Superheterodyning - How Radios And Cell Phones Tune To Varying

Transcript

Tuned Radio Frequency Superheterodyning Cell Phones Superheterodyning How Radios and Cell Phones Tune to Varying Frequencies Matthew Goldstein, KB1NCS MIT UHF/VHF Repeater Association October 16, 2008 Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem How to Tune to a Station Start with an antenna Electronic "Filters" can select frequency ranges Amplify the result Repeat until you have just your station Filters applied to a signal 50 45 40 35 30 25 20 15 10 5 0 100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.5 Frequency (MHz) Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem How to Tune to a Station Start with an antenna Electronic "Filters" can select frequency ranges Amplify the result Repeat until you have just your station Filters applied to a signal 50 45 40 35 30 25 20 15 10 5 0 100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.5 Frequency (MHz) Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem How to Tune to a Station Start with an antenna Electronic "Filters" can select frequency ranges Amplify the result Repeat until you have just your station Filters applied to a signal 100 90 80 70 60 50 40 30 20 10 0 100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.5 Frequency (MHz) Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem How to Tune to a Station Start with an antenna Electronic "Filters" can select frequency ranges Amplify the result Repeat until you have just your station Filters applied to a signal 100 90 80 70 60 50 40 30 20 10 0 100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.5 Frequency (MHz) Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem How to Tune to a Station Start with an antenna Electronic "Filters" can select frequency ranges Amplify the result Repeat until you have just your station Filters applied to a signal 100 90 80 70 60 50 40 30 20 10 0 100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.5 Frequency (MHz) Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem A Tuning Example Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem What if we Change Frequencies? Have to adjust every Filter Filters change selection range If only the frequency to the Filters never changed Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory Example Problem What if we Change Frequencies? Have to adjust every Filter Filters change selection range If only the frequency to the Filters never changed Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory FM Example How to Move the Frequencies Superheterodyning - Mixing Vacuum Tubes and Transistors Mix Frequencies Produce Sum and Difference Frequencies Generate a Local Frequency with Constant Offset Filter the Mixed Difference Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory FM Example How to Move the Frequencies Superheterodyning - Mixing Vacuum Tubes and Transistors Mix Frequencies Produce Sum and Difference Frequencies Generate a Local Frequency with Constant Offset Filter the Mixed Difference Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory FM Example How to Move the Frequencies Superheterodyning - Mixing Vacuum Tubes and Transistors Mix Frequencies Produce Sum and Difference Frequencies Generate a Local Frequency with Constant Offset Filter the Mixed Difference Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory FM Example What does this give us? Let’s Tune again to 101.1 Only have to set Local Frequency to 90.4 Filters are already tuned to 10.7 Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Theory FM Example What does this give us? Let’s Tune again to 101.1 Only have to set Local Frequency to 90.4 Filters are already tuned to 10.7 Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Processing High Frequencies Cell Phone Processors Cell phone signal frequencies are around 2GHz Fast processors are expensive To make Lower battery life Matthew Goldstein Superheterodyning Tuned Radio Frequency Superheterodyning Cell Phones Processing High Frequencies How Superheterodyning Helps It is often impractical to use frequencies as they are given. Particularly when they move or are too high Superheterodyning pretends you were given something else Matthew Goldstein Superheterodyning