Frequency‐dependent maximum average power‐handling capabilities of single and edge‐coupled microstrip lines on low‐temperature co‐fired ceramic (LTCC) substrates

The frequency‐dependent maximum average power‐handling capabilities (APHCs) of single and edge‐coupled microstrip lines (MLs) on low‐temperature co‐fired ceramic (LTCC) substrates are investigated in this article. Although LTCCs have excellent high‐frequency performance, the thermal conductivity is about 2.0–3.0 W/m°C, which is much smaller than that of sapphires, alumina, silicon, and GaAs. The method used to predict the APHC is based on the calculated conductive and dielectric attenuation constants for different modes, and the proposed multilayer thermal model for the temperature rise. Numerical investigations are carried out to examine the effects of geometric and physical parameters on the wideband pulse responses and maximum APHC for single finite‐ground thin‐film and coupled MLs, respectively. Methodologies to enhance the power‐handling capability which are useful in the design of high‐density microstrip interconnects on or embedded in multi‐layer LTCCs are proposed. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Microstrip multiplexer with four channels for broadband system applications

A microstrip multiplexer for broadband system applications from 10 to 21 GHz has been developed. The multiplexer consists of four microstrip bandpass filters with center passband frequencies at 10, 12, 19, and 21 GHz. The multiplexer efficiently suppresses the parasitic passbands of the 10‐ and 12‐GHz filters and balances the phase relationship among the multiplexer channels. A method for improving the parasitic passband rejection has been devised. Measured results show that parasitic passband rejection is more than 38 dB. Measured insertion losses are 1.81, 1.90, 2.88, and 2.51 dB at 10.3, 12.25, 19.4, and 21.285 GHz, respectively. Measured out‐of‐band isolation is more than 32 dB at all these frequencies. This multiplexer has applications in communication transceiver systems with dual‐channel receiver (12 and 21 GHz) and dual‐channel transmitter (10 and 19 GHz). © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 48–54, 2001.     

A comparative study of two techniques for improving power‐handling capability of CMOS T/R switches

This article proposes an asymmetric topology for transmit/receive (T/R) switches and more importantly presents a comparative study of both LC‐tuned and resistive body‐floating techniques for improving the power‐handling capability of the T/R switches in the same 0.18‐μm triple‐well CMOS. It is shown from simulations and measurements that the switches adopting either technique achieve comparable performances. For instance, the switch employing the LC‐tuned body‐floating technique exhibits insertion loss of 1.5 dB, isolation of 23.5 dB, and power‐handling capability of 22.5 dBm at 5.2 GHz, whereas the switch using the resistive body‐floating technique exhibits insertion loss of 1.3 dB, isolation of 24 dB, and power‐handling capability of 22.2 dBm, respectively. Therefore, one can conclude that the asymmetric topology with the resistive body‐floating technique is more suitable for designing T/R switches for wireless local area network applications as it consumes smaller silicon area. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

A novel balanced wideband power divider based on microstrip‐slot transitions

A novel design of a balanced wideband power divider (PD) with enhanced common‐mode (CM) suppression is proposed. The top and bottom layers of the structure contain tapered microstrip line. Those microstrip lines are coupled via slotline in the ground plane, which is located at the middle layer. With appropriate placement of the slotline, the coupling between the slotline mode and the differential‐mode (DM) signals can be maximized, while that between the slotline mode and the CM signals can be minimized. Simulated and measured results show that the proposed PD has equal power division, low insertion loss, and good return loss. In the measurement, the fractional bandwidth of the measured ?10 dB (DM) return loss is about 101% (1.82–5.35 GHz), the insertion loss for the DM signals is less than 5 dB, the suppression of the CM signals is higher than 45 dB, and the DM isolation is better than 10 dB over the fractional bandwidth. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:437–442, 2014.     

High gain microstrip antenna design for broadband wireless applications

This article presents a new broadband microstrip antenna for personal communications systems (PCS) applications. Using multilayer substrate structure with aperture‐coupled feed, a rectangular microstrip patch antenna operating at 1.9‐GHz band is designed and experimentally validated. This antenna configuration uses a quarter‐wave transformer to enhance the matching between the feed transmission line and the antenna patch. To demonstrate the design procedure, a first experimental broadband microstrip antenna prototype is designed and implemented. To analyse its performance, measurements are carried out and good performances are achieved. However, this prototype has a low front‐to‐back ratio. To overcome this drawback, an optimization process is proposed, and a second prototype is designed and successfully realized. To examine the effect of the optimization, experimental investigations are carried out on the second prototype. Very good agreement is obtained between numerical and measured results. Experimental results indicate that the proposed antenna achieves a bandwidth of 21%, a gain of 9.5 dB, and a front‐to‐back ratio of 20 dB, which are very sufficient for broadband wireless applications. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13, 511–517, 2003.     

An efficient method of designing dual‐ and wide‐band power dividers with arbitrary power division

Capability of microstrip nonuniform transmission lines (MNTLs) for construction of dual‐band and broadband unequal Wilkinson power dividers with arbitrary‐way, arbitrary frequency band operations, and arbitrary power divisions is evaluated. Also, the MNTL transformers are introduced for dual‐band/broadband matching of the unequal output impedances of the MNTL power divider with arbitrary output terminal impedances. The strip width of MNTLs is considered variable and is written as a truncated Fourier series expansion. To show the validity of the design procedure, three experimental MNTL Wilkinson power dividers, which are dual‐band two‐ and three‐way power dividers with different power divisions working at 1 and 3.4 GHz and one broadband equal power divider working from 0.4 to 1.8 GHz, have been designed and fabricated. In the first ones with power division of 1.5, outputs isolation and ports matching of less than ?30 dB are achieved. Next, an extended recombinant structure is presented for achieving three‐way MNTL power dividers with dual‐band operation. The measured isolation between outputs and ports matching are better than 30 dB and measured forward transmissions are between ?4.87 and ?5.45 in two passbands of the divider. Also, for the proposed broadband divider, the measured isolation between the outputs is better than 13 dB in 127% desired bandwidth. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

A low sampling clock,high bandwidth,master‐slave track and hold amplifier

A fully‐differential master‐slave track and hold amplifier (MSTHA), with one‐input, four‐output and nearly 20 GHz bandwidth is designed and fabricated in 0.13‐μm SiGe BiCMOS technology. Operating with a single +3.3 V supply, 0 V input direct‐voltage, 2 GHz sampling clock input and 5 dBm input power, the MSTHA achieves a spurious free dynamic range (SFDR) of less than ?31 dB up to 20 GHz, 0.5 mV_rms output noise amplitude (RMS, root of mean square) and totally power consuming about 1.3 W.     

Average power‐handling capability of the signal line in coplanar waveguides on polyimide and GaAs substrates including the irregular line edge shape effects

The average power‐handling capability (APHC) of the signal line in finite‐ground coplanar waveguides (FGCPWs) on polyimide and GaAs substrates is evaluated in this paper. In our approach, the ohmic loss of metal lines is characterized in different ways, and the effects of an irregular edge shape are also considered. The rise in temperature of the signal line is determined by single‐ and double‐layer thermal models, with the temperature‐dependent properties of the thermal conductivity of GaAs material treated appropriately. Parametric studies are carried out to investigate the overall effects of signal‐line width, thickness, conductivity, edge‐shape angle, and polyimide thickness on APHC. Some possible ways to enhance the APHC of these FGCPWs are also proposed. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Artificial neural networks in their simplest forms for analysis and synthesis of RF/microwave planar transmission lines

In this work, the multiplayer perceptron (MLP) and radial basis function (RBF) neural networks in their simplest forms are employed in function approximation for highly nonlinear and complex analysis and synthesis of the most commonly used planar RF/microwave transmission lines, that is, microstrip lines, coupled microstrip lines, and basic and shielded coplanar‐waveguides. Since the analysis and synthesis processes for these systems have “one‐to‐one mapping” relations with each other, a forward model is defined for the analysis process for all these types of the planar transmission lines; on the other hand, a reverse model is also considered for the synthesis of the same lines. This reverse model is realized by swapping some of the inputs/outputs in the analysis model, and training the neural networks accordingly. Both MLP and RBF types of neural models are applied to the four widely used anisotropic and isotropic dielectric materials: PTFE/microstrip glass, RT/Duroid 6006, alumina and gallium arsenide. The results are shown to agree very well with the targets. A low‐pass filter with 30‐dB attenuation frequency at 3.5 GHz on an alumina substrate is designed by the use of a neural‐network synthesis and its resulting performance agrees well with the one using analytical formulas for the synthesis. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Dual‐polarized high gain resonant cavity antenna for radio frequency energy harvesting

A Fabry pérot antenna with a multilayer superstrate having nonuniform unit cells has been investigated as a receiving antenna for radio frequency (RF) energy harvesting applications. Here, the primary radiator is selected as a dual‐polarized aperture coupled microstrip antenna with a double‐layer superstrate. This antenna excites orthogonal polarizations, vertical (V) and horizontal (H) in the frequency band of 6.2 and 5.8 GHz, respectively, due to the presence of two orthogonal H‐shaped slots in its ground plane. The proposed antenna provides a gain enhancement of 9.8 and 10.1 dBi at the respective frequencies. The rectifying circuit is designed for a frequency of 5.8 GHz using a voltage doubler topology. The circuit provides a power conversion efficiency of 41% at 0 dBm input power.     

An efficient method for analyzing nonuniformly coupled microstrip lines

This article presents an efficient method for analyzing nonuniformly coupled microstrip lines. By choosing a modal‐transformation matrix, the coupled nonlinear differential equations describing the symmetric nonuniformly coupled microstrip lines are decoupled using even‐ and odd‐mode parameters; the original problem is thus transformed into two single nonuniform transmission lines. A power‐law function of arbitrary order and having two adjustable parameters is chosen to better approximate the equation coefficients. Closed‐form ABCD matrix solutions are obtained and used to calculate the S‐parameters of nonuniformly coupled microstrip lines. Numerical results for two examples are compared with those from a full‐wave commercial package and experimental ones in the literature in order to demonstrate the accuracy and efficiency of this method. This highly efficient method is employed to optimize a cosine‐shape 10‐dB codirectional coupler, which has good return loss and high directivity performance over a wide frequency range. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot‐strip‐foam‐inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S₁₁ < ?10 dB) and side lobe level (SLL) of ?25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.     

Broadband gap‐coupled half‐hexagonal microstrip antenna fed by microstrip‐line resonator

Half‐hexagonal microstrip antenna (H‐HMSA) is a compact version of HMSA, as it resonates at the same fundamental mode frequency. In this article, a compact configuration of a single layer, broadband gap‐coupled H‐HMSA has been proposed. Gap‐coupled H‐HMSA is fed indirectly by a λ/2 microstrip‐line resonator. Broad bandwidth (BW) is achieved with an effective use of resonance introduced by λ/2 resonator and gap‐coupled half‐hexagonal radiating patches. A peak gain of 7.07 dBi and measured BW (S₁₁ ≤ ?10 dB) of 11.5% at the center frequency of 5.2 GHz have been achieved, which occupies a small volume of 0.023 λ₀³ including the ground plane. The radiation patterns remain in the broadside direction throughout the return loss BW. Simulated results of the proposed antenna configuration are experimentally validated with good agreement.     

Modified Wilkinson power divider with harmonics suppression and compact size for GSM applications

In this article, a modified microstrip Wilkinson power divider with harmonics suppression for GSM communications applications is presented. For low‐pass filter designing, one open stub, one radial resonator, and two rectangular resonators are used. According to results related to insertion losses (|S₂₁| and |S₃₁|), stopband is wide and equal to 7.5 GHz (3.4‐10.9 GHz), under the condition of 20 dB harmonic suppression level. The results show that at the designed frequency of 1.8 GHz, the input return loss (|S₁₁|) and output return losses (|S₂₂| and |S₃₃|) are better than 22 dB, and the isolation between of output ports (|S₃₂|) is better than 30 dB. The size of the proposed power divider is compact and equal to 10.6 × 14.6 mm². Finally, the proposed power divider was fabricated and the measurement results illustrate a good agreement with simulation results.     

A broadband circularly polarized slot antenna with a compact microstrip to CPW transition

A simple structure of broadband circularly polarized slot antenna based on coplanar waveguide (CPW) feeding is proposed in this article. To obtain circular polarization with a single feed, a transition from microstrip to CPW is designed to excite the even and odd modes of the CPW simultaneously. By adjusting the relative position and dimensions of the two circular patches introduced at the end of microstrip line and CPW, a 90° phase difference between two modes can be produced. When the two modes are coupled into the wide slot antenna, broadband circular polarization operation can be realized. The 10‐dB reflection coefficient bandwidth of the proposed antenna is 88.2% (2.49‐6.42 GHz) and 3‐dB AR bandwidth attains 50% (2.72‐4.49 GHz).     

A high‐gain compact circularly polarized microstrip array antenna with simplified feed network

A broadband high‐gain circularly polarized (CP) microstrip antenna operating in X band is proposed. The circular polarization property is achieved by rotating four narrow band linearly polarized (LP) microstrip patch elements in sequence. Since the conventional series‐parallel feed network is not conducive to the miniaturization of the array, a corresponding simplified feed network is designed to realize the four‐way equal power division and sequential 90° phase shift. With this feed network, the impedance bandwidth (IBW) of the CP array is greatly improved compared with that of the LP element, while maintaining a miniaturized size. Then, parasitic patches are introduced to enhance the axial ratio bandwidth (ARBW). A prototype of this antenna is fabricated and tested. The size of proposed antenna is 0.93λ₀ × 0.93λ₀ × 0.017λ₀ (λ₀ denotes the space wavelength corresponding to the center frequency 10.4 GHz). The measured 10‐dB IBW and 3‐dB ARBW are 13.6% (9.8‐11.23 GHz), 11.2% (9.9‐11.07 GHz) respectively, and peak gain in the overlapping band is 9.8 dBi.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

High frequency integrated feed for front end circuitry and antenna arrays

Low‐cost printed circuit board waveguide (PCBWG) technology is employed to develop new waveguide‐fed microstrip antenna arrays with low profile and light weight while maintaining high efficiency and gain at 12.5 GHz. The proposed corporate feed network has two parts: on the antenna layer, microstrip lines are used to form a 2 × 4 sequentially rotated sub‐array of circularly polarized microstrip patches and on the feed layer PCB‐WG is utilized to combine any number of these sub‐arrays to form a larger array. Because PCB‐WGs transmit the power over a large portion of the feed network, losses are substantially reduced and spurious radiations from feed circuit are eliminated. Several microstrip arrays with PCBWG feed were designed and fabricated using standard PCB process. Comparing the results with those of a hybrid array with conventional waveguide feed shows that there is only a negligible degradation in gain and efficiency when bulky and expensive aluminum waveguides are replaced by PCB‐WGs. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Hybrid wideband dual‐cylindrical circularly polarized dielectric resonator antennas excited with S‐shaped microstrip feed for sub‐6 GHz frequency range

In this article, a hybrid microstrip fed dual‐cylindrical dielectric resonator antenna (dual‐CDRA) has been proposed for the sub‐6 GHz band application with a wide circular polarization band. The proposed hybrid microstrip feed cylindrical dielectric resonator antenna utilizes an S‐shaped microstrip feed line to excite fundamental HE_11δ like mode and hybrid mode in dual‐CDRAs. The presented antenna structures are acting as monopole antenna separately with 48.75% (3.88‐6.38 GHz) bandwidth whereas both radiators called dual‐CDRAs enhances the bandwidth up to 93.06% (2.16‐5.92 GHz) in addition with an axial ratio bandwidth of 15.2% (3.52‐4.1 GHz). The proposed antenna is applicable for WiMAX (3.4‐3.69 GHz), and WLAN application of 802.11d and 8.02.11e IEEE standard. For validation of simulated results, an antenna prototype has been fabricated and experimentally verified. A good agreement between simulation and measured results are obtained. The simulation results have been carried out by using Ansys HFSS 14.0 version software.     

Low loss multilayer microstrip line for monolithic microwave integrated circuits applications

This paper describes the multilayer microstrip structure using low dielectric constant polyimide as a buffer layer between the microstrip conductor and the GaAs substrate to reduce dissipation loss, especially for very high impedance microstrip lines. The new structure provides about half the dissipation loss and about 40% higher characteristic impedance in comparison to the conventional microstrip line on GaAs substrate having the same conductor widths. An empirical formula for the equivalent dielectric constant compatible with commercial computer-aided design tools was developed to design monolithic microwave integrated circuits (MMICs) using this medium. The multilayer microstrip structure is compatible with ITT's 4′ MSAG^® process which uses polyimide for crossovers and scratch protection. The present structure has great potential in realizing low loss and wideband matching networks including low noise, high power, and high efficiency amplifiers, and passive components on GaAs substrate with improved insertion loss and bandwidth performance, and three-dimensional MMICs. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 441–454, 1998