I have a few noble ancestors. Sometimes if someone didn't have any sons, a title could get passed down through a daughter.
for instance, I have an ancestor, Clement de Reihlac. He was actually born Clement le Fevre His mother was Marguerite de Reihlac. When her brother died and there were no more male heirs to the de Reihlac name, Clement le Fevre took on the name de Reihlac and the noble house.
I think it is also possible that the surname is just Chambaron. I have a few noble ancestors whose real surname was what came before the last "De -----". For instance, my ancestor Nicolas de Mesme de Marolles was from the family "de Mesme" but after he acquired the lands of Marolles he tacked on the name de Marolles.
"D" with an apostrophe after it usually comes before a vowel and is the same thing as "De" before a consonant. It means "of". So when your ancestor signed Chambaron chevalier d'Antignac it was the same thing as saying Chambaron, Knight of Antignac. Antignac is a surname in France but it is also a place which is why I think the surname might be just Chambaron.
This might also help:
http://en.wikipedia.org/wiki/Nobiliary_particle#FranceNote this paragraph:
"From the sixteenth century, surnames among the French nobility have often been composed of a combination of patronymic names, titles, or noms de terres ("names of lands" or estates) joined by the preposition de..."
The Chambaron would be a surname and the "d'Antignac" would be the nom de terres.
I hope this helps