Dielectric Characterization of Meat Using Enhanced Coupled Ring-resonator Muhammad Taha Jilani 1 , Wong Peng 2 Wen, Mohammad Azman Zakariya, Lee Yen Cheong 3 Department of Electrical & Electronics Engineering, 3 Department of Fundamental Applied Sciences University Technology PETRONAS, Malaysia 1 mtaha.jilani@gmail.com, 2 wong_pengwen@petronas.com.my Abstract—In this paper an enhanced coupled microstrip ring- resonator is presented for poultry meat quality evaluation. The proposed 1 GHz ring-resonator demonstrates significant change in resonance frequency while characterizing the meat with different moisture content. Measured and simulated results are in very good agreement where the maximum discrepancy observed is 4.24%. Keywords— Microstrip ring-resonator, coupling-gap, meat quality, dielectric characterization, dielectric constant, effective permittivity I. INTRODUCTION Evaluation of meat quality using dielectric properties has gained more interest in recent years. Using a dielectric method for freshness and quality assessment of meat has several advantages, such as: it is non-destructive, easy, rapid, effective and reliable [1, 2]. A large amount of research has been conducted to study meat properties on lower frequencies. Using KHz to MHz frequency range, the impedance variations has been used to identify meat quality aspects (freshness, tenderness, fat content), quality classes (such as PSE, DFD and RFN), detection of frozen, chemical contaminations and microbial activities [3]. However, relatively a small amount of literature is found in GHz range which is mainly related to evaluation of freshness, aging state, salting process and fat determination [3-5]. In microwave region, study of water content has great importance due to its dipolar relaxation. The main constituent of meat is water, which is about 70% of total mass [4]. During postmortem time due to various biochemical reactions & membrane modifications this amount of moisture reduces substantially. Thus, changing the meat permittivity significantly [5]. It is well known that the effective permittivity of a microstrip line has strong dependency on the permittivity of a medium above its surface [6]. Whereas, small permittivity variations in the above medium can be easily determined by its effective permittivity. Using overlay meat samples any variation in its permittivity can also be observed also. As mentioned before, this change basically represents the variation in water content held within muscles. The amount of water within a muscle is generally expressed as water holding capacity (WHC), where a good quality meat has higher WHC then a poor quality meat [1]. It has been reported before that the microstrip ring-resonator can be used for meat quality determination [7]. However, to detect a small variation among different meat samples (due to WHC) it is required to realize a resonator which is more sensitive. Thus, the main objective of this study is to increase the sensitivity of a resonator; hence, characterization of meat samples will be more easy and reliable. II. ANALYSIS OF CAPACITIVE COUPLING OF RING RESONATOR Microstrip ring resonator is considered as a closed-loop transmission line. To excite the resonator, power is capacitively coupled through feed lines and the gap between them. The resonance is produced when a mean circumference of the ring is equal to an integral multiple of the guided wavelength [8] 2 Ȝg for 1 ,2,3 r n n π = = … (1) Where r is ring radius, n is mode number and λ g is the guided wavelength. For resonance frequency, considering (1) with guided wavelength (Ȝ g ), will give 2 eff nc f r π ε = (2) However, this relation does not account for the coupling gap effect, thus valid only for loose coupling structures [9]. If the gap is reduced the gap capacitance will be increased hence coupling will be tight. This increase in gap-capacitance results in the deviation of a resonator’s inherent frequency to lower frequency, which is known as its “pushing effect” [9]. Although it lowers the insertion-loss but the effect on resonance frequency is more significant [8]. With symmetric feeding and without any discontinuity in the structure, the maximum field occurs at these gaps. Since the coupling region has maximum field point, hence, it will be more sensitive to overlay permittivity variations. Furthermore, there are also some design modifications to increase the coupling strength. Some of these coupling schemes found in literature are used to reduce the losses and increase the coupling strength [8]. As depicted in Fig 1 (a), the scheme is known as loose coupling. In this method, since the coupling strength is not much higher, its effect on resonance frequency is minimal. But the insertion loss is much higher, however, by selecting optimum gap size it can be reduced [8]. Another scheme is matched loose coupling, as its name implies, a matched stub has been used to increase the coupling strength, shown in Fig.1 (b). This method reduces the insertion 2014 IEEE Asia-Pacific Conference on Applied Electromagnetics (APACE) 8 - 10 December, 2014 at Johor Bahru, Johor, Malaysia 978-1-4799-6603-5/14/$31.00 ©2014 IEEE 191 NOTE: This article is not for mass dissemination but just for students and colleagues.