mjhjmtu

I need to plot a rectangular waveform with Latex. The main problem is how to make the height of the pulse "variable" not a "number" as you can see in the figure below. "x" here is some variable that will be found by calculations.

A PSTricks solution just for comparison purpose.

documentclass[pstricks,border=12pt,12pt]standalone
usepackagepst-plot
begindocument
beginpspicture(-1,-1)(11.5,5.5)
 psaxes[ticks=x,labels=x]->(0,0)(-1,-1)(11,5)[$t$,0][$A(t)$,90]
 multips(0,0)(2,0)5psline[linecolor=blue,linewidth=2pt](0,0)(0,4)(1,4)(1,0)(2,0)
 uput5pt[180](0,4)$sqrtR_s$
endpspicture
enddocument

Since this question is tagged tikz-pgf, I thought you may also be interested in a TikZ code. (One of its advantageous is that this works with pretty much any compiler.)

documentclass[tikz,border=3.14mm]standalone
begindocument
begintikzpicture
pgfmathsetmacroh2
pgfmathsetmacroL4
draw[thick,-latex] (0,-0.5) -- (0,h+2) node[above] $A(t)$;
draw[thick,-latex] (-0.5,0) -- (2*L+1,0) node[right] $t$;
foreach X [evaluate=X as Z using int(2*X-1),] in 1,...,L
draw[very thick,blue] (2*X-2,0) 
endtikzpicture
enddocument

A simple approach using TikZ.

documentclass[border=3.14mm]standalone
usepackagetikz
begindocument
 begintikzpicture
 defx1 % replace 1 with desired value here
 draw[-latex] (0,0) -- ++(4,0) node[right]$t$;
 draw[-latex] (0,0) -- ++(0,2.0x)node[left]$A(t)$;
 draw[thick] (0,x)node[left]$sqrtx$ -- ++(1,0) -- ++(0,-x)node[below]1 -- ++(1,0) -- ++(0,x) -- ++(1,0) -- ++(0,-x)node[below]3 -- ++(0.5,0);
 endtikzpicture
enddocument