Using capacitors to block DC while passing AC signals. Common in high-speed interfaces like PCIe, USB, and HDMI to allow different DC bias levels between transmitter and receiver.
The copper pad area surrounding a drilled hole in a PCB. Minimum annular ring is typically 4-6 mils for reliable manufacturing.
Removing unused via stub to reduce signal reflections and improve high-frequency performance. Essential for signals above 5 Gbps.
The frequency range over which a signal or system operates effectively. Higher data rates require wider bandwidth.
The ratio of voltage to current for a wave traveling along a transmission line. Determined by trace geometry and dielectric properties. Common values: 50Ω single-ended, 100Ω differential.
Unwanted coupling between adjacent signal traces. NEXT (Near-End) occurs at the source, FEXT (Far-End) at the receiver. Minimize with proper spacing and ground shielding.
Transmission line with ground planes on either side of the signal trace on the same layer. Offers good impedance control and EMI performance.
Measure of a material's ability to store electrical energy. FR-4 Dk ≈ 4.2-4.5. Lower Dk means faster signal propagation.
Two traces carrying complementary signals (equal amplitude, opposite polarity). Provides noise immunity and reduced EMI. Common in USB, PCIe, HDMI, Ethernet.
Measure of signal energy lost as heat in the dielectric. Lower Df means less loss. FR-4 Df ≈ 0.02, Megtron 6 Df ≈ 0.004.
The speed of signal transition from low to high (rise time) or high to low (fall time). Faster edges contain higher frequency content and require more careful SI design.
Oscilloscope display showing signal quality by overlaying many bit transitions. A wide, open 'eye' indicates good signal integrity.
Crosstalk measured at the far end of the victim trace. Increases with trace length and coupling. Dominant in stripline configurations.
Standard glass-reinforced epoxy laminate for PCBs. Dk ≈ 4.2-4.5, Df ≈ 0.02. Suitable for signals up to ~3 Gbps.
DDR memory routing where clock and command signals pass sequentially through each DRAM. Creates intentional skew compensated during training.
Voltage fluctuation on ground due to simultaneous switching of multiple outputs. Causes false triggering. Mitigate with proper decoupling.
Continuous copper layer providing signal return path and shielding. Essential for controlled impedance and EMI reduction.
PCB technology using microvias, fine traces, and thin materials for compact designs. Common in mobile devices and advanced packaging.
Opposition to AC current flow, measured in ohms. Controlled impedance traces are designed to specific values (50Ω, 75Ω, 100Ω) for signal integrity.
Signal power lost as it travels through a transmission line. Expressed in dB. Increases with frequency and trace length.
When one bit affects adjacent bits due to channel bandwidth limitations. Visible as eye closure. Compensated with equalization.
Timing variation in signal edges from ideal positions. Measured in picoseconds. Causes bit errors at high data rates.
Ensuring signal traces have equal electrical length for timing. Critical for parallel buses (DDR), differential pairs, and clock distribution.
Differential signaling standard using 350mV swing. Low power, high speed, reduced EMI. Common in displays and high-speed data links.
Transmission line with trace on outer layer above a ground plane. Easy to manufacture but has higher radiation than stripline.
Small blind via (typically ≤6 mils) connecting adjacent layers. Lower inductance than through-hole vias. Used in HDI designs.
Crosstalk measured at the near end (source side) of the victim trace. Dominant in microstrip. Reduce with spacing and ground shielding.
Half the data rate frequency. For 10 Gbps signal, Nyquist is 5 GHz. Channel must support this frequency for proper operation.
Termination resistors integrated into IC die. Eliminates need for external resistors. Common in DDR memory interfaces.
4-level Pulse Amplitude Modulation encoding 2 bits per symbol. Doubles data rate vs NRZ. Used in 100G+ Ethernet and PCIe 6.0.
Partially cured fiberglass/resin material used between copper layers in PCB stackup. Becomes rigid after lamination.
Signal power reflected back to source due to impedance mismatch. Expressed in negative dB. Better than -10dB typically required.
Time for signal to transition from 10% to 90% of final value. Shorter rise times require higher bandwidth channels.
Brand of high-performance PTFE-based laminates. Low loss, stable Dk. Used in RF, microwave, and high-speed digital applications.
Scattering parameters describing high-frequency behavior. S21 is insertion loss, S11 is return loss. Used for channel characterization.
AC current concentrating near conductor surface at high frequencies. Increases resistance and loss. More pronounced at higher frequencies.
Transmission line with trace between two ground planes. Better shielding than microstrip but harder to route. Lower crosstalk.
Unterminated trace branch causing reflections. Via stubs from unused barrel length. Remove with back-drilling for high-speed signals.
Measurement technique sending pulse down trace and analyzing reflections. Used to find impedance discontinuities and measure trace impedance.
Transition Minimized Differential Signaling used in HDMI and DVI. Encoding reduces transitions for lower EMI.
Trace designed with controlled impedance for high-frequency signals. Required when trace length > 1/6 of signal wavelength.
Plated hole connecting copper layers. Types: through-hole (all layers), blind (surface to inner), buried (inner layers only).
Unused portion of through-hole via extending past signal layer. Creates resonance and reflections. Remove with back-drilling.
Impedance variation due to fiberglass weave pattern in PCB laminate. Can cause skew in differential pairs. Mitigate with rotated routing.