A polar decoder kernel comprising a processing unit having: at least one input configured to receive two input Logarithmic Likelihood Ratios, LLRs, (2202, 2203); logic circuit configured to manipulate the two input LLRs; and at least one output configured to output a manipulated LLR obtained by manipulating the two LLRs; wherein the polar decoder kernel is characterised in that the logic circuit of the processing unit comprises only a single two-input adder to manipulate the two input LLRs without employing a further adder for adding a logic '1' within a negation circuit operating in two's complement format, and the input LLRs and the manipulated LLR are in a format of a fixed-point number representation that comprises a two's complement binary number and an additional sign bit, wherein, when defining an 'f' function as: x̃ c = f ( x̃ a, x̃ b) = sign( x̃ a)sign( x̃ b)min(| x̃ a |, | x̃ b |), where sign(·) returns '-1' if its argument is negative and '+1' if its argument is positive; and defining a 'g' function as: x ̃ d = g x ̃ a x ̃ b u ^ a = − 1 u ^ a x ̃ a + x ̃ b the processing unit is configured to manipulate the two input LLRs by either (i) performing at an instant in time either a 'g' function or an 'f' function on the two input LLRs; or (ii) only ever performing one of: a 'g' function or an 'f' function, and wherein said format is represented using the fixed-point number representation having W+1 bits, as: x ̃ = − 1 x ̃ 0 ⋅ − 2 W − 1 x ̃ 1 + ∑ w = 2 W 2 W − w x ̃ w, where x̃ 0 is a label of the additional sign bit, x̃ 1 is a label of a bit that serves as both a most significant bit, MSB, and a sign bit of the two's complement binary number part of the fixed-point number representation, and x̃ W is a label of a least significant bit, LSB, of the two's complement binary number part of the fixed-point number representation. at least one input configured to receive two input Logarithmic Likelihood Ratios, LLRs, (2202, 2203); logic circuit configured to manipulate the two input LLRs; and at least one output configured to output a manipulated LLR obtained by manipulating the two LLRs; x̃ c = f ( x̃ a, x̃ b) = sign( x̃ a)sign( x̃ b)min(| x̃ a |, | x̃ b |), where sign(·) returns '-1' if its argument is negative and '+1' if its argument is positive; and defining a 'g' function as: x ̃ d = g x ̃ a x ̃ b u ^ a = − 1 u ^ a x ̃ a + x ̃ b the processing unit is configured to manipulate the two input LLRs by either (i) performing at an instant in time either a 'g' function or an 'f' function on the two input LLRs; or (ii) only ever performing one of: a 'g' function or an 'f' function, and wherein said format is represented using the fixed-point number representation having W+1 bits, as: x ̃ = − 1 x ̃ 0 ⋅ − 2 W − 1 x ̃ 1 + ∑ w = 2 W 2 W − w x ̃ w, where x̃ 0 is a label of the additional sign bit, x̃ 1 is a label of a bit that serves as both a most significant bit, MSB, and a sign bit of the two's complement binary number part of the fixed-point number representation, and x̃ W is a label of a least significant bit, LSB, of the two's complement binary number part of the fixed-point number representation. (i) performing at an instant in time either a 'g' function or an 'f' function on the two input LLRs; or (ii) only ever performing one of: a 'g' function or an 'f' function, and wherein said format is represented using the fixed-point number representation having W+1 bits, as: x ̃ = − 1 x ̃ 0 ⋅ − 2 W − 1 x ̃ 1 + ∑ w = 2 W 2 W − w x ̃ w, where x̃ 0 is a label of the additional sign bit, x̃ 1 is a label of a bit that serves as both a most significant bit, MSB, and a sign bit of the two's complement binary number part of the fixed-point number representation, and x̃ W is a label of a least significant bit, LSB, of the two's complement binary number part of the fixed-point number representation. x̃ 0 is a label of the additional sign bit, x̃ 1 is a label of a bit that serves as both a most significant bit, MSB, and a sign bit of the two's complement binary number part of the fixed-point number representation, and x̃ W is a label of a least significant bit, LSB, of the two's complement binary number part of the fixed-point number representation.