To implement the AM transmitter signal, do the following steps:

a$.$ First you need to create your MATLAB function block to generate the envelope $(1+\frac{m(n{T}_x)}{m_p})$ from the incoming message. To provide the $m_p$ to the input of MATLAB function, use Array Max and Min block to get the max$(m_p)$ value of the message signal.

b$.$ This Array Max and Min block is an array in$/$out$,$ so connect it to the message properly to get only the value $($recall that you need to use Waveform properties block to get value from y terminal$)$ of the message.

c$.$ The envelope value $(1+\frac{m(n{T}_x)}{m_p})$ also cannot exceed $+-1$ for the USRP to operate properly. Thus you need to normalize it by dividing by its max value $[$MATLAB code: abs$($evelope$\_$value$))].$

d$.$ Create two outputs of MATLAB as $g_l$ and $g_Q$ where $g_l$ is the normalized envelope and $g_Q$ is equal to $0.$ However, note here that $g_Q$ has to be an array, not a constant. So you may use a MATLAB code : $g_Q=m^{**}0$ to do this.

e$.$ Connect the baseband $($MATLAB output$)$ signal to the niUSRP Write Tx Data block through Real and Imaginary to Complex block.

f$.$ Complete all other missing connections.

g$.$ Connect appropriate graphs for the time domain, and the frequency domain observations of the AM message $($envelope$).$