Simple Question

[Philip Newman]

Consider a simple band-pass filter. The bandwidth can be considered as the
frequency range between the lower frequency limit and the upper frequency
limit, where each limit occurs at -3dB down either side of the filter.
This -3dB point corresponds to the half-power point.

What is the mathematical relationship between -3dB and half-power??

Phil

 

[Jim Thompson]

On Fri, 21 May 2004 17:21:52 +0100, "Philip Newman"
<nojunkmail@ntlworld.com> wrote:

Consider a simple band-pass filter. The bandwidth can be considered as the
frequency range between the lower frequency limit and the upper frequency
limit, where each limit occurs at -3dB down either side of the filter.
This -3dB point corresponds to the half-power point.

What is the mathematical relationship between -3dB and half-power??

Phil

Homework ?

dB = 20xLOG10(VoltageRatio)

or VoltageRatio = 10^(dB/20)

dB = 10xLOG10(PowerRatio)

or PowerRatio = 10^(dB/10)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Philip Newman]

"Jim Thompson" <thegreatone@example.com> wrote in message
news:cabsa05mbail3douosqr4nq54t4vveg1qt@4ax.com...

On Fri, 21 May 2004 17:21:52 +0100, "Philip Newman"
nojunkmail@ntlworld.com> wrote:

Consider a simple band-pass filter. The bandwidth can be considered as
the
frequency range between the lower frequency limit and the upper frequency
limit, where each limit occurs at -3dB down either side of the filter.
This -3dB point corresponds to the half-power point.

What is the mathematical relationship between -3dB and half-power??

Phil


Homework ?

no, just a stupid question

-3~10log(0.5)

d'oh!

see subject heading - simple question. understated i think