horas, 50mg tableta de liberación horas) (Pristiq

The several key requirements that have been identified along the major waterway of the Malacca Strait are often categorized from the security and weather perspective. As mentioned above, the main requirements prioritize on monitoring the movement and behavior of medium to larger sized vessels passing through the strait and to provide authorities with sufficient awareness towards harsh propagation conditions in the event of bad visibility and high sea states. In many coastal waters around the world, the implementation of electronically scanning phased array radar systems has proven to deliver high-end performance that fulfils the surveillance and monitoring requirements for the detection and tracking of targets that passes through the monitored sector of the strait. Hence, these radar systems were initially chosen to create a network of multistatic radars along the coasts surrounding the strait due to its capability in delivering the highest detection performance that can be expected from any surveillance radar systems available, and therefore they are preferred especially for applications that requires very high requirements. The advantages of phased array radars as compared to other mechanical scanning surveillance radar systems are discussed in Section 2.1.

However, despite the excellent performance of electronic scanning radars in fulfilling the surveillance requirements of the strait, during the several years of operation the phased array antennas deployed had required regular maintenance to be performed as a portion of the radiating elements within the array may have stopped functioning. When this happens, it prevents the radar from operating at its maximum capability, while going unnoticed, and therefore it was difficult to identify whether the radars were functioning optimally unless there

8

was a significant deterioration in radar performance. Moreover, in addition to the maintenance issues, the authorities have found it challenging and costly to provide regular maintenance of the radars due to the limited infrastructure and poor accessibility to most of the allocated radar sites along the coast. The lack of logistics and difficulty in transporting people in and out of the radar sites within a short period of time have been an inconvenience over the past decade. Hence, as a result the government had evaluated the conditions to be unsuitable for the continuous operation of the existing electronic scanning radar systems, especially for large antennas that requires large fixed radar sites and a continuous large supply of power. The excessive overhead costs and maintenance issues encountered with the existing network of radars was a big driver to go with a simpler antenna solution or method of fulfilling the surveillance requirements. Meanwhile, instead of resolving the issues encountered with the existing radar systems, the government had opted for conventional patrolling methods to provide for the surveillance and monitoring of the Indonesian territorial waters. This decision has led to the purchase of approximately 200 locally produced patrol boats a year across the governing maritime organizations, which have undoubtedly contributed to the steep growth within the shipbuilding industry in recent years.

From a technological standpoint, the implementation of mechanically scanning radar systems at the numerous pre-determined radar sites along the coastline surrounding the strait can be proposed to replace the existing electronic scanning radar systems since most of the targets of interest are primarily large ships that are either stationary or propagating at relatively low speed (<20 knots). Hence, the use of sophisticated phased array antennas may prove to be over performing and unnecessary, especially where cost is of a significant factor. The two most common types of mechanical scanning radar for coastal surveillance are magnetron-slotted waveguide antenna radars and solid state-reflector antenna radars of FMCW type. The latter has become the preferred choice since its introduction within coastal surveillance radars due to its anti-intrusion function with a couple of watts, higher instantaneous bandwidth and frequency agility. Well-designed reflector antennas are also capable of producing beams of significantly higher gain and narrower principal plane beamwidths, where required, that translates to a further maximum detectable range and a higher angular resolution which benefits through better discrimination of smaller targets from the background and an improved detection accuracy. These properties are critically important towards the requirements of a coastal surveillance application, especially when dealing with the detection of ground and flying objects over considerably long operating ranges, and, thus, it generally offers a higher level of performance. Moreover, the suitable radar parameters, which are determined according to the surveillance requirements of the strait, can be fulfilled more flexibly with space fed antennas. Hence, the use of reflector antennas in mechanical scanning coastal surveillance radars has become the

9

most popular choice over the last few decades for applications requiring lower performance capability than electronically scanned radar systems. Such radar systems have been implemented along many major coastlines around the world to create a network of bistatic, or more frequently, multistatic radars.

Although conventional reflector antenna systems are a popular choice for providing effective coastal surveillance and monitoring of common types of target observed along the coastal waters, many existing reflector antenna systems in operation also have limitations from the design, cost and weight perspective, especially those systems that exhibits very high- performance capabilities, from which there are room for possible improvements through new ideas. The project aims to exploit this, thereby placing the focus on addressing the limitations of existing conventional reflector antenna systems by proposing a new reflector antenna design, or particularly feed system, that is novel and unique to current mechanical radar systems employing reflector antennas used for similar applications, and an alternative method of manufacturing medium sized reflector.