shifts.
Dialogue: 0,0:01:46.97,0:01:48.95,Default,,0000,0000,0000,,A phase shift is just a time delay.
Dialogue: 0,0:01:48.95,0:01:52.46,Default,,0000,0000,0000,,So as a little bit of signal goes\Nup this line and comes back,
Dialogue: 0,0:01:52.46,0:01:55.13,Default,,0000,0000,0000,,that's the time delay\Nthat it experiences and
Dialogue: 0,0:01:55.13,0:01:58.10,Default,,0000,0000,0000,,consequently the phase\Nshift that it also obtains.
Dialogue: 0,0:01:58.10,0:02:00.22,Default,,0000,0000,0000,,So, once we get past this point,
Dialogue: 0,0:02:00.22,0:02:02.57,Default,,0000,0000,0000,,the antenna and this combination of
Dialogue: 0,0:02:02.57,0:02:07.11,Default,,0000,0000,0000,,impedance matching network are\Nnow matched to a 50 Ohm line.