Austein Concept

8/3/2019 Austein Concept

1/25

Tuned Radio Frequency

Superheterodyning

Cell Phones

SuperheterodyningHow Radios and Cell Phones Tune to Varying Frequencies

Matthew Goldstein, KB1NCS

MIT UHF/VHF Repeater Association

October 16, 2008

Matthew Goldstein Superheterodyning
http://goforward/http://find/http://goback/


2/25


Superheterodyning

Cell Phones

Theory

Example

Problem

How to Tune to a Station

Start with an antennaElectronic "Filters" can select frequency ranges

Amplify the result

Repeat until you have just your station

100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.50

5

10

15

20

25

30

35

40

45

50

Frequency (MHz)

Filters applied to a signal

http://find/http://goback/


3/25


Superheterodyning

Cell Phones

Theory

Example

Problem



Amplify the result


100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.50

5

10

15

20

25

30

35

40

45

50

Frequency (MHz)




4/25


Superheterodyning

Cell Phones

Theory

Example

Problem



Amplify the result


100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.50

10

20

30

40

50

60

70

80

90

100

Frequency (MHz)




5/25


Superheterodyning

Cell Phones

Theory

Example

Problem



Amplify the result


100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.50

10

20

30

40

50

60

70

80

90

100

Frequency (MHz)



T d R di F Th


6/25


Superheterodyning

Cell Phones

Theory

Example

Problem



Amplify the result


100.6 100.7 100.8 100.9 101 101.1 101.2 101.3 101.4 101.50

10

20

30

40

50

60

70

80

90

100

Frequency (MHz)



T d R di F Th


7/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example


Tuned Radio Frequency Theory


8/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example




9/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example




10/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example




11/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example




12/25


Superheterodyning

Cell Phones

Theory

Example

Problem

A Tuning Example




13/25

q y

Superheterodyning

Cell Phones

y

Example

Problem

A Tuning Example




14/25

q y

Superheterodyning

Cell Phones

y

Example

Problem

A Tuning Example




15/25

Superheterodyning

Cell Phones

Example

Problem

A Tuning Example



16/25


S h d i

Theory

E l


17/25

Superheterodyning

Cell Phones

Example

Problem

What if we Change Frequencies?

Have to adjust every FilterFilters change selection range

If only the frequency to the Filters never changed



S h t d i

Theory

E l


18/25

Superheterodyning

Cell Phones

Example

Problem

What if we Change Frequencies?

Have to adjust every FilterFilters change selection range

If only the frequency to the Filters never changed



SuperheterodyningTheory


19/25

Superheterodyning

Cell Phones

y

FM Example

How to Move the Frequencies

Superheterodyning - Mixing

Vacuum Tubes and Transistors Mix FrequenciesProduce Sum and Difference Frequencies

Generate a Local Frequency with Constant Offset

Filter the Mixed Difference



SuperheterodyningTheory


20/25

Superheterodyning

Cell PhonesFM Example







Tuned Radio FrequencySuperheterodyning

Theory


21/25

Superheterodyning









Theory


22/25

Superheterodyning


What does this give us?

Lets Tune again to 101.1

Only have to set Local Frequency to 90.4

Filters are already tuned to 10.7



Theory

FM E l


23/25

Superheterodyning


What does this give us?

Lets Tune again to 101.1

Only have to set Local Frequency to 90.4

Filters are already tuned to 10.7


Tuned Radio FrequencySuperheterodyning Processing High Frequencies


24/25

p y g

Cell Phones

g g q

Cell Phone Processors

Cell phone signal frequencies are around 2GHz

Fast processors are expensiveTo makeLower battery life


Tuned Radio FrequencySuperheterodyning Processing High Frequencies


25/25

p y g

Cell Phones

g g q

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


Documents

Austein Concept