More about Notebooks and T Shirts Lab Notebook from DeForest key in Major Patent Battle Dear Lab Notebook Lab 1 They say things are a bit different down here in the basement Like how your biological clock no longer works How the boiling point of water is slightly elevated And how light slows down just a bit Lab 2 Hey this lab wasn t that bad It s all downhill from here Lab 3 On Valentines Day I made for my significant other a witty valentine card I used phrases like dB my valentine and let s resonate I m not sure why I got slapped Lab 4 I stayed really late in lab last night so I couldn t avoid falling asleep during Dutton s lecture I dreamed that he was delivering our Commencement address and he said that we had to impedance match our college years with the next stage of our lives Lab 5 My doctors tell me that somehow the presence of lead in my blood is three times the federal health limit and if I don t stop whatever I m doing I will become mentally retarded Obviously it s too late Lab 6 I had a horrible nightmare that nothing worked and the TAs told us to rebuild the whole damn thing Wait was that a dream Final If we scream and no one cares do we make a sound You need to get and keep a hard bound lab notebook This is stuff that is absolutely KEY for defining and protecting IP When you go for a job inteview after graduation and you show them your EE133 Notebook and IF you ve done a careful diligent job you might find it to be a major asset job experience The DeForest story is amazing He and his arch rival John Armstrong inventor of FM and Hetero dyning had a pitched battle over IP Unfortunately this B lab book was used as evidence even though DeForest couldn t actually explain his invention 1 Super Heterodyned Receiver Antenna one of Armstrong s MANY contributions RF Filter RF Mixer IF Filter Speaker RF Audio Output Audio Amp VFO LO Variable Frequency Oscillator Tune both filter and VFO at the same time giving output of mixer ALWAYS at Intermediate Freg Local Oscillator Advantages of Super Het Tuning Image Rej Decoupled from detection IF filtering can be optimized and also reused I e many AM stations converted to single IF MUCH easier to work at IF vs directly at RF especially at high frequencies IF at FIXED Freq and therefore LO Freq is also fixed in taking output of IF down to basedband One more pass on the Receiver side this time giving a quick preview of how your commercial radio receivers work As you will certainly see by doing in Lab 5 down conversion to a nicely controlled and well defined intermediate frequency IF is very useful In commercial radio this is at 455KHz and for your projects it will be a bit lower It is at a FIXED frequency for ALL stations That means that the stage before the IF needs to have it s local oscillator LO tuned using a Variable Frequency Oscillator VFO such that the resulting spectrum I e the difference term from the law of the cosines ends up exactly at the IF Then when the spectrum your station s signal modulated about the IF is multiplied times the IF LO the signal is NOW at baseband The above slides and discussion are definitely a fast forward on things we will spend the rest of the quarter working on This discussion is purely motivational in terms of block diagrams of transmitters and receivers 2 Brief Preview of RF Tran ceivers Transmit and Receiver Antenna Mixer Audio Amp Decoding RF Speaker Audio Output LO Local Oscillator Down Converted Signal Your modulated FM signal carrier voice Unwanted Signal Solution I e station at Image Use Filter to Reject Image RF LO Image freq What do RF signals look like in the frequency domain and how do we get them down to baseband where we can hear the information In the simplest case 90 of what EE133 is about the RF band signal will be a carrier with sidebands the sidebands are the information To get the RF signal down to baseband we use our good friend the law of cosines 1 Cos 1t Cos 2 t Sin 1 t 2 t Sin 1 t 2 t 2 Now the math is the same but we are trying to only keep the difference terms that bring our signal back to baseband and filter out the sum terms What s also shown in the figure is an unwanted image signal Unfortunately the multiplier will do its job on ALL signals present unless we filter them out If we don t filter out the image Both the local oscillator LO frequency minus our RF and the Image Freq Minus the LO will BOTH end up in the same down converted frequency range Comment in this example we did NOT convert the modulated signal all the way to zero frequency That is we down converted by a different frequency than we up converted We ll be talking about this more in the demodulation labs especially for FM This NEW frequency will be the IF 3 Blocks for SPAM Receiver HO 1 p 12a Antenna XO Decoding BNC to ANT LNA Mixer SA 602 IF Amp PLL LM 565 BNC to Speaker Lab 1 4 A Quick Look at BW including preview of FCC perspective Direct Conversion Local Oscillator Frequency used In multiplier Transmitted Carrier with Double SideBands info First stage modulation assuming NO distortion LO freq Modulation of already modulated signal distortion Second stage modulation and including fistortion LO1 Bandwidth is basically 2 x BW of baseband I e voice LO2 LO2 3xLO1 freq LO2 3xLO1 Bandwidth can start to look ugly due to distortion FCC may be up close and in your face The top figure is a very simple story in theory that is the wished for future Direct Conversion Basically simply to move the information double side bands directly up to the carrier frequency and by means of the LO exactly at that carrier frequency to again down convert the spectrum to baseband The lower figure shows that exact same figure PLUS the second stage modulation hetero dyning to a second and obviously higher frequency The new piece of information here is the fact that various blocks for example amplifiers may not be linear and the process of distortion creates additional signals Basically the multiplier is happy to send them up in frequency and the overall bandwidth BW of the system can get large and ugly The Federal Communications Commission FCC or big brother doesn t really like to see this ugliness If we are in commercial radio band this may be putting your signals into some else s licensed band a serious NO NO you get shut down for not obeying the rules Bottom line We will spend time as we go along learning more about spectra bandwidth and linearity issues 5 Multipliers Motivation about …