by Professor W J Mullarkey (db Research Ltd) at the BMEA Conference 2010

4. Common signal processing chain for all radars. The first task is to illuminate the target scene with energy and store the resulting echo returns on a B Plane Antenna Signal processing Radio Tx and Rx Scan Converter r B Plane Display

5. B Plane Bearing Range

6. Pulse Radar amplitude t return Pulse Repetition Period Tx Rx (not to scale) time Pulse Radar t return

7. FMCW Radar Rx The Rx frequency is different to the current Tx one t return Sweep Repetition Period (SRP) time FMCW (Broadband) Radar t return frequency

8. Publicity image from the Navico FMCW radar on a 1/16 mile range

11. The first is determined by receiver bandwidth and pulse length for range; and the antenna characteristics for bearing The second is by the ratio of the echo’s energy to the receiver’s inherent noise.

12. It is expensive to reduce receiver noise so the only practical way to improve target detection is to illuminate the target scene with as much energy as possible. Energy Not Peak Power Think in terms of Joules not Watts

13. Some Numbers A 2Watt FMCW radar will typically sweep the frequency over a period of about 1ms and have a PRF of 1kHz. It transmits all the time and radiates 2J of energy every second. A conventional 4kW pulse radar will typically use a 100nS pulse on the short ranges with a PRF of about 3kHz, which illuminates the scene with 1.2J per second. On a longer range it might use a 1us pulse that provides 4J per second

16. In summary Inherent differences between the technologies Characteristic Broadband (FMCW) Pulse Short range target detection Better Worse Long range target detection Worse Better Visibility of close in targets Better Worse Target resolution in azimuth Same Same Target resolution in range Better Worse Sea clutter suppression Better Worse

17. Inherent differences between the technologies Characteristic Broadband (FMCW) Pulse Power requirements Similar Similar Power cabling Thinner Thicker Requires standby period No No, once switched on Triggers Racon Beacons No Yes Vulnerability to interference from other radars Difficult to solve Easy to solve Vulnerability to onboard reflectors Potentially a problem Not a problem Potential for future development Only just begun Mature technology

32. Notice how the SeaHawk enhanced bandwidth matches that of the 12 ft antenna, with a little gain.

33. Target resolution of an antenna that is twice the size

37. The original presentation included two images taken from the Second Generation SeaHawk. For now they are company confidential. If you want to view them AND are either and existing Collaborator of dB Research OR Denbridge Marine OR have a Confidentiality Agreement with one of them, email [email_address] with a request for a password to access it and others.