In this article, the development of a high-efficiency power amplifier (PA) with the inverse class-F configuration and a novel 3/4 spiral defected ground structure (DGS) is presented. The proposed DGS structure has improved rejection characteristic and its resonance frequencies are more convenient to adjust than conventional symmetric and asymmetric spiral structure. The electromagnetic-simulated result shows that the proposed circuit has improved harmonic control performance with simplified structure and less return loss than the conventional microstrip harmonic control circuit. The 3/4 spiral harmonics control circuit (HCC) can be modeled by three parallel RLC resonators. Using the proposed structure a high-performance harmonic control circuit is designed for implementing an inverse class-F PA. For comparison, two inverse class-F PAs operating at 2.4 GHz have been implemented by the microstrip HCC and the proposed HCC, respectively. According to the experiment results, the size of the proposed inverse class-F PA is reduced by 20%, the power-added efficiency and the gain are increased by 4.8% and 1.5 dB, respectively.

The narrow bandwidth of microstrip antennas is one of the most important features that restrict its wide usage. This paper presents a new coplanar waveguide-fed compact rectangular microstrip antenna with the improvement of the bandwidth using the slot geometry and cutting rectangular periodic edges for the patch radiator. To develop this structure, we have conducted many optimization and investigation using Momentum Software integrated into ADS “Advanced Design System” and comparison of the results with CST Microwave Studio. The comparison between the simulation and measurement results permits to validate the final achieved antenna with an improvement of the bandwidth. This antenna has wide matching input impedance ranging from 1.7 to 3.5 GHz with a return loss less than −10 dB, corresponding to bandwidth 69.7% at 2.6 GHz as a frequency center. The antenna achieved is a low cost, planar, and easy to be fabricated, thus promising for multiple applications in wireless communication systems. Details of the proposed antenna design and both simulated and experimental results are described and discussed.

This paper furnishes a compact modified hourglass-shaped aperture-coupled antenna for radar applications. The effect of slots of various shapes and various slot lengths on the input impedance, radiation pattern, and gain of the antenna are analyzed. The proposed antenna, designed using a modified hourglass-shaped aperture, offers a gain of 8.214 dBi for an compact antenna with a dimension of 20.4 × 20.4 × 1.041 mm3 and an aperture area of 2.495 mm2. Implementation of this proposed modified hourglass-shaped aperture offers a high gain per unit radiating patch area of 40.26 dB/$\lambda _g ^2$ and a high gain per unit aperture area of 1324.84 dB/$\lambda _g ^2$. The proposed aperture feeds a circular patch which radiates at its resonant frequency of 10.5 GHz. The proposed design is fabricated and the simulated results are verified experimentally. Equivalent circuit analysis is also done. A measured gain of 7.2 dBi is observed at 10.5 GHz. The physical area of the antenna is reduced without compromising the gain by judiciously choosing the shape of slot with more degree of freedom for impedance matching. The proposed antenna is well suited for the unit cell of phased array antennas for X-band missile radar applications.

A new compact wideband filtering balun based on substrate-integrated suspended line technology is presented in this brief. The proposed device is composed of a λg/4 suspended stripline open-circuited stub, a λg/2 suspended stripline resonator, and a λg/2 suspended slotline resonator. These striplines and slotline are encapsulated in an electromagnetic (EM) shielding box consisting of air cavity, surrounding substrate layers, and metal layers to achieve EM shielding performance. By properly exciting the suspended stripline and slotline resonators, three transmission poles are generated to achieve high frequency selectively. The intrinsic 180∘ phase difference between the two output ports can be obtained by using the electric field distribution caused by the perpendicular coupling between the suspension stripline and the slotline resonator. The wideband passband is achieved with magnitude balance and out-of-phase properties. To validate our proposal, a wideband filtering balun operating at 2.56 GHz with fractional bandwidth of 65.6% is designed and fabricated.

This paper reports the test results of a small-scale prototype that implements a digitally beam-formed phased antenna array in the E-band. A four-channel dual-conversion receive RF module for 71–76 GHz frequency band has been developed and integrated with a linear end-fire antenna array. Wideband frequency-domain angle-of-arrival estimation and beam-forming algorithms were developed and implemented using Orthogonal Frequency Division Multiplexing (OFDM) with Quadrature Phase-Shift Keying (QPSK) at 1 Gbps. Measured performance is very close to the simulated results and experimental data for an analogue-beam-formed array. This work is a stepping stone toward practical realization of larger hybrid arrays in the E-band.

It is difficult to detect a stationary object in practice, especially in an unknown indoor environment, because (a) there is no distinct speed difference between the targets and the background; (b) responses of the targets are contaminated by dense unknown clutter; (c) a priori knowledge of the background is not always available for some scenarios. In this paper, a set of ultra-wideband sensors are used to detect a stationary target with a planar diffuse surface. It is shown that, the relative spectrum-shifts of the data after data-projection operation, are closely connected to the illumination-angle differences. Based on this, a detector is designed, and the location and the orientation of the target are determined. In order to mitigate the influence of clutters, a “time-shift & accumulation” scheme is designed to enhance the signal. As a consequence, the signal-to-interference-and-noise ratio is increased. In addition, results from measurement in a realistic indoor environment are provided.

A miniaturized high-isolation quadplexer with wide upper-stopband based on open and short stub-loaded multimode-resonator is proposed in this paper. Based on the theory of multimode-resonator and stepped impedance resonator (SIR), the compact quadplexer is designed by using multimode-resonator and SIR. In order to further miniaturize the size of the circuit, the multimode resonator is employed as the common resonator to replace the common matching network of the quadplexer and the SIRs are curved. Equivalent topology circuit is given to analyze and design the quadplexer. Detailed analyses are given according to the equivalent circuits. The proposed compact quadplexer working at central frequencies of 1.8, 2.4, 2.8, and 3.5 GHz with over 40 dB isolation is finally simulated, fabricated, and measured. The measured results agree well with the simulated ones. The total size of the fabricated quadplexer is 0.36 λg × 0.42 λg.

The front-end circuitry of transceiver modules is slowly being updated from GaAs-based monolithic microwave integrated circuits (MMICs) to Gallium-Nitride (GaN). Especially GaN power amplifiers and T/R switches, but also low-noise amplifiers (LNAs), offer significant performance improvement over GaAs components. Therefore it is interesting to also explore the possible advantages of a GaN mixer to enable a fully GaN-based front-end. In this paper, the design-experiment and measurement results of a double-balanced image-reject mixer MMIC in 0.25 μm AlGaN/GaN technology are presented. First an introduction is given on the selection and dimensioning of the mixer core, in relation to the linearity and conversion loss. At the intermediate frequency (IF)-side of the mixer, an active balun has been used to compensate partly for the loss of the mixer. An on-chip local-oscillator (LO) signal amplifier has been incorporated so that the mixer can function with 0 dBm LO input power. After the discussion of the circuit design the measurement results are presented. The performance of the mixer core and passive elements has been demonstrated by measurements on a test-structure. The mixer MMIC measured conversion loss is <8 dB from 6 to 12 GHz, at 1 GHz IF and 0 dBm LO power. The measured image rejection is better than 30 dB.

By introducing a modified F-shaped feeding strip and dual parasitic shorted strips, a small-size wireless wide area network/long-term evolution (WWAN/LTE) printed antenna is proposed and embedded in the 4 G mobile phone with octa-band operation. The operating impedance bandwidths (RL ≥ 6 dB) of 263/1093 MHz can be obtained across the LTE/WWAN bands, respectively. The overall antenna size of the proposed printed monopole antenna (MA) is only 35 × 10 × 0.8 mm3. Meanwhile, this small-size MA provides the measured peak gains and antenna efficiencies of 2.0/3.6 dBi and 80/75% for the LTE/WWAN bands, respectively.

In this paper, an antenna-to-antenna method to design high-efficiency polarization converters was proposed. Two in-linked split ring resonators (SRRs) were used as the fundamental unit cell, which can effectively make the original linear polarization angle deflected into a customized one (include but not limited to 90°). The same as the process of energy reception and transmitting of microstrip symmetric dipole antennas, the top SRR plays the role of a receiving antenna and the bottom one acts as a transmitting antenna. Under normal illumination, the strong coupling between electric resonance and magnetic resonance can result in high transmission and broad bandwidth. Since the two SRRs act as two independently polarization selective components, the polarization angle of transmitted waves can be easily controlled by rotating the transmitting SRRs around the center. The proposed concept and the design method are validated using numerical simulations, as well as experimental results of three examples for 45, 60 and 90° polarization angle rotation, the polarization conversion ratio of which is about 92.2, 88.9 and 91.9% from 7.5 to 10 GHz.

A triple-frequency operated concentric annular ring microstrip antenna which is single fed is presented. The proposed antenna with three concentric annular rings and two symmetrical notches on its outer ring and having a cross slot in its ground surface shows triple band at resonance frequency 1.22760, 1.57542, and 2.18 GHz, respectively. At the first two bands (GPS L2 and GPS L1), circular polarization characteristic is observed and the third band observes linear polarization finding its application in Universal Mobile Telecommunication System (UMTS). The complete dimension of the antenna designed and fabricated is only 51.6 × 51.6 × 1.6 mm3. Experimental results depict the proposed antenna gain of 3.31, 3.55, and 3.50 dBi in three bands, respectively, and closely matches with the theoretical results.

In this paper, a rectangular dielectric resonator antenna (DRA) with a parasitic gap-coupled microstrip resonator (MSR) is investigated; analytically, and experimentally. The proposed antenna uses an open-ended half-wavelength MSR patch as a hybrid radiator. Radiating modes are identified for both the radiators. Two separate and fully independent modes are merged together to get an enhanced bandwidth. The antenna can offer three modes of operation, mode 1 (only DRA is active), mode 2 (only MSR is active), and the mode 3 (both DRA and MSR are active). In mode 3, the antenna offers a single wideband operation with ≈11% bandwidth by merging modes 1 and 2 with a broadside radiation pattern. Two switches are proposed to realize the three modes of operation. A p–i–n diode is utilized as switching element in simulations. Multiple antennas have been fabricated using a small metal strip as a switch to validate the proposal. Analytical, simulated, and measured results are found in harmony. A parametric study is done to describe the antenna characteristics. An approximate lumped element model is also extracted and presented.

This paper presents the performance study of a 248 GHz voltage-controlled hetero-integrated signal source using indium phosphide (InP)-on-bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. The source consists of a voltage controlled oscillator (VCO) in 0.25 µm BiCMOS technology and a frequency multiplier in 0.8 µm transferred-substrate InP-heterojunction bipolar transistor technology, which is integrated on top of the BiCMOS monolithic microwave integrated circuit in a wafer-level based benzocyclobutene bonding process. The vertical transitions from BiCMOS to InP in this process exhibit broadband properties with insertion losses below 0.5 dB up to 325 GHz. The VCO operates at 82.7 GHz with an output power of 6 dBm and the combined circuit delivers −9 dBm at 248 GHz with 1.22% tuning range. The phase noise of the combined circuit is −85 dBc/Hz at 1 MHz offset. The measured output return loss of the hetero-integrated source is >10 dB within a broad frequency range. This result shows the potential of the hetero integrated process for THz frequencies.

This paper presents a new artificial neural network (ANN)-based radar data processing approach for the detection of breast cancers located inside fibro-glandular tissues. The aim is not the breast imaging but detecting tumors through ANN processing of data extracted from the radar signals measured around the breast. The proposed approach has been assessed using several realistic two-dimensional breast geometries derived from the models provided by the numerical breast phantom repository of the University of Wisconsin Cross-Disciplinary Electromagnetic Laboratory (UWCEM). The pulsed radar system was assumed to operate in the mono-static configuration. The obtained results showed the abilities of the proposed approach to detect, for any single radar trace, tumors located inside the fibro-glandular tissues with a sensitivity of 93%, a specificity of 90%, and an overall accuracy of 92%.

An ultra-wideband (UWB) highly compact bandpass filter with extremely high passband bandwidth is presented. The proposed structure is made using three-staged stepped-impedance lines and a composite right/left-handed transmission line (CRLH-TL) synthesized with meander fractal like ring slot in the ground and series capacitive gap in conductor strip. The capacitive gap in conductor strip and meander fractal like ring slot in the ground plane play major role for controlling the lower and higher cut-off frequencies. The equivalent circuit model of proposed filter is demonstrated and lumped parameters are extracted. A prototype is fabricated to experimentally validate the performance of proposed filter. The proposed UWB filter has extremely wide −10 dB return loss passband bandwidth from 3.14 to 18.26 GHz with relative bandwidth of 142% and insertion loss better than 0.5 dB. Also it achieves a wide upper-stopband from 19.7 to 24.4 GHz with insertion loss better than 13.0 dB, return loss <1.5 dB and sharpened rejection skirts outside the passband at both lower and upper frequency ends. Good agreement is found between simulated and measured results with measured group delay variation in the passband <0.65 ns.

A recently proposed technique for the distributed modeling of extrinsic parasitic effects in electron devices is used for the very first time in conjunction with a lumped equivalent circuit model for the intrinsic device.

Nonlinear modeling of 0.1 μm InP HEMTs for W-band applications is considered here, leading to extremely accurate predictions of harmonic distortion and power added efficiency at the fundamental frequencies of 27 and 94 GHz.

The distributed parasitic network is identified through accurate electromagnetic simulations up to the upper frequency limit of the millimeter-wave band (300 GHz), while standard pulsed I/V and S-parameter measurements up to 67 GHz are used for the identification of the intrinsic device model.

The use of 130-nm CMOS for power amplifiers at 20 GHz is explored through a set of power amplifiers as well as transistor level measurements. The power amplifiers explore single versus cascode configuration, smaller versus larger transistor sizes, and the combination of two amplifiers using power splitters/combiners. A maximum output power of 63 mW at 20 GHz was achieved. Transistor-level characterization using load pull measurements on 1-mm gate width transistors yielded 148-mW/mm output power. Transistor modeling and layout for power amplifiers are also discussed. An estimate on the maximum achievable output at 20 GHz from 130-nm CMOS power amplifiers, based on findings in this paper and the literature, is finally presented.

Coupled-mode theory is applied to obtain an analytic form of scattering parameters for a class of transmission line metamaterials with antisymmetric split-rings. The same structure is modeled with equivalent circuit, which includes electric and magnetic coupling with the line and inter-resonator coupling. Modified even/odd analysis is used to obtain scattering parameters from the equivalent circuit. These two methods are shown to be equivalent in a narrow band, and their constants related. The obtained results are compared with full-wave simulations and measurements, and it is shown that both methods give accurate approximation in one octave frequency band. The derived analytic expressions are suitable for study of resonant phenomena, with potential practical applications for filters, phase shifters, delay lines, and sensors.

A new class of 3-dB impedance transforming directional couplers has been proposed in which the recently published coupled-line couplers, consisting of coupled-line sections having different electrical lengths, have been utilized. The main advantage of the proposed directional couplers is the possibility of obtaining high impedance transformation ratio, thus the known limiting condition of realizable impedance transformation in 3-dB couplers is overcome. Moreover, the proposed directional couplers feature significantly wider operational bandwidths. The theoretical analysis of the proposed impedance-transforming directional couplers has been shown and is fully supported by the measurements of the manufactured model operating in 0.5–1.5 GHz frequency range.

A linearly polarized dual band reflectarray (RA) antenna designed, fabricated, and tested to operate in the Ku and K band frequencies is reported in this paper. The 24 × 24 cm2 size RA is developed using 1058 integrated elements etched over a 0.275 mm thick Rogers RT5870 substrate. The integrated elements include concentric circular rings distributed co-centric with the source and the Malta cross elements distributed offset from the source. The distribution of these elements is done based on the 590 and 360° phase change observed at 14.25 (Ku) and 22.5 (K) GHz by varying the size of the circular rings and the Malta cross respectively. The designed RA offers a simulated gain of 28.62 dBi at 14.25 GHz and 26.92 dBi at 22.5 GHz. These results are validated experimentally using the fabricated prototype. A measured peak gain of 28 and 26.4 dBi are observed with sidelobe levels (SLL) of −21 and −11 dB at 14.25 and 22.5 GHz respectively. The cross-polarization levels measured at the resonant frequencies are <−31 and <−28 dB. The proposed dual-band RA covers the entire Ku band uplink frequencies utilized for fixed satellite services and the K band downlink frequencies useful for earth exploration satellite services.