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Questions tagged [superheterodyne]

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8
votes
6answers
1k views

Why is superheterodyning better than direct conversion?

What is the advantage of having the extra stage of IF, extra local oscillator and extra filtering stage and amplification. It just seems like more work and circuitry. Surely the direct conversion to ...
0
votes
1answer
380 views

Bandwidth-Noise-SNR relationship

Let’s say we have the noise figure F of a system of devices. We also have the bandwidth improvement coefficient ( as defined by my teacher ) $$BI=10log(\frac{B_{in}}{B_{out}})$$ where B1 is the ...
1
vote
1answer
75 views

In heterodyn receiver circuits, why is the LO not chosen to match the target frequency?

I'm trying to design a device that detects motion using sonar. I'm basing it on a common superheterodyne receiver like this: Now from what I've read, in radio audio receivers the local oscillator is ...
0
votes
1answer
255 views

direct conversion SSB (vs DSB-SC)

While I understand the problems trying to demodulate a DSB-SC signal using a direct conversion scheme, mostly the phasing issues arising from the fact that the sidebands are symettric and in ...
3
votes
3answers
823 views

Intermediate frequency

I'm a newbie to communication systems and circuitry. I was going through superhet receivers while trying to undertand AM/FM/DAB receiver architecture. For FM, IF is fixed to 10.7 MHz and AM 455 KHz. ...
-2
votes
1answer
169 views

Spectrum analyser [closed]

Why do we use ramp generator (sawtooth generator) with local oscillator in a spectrum analyser? I have searched in Google and I didn't find any answer that made me understand the concept. Thanks !
0
votes
0answers
58 views

Superheterodyne and intermodulation products: understanding f_RF-f_LO Graph

While studying superheterodyne-based spectrum analyzers I ran into the concept of intermodulation products explained through a \$f_{RF}-f_{LO}\$ graph. If it's not clear enough, the dashed lines are ...