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8

They have a much faster ADCs. Also, ADSL2+ has its downlink up to maybe 2.2 MHz, so you'd need at least 4.4 MS/s to do that. In reality, single-digit MHz ADCs are "old tech" and relatively cheap. Together with it being desirable to oversample the signal to apply digital filtering to increase your SNR, I'd presume that modern (as in: of the last 20 ...


7

To answer your two questions: ADSL modems were usually >2Msps, often a multiple of 1.1Msps to simplify the signal processing later. E.g. the MTC20174 ADSL analog frontend had a 8.8Msps ADC/DAC. The reason for the higher than necessary sampling rate was the use the higher sampling rate to get more effective bits at signal frequency. This is a quite common ...


4

First note that the Carlson formula is only an approximation. Second, narrowband FM is defined as FM modulation for which the modulation index is small compared to one. When this is the case, the Carlson formula reduces to the simpler formula and the spectrum of a narrowband FM signal is just the carrier and two sidebands spaced by the modulation frequency. ...


4

I assume that your quantity beta is the maximum momentary frequency offset per the maximum baseband signal frequency fm. That beta is called "modulation index" and it exists in the approximated formula of the needed transmission bandwidth which is the uppermost of your bandwidth formula options. In narrow band FM the modulation index is much ...


3

I recall taking a look at the spectrum of SHDSL modems once, those were capable of 15 Mbps over a single twisted pair. The spectrum had a steep roll-off above say 1.5 MHz if memory serves. So that's roughly 3 MBaud... times 5 bits per symbol? The modulation was called TC-PAM I guess... note that modern VDSL systems use very different modulation schemes, ...


2

This has got off to a bad start, but the answers are really almost there: WiFi and Ethernet are closely related through both the technology and the IEEE standards body that defines them. The absolute simplest wifi-wire-to-wifi would be unscrewing both antennas on the APs and putting a length of coaxial cable between them. For short links this would probably ...


1

From your 2nd picture it looks like you need a linear-phase FIR, as opposed to an IIR. The main difference is that FIRs can have perfectly linear phase, thus a perfectly flat group delay, which means all the frequencies are delayed by the same amount, while IIRs have non-linear phase by design, thus a nonlinear group delay, resulting in smearing in time ...


1

No, not necessarily. The receiver might just compare if input A voltage is above or below input B voltage. So the absolute voltages are not that important, the difference is. If you have 0V at the receiver inverting pin, and the receiver has a threshold of say 200mV, then the non-inverting pin being below 200mV is 0 and above 200mV is 1.


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