| Summary: | This paper introduces an analog notch filtering-based coupling circuit for receivers in ultra-narrowband and narrowband power line communication systems, which are connected to low-voltage electric power grids. It is composed of a twin-T notch analog filter, which is responsible for imposing a significant attenuation on the main frequency (i.e., <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mn>0</mn></msub><mo>∈</mo><mrow><mo>{</mo><mn>50</mn><mo>,</mo><mn>60</mn><mo>}</mo></mrow></mrow></semantics></math></inline-formula> Hz) in cascade with an elliptic low-pass analog filter, designed with a 3 dB cut-off frequency of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mi>c</mi></msub><mo>≫</mo><msub><mi>f</mi><mn>0</mn></msub></mrow></semantics></math></inline-formula>. For <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mn>0</mn></msub><mo>=</mo><mn>60</mn></mrow></semantics></math></inline-formula> Hz and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mi>c</mi></msub><mo>=</mo><mn>2</mn></mrow></semantics></math></inline-formula> MHz, the prototype of the analog notch filtering-based coupling circuit attains attenuation values of 22 dB and less than 2 dB at the main frequency and in the rest of the frequency bandwidth, respectively, when practical scenarios are considered. Lastly, it shows that the analog notch filtering-based coupling circuit is more effective than a typical capacitive coupling circuit when frequencies lower than 3 kHz are considered for data communication and sensing purposes.
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