270-GHz Radiator Module for Eight-Way Incoherent Power Combining of InP HBT Oscillators

This article presents a metallic radiator module, $11.5\times 5.6\times 2.5$ cm3 in size, designed to direct terahertz power with a 26° circularly symmetric radiation beam. The module combines the power from eight identical integrated oscillator chips in free space using a linear array of built-in circular horns with 17-dB gain. The oscillators operating at unlocked frequencies produce an average power of 3.5 dBm within the 268–274 GHz range. When all elements are activated, the radiator module maintains the same radiation patterns as the individual elements, achieving a total radiated power of 12.5 dBm, which represents an eightfold increase from the average power per element.

I. Introduction

The security imaging systems for detecting concealed objects have become a major application of terahertz integrated circuits [1]. While the performance of passive systems, which detect self-generated thermal emissions from target objects, has greatly improved due to the development of low-noise amplifiers [2], active systems combining terahertz emission sources with detector arrays offer superior image quality. Currently, near-distance imaging systems that operate in transmission mode—where the target is placed between the source and the detector array—are available as commercial products. For instance, Terasense produces terahertz cameras featuring GaAs heterostructure detector arrays with a noise equivalent power (NEP) of 1 nW/Hz^0.5, paired with 100-GHz 80-mW Impatt-diode sources emitting from diagonal horns. Additionally, the National Optics Institute (INO) provides uncooled microbolometer focal-plane arrays, combined with terahertz lasers that output 4 mW at 282 GHz.