0

Similarly to the following question:

How to draw this simple box diagram with Tikz

I want to draw a feedback loop, but to other box. it looks like: enter image description here

2

A starting point could be with

\documentclass[tikz,14pt,border=10pt]{standalone}
\usepackage{textcomp}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\begin{document}
    % Definition of blocks:
    \tikzset{%
        block/.style    = {draw, thick, rectangle, minimum height = 3em,
            minimum width = 8em, fill=white, text width=2.5cm},
        sum/.style      = {draw, circle, node distance = 2cm}, % Adder
        input/.style    = {coordinate}, % Input
        output/.style   = {coordinate}, % Output
        virtual/.style = {coordinate},
    }
    % Defining string as labels of certain blocks.
    \newcommand{\suma}{\Large$+$}

    \begin{tikzpicture}[auto, thick, node distance=2cm, >=triangle 45]
    \draw
    % Drawing the blocks of first filter :
    node at (0,0){}
    node [input, name=input1] {} 
    node [block, right = 1cm of input1] (inte2) {LDPC Encoder}
        node [block, right = 1cm of inte2] (inte3) {BPSK modulator}
            node [block, right = 1cm of inte3] (inte4) {Intersymbol intereference (ISI)}
    node [sum, right = 1cm of inte4] (suma1) {\suma}
    node [input, name=input2, above = 1cm of suma1] {} 
    node [output, name=output1, right = 1cm of suma1] {};
    \node [block, right = 1cm of output1] (model) {Model};
    \node [block, right = 1.5cm of model] (model1) {Model1};
    \node [virtual, left=of model.165] (input)     {};
    \node [virtual, right=of model1.0] (output)    {};
    \node [virtual, below left=of model.west] (feedback)  {};
    % Joining blocks. 
    % Commands \draw with options like [->] must be written individually
    \draw[->](input1) -- node {$m$}(inte2);
    \draw[->](inte2) -- node {$c$}(inte3);
        \draw[->](inte3) -- node {$x$}(inte4);
            \draw[->](inte4) -- node {$x+h$}(suma1);
    \draw[->](input2) -- node {$w(t)$} (suma1);
    \draw [->] (suma1.30) -- node {$y$} (model.171);
    \draw[->](model) -- node {$q_\Phi(x|y)$} (model1);
    \draw [->] (model1) -- node [name=y] {$p(x)$}(output);
    \draw [->,rounded corners] (model1) -- (y.south) |- (feedback) |- (model.195);
    \end{tikzpicture}
\end{document}

which will give you:

enter image description here

You can of course, play with the block definition of each individual(ly defined) blocks to center the multiline texts using minimum width and text width respectively which, I leave it as an exercise for you to play :).

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