In recent times, the advancement in telecommunication technology and avionics has brought many new challenges for the design of mobile devices, warfare equipment, especially in radomes and antennas applications. the functionality of a radome is to provide a protective layer between designed antenna and the surrounding with negligible impact to the electrical performance of the antenna. therefore, a material having the capability of minimal power loss during electromagnetic wave transmission through the material is considered as an ideal radome material. however, no such material exists which can reasonably fulfill the electrical requirements altogether with the mechanical and physical requirements. therefore, the selection of a radome material is a compromise between the dielectric constant and loss tangent of the material along with the material density, temperature, humidity absorption, and frequency. nowadays, various frequency bands are being utilized in aerospace, electronics, communications and commercial applications, and so the multi-band antennas are being employed. many multi-band antennas for gsm, umts, and wi-fi applications have been reported in the literature, and now the lte standard is another recent addition to these existing frequency bands. all these new frequency bands have also to be covered in near future and accordingly various rf devices including the radome structures have to be designed for these bands. however, a limited number of study has been carried out till now in the case of multi-band performance of radomes. this may be due to the expensive and rigorous microwave testing techniques to characterize the material under test. due to the requirement of high accuracy in selection of low lossy material, the microwave characterization of radomes using resonant method is preferable over non-resonant methods. although the conventional waveguide resonator techniques provide better accuracy in the loss tangent calculation; the cost, weight, and size of the corresponding cavity become quite large especially in the lower frequency bands. as the global system for mobile communications (gsm) bands for 3g and 4g applications employs low frequency, the conventional cavity sensor gets quite bulky and expensive thus making it inconvenient for microwave testing of samples. in this innovation, a novel and highly compact tri-band epsilon-near-zero (enz) substrate integrated waveguide (siw) based microwave sensor has been proposed for material testing at the global system for mobile communications (gsm) bands. the prototype rf sensor is designed, simulated, and tested in-house for the microwave characterization of materials under test in 3g and 4g frequency bands. the attractive proposed design provides a substantial reduction in the sensor size and simultaneously facilitates a convenient sample placement design for microwave measurement of the sample under test at various frequencies of 3g and 4g bands. the detection of dielectric signature of the material under test at multiple frequencies with reasonable sensitivity as compared to the conventional siw based sensors has been reported. the device is fabricated using multilayer fr4 substrate where a three layered enz tunnel is machined for the testing. the attractive feature of the proposed sensor is its capability of multiple frequency measurements using the same mode of operation i.e., the te100 mode. thus, the evanescent wave propagation constant becomes same for all the measurement frequency which is otherwise not available elsewhere. the proposed tri-band microwave sensor is designed to work at 1.7 ghz, 2.1 ghz and 2.5 ghz of gsm bands which have been recently adopted to be used for 3g and 4g mobile applications. the structure has been developed using in-house milling, cutting, and standard electroplating techniques. the rf signal is being coupled to the prototype using the subminiature version a (sma) connectors which are then collected at other end using the network analyzer. the measured data is then processed with the standard algorithm for getting the dielectric signature of various reference samples. the measured data are found to be in good agreement with their reference values thus validating the design methodology, proposed technique and, the developed prototype. this prototype can be useful for telecommunication, military and, aerospace industry.