Do I need a 300 GHz scope mow?? ;-)

Pushed to the limit: A CMOS-based transceiver for beyond 5G applications at 300 GHz

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Reply to
Jan Panteltje
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One nasty thing in (sub)millimeter communication is the extremely small capture area of an antenna element (e.g. dipole) It is just a fraction of a square wavelength, i.e. the size of a grain of sand at

300 GHz, thus the power recovered from a specific field strength is minuscule.

Of course parabolic reflectors etc. can be used to collect power from larger areas, but such constructions tend to be too directive, requiring accurate antenna pointing and in practice line of sight.

For any practical link, a multiple element panel is needed by dynamically varying phase shifts from each element to dynamically aim the radiation pattern towards the strongest incoming signal. At these frequencies, you are going to need tens or hundreds individually phase controlled elements to collect enough signal power. The experiment shown in the linked message had only 4 elements, so much more integration is needed.

Reply to
upsidedown

On a sunny day (Sun, 07 Feb 2021 11:29:00 +0200) it happened snipped-for-privacy@downunder.com wrote in :

Yes, phased arrays you see more and more, for example in that SpaceX terminal.

300 GHz (1 mm) is also where infrared starts officially. Use of lenses comes to mind. To dynamically control the phased arrays is not so simply I think. I am even surprised they got CMOS to work at that frequency!
Reply to
Jan Panteltje

Good thing that the team working on CMOS ICs prevailed. In the old days CMOS was deemed to be impossible to get working at high frequencies and high production yield

--
Klaus Kragelund
Reply to
Klaus Kragelund

That is a must if you want to avoid mechanically track the fast moving low orbit satellite with a paraboloid.

There is an overlap in naming conventions. Some call the 1 mm - 0.1 mm (0.3 - 3 THz) as the sub millimeter band or teraherz band. Some even extend it to 30 THz (10 um). However, the 300 K black body spectral peak is at 10 um, i.e. all objects at room temperature radiates these frequencies.

Usable for point to point line of sight with critical mechanical aiming.

You do not have to do the phase shift at 300 GHz. For each antenna element, mix down each individual antenna element with a separate mixer to say 1 GHz and do the phase shifting at1 GHz. A common 299 GHz local oscillator signal is required by all mixers,

The article talks about subharmonic mixers, so the local oscillator is around, 150, 100 or 75 GHz etc. and mixing occurs between the antenna signal and some of the harmonics of the LO. Thus, the only parts working on 300 GHz is the antenna port of the mixer, everything else is at much lower frequencies.

Reply to
upsidedown

On a sunny day (Sun, 07 Feb 2021 14:36:55 +0200) it happened snipped-for-privacy@downunder.com wrote in :

Cool, learning new stuff! Thanks

Reply to
Jan Panteltje

A single EM mode has an etendue of lambda**2/2. (The etendue is the product of area and projected solid angle.) A mode is a single degree of freedom, i.e. in principle it can be coupled losslessly into a one-port network.

Single-mode fibre is sometimes said to have an etendue of lambda**2, but that lumps its two polarization modes together.

That's one of the main reasons that lidar is harder than radar.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

On a sunny day (Sun, 07 Feb 2021 12:35:40 +0100) it happened Klaus Kragelund wrote in :

I am now just wondering if DLP projector chips would work for beam direction steering at 1 mm wavelength, those have a lot of moving micro-mirrors?

That would be fun to program! First hit in google for 'size of DLP projector chips': "New DMD chip for use with DLP projectors that have a native resolution of 1024x768 pixels. This DMD chip measures 32x22mm"

Reply to
Jan Panteltje

They won't do much at 1 mm, because the pitch of the mirrors is much smaller than that. So flopping the mirrors will just produce a subwavelength grating. You'd get a small phase shift, but no more.

Also DMD devices are binary--you use PWM to adjust the intensity of each colour.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

Indeed. Makes a pleasant change to have a constructive, informative and expletive-free comment from an antipodean for once.

Reply to
Cursitor Doom

Is there any way to use your THz diodes as a sampler?

--
John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.
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Reply to
jlarkin

You reckon the Netherlands is the Antipodes now do you?

Mixing down multiple signals from one LO and then comparing/measuring the phase is how the NanoVNAs work. LO up to 6GHz, IF at 5KHz. Then you create your VNA in software in a slow MCU.

Reply to
Clifford Heath

On a sunny day (Sun, 7 Feb 2021 12:46:08 -0500) it happened Phil Hobbs wrote in :

OK, one of the things I have never played with is DLP projectors, there is a video on youtube of somebody using one to put layouts on photo-PCB. So alternative: Bought a I-connect PicoP laser video projector a few years back, it has R.G.B lasers deflected by some mirror system for scanning. Picture is always in focus. But then you start out with an already focused beam. So microwave lens to focus the 300 GHz, then borrow the moving mirror assembly from that projector... An other idea ;-) Else back to thousands of those phased arrays,...

Reply to
Jan Panteltje

How does different materials react to different materials at 300 GHz, how well do they reflect it and which materials absorb it ? This determines how well those signals bounces around within a room and how it behaves outdoors.

In current wireless systems at a few GHz, in urban areas with lot of concrete and brick buildings signals reflect nicely from buildings propagating around several blocks but is absorbed effectively by vegetation in suburban and rural areas.

It is interesting to see how mmWave 5G (25-30 GHz) behaves when it is largely employed in various environments (indoors, urban, rural).

The situation at 300 GHz might still be quite different.

Reply to
upsidedown

On a sunny day (Mon, 08 Feb 2021 09:48:27 +0200) it happened snipped-for-privacy@downunder.com wrote in :

I find a lot of papers with googling for "300GHz propagation"

Reply to
Jan Panteltje

Besides the usual scare tactics of cancer, 5G has some serious problems. Here are some google posts:

Verizon's millimeter wavelength (mmWave)-based 5G, operates at frequencies of about 28 GHz and 39GHz. This is considerably higher than 4G networks, which use about 700 MHz-2500 MHz frequency to transfer information.

Verizon 5G utilizes millimeter wave technology. These millimeter waves exist on an extremely high frequency and are considered millimeter waves because the wavelengths range between 1 and 10 mm.

5G may also utilize ultra-high frequency radio waves between 300 MHz and 3 GHz. 6 Disadvantages of 5G

Obstructions can impact connectivity. The range of 5G connectivity is not great as the frequency waves are only able to travel a short distance.

Initial costs for rollout are high.

Limitations of rural access.

Battery drain on devices.

Upload speeds don't match download speeds.

Many of the old devices would not be competent to 5G, hence, all of them need to be replaced with new one - expensive deal.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  1. 5G does not work on all phones

Of course, it is awesome with super fast internet connections, but unfortunately not all phones have the capacity for 5G. There are a lot of phones out on the market today, which have the right capacity and fortunately the prices of these are starting to drop a bit.

Samsung Galaxy s20Plus and OnePlus 8 are examples of phones with capacity for 5G that have received high ratings from users, but not everyone can afford to invest in a new phone. Apple has not yet launched a mobile phone with capacity for 5G, and iPhone enthusiasts are eagerly waiting for this to happen. If you are sitting on an old mobile phone, you will unfortunately have to open up your wallet if you want to be able to surf with 5G.

  1. More expensive subscription costs

When we are still on the subject of money, we can also mention that many who have variable price plans may experience higher subscription costs. This is for the simple reason that if you can surf at incredible speeds, your subscription will be able to use more data, at a faster pace. We can only hope and believe that the market solves smart subscriptions that allow users to surf in peace, without worrying about sky-high costs.

  1. Uneven coverage

It's not just the very frequency of 5G that makes the network so fast. It is a combination of frequency and the new technology that is in the masts, such as MIMO, beamforming and throughput (read more about these terms here). In order to be able to deliver 5G, new masts must therefore be installed. This is a job that is both expensive and time consuming. In addition, the work has taken even longer in some places, this due to resistance from residents nearby.

For some time to come, many will therefore experience a spotty coverage of 5G.

  1. Replaces battery capacity for speed

When it comes to our smart devices, such as mobiles and VR games, we always want more. We want them to work faster and the battery to last longer. 5G will be a pretty battery-hungry network. This means that manufacturers have to choose whether they want to invest in their devices to have more bulky batteries that last longer, perhaps provide the opportunity to be able to change the battery, or to force users to charge their devices more often.

  1. Few will have access to the really fast 5G

There are different types of 5G. They are usually divided into low-band, mid-band and high-band 5G. Simply put, low-band 5G is slower but has radio waves that reach further. Many places that have low-band 5G deliver internet that is not much faster than what 4G LTE did. However, the masts can sit further apart and still provide an even coverage.

High-band, on the other hand, has a higher frequency, between 25-39 GHz, which provides extremely good internet speed. With high-band 5G you can download an entire series in just a few minutes and it is often up to ten times faster than the WiFi we have at home. But high-band 5G signals do not go very far, this means that carriers need to set up nodes quite close together to be able to deliver consistent coverage. In the cities that have high-band 5G, users today can experience an inconsistency in their coverage and speed.

Further more, the indoor coverage for high-band 5G does not usually make users rejoice. The short wavelengths in the frequency are very bad at getting through things like concrete and metal.

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The best designs are no accident - sw
Reply to
Steve Wilson

Possibly. They'd need thicker oxide than my devices, which were always near 100 ohms.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

While there is a water vapor absorbtion line around 22 GHz. mmWave free space propagation works also on long distances. The problem is how to increase the receiver antenna effective capture area without too much directivity.

A one meter diameter parabolic reflector is quite good for receiving from 36000 km geosynchronous satellite orbit :-).

Preferably you should have a 5G base station in every lamp post (or at least every other lamp post). This will greatly simplify mobile station complexity and power consumption. The base stations also needs to be connected to the internet, so you may have to connect fiber cables to very light pole.

Indeed with a base station in every lamp post :-).

With base stations in every other lamp post along the main road and some mesh networking you can have quite good coverage for those driving along the main road. However, for those hiking in the woods, the coverage is very bad.

Depends on upload/download speed ratio. With a much higher download speeds, the RF power consumption is minimal.

How often do you need high upload speed (and hence high power consumption) ?

As long as the 3G/4G network is running, you still have the sane service as before.

Reply to
upsidedown

You are omitting problems such as inceased battery drain, increased absorption by foliage, and multipath distortion caused by reflections from steel buildings in cities. Continuous reception in cars will be a problem, as well as dead spots in stadiums. User cost will increase due to higher traffic, the cost of replacing phones, and the need to recover the cost of upgrading towers. 5G is not cheap.

5G limitations will become apparent as more areas are developed. Users will find that existing 4G is perfectly adequate, and the cost and unreliability of 5G is not worth the effort. 5G phone sales will plummet, and companies will have to find a better way to attract new customers.
--
The best designs are no accident - sw
Reply to
Steve Wilson

On a sunny day (Mon, 8 Feb 2021 21:12:45 -0000 (UTC)) it happened Steve Wilson wrote in :

From that perspective you might as well put a modulated IR transmitter in every [other] lamp-post for the receive part that is, It will help security cameras see in the dark at the same time, is much cheaper. Tx part via normal 4G. IR high power panels with LEDs are available.

Many years ago some uni in Germany did an indoor experiment with modulated lighting that worked quiet well.

Reply to
Jan Panteltje

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