Antenna Remoting Research Articles

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

A photonic architecture for remote multi-parameter measurement and transmission of microwave signals is proposed and demonstrated, which utilizes a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) in the antenna unit and a dual-drive Mach-Zehnder modulator (DDMZM) in the processing unit. Doppler frequency shift (DFS) and angle of arrival (AOA) can be determined by analyzing the down-converted intermediate frequency signals. Introducing a reference signal in the processing unit ensures DFS measurement without directional ambiguity. The proposed architecture can also be applied for instantaneous frequency measurement based on down-conversion. Due to the use of optical single sideband modulation, long-distance transmission of radio frequency (RF) signals without dispersion-induced power fading can be achieved. Experiments for accurate and stable DFS and AOA measurement as well as long-distance RF signal transmission with dispersion-induced power fading are presented. The approach avoids the use of optical filters and polarization-related devices, facilitating wideband and stable operation, which is highly desirable. The proposed architecture is a potential solution for microwave photonic antenna remoting, offering support for both remote transmission and multi-parameter measurement.

Electronic System of Remote Optical Control of LiNbO3 Mach-Zehnder Modulator Operating Point

A system for integrated optical LiNbO3 Mach–Zehnder modulator operating point remote control and stabilization was developed. It consisted of a conventional telecom photodiode and a passive electronic circuit at the bias input of the modulator. Light from an amplitude-modulated laser was used to remotely set the output voltage of the electronic circuit at the bias input of the Mach–Zehnder modulator. Information regarding the current operating point that had been provided with feedback system implementation was taken from DC values of high frequency photodetector currents. Efficient remote control of the modulator operating point over 1 km of a single-mode optical fiber, which multiplexes an optical carrier at 1550 nm and a low frequency control signal with a peak power of 2 mW at 1310 nm, was demonstrated. The results could be of interest for antenna remoting, radio-over-fiber (RoF) technology, and other applications with broadband optical transmission from remote sources in a distributed network.

All-Optical In-Phase/Quadrature Microwave Mixer for Antenna Remoting Applications

A new microwave photonic signal processing structure for realising in-phase/quadrature (I/Q) mixing is presented. It is based on a dual-drive Mach Zehnder modulator (DDMZM) and an optical phase modulator inside a Sagnac loop interferometer. Two output IF signals with a quadrature phase difference are obtained by using two photodetectors to detect the upper and lower sidebands of the optical signal at the Sagnac loop output. A quadrature phase difference in the two IF signals is realised by biasing the DDMZM at the quadrature point. This has the advantage of very little quadrature phase errors as a standard modulator bias controller can accurately lock the DDMZM bias point. The optical phase modulator driven by an RF signal can be placed in a remote location for antenna remoting. Theoretical analysis and simulation show using the proposed I/Q mixer for image rejection can overcome the modulation index dependent image rejection ratio problem in the reported I/Q mixers based on a cascaded modulator structure. The Sagnac loop based I/Q mixer is experimentally verified with results show only ±1° quadrature phase error and more than 50 dB image rejection ratio over the operating frequency range of 6 to 20 GHz.

500 GHz plasmonic Mach-Zehnder modulator enabling sub-THz microwave photonics

Broadband electro-optic intensity modulators are essential to convert electrical signals to the optical domain. The growing interest in terahertz wireless applications demands modulators with frequency responses to the sub-terahertz range, high power handling, and very low nonlinear distortions, simultaneously. However, a modulator with all those characteristics has not been demonstrated to date. Here, we experimentally demonstrate that plasmonic modulators do not trade-off any performance parameter, featuring—at the same time—a short length of tens of micrometers, record-high flat frequency response beyond 500 GHz, high power handling, and high linearity, and we use them to create a sub-terahertz radio-over-fiber analog optical link. These devices have the potential to become a new tool in the general field of microwave photonics, making the sub-terahertz range accessible to, e.g., 5G wireless communications, antenna remoting, Internet of Things, sensing, and more.

Conversion for the Better: A Broadband Highly Efficient Microwave Photonics Detector

Optical fibers have many advant ages over traditional electrical cables and interconnects when it comes to transmitting high-frequency signals. These advantages include lower loss, higher bandwidth, immunity to electromagnetic interference, and lower power consumption. It is due to these advantages that fiber optic links have found widespread use in applications such as radioover-fiber and antenna remoting, where coaxial cable loss increases prohibitively versus frequency.

A Colorless Remote Antenna Unit for Bidirectional Photonic Antenna Remoting

A colorless (wavelength-independent) remote antenna unit (RAU) for bidirectional photonic antenna remoting is proposed and demonstrated, which is based on a reflective semiconductor optical amplifier electroabsorption modulator (SOA-EAM). Due to the gain saturation effect in the semiconductor optical amplifier (SOA) of the reflective SOA-EAM, the microwave signal carried by the downlink optical signal is received and effectively erased. Then, the electroabsorption modulator (EAM) converts the uplink RF signal to an optical signal, which is reflected back to the center office (CO) by the high-reflection coated facet of the device to provide the uplink service. No signal downconversion is needed since the modulation bandwidth of the EAM can reach tens of GHz. A proof-of-concept experiment is carried out. The RAU performs well in a bidirectional radio over fiber (ROF) system for providing 500 Mb/s wireless services centered at 2 GHz.

Switching between positive and negative permeability by photoconductive coupling for modulation of electromagnetic radiation

We introduce a modulation mechanism for negative index materials (NIM) in the GHz frequency range by means of photoconductive coupling. This leads the way to a monolithically integrated modulable NIM achieved by conventional microfabrication techniques. The photosensitive material is deposited in the gap of the split ring resonator (SRR) structure and the response in terms of S-parameters is simulated using a high frequency structure simulator (HFSSTM) program. Only a single SRR particle is simulated to demonstrate total suppression of resonance amplitude and without any loss of generality the concept is applicable to a NIM comprising of both negative permeability and negative permittivity. This simple modulation of refractive indices can lead to novel optical device developments with the potential to dramatically improve the performance of existing phased array antennas, optical beam-forming networks, antenna remoting and transportation of RF power through fiber.

Optical Generation of mm-Wave Signal with Wide Linewidth Lasers for Broadband Communications

In future generation space based phased array antennas, pico-cellular broadband communication systems and antenna remoting, optical techniques using optical flber, laser diodes and photo-detectors for transport electrical signals are widely used. Interest in the deployment of optical flbers arises from the low transmission loss compared to electrical media. Aside this, optical flbers are small, ∞exible, lightweight, and they have good phase accuracy and very large bandwidth. In view of the use of laser diodes and photo-detectors in the link, it is expected that the system costs can be considerably reduced if these optical devices are used for the generation of mm-wave signals so that no mm-wave oscillator and modulator are required. The problem is to use large linewidth lasers to generate mm-wave signal with desired spectral purity. This paper suggests a solution. DOI: 10.2529/PIERSxxxxxxxxxxxx

Dynamic range of vertical-cavity surface-emitting lasers in multimode links

We report spurious-free dynamic-range measurements of 850-nm vertical-cavity surface-emitting lasers in short multimode links for radio frequency communication. For a 27 m fiber link, the dynamic range at optimal bias was greater than 95 dBHz/sup 2/3/ for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free-space link, we have measured the highest dynamic range in an 850-nm vertical-cavity surface-emitting laser of 113 dB Hz/sup 1/3/ at 900 MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

High-Performance Fiber-Optic Link for Electronic Countermeasure Antenna Remoting

The ability to remotely radiate microwave signals has become an essential feature of modern electronic countermeasure (ECM) systems. The use of fiber optics allows remote microwave links to be constructed that have very low propagation loss and dispersion, are very flexible and light in weight, and have a high degree of immunity from external electromagnetic fields, cross talk, and environmental effects. This combination of desirable characteristics is beneficial to avionic ECM antenna remoting as well as many other applications. GEC-Marconi has developed high-per formance fiber components for use in a towed radar decoy. The resulting rugged and compact optical transmitter and receiver modules have been proven to maintain the required performance over the full hostile range of environmental conditions en countered on a fast jet. Packaged fiber-optic links have been produced that can achieve a compression dynamic range of 87 dB in a 1-MHz bandwidth over a 2- to 18-GHz range.

Low-cost, high performance optoelectronic components for antenna remoting

We describe a demonstration of a system in which we incorporated components developed as part of the DARPA Analog Optoelectronic Module Technology Project (TRP). The goal of the TRP program was to bring to manufacturability fiber optic components whose specifications are adequate for both military and commercial applications but whose cost is substantially less than the presently available components. We demonstrated the functionality of the TRP components by using them in a fiber optic link designed to replace one of the coaxial cables that perform antenna remoting in a phased array. For this antenna remoting demonstration, we used an existing linear array at the Makaha Ridge, MIT Lincoln Laboratory Facility. Ordinarily, each subarray is connected to the programmable array computers in the control trailer with coaxial cable. The performance of the array with all coaxial cables connected to each subarray was compared to the case with one of the coaxial cables replaced by the fiber optic link. The results showed no degradation in the performance of the linear array with the TRP fiber optic link replacing one of the remoting coaxial cables.

Principles and performance of traveling-wave photodetector arrays

Analog fiber-optic links are used in a variety of microwave applications, including cable-TV and cellular-telephone distribution, as well as antenna remoting. The RF insertion loss and output power obtainable from externally modulated links is primarily limited by photodetector optical-power handling capabilities. Using traveling-wave concepts similar to those in microwave distributed amplifiers, we demonstrate the principle of traveling-wave detector arrays (TWDAs) in which discrete photodiodes are embedded within an artificial transmission line. By feeding these detectors with suitably time-delayed optical signals, this arrangement coherently combines multiple RF photocurrents into a single output. This paper presents the theory, construction details, and results of two- and four-element TWDA's operating up into the Ku-band. We demonstrate a two-element TWDA yielding a 6-dB improvement in insertion loss and RF output power with 12 GHz of operating bandwidth, and a four-element TWDA yielding 12-dB improvement up to 18 GHz.

Transient and optoelectronic feedback-sustained pulsation of laser diodes at 1300 nm

We report the observation of self-sustained pulsation and transient self-pulsation in laser diodes at 1300 nm and the effects of optoelectronic feedback on the pulsations. Transient self-pulsation has a lifetime of a few minutes with frequencies up to 7 GHz. The linewidth of self-pulsation is on the order of 0.5 GHz. With optoelectronic feedback, the transient self-pulsation can be sustained and the linewidth significantly reduced to about 20 kHz. The center frequency of feedback-sustained pulsation is dependent on the passband of the bandpass filter in the feedback loop. The feedback sustained pulsation can be frequency modulated for applications in subcarrier multiplexed optical networks such as cable TV distribution and antenna remoting.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

COMMERCIAL LiNBO_3 INTEGRATED OPTIC DEVICES

The application of LiNbO3 integrated optical devices in the areas of telecommunications, cable television signal distribution, antenna remoting, and fiber optic gyroscopes is reviewed. Emphasis will be placed on significant new devices and device improvements which are presently in commercial and advanced development.

Dynamic range requirements for optical transmitters in fiber-fed microcellular networks

Analog fiber-optic links can be used for antenna remoting in microcellular networks. Using a statistical model of user access in a wireless network, it is shown that by accepting a modest (<0.5%) percentage of blocked calls, a modest optical link dynamic range of 91 dB (1 Hz) is required. By using multiple fiber-fed antennas per cell and proper network protocol, the required dynamic range is dramatically reduced to <80 dB for the same blocking probability.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance prediction and optimization of a coherent phase modulated low noise analog optical link operating at microwave frequencies

Analog optical communication links operating at microwave frequencies are useful for applications like antenna remoting, transceivers, optical signal distribution (CATV), etc. In recent years great progress has been achieved on AM optical links, however, very little has been published on the use of coherent optical links for analog applications. In this paper, we present the analysis, calculated performance, and design guidelines for a coherent phase modulated analog optical link. The performance of this link is compared to that of AM links, and a substantially improved performance is predicted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>