# Tag Info

Accepted

### Understanding the relationship between LoRa chips, chirps, symbols and bits

LoRa is a chirp-based spread-spectrum modulation. A symbol is a chirp. To generate symbols/chirps, the modem modulates the phase of an oscillator. The number of times per second that the modem ...
• 809
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### FSK demodulation using DSP

A very simple but elegant approach to demodulate FSK is a delay and multiply. (Followed by a simple low pass filter). This is a non-coherent FM detector using the principal that the output of a ...
• 498
Accepted

### Question about AM demodulation concept

The main body of this answer was made before the OP added an edit section to his question - that edit section is inapplicable because the type of modulation (although AM) is full double sideband ...
• 465k

### Half wave rectifier query

You should analyze it in two conditions, due to the diode non-linearity. Using the same value for both resistors, since the current though them is the same (ideal op. amp.) so is the voltage across ...
• 8,567
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### Analog television: What is the difference between the first IF and second (demodulated) IF?

It's helpful to include a link to the datasheet even if, as you note, it doesn't explain the circuit operation. Why is the video carrier frequency 38.9 MHz but the audio 33.4 MHz? On-air the audio ...
• 4,423

### Understanding the relationship between LoRa chips, chirps, symbols and bits

Definitions So, what is a bit, symbol, chip, and chirp, and what do these mean? Bit Bit is the smallest unit of information. Most of the time, we try to send these bits from the sender (TX) to the ...
• 854

### Why, where and how we use envelope detector in AM demodulation?

I don't understand how you could have studied AM demodulation and not understand the purpose of an envelope detector. Something is lacking in your studies. In any case, in AM (the M stands for ...
• 16.1k

### Techniques for digitally copying video laserdiscs

So, approaching this from a "top view": A LaserDisc records analog signal. The recording process is basically: Make a composite video signal (basically, PAL or NTSC "baseband") FM-Modulate the 4-6 ...
• 97.5k
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### Hearing the radio by touching a jack plug

Here is a circuit having four "components" that can act as a radio receiver. When each component is optimized, reception can be too loud to bear: simulate this circuit – Schematic ...
• 26.8k

### Envelope/Peak Detector

Having read the datasheet of LM7171, I have 7 suggestions: 0) is your scope fast enough (500MHz) to look for oscillations of the OpAmp 1) operate the OpAmp from 10Volts; its not characterized at ...
• 34.6k

### RC time constant and diode detector

your derivation is partially correct. Pls checkout my images for complete derivation.

### Select Phase Detector Cutoff Frequency? Phase Locked Loop FM Demodulation

When building a phase locked loop, the purpose of the low pass filter is poorly understood. When you wrap a phase feedback loop around a VCO, the integration of frequency to phase causes a 20dB per ...
• 170k
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### Why can FM be demodulated non-coherently while PM cannot be demodulated non-coherently?

The phase of a signal is only defined with respect to a reference. If the reference cannot be communicated, then the phase is meaningless. Often when phase modulation is used, it's treated as ...
• 170k

### Half wave rectifier query

Seeing the forest behind the trees After these comprehensive but specific answers, I will try to summarize what has been done and why it has been done in this way (ie, I will try to guess what were ...
• 17.8k
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### Cost-efficient mixers and/or demodulators for low frequencies

Antonio's suggestion of four switches to make a mixer is an ideal one for low-frequencies like 200 kHz. A local oscillator at 4X frequency (800 kHz) allows I & Q output: simulate this circuit &...
• 26.8k
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### AM Demodulation of Square wave

R8 (1 Mohm) and C4 (15 pF) have a time constant that is too long for decent 10 kHz demodulation. Try lowering R3 to 1 kohm. You will get more carrier ripple coming through but the square wave shape ...
• 465k

### FSK demodulation using DSP

There's a lot of approaches for decoding FSK. Zero-crossing detection will be pretty sensitive to noise. At these low rates, you don't have to worry. Every milkcan these days has enough compute power ...
• 97.5k
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### What kind of component was used in this demodulation circuit?

They are commonly known as IF (intermediate frequency) Transformers. They can have various winding arrangements (tapped/untapped, single/transformer) - the 5 pin base is common, and are used for ...
• 5,433
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### In this Foster Seeley discriminator, what is the purpose of capacitor C3?

C3 provides the reference signal from the primary of the transformer to be combined with the signal from the secondary of the transformer that resonates at the centre frequency of operation. The two ...
• 33.8k
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### Can someone explain how this Ratio detector circuit works?

The diagram in your question comes from a NEETS (US Navy Electricity & Electronics Training Series) module, to be more specific it comes from module nÂș12 . The documentation for these modules ...
• 5,801
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### Why is transformer coupling used in a simple slope detector? Can't the FM signal be applied directly in parallel to a tuned circuit?

Why is transformer coupling used in a simple slope detector? You don't need a transformer for a simple slope detector. This circuit would work providing you select the centre frequency to be one side ...
• 465k

### Half wave rectifier query

I'm having issues with the first amplifier. Although it seems very simple (just an inverter), can't see clearly how the first diode rectifies the negative part of the SIG signal. It's an inverting ...
• 465k

### Half wave rectifier query

This is called a precision rectifier. Imagine the SIG going negative by 1V, the opamp wants to make the voltage at the inverting input the same as at the non-inverting input, which is 0V, so it needs ...
• 25.6k

### Cost-efficient mixers and/or demodulators for low frequencies

If your signal is not differential ... use this. And with a DC offset in signal ... And if it is "differential" ... And with a signal and a DC offset ...
• 14.7k

### What is the relation between a signal and its generated audio?

No, the signals are different: the AM signal (AM=amplitude modulation) has a fixed frequency, and its amplitude is modulated by the sound signal, which has a much lower frequency. If you connect every ...
Accepted

### Why do we need a diode in an AM demodulation circuit?

If we only apply a low-pass filter to it, we will get an AC signal that can be passed to a speaker directly, right? No, not at all. The low-pass filter would just block the RF signal (your modulated ...
• 97.5k
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### Front-End Selection for digital FM Demodulator

Having thought through the direct downconversion issues, the primary challenge is the dynamic range needed to accept massive energy alongside the weak FM signals. simulate this circuit – ...
• 34.6k

### AM Demodulation of Square wave

The signal modulating the carrier is a $f_0=10\ kHz$ square wave. Note that it has a quite high bandwidth: theoretically infinite, practically it's $BW\approx10\ f_0$. A 100 kHz bandwidth on a ...
• 5,801