If the impedances in the two circuits differ, then the power ratio must be corrected for that difference.
The same formula and conditions apply to the determination of a power ratio from a ratio of currents. Vi/v2 is the ratio of RMS voltages across two circuit elements of equal resistance, or in the case of identical signal shapes in the two circuits, such as sine waves, the ratio of voltage amplitudes across two circuits having equal complex-valued impedances, and This definition of a power ratio, in units of decibels, assumes equal impedances in the two circuits: In two circuits of equal impedance, the ratio of their powers may be determined as the square of the ratios of the voltages. Transmission period ( drawing not to scale)įigure 1.1-The power spectral density of random data signal has nulls at multiples of the data rates and a maximum effective bandwidth related to its rise and fall time. T 10_90% in this example is 11200th of the data At knee frequency the 1 spectrum lies 6.8 dB
frequency 1 Eye pattern of data signalġ010. The frequency 0.35/t10_90% Hz may better approximate the meat of the spectrum associated with a rising edge.ġ.2 POWER RATIOS The decibel equivalent for any power ratio isĠ Power-average of many data sequences (thick line)ĭata transmission. The knee frequency, !knee ~ 0.5/ !10_90% Hz, is a crude estimate of the highest frequency content within a particular digital signal. He frequently conducts technical workshops for digital engineers at Oxford University and other sites worldwide: DR. He is the featured Signal Integrity columnist for EDN Magazine and Chief Technical Editor of IEEE 802.3 standards for Fast Ethernet and Gigabit Ethernet. HOWARD JOHNSON has accumulated 30 years of experience in digital design, consulting with engineers all over the world. Packed with new examples and never-before-published high-speed design guidance, this book offers a complete and unified theory of signal propagation for all baseband digital media, from pcb traces to cables to chips. HIGH-SPEED SIGNAL PROPAGATION ADVANCED BLACK MAGIC Howard Johnson and Martin Graham present state-of-the-art techniques for building digital interconnections that transmit faster, farther, and more efficiently than ever before.
For all the PCB designers and circuit designers out there, buy it' read iC keep it" - Dan Baumgartner, Printed Circwt Design ".one of the finest efforts to come along in the field of applied high-speed digital design because of its focus on providing tools for the whole design team bringing a high-speed product to life. Raves for Johnson and Graham's previous classic, High-Speed Digital Design: A Handbook of Black Magic
HIGH-SPEED SIGNAL -PROPAGATION ADVANCED BLACK MAGIC
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