Entering subcaptions for figures without using subcaption environment

Question

I'd like to realize this picture in LaTeX to show radiation of the dipole. I've already ask this question Radiation diagram. But, I need to have the caption for each diagram WITHOUT using \subcaption! (because in my code I need to use \subfigure for something else and we can't use at the same time \subcaption and \subfigure,...)

My code is the following (taken from marmot's answer) to the linked question:

    \documentclass[11pt,a4paper]{article}
    \usepackage{subcaption}
    \usepackage{floatrow}
    \usepackage{pgfplots}
    \pgfplotsset{width=8cm,compat=1.16}
    \usepgfplotslibrary{polar}
\begin{document}
    \begin{figure}[htb]
    \floatsetup{valign=c, heightadjust=all}
    \ffigbox{%
    \begin{subfloatrow}
    \ffigbox{\begin{tikzpicture}
    \begin{axis}[view/h=45,axis lines = none,unit vector ratio=1 1 1]
            \addplot3[domain=0:360,domain y=0:360,samples=31,
            point meta=sqrt(x^2+y^2),
            colormap/blackwhite,surf,%mesh,point meta=1, %<-if you want a mesh
        z buffer=sort]
           ({(sin(x+90)*sin(x+90))*cos(y)}, 
            {(sin(x+90)*sin(x+90))*sin(y)}, 
            {(sin(x+90)*sin(x+90))*sin(x)});
    \end{axis}
    \path(current bounding box.south west) rectangle (current bounding box.north
    east);
    \end{tikzpicture}}{\caption{Diagramme de rayonnement du dipôle.\label{fig:Diagramme de rayonnement du dipôle}}}
    \ffigbox{\begin{tikzpicture}
    \begin{polaraxis}[axis lines = none]
        \addplot[domain=0:360,samples=73,smooth] (x+90,{sin(x)*sin(x)});
    \end{polaraxis}
    \draw[-stealth] ([yshift=2cm]current axis.south) -- ([yshift=-2cm]current axis.north);
    \end{tikzpicture}}{\caption{Coupe verticale du diagramme de rayonnement.\label{fig:Coupe verticale du diagramme de rayonnement}}}
    \end{subfloatrow}}
    {\caption{Rayonnement du dipôle demi-onde.}\label{fig:Rayonnement du dipôle demi-onde}}
    \end{figure}
\end{document}

Answer 1

mwe for above image is:

\documentclass{article}
\usepackage[export]{adjustbox}
\usepackage{tabularx}

\begin{document}

\begin{figure}[htb]
\begin{tabularx}{\linewidth}{*{2}{>{\centering\arraybackslash}X}}
\includegraphics[width=\linewidth]{example-image-duck}
\caption{3D presentation of dipole radiation}
\label{fig:dipol-1}
    &
\includegraphics[width=\linewidth, height=3cm]{example-image-duck}
\caption{3D presentation of dipole radiation}
\label{fig:dipol-2}
\end{tabularx}
\end{figure}

or

\begin{figure}[htb]
\begin{tabularx}{\linewidth}{*{2}{>{\centering\arraybackslash}X}}
\includegraphics[width=\linewidth,valign=c]{example-image-duck}
    &
\includegraphics[width=\linewidth, height=3cm,valign=c]{example-image-duck}\\
%
\caption{3D presentation of dipole radiation}
\label{fig:dipol-1}
    &
\caption{3D presentation of dipole radiation}
\label{fig:dipol-2}
\end{tabularx}
\end{figure}

\end{document}

in case that you like to include code of images, than with them replace \includegraphics ... and for their vertical align use option baseline ... for the tikzpicture. Since you not provide mwe, i can't show anything further.

addendum:

Following the edit to the question (which uses code from https://tex.stackexchange.com/a/467985), if i understood you correctly, you looking for the following:

it is generated with the following mwe:

\documentclass[11pt,a4paper]{article}
%\usepackage{floatrow}  % not used in this mwe
                        % however it is troublemaker. do you really need it?
\usepackage{caption}    % not used in this mwe
\usepackage{subcaption} % not used in this mwe
\usepackage{tabularx}   % <--- new

 \usepackage{pgfplots}
\pgfplotsset{width=8cm,compat=1.16}
\usepgfplotslibrary{polar}

\begin{document}
    \begin{figure}[htb]
\begin{tabularx}{\linewidth}{*{2}{>{\centering\arraybackslash}X}}
% left image
    \begin{tikzpicture}
\begin{axis}[view/h=45,axis lines = none,unit vector ratio=1 1 1]
        \addplot3[domain=0:360,domain y=0:360,samples=31,
        point meta=sqrt(x^2+y^2),
        colormap/blackwhite,surf,%mesh,point meta=1, %<-if you want a mesh
    z buffer=sort]
       ({(sin(x+90)*sin(x+90))*cos(y)},
        {(sin(x+90)*sin(x+90))*sin(y)},
        {(sin(x+90)*sin(x+90))*sin(x)});
\end{axis}
\path(current bounding box.south west) rectangle (current bounding box.north east);
    \end{tikzpicture}
\caption{Diagramme de rayonnement du dipole.}
\label{fig:Diagramme de rayonnement du dipole}
    &
% right image
    \begin{tikzpicture}
\begin{polaraxis}[axis lines = none]
\addplot[domain=0:360,samples=73,smooth] (x+90,{sin(x)*sin(x)});
\end{polaraxis}
\draw[-stealth] ([yshift=1.6cm]current axis.south) -- ([yshift=-1.6cm]current axis.north); % corected yshift
    \end{tikzpicture}
\caption{Coupe verticale du diagramme de rayonnement.}
\label{fig:Coupe verticale du diagramme de rayonnement}
\end{tabularx}
    \end{figure}
\end{document}

to obtain above image i comment (removed) package floatrow. Do you really need it? Apparently it somehow redefine appearance of captions in figure environments (allow only one caption) and consequently in above mwe cause errors.

Almost all, for what i see that it is used in your document, can be achieved with subcaption package:

\documentclass[11pt,a4paper]{article}
%\usepackage{floatrow}  % not used in this mwe
                        % however it is troublemaker. do you really need it?
\usepackage{subcaption} % not used in this mwe
\usepackage{tabularx}   % <--- new

 \usepackage{pgfplots}
\pgfplotsset{width=8cm,compat=1.16}
\usepgfplotslibrary{polar}

\begin{document}
    \begin{figure}[htb]
    \centering
% left image
\begin{subfigure}[b]{0.45\linewidth}
    \begin{tikzpicture}
\begin{axis}[view/h=45,axis lines = none,unit vector ratio=1 1 1]
        \addplot3[domain=0:360,domain y=0:360,samples=31,
        point meta=sqrt(x^2+y^2),
        colormap/blackwhite,surf,%mesh,point meta=1, %<-if you want a mesh
    z buffer=sort]
       ({(sin(x+90)*sin(x+90))*cos(y)},
        {(sin(x+90)*sin(x+90))*sin(y)},
        {(sin(x+90)*sin(x+90))*sin(x)});
\end{axis}
\path(current bounding box.south west) rectangle (current bounding box.north east);
    \end{tikzpicture}
\caption{Diagramme de rayonnement du dipole.}
\label{fig:Diagramme de rayonnement du dipole}
\end{subfigure}
    \hfil
% right image
\begin{subfigure}[b]{0.45\linewidth}
    \begin{tikzpicture}
\begin{polaraxis}[axis lines = none]
\addplot[domain=0:360,samples=73,smooth] (x+90,{sin(x)*sin(x)});
\end{polaraxis}
\draw[-stealth] ([yshift=1.6cm]current axis.south) -- ([yshift=-1.6cm]current axis.north);  % corected yshift
    \end{tikzpicture}
\caption{Coupe verticale du diagramme de rayonnement.}
\label{fig:Coupe verticale du diagramme de rayonnement}
\end{subfigure}
    \caption{Rayonnement du dipole demi-onde.}
    \label{fig:Rayonnement du dipole demi-onde}
    \end{figure}
\end{document}

in both case i slightly corrected second image (see both mwe)