I am wondering how it is possible to generate 2.4 GHz, if its core clock frequency is much lower than GHz scale.
Electronic – How come esp8266 is able to generate 2.4 GHz wifi signals
esp8266high frequencyRFwifi
Related Solutions
SAW
Impatt Diode
Gunn Diode
Magnetron / Klystron / TWT
Esaki diode (tunnel diode)
fXo
Fractional N synthesiser.
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For $US35.70/1 on stock you can gete 1 GHZ fxo modules from Digikey here for prices.
FXO-PC73 series. Up to 1.35 MHz. Multiply in various ways from there.
Datasheet here They say:
- EXTREMELY Low Jitter
- Low Cost
- Frequency Resolution to six decimal places
- Stabilities to ± 20 PPM
- -20 to +70°C or -40 to +85°C operating temperatures
- Serial ID with Comprehensive Traceability
For $5/1 you can buy synthesiser ICs that cover your range.
Typical example only
Gunn diode oscialltyors using cavities for fequency tuning and with varactors for tuning are a time honoured solution and may give you power levels that can be used directly.
ZAX Gunn oscillators
Zax catalog - very pretty
Gunn XBan - well above your range useful
Ham Radio mag 1980 DIY 10 GHz - very relevant if DIYing here
MUCH more. More detail please. Is this homework. If so, tell us what is being asked of you and we will help you learn.
RF comms do not transmit one bit of information per cycle of the carrier wave - that would be digital baseband communications and it requires incredible amounts of bandwidth. Incidentally, you can buy FPGAs with built-in 28 Gbps serdes hard blocks. These can serialize and deserialize data for 100G ethernet (4x25G + coding overhead). I suppose the 'fundamental' frequency in this case would actually be 14 GHz (data rate/2 - think about why this is!) and they require around 200 MHz to 14 GHz of bandwidth. They don't go all the way down to DC due to using the 64b66b line code. The frequency used to drive the serdes modules would be generated by some sort of a VCO that is phase locked to a crystal reference oscillator.
In the RF world, the message signal is modulated onto a carrier which is then upconverted to the required frequency for transmission with mixers. These balloons probably have a baseband of less than 100 MHz, meaning that initially the digital data is modulated onto a relatively low frequency carrier (intermediate frequency) of around 100 MHz. This modulation can be done digitally and the modulated IF generated by a high speed DAC. Then this frequency is translated up to 24 GHz with a 23.9 GHz oscillator and a mixer. The resulting signal will extend from 23.95 to 24.05 GHz, 100 MHz of bandwidth.
There are many ways to build high frequency oscillators in that band. One method is to build a DRO, which is a dielectric resonance oscillator. Think of this as an LC tank circuit - there will be some frequency where it will 'resonate' and either generate a very high or very low impedance. You could also think of this as a narrow bandpass filter. In a DRO, a piece of dielectric is used - usually some sort of ceramic, I believe - that resonates at the frequency of interest. The physical size and shape determine the frequency. All you need to do to turn it into a frequency source is add some gain. There are also ways of using special diodes that exhibit negative resistance. A Gunn diode is one example. Biasing a Gunn diode correctly will cause it to oscillate at several GHz. Another possibility is something called a YIG oscillator. YIG stands for Yttrium Iron Garnet. It is common to build bandpass filters by taking a small YIG sphere and coupling it to a pair of transmission lines. YIG happens to be sensitive to magnetic fields, so you can tune or sweep the center frequency of the filter by varying the ambient magnetic field. Add an amplifier, and you have a tunable oscillator. It's relatively easy to put a YIG in a PLL. The power of a YIG is that it is possible to use it to produce a very wide band smooth sweep, and hence they are often used in RF test equipment such as spectrum and network analyzers and sweeping and CW RF sources. Another method is to simply use a bunch of frequency multipliers. Any nonlinear element (such as a diode) will produce frequency components at multiples of the input frequency (2x, 3x, 4x, 5x, etc.). Stringing together a chain of multipliers, bandpass filters, and amplifiers can be used to produce very high frequencies.
Related Topic
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- Electronic – 802.15.4 – how are the baseband and RF signals related
- Electrical – disabling CSMA/CA protocol in esp8266 or any other wifi ic
- Electronic – Can a Wifi device be made to output a continuous 2.4 GHz wave
- Electronic – WiFi antenna understanding, which is 2.4, 5 GHz
Best Answer
The radio contains a voltage controlled oscillator that is locked to an external reference oscillator using a phase locked loop (PLL). This results in a very precise high frequency signal for the radio on the chip. The radio will use one or more oscillators to upconvert and downconvert the signal to the required RF channel. This will be entirely distinct from the actual CPU clock, though it is possible the CPU clock is derived from the same reference clock. It's the same story for any device with a radio; the digital logic that directly interfaces with the radio usually only runs at a few 100 MHz or less, even if the radio operates in the 2.4 or 5 GHz bands.
The most important thing to remember about radio communications is that even though the channel can be located at a high frequency, the channel is quite narrow. In the case of Wi-Fi, the channel may be centered between 2.4 and 2.5 GHz, but it is only 20 MHz wide (or perhaps 40 or 80 if multiple channels are bonded in newer standards). Since the band is only 20 MHz wide, most of the signal processing ony operates up to around 20 MHz. If there are ADCs and DACs, they will probably only run at 100 Msps or so. Any DSP circuitry will run at this rate as well. Mixers will then be used to convert between this 'baseband' and the actual RF channel.