a-temp-009 -1 issue 002 understanding new naval radars

A DIVISION OF ARMSCOR SOC LTD

Understanding New Naval Radars From An

Electronic Support (ES) Perspective

Presented By : Lance Clayton (IMT)

31 May 2018

A-TEMP-009 -1 ISSUE 002


About the Presenter : Lance Clayton

• ABSTRACT : This talk addresses the evolution of Electronic Support (ES) technologies as required by future Naval Vessels to address the changing trends in Naval Radars.

• BIO : I started my career in the Defence Electronics Industry in 1986 and completed an Apprenticeship and Technical College Diploma in Radio/Radar in 1990 while working at the SA Naval Dockyard in Simon’s Town and I was involved with Radar, ESM and certain Combat Management Sub-system refits on SAN Strike Craft and Daphne Submarines. I completed a further Diploma in Electronic Engineering at the Cape Peninsula University of Technology and then worked in Design and Development at African Defence Systems from 1995 where I was involved with development of combat suite and radar system upgrades for the SAN. I have been at the Institute for Maritime Technology (IMT) since 1999 and I am the Domain Leader Maritime RF Electromagnetics that includes projects relating to Radar, Radio Communications and EW.


Classical ES Requirements

Electronic Support (Electromagnetic

Support )

Radar-ESM Electronic

Intelligence(ELINT)

To provide tactical warning and situation awareness in order to take required action

To gather detailed signal information for analysis to populate ESM threat libraries or make strategic decisions

Tactical Combination


Classical Naval Radar-ESM

• Radar-ESM on warships provide instant warning of emissions over a wide frequency band usually from 1-18 GHz but there are now even missile seeker threats up to 40 GHz

Radar-ESM System on Royal Navy Type-23 Frigate

Wideband Directional Antenna Array

The Radar-ESM Receiver’s Advantage over the Radar


Today’s Naval ES Environment

• The emergence of Commercial and Military Solid State Low Power Coherent Pulsed Radars with Pulse Compression.

• The emergence of Commercial and Military Frequency Modulated Continuous Wave (FMCW) Radars.

• Increasing Electromagnetic Density (Numbers of radar signals closely spaced in Time and Space).

• Complex Waveforms with varied Pulse Widths (PW), Intra-Pulse characteristics, Pulse Repetition Frequency (PRF) and Antenna Rotational Characteristics.

• Radars with Electronically Steered Antenna Arrays.

• Radars with Varied Modes to fulfill Varied Operational Requirements.


Low Power Pulse Compression Radars

• Short Pulsed Non-Coherent radars with peak powers of 20-25KW are being replaced with radars transmitting peak powers of around 200W

• Pulse Compression Technology is common place in in newer radars, the low power pulses with pulse widths of up to 100 uS which would equate to a range resolution of around 15Km are compressed using chirp or other coding technology to equivalent narrow band pulses with range resolutions down a few meteres.

• This presents a challenge to the ES receiver system where sensitivities need to increase by around 20dB and the receivers need to be more capable of handling CW signals.


Frequency Modulated CW Radars

RRS RSR940/906 FMCW Surveillance Radar RRS RTS3200 FMCW Tracking Radar


Frequency Modulated CW Radars

• FMCW radars repetitively sweep across a frequency band and if a target return is detected the time alignment of the returned and transmitted sweep would differ thus producing a frequency difference. This frequency difference determines range.

FFT Range Bins


Radars With Electronically Steered Arrays

• Naval Radars have evolved from 2D -> 3D to provide not only the Range, Bearing and Speed but also the Altitude of detected targets.

• Naval Radars now steer the transmitted and received beam mechanically, electronically and both mechanically and electronically.

• Earlier generation 3D radars used a single transmitter and receiver and shifted the beam by changing the phase of the signals passively using phase shifters only as they entered and left the antenna. These radars are Passively Electronically Steered Array (PESA). There is no amplification on individual elements in the array. When varied phase shifts are provided by these phase shifters then the power and receive sensitivity at specific angles to the array where the signals add coherently is increased to form beams.

• Later generation 3D radars use many low power transmit and receive sections in the antennas. These radars are called Active Electronically Steered Array (AESA). When varied phase shifts are provided by these sections then the power and receive sensitivity at specific angles to the array where the signals add coherently is increased to form beams.


Passive Electronically Steered Array Radars

Passive Electronically Steered Array (PESA) Naval Radars

Phase Shifting for Beam Steering Applied by Phase Shifters

High Power Ferrite Phase Shifter

High Peak Power Travelling Wave Tube (TWT) Transmitter Slotted Waveguide Array (Newer Radars use Microstrip Techniques)


Passive Electronically Steered Array Radars

Passive Electronically Steered Array (PESA) Naval Radars

This Multi-Mode Radar provides Surface search and 12 simultaneous beams in elevation up to 90 Degrees for Air Search.

Thales MRR-3D NG

This Multi-Mode Radar provides Surface search and can scan 5 beams in elevation up to 70 Degrees for Air Search in every rotation.

Thales Nederland Smart-S SAAB Sea Giraffe AMB

This Multi-Mode Radar is called AMB (Agile Multi-Beam), and incorporates a stacked beam solution. The Sea Giraffe AMB has 12 simultaneous receiver beams in elevation and uses A Mono-pulse technique to calculate the Elevation.


Multi-Mode Naval Radars

Typical Modes of Naval Multi-Mode Radars : • Self Defence/Protection - The radar scans the surface and provides air

coverage up to high elevation angles. The radar may alternate between air and surface search on alternative scans with short PRI and short ARP.

• Medium Range Surveillance – The Radar scans the surface and the lower elevation angles with a possibly longer PRI and longer ARP.

• Long Range Surveillance - The Radar scans the surface and the medium elevation angles with a long PRI, long pulse and possibly changed intra-pulse characteristic for pulse compression and longer ARP.


Active Electronically Steered Array Radars

Active Electronically Steered Array (AESA) Naval Radars

Phase Shifting for Beam Steering Applied in Digital Processing

Multiple Tx/RX Modules Stacked in Array




AN/SPY-1D

Air & Missile Defence Radar (AMDR)

Volume Search & Air Control

Track

Raster Scan

Surface Search




IAI Elta EL/M-2248 MF-STAR Hensoldt TRS-4D A rotating version of the Active Electronically Scanned Array (AESA)




BAE Samson Radar Dual Face Rotating Planar Phased Array for Air & Missile Defence




Where did the tracking radar go !!


Electronically Steered Array Radar Signals


Digitally Modulated Radar

Classical Radar Signal parameters



Both Active and Passive Electronically Steered Array Naval Radars Generally Transmit Pulse Groups

Mode 1

Mode 2



If a Passively Electronically Steered Array (PESA) applied beam steering on transmit or it is a Active Electronically Steered Array (AESA) Naval Radar there may be amplitude variations between pulse groups.

Software Defined Radar

Could also be tracking !




Modern AESA radars are able to essentially use a random number generator to come up with a random, sequence of frequencies, and then not only transmit, but also memorise them. This randomness is not just constrained to frequency however, it can also be random in the following: Pulse repetition frequency: For example, does it pulse exactly 500 times a second, every 2 milliseconds, or does it pulse 523 times one second and 347 times the next, with pulses varying being between 4 and 1 millisecond apart? Duty cycle: How long a pulse lasts; AESA radars generally want this to be low to minimise the total amount of energy transmitted at the enemy, but it can also vary this to make the signal less uniform.




Using intra-pulse modulation : Not only can the AESA change the frequency of each pulse, but it can also change the frequency continuously during a pulse to achieve pulse compression where an increase or decrease in frequency during a pulse can identify that there are multiple targets when they have little difference in range from the radar even when longer pulse widths are used thus allowing a radar with a long pulse to gain range to have the range resolution of a radar with a short pulse. AESA radars do this using technology called Direct Digital Synthesis (DDS)




This is the screen of a high performance Rohde & Schwarz Signal Analyser looking at the Emission from a AESA Radar. It can Classify Power and Frequency Trends In pulse groups to attempt to identify radar operating mode




The same Signal Analyser to Classify Pulse Width and Intra-Pulse Characteristics (FMOP/PMOP) in pulse groups.


ES Receiver Architectures

• Wide-Band Log Video Detection – DLVA/SDLVA

• Wide Band Superhet

• Narrow Band Superhet

• Channelised Receiver Architecture

• Digital Receiver Architecture

• Combined Wide/Narrow Band Superhet with IF sampling Digital Receiver


Increased Sensitivity Radar ES Receiver

Technology

Experimental IMT Wide Band Receiver and X-Band Narrow Band Dual Conversion Superhet with -80dBm Sensitivity. Actual Tests with this receiver against SharpEye Low Power Commercial Pulse Compression Radar have also shown good results.

Actual Tests with this receiver against SharpEye Low Power Pulse Compression Radar have shown good results.


Increased Sensitivity Radar ES Receiver

Technology

In order to deal with the frequency agility of Naval Multi-Mode Radars, a Wide-Band Superhet is required. In order to get the higher sensitivity over a wideer band, more antenna gain is required like that provided by a Spin DF Antenna.

In this receiver the WB IF output needs to feed a digital receiver sampling at around 1Gigasamples or more.

The increased antenna gain of A Spin DF would be an advantage


Radar ES Digital Receiver IF Processing

De-Interleave by Frequency when Emitters are Fixed Frequency (Using Superhet Techniques)

De-Interleave by Amplitude when Emitters are Frequency Agile or Close in Frequency Separation

High Speed FFT Processing

FFT Analysis of De-Interleaved Radar Signal Reveals Pulse Parameters


ES Receiver for FMCW Radar Signal

Parameter Measurement

• Analysis of FMCW parameters would require high speed FFT analysis at rates much higher than the radar’s range FFT

• The identifying parameters for FMCW radars would be as follows : • Antenna Rotational Period (ARP)

• Sweep Repetition Frequency (Hz)

• Sweep Time (ms)

• Sweep Bandwidth (MHz)

High Speed FFT F (t)


New Generation ES Receiver Design for

Naval Applications

• New Generation Modular Naval ES Receiver System Design


To Conclude

• The receiver technologies required for Radar ES need to be of increased sensitivity to deal with low power radar technology.

• FMCW radars used for surveillance are growing in number and need to be addressed in new generation ES receiver design.

• ES Receiver technologies for new lower power pulsed radars are quite complex and need to determine group parameters to identify waveforms and modes especially when dealing with PESA and AESA radars.

Questions?

a-temp-009 -1 issue 002 understanding new naval radars

Documents