Currently a large amount of debris, potentially lethal to resident space assets, is orbiting Earth. While a handful of countries keep track of it, a significant gap is emerging between the debris density, its growth, and the ability to track it and monitor it on a continuous basis. This article takes a close look at the key high-power radars that are entrusted with this difficult task and examines and assesses the high-power transmitter technology and its advancement over the past four decades.

This letter presents a novel and challenging design of a 50-way all-waveguide W-band radial combiner, utilizing WR10 ports for all connections. The novelty lies in its pioneering design and implementation of the radial combiner structure, while the challenges stem from the complexities associated with high-frequency design, manufacturing precision, and the integration of multiple waveguide sections. The design begins with a radial combiner featuring rectangular waveguide peripheral ports and a circular waveguide intermediate port operating in the TE01 mode, which is particularly advantageous due to its low loss, attributed to its field distribution with minimal surface current density. A mode transducer is designed to convert the intermediate circular waveguide TE01 mode to the dominant TE10 mode in the WR10 rectangular waveguide. This transducer is integrated with the radial combiner to produce a standard WR10 waveguide output. The design follows a modular approach, dividing the process into separate optimally designed blocks, which are then integrated to form the final structure. Mechanical considerations are crucial at such high frequencies, and all features, such as matching disks and bifurcations, are designed to require only simple mechanical tooling. The design is thoroughly discussed, and an experimental prototype was fabricated and tested, demonstrating good performance without the need for tuning.

We present a 100W W-band solid-state power amplifier (SSPA) with 9GHz of bandwidth and a gain-bandwidth product improvement of at least 9X over any previously published W-band SSPA.

This paper summarizes over 60 years of radar system development at MIT Lincoln Laboratory, from early research on satellite tracking and planetary radar to the present ability to perform the centimeter-resolution imaging of resident space objects and future plans to extend this capability to geosynchronous range.

An upgrade to the Haystack Ultra-Wideband Satellite Imaging Radar (HUSIR) with a fifty-fold peak power increase is underway utilizing a vacuum power electron device for the W-band transmitter amplifier. This 17-dB sensitivity increase will extend the range of HUSIR capability to geosynchronous orbits (GEO). A single Communications and Power Industries (CPI) Gyrotron Traveling Wave Tube (TWT) design is expected to deliver 50-kilowatt peak power over the 92–100 GHz HUSIR bandwidth. A Raytheon Technologies solid-state amplifier will combine over 100 monolithic microwave integrated circuit (MMIC) devices to provide 100 watt peak power input for the GyroTWT. Modifications for the HUSIR radar transmitter, antenna feed, and transmit path are underway to accommodate the anticipated power increase. This paper highlights the contributions of EM modeling and simulation to this challenging development effort.

The cascaded noise behavior of RF components arranged in series is well known but that of parallel arrangements such as arrays and beamformers has received far less coverage. In such arrangements it is not always the case that signals add coherently while noise adds incoherently. High power solid-state amplifiers require large-scale RF power combining of many identical devices at their output. Wideband output at high efficiency imposes true-time-delay matching on the signal paths being summed and saturation of the final-stage amplifiers. Immunity from radio frequency interference (RFI) and oscillation require significant gain upstream of the parallel output stages which are to be combined. These requirements were observed to act in concert in a 30 kW peak power wideband (410 to 450 MHz) solid-state UHF transmitter to produce coherent addition of RF thermal noise from the various paths in these combiners, even when they were isolated and terminated with absorbing loads. In a monostatic radar, where a high-gain aperture is shared by the transmitter and receiver, inter-pulse noise power spectral density (PSD) must be suppressed to below −100 dBm/MHz through techniques such as bias-switching of the devices and/or RF switching of the common path in order to eliminate desensitization of the receiver via T/R leakage. Implementation of these methods, and their tradeoffs, are discussed in this paper.

The Haystack Ultra-wideband Satellite Imaging Radar (HUSIR) is a dual-frequency ground-based radar operating at X-band and W-band providing high resolution Inverse Synthetic Aperture Radar (ISAR) imagery of Earth orbiting satellites at 3 cm resolution. An upgrade of the radar hardware is being initiated to extend W-band operation from low Earth to geosynchronous orbit. In this paper we report on the development of a new W-band Gyro TWT transmitter increasing peak transmit power from ~1 kW to ~50 kW and upgrades to the receiver and feed subsystems made necessary by the increased W-band power.

For several decades high-power tracking and imaging radars around the world have been reliant on vacuum electron devices (VEDs) to power them. Increased cost, dwindling know-how, long delivery time, and limited commercial providers has led radar engineers to consider solid-state alternatives. This paper reports on several efforts to develop alternative solid-state RF high power amplifiers that span a broad RF spectrum (VHF to W-band) and could potentially serve as an alternative to aging VED technology.

This tutorial provides an overview of RF-transparent protective enclosures or “radomes” for ground-based antennas. In addition to electromagnetic behavior, structural and environmental considerations are highlighted which are important in large antenna installations such as those for satellite communication and deep space radar applications. Different radome types such as metal space frame, inflatable, and sandwich are contrasted with emphasis on the tradeoffs they entail for the antenna system.

In 2010 the Haystack 37 meter reflector was replaced with a new antenna. This work presents measurements of the spatial and temporal thermal behavior of the antenna and its radome under diurnal and seasonal forcing. Values for thermal capacity and resistance of the antenna structure and radome are derived. The convective heat transfer coefficient acting on the aluminum antenna backstructure is found to be 2 to 5 W/m$^{2}$ -K for all instrumented member geometries. Modeling with a simple lumped-thermal-element representation is presented, which accurately matches observed temperatures. The heat and ventilation equipment and controls are demonstrated to be sufficient to keep modeled antenna gain reductions due to thermally-induced distortions ${<}0.4$ dB more than 90% of the time during heating season. Gain reductions during summer will be dominated by vertical stratification of air in the radome, which is shown to be associated with daylight hours and outside temperature ${>}15^{\circ}$C.