An eye diagram visualizes signal integrity by overlaying many periods of a digital signal onto a single time window spanning 1-2 unit intervals (UI). The overlapping traces form a characteristic eye-shaped opening whose height, width, and clarity reveal signal quality metrics such as jitter, noise, and inter-symbol interference (ISI). A wide-open eye indicates clean signal transmission, while a closed or blurred eye signals degradation.
#' anyplot.ai
#' eye-diagram-basic: Signal Integrity Eye Diagram
#' Library: ggplot2 3.5.1 | R 4.4.1
#' Quality: 92/100 | Created: 2026-06-18
library(ggplot2)
library(ragg)
set.seed(42)
# Theme tokens (Imprint palette, theme-adaptive chrome)
THEME <- Sys.getenv("ANYPLOT_THEME", "light")
PAGE_BG <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
ELEVATED_BG <- if (THEME == "light") "#FFFDF6" else "#242420"
INK <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
INK_SOFT <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
INK_MUTED <- if (THEME == "light") "#6B6A63" else "#A8A79F"
# NRZ simulation parameters
n_bits <- 600
samp_per_ui <- 100
noise_sigma <- 0.05 # Gaussian noise (5% of amplitude)
jitter_sigma <- 0.03 # Timing jitter std dev (3% of UI)
sigmoid_k <- 18 # Bandwidth-limiting sharpness
# Random bit stream and per-transition jitter
bits <- sample(c(0L, 1L), n_bits, replace = TRUE)
jitter_raw <- rnorm(n_bits - 1L, 0.0, jitter_sigma)
j_arr <- c(0.0, jitter_raw)
# Vectorized waveform generation with sigmoid transitions and jitter
n_total <- n_bits * samp_per_ui
t_all <- (seq_len(n_total) - 0.5) / samp_per_ui
bit_idx <- pmin(as.integer(floor(t_all)) + 1L, n_bits)
t_within <- t_all - floor(t_all)
prev_bits <- c(bits[1L], bits[-n_bits])
prev_at_t <- prev_bits[bit_idx]
curr_at_t <- bits[bit_idx]
j_vals <- j_arr[bit_idx]
dt <- (t_within - j_vals) * sigmoid_k
sig_s <- 1.0 / (1.0 + exp(-dt))
same <- (prev_at_t == curr_at_t)
rise <- (!same & curr_at_t > prev_at_t)
v_sig <- ifelse(same, curr_at_t * 1.0, ifelse(rise, sig_s, 1.0 - sig_s))
v_sig <- v_sig + rnorm(n_total, 0.0, noise_sigma)
# Fold waveform into 2-UI eye traces (start at each bit boundary)
window_sz <- 2L * samp_per_ui
n_traces <- n_bits - 2L
t_axis <- seq(0.0, 2.0, length.out = window_sz + 1L)[-1L]
start_idx <- (seq_len(n_traces) - 1L) * samp_per_ui + 1L
samp_mat <- outer(0L:(window_sz - 1L), start_idx, `+`)
eye_df <- data.frame(
time = rep(t_axis, n_traces),
voltage = v_sig[as.vector(samp_mat)]
)
# Pre-compute 2D density grid: vectorised findInterval + tabulate → geom_raster
n_bins_x <- 200
n_bins_y <- 150
t_breaks <- seq(0.0, 2.0, length.out = n_bins_x + 1L)
v_breaks <- seq(-0.18, 1.18, length.out = n_bins_y + 1L)
t_mids <- (t_breaks[-1L] + t_breaks[-length(t_breaks)]) / 2
v_mids <- (v_breaks[-1L] + v_breaks[-length(v_breaks)]) / 2
t_bin_idx <- pmin(pmax(findInterval(eye_df$time, t_breaks), 1L), n_bins_x)
v_bin_idx <- pmin(pmax(findInterval(eye_df$voltage, v_breaks), 1L), n_bins_y)
lin_idx <- (t_bin_idx - 1L) * n_bins_y + v_bin_idx
count_vec <- tabulate(lin_idx, nbins = n_bins_x * n_bins_y)
# Full rectangular grid required for geom_raster interpolation;
# zero-count cells → NA so scale maps them to PAGE_BG (eye opening shows through)
raster_df <- data.frame(
time = rep(t_mids, each = n_bins_y),
voltage = rep(v_mids, times = n_bins_x),
density = ifelse(count_vec > 0L, sqrt(count_vec), NA_real_)
)
# Estimate eye opening at optimal sampling point (t ≈ 1.5 UI, centre of second eye)
at_center <- eye_df$time >= 1.40 & eye_df$time <= 1.60
center_v <- eye_df$voltage[at_center]
low_level <- center_v[center_v < 0.5]
high_level <- center_v[center_v > 0.5]
eye_lo <- if (length(low_level) > 10L) as.numeric(quantile(low_level, 0.995)) else 0.15
eye_hi <- if (length(high_level) > 10L) as.numeric(quantile(high_level, 0.005)) else 0.85
eye_ht_mv <- max(0L, round((eye_hi - eye_lo) * 1000L))
plot_title <- "eye-diagram-basic · r · ggplot2 · anyplot.ai"
p <- ggplot(raster_df, aes(x = time, y = voltage)) +
# Smooth density heatmap via bilinear-interpolated raster (publication-quality)
geom_raster(aes(fill = density), interpolate = TRUE) +
# Optimal sampling point (t=0.5, centre of first eye) — vertical dashed reference
annotate("segment", x = 0.5, xend = 0.5,
y = min(v_breaks), yend = max(v_breaks),
color = INK_MUTED, linewidth = 0.45, linetype = "dashed") +
# Eye height bracket: bracket bar + serif ticks + measurement label
annotate("segment", x = 1.72, xend = 1.72, y = eye_lo, yend = eye_hi,
color = "#AE3030", linewidth = 0.6) +
annotate("segment", x = 1.70, xend = 1.74, y = eye_lo, yend = eye_lo,
color = "#AE3030", linewidth = 0.5) +
annotate("segment", x = 1.70, xend = 1.74, y = eye_hi, yend = eye_hi,
color = "#AE3030", linewidth = 0.5) +
annotate("text", x = 1.76, y = (eye_lo + eye_hi) / 2,
label = paste0(eye_ht_mv, " mV"),
color = "#AE3030", size = 2.5, hjust = 0.0, fontface = "bold") +
scale_fill_gradient(
name = "Density",
low = "#009E73",
high = "#4467A3",
na.value = PAGE_BG,
guide = guide_colorbar(barwidth = 0.5, barheight = 8)
) +
scale_x_continuous(
name = "Time (UI)",
breaks = c(0.0, 0.5, 1.0, 1.5, 2.0),
expand = c(0.04, 0.0)
) +
scale_y_continuous(
name = "Voltage (V)",
breaks = c(0.0, 0.25, 0.5, 0.75, 1.0),
expand = c(0.06, 0.0)
) +
coord_cartesian(clip = "off") +
labs(title = plot_title) +
theme_minimal(base_size = 8) +
theme(
plot.background = element_rect(fill = PAGE_BG, color = PAGE_BG),
panel.background = element_rect(fill = PAGE_BG, color = NA),
panel.grid.major = element_line(color = INK_MUTED, linewidth = 0.15),
panel.grid.minor = element_blank(),
panel.border = element_rect(fill = NA, color = INK_SOFT, linewidth = 0.4),
axis.title = element_text(color = INK, size = 10),
axis.text = element_text(color = INK_SOFT, size = 8),
plot.title = element_text(color = INK, size = 12, hjust = 0.0),
legend.background = element_rect(fill = ELEVATED_BG, color = INK_SOFT, linewidth = 0.3),
legend.text = element_text(color = INK_SOFT, size = 8),
legend.title = element_text(color = INK, size = 9),
legend.position = "right",
plot.margin = margin(12, 20, 12, 12, "pt")
)
ggsave(
filename = sprintf("plot-%s.png", THEME),
plot = p,
device = ragg::agg_png,
width = 8,
height = 4.5,
units = "in",
dpi = 400
)
Part of Signal Integrity Eye Diagram on anyplot.ai.