For this example the coefficients are signed with a coefficient width of 18 bits and a coefficient fractional width of 19 bits, or Fix18_19. The specified coefficients range between -0.000256022 and +0.182865845.
An integer coefficient width of 18 bits gives a maximum positive value of 131071 and a maximum negative number of -131072. Considering the fractional bits, this gives a maximum representable positive number of 131071/(2^19)=0.249998092 and a maximum representable negative number of 131072/(2^19)=0.25. The scaling factor is determined by dividing the maximum value that can be represented (for the specified number of coefficient bits) by the maximum coefficient value. In this case 0.249998092/0.182865845=1.367112009 (=+2.716081962dB).
IMPORTANT: While some performance improvement can be achieved by using the full dynamic range of the coefficient bit width, you must be satisfied that any changes are acceptable using the frequency response plot. You must also account for any additional gain introduced by coefficient scaling elsewhere in the application system. In many systems, signal scaling can be arbitrary and no gain compensation is required; where scaling is necessary, it is often desirable to amalgamate gains inherent in a signal processing chain and compensate or adjust for these gains either at the front end (for example, in an Automatic Gain Control circuit) or the back end (for example, in a Constellation Decoder unit) of the chain. If you do not want to introduce any additional scaling into the design, select Quantize Only .