Value chain · CLM-1127
In plain terms
As 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 blurred to protect the diodes. The authors' arithmetic says a properly focused beam onto a receiver seven to twenty-two times larger would get a quarter to nearly half of it through; nobody has built that.
The claim as recorded
NRL 2022 measured end-to-end: "The overall link efficiency (i.e., the ratio of rectenna output power to the RF power input to the transmitter) demonstrated experimentally is 1.8%" (Table 2: 91.2 kW RF into the antenna, 17 dB taper, 4.49 m2, 2.27 kW incident, 1.65 kW out), the loss being deliberate defocusing forced by the limited power handling of commercial Schottky diodes, which forced the beam to be spread so that the density at the rectenna stayed in the 500 to 600 W/m2 range; the authors then project, at the same transmit efficiency, Case B "reduces the RF transmit power by 4.4 dB so that the beam can be fully focused on the rectenna without destruction, increasing link efficiency to 5%" (33.0 kW in, 1.65 kW out), Cases C and D "further increase link efficiency to 25% and 44%, respectively, by using larger rectennas" (30.2 m2 and 101 m2 at 30.6 kW in, 8.11 and 14.6 kW out), and Cases E and F with a uniform (0 dB) aperture reach the same outputs on 18.6 and 53.0 m2, showing "what would be reasonably achievable with a spatially combined architecture".
Evidence behind this: T1 for the measured 1.8 per cent; the Cases B-F are the authors' projections (T2 grade) and the record says so line by line.
Scope and limits
CASES C-F DO NOT RECOMPUTE ON THE PRINTED INPUT: 8.11 / 30.6 = 26.5 and 14.6 / 30.6 = 47.7 per cent against the printed 25 and 44, which reproduce on 33.0 kW (24.6, 44.2); read at the zoom-5 crop, not a power-of-ten mismatch, recorded and not repaired; the table's own note says "Cases C and D are the same as Case B, but with larger rectenna arrays" while printing 30.6 kW for C and D against B's 33.0 kW, so the page's inputs and its percentages cannot both be as printed. The projected rectenna efficiency (53 per cent) is well below the measured 73 (CLM-1125) and the paper does not say why; Case E's 823 W/m2 incident is above the 500-600 W/m2 the text says the diodes required. Cases B-F are arithmetic, not demonstrations, and the abstract's "should readily scale" rests on them. The 1.8 per cent excludes the DC-to-RF conversion of the magnetron and everything upstream.
What it assumes
The projections hold transmit efficiency at the 17 dB taper value and rectenna efficiency at about 53 per cent; the 91.2 kW is the RF at the antenna input, not the magnetron's 100 kW rating.
Where it comes from
PDF 11 / printed 38: "The overall link efficiency (i.e., the ratio of rectenna output power to the RF power input to the transmitter) demonstrated experimentally is 1.8%" (R2); the limited power handling of commercial Schottky diodes, which forced the beam to be spread so that the density at the rectenna stayed in the 500 to 600 W/m2 range (R1); Case B, the paper says, reduces the RF transmit power by 4.4 dB so that the beam can be fully focused on the rectenna without destruction, raising link efficiency to 5 per cent (R1); Cases C and D raise link efficiency further, to 25 and 44 per cent respectively, by using larger rectennas (R2); the paper says a uniform amplitude distribution is impossible with a reflector and presents Cases E and F as what a spatially combined architecture could reasonably reach (R1); the paper calls the estimated output power and efficiency in these cases conservative because the same transmit efficiency is used as for Cases A, B, C and D (R1). PDF 12 / printed 39, Table 2 (crop read): This Work 91.2 kW / 17 dB / 4.49 m2 / 2.27 kW / 1.65 kW / 1.8%; Case B 33.0 kW / 17 dB / 4.49 m2 / 2.27 kW / 1.65 kW / 5.0%; Case C 30.6 kW / 17 dB / 30.2 m2 / 15.3 kW / 8.11 kW / 25%; Case D 30.6 kW / 17 dB / 101 m2 / 27.6 kW / 14.6 kW / 44%; Case E 30.6 kW / 0 dB / 18.6 m2 / 15.3 kW / 8.11 kW / 25%; Case F 30.6 kW / 0 dB / 53.0 m2 / 27.6 kW / 14.6 kW / 44%; the note says that in Case B the RF transmit power is reduced so that the beam can be fully focused on the rectenna without destruction (raw). PDF 1: the abstract says the results "should readily scale" to higher levels of power and performance (normalised). Recomputed: 1.65 / 91.2 = 1.81 per cent; 91.2 / 10^0.44 = 33.1 kW; 1.65 / 33.0 = 5.0 per cent; 1,643 / 10^0.44 = 597 W/m2 focused at Case B power; 8.11 / 15.3 = 53.0 and 14.6 / 27.6 = 52.9 per cent projected rectenna efficiency; 15.3 / 30.6 = 50 and 27.6 / 30.6 = 90 per cent projected collection; incident densities 506, 507, 273, 823, 521 W/m2 for B, C, D, E, F.
Basis: per cent of RF input to the transmit antenna delivered as DC; kW; m2; dB taper
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-1127
CLM-1127, 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-1123A 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...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-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.