Modified approach for high frequency dielectric characterization of thinly metallized soft polymer film using grounded coplanar waveguide

Abstract

International audienceIn this paper, we introduce the dielectric characterization of soft polymer, polyurethane (PU), between 1 and 31 GHz frequency band using Grounded CoPlanar Waveguide (GCPW) lines with a modified analytical method. The unavoidable thin metallization (1 μm) of GCPW lines on polyurethane yields high conductor losses, which contribute to the extracted global losses up to 58% at 4 GHz. In order to get more precisely the dielectric losses, a modification of an already existing analytical model by coupling it with 3D electromagnetic simulations is proposed, which allows to estimate and subtract quickly the conductor losses. The measurements indicated that polyurethane relative permittivity ranges from 3.49 to 2.65 and the loss tangent was about 0.08, which is in agreement with the state of the art on this grade of PU as well as the Metal-Insulator-Metal capacitors characterizations (from 10−1 to 107 Hz and from 2 × 108 to 5 × 109 Hz). The proposed approach may open a fast and simple way for precisely determining the microwave dielectric properties of (ultra) soft polymers in a large bandwidth

New low loss soft thermoplastic blends for microwave applications

“…So forth, establishing the correct method is crucial to obtain accurate values of the dielectric parameters of the sample. Thereupon, different methods have been thoroughly studied [10,19,20] and the microstrip ring resonator method has been selected for our measurements. This method has been exploited for different configurations such as liquid crystal polymers [20][21][22][23].…”

“…It may be noted that the conductivity of the metallic radi ating patch must be as high as possible and the thickness of the deposited layer must be at least equivalent to one skin depth at the operating frequency, otherwise metal losses prevent from good radiation. For instance, for a 10 GHz operating patch antenna with a copper patch, the skin depth-minimum metal thickness for antenna radiation-is equal to 0.92 µm [10]. Besides, the generally weak adhesion between polymers and metals due to their chemical incompatibility is often a crucial issue for microwave applications.…”

“…For each polymer blend, dielectric measurements were made on three to four samples and repeated three times, from which the mean value of the dielectric parameters was calculated. Figure 7 shows the frequency dependence of the relative permittivity in low frequency range [1][2][3][4][5][6][7][8][9][10] kHz. The relative permittivity exhibits a quasistable value around 2.82 for the rPP blend and 2.65 for the LDPE based blend which are typical values of a nonpolar polymer such as rPP and LDPE containing blends [31].…”

“…Thereby, printed antennas and more specifically, microstrip antennas play a paramount role in the wireless communication since they ensure the signal noise reduction of the communica tion. The modern communication systems and technologies at the X band (8)(9)(10)(11)(12) are supported by different types of antennas such as compact antennas and more precisely planar patch antenna that are widely used owing to their large signal to noise ratio, low profile and low cost [1].…”

“…Microwave antennas are concrete examples whose properties of the substrate determine the quality of the radiation of the antenna. From that perspective, developing a performing soft substrate for antenna is still challenging due to the quite high dielectric loss factor (tan δ > 0.01) [10] of some previously studied soft polymers at 1 GHz. We aim to develop a patch antenna based on soft dielectric at X band, which is of interest in many military and medical applications.…”