Rail RFID Read Window Engineer V5

1. Enter antenna height, train-window distance, window heights, yaw and pitch.
2. Use Basic mode for a simple project demonstration, or Engineering mode for the RF inputs.
3. Choose component-based transmitter power or direct EIRP. Do not enter cable loss twice.
4. Enter each tag position and sensitivity. X is perpendicular to the track, Y is along-track, and Z is above top of rail.
5. Review the 3D, Top, Side and Window Footprint views.
6. Review forward-link, reverse-link and limiting margins in Link Budget.
7. Enter train speed and run the animation. Review the Read Timeline and indicative inventory opportunities.
8. During field testing, enter measured RSSI or import a Sargas CSV and calibrate the planning model.
9. Save the project preset and print the report.

• Shows a rounded directional antenna main lobe, optional HPBW construction guide and calculated operational volumes.
• Calculates full 3D tag distance and horizontal/vertical offset relative to antenna yaw, pitch and roll.
• Separately checks tag activation on the forward link and backscatter reception on the reverse link.
• Applies off-axis antenna loss, polarization mismatch, glass loss, feeder loss, environmental fade allowance and calibration.
• Classifies tags as Strong, Good, Marginal, Unlikely or Outside display range.
• Simulates straight-line train movement and estimates available read time and inventory opportunities.
• Imports common Sargas CSV read logs and summarizes RSSI.
• Saves versioned local JSON presets and prints a project report.

Component-based mode

EIRP = conducted power - TX feeder loss + TX antenna gain.

Direct EIRP mode

Enter EIRP directly. The application disables transmitted-path component fields to avoid deducting feeder loss twice.

Circular polarization applies a first-order 3 dB mismatch when coupled to a linearly polarized label. Linear polarization uses the tag rotation and tilt to estimate mismatch. A tag near 90 degrees misalignment can suffer severe loss.

Glass losses are one-way assumptions. Standard, tinted, UV/IR, heated and metallised choices are indicative only. Use Custom after measuring the actual train window. Metal framing near a tag can detune the label and is not explicitly solved.

• Rounded antenna pattern: a smooth normalized main-lobe visualization fitted to horizontal and vertical HPBW. It illustrates gradual fall-off and is not a fixed read distance.
• Reliable volume: green calculated surface where the selected reference tag meets the configured required design margin.
• Marginal volume: amber calculated surface where the theoretical link is at or above threshold but below the required design margin.
• HPBW angle guide: optional pyramid-like construction lines. This is retained only to explain the entered beam angles.

The calculated volumes use the same pattern-loss function as tag classification. This keeps the 3D, Top, Side, Window and Link Budget results consistent.

3D

Drag to orbit, use the mouse wheel to zoom and Shift+drag to pan. The train window is a translucent plane. Tag colour indicates the operational result.

Top

Plan view of perpendicular X distance and along-track Y position. Curved contours show gradual horizontal pattern fall-off.

Side

Elevation view using X distance and Z height above top of rail. Use this view to set antenna height and pitch against the window band.

Window footprint

Looks directly at the train side and shows the boresight-centred footprint on the window plane.

Read timeline

Plots predicted backscatter level while the train passes. The dashed line is reader sensitivity plus design margin.

Link budget

Shows forward margin, reverse margin, limiting margin, time proxy, inventory opportunities and acceptance review.

Use the detailed table to identify the limiting cause: insufficient tag power, weak reverse response, off-axis loss, polarization loss, glass loss, fade allowance or insufficient moving-read opportunities.

d = sqrt(X² + Y² + (Z - antenna height)²)

FSPL = 32.44 + 20 log10(f MHz) + 20 log10(d km)

The normalized Gaussian pattern is fitted so the combined relative loss is approximately 3 dB on the entered HPBW contour.

Power at tag = EIRP - FSPL - pattern loss - polarization loss - glass loss - fade allowance

Forward margin = power at tag - tag activation sensitivity

Backscatter at reader = power at tag + tag backscatter factor - return FSPL - return losses + RX gain - RX feed loss + calibration

Reverse margin = backscatter at reader - reader sensitivity

Overall margin = minimum(forward margin, reverse margin)

The train follows a straight line along Y. The application estimates nominal time in the horizontal coverage width from speed and geometry, then divides by the configured inventory-opportunity duration. This is indicative only. Reader firmware, encoding, session, Q, tag population, interference and EPC length affect real inventory timing.

Use Required reads/pass and Minimum readable time as project acceptance inputs. A PASS is still subject to field verification.

1. Install the actual antenna, cable, reader and representative label.
2. Record antenna height, standoff, tag coordinates, power setting, frequency and glass type.
3. Collect multiple readings at a fixed point. Use median RSSI rather than one instantaneous result.
4. Enter the measured median RSSI against Tag 1 and select Calibrate.
5. Repeat at additional locations and compare measured versus predicted values.
6. Do not force one calibration offset to hide a wrong power, gain, cable-loss or coordinate input.
7. Retain a realistic fade margin after calibration.
8. Validate using points that were not used for calibration and perform moving-train passes at the maximum design speed.

The importer reads a local CSV and searches headings containing RSSI, Time, EPC or Tag. It reports valid row count and minimum, median, mean and maximum RSSI. Data stays in the browser and is not uploaded. If no numeric RSSI column is detected, rename the column to include “RSSI”.

Save Preset creates a schema-versioned JSON file containing the current project fields. Load Preset validates that a values object exists and ignores unknown fields. Print Report uses the browser print system and can be saved as PDF. Export PNG captures the current 3D canvas.

• Tag inside HPBW but Unlikely: HPBW is not a read guarantee. Check forward/reverse margins, glass, polarization and sensitivities.
• Results are extremely strong or weak: check whether EIRP and component-based power have been mixed and confirm units.
• Blank or distorted view: reset the camera, reload the file in current Chrome or Edge and verify browser zoom.
• No CSV results: confirm comma-delimited text and an RSSI heading containing numeric values.
• Preset rejected: use an unmodified JSON preset created by this application.
• Different result from field test: verify cable loss, glass, tag location and orientation, then calibrate using median RSSI.

RAIN RFID: passive UHF RFID ecosystem. EPC Gen2: common air-interface protocol. EIRP: effective isotropic radiated power. dBm: absolute RF power. dB: gain or loss ratio. dBi: antenna gain relative to an isotropic radiator. RSSI: reader-reported received signal indicator. HPBW: half-power beamwidth. Boresight: peak-direction axis. Forward link: reader to tag. Reverse link: tag backscatter to reader. Link margin: predicted level above the required threshold. Fade margin: allowance for uncertainty and environmental variation.

• Straight, level railway and fixed window plane.
• Smooth planning pattern based on entered HPBW, not a full-wave electromagnetic solution or exact installed XC-AF26 pattern.
• No exact metal-frame detuning, train-body current, diffraction, Fresnel obstruction or deterministic multipath solution.
• Glass, tag sensitivity, reader sensitivity and backscatter factor must be confirmed for the real hardware.
• Operational volumes are tag-specific. If Tag 1 and Tag 2 parameters differ, visible volumes use Tag 1 as the reference and each marker retains its own result.
• Field verification remains mandatory.