Image Response Calculator

Image Response

Calculate local oscillator frequency, f_LO, and image frequency, f_ci, for a heterodyne receiver.

Select unit format: Select conversion:

Intermediate frequency, f_IF:

Carrier frequency, f_c:

Select relation:

f_LO =
f_ci =

Fill out the fields, you can use SI suffixes in your numbers e.g. 10k would be 10 kilo. Capitalization matter, as 1m would be 1 milli and 1M would be 1 mega. Finally, press the "Calculate" button to get the answer.

A sketch for one of the typical situations in downconversion receivers is shown below:

Frequency translation by heterodyning with f_LO > f_c . Image response creation.

Calculations are based on the following formulas:

for downconversion (f_IF< f_c):

if f_LO > f_c, then f_LO = f_c + f_IF and f_ci = f_c + 2f_IF;
if f_LO < f_c, then f_LO = f_c - f_IF and f_ci = f_c - 2f_IF.

for upconversion (f_IF> f_c):

if f_LO > f_IF, then f_LO = f_c + f_IF and f_ci = f_c + 2f_IF;
if f_LO < f_IF, then f_LO = f_IF - f_c and f_ci = 2f_IF - f_c.