\documentclass[convert, tikz,transparent]{standalone}
\usepackage[spanish]{babel}
\usepackage[utf8]{inputenc}
% Bibliotecas
\usepgflibrary{arrows.meta} % Uso de bibloteca de flechas
\usetikzlibrary{shapes} % Biblioteca de formas
% Definición de bloques
\tikzstyle{mix} = [draw, very thick, circle, minimum size=1cm] % Demodulador y señal de portadora
\tikzstyle{block1} = [draw, very thick, rectangle, minimum height=1.5cm, minimum width=3cm] % Filtro pasobajo
\tikzstyle{block2} = [draw, very thick, rectangle, minimum height=1cm, minimum width=1cm] % Circuito de Retardo
\tikzstyle{block3} = [draw, very thick, rectangle, minimum height=3cm, minimum width=3cm] % Generador de fases
% Definición de estilos
\tikzstyle{ann} = [font=\large \bf ,inner sep=1pt, align=center] % Estilo de nodo
% Definición de variables
\newcommand{\mixer}{\Huge $\times$} % La "X" de los demoduladores
\newcommand{\pim}{\Large $\frac{\pi}{2}$} % Retardo de la línea
\newcommand{\deriv}{\Large $\frac{d}{dt}$} % Bloque derivador
\begin{document}
\begin{tikzpicture}[auto, very thick, -Stealth] % Se define la linea muy gruesa y la unión de líneas con flechas con el estilo "Stealth".
% Diagrama de un Demodulador GSMK
	\node[ann] at (0,0){Señal \\GMSK};
	\node[ann,mix] at (5.5,3)(mix1){\mixer};
	\node[ann,mix] at (5.5,-3)(mix2){\mixer};
	\node[ann,block1] at (9,3)(fpb1){Filtro\\pasabajo};
	\node[ann,block1] at (9,-3)(fpb2){Filtro\\pasabajo};
	\node[ann,block2] at (5.5,-1)(del1){\pim}; % Desfasador de la portadora
	\node[ann,block3] at (13,0)(fase){Generador\\de fases};
	\node[ann,block2] at (17,0)(der1){\deriv}; % Derivador
	\node[ann,mix] at (8,0.5)(port){$f_C$}; % Generador de portadora
	\draw (1,0) --++(2,0) |- (mix1.west);
	\draw (1,0) --++(2,0) |- (mix2.west);
	\draw (port) -| (mix1.south);
	\draw (port) -| (del1.north);
	\draw (del1.south)-|(mix2.north);
	\draw (mix1.east)--(fpb1.west);
	\draw (mix2.east)--(fpb2.west);
	\draw (fpb1.east)-|(fase.north);
	\draw (fpb2.east)-|(fase.south);
	\draw (fase.east)--(der1.west);
	\draw (der1.east)--++(1,0); 
	\node[ann] at(20,0) {Señal\\de datos}
;
\end{tikzpicture}
\end{document}