Ensuring maximum convective heat dissipation from a transmit/receive module of an active phased array antenna

The development of modern radio equipment is driven by multifunctionality, increased stealth, electronic integration, information richness, reliability, and manufacturability. The increasing saturation of equipment with electronics has made it possible to reduce the dimensions of transmit/receive modules (TRM) in active phased array antenna (APAA), but this has led to higher packaging density and, consequently, higher specific heat generation. Elevated temperatures can cause malfunction or failure of electronic components, making thermal management and temperature field redistribution inside TRM critically important. A common solution is the use of a heat sink operating under natural convection. Under the size and weight constraints of a TRM, selecting a heat sink fin cross‑section that provides the largest possible surface area to enhance convective heat dissipation becomes essential.

This work aims to determine the geometric shape of the heat sink fin (cross‑section) that maximizes convective heat dissipation for TRM in APAA.

A comparison criterion is introduced – the ratio of the perimeter of an equilateral triangle to the perimeter of a given shape under equal areas. The equilateral triangle is chosen as the reference because it has one of the smallest perimeters for a fixed area. When, the equilateral triangle has a larger perimeter; when, the shape under consideration has a larger perimeter.

The analysis of various cross-sectional shapes (circle, square, regular polygon, ellipse, rectangle, isosceles triangle) shows that for non-elongated shapes – circle, square, regular polygon – the perimeter is smaller than that of the equilateral triangle (). For elongated shapes – ellipse, rectangle, isosceles triangle – as the elongation parameter increases, the perimeter grows without limit compared to the equilateral triangle, and tends to zero.

Threshold values of the elongation parameter at which elongated shapes begin to outperform the equilateral triangle are determined. For the rectangle and ellipse, these thresholds lie within a certain range; for the isosceles triangle, the perimeter exceeds that of the equilateral triangle for any elongation greater than unity.

A comparison among elongated shapes under the same elongation and equal area shows that the isosceles triangle provides the largest perimeter, while the rectangle has a larger perimeter than the ellipse up to a certain elongation value; beyond that value, the ellipse exhibits a larger perimeter.

Considering manufacturability, the rectangular base is selected for practical implementation. Six design variants, differing by the arrangement of material relative to the central axis, are examined. Variants with additional transverse elements yield the largest perimeter increase but require advanced manufacturing methods such as additive technologies. Variants with internal cavities create closed volumes that hinder air circulation and are therefore considered unsuitable. One particular variant is found to be technologically feasible, providing a noticeable perimeter increase compared to the baseline configuration while remaining compatible with conventional mechanical processing.

The obtained analytical dependencies allow, at the design stage, a substantiated choice of the heat sink fin cross-section geometry – including the selection between non-elongated and elongated shapes, the necessary degree of elongation, and the optimal rectangular-based configuration – to ensure maximum convective heat dissipation for TRM in APAA.