How to generate UHF signals (1GHz - 10GHz)? - Page 1
Forum section: electronics / beginners

author: Tantal
author_rank: Contributor
timestamp: May 27, 2015, 11:37:59 pm
content: My first idea was to get VCO and an Amp (MMIC). But VCOs in the GHz range are first hard to find and second very expensive.E.g. this one here ZX95-2650 costs about 45$http://194.75.38.69/pdfs/ZX95-2650+.pdfBut maybe I'm searching in the wrong area. So general question: How do I generate high frequency signals?

author: Howardlong
author_rank: Super Contributor
timestamp: May 27, 2015, 11:50:52 pm
content: What is your application?Do you really need the entire 1-10GHz covered, or just one segment within there?What sort of frequency stability do you need?How much phase noise/jitter can you tolerate?

author: Tantal
author_rank: Contributor
timestamp: May 28, 2015, 12:14:40 am
content: Quote from: Howardlong on May 27, 2015, 11:50:52 pmI just like to start experimenting with UHF/microwave. First goal would be a Beacon. Final goal would be a Doppler Radar (some day far in the future).QuoteNo, no, not the full band. Could be 2GHz, could be 6GHz, etc. Plus some modulation (a few hundred kHz).QuoteDon't care to much (at least not for now).

author: xrunner
author_rank: Super Contributor
timestamp: May 28, 2015, 12:41:32 am
content: By definition, HF is from 3 to 30 MHz.1 GHz would be UHF, and 10 GHz would be SHF.http://en.wikipedia.org/wiki/Radio_spectrum#ITU

author: Tantal
author_rank: Contributor
timestamp: May 28, 2015, 12:44:20 am
content: Quote from: xrunner on May 28, 2015, 12:41:32 amThanks. I've changed the subject line

author: BennVenn
author_rank: Regular Contributor
timestamp: May 28, 2015, 01:44:12 am
content: You can pick up doppler radars running around 10.5ghz on ebay for a few dollars. There are a few sites that document the conversion to microwave data trancievers. Frequency is modulated via supply voltage and is course tuned via a slug in the oscillator. They output a doppler signal as the oscillator is used for both tx and the rx L.O.Having two modules running at different freqs gives an I.F on the doppler output which if set around 90mhz can be detected via a standard FM radio.

author: hagster
author_rank: Frequent Contributor
timestamp: May 28, 2015, 05:18:07 am
content: Just a thought. You could use a SDR radio like HackRF or Ettus B200. You would be limited to 6Ghz though.

author: tggzzz
author_rank: Super Contributor
timestamp: May 28, 2015, 09:44:33 am
content: Quote from: Tantal on May 28, 2015, 12:14:40 amYou might be interested inhttp://hforsten.com/6-ghz-frequency-modulated-radar.html

author: VK5RC
author_rank: Unknown
timestamp: May 28, 2015, 10:31:57 am
content: One of my favourite general oscillators for higher frequency work is Down East Microwaves A32 board, it can generate a series of frequencies, switch selectable and if connected to a reasonable 10MHz source reasonably stable, not crazy money either.http://www.downeastmicrowave.com/product-p/a32.htmPS While the unit stops at about 1GHz the harmonics are relatively rich and can be filtered.

author: LukeW
author_rank: Frequent Contributor
timestamp: May 28, 2015, 06:14:18 pm
content: It depends what your requirements are.http://www.digikey.com/product-detail/en/MAX2751EUA%2B/MAX2751EUA%2B-ND/1512362Here's a microwave VCO for a few dollars.If you want cheap, then you'll get cheap by focusing on parts of the spectrum that see large-scale commercial products using it - for example the 2.4 GHz spectrum, or the GPS bands which have cheaply available LNAs, for example. Of course, remember that you should be a "good citizen" of the RF spectrum, as well as following law in your country, when it comes to using the spectrum and choosing the components you want to use.Things like connectorised building-block VCO modules from places like Mini-Circuits will be significantly more expensive than chip-level components - other than the SMA connectors and shielding case, you're also paying for not having to design anything yourself - no RF test equipment or microstrip layout expertise needed, you can have confidence that the module works as specified and it can be used as a building block - you don't have to worry about power supplies, 50 ohm transmission lines, connector, housing, the right PCB substrate etc.http://www.microwavejournal.com/articles/2660-a-wideband-varactor-tuned-microstrip-vcoThere is also the option of making something from scratch yourself, such as a discrete varactor based VCO.

author: Dago
author_rank: Frequent Contributor
timestamp: May 29, 2015, 05:08:15 am
content: You could always use a synthesizer chip like ADF4351 too which is an integrated PLL+VCOhttp://www.analog.com/en/products/rf-microwave/pll-synth/adf4351.htmlYour question is bit hard to answer because there are many many ways to generate microwave range RF but all the methods have their merits and downfalls, without specifying what you want it is hard to rule any out.

author: Tantal
author_rank: Contributor
timestamp: May 29, 2015, 12:59:51 pm
content: Thanks a lot!Quote from: LukeW on May 28, 2015, 06:14:18 pmOK, so I'll focus, for a start, on 2.4 GHz then. Which part (VOC) would you recommend?QuoteDo you have a link on how to do that?

author: richard.cs
author_rank: Super Contributor
timestamp: May 29, 2015, 04:00:26 pm
content: HF crystal oscillator and many stages of frequency multipliers - doublers and tripplers are pretty easy.Alternatively rip apart a satellite TV downconverter, they normally have dielecric resonantor oscillators inside. Note that being cheaply made they're not particularly stable in frequency, especially with temperature. They just let the IF wander around and the receiver follows it. Common LO frequencies are 5.15, 9.75, 10.6, 10.75 and 11.25 GHz.Also take a look athttp://www.kuhne-electronic.de/en/home.html- they publish schematics for many of their products (quite a few of which have also been published in amateur radio magazines).

author: Howardlong
author_rank: Super Contributor
timestamp: May 29, 2015, 07:31:42 pm
content: For the KISS principle, you could try thishttp://www.g0mrf.com/source2.htmWhen connected to a well located antenna, it can be picked up from quite some distance, ISTR a couple of km or so was achieved with a reasonably sensitive narrowband receive setup. Of course, being a comb generator, one would be using a filter with that, and have an appropriate licence for the filtered frequency if necessary.The 2.4GHz noise floor is pretty bad nowadays unless you're out in the sticks. When those experiments were conducted around 2000 or so, WiFi wasn't anywhere near as ubiquitous as it is nowadays.

author: Tantal
author_rank: Contributor
timestamp: May 30, 2015, 09:43:07 am
content: Quote from: Howardlong on May 29, 2015, 07:31:42 pmI live pretty much in the middle of nowhere - so I only might to kill my own WiFi

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 30, 2015, 12:32:25 pm
content: At what power level? Gunn diode, yig, BWO, Klystron, etc...

author: n9zl
author_rank: Unknown
timestamp: May 30, 2015, 06:39:48 pm
content: I first started playing in SHF with 10mW Gunnplexer modules. I built a 10GHz beacon, a Doppler radar gun, and a pair of transceivers.You can find the modules on ebay and other places, they're pretty cheap, they typically tune over several GHz mechanically, and a few hundred MHz electrically and are very simple to work with. They contain a microwave diode that oscillates at microwave frequencies when power is applied. Varying the supply voltage will change the frequency a bit. Better (more expensive) units have a separate tuning control input for modulation.The great thing is a gunnplexer forms a mixer by using its own transmitter as a local oscillator. To make a radar gun, you just hook up an audio amplifier, or an audio frequency counter. When you point the gunnplexer at a moving vehicle, the outbound 10GHz bounces off the car at a slightly different frequency, comes back, and mixes with the original signal to give you an audio signal corresponding to the speed of the car. The tone is about 30 Hz per mile per hour as I recall.The beacon simply keyed a gunnplexer with a tone modulated power supply and sent morse code. I could hear it 12 miles away on a mountaintop.Making a two way communication system was harder. I offset two gunnplexers by about 30MHz, then used wideband 30MHz FM receiver boards to demodulate the gunnplexers. The hardest thing here is gunnplexers are not very frequency stable with temperature, so you have to use a wideband signal so you don't have to chase it all over the band. I made a line of sight voice contact over several miles with mine. I tried to send video over it, but I had trouble coming up with a modulator scheme that could handle the bandwidth required.Lots of fun.