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Low pass fir filter with non-unity gain

up vote 14 down vote favorite

In my filter specs, the passband gain is given as 6.02db. How do I achieve this?

Usually all texts give the passband gain as 0db (as well as passband ripples if any).

2 Answers

up vote 4 down vote accept

This simply means that you have a non-unity gain in the passband. The number 6.02 in decibels corresponds to a multiplicative gain factor of two. You can check it like so:

$$10^\tfrac{6.02}{20} = 2 $$

All you have to do then is multiply all you FIR filter coefficients by 2.

up vote 3 down vote

Just multiply your FIR coefficients by 2. You can verify your passband gain at DC by setting $z=1$ which amounts to just summing the coefficients.


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Low pass fir filter with non-unity gain

up vote 14 down vote

In my filter specs, the passband gain is given as 6.02db. How do I achieve this?

Usually all texts give the passband gain as 0db (as well as passband ripples if any).


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up vote 9 down vote

This simply means that you have a non-unity gain in the passband. The number 6.02 in decibels corresponds to a multiplicative gain factor of two. You can check it like so:

$$10^\tfrac{6.02}{20} = 2 $$

All you have to do then is multiply all you FIR filter coefficients by 2.

edit

It should be $10^{\frac{6.02}{20}} = 2$ because we're talking dBs. - Matt L. Apr 25 '13 at 10:35

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