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Non-Ionizing Radiation Measurements for Trajectography Radars
J. Marcos Leal Barbosa Filho, Millena M. de M. Campos, Daniel L. Flor, William S. Alves, Adaildo G. D'Assunção, Marcio E. C. Rodrigues, Vicente A. de Sousa Jr
TL;DR
High-power, narrow-beam trajectography radar emissions raise exposure concerns, especially near public areas, yet the paper notes a lack of measurements for this radar type. It proposes a specific field-measurement method and finds that occupational limits are met everywhere, while the general-public limit is exceeded at one point near the antenna.
Problem
High-power, narrow-beam radar emissions raise exposure concerns, and the paper addresses the lack of measured NIR levels for trajectography radars.
Source: §1 · pp. 1–2Method
The study proposes a specific method for measuring trajectography-radar power density and directs the receiving antenna toward the radar for measurements where possible.
Source: §3.3 · p. 7, §5 · p. 11Results
All measured power-density values are below the occupational limit, but the general-public limit is exceeded at one point near the Béarn antenna.
Source: §5 · p. 11Takeaways & Limitations
General-public access should be restricted near the Béarn antenna, and workers should receive risk guidance and have their time in the surrounding area controlled.
Source: §5 · p. 11Predictions assume 0.851 kW average transmitter power and 44 dBi gain; the maximum-density estimate assumes an on-axis beam focused at infinity with no reflections.
Source: §4.2 · p. 10
Abstract
from arXiv · showhide
This work presents a Non-Ionizing Radiation (NIR) measurement campaign and proposes a specific measurement method for trajectography radars. This kind of radar has a high gain narrow beam antenna and emits a high power signal. Power density measurements from a C-band trajectography radar are carried out using bench equipment and a directional receiving antenna, instead of the commonly used isotropic probe. The measured power density levels are assessed for compliance test via comparison with the occupational and general public exposure limit levels of both the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Brazilian National Telecommunication Agency (Anatel). The limit for the occupational public is respected everywhere, evidencing the safe operation of the studied radar. However, the limit for the general public is exceeded at a point next to the radar's antenna, showing that preventive measures are needed.
1. Introduction
Trajectography radars concentrate high-power non-ionizing radiation in narrow beams, prompting concern about exposure near public areas. The paper addresses the lack of trajectography-radar measurements with a radar-specific method designed to isolate its emissions and compare exposure with established limits.
1. Introduction
- High-power emissions concentrated in narrow beams create an unusual exposure scenario and raise health concerns, particularly in public areas.The authors identify a need to measure exposure for both people working with the radar and visitors, then compare measurements with ICNIRP and Anatel limits.Source: §1 · pp. 1–2
- Because exposure is compared against ICNIRP and Anatel limits, the measurements can inform preventive and control measures.The introduction frames this comparison as relevant to both radar workers and visitors.Source: §1 · p. 2
- The study measures Béarn radar emissions at CLBI, including a point 690 m from a museum visited daily by the public.Béarn operates at higher power than the base’s Adour radar; the study aims to measure only radar emissions and reports no prior NIR-level records for CLBI.Source: §1 · p. 2
1.1. Related Works
- Only three prior contributions measured NIR from radars, and none studied trajectography radars, according to the authors’ Scopus survey.Those earlier radar measurement studies concerned air-traffic-control and shipboard-navigation radars.Source: §1.1 · p. 2
- Common isotropic-probe measurements suit rotating or scanning radars but make it impracticable to isolate a pointed trajectography radar’s signal amid other transmitters.The authors note mobile-communication base stations’ third-harmonic signals at CLBI and propose a specific method for this radar type.Source: §1.1 · pp. 2–3
2. Regulation of Human Exposure Limits to Non-Ioninzing Radiation
This section outlines the radiofrequency exposure framework used to assess the radar’s measured power density. It distinguishes occupational from general-public limits and focuses the assessment on average power density.
2. Regulation of Human Exposure Limits to Non-Ioninzing Radiation
- The section distinguishes non-ionizing radiation’s thermal effects from non-thermal effects, for which it reports no evidence of danger to human health, particularly for long-term exposure.Thermal effects are attributed to increased vibration in material molecules caused by NIR.Source: §2 · p. 3
- Brazil’s Anatel Act No. 458 sets radiofrequency exposure limits from 8.3 kHz to 300 GHz and defines evaluation and licensing procedures.Brazilian law directs exposure limits to follow WHO recommendations, which adopted ICNIRP values.Source: §2 · p. 3
- For 2–300 GHz, the stated power-density limits are less than 10 W/m² for the general population and 50 W/m² for occupational exposure.Occupational exposure applies to people exposed through work who know of the potential exposure and can control their time at the location or adopt preventive measures.Source: §2 · p. 3
- The paper assesses average power density because the radar’s 1 MW peak power is 1,000 times its average power and is within the suggested pulse-averaged limit.The text notes limited information on biological effects of peak pulsed fields and describes the suggested level for frequencies above 10 MHz.Source: §2 · pp. 3–4
3. Materials and Methods
The method isolates trajectography-radar emissions using a directional receiving antenna and frequency-selective measurements, then evaluates measured power density against predictions and exposure limits. The campaign selects four sites with likely exposure and people present, and bench tests confirm key radar-signal properties and measurement equipment performance.
3.1. Proposed Method
- The proposed workflow selects a directional antenna and frequency-selective power measurement, then chooses exposure-relevant sites, validates equipment, measures average power density, predicts levels, and compares results with exposure limits.Measurements are taken over 6 min according to Anatel and ICNIRP instructions.Source: §3.1 · p. 4, Figure 1 · p. 4
3.2. Measurement Scenario
- The four sites include radar operator instruments, a space museum, and a mobile launch platform, at distances of 9, 960, 690, and 1570 m, respectively.Sites were chosen for likely exposure and presence of people.Source: §3.2 · p. 5, Figure 2 · p. 5
- P01 is the sole near-field point; the other three are far-field, while vegetation blocks line of sight to P03.The calculated near-/far-field boundary is 618.67 m, leaving only P01 within the near field.Source: §3.2 · pp. 6–7
3.3. Measurement Setup
- A 22 dBi directional antenna and spectrum analyzer restrict reception by direction and frequency, enabling radar-specific measurements; P01 was measured from a side lobe because the radar antenna could not point lower.At P01, the desired and lowest possible radar-antenna elevations differ by 16.43°; measurements used vertical polarization at 1.60 m and averaged power over 6 min.Source: §3.3 · p. 7
3.4. Bench Tests
- 0.851 kW average transmitted power (59.3 dBm) was measured, 0.7 dB below specification, with the carrier frequency confirmed at 5800 MHz.Bench tests also confirmed a 1.7 µs pulse width and 1.707 ms pulse repetition period; a simulated radar-like signal and power meter were used to check analyzer readings.Source: §3.4 · pp. 7–8, Figure 7 · p. 8
3.5. Equipment
- All equipment was calibrated before each measurement campaign, and the paper lists the equipment used.The equipment list is presented in Table 2.Source: §3.5 · p. 8, Table 2 · p. 8
4. Results and Discussion
The section reports measured power-density calculations and scenario-specific predictions, then compares measurements with predictions and exposure limits. All measured points meet the occupational limit, but P01 exceeds the general-population limit.
4.1. Measurement Results
- At P01, the spectrum analyzer measures average signal power; instrument attenuation and offset are used to calculate receiving-terminal power, then power density, with calculated values reported in Tables 3 and 4.Source: §4.1 · pp. 8–9, Figure 8 · p. 9, Table 3 · p. 9
4.2. Predictions
- Far-field predictions for P02–P04 use a free-space model with 0.851 kW average transmit power and 44 dBi antenna gain, while near-field P01 uses a maximum-density estimate.For the near-field estimate, if predicted density reaches or exceeds the maximum permissible exposure, the authors assume that level may occur anywhere in the near-field region.Source: §4.2 · pp. 9–10
4.3.1. Measurements and Predictions
- At P01, measured power density is considerably below the predicted on-axis maximum because the measurement point is misaligned with the antenna axis.Source: §4.3.1 · p. 10
- Predicted and measured values are very close at P02 and P04, where line-of-sight conditions leave no meaningful attenuation beyond free-space propagation.The authors relate this agreement to the static link, directional receiving antenna, and very narrow transmitting beam.Source: §4.3.1 · p. 10
- At P03, the measured value is 96.44% far from the prediction, which the authors attribute to vegetation shadowing on a non-line-of-sight path.Source: §4.3.1 · p. 10
4.3.2. Measurements and Limits
- 50 W/m2 occupational limit is met at every measurement point, but P01 exceeds the 10 W/m2 general-population limit.The authors state that general-population access to P01 should be restricted and that occupational exposure there requires warnings and controlled permanence time.Source: §4.3.2 · p. 10
5. Conclusions
The conclusions report a radar-specific NIR measurement campaign and identify a near-antenna public-exposure exceedance. They call for restricting public access there and using preventive measures for occupational exposure.
5. Conclusions
- The work proposes a specific method for measuring trajectography-radar NIR power density and reports previously unpublished measurement results.Source: §5 · p. 11
- The setup isolates radar emissions using the spectrum analyzer’s channel-power function and a directional receiving antenna across four points: three far-field and one near-field.Source: §5 · p. 11
- All measured values meet the occupational limit, but the general-population limit is exceeded near Béarn’s antenna, prompting access restrictions and occupational risk guidance and time controls.The authors note that CLBI already performs the occupational preventive actions for its radars.Source: §5 · p. 11