Compact Microstrip Resonant Cell Research Articles

An Efficiency-Improved Inverse Class-[formula omitted] Power Amplifier Design Using a Novel Metamaterial-Based Harmonic Control Circuit

In this article, an efficiency-improved inverse class-F2,3 (class-F2,3-1) power amplifier (PA) is designed and implemented using a novel harmonic control circuit (HCC) based on a metamaterial structure. It is proposed to utilize a bi-band, compact microstrip resonant cell (CMRC) inspired by the split ring resonator (SRR) that behaves like an HCC, to control concurrently the second and third harmonics. The main objective is to demonstrate the potentiality and versatility of SRRs for suppression of un-wanted harmonics in microwave PAs, shaping voltage and current waveforms, miniaturization (due to subwavelength operation of SRRs), as well as improving the performance of the PA. The recommended architecture is validated by the design, fabrication and testing of a metamaterial-based class-F2,3-1 PA utilizing a commercial 10 W GaN-HEMT device. The proposed PA yields a power added efficiency (PAE) of 78%, a drain efficiency (DE) of 83.3%, a saturated output power of 41 dBm, and a gain of 16.8 dB at 3.5 GHz.

Dual-Band Dual-Polarized Shared-Aperture Grid Antenna With Large Frequency Ratio

In this letter, a dual-band dual-polarized shared-aperture grid antenna with a large frequency ratio is presented. To achieve shared aperture and large frequency ratio, a millimeter-wave (mm-Wave) partially reflective surface (PRS) is embedded into a microwave patch antenna. A periodic circular grid patch is adopted not only as the microwave antenna but also as the mm-Wave PRS antenna. The mm-Wave PRS antenna is centrally excited by a cross-shaped waveguide with two coaxial connectors, and the microwave patch antenna is driven by a pair of orthogonal L-shaped probes, resulting in polarization diversity in both bands. A compact microstrip resonant cell (CMRC) and a metal post are designed to reduce the couplings between different ports. For demonstration, a prototype operating in the 3.5 GHz and 28 GHz bands is fabricated and measured. The overlapped measured -10 dB impedance bandwidths between the orthogonal ports cover 3.41–3.59 GHz (5.14%) and 26.62–30.26 GHz (12.8%) in the low and high bands, whereas the measured peak realized gains of 8.75 dBi and 12.79 dBi are obtained, respectively. All port-to-port isolations are larger than 20 dB over the bands of operation.

Generalized Complex-to-Complex Impedance Transformers Based on Conjugately Characteristic-Impedance Transmission Lines

The novel technique of generalizing complex-to-complex impedance transformers (CCITs) with miniaturization is introduced in this paper. The generalized CCITs are designed based on conjugately characteristic-impedance transmission lines (CCITLs) along with the Meta-Smith charts (MSCs), resulting in convenient design equations. For illustration, a prototype of generalized CCITs is designed, simulated, and implemented with an asymmetric compact microstrip resonant cell (ACMRC), which is one of the CCITLs. The measurement results confirm that the proposed technique offers approximately 28.5% shorter in physical length compared to the CCIT designed using standard transmission lines.

Low-Pass Filter Based Integrated 5G Smartphone Antenna for Sub-6-GHz and mm-Wave Bands

To maintain the compactness of future 5G smartphones, integration of sub-6 GHz and millimeter-wave (mm-wave) bands is a challenging task due to the large frequency ratio. We, therefore, propose a single-fed triple-band antenna with a large frequency ratio. The proposed antenna is composed of a microstrip patch radiator with an inverted U-shaped slot for dual-band operation in the mm-wave frequencies (28 and 38 GHz). A meandered radiating structure is linked to the microstrip patch radiator through a compact microstrip resonant cell (CMRC) low-pass filter (LPF), which is used for the integration of these structures to be operated at 3.5 GHz. A compact size of 22 mm ×10 mm ×0.508 mm for the proposed antenna was realized by incorporating the radiator slot, an LPF, the truncated ground, and a meandered line structure. Wide, decoupled -10 dB bandwidths of 12.9%, 5.8%, and 2.4% at 3.5, 28, and 38 GHz, respectively, were realized for the proposed MIMO antenna without utilizing an external decoupling structure. A detailed safety study with respect to specific absorption rates and power densities was analyzed in data, reading, and talking modes. Finally, the measurements were performed in an anechoic chamber, and the measured results were in a good correlation with the simulation results.

Compact bandpass filter based on single isosceles right triangular substrate integrated waveguide cavity and modified complementary compact microstrip resonant cell

Compact bandpass filter based on single isosceles right triangular substrate integrated waveguide cavity and modified complementary compact microstrip resonant cell

Compact Wideband Dual-Band SIW Bandpass Filters

A novel method to design compact wideband dual-band substrate integrated waveguide (SIW) bandpass filters (BPF) is proposed in this paper. By loading a novel beeline compact microstrip resonant cells (BCMRCs) with band-gap characteristics on top layer of SIW, two wide passbands separated by a stopband are generated. In order to enable the filter to have lower reflection coefficients in the two passbands, we use a tapered gradient line embedded with rectangular slots and loaded open stubs as the transition structure from microstrip line to SIW. The wideband dual-band BPF (DBBPF) is fabricated. The lower-band and upper-band fractional 3-dB bandwidths are 58.2% and 22.6%, while the measured minimum insertion losses (ILs) are 0.7 and 0.92 dB, respectively. The stepped-impedance openloop ring resonator (SIOLRR) is introduced in order to improve the selectivity of the filter. The wideband DBBPF with SIOLRR is studied, simulated and measured. Two transmission zeros are generated in the stop band between the two passbands. Good agreement between simulated and measured results can be obtained.

A compact coupler design using meandered line compact microstrip resonant cell (MLCMRC) and bended lines

In this paper, a novel branch-line coupler using meandered line compact microstrip resonant cell (MLCMRC) and bended lines is proposed. The presented coupler works at 0.9 GHz, with good specifications. The measured values of S12 and S13 at 0.9 GHz are 3.2 dB and 3.3 dB, respectively, which show better than 0.3 dB insertion loss in the pass band. The measured value of S14 is better than 36 dB and S11 is better than 31 dB. The proposed design can eliminate 3rd and 5th harmonic with high suppression level (more than 40 dB) and reduce the size of the circuit more than 64% compared to the conventional branch-line coupler. The presented coupler has a very simple structure, which can be used in modern communication applications.

A Portable Microwave Interferometry Sensor for Permittivity Detection Based on CCMRC

A portable microwave complex permittivity sensor based on the interferometry configuration is proposed. A complementary compact microstrip resonant cell (CCMRC) is applied as the sensitive element, which converts the dielectric information of the material under test (MUT) into the phase variations of its transmission coefficient. A miniaturized interferometry platform based on a down-converting mixer further translates the phase change into DC output voltage variation, which can be readily recorded with a direct readout circuit. In this context, expensive and bulky vector network analyzer is no longer needed, thereby leading to a low hardware cost. With comprehensive theoretical analysis, the material permittivity is simply extracted using a specific extrapolation algorithm. As a proof of concept, several different solid material samples with known permittivity values are used to verify the devised detection system.

Design of a high efficiency class-F power amplifier with large signal and small signal measurements

In this paper, a modified class-F power amplifier is designed and implemented with new method at 900 MHz frequency. The meandered line compact microstrip resonant cell (MLCMRC), with simple structure is proposed to use as a harmonic control circuit (HCC). The proposed MLCMRC correctly acts as open-circuit at third and fifth harmonics and acts as short-circuit at second and fourth harmonics. In this design, the proposed PA is integrated with simple MLCMRC, while the large conventional matching lines are omitted, which leads to harmonics suppression, size reduction, and PAE improvement at same time. The proposed class-F power amplifier is characterized by small-signal and large-signal measurements to evaluate its performance. The maximum obtained gain for the proposed PA is 18.5 dB. Also, this design can obtain 74% PAE under 15 dBm input power, which shows 5% and 10% improvement in the maximum gain and PAE, respectively compared to the conventional class-F PA. Moreover, the applied MLCMRC resulted in the 36% size reduction, compared to the same PA without MLCMRC.

Design of a Compact 2.4 GHz Class-F Power Amplifier with High Power Added Efficiency

ABSTRACTDesign of a compact 2.4 GHz class-F power amplifier (PA) with high power-added efficiency (PAE) using a novel harmonic control circuit (HCC) is reported. The main aims of the proposed PA are to obtain compact size and high PAE. The proposed HCC consists of an input matching circuit, a lampshade compact microstrip resonant cell (LCMRC) and output matching network (OMN). The HCC input matching circuit is employed to reduce the capacitive and inductive effects of the transistor. A part of the input matching circuit is replaced with a LCMRC to have more suppression at the third harmonic (7.2 GHz). The HCC OMN consists of two transmission lines for matching fundamental harmonic. The optimum values of the circuit parameters are obtained by harmonic balanced analysis at a drain voltage of 3 volts. The measured values of PAE and output power at 2.4 GHz are 83% and 23.65 dBm, respectively under 10 dBm input power. Furthermore, the fabricated amplifier occupies an area of 45 × 35 mm2 only.

Compact bandpass filter using CMRC‐based dual‐behavior resonator

This article presents a novel bandpass filter (BPF) using two proximity-coupled dual-behavior resonators (DBRs). The employed DBR is implemented by a single shunt stub with the compact microstrip resonator cell at its open end instead of the traditional dual stubs in cross-shape. Due to the adoptions of the proposed DBR and proximity-coupling scheme, both the transverse and longitudinal dimensions of the proposed BPF are reduced significantly. To verify the proposed idea, a demonstration microstrip BPF is designed and fabricated, and good agreement between the simulated and measured results can be observed, showing low loss and high selectivity due to four transmission zeroes in the stopband.

Design of a full W‐band detector based on Schottky diode with quartz substrate

A power detector based on Schottky diode with a quartz substrate is proposed in this study. A three-dimensional model of the Schottky diode is built for accurate performance evaluation. A broadband input DC grounding circuit is designed based on two sets of radial stubs. An output chocking circuit is implemented using a single compact microstrip resonator cell, which features compact size and broad stopband. Input and output matching circuits are also introduced to achieve flat frequency response. Measured results agree well with simulated ones. The voltage sensitivity is about 6000–9500 mV/mW with −30 dBm drive power at the full W-band (75–110 GHz). The detector also has outstanding temperature stability. The output voltage varies <6.3% with −3 dBm drive power when ambient temperature changes from −40 to +60°C.

A Dual-Band Shared-Aperture Antenna With Large Frequency Ratio, High Aperture Reuse Efficiency, and High Channel Isolation

The operating frequency of future communication systems will cover unlicensed millimeter-wave bands as well as existing microwave bands. Large frequency ratio antennas that can be applied to both frequency bands simultaneously and maintain the high isolation between the two channels are difficult to design. This paper presents a new design of dual-band shared-aperture antenna based on the concept of structure reuse. The antenna consists of a patch antenna working at 3.5 GHz and a 12 × 12 substrate integrated waveguide (SIW) slot array antenna working at 60 GHz. The frequency ratio of this shared-aperture antenna is 17. In this design, the overall structure of the SIW slot array antenna is employed as the radiator of the patch antenna. With this new scheme, the high aperture reuse efficiency can be achieved. Meanwhile, the millimeter-wave antenna based on the SIW technology has the high-pass nature to reject the lower frequency signal. A compact microstrip resonant cell that acts as a low-pass filter is connected in series on the feedline of the microwave antenna to suppress the upper frequency signal. Thus, the channel isolation between the patch and the SIW slot array antennas can be more than 130 dB at 3.5 GHz and 65 dB at 60 GHz.

Single‐fed 4G/5G multiband 2.4/5.5/28 GHz antenna

In this study, a single-fed printed multiband antenna for 4G/5G wireless communication systems is presented. The proposed multiband antenna consists of Franklin strip monopole antenna to cover 4G, and wireless applications (WLAN and WiMAX), and a rectangular patch antenna that is designed to cover 5G band. Furthermore, a modified compact microstrip resonant cell low-pass filter is printed between the antenna parts to allow feeding the Franklin antenna at low-frequency bands while isolating the Franklin antenna from the rectangular patch at the 5G band. The proposed antenna is designed on Rogers 5880 with compact size 45 × 40 × 0.508 mm 3 . The proposed antenna is utilised to operate at triple band: 2.4, 5.5 and 28 GHz with wide impedance bandwidth (15.8, 23.5 and 11.3%) and the gain reaches (1.95, 3.76 and 7.35 dBi).

A modified class-F power amplifier with miniaturized harmonic control circuit

In this paper, a modified class-F power-amplifier (PA) for GSM applications is designed, simulated and tested. In this design, novel symmetrical meandered lines compact microstrip resonant cell (SMLCMRC), is proposed as a new harmonics control circuit (HCC), which resulted in size compression, power added efficiency (PAE) enhancement, power gain improvement, and better linearization in the PA. In this work both of the conventional class-F amplifier and proposed amplifier with SMLCMRC is designed at 1.8 GHz. The measurements show that the proposed PA with SMLCMRC has 72.54% maximum PAE, 17.13 dB gain and the 1 dB compression point (P1dB) is about 35.1 dBm. These results show, 16.5% improvement in PAE, 1.33 dB increment in gain and 1.1 dB improvement in linearity operating range of proposed amplifier compared to the conventional PA.

Inverse modeling for fast design optimization of small-size rat-race couplers incorporating compact cells

In the paper, a framework for computationally-efficient design optimization of compact rat-race couplers (RRCs) is discussed. A class of hybrid RRCs with variable operating conditions is investigated, whose size reduction is obtained by replacing ordinary transmission lines with compact microstrip resonant cells (CMRCs). Our approach employs a bottom-up design strategy leading to the development of compact RRCs through rapid design optimization of its building blocks and a subsequent fine tuning to account for parasitic cross-coupling effects. The fundamental component of the proposed method is an inverse CMRC surrogate model, covering a wide range of cell electrical parameters, and enabling a convenient adjustment of coupler bandwidth. Having the surrogate model established, it is possible to produce close-to-optimum CMRC dimensions at a negligible computational cost. The subsequent correction step requires only up to two electromagnetic simulations of the CMRC. The proposed method is demonstrated by designing an RRC for several operational bandwidths. Experimental results are also provided.

A Frequency Synthesizer Based Microwave Permittivity Sensor Using CMRC Structure

In this paper, a high-sensitive microwave dielectric sensor targeted for material permittivity characterization is proposed. A reflective voltage controlled oscillator is devised by virtue of the compact microstrip resonant cell (CMRC) and embedded into a fractional- $N$ phase-locked loop frequency synthesizer. The CMRC structure, covered with material under test, changes its resonating characteristics and, hence, the initial oscillating frequency. Due to the presence of the frequency synthesizer, this frequency shift is finally translated into the controlling voltage variation. In this paper, the material permittivity is extracted by measuring the voltage deviation. Several different samples with known permittivity values are tested to verify the effectiveness of the design sensing platform.

Low-cost multiband compact branch-line coupler design using response features and automated EM model fidelity adjustment

Design closure of compact microwave components is a challenging problem because of significant electromagnetic (EM) cross-couplings in densely arranged layouts. A separate issue is a large number of designable parameters resulting from replacement of conventional transmission line sections by compact microstrip resonant cells. This increases complexity of the design optimization problem and requires employment of expensive high-fidelity EM analysis for reliable performance evaluation of the structure at hand. Consequently, neither conventional numerical optimization algorithms nor interactive approaches (e.g., experience-driven parameters sweeps) are capable of identifying optimum designs in reasonable timeframes. Here, we discuss application of feature-based optimization for fast design optimization of dual- and multiband compact couplers. On one hand, design of such components is difficult because of multiple objectives (achieving equal power split and good matching and port isolation for all frequency bands of interest). On the other hand, because of well-defined shapes of the S-parameter responses for this class of components, feature-based optimization seems to be well suited to control multiple figures of interest as demonstrated in this work. Two-level EM modeling is used for further design cost reduction. More importantly, we develop a procedure for automated determination of the low-fidelity EM model coarseness that allows us to find the fastest possible model that still ensures sufficient correlation with its high-fidelity counterpart, which is critical for robustness of the optimization process. Our approach is illustrated using two dual-band compact couplers. Experimental validation is also provided.

A novel compact and high performance bandpass filter based on SIW and CMRC technique

Based on the substrate integrated waveguide (SIW) and compact microstrip resonant cell (CMRC) technique, a compact and high performance planar bandpass filter (BPF) is proposed in this paper. The SIW cavity, which has the advantages of high quality and low insertion loss, provides a highpass characteristic. The CMRC structure etched on the top metal plane of the SIW cavity behaves as a lowpass filter, and it can also effectively reduce the dimension of the filter. In order to improve the out-of-band rejection and sharpen skirt selectivity, the open circuit lines at the input and output ports of the filter are introduced. Moreover, the bandwidth and center frequency of the proposed filter can be flexibly tuned by adjusting the cutoff frequencies of the SIW and CMRC separately. As a verification, a representative BPF having a center frequency of 4.54GHz and a 3dB bandwidth of 1.39GHz is designed, fabricated, and experimentally evaluated. The simulated and measured results are in good agreement.

A compact microstrip low-pass filter with ultra wide stopband using compact microstrip resonant cells

In this paper, a novel compact microstrip low-pass filter (LPF) with ultra wide stop band and sharp roll off, is proposed. In the proposed structure, a high impedance transmission line is loaded by compact microstrip resonant cells, which results in ultra wide stopband. The −3 dB cut-off frequency of filter is 1.5 GHz and the maximum insertion loss is &lt;0.1 dB in the passband. The proposed LPF presents extremely wide stopband from 1.68 to 44 GHz, with more than the −20 dB attenuation level, which suppresses the 2nd to 29th harmonics with high rejection levels. The size of the proposed LPF is only 0.1 λg × 0.19 λg, which shows excellent size reduction. There is a good agreement between the simulated and measured results.