Edit in JSFiddle

var popup1 = new wijmo.input.Popup('#Popup1', {
    modal: true,
    hideTrigger: wijmo.input.PopupTrigger.None
});

var popup2 = new wijmo.input.Popup('#Popup2', {
    modal: true,
    hideTrigger: wijmo.input.PopupTrigger.None
});

function btn_click1(e, args) {
    popup1.show();
}

function btn_click2(e, args) {
    popup2.show();
}

<div id="Popup1" style="width:300px; height:150px">
    Popup1<br/>
    <button onclick="btn_click2()">Show Popup2</button>
</div>
<div id="Popup2" style="width:150px; height:70px">       
     Popup2<br />
</div>
<button onclick="btn_click1()">Show Popup1</button>