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The purpose of this paper is to present the design of a compact microstrip bandpass filter (BPF) in dual-mode configuration loaded with cross-loop and square ring slots on a square patch resonator for C-band applications.

In the proposed design, the dual-mode response for the filter is realized with two transmission zeros (TZs) by the insertion of a perturbation element at the diagonal corner of the square patch resonator with orthogonal feed lines. Such TZs at the edges of the passband result in better selectivity for the proposed BPF. Moreover, the cross-loop and square ring slots are etched on a square patch resonator to obtain a miniaturized BPF.

The proposed dual-mode microstrip filter fabricated in RT/duroid 6010 substrate using PCB technology has a measured minimum insertion loss of 1.8 dB and return loss better than 24.5 dB with a fractional bandwidth (FBW) of 6.9%. A compact size of 7.35 × 7.35 mm² is achieved for the slotted patch resonator-based dual-mode BPF at the center frequency of 4.76 GHz. As compared with the conventional square patch resonator, a size reduction of 61% is achieved with the proposed slotted design. The feasibility of the filter design is confirmed by the good agreement between the measured and simulated responses. The performance of the proposed filter structure is compared with other dual-mode filter works.

In the proposed work, a compact dual-mode BPF is reported with slotted structures. The conventional square patch resonator is deployed with cross-loop and square ring slots to design a dual-mode filter with a square perturbation element at its diagonal corner. The proposed filter exhibits compact size and favorable performance compared to other dual-mode filter works reported in literature. The aforementioned design of the dual-mode BPF at 4.76 GHz is suitable for applications in the lower part of the C-band.

This paper is aimed to study the design of a miniaturized filter with tri-band characteristics. In this paper, perturbation is used to realize circuit miniaturization and multi-band by exploiting the inductive property. During this process, vias are added for twofold benefit, namely, circuit miniaturization and enhanced frequency selectivity at high frequency. Thus, with the introduction of the shorting via, the single-band dual-mode bandpass filter is converted into a tri-band filter with a smaller electrical size.

This paper presents the design and characterization of a miniaturized two-port filter with tri-band operating characteristics. The proposed filter is constructed using a square patch resonator operating at 5.2 GHz with a capacitively coupled feed configuration. A square perturbation is added to the corner of the square patch to achieve diagonal symmetry and to excite dual mode. The perturbation offers a sharp transmission zero defining bandwidth of the proposed filter. In addition, a shorting post is introduced to achieve an 88% size reduction by lowering the operating frequency to 1.8 GHz.

The prototype filter has insertion less than 1.2 dB and return loss better than 12 dB throughout all the realized frequency bands. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The realized fractional bandwidths of the proposed bandpass filter are 11/5.6/1 at 1.8/4.6/5.85 GHz, respectively. The quality factor of the proposed antenna is greater than 80 and a peak Q-factor of 387 is realized at 5.85 GHz. The high Q-factor indicates low loss and improved selectivity. The rejection levels in the stopband are greater than 20 dB.

The results indicate that the proposed filter is a suitable choice for low-power small-scale wireless systems operating in the microwave bands. The realized filter has the smallest footprint of 0.36λ_eff  × 0.19λ_eff where λ_eff is the effective wavelength calculated at the lowest frequency of operation.

This paper aims to present the design of a compact quad-band coplanar-fed monopole antenna for tablet computer applications.

The antenna has the smallest size of 26 × 14 mm and supports GSM, Wi-Fi, WIMAX and Bluetooth. The proposed antenna consists of a coplanar fed main radiator, c-shaped stubs and parasitic meandered stub. The inverted c-shaped stubs enhance the bandwidth of upper frequencies. The resonance at 2.4 GHz is individually controlled by the coupled meandered stub.

The percentage bandwidth in the four operating bands are 8.7/4.12/27.8/13.3%. Furthermore, the antenna is integrated with the mock-up ground plane and specific absorption rate (SAR) calculations are performed. The estimated SAR is less than 1.6 W/kg for a 1 g body tissue. The gain and efficiency of the antenna are 3.56/4.37/4.97/6 dBi and 82.4/85/97.1/89.3%, respectively. The measured impedance and radiation characteristics of the fabricated prototype are in good correlation with the simulated results.

In the proposed work, vias and lumped elements are not used for lower band excitation, and most of the wireless applications in the tablet computers have been covered. Further, the effect of antenna with different orientation has been tested for the estimation of SAR.