Details on Doppler Radar Illumination

Ideally, a fixed-position motion detector with no beam steering capability would possess an illumination pattern of 10 degrees vertical and 90 degrees horizontal. Since people and vehicles move in the horizontal plane, it is logical to focus the illumination energy to a narrow vertical beam and a wide horizontal beam. For visualization purposes, a virtual environment in a Computer Aided Form Synthesizer is seen in the following images. The ground is textured with green grass and extends 100 meters in front and 30 meters in back and 400 meters wide of the virtual illuminator which intersects a 400 x 400 meter gray curtain 2 meters below a dividing line at the horizontal mid point. A horizontal line on the curtain is level to the illuminator.

 

The figure on the left shows a synthesized elliptical mask illuminated from behind which is where we see it here. The light source is conical and is adjusted so that it shines directly through the center of the shadow mask forming an elliptical beam. The two figures to the right are seen from the front side. These two shadow masks form a 30x60 Degree Pattern and a 10x90 Degree Pattern respectively. These two elliptical Illuminating Projectors are 100 meters from the virtual 400 x 400 meter curtain. Notice the tiny spot in the center of each elliptical pattern, these are each a virtual microwave projector.

 

Description of the projectors

 

Close-up of the 30x60 Degree Pattern Virtual Projector. By placing a point source light behind an elliptical hole in a membrane, a virtual projector illustrates the illumination pattern of a typical microwave horn. If the elliptical hole has a ratio of 2 wide and 1 high, placed at the proper distance from the imaginary center of the hole, a reasonable illumination simulator may be used to demonstrate a viable Doppler illumination pattern.

30x60 Degree Pattern 50x100 meters The virtual projector produces a + and - 30 degree spot along the horizontal axis of the projector, the typical illumination pattern of a microwave horn.

10x90 Degree Pattern 20x170 meters with a ratio of 1 high by 9 wide (more desirable). The virtual projector produces a + and - 45 degree spot along the horizontal axis of the projector.

30x60 Degree Pattern. The elliptically shaped beam leaves the virtual projector as an illumination beam 30 degrees vertical (50 meters) and 60 degrees horizontal (100 meters) as measured from the point source illuminator. Notice the small gray spot near the center of the elliptical light patch. This is the simulated 6-foot human in Figure 12 standing in front of a simulated curtain that is 400 meters by 400 meters perpendicular to the axis of the illuminator. Notice the virtual projector in the foreground with the glow of the illuminator emanating toward the curtain. Again, the virtual projector is 100 meters from the curtain. This relates the size and scale of the distances described.

10x90 Degree Pattern. The elliptically shaped beam emanates from the virtual projector as an illumination beam 10 degrees high and 90 degrees wide as measured from the point source illuminator. This pattern is not typical of off-the-shelf microwave feed horns. The pattern is almost twice as wide as a typical 30x60 pattern yet more than doubles the beam intensity along the horizontal axis and doubles its effective range. This allows better coverage of the area of interest from the typical 30x60 Pattern feed horn and also limits clutter.

MIR/TM-UWB 50 meter radius Spherical Pattern. (Micro-power Impulse Radar (MIR) and/or Time modulated Ultra Wideband (TM-UWB) RADAR)The illumination pattern of an atypical high power MIR. A typical low cost off-the-shelf MIR has an effective range of 4 meters. The theoretical effective range of an MIR using low power semiconductors is 50 meters. The sphere of light is 50 meters in radius, 1/2 way to the curtain. There is some pulse radiation falling on the human figure (the tiny spec) in front of the virtual curtain characterized by the dim illumination on the virtual curtain but the MIRís effective range falls far short of the distance to the virtual curtain.

 

The down side of MIR/TM-UWBs. MIR/TM-UWBs seem to be the natural choice for 3D imaging but current COTS (Commercial-Off-The-Shelf) MIR/TM-UWBs have very limited range rendering them inappropriate for this proposal without further investigation. Limited range is intentional, for precise imaging with resolutions in unit inches required to detect humans. It may be possible to create a custom MIR/TM-UWB to be effective at the illustrated distance of 100 meters and beyond but the author has not discovered a working commercial unit that specifies this capability without cumbersome, massive, and awkward apparatus as indicated in the significant Patents. This effective distance would be seriously impeded by buildings indicating the need for even higher output power. MIRs exhibit a limitation, not because of their semiconductors but from the laws of physics, as follows. Resolution and distance are inversely proportional. The lower spatial resolution is caused by longer time between return of transmitted pulses. To image human subjects at 100 meters would take very high-precision measurement of the return pulses. This would make the impulse detection scheme very vulnerable to multipath problems. Many Patents have evolved addressing this problem in a vain attempt to overcome this deficiency in impulse radar. Many different schemes have been demonstrated, array antennae, multiple transmitters, array receivers, 3 dimensional processing (reflectograms), orientation reflectors; all have significant drawbacks for RSTA (Reconnaissance, Surveillance and Target Acquisition ) compared to Doppler radar.

2x2 Degree Pattern. By placing a 10.525 GHz DIR (Doppler Illuminating Radar ) in a fourteen inch Direct Broadcast Satellite offset dish or by using a 35.5 GHZ Gunnplexer where no dish is required, a spot beam illuminator is formed. This allows the user to illuminate highly selective distant areas like through doorways, through windows, long straight streets, long straight roads, highway intersections, tar macadam, single vehicles or aircraft, and along fence lines. RADAR PC has also successfully demonstrated the ability to detect human movement through most walls and doors. At distances of 30 meters, RADAR PC use of a low power radar detects movement inside buildings. If used from inside a building, movement is successfully detected through walls in immediately adjacent buildings or rooms. Used outside, with the adaptation of a high power DIR, this scheme may operate for tens of miles using the authorís software allowing detection along an entire ridgeline or mountain, especially if used with a look-down periscope.
Simulated subject illuminated by 2x2 Degree beam
. At 100 meters, the 2 degree beam is seen as the bright area in the middle of the image. However, radiation spills outside the 2 degree arc. This is seen as the glow around the bright patch. The grass is illuminated in the foreground. By focusing the beam with a dish, the effective range is multiplied from 30 to 500 times, depending on the size of the dish, at the sacrifice of wide area horizontal coverage. It is typical to detect people walking using a 10 milliwatt illuminator at 500 meters.