> Yes. Compared to MPSK. MPSK [Multiple Phase Shift Keying] is digital >> phase modulation.
> It is? There were certainly plenty of, e.g., QPSK and BPSK systems >while analog still dominated communication systems. I expect there >were even, e.g., 16-PSK systems done in analog, although I can't >personally give you an example of one.
Any PSK, FSK, ASK are digital. They use 1s and 0s. So they are digital.
Please tell me how MPSK can't be digital. The phases are determined by the 1s and 0s. So again, how can't MPSK be digital????
Wikipedia confirms that PSK is digital, not analog. PM is the analog equivalent of PSK. Don't know what you're thinking. No offense.
Huh? What are you saying? Yes AM, FM, and PM can be used to convey digital convey info, but then they would be mASK, mFSK, and mPSK, respectively. If the digital info is binary, then there would be just ASK, FSK, and PSK without only 2 states.
Not true -- direct sequence spread spectrum is used both with digital data and analog data quite routinely.
You're suffering from the common problem today of assuming that just because you only know of one item that's a certainly way (QAM being both digital and analog), it's the only possibility out there. This is rather arrogant bordering on rude...
Ok, but if the DSSS uses bits, then its digital. If it doesn't use bits, its analog.
I'm sorry if that's how you feel. I wasn't trying to be rude. I was simply curious as to how something with bits, 1s and 0s, can be considered analog or non-digital.
About QAM, my guess is that analog QAM uses PM and AM, while digital QAM uses [M]PSK and [M]ASK. I could be wrong though.
It uses both... for the simplest form of BPSK, you take an analog signal and invert it or not based on a long digital bitstream. In other words, you have a fully analog, continuous time signal f(t) that you simply multiple by +1 or -1 for discrete units of time.
The problem is that you're trying to take one label ("analog" or "digital") and apply it to big systems. Hence the initial confusion of people not being clear on whether you were talking about digital *modulation* methods or digital *generation* methods... the confusion comes about because, by the time you hit an antenna you always have an analog signal, so you have to be clear on where in the radio you want to examine as to whether you're expecting digital or analog signals.
I think the word you want to toss in here is "quantized" -- it's a little clearer than "PSK" or "ASK." "Analog QAM" doesn't use quantized amplitudes or phases, whereas "Digital QAM" does. Note that if someone hands you an "analog QAM" system -- it has a couple of connectors labeled "amplitude" and "phase" -- it's easy to turn it into a digital QAM system. The other way around is often not the case!
Analog QAM systems are not that horribly common these days, although they're definitely around -- Motorola's old AM stereo system (C-QUAM) could be considered one: They used amplitude to represent L+R to remain compatiable with traditional AM stereos (the "C" in "C-QUAM" is "compatible") whereas they used phase change to represent L-R to allow extraction of the separate L and R channels for AM stereo receivers.
So it seems a binary signal doesn't have to be strictly digital or analog.
Can analog signals interfere with digital reception?
Yes. 'Quantized' is the term I was looking for. Thanks.
If I bought a digital PM-receiver and tuned it to station 2 GHz, what would I most likely hear? Heterodynes?
As an individual who was once taught to believe that digital wireless reception is completely immune to EMI/RFI, I like to be proven wrong in this sense.
I do, however, guess that if analog phase-modulation signal has certain components to it, a digital PM signal might 'misconstrue' it as a digital signal. Just like FM is not completely immune to EMI/RFI -- if an interfering signal has frequency-modulated components that are strong enough, it will register on an FM receiver. Just like that, an analog signal which adequately resembles a digital signal will be considered a digital signal by a digital receiver.
Damn it you are right, worse i knew better, but did not remember TAPR high speed mixed mode radios. They are FHSS / QAM. There was an alternative that is DSSS / QAM.
The terminology starts getting messy at some point. :-) Hence I refer to such systems as "hybrids" -- it 's the sort of system that often isn't an "obvious" application to either hard-core analog guys nor hard-core digital guys... Similar, I suppose, to switched capacitor filters: They're analog in value (not quantized) but discrete in time.
I think whoever first thought up switched cap filters was rather creative -- I doubt I'm clever enough to have done so myself. (People like to point out that Maxwell kind of/sort of mentions using a switched capacitor as a variable resistor of sorts, but personally I don't see enough there to take switched cap development away from the guys at Bell Labs. Still, Maxwell was incredibly creative too... you know those guys back then spent a lot of time trying to model electromagnetic fields with various mechanical analogies, like infinite arrays of meshed gears and the like? Many suggest that it was Maxwell tossing out the mechanical analogies and trying to come up with straight mathematical models that let him so seamleslly combine field theory into his four famous equations.)
Yes.
Absolutely.
Positively.
Happens all the time!
Intereference has more to do with the bandwidth and power of the signal you're attempting to receive vs. that of the interferer than modulation methods: Many of the "digital modulation format du jour" are rather wideband (FHSS, DSSS, OFDM, etc.) and hence are largely resistant to narrow band interferers such as traditional AM and FM transmissions. Additionally, most digital modulation methods that are carrying voice or audio add plenty of error correction to the protocol to "cover" for interference or just fading that destroys some bits; with analog you hear clicks/pops/hiss/whatever and your brain provides the "error correction." Still, if you have enough power, you can easily jam up another receiver simply by forcing it to crank down its AGC such that it'll never hear the intended signal (this is known as "desensing") -- and wideband receivers are more susceptible to this than narrowband ones are, since interferers are simply more likely to show up in the wideband receiver's passband in the first place.
Depending on the bit rate of the transmitter, it'd sound either something more or less like FM radio with a bunch of tones jumping about (since frequency is just the integral of phase and all), or just white noise once the bit rate is well above audio frequencies.
Bwahahaha... who taught you that? :-)
Did someone tell you that you'll be able to directly hook an antenna up to an ADC any time soon too? :-)
Yes, if it's strong enough, it'll certainly cause bit errors.
Interesting that wideband-receivers could be more vulnerable to any type of interference than narrowband ones.
It would be more enjoyable [at least for me] if they are tones.
Stupid commercial tech magazines.
I just love when that happen. A digital PM receiver mistaking an analog signal as a digital one.
Imagine receiving the wrong text because random purely-analog PM signals with sufficient "digital-resembling" components interefere with the purely-digital PM reception:
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