New Radar Technology 8 500 10 500 MHz

New Radar Technology 8 500 -10 500 MHz Band Presented by Mr. Frank Sanders National Telecommunications & Information Administration Mr. Thomas Fagan Raytheon

Technical Characteristics • 8 500 -10 500 MHz radars exist on land-based, transportable, shipboard, and airborne platforms. • Radiodetermination functions include airborne, space & surface search, ground-mapping, terrain-following, navigation (both aeronautical and maritime), and target-identification. • Major differences among radar designs include: transmitter output devices, transmit duty cycles, emission bandwidths, presence and types of intra-pulse modulation, frequency-agile capabilities of some, transmitter peak and average powers, and types of transmitter RF power devices. • These characteristics, individually and in combination, all have major bearing on the compatibility of the radars with other radio systems in their environment.

More Technical Characteristics • Many radiolocation radars in this band are primarily used for detection of airborne objects. • The purpose is to measure target altitude as well as range and bearing. – Some of the airborne targets are small and at long ranges as great as 555 km (300 nautical miles). – These radiolocation radars must have high sensitivity and must provide a high degree of suppression to all forms of clutter return, including that from sea, land, and precipitation. • In some cases, the radar emissions in this band are required to trigger radar beacons.

Mission Requirements Dictate General Design Characteristics Basic radar design parameters are as follows: – Minimum target size (cross section) and maximum range requirements – Maximum available space for antenna (constrained, for ex. , by platform size) – Spectrum band (driven by propagation needs & maximum possible antenna size) – Required (minimum acceptable) signal-to-noise ratio (SNR) for target echoes – Minimum number of pulses (N), echoed from each target to achieve minimum SNR – Antenna scan rate and beam scanning pattern, determined by the values of N and PRI – Pulse repetition interval (PRI), determined by maximum radar range – Pulse width and shape, determined by need for best possible location resolution

Mission Requirements Dictate General Design Characteristics (cont. ) • Basic radar design parameters continued: – Pulse peak power, determined by target size (cross section) and maximum range – Pulse modulation (coding), which can allow pulses to be transmitted at lower peak power, but with proportionately longer length. (i. e. , average power tends to stay constant). – Selection of radar transmitter output device is determined by needs for peak power, pulse modulation (if any), size, weight, cost, reliability, and spectrum characteristics. • 8 500 -10 500 MHz radars often have small platform-size (and thus small antenna) constraints. • 8 500 -10 500 MHz radars often need to observe small targets at relatively long ranges using designs that have reasonable cost, reliability, and maintainability. • These constraints feed back into all of the design parameters listed on the previous slide.

Mission Requirements Dictate General Design Characteristics (cont. ) • 8 500 10 500 MHz radars often need high transmitter peak and average power • Master-oscillator-power-amplifier transmitters may be preferred over power oscillators. • Tunability and frequency-agility are sometimes required • Some require pulse modulation such as a linear (or non-linear) FM chirp or phase codes. • Antenna mainbeams often need to be steerable in one or both angular dimensions, sometimes using electronic beam steering.

Mission Requirements Dictate General Design Characteristics (cont. ) • Driven by mission requirements, individual 8 500 -10 500 MHz radars need a wide variety of pulse widths & pulse repetition frequencies. Chirp radars need a variety of chirp bandwidths. Some frequency-agile radars need a variety of agile-frequency modes. Such design flexibilities can provide useful tools for performing missions while maintaining compatibility with other radars in the environment. • Versatile receiving and processing capabilities are also often needed for 8 500 -10 500 MHz radars to include: – Auxiliary sidelobe‑blanking receive antennas; – Processing of coherent-carrier pulse trains to suppress clutter return by means of moving-target-indication (MTI): – Constant-false-alarm-rate (CFAR) techniques: – Adaptive selection of operating frequencies based on sensing of interference on various frequencies (some cases).

Marine Radar U. S. Department of Commerce • Typical X-Band maritime radionavigation radar • Magnetron Output • Integrated Platform (receiver & transmitter contained in small mastmounted package) • Typically found onboard pleasure craft and commercial ships

8 500 -10 500 MHz Marine Radar Mk-2 Pathfinder (marine) Raytheon

Mission Requirements Dictate Frequency Range • Atmospheric attenuation and water vapor absorption help determine radar operational frequencies. • Weather radars use frequencies where water vapor absorption is high. • Radiolocation radars use frequencies where water vapor absorption is low. – Only certain frequency bands have low water vapor absorption.

8 500 -10 500 MHz Radar Design Tradeoffs • Except for some ground-based systems, 8 500 -10 500 MHz platform dimensions typically restrict the maximum possible size of transmitter antennae, both for present and future systems. • Small antenna sizes tend to force high pulse peak power levels for adequate target detection. Alternatively, if lower peak power levels are used then longer pulse widths are required to expose targets to enough total energy to detect them. • But, if longer pulses are used, then additional pulse modulation (coding) is required to achieve adequate range resolution.

8 500 -10 500 MHz Radar Design Tradeoffs (cont. ) • The choice of 8 500 -10 500 MHz transmitter output device technology is a major design decision. It significantly affects radar performance, cost, and spectrum out-of-band spurious emission levels. Tradeoffs between all these parameters must be carefully balanced by designers of X-band radars. • Some 8 500 -10 500 MHz radar designs may be driven primarily by cost and size factors, and may therefore need to use cheaper and lighter tubes, such as magnetrons. Conversely, more advanced transmitter output devices (eg; solid state), may be more costly, heavier, and more complex. But they may offer better-controlled pulse shaping and thus possibly improved spectrum out-of-band spurious emission characteristics.

8 500 -10 500 MHz Airborne Radar • Typical example of an Airborne Radar where it must fit into the nosecone of an aircraft • Note that the antenna is small to fit into the limited amount of space available AN/APG-73 radar Raytheon

8 500 -10 500 MHz Airborne Radar AN/APG-70 radar Raytheon

8 500 -10 500 MHz Surface Surveillance Radar Used for monitoring ground traffic (airplanes, service vehicles, baggage vehicles, security vehicles) at airports Advanced Surface Movement Radar (ASMR) Raytheon

Future 8 500 -10 500 MHz Radar Design Trends (cont. ) • More flexibility will be needed, including the capacity to operate different modes in different azimuth and elevation sectors. • Capability to operate in a wide bandwidth will be needed. • Electronically-steerable antennae will become more common. • Current technology makes phase steering a practical and attractive alternative to frequency steering. – Radars in other bands have employed phase steering in both azimuth and elevation, and can steer any fundamental frequency in the radar’s operating band to any arbitrary azimuth and elevation within its angular coverage area. – Phase steering may enhance electromagnetic compatibility in many circumstances. • Reduction of unwanted emissions below those of the existing radars that employ magnetrons or crossed-field amplifiers may occur through the use of linear beam and solid-state output devices.

Future 8 500 -10 500 MHz Radar Design Trends (cont. ) • Radar designs will continue to evolve – Towards solid-state output devices; – Radar bandwidth will increase (instantaneous and operational); – Peak power will increase on some radars; – Average power will increase on some radars; – Pulse Repetition Frequency (PRF) and pulse width will increase; – Amount of coding modulation (phase and chirp) will increase due to the trend towards solid-state output devices; – Use of this radar frequency band will increase.

Summary • Development of radars in this band is an ongoing process that continue to evolve as technology advances. • Working Party 8 B will continue to follow these technology trends and their consequences and impact on the use of the radio spectrum. • Thank You for your attention!