Value chain · CLM-0992
In plain terms
The receiving field on the ground makes its own harmonics: the diodes that turn microwaves into electricity also generate signals at two, three and four times the frequency and send some of it back out. Early measurements put the strongest of these at about three hundred times weaker than the main beam.
The claim as recorded
The rectenna re-radiates harmonics of its own: Arndt and Leopold report that "harmonics of 2.45 GHz will be generated within the half-wave rectifying diodes and will be reradiated back through the low-pass filters and dipoles", with initial measurements putting the 2nd, 3rd and 4th harmonics at -25 dB, -40 dB and more than 70 dB down (printed "<-70 dB") relative to the fundamental "for the normal dipole/diode rectifier configuration". This is a third harmonic dataset, from the ground receiver, distinct from the transmitter-tube harmonics of SRC-451 and from the band-collision analyses.
Evidence behind this: T3-proceedings reprinting a 1978 paper that reports "initial measurements" without the measurement's conditions.
Scope and limits
"INITIAL MEASUREMENTS" WITH NO STATED CONDITIONS, ELEMENT OR POWER LEVEL, IN A REPRINTED CONFERENCE PAPER; MED for that reason. Relative to the fundamental at the rectenna, not a flux density at any distance; converting it to an interference level needs the rectenna's re-radiation pattern, which the paper does not give. The page attributes the measurements to Brown's 1977 receiving-terminal report (NASA CR-135194, its Ref 4), which is where the element, power level and conditions would be found; that report is held as SRC-558 (NASA CR-135194, Raytheon PT-4964, August 1977), and its conditions are now recorded: one RXCV element at 5 W in a ground-plane fixture, at the input terminals, with the fourth-harmonic figure the instrument's floor (CLM-1095).
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.242, raw: "Harmonics of 2.45 GHz will be generated within the half-wave rectifying diodes and will be reradiated back through the low-pass filters and dipoles. Initial measurements of the harmonic levels relative to the fundamental indicate the 2nd, 3rd, and 4th harmonics are down by -25 dB, -40 dB, and <-70 dB respectively for the normal dipole/diode rectifier configuration (Ref 4)." The text layer prints "~-70"; the render reads "<-70". Ref 4 on PDF p.245 is Brown, NASA CR-135194, August 1977.
Basis: dB below the fundamental, re-radiated by the rectenna
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-0992
CLM-0992, Energy Aperture, as of 1978.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-516
- CLM-0988The rule that radio astronomers hold the satellite to is a specific international report, and its limit near the satellite's frequency is...CLM-0989The same figure, minus 160, appears in two 1970s papers meaning two different things: in one it is the noise reaching the ground, in the...CLM-0990The extra twenty decibels of noise suppression for a fleet assumes a hundred satellites. The government's reference plan was sixty, which...CLM-0991In 1978 the frequency band the satellite was to use was an industrial free-for-all band in the West, where users must put up with each...CLM-1091The people running the programme said 2.45 GHz was sensible and also said, in the same breath, that nobody international had agreed to it...CLM-1222The fourth paper the 1978 design cites for its beam limit also calls the limit a theory that had not been tested. The one experiment it...