Value chain · CLM-1123
In plain terms
A five-metre dish and a 100 kW radar-type pulsed tube a kilometre away, bounced partly off the ground on purpose to get more power onto the receiver, then deliberately blurred so the diodes would not be burnt out: about 550 watts per square metre landing on the array, from a beam that could have delivered three times that.
The claim as recorded
The conditions under which the NRL 2022 array was measured: a 5.4 m parabolic reflector with "focal length is 2 m", a horn feed with a "17 dB amplitude taper from the center to the edge" on a linear actuator ("100 mm range along the reflector's axis") that focuses the beam at a chosen near-field distance, fed by a "9.7 GHz, 100 kW magnetron oscillator" at "the maximum pulse duration is 1" us and "604 Hz repetition rate", to a receiver "separated by 1046 m" over rugged terrain at Blossom Point, MD; a deliberate ground bounce gave a measured "2.3 dB (70%)" enhancement against a 2.73 dB parabolic-equation prediction; focused, "The peak power density is 1643 W/m2", but the MA4E1317's maximum input makes "the estimated maximum power handling of the rectenna array (neglecting losses in the microstrip antenna and matching network)" 444 W/m2, so the feed was defocused by 40 mm to "552 W/m2 power density at the center of the target area" and 2265 W integrated over the array, with a steel dumpster at 262 m in the line of sight; the forward and reversed links agreed "within 0.20 dB".
Evidence behind this: T1-peer-reviewed measured link conditions with the instruments named; the ground-bounce prediction beside it is the authors' model (T2 grade) and is marked as such.
Scope and limits
PULSED, NOT CONTINUOUS: every Blossom Point figure is a 1 us pulse at 604 Hz (duty 0.06 per cent), because no kW-class CW source was available during the pandemic (PDF 2); the densities are peak-of-pulse. The mean incident density of 509 W/m2 is 15 per cent above the 444 W/m2 diode-limited estimate and the array survived it, so the estimate is conservative by the paper's own later test. The ground-bounce gain is site-specific and the paper says the optimum geometry "is not general" (PDF 5, raw).
What it assumes
The 444 W/m2 is the authors' estimate from the diode's 20 dBm specification and the element area, not a measurement (CLM-1126 measures the actual limit).
Where it comes from
PDF 2 / printed 29: "separated by 1046 m" (raw); a 5.4 m diameter parabolic reflector, originally designed as a Cassegrain antenna and reconfigured to use a standard axial feed (R1); "The reflector's focal length is 2 m" (R1); "17 dB amplitude taper from the center to the edge" (normalised); "vary over a 100 mm range along the reflector's axis" (R1); "9.7 GHz, 100 kW magnetron oscillator" (normalised); "the maximum pulse duration is 1" (normalised) us; "604 Hz repetition rate" (raw). PDF 7 / printed 34: "a 100-kW pulsed power amplifier (PA) feeds the 5.4-m reflector antenna" (R1); "A calibrated horn with 10.95 dBi gain at 9.73 GHz samples the power density at 1046-m standoff" (R1); "Identical LadyBug LB680A power meters" (raw). PDF 8 / printed 35: "is 2.3 dB, which although slightly less than the predicted value of 2.7 dB" (normalised); "The peak power density is 1643 W/m2" (raw); the estimated maximum power handling of the rectenna array, neglecting losses in the microstrip antenna and matching network, is given as 444 W/m2 (normalised); "providing a mechanism for controlling power density over a >10 dB range" (normalised); "552 W/m2 power density at the center of the target area" (raw); a 2 x 1.3 x 1.7 m steel dumpster left directly in the transmitter's line of sight at 262 m standoff (normalised). PDF 9 / printed 36: "array at this 40 mm feed displacement is 2265 W" (raw); "shows agreement within 0.20 dB" (normalised). PDF 5 / printed 32: "predicting a 2.73 dB increase in maximum power density" (raw). PDF 1: the abstract states a "2.3 dB (70%)" enhancement in power density at the target site by deliberate exploitation of a ground bounce (normalised). Recomputed: 10^0.23 = 1.70; 2 x 5.4^2 / 0.0309 = 1,887 m far field, 1,046 / 1,887 = 0.55; 1,643 / 552 = 2.98 (4.7 dB); 2,265 / 4.45 = 509 W/m2 mean; 0.1 W / 2.28 cm2 = 439 W/m2 against the stated 444.
Basis: m; GHz; kW; us; Hz; dB; W/m2; W
Cite this
energyaperture.com/c/clm-1123
CLM-1123, Energy Aperture, as of 2022-01.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-270
- CLM-1122About twenty thousand postage-stamp-sized antenna-plus-diode cells, each with an off-the-shelf microwave diode, wired into tiles, then...CLM-1124One panel the size of a sheet of paper turned about seven-tenths of the microwave power landing on it into DC, and did best at about three...CLM-1125Four square metres of receiver turned 73 per cent of the microwave power arriving at it into 1.65 kW of DC, measured a kilometre from the...CLM-1126They deliberately fried each of the four panels with ever-stronger pulses. A bare panel gave up at 672 watts out; clamping its voltage with...CLM-1127As flown, under two per cent of the microwave power fed to the dish came out of the receiver as electricity, because the beam had to be...CLM-1128A second test used a big radar dish in Massachusetts to light up a strip of LEDs on a tower over a kilometre away, with about a kilowatt...CLM-1129The authors say the 1975 record still stands at twenty times their power, that the custom diodes which set it no longer exist, and that...CLM-1130A quick way to size a ground-to-ground beam: at the distance where the dish stops focusing, the cone holding half the power is about twice...More on the source page.