"Metallic Delay Lenses" paper (1948) - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: January 12, 2018, 01:52:40 am
content: From the venerable Bell System Technical Journal, no less.https://ia801604.us.archive.org/18/items/bstj27-1-58/bstj27-1-58.pdf

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 14, 2018, 12:37:00 am
content: Wow, that's amazing!

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2018, 01:26:07 am
content: This is an ancestor in spirit of "metamaterials"also something Copper Cone has discussed here, the use of RF absorbent materials in gradients.Also called "stealth" materials.Which can be surprisingly easy to make if you like me, use filters for your drinking water, they come with quite a bit of activated carbon which can be used in projects.. You can use the spray foam you buy in cans to make layered foams with different densities of carbon. It sort of works.I was trying to make a better GPS antenna.

author: CopperCone
author_rank: Super Contributor
timestamp: January 14, 2018, 08:59:17 pm
content: that stuff looked like it was really fun to build.

author: cdev
author_rank: Super Contributor
timestamp: January 15, 2018, 12:05:41 am
content: Quote from: CopperCone on January 14, 2018, 08:59:17 pmIt must have been, totally..Have you ever heard of a Luneburg lens?Very similar concept.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 15, 2018, 12:25:02 am
content: There were several commercial implementations. For example the JBL "venetian blind" acoustic lens:And the "potato masher" lens:

author: KE5FX
author_rank: Super Contributor
timestamp: January 15, 2018, 01:06:48 am
content: What will really bake your noodle is how much this hardware resembles the polarizers and collimators used by Bosearound fifty yearsearlier.

author: LaserSteve
author_rank: Super Contributor
timestamp: January 15, 2018, 07:31:21 am
content: Delay lenses were used for the first transcontinental microwave links in the US.. They were later replaced by the famous KS-15676 Horn..Dr. Winston Kock worked in sonar, radar, microwave communications and holography. His lenses and textbooks are amazing.He created a method of visualizing sound waves with a neon lamp, a signal generator, and a scanning microphone that makes amazing pictures using a camera with an open shutter..Steve

author: cdev
author_rank: Super Contributor
timestamp: January 17, 2018, 01:57:36 am
content: That sounds interesting! Do you have any links? is it anything likehttps://en.wikipedia.org/wiki/Schlieren_photography?Quote from: LaserSteve on January 15, 2018, 07:31:21 am

author: LaserSteve
author_rank: Super Contributor
timestamp: January 18, 2018, 08:29:45 pm
content: Easy, make a pivoted arm that scans vertically through the near field signal to be mapped from your speaker or microwave horn/lens.. Place microphone or detector diode on the tip of the free end of the arm. Koch used a neon lamp, but these days we have LEds.Place the light just behind the detector on the wooden pivoting arm.The above is your Y scanning axis, and drive the arm with a motor or a pully and string.The X axis is the pivoted arm described above, mounted on a cart on a track.The lamp is driven by a mixer, amplitude detector, or phase detector , depending on what you seek.The signal source is a reasonably stable, coherent, oscillator split between the sending transducer and providing a phase reference to whatever drives the lamp.Place a camera at right angles to the track in a darkened room.Turn everything on. Set the camera on " bulb" if using film and open the shutter. These. Days you'd use "integrate, average, or time exposure" on a digital camera.Leave the shutter open. Sweep the arm,Move the cart back, sweep the arm, then repeat as needed.Close shutter when done.The wave will show up as a series of light and dark spaces proportional to amplitude and phase of the signal in your time exposure.Makes really neat near field plots with short wavelengths.If you Google "koch bell labs sound " in "Googlr images" something will pop up.Steve

author: cdev
author_rank: Super Contributor
timestamp: January 18, 2018, 09:43:02 pm
content: Something like that seems like a useful technique in a number of different kinds of measurements.For example, "poor mans thermography" might be done with a non contact thermometer in a manner something like that, using a RGB LED, maybe to display the color mapped output.