A system for measuring a material, the system comprising: at least one transmitter configured to transmit (904, 920, 1204) at least a first signal and a second signal over a signal path, wherein the transmitted signals are radio frequency signals; at least one variable reflector (106, 1600, 1604, 1700, 2000) configured to reflect (908, 924, 1208) a portion of the first signal to produce a first reflected signal, the portion of the first signal having traveled through the material, and configured to reflect a portion of the second signal to produce a second reflected signal, the portion of the second signal having traveled over the signal path through the material; at least one receiver configured to receive (912, 928, 1212) at least a first received signal (130, 1016) and at least a second received signal, the first received signal comprising the first reflected signal having traveled through the material and the second received signal comprising the second reflected signal having traveled through the material; and a processor in communication with the at least one receiver; wherein the at least one variable reflector (106, 1600, 1604, 1700, 2000) is configured to reflect the portion of the first signal with a reflecting property having a first reflecting property value, the portion of the first signal having traveled over the signal path, wherein the first reflected signal travels over a reflected signal path (A'); the at least one variable reflector (106, 1600, 1604, 1700, 2000) is configured to reflect the portion of the second signal with the reflecting property having a second reflecting property value that is different from the first reflecting property value, the portion of the second signal having traveled over the signal path, wherein the second reflected signal travels over the reflected signal path (A'); the at least one variable reflector (106, 1600, 1604, 1700, 2000) is adjustable to change the value of the reflecting property by one of adjusting a reflectivity amplitude of the at least one variable reflector and adjusting an effective impedance of the at least one variable reflector, wherein the reflectivity amplitude is independent of an incident excitation vector direction; and the processor is configured to isolate (1004, 1224) a representation of the first reflected signal and the second reflected signal by calculating a difference between the first received signal and the second received signal and to determine a property of the material based on the isolated representation of the first and second reflected signals. at least one transmitter configured to transmit (904, 920, 1204) at least a first signal and a second signal over a signal path, wherein the transmitted signals are radio frequency signals; at least one variable reflector (106, 1600, 1604, 1700, 2000) configured to reflect (908, 924, 1208) a portion of the first signal to produce a first reflected signal, the portion of the first signal having traveled through the material, and configured to reflect a portion of the second signal to produce a second reflected signal, the portion of the second signal having traveled over the signal path through the material; at least one receiver configured to receive (912, 928, 1212) at least a first received signal (130, 1016) and at least a second received signal, the first received signal comprising the first reflected signal having traveled through the material and the second received signal comprising the second reflected signal having traveled through the material; and a processor in communication with the at least one receiver; wherein the at least one variable reflector (106, 1600, 1604, 1700, 2000) is configured to reflect the portion of the first signal with a reflecting property having a first reflecting property value, the portion of the first signal having traveled over the signal path, wherein the first reflected signal travels over a reflected signal path (A'); the at least one variable reflector (106, 1600, 1604, 1700, 2000) is configured to reflect the portion of the second signal with the reflecting property having a second reflecting property value that is different from the first reflecting property value, the portion of the second signal having traveled over the signal path, wherein the second reflected signal travels over the reflected signal path (A'); the at least one variable reflector (106, 1600, 1604, 1700, 2000) is adjustable to change the value of the reflecting property by one of adjusting a reflectivity amplitude of the at least one variable reflector and adjusting an effective impedance of the at least one variable reflector, wherein the reflectivity amplitude is independent of an incident excitation vector direction; and the processor is configured to isolate (1004, 1224) a representation of the first reflected signal and the second reflected signal by calculating a difference between the first received signal and the second received signal and to determine a property of the material based on the isolated representation of the first and second reflected signals.