Jaco Verpoorte

Novel Ring Resonator-Based Integrated Photonic Beamformer for Broadband Phased Array Receive Antennas—Part I: Design and Performance Analysis

A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beamforming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical conversion is performed by means of single-sideband suppressed carrier modulation, employing a common laser, Mach-Zehnder modulators, and a common optical sideband filter after the OBFN. The unmodulated laser signal is then re-injected in order to perform balanced coherent optical detection, for the opto-electrical conversion. This scheme minimizes the requirements on the complexity of the OBFN, and has potential for compact realization by means of full integration on chip. The impact of the optical beamformer concept on the performance of the full receiver system is analyzed, by modeling the combination of the PAA and the beamformer as an equivalent two-port RF system. The results are illustrated by a numerical example of a PAA receiver for satellite TV reception, showing that - when properly designed - the beamformer hardly affects the sensitivity of the receiver.

Conformal phased array with beam forming for airborne satellite communication

For enhanced communication on board of aircraft novel antenna systems with broadband satellite-based capabilities are required. The installation of such systems on board of aircraft requires the development of a very low-profile aircraft antenna, which can point to satellites anywhere in the upper hemisphere. To this end, phased array antennas which are conformal to the aircraft fuselage are attractive. In this paper two key aspects of conformal phased array antenna arrays are addressed: the development of a broadband Ku-band antenna and the beam synthesis for conformal array antennas. The antenna elements of the conformal array are stacked patch antennas with dual linear polarization which have sufficient bandwidth. For beam forming synthesis a method based on a truncated singular value decomposition is proposed.

On-chip microwave photonic beamformer circuits operating with phase modulation and direct detection

We propose and experimentally demonstrate the working principles of two novel microwave photonic (MWP) beamformer circuits operating with phase modulation (PM) and direct detection (DD). The proposed circuits incorporate two major signal processing functionalities, namely a broadband beamforming network employing ring resonator-based delay lines and an optical sideband manipulator that renders the circuit outputs equivalent to those of intensity-modulated MWP beamformers. These functionalities allow the system to employ low-circuit-complexity modulators and detectors, which brings significant benefits on the system construction cost and operation stability. The functionalities of the proposed MWP beamformer circuits were verified in experimental demonstrations performed on two sample circuits realized in Si(3)N(4)/SiO(2) waveguide technology. The measurements exhibit a 2 × 1 beamforming effect for an instantaneous RF transmission band of 3‒7 GHz, which is, to our best knowledge, the first verification of on-chip MWP beamformer circuits operating with PM and DD.

Finite Element Model for the Computation of the Transfer Impedance of Cable Shields

The transfer impedance of a cable shield is a parameter that characterizes its shielding effectiveness. To calculate this parameter, we can use analytical or semiempirical approaches but, in this study, the objective is to adapt a general-purpose finite element formulation. The advantage of a numerical method is that it can be applied to a wider variety of situations, where complex geometries and materials may be present. To obtain numerically the transfer impedance, we first express it as a function of the electric field and then we compute the field by means of the finite element method. The only input data required in the process are the geometry and the material properties of the shield. To validate our numerical model, we apply it to a few cable shields and compare the results of the simulations with analytical models and measurements obtained from the literature.

Broadband optical beam forming for airborne phased array antenna

For enhanced communication on board aircraft, novel antenna systems with broadband satellite-based capabilities are required. The technology will enhance airline operations by providing in-flight connectivity for flight crew information and will bring live TV and high-speed Internet connectivity to passengers. The installation of such systems on board aircraft requires for aerodynamic reasons the development a very low-profile aircraft antenna, which can point to satellites anywhere in the upper hemisphere. Major keystones for the success of steerable low-profile antennas are multi-layer printed circuit boards (PCBs) with an array of broadband antenna elements, and compact micro-wave systems with appropriate beam steering capabilities. The present paper describes the development of a prototype 8x1 optical beam forming network using cascades of optical ring resonators as part of a breadboard Ku-band phased array antenna.

Development of dual-frequency airborne Satcom antenna with optical beamforming

For enhanced communication on board aircraft, novel antenna systems with broadband satellite-based capabilities are required. The amount of data agglomerated over a range of passenger services (VoIP, Web, Email, SMS, MMS) and over a range of flights, appears highly asymmetrical. The inbound traffic is about 5 times higher than the outbound. The inbound traffic requires the availability of a broadband Ku-band antenna in receive mode only. The outbound traffic services can be supplied by the Inmarsat SBB link, which requires the installation of an L-band transmit antenna. In order to avoid both the installation of L-band antenna and Ku-band antenna, the concept of a hybrid dual-frequency antenna operating both L-band and Ku-band is being explored in this paper.

Development of the SANDRA antenna for airborne satellite communication

Novel avionics communication systems are required for increasing flight safety and operational integrity, for optimizing economy of operations and for enhancing passenger services. One of the key technologies to be developed is an antenna system that will provide broadband connectivity within aircraft cabins at an affordable price. This paper describes the development of an electronically steered Ku-band phased array antenna with low aerodynamic profile. The antenna front-end consists of at least 1800 antenna elements, of which the beam has to be steered continuously to geostationary satellites. Best performance for the beam steering is expected from a hybrid architecture with small sub-apertures having their local own beamformers (using phase shifters). The beamformer to steer the sub-apertures of the entire antenna uses True Time Delays with an optical ring resonator. 1 2

Development of a broadband and squint-free Ku-band phased array antenna system for airborne satellite communications

Novel avionic communication systems are required for various purposes, for example to increase the flight safety and operational integrity as well as to enhance the quality of service to passengers on board. To serve these purposes, a key technology that is essential to be developed is an antenna system that can provide broadband connectivity within aircraft cabins at an affordable price. Currently, in the European Commission (EC) 7th Framework Programme SANDRA project (SANDRA, 2011), a development of such an antenna system is being carried out. The system is an electronically-steered phased-array antenna (PAA) with a low aerodynamic profile. The reception of digital video broadcasting by satellite (DVB-S) signal which is in the frequency range of 10.7-12.75 GHz (Ku-band) is being considered. In order to ensure the quality of service provided to the passengers, the developed antenna should be able to receive the entire DVB-S band at once while complying with the requirements of the DVB-S system (Morello & Mignone, 2006). These requirements, as will be explained later, dictate a broadband antenna system where the beam is squint-free, i.e. no variation of beam pointing direction for all the frequencies in the desired band. Additionally, to track the satellite, the seamless tunability of the beam pointing direction of this antenna is also required. In this work, a concept of optical beamforming (Riza & Thompson, 1997) is implemented to provide a squint-free beam over the entire Ku-band for all the desired pointing directions. The optical beamformer itself consists of continuously tunable optical delay lines that enable seamless tunability of the beam pointing direction.

Hole inductance in braided cable shields

The shielding effectiveness of metal braids of cables is governed by the geometry and the materials of the braid. The shielding effectiveness can be characterised by the transfer impedance of the metal braid. Analytical models for the transfer impedance contain in general two components, one representing diffusion of electromagnetic energy through the metal braid, and a second part representing leakage of magnetic fields through the braid. The second part is a local phenomenon, which again has three parts: hole inductance, braid inductance and skin inductance. The hole inductance is governed by the penetration of magnetic fields through the apertures of the braid. Well-known analytical models overestimate the contribution of the hole inductance by a factor two. This can be easily corrected by multiplying the hole inductance terms by a factor (2/π)3/2.

Smart Antennas in aerospace applications

The interest in Smart Antennas for aerospace applications is growing. This paper describes smart antennas which can be used on aircraft. Two aerospace applications are discussed in more detail: a phased array antenna with optical beam forming and a large vibrating phased array antenna with electronic compensation techniques.