Choose an occupancy radar’s PCB antenna layout from the installed viewing geometry first. A wall-mounted sensor looking across a room and a ceiling-mounted sensor looking downward do not need the same angular coverage or the same balance of horizontal and vertical resolution. The laminate and antenna artwork must support those requirements, but neither establishes the final detection area by itself.
This article uses a hypothetical room to build a coverage worksheet. The calculated angles are geometric requirements, not measured antenna patterns, guaranteed detection ranges or a qualified reference design.
Define the monitored volume before selecting an aperture
Draw the required detection area, excluded areas and possible mounting positions. Record ceiling height, sensor height, tilt, doors, furniture and nearby metal. Define whether the product must detect a walking person, retain occupancy while someone sits quietly, or separate two people. Those are different acceptance tasks.
Use room coordinates for the installation drawing and antenna coordinates for radiation-pattern data. Mark the sensor’s boresight, both board axes and its rotation in the enclosure. After tilting the board, a horizontal room direction no longer corresponds automatically to an antenna’s principal-plane plot.
TI’s placement and angle application brief recommends selecting the antenna layout together with room dimensions, mounting height and orientation. Its ISK and ODS examples emphasize different distributions of virtual antenna positions for wall and overhead installations. Treat these as starting architectures; the room and required behavior still determine the choice.
Worked example: a ceiling sensor above a 4 m by 3 m zone
Assume a sensor at the center of a rectangular zone, 3.0 m above the floor, pointing straight down. The zone extends 2.0 m on either side along x and 1.5 m along y. Ignore obstructions for this first calculation. Let z be a horizontal target-plane height and d = 3.0 m minus z.
The full geometric spans in the two principal cuts are 2 arctan(2.0/d) and 2 arctan(1.5/d). Convert the results to degrees. At a corner, the horizontal offset is the square root of (2.0 squared plus 1.5 squared), or 2.5 m. The corner’s angle away from downward boresight is arctan(2.5/d), and its slant range is the square root of (2.5 squared plus d squared).
| Target plane z | Distance d | Full x-cut span | Full y-cut span | Corner off-boresight angle |
|---|---|---|---|---|
| 0 m: floor reference | 3.0 m | 67.4° | 53.1° | 39.8° |
| 1.2 m: illustrative body plane | 1.8 m | 96.0° | 79.6° | 54.2° |
| 1.7 m: higher illustrative plane | 1.3 m | 114.0° | 98.2° | 62.5° |
At z = 1.2 m, the corner slant range is about 3.08 m. A footprint drawn only on the floor would therefore understate the angular coverage needed at this higher plane. The chosen heights are teaching inputs; a person is a distributed, changing radar target rather than a flat reflector at one fixed height.
The corner check also prevents another mistake: passing two principal cuts does not prove coverage throughout the rectangular zone. Inspect the full three-dimensional pattern at the corner directions, then test the actual occupants and room. A quoted field of view is not necessarily a circular cone or a rectangular boundary with uniform sensitivity.
Compare a wall mount using the same zone
Now place the hypothetical sensor at the middle of the 3 m wall, 2.4 m high. For an initial centerline calculation, consider the z = 1.2 m plane from 1 m to 4 m in front of the wall. The required downward sightline angles are arctan(1.2/1) = 50.2° at the near point and arctan(1.2/4) = 16.7° at the far point.
That is a 33.5° centerline vertical interval. Pointing halfway between these angles, about 33.4° downward, centers the interval geometrically; it does not optimize received signal strength. The near edge spanning the full 3 m width needs about 112.6° of horizontal projected coverage before accounting for tilt. The corner directions must then be transformed into the tilted antenna coordinates.
This example excludes the first meter from its calculation. If the requirement includes people directly below or beside the sensor, add those points explicitly. A wall mount can trade overhead coverage problems for a near-sensor blind zone or occlusion behind another person. Keep both mounting options until the measured coverage map supports a decision.
Distinguish coverage, array resolution and software behavior
TI’s IWR6843ISK overview describes an antenna with a much wider azimuth field of view than elevation field of view. Its IWR6843ISK-ODS overview describes wide coverage in both axes. These provide a useful architectural comparison for evaluating a wall-facing or overhead arrangement. Use the exact hardware revision, pattern definition and demo configuration when comparing them.
Keep three requirements separate in the design record:
- Coverage: sufficient transmitted and received response in the required directions.
- Angular discrimination: the array geometry and processing needed to distinguish targets at different angles.
- Occupancy behavior: the application’s entry detection, persistence, exit timing and false-trigger performance.
A wide pattern cannot establish two-person separation, and a point cloud does not automatically establish reliable stationary occupancy. TI’s people-counting reference design includes both radar hardware and detection/tracking processing, illustrating why the finished application must be assessed as a system. The array antenna reference introduces the related aperture and feed-network considerations.
Turn the viewing requirement into a PCB and housing specification
Reserve space for radiators, feed routing, the required reference conductor, connectors and mounting hardware together. Preserve the antenna topology’s specified ground structure; do not apply a generic instruction to remove all copper beneath a patch antenna. Define board-edge distance and metal clearances from the modeled antenna and enclosure geometry, rather than copying a clearance from an unrelated frequency band.
The patch-antenna calculator can supply a first dimensional estimate under its assumptions. It does not validate a multi-channel radar aperture, coupling, housing or field of view. Plan electromagnetic analysis and an assembled prototype before releasing custom artwork.
Use the material-selection guide to document dielectric construction, copper, thickness tolerance and fabrication needs. If considering RO4830 Plus, read its manufacturer data sheet: it targets 76–81 GHz radar applications and reports design Dk at 77 GHz. That characterization does not independently validate a 60 GHz occupancy-sensor design. Obtain appropriate inputs and verify the actual antenna construction.
When comparing candidate feed constructions, use the laminate-upgrade loss-budget worksheet to identify the loss a material change could recover. A lower-loss feed does not by itself correct the aperture’s viewing geometry.
Include the final bracket, screws, housing wall, coating and cables in the prototype review. TI’s radome design guide examines material, thickness, spacing and angle-dependent effects. Compare bare-board and assembled patterns across the required directions. A boresight-only check can miss an enclosure-induced problem near the zone boundary.
Release against a coverage map and a repeatable test
Before testing, set product-specific limits for missed detections, entry latency, occupancy retention, vacancy delay and unwanted detections outside the zone. Do not substitute a universal pass percentage. Record firmware, radar configuration, mounting coordinates and housing revision so a later test is comparable.
| Test location or action | What to record | Question answered |
|---|---|---|
| Center, edges and every corner | Repeated entry paths, body orientation and detection latency | Does coverage extend throughout the required zone? |
| Seated and standing pauses | Occupancy output over the required dwell time | Does occupancy persist during quiet activity? |
| Two people and furniture | Occlusion cases and any required target separation | Which situations create blind zones or merged tracks? |
| Doorway and adjacent corridor | False triggers, boundary crossings and vacancy delay | Are unwanted areas excluded in the finished installation? |
Mark failures on the room drawing and repeat after changing position, tilt, antenna or configuration. Preserve the original results. Software boundaries can reject detections outside the intended area, but they do not restore a missing RF path inside it.
Review your occupancy sensor antenna layout
Send the floor coverage sketch, mounting height and tilt, antenna artwork, stackup, operating band and housing CAD. Include required occupant behaviors, excluded areas and any measured blind zones. Request an occupancy-radar PCB review, or organize the board and prototype requirements with the RFQ checklist builder.