# implementing complex multiplication in simulink

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amuka anurag on 20 Apr 2021
Edited: Kiran Kintali on 10 May 2023
how to build the complex mulitplication block with total 4 inputs(2 real,2 imaginary)

Pratheek Punchathody on 23 Apr 2021
Using the MATLAB Function block, we can create a complex multiplication block with the required number of inputs.
Create a functional block in simulink, by double clicking on this function block write the below function which takes 2 real inputs and 2 imaginary inputs.
function y = fcn(a,b,c,d) %a,c are real inputs and b,d are imaginary inputs
c1=complex(a,b);
c2=complex(c,d);
y = c1*c2; % performing multiplication
end
The following MATLAB function block is created with 2 real inputs and 2 imaginary inputs. The multiplication operation of the two complex numbers are performed and the output is shown with the variable y.
Hope this helps..!
Walter Roberson on 9 May 2023
Have you happened to explore using a Product block in Matrix mode with complex signals ?
Philipp Raffael Diel on 9 May 2023
Yes I have. Since I saw, that the results were different from my Matlab reference code, I figured the product block (matrix multiplication mode) doesn't work for complex signals.

Kiran Kintali on 9 May 2023
For HDL Code Generation you can use the Simulink and MATLAB function examples shown below.
These examples use FPGA/ASIC friendly full precision intermediate products in the complex multiplication.
>> Simulink start page / HDL Coder templates section
>> eml_design_patterns
Philipp Raffael Diel on 10 May 2023
Thank you very much!
Is there also an example for complex multiplication of matrices?
Kiran Kintali on 10 May 2023
Edited: Kiran Kintali on 10 May 2023
Here are few product examples for your reference that can be modified for your use.
HDL Coder has several examples. Can you share more details on your requirements?
Are you looking for streaming (sample by sample) implementation to be done on FPGA/ASIC ? Do you need Floating-point or fixed-point precision? Are some of the inputs constants (like state space matrix compuation), if yes, is the data sparse or dense? Is the data source stored on the internal memory or external memory? What is the context in which matrix multiplication be used?

Walter Roberson on 9 May 2023
You can use blocks to combine each real component with its corresponding imaginary component. Then you can use a Product block https://www.mathworks.com/help/simulink/slref/product.html . Just be sure not to set the output signal type to Inherit: Keep MSB, or to Inherit: Match Scaling, as those two do not support complex signals.