Digital board for spectrum analyzer

Description

This is digital part of an experimental RF receiver. It works with:
https://hackaday.io/project/182646-microwave-frequency-converter-0-3ghz-to-200mhz
https://hackaday.io/project/168985-microwave-synthesizer-4-7ghz
https://hackaday.io/project/187783-if-converter-228mhz-to-3mhz-and-lo-generator

This board includes:
- ADC with input amplifier
- some power supplies
- simple graphics controller for LCD implemented in FPGA
- signal processing implemented in FPGA: conversion to baseband, filtering, downsampling, RMS calculations
- microcontroller which controls the whole system, does calculations on the results from FPGA, controls keyboard and display.

Design documentation is attached (see "Files")

Files

Digital_design_pack.zip

design files and description of digital part of spectrum analyzer

Zip Archive - 7.79 MB - 11/27/2022 at 19:27

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Discussions

L4wudu wrote 08/09/2023 at 23:41

Are you using only FIR filters before each decimate by 10 stage? How many taps?

Are you sure? yes | no

michal777 wrote 08/28/2023 at 09:30

First the signal is multiplied by 3MHz sin and cos digitally, then FIR filtering with simultaneous dropping samples for decimation (both I and Q signals). After one or more filtering/decimation stages, RMS is calculated from remaining samples - that's all. About 120 taps (probably the filter is currently too good for the hardware so it's just some initial value to be tuned later).

Are you sure? yes | no

Digital board for spectrum analyzer

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Description

Files

Digital_design_pack.zip

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