Augmented Hammerstein model for the calibration of six‐port based dual band wireless receivers

Two architectures of concurrent dual‐band six‐port‐based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six‐port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in‐phase (I₁ and I₂) and quadrature (Q₁ and Q₂) components of an RF signal with two frequency components (RF₁ and RF₂). Experimental validations have been performed to verify the performance of the proposed concurrent dual‐band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual‐band RF signal. The single LO based receiver has been tested with a dual‐band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%.     

Design of a 4.2–5.4 GHz differential LC VCO using 0.35 μm SiGe BiCMOS technology for IEEE 802.11a applications

In this paper, a 4.2–5.4 GHz, ?Gm LC voltage controlled oscillator (VCO) for IEEE 802.11a standard is presented. The circuit is designed with AMS 0.35 μm SiGe BiCMOS process that includes high‐speed SiGe Heterojunction Bipolar Transistors (HBTs). According to post‐layout simulation results, phase noise is ?110.7 dBc/Hz at 1 MHz offset from 5.4 GHz carrier frequency and ?113.4 dBc/Hz from 4.2 GHz carrier frequency. A linear, 1200 MHz tuning range is obtained from the simulations, utilizing accumulation‐mode varactors. Phase noise was also found to be relatively low because of taking advantage of differential tuning concept. Output power of the fundamental frequency changes between 4.8 dBm and 5.5 dBm depending on the tuning voltage. Based on the simulation results, the circuit draws 2 mA without buffers and 14.5 mA from 2.5 V supply including buffer circuits leading to a total power dissipation of 36.25 mW. The circuit layout occupies an area of 0.6 mm² on Si substrate, including DC and RF pads. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

A novel CMOS process compatible high performance parallel-stacked RF spiral inductor

In this study, a deep-submicron CMOS process compatible parallel-stacked inductor has been successfully developed. We use the mature CMOS compatible technology and air gap structure to reduce substrate losses and parallel-stacked structure to reduce the resistance, thus can promote the Q factor. Experimental results evidence that by using the parallel-stacked structure, the chip area can be reduced significantly for the issue of continuing reduction of the chip size. Furthermore, the resistance can be reduced by using the parallel-stacked structure and thus results in an obviously improving of the Q at low frequency. The measured peak Q and peak-Q frequency with the parallel metal layer of M8//M7//M6//M5 are 7.06 and 1.8 GHz, thus enhancing its applications for higher frequency RF IC. Therefore, the developed deep-submicron CMOS process compatible parallel-stacked inductor is suitable for CMOS RF integrated circuit applications.     

The effect of a metal PGS on the Q‐factor of spiral inductors for RF and mm‐wave applications in a 28‐nm CMOS technology

In this paper, the effect of a metal patterned ground shield (PGS) on the performance of monolithic inductors is investigated. To this aim, three spiral inductors integrated in a 28‐nm fully depleted (FD) silicon‐on‐insulator (SOI) CMOS technology are analyzed by means of a 3‐D FEM‐based commercial software. The inductors have been designed at different operating frequencies in the RF and mm‐wave ranges to better explore the effect of the PGS. Extensive analysis revealed that the shield is able to improve the quality factor (Q‐factor) only of the inductor operated at the lowest frequency (ie, K‐band). On the contrary, it has a detrimental effect on the Q‐factor of the inductors working at higher frequencies. This is mainly due to induced losses in the PGS itself, which are so high to frustrate the substrate loss reduction. This result gives a different perspective to the adoption of the PGS for CMOS integrated inductors, which is largely recommended to improve inductor performance in the current state of the art.     

Stability investigation for InP DHBT mm‐wave power amplifier

In this article, we discuss stability issues for mm‐wave monolithic integrated power amplifiers using InP double heterojunction bipolar transistor (DHBT) technology targeting E‐band applications at 71–76 GHz and 81–86 GHz. Different stability detection methods based on the classical two‐port K‐Δ_s pair, linear three‐port graphical analysis, system identifications, circuit modal analysis, and normalized determinant function are all reviewed. The corresponding techniques are employed to predict the occurrence of instability at 15 GHz observed during measurements on a fabricated monolithic microwave integrated circuit power amplifier. Experimental results from a redesigned power amplifier with improved stability are presented to confirm that the previously detected oscillation loop is removed using odd‐mode stabilization resistors with the correct choice of values and locations. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 662–674, 2013.     

Matching network design using non‐Foster impedances

Non‐Foster synthesis bypasses the gain‐bandwidth limitations of conventional LC matching and achieves superior broadband performance by employing negative circuit elements, which are realized via negative impedance converters. The idea is to construct a negative‐image model of an antenna, which cancels the antenna's parasitic reactance and transforms its frequency‐dependent radiation resistance to a constant value. Successful implementation of negative‐image modeling requires the realization of stable, low‐loss negative elements. After a discussion of the basic ideas of non‐Foster matching, we present experimental results for broadband, stable, high‐Q, grounded negative capacitance. Next, in the first experimental confirmation of non‐Foster impedance matching for signal reception, we use a floating negative capacitor to cancel a substantial portion of the reactance of a 6‐in. monopole antenna. Over 20–110 MHz, the signal‐to‐noise ratio improved by up to 6 dB as compared to the same antenna with no matching, or to a lossy‐matched blade antenna of twice the size. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Poststress RF‐drifts of dual‐band LC VCO in 0.18‐μm CMOS technology

This article studies the RF‐property of a dual‐band voltage‐controlled oscillator (VCO). The designed circuit consists of a dual‐resonance LC resonator and a Colpitts negative resistance cell. The dual‐resonance LC resonator comprises a series‐tuned LC resonator and a parallel resonant resonator. The proposed VCO has been implemented with the TSMC 0.18 μm 1P6M CMOS technology. The VCO can generate differential signals in the frequency range of 3.0–3.37 GHz and 6.95–7.40 GHz with core power consumption of 10.08 and 10.24 mW at the dc drain‐source bias V_DD of 1.4 V, respectively. The die area of the dual‐band VCO is 0.485 × 0.800 mm². The circuit was operated at V_DD = 3 V for 8 h and significant drift in RF parameters was found. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:243–248, 2014.     

A novel six‐port circuit based on four quadrature hybrids

A novel six‐port circuit is proposed and demonstrated. The circuit is based on four quadrature hybrids. A prototype circuit is fabricated and characterized with microstrip lines. Reflection coefficients for a few loads are measured with the fabricated circuit to evaluate its performance. The results agree with those from an HP8510C network analyzer reasonably well. Using active inductors and varactors, the six‐port circuit is also designed with a 0.13 μm CMOS process. The simulation results show that the operating frequency is tunable from 1 to 6.8 GHz. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

High quality factor copper inductors integrated in deep dry-etched quartz substrates

This paper reports on an inductor fabrication method capable to deliver high quality factor (Q) and high self-resonance frequency (SRF) devices using quartz insulating substrates and thick high-conductivity copper lines. Inductors are key devices in RF circuits that, when fabricated on traditional semiconductor substrates, suffer from poor RF performances due to thin metallization and substrate related losses. Many previous works revealed that RF performances are strongly dependent on the limited metallization thickness and on the conductivity of the substrate. In this paper we demonstrate a new fabrication process to improve the Q factor of spiral inductors by patterning thick high conductive metal layers directly in a dielectric substrate. Moreover, we develop and validate accurate equivalent circuit modeling and parameter extraction for the characterization of the fabricated devices.     

Modeling double‐side printed meander‐line inductors on printed circuit boards

A lumped element model for a double‐side printed meander‐line inductor with closed‐ form expressions for the electrical model parameters L, C, R_l, and R_c is presented. These structures are cheaper than coils and need less area per unit of inductance than single‐side printed meander‐line inductors. The model has been validated with measurements from 30 to 1000 MHz, finding a mean error in the inductance parameter of about 1%. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 105–112, 2003.     

Rotationally symmetric FDTD for wideband performance prediction of TM01 DR filters

The generalized perfectly matched layer (GPML) coupled with rotationally symmetric (RS)‐FDTD method has been utilized to extract the S‐parameters for several probe‐coupled TM₀₁ dielectric resonator (DR) filters to directly obtain the theoretical wideband spurious performance. The computationally efficient (RS)‐FDTD method has also been used to obtain accurate filter parameters for TE₀₁ and TM₀₁ dielectric resonators loaded in cylindrical cavities. The RS‐FDTD method combined with digital filtering and the Matrix Pencil technique are used to analyze the resonant frequencies, inter‐resonator coupling, and external Q values. When perturbation theory is used with RS‐FDTD, accurate values of unloaded Q are obtained. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 259–271, 2002.     

Design and fabrication of the suspended high-Q spiral inductors with X-beams

In this paper, deep sub-micron CMOS process compatible high Q on-chip spiral inductors with air gap structure were designed and fabricated. In the design the electromagnetic solver, SONNET, and the finite element program, ANSYS, were used for electrical-characteristics and maximum mechanical strength, respectively. The copper wires were capped with electroless Ni plating to prevent the copper from oxidizing. A Si₃N₄/SiO₂ X-beam was designed to increase the mechanical strength of the inductor in air gap. The enhancement of maximum mechanical strength of a spiral inductor with X-beams is more than 4,500 times. Among these structures, the measured maximum quality factor (Q) of the suspending inductor and frequency at maximum Q are improved from 5.2 and 1.6 GHz of conventional spiral inductor to 7.3 and 2.1 GHz, respectively.     

Dual‐functional QM SIW cavity integrating two‐element MIMO antenna and second‐order bandpass filter

A quarter‐mode (QM) substrate‐integrated‐waveguide (SIW) cavity is designed as a dual‐functional component. By etching three slots, four sub‐cavities are formed and then two of them with the same size are individually fed by a coaxial port. Three resonating frequencies are excited in the single QM SIW cavity. One of them can radiate cavity energy input by these ports into free space, implying a two‐element multiple‐input‐multiple‐output (MIMO) antenna, whereas the other two can transmit energy from one port to the other port, indicating a second‐order bandpass filter. Moreover, antenna isolation and filter bandwidth can be adjusted to a certain degree. A prototype with the overall size of 0.40λ₀ × 0.40λ₀ × 0.02λ₀ has been fabricated. The integrated bandpass filter demonstrates the measured center frequency of 3.8 GHz and operating bandwidth of 32 MHz while the integrated MIMO antenna exhibits the frequency of 3.4 GHz, bandwidth of 67 MHz, port isolation of 18.0 dB, radiation gain of 4.0 dBi, and envelope correlation coefficient of 0.25.     

Synthesis and design of tunable bandpass filters with constant absolute bandwidth using varactor‐loaded microstrip resonator

This article presents two new types of tunable filters with constant absolute bandwidth using varactor‐loaded microstrip resonators. First, the second‐ and third‐order Butterworth tunable filters are designed based on the parallel coupled‐line J inverters. Second, a fourth‐order Chebyshev tunable filter is designed based on the alternative J/K inverters, in this design, two adjacent resonators are coupled with each other through a short‐circuited transmission line as the K inverter. The proposed two topologies can be easily extended to high‐order tunable filter. Three tunable bandpass filters with J and alternative J/K inverters, respectively, are built with a tuning range from ～1.8 to ～2.3 GHz. The measured second‐order filter has a 3‐dB bandwidth of 160 ± 6 MHz and an insertion loss of 2.4–3.8 dB. The third‐order filter shows a 3‐dB bandwidth of 197 ± 5 MHz and an insertion loss of 3.8–4.8 dB. The fourth‐order filter shows a 3‐dB bandwidth of 440 ± 5 MHz and an insertion loss of 2.1–2.6 dB. For all the designed filters, the measured results are found in excellent agreement with the predicted and simulated results. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:681–689, 2014.     

Accurate model for micromachined microwave planar spiral inductors

An accurate model is presented for micromachined on‐chip spiral inductors, in which the high‐frequency current crowding effects in metal traces are considered by simplified partial element equivalent circuits, and the substrate parasitics are extracted by the parametric modeling method. The model has been confirmed by both measurements and the results from the 3‐dimensional finite element method. This equivalent circuit model enables the prediction and optimization of high‐Q micromachined spiral inductors in gigahertz frequencies. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 229–238, 2003.     

Nonlinear circuit stability under large‐signal pumping: Three‐port μ stability factor versus conversion matrix system identification—application to a millimeter‐wave band MMIC up‐converter

This article presents and discusses a method to determine stability in nonlinear three‐port circuits based on a generalized three‐port μ stability factor applied to linearized S parameters under large‐signal pumping. A comparison with an extension of the conversion matrix–based, system pole–zero identification used to analyze circuit stability is also presented. The relationship between the two techniques has been verified by means of an ideal two‐port nonlinear circuit, and then, it has been applied in the design of a three‐port millimeter‐wave Monolithic Microwave Integrated Circuit (MMIC) up‐converter. The circuit has been fabricated in a commercial GaAs process. On‐wafer measurements showed an average conversion loss about 3.5 dB in a RF bandwidth between 40.4 and 41.5 GHz with local oscillator (LO) frequency fixed at 42.5 GHz. A RF/LO isolation better than 25 dB was measured in the whole band, also showing outstanding intermodulation performance. With the proposed approach, the appearance of spurious oscillations was prevented. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Design of a printed MIMO/diversity monopole antenna for future generation handheld devices

This article presents a printed crescent‐shaped monopole MIMO diversity antenna for wireless communications. The port‐to‐port isolation is increased by introducing an I ‐shaped conductor symmetrically between the two antenna elements and shaping the ground plane. Both the computed and experimental results confirm that the antenna possesses a wide impedance bandwidth of 54.5% across 1.6–2.8 GHz, with a reflection coefficient and mutual coupling better than ?10 and ?14 dB, respectively. By further validating the simulated and the measured radiation and MIMO characteristics including far‐field, gain, envelope correlation and channel capacity loss, the results show that the antenna can offer effective MIMO/diversity operation to alleviate multipath environments. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:348–359, 2014.     

Self‐oscillating mixer using six port power divider

A self‐oscillating mixer (SOM) that uses a six port microstrip power divider is presented in this article. The oscillation and mixing functions are executed using a pair of identical GaAs field effect transistors. The power division and combination of the RF and local oscillator (LO) signals involved in the operation are implemented using the six port network. The RF input port of the proposed SOM is totally isolated from the operation of the LO which is a desirable feature in many applications. The proposed structure can work as a stand‐alone oscillator with a frequency of 4.71 GHz and a power level of 16.1 dBm. When fed with a RF signal, the proposed structure becomes a fully functional SOM exhibiting a conversion gain of 5.2 dBm. The simulation and measurement results of the proposed SOM are presented to validate the design concept. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:269–276, 2015.