MIT Lincoln Laboratory Journal: fifty years of radar

This review assumes that many non-US readers may not be well-informed about the steps and work in radar development in the US after WW II to the present. Many know MIT by name and recall the famous Radiation Laboratory Series. But the more recent technical history has been less in the "public domain." In an attempt to correct this, one of the key institutions in the field, the MIT Lincoln Laboratory two years ago produced a special issue of their regular publication. Although the document currently at hand is not a book in the strict sense, the size, shape, and editorial comprehensiveness of the MIT Lincoln Laboratory Journal's Fifty-Year Anniversary Issue (12, 2, 2000) justifies calling this article being treated as a book review.     

The Fine Structure of the AKR Electromagnetic Field as Measured by the Interball-2 Satellite

The fine structure of the Auroral Kilometric Radiation (AKR) is studied using multicomponent measurements of the electric component of the electromagnetic field in the frequency band 4 kHz–1 MHz (the POLRAD experiment onboard the INTERBALL-2 satellite). Special attention is paid to the measurements near the source of the AKR: under conditions when the lower boundary of the emission range descended sufficiently low, down to the local gyrofrequency of electrons. From the analysis of the electric field structure the conclusion is drawn that the bulk of the AKR power is carried by the signal component fast variable in time and frequency (flickering component). The power of a constant component (continuum) is lower by at least an order of magnitude. During strong bursts of the AKR, the relative contribution of the flickering component increases. The spatial structure of the zone of generation has at least three characteristic scales along and across the magnetic field.     

碧水青山映古城——雨城雅安

雅安市坐落在四川省中部，位于四川盆地与青藏高原交接带。古为青衣羌国领地，汉代称雅州，名闻遐迩的川藏茶马古道以此为起点翻越莽莽群山逶迤西去，城边的蒙顶山是中国茶化的发祥地，憨态可掬的大熊猫也是从雅安山野里走向世界……此地自古就是多元化的交汇之所，也是地理意义上汉区与藏区和彝区的分水岭，高耸入云的大山将这里切割为迥然而异的化区和自然带，川流不息的青衣江荡涤着这座古风习习的昔日边城。     

Removing autocorrelation sidelobes by overlaying orthogonal coding on any train of identical pulses

A coherent train of identical linear FM (LFM) pulses is used extensively in radar because of its good range and Doppler resolution. Its relatively high autocorrelation function (ACF) sidelobes are sometimes reduced through spectrum shaping (e.g., nonlinear FM, or intrapulse weighting on receive). We show how to completely remove most of the ACF sidelobes about the mainlobe peak, without any increase to the mainlobe width, by diversifying the pulses through overlaying them with orthonormal coding. A helpful byproduct of this design is reduced ACF recurrent lobes. The overlaid signal also results in reduced Doppler tolerance, which can be considered as a drawback for some applications. The method is applied to several trains of identical pulses (LFM and others) using several orthonormal codes. The effect on the three important properties of the radar signal: ACF, ambiguity function (AY), and frequency spectrum is presented. The effect on Doppler tolerance is studied, and implementation issues are discussed. The new design is also compared with complementary and sub-complementary pulse trains and is shown to be superior in many aspects.     

Distance estimation at 60 GHz

An FM-CW radar front-end was fabricated in an integrated manner at 60 GHz by using the NRD guide. Main emphasis was placed on compactness in size and high-precise operation in performance. The fabricated radar consists of an FM Gunn oscillator, a balanced mixer, and a planar antenna fed by leaky NRD guide with a mechanically beam-scanning performance. All circuit components and the antenna were contained in a compact housing of 170 /spl times/ 140 mm in area and 25 mm in thickness, and thus, a thin type of millimeter-wave radar front-end was successfully developed. Moreover, an error of distance estimation was measured to be less than a distance of 0.7 m.     

Superiority of canards in homing missiles

We suggest a first-order model to distinguish between nose control (canards) and tail control. We present optimal guidance strategies and demonstrate the superiority of nose control. This simple model enables us to develop simple and robust guidance strategies based on three approaches: unconstrained optimal control, constrained optimal control, and constrained differential games. It turns out that nose control requires low gain and is capable of forcing small miss distance in the presence of a maneuvering target.     

Power anomaly effects and costs in low-voltage mobile power systems

Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and mitigation methods for power anomalies typical of LV mobile power systems. Electric power anomaly cost data collected from the literature are also presented, from which the costs of anomalies to the national defense are estimated using some simple rationales.     

Road profile recognition for autonomous car navigation and Navstar GPS support

We discuss autonomous car navigation based on updating dead reckoning (DR) by road profile recognition (RPR). The navigation system requires sensors to detect changes in altitude and driving direction which are installed in modern cars for different purposes (e.g. ABS sensors). The layout of the navigation system is discussed and simulations are carried out over driving distances of approximately 150 km on the basis of realistic road data and ordinary sensor accuracies. Positioning errors of lower than 10 m (standard deviation) are observed. To achieve this accuracy the synchronization error between measured and mapped data must be continually estimated. The introduced navigation method is ideal to complete present commercial car navigation systems using Navstar GPS.     

Operational testing of valve regulated lead acid batteries incommercial aircraft

Valve regulated lead acid (VRLA) batteries provide electrical performance that is virtually identical to sintered plate nickel-cadmium battery systems. In addition, the VRLA batteries offer the user a no-maintenance battery and other enhanced features that make this a very desirable battery for aircraft applications. In field trials, where VRLA batteries were substituted for nickel-cadmium batteries, the VRLA provided the user with a high reliability turbine engine starting battery under a wide variety of climatic conditions     

Advanced lithium ion battery charger

A lithium ion battery charger has been developed for four and eight cell batteries or multiples thereof. This charger has the advantage over those using commercial lithium ion charging chips in that the individual cells are allowed to be taper charged at their upper charging voltage rather than be cutoff when all cells of the string have reached the upper charging voltage limit. Since 30-60% of the capacity of lithium ion cells may be restored during the taper charge, this charger has a distinct benefit of fully charging lithium ion batteries by restoring all of the available capacity to all of its cells