Abstract: A differential transmission line includes a positive conductor on which a positive complementary component of a differential signal is transmitted, and a negative conductor parallel to the positive conductor on which a negative complementary component of the differential signal is transmitted. A quarter wavelength differential coupler is inserted along a length of the positive and negative conductors. The quarter wavelength differential coupler has a length corresponding to a frequency of common mode noise on the positive and negative conductors. The quarter wavelength differential coupler reduces the common mode noise at the frequency as the differential signal passes through the quarter wavelength differential coupler.

Abstract: An optical element conveying human-discernible information to a user has its brightness modulated to also convey machine-discernible information to an optical detector. A frame section in which a bit of data can be conveyed begins at a falling edge of a preceding frame section corresponding to the brightness of the optical element decreasing to a low level. At a first predetermined point within the frame section, if the bit of data is logic one, the brightness is increased to a high level, corresponding to a rising edge. At a later, second predetermined point within the frame section, if the bit of data is logic zero, the brightness is increased to the high level, corresponding to the rising edge. At the end of the frame section, the brightness is decreased to the low level, corresponding to a falling edge of the frame section.

Abstract: A differential transmission line with a common mode notch filter includes adjacently arranged, repeating differential transmission line pair sections. The sections have lengths that are each equal to half of an electric wavelength of a lowest frequency of a common mode electromagnetic wave to be suppressed during transmission of an electric signal over the differential transmission line. Each section includes a pair of conductors separated from one another by a spacing. The width of each conductor and the spacing between the conductors of each section vary over the length thereof according to a same pattern such that at every point over the length of each section a differential mode impedance of the differential transmission line is identical. A common mode impedance of the differential transmission line changes periodically in accordance with the lengths of the sections.

Abstract: A differential transmission line includes a positive conductor on which a positive complementary component of a differential signal is transmitted, and a negative conductor parallel to the positive conductor on which a negative complementary component of the differential signal is transmitted. A quarter wavelength differential coupler is inserted along a length of the positive and negative conductors. The quarter wavelength differential coupler has a length corresponding to a frequency of common mode noise on the positive and negative conductors. The quarter wavelength differential coupler reduces the common mode noise at the frequency as the differential signal passes through the quarter wavelength differential coupler.

Abstract: An optical element conveying human-discernible information to a user has its brightness modulated to also convey machine-discernible information to an optical detector. A frame section in which a bit of data can be conveyed begins at a falling edge of a preceding frame section corresponding to the brightness of the optical element decreasing to a low level. At a first predetermined point within the frame section, if the bit of data is logic one, the brightness is increased to a high level, corresponding to a rising edge. At a later, second predetermined point within the frame section, if the bit of data is logic zero, the brightness is increased to the high level, corresponding to the rising edge. At the end of the frame section, the brightness is decreased to the low level, corresponding to a falling edge of the frame section.

Abstract: A differential transmission line with a common mode notch filter includes adjacently arranged, repeating differential transmission line pair sections. The sections have lengths that are each equal to half of an electric wavelength of a lowest frequency of a common mode electromagnetic wave to be suppressed during transmission of an electric signal over the differential transmission line. Each section includes a pair of conductors separated from one another by a spacing. The width of each conductor and the spacing between the conductors of each section vary over the length thereof according to a same pattern such that at every point over the length of each section a differential mode impedance of the differential transmission line is identical. A common mode impedance of the differential transmission line changes periodically in accordance with the lengths of the sections.