Corner reflector

Most readers will say no. They typically base their answer on well-documented facts about the most commonly used antennas such as a single dipole or monopole, the horn, the flat spiral, the corner reflector, the polyrod, the patch, the log periodic, the helical with a groundplane, and many more. These are all lacking in their ability to produce a low RCS over a broad frequency range when properly matched. Thus, we shall in this chapter instead concentrate on one of the few concepts that can truly produce invisibility in the backward sector, namely the large flat aperture in the form of an array backed by a groundplane and with uniform aperture illumination. The tapered case will also be discussed and it will be shown that also in that case, invisibility is conceptually compatible with 100% efficiency. 

Xia, Y. et al. 2004. Landslide Monitoring in the Three Gorges Area Using D-InSAR and Corner Reflectors. Photogram metric Engineering Remote Sensing. October 2004 1167-1172. 

A corner-reflector antenna maybe formed as shown in Fig. 13.45. A ground plane or flat reflecting sheet is placed at a distance of 1/16- to 1/4-wavelengths behind the dipole. Gain in the forward direction can be increased by a factor of 2 with this type of design. 

Fig. 2 Schemes of the optical part in the LICRM system. 1, Laser light source 2, movable plane mirror or corner reflector 3, polarizer 4 and 5, photocells 6 and 7, semi-transparent (half-sUvered) mirrors 8 and 9, stationary mirrors 10, the directions for the reflector 2 displacement...

Fig. 3 A scheme of the LICRM setup operating under compressive stress, 1, Laser light source 2, movable corner reflector 3, polarizer 4 and 5, photocells 6 and 7, semi-transparent mirrors 8, stationary corner reflector 9, specimen 10, support 11, puncheon 12, clock-like scale micrometer for rough controlling deformation 13, dampers 14, figured lever providing a stress constancy 15, load 16, oil damper 17, cooling unit 18, heater 19 and 20, programmable temperature regulator 21, amplifier 22, tape recorder 23, oscillograph 24, shaper of a meander (Schmitt trigger) 25, computer with the interface board imbedded...

The PFS instrument consists of two double-pendulum interferometers with corner reflectors. The near infrared interferometer operates from 2000 to 8000 cm with a calcium fluoride (CaF2) beamsplitter and a 2° field of view. The short-wave detector, a lead selenide photoconductor, has a NEP of 1 x 10 2 wHz-2 and... 

In a transmission insertion probe (see Figure 6.1) light makes only a single pass through the sample gap. In these probes either the fiber is forced into a U bend at the end of the probe, or corner-cube reflectors must be used to turn the light path 180°. Again, the smallest practical gap is 0.5 mm (0.5-mm optical path). 

The beam enters the 1.75 m Teflon-lined White cell containing a corner cube reflector (3) and undergoes 102 passes before exiting to the detector. Absorptions at least as low as 10 s can be measured which, for a total path length of 150 m corresponds to detection limits in the range 25 to 100 parts per trillion by volume for most atmospheric gases. 

The seismic analysis of the core is performed with the two-dimensional special purpose computer codes CRUNCH-2D and MCOCO, which account for the non-linearities in the structural design. Both CRUNCH-2D and MCOCO are based on the use of lumped masses and inertia concepts. A core element, therefore, is created as a rigid body while the element flexibilities are input as discrete springs and dampers at the corners of the element. CRUNCH-2D models a horizontal layer of the core and the core barrel structures (Figure 3.7-7). The model is one element deep and can represent a section of the core at any elevation, MCOCO models a strip of columns in a vertical plane along a core diameter and includes column support posts and core barrel structures (Figure 3.7-8). The strip has a width equal to the width of a permanent reflector block. Both models extend out to the reactor vessel,... 

The side reflector consists of two rows of hexagonal reflector columns, as shown in Figure 4.1-2. The side reflector hexagonal elements are solid elements, with the exception of the fuel handling hole, and the control rod channel in 24 of the reflector columns adjacent to the active core as shown in Figure 4.2-4. The control rod channel diameter is 102 mm (4 in.) and stops at an elevation just below the active core. The control rod channel is centered 119.4 mm (4.7 in.) from the center of the reflector element, in the corner nearest the active core. 

A very convenient way to extract the laser power is the Littow-mounted grating combined with a mirror at right angle to form a "corner cube reflector" (Fig.3.8). The zeroth order reflection of the grating is used to couple the laser power out of the cavity. This loss is present anyway, and thus we can avoid a partly transmitting end mirror and use a gold coated mirror instead. 

Fig. 5.17a,b. Two examples of possible ring resonators, using total reflection (a) with corner-cube prism reflectors and frustrated total reflection for output coupling (b) three-mirror arrangement with beam-combining prism... 

Foil activation ofl-axis and away from the central plane showed that the fluxes are separable to within experimental error throughout the core. Only in the outer corner of the reflector did the activation increase (by about 40%) over the product of the separated fluxes. 

The worth of a one-foot-diameter central hole in one end reflector was measured to be 0.76% Ak. In the most dilute core (largest fuel radius) the peak power (at the corner of the fuel) was a factor of 1.3 above the core-center power. In the core with a fuel radius of 10.1 in. (0.53 of the cavity radius), the peak power was 3.4 above the core center power. The fraction of fissions occurring above the cadmium cutoff for 0.020-in.-thick cadmium disks (nominally 0.45 eV) was 4.2% and 7.1%, respectively, for these two configurations. 

Figure 4.69 illustrates the principle of a traveling-wave Michelson-type interferometer as used in our laboratory. Such a wavemeter was first demonstrated in a slightly different version by Hall and Lee [184] and by Kowalski et al. [190]. The beams 5r of a reference laser and of a laser with unknown wavelength Xx traverse the interferometer on identical paths, but in opposite directions. Both incoming beams are split into two partial beams by the beam splitters BSl and BS2, respectively. One of the partial beams travels the constant path BS1-P-T3-P-BS2 for the reference beam, and in the opposite direction for the beam Bx. The second partial beam travels the variable path BS1-T1-M3-M4-T2-BS2 for 5r, and in the opposite direction for Bx. The moving corner-cube reflectors T1 and T2 are mounted on a carriage, which either travels with wheels on rods or slides on an airtrack. 

Our primary interest in this calculation is the determination of the critical mass of the hot clean reactor and the radial distribution of the fast and thermal flux throughout the core and reflector. An accurate analysis of this system must necessarily take into account the completely reflected cylindrical geometry shown in Fig. 8.216. However, since this would entail a somewhat involved calculation, we will approximate the actual configuration by an equivalent reflected sphere of the same composition. This will reduce our computation appreciably and yet not obscure any of the essential steps in the application of the two-group model. A study of the effect of the corners in the completely reflected cylinder will be deferred until the next section. 

The principle of long-path absorption techniques is illustrated in Fig. 10.17. A laser beam is transmitted continuously into the atmosphere against a corner-cube retro-reflector (Fig. 6.21) that is placed at a distance of up to 10 km. The reflected beam is received by an optical telescope that is placed at the site of the laser and is directed towards the retro-reflector. The received light intensity is measured photo-electrically as a function of the laser wavelength. The absorption spectrum of the atmosphere between the laser and the retro-reflector is then recorded and the mean concentrations Nj of pollutant molecules can be determined using the Beer-Lambert relation... 

The corner-cube reflectors guarantee that the incoming light beam is always reflected exactly parallel to its indicent direction, irrespective of slight... 

Haze After exposure of each sample to outdoor weathering, haze measurements are to be conducted as per ASTM D1003-61 standard. For plastics used in lamp lenses, haze should not be greater than 30%, while for reflex reflectors or lenses used in front of reflectors, it should not be greater than 7%. In addition, plastics used for headlights (excluding cornering lamps) should also not show any deterioration. 

---