122 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 11, NO. 1, JANUARY 1999 Compact Photonic Integrated Phase and Amplitude Controller for Phased-Array Antennas J. Stulemeijer, F. E. van Vliet, Member, IEEE, K. W. Benoist, D. H. P. Maat, and M. K. Smit, Associate Member, IEEE Abstract— Feasibility of an extremely compact photonic in- tegrated circuit for controlling phase and amplitude of a 16- element phased-array microwave antenna has been demonstrated experimentally. Index Terms— Beam steering, integrated optics, optical phase shifters, optical waveguides, phased-array radar. I. INTRODUCTION P HASED-ARRAY antennas have been used since the be- ginning of the 1970’s and are now becoming increasingly important in satellite and mobile communications. A draw- back for broad application of phased-array antennas is the large volume and weight of the RF electronic beam-forming network. Photonics holds a great promise for reducing both weight and volume of these networks. Many experiments have been reported based on discrete optical components [1]–[3]. First integrated circuits were realized on lithium niobate, see [4] and [5]. In this paper we report the first experiments on an InP-based integrated beam-forming network with extremely small dimensions (8.5 8 mm ) for controlling phase and amplitude of a 16-element RF phased-array antenna. InP has the advantage that it allows for integration of high extinction electroabsorption modulators and optical amplifiers for com- pensating on-chip losses in large circuits. Further device size can be much smaller as compared with lithium niobate. II. OPERATION PRINCIPLE Using a coherent detection scheme phase and amplitude of an optical signal can be directly transferred to a microwave signal by mixing this signal with an optical local oscillator signal. In this way, modulation of phase and amplitude of a microwave signal can be performed using optical phase and amplitude modulators, which provides the module with an almost unlimited bandwidth; phase and amplitude modulation efficiency is flat in a frequency range from a couple of MHz up to tens of GHz (only limited by the photo-detector). Fig. 1 illustrates the schematic of the photonic beam control network, which has been realized. The optical chip is shown within the dotted box. The chip has two inputs for two optical signals, one Manuscript received July 15, 1998; revised October 12, 1998. J. Stulemeijer and M. K. Smit are with the Department of Information Technology and Systems, TTT Laboratory, Integrated Photonics Group, Delft University of Technology, 2600 GA Delft, The Netherlands. F. E. van Vliet and K. W. Benoist are with TNO-Physics and Electronics Laboratory, 2509 JG The Hague, The Netherlands. D. H. P. Maat is with the Delft University of Technology, Department of Applied Physics, 2600 GA Delft, The Netherlands. Publisher Item Identifier S 1041-1135(99)00377-8. Fig. 1. Schematic view of the optical control of a phased-array antenna. Fig. 2. Layer-stack. of which is modulated with the radar pulse. The two inputs are fed to two 1 16 power splitting networks, which are overlapping in such a way that every output of the first network is situated next to an output of the second network. Each pair is connected to a phase and amplitude modulation section, after which the two signals are fed to a 3-dB coupler. The RF- signals are obtained by coupling the signals coming out of the sixteen 3-dB couplers to a series of 16 balanced detector pairs. In the following we will discuss the design and performance of the different elements. III. FABRICATION We developed our circuit in a MOVPE grown InP– InGaAsP–InP double-heterostructure as usual for operation in the long wavelength window (1550 nm) for optical commu- nication, see Fig. 2. 1041–1135/99$10.00  1999 IEEE