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# Low pass fir filter with non-unity gain

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

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.

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

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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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.

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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