Re: TI-H: cellular phone
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Re: TI-H: cellular phone
>acctualy i was just going to ask if anyone knew what the heck a bandpass
>filter does , beacause thers one in here and it looks cool :) anyone know?
There are basically four types of filters that go into this grouping.
Low-Pass
High-Pass
Band-Pass
Band-Reject
A Low-Pass filter passes all the frequencies BELOW a specified level. This
type of filter would be used in say a speaker crossover. Say you wanted to
pass everything below 500 Hz to a subwoofer, you would use a Low-Pass filter.
A High-Pass filter passes all the frequencies ABOVE a specified level.
Let's use a speaker crossover for an example again... You want to pass all
the flutes, and clarinets to your tweeter. Say everything above 5KHz
A Band-Pass filter will pass all the frequencies between two specified
frequencies. This would be like putting the 300 Hz - 4KHz to your midrange.
This is also used in telephone systems. A voice Grade Channel (VGC) is
0-4KHz. Now you could use a Low-Pass filter to pass all the frequencies
below 4KHz, but the human voice generally falls within 300 - 3.4KHz, so you
would use a Band-Pass filter for 300-3.4KHz (This also allows the 3.4 -
3.835KHz portion to be used for Out of Band signalling, while leaving room
for guardbands, but this is all telephone related stuff (Sorry I got
sidetracked))
and finally, the Band-Reject filter. This filter is used in almost all
power supplys that convert A.C. to D.C. (as in your computer) The power in
the states is 60 cycle (It's 50Hz here in Japan), and if you didn't filter
out that 60Hz, it would bleed over into the circuitry. This would cause a
hum in any audio recordings you made etc...
There are many more types of filters (Half-wave rectifiers, Clampers,
Limiters etc... I hope I answered your question...
p.s. My homepage will be done shortly, and it will have all sorts of info
like this on it... Frequency Spectrums, Propagation, Satellite
communications, L.O.S., Troposcatter, information on resistors, caps,
diodes, Frequency Modulation, Amplitude Modulation, multiplexing,
directional couplers, Farraday effect, attenuators, amplifiers, Fiber
Optics and a bunch more... I just have to get off my lazy butt and finish it.
ldgregory@biogate.com
Dedicated to providing you with more information
than you needed to know.