Neil Chamberlain

A Self-Adapting Flexible (SELFLEX) Antenna Array for Changing Conformal Surface Applications

A phased-array test platform for studying the self-adapting capabilities of conformal antennas is developed and presented. Specifically, a four-port 2.45-GHz receiver with voltage controlled phase shifters and attenuators is designed along with four individual printed microstrip patch antennas attached to a conformal surface. Each antenna is connected to the corresponding receiver port with a flexible SMA cable. It is shown that with appropriate phase compensation, the distorted radiation pattern of the array can be recovered as the surface of the conformal array changes shape. This pattern recovery information is then used to develop a new self-adapting flexible 1 × 4 microstrip antenna array with an embedded flexible sensor system. In particular, a flexible resistive sensor is used to measure the deformation of the substrate of a conformal antenna array, while a sensor circuit is used to measure the changing resistance. The circuit then uses this information to control the individual voltage of the phase shifters of each radiating element in the array. It is shown that with appropriate phase compensation, the radiation properties of the array can be autonomously recovered as the surface of the flexible array changes shape during normal operation. Throughout this work, measurements are shown to agree with analytical solutions and simulations.

The UAVSAR phased array aperture

The development of a microstrip patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) is discussed in this paper. The instrument will be flown on an unmanned aerial vehicle (UAV) and will provide accurate topographic maps for Earth science by 2007. The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations for fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of plusmn20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. The amplitude taper is provided by coupling networks in the interconnect circuits as opposed to using attenuators in the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and cross-polarized far-field antenna patterns, and also in terms of active reflection coefficient. Measured performance of a 4-element by 2-element antenna tile is presented

Microstrip patch antenna panel for large aperture L-band phased array

This paper describes the design and development of a large, lightweight antenna panel for an active phased array operating at L-band. The panel was developed under a JPL program of technology development for space based radar. It utilizes dual-stacked patch elements that are interconnected with a corporate feed manifold of striplines. This paper focuses on the electromagnetic design and performance of the radiating elements, with emphasis on scan performance, and also addresses mechanical and thermal aspects of the panel. The element in the array environment has a bandwidth of more than 80MHz centered at 1260MHz and is fed so that it can radiate orthogonal linear polarizations. The envisioned phased array, with a nominal aperture of 50m times 2m, is designed to scan plusmn45 degrees in azimuth and plusmn20 degrees in elevation. The panel of radiating elements has a mass density of 3.9 kg/m2, which represents approximately 50% of the target 8kg/m2 total panel mass density that includes T/R modules and feed manifolds

MRO relay telecom support of Mars Science Laboratory surface operations

The Mars Science Laboratory (MSL) mission landed the Curiosity Rover on the surface of Mars on August 6, 2012, beginning a one Martian year primary science mission. The UHF relay link from Curiosity to the Mars Reconnaissance Orbiter (MRO) incorporates new features enabled by the Electra and Electra-Lite software-defined radios on MRO and Curiosity, respectively. Specifically, the Curiosity-MRO link has for the first time utilized frequency-agile operations, increased data rates from 256 kbps up to 2048 kbps, employed suppressed carrier modulation and a new Adaptive Data Rate algorithm in which the return-link data rate is varied to match the observed channel condition. During the first 200 sols, the telecom operations team has been able to tune the radio and protocol parameters to maximize return-link data volume, which is now averaging roughly 500 Mbits per sol or twice the design requirement of 250 Mbits per sol. The telecom team has also derived new predict models that reduce data volume prediction errors and that quantify the impact of operational modes and link parameters, providing further planning insight for MSL mission operations team.

MAVEN relay operations concept

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission will launch in late 2013 and, following a 10 month cruise to Mars, will study the upper atmosphere of the planet. In addition to the science instruments, the MAVEN spacecraft is equipped with an Electra UHF transceiver to support relay communication with landed assets. This paper describes how UHF relay service is provisioned by MAVEN. The discussion includes a description of the Electra payload, the process by which relay activities are coordinated and accounted for, the process of a typical relay session, including uplink and downlink, as well as special commands to calibrate and verify relay performance. The operational processes for providing these services are inherited largely from prior Mars missions and take advantage of existing infrastructure and lessons learned from those missions. Preliminary data volume return capabilities using adaptive data rates and low-density parity check channel coding are presented.

The DESDynI synthetic aperture radar array-fed reflector antenna

DESDynI is a mission being developed by NASA with radar and lidar instruments for Earth-orbit remote sensing. This paper focuses on the design of a large-aperture antenna for the radar instrument. The antenna comprises a deployable reflector antenna and an active switched array of patch elements fed by transmit / receive modules. The antenna and radar architecture facilitates a new mode of synthetic aperture radar imaging called ‘SweepSAR’. A system-level description of the antenna is provided, along with predictions of antenna performance.

Juno Microwave Radiometer patch array antennas

The requirements, design, and performance of the Juno Microwave Radiometer patch array antennas were discussed. The antennas meet both the electrical performance and environmental requirements. There is generally good agreement between measurements and calculations.

The UAVSAR Transmit / Receive Module

This paper describes the L-band transmit/receive (T/R) modules of the UAVSAR phased array antenna. UAVSAR (uninhabited aerial vehicle synthetic aperture radar) is an airborne, repeat-pass, polarimetric radar interferometer instrument that is being developed at JPL and NASA Dryden. The instrument has demanding requirements for phase stability over temperature and the antenna components, particularly the T/R modules, are key to meeting these requirements. The UAVSAR T/R modules have a bandwidth of more than 80 MHz centered at 1257.5 MHz and support dual receivers for full quad polarization measurements. Phase and amplitude are controlled by a 7- bit phase shifter and a 5-bit attenuator, respectively. Custom microwave integrated circuits were developed and fabricated for the low noise amplifier (LNA) and phase shifter circuits. The receiver noise figure is 2.25 dB at OC including all front-end losses. The transmitter power amplifiers use silicon bipolar junction transistors that typically generate 162 W peak into a nominal 50 ohm load. The modules have an overall efficiency of 32% at the peak operating duty cycle of 5%. Module mass and dimensions are 567 g and 16 cm times 12 cm times 3 cm, respectively. Fifty four of these T/R modules were fabricated for integration into two antennas. System architecture and performance data for this ensemble of modules are discussed.

T/R module development for large aperture L-band phased array

This paper describes a transmit/receive (T/R) module for a large L-band space based radar active phased array being developed at JPL. Electrical performance and construction techniques are described, with emphasis on the former. The T/R modules have a bandwidth of more than 80 MHz centered at 1260 MHz and support dual, switched polarizations. Phase and amplitude are controlled by a 6-bit phase shifter and a 6-bit attenuator, respectively. The transmitter power amplifier generates 2.4 W into a nominal 50 ohm load with 36% overall efficiency. The receiver noise figure is 4.4 dB including all front-end losses. The module weighs 32 g and has a footprint of 10.6 cm /spl times/ 4.8 cm. Fourteen of these T/R modules were fabricated at the JPL pick-and-place facility and were tested using a computer-controlled measurement facility developed at JPL. Calibrated performance of this set of T/R modules is presented and shows good agreement with design predictions.

Juno microwave radiometer all-metal patch array antennas

This paper focuses on the design and RF performance of metal patch antenna arrays for the Juno microwave radiometer (MWR) instrument [1]. Juno is a NASA New Frontiers mission to Jupiter scheduled to launch in 2011. Metal patch antenna elements contain no dielectric. This is attractive for the Juno application because the elimination of dielectric prevents electrostatic discharge due to high-energy electrons in the Jovian orbital environment. Dielectric materials can be engineered to bleed static charge by doping them with carbon powder, but it can be difficult to obtain the desired balance of DC, RF, structural, and thermal performance. All-metal patches side-step these materials issues and provide a design that is amenable to predictable performance, both from an electrical and mechanical point of view. The metal patch design has good pattern performance and other advantages, including wide bandwidth, precise tuning, low mass, and good thermal and emissivity properties.