Thin-film Microstrip Research Articles

Complex dielectric permittivity extraction based on multilayer thin film microstrip lines

This study presents an analytical method for the extraction of the complex relative permittivity of multi-layered dielectric substrates that are used to construct thin film microstrip lines (TFMLs). The proposed approach is based on the analysis of an equivalent parallel plate waveguide filled with a dielectric material whose relative dielectric permittivity is the effective dielectric permittivity of the corresponding TFML. The extraction technique relies only on the knowledge of the complex propagation constant obtained from S -parameter measurements and is applicable to a wide range of line dimensions and dielectric permittivity values. For experimental verification, several TFMLs were fabricated, and from the measured scattering parameters, the complex dielectric characteristics of each device are extracted. The extracted relative permittivity and loss tangent values are then compared with the dielectric parameters obtained from a numerical technique based on full wave analyses. The accuracy of the proposed analytical method is shown to be approximately 15 and 5% for the fabricated TFMLs with ratios of the microstrip line width ( W ) to dielectric thickness ( H ), ( W / H ) of 4 and 80, respectively.

Microwave-Based Microfluidic Sensor for Non-Destructive and Quantitative Glucose Monitoring in Aqueous Solution.

This paper presents a reliable microwave and microfluidic miniature sensor dedicated to the measurement of glucose concentration in aqueous solution. The device; which is integrated with microtechnologies; is made of a bandstop filter implemented in a thin film microstrip technology combined with a fluidic microchannel. Glucose aqueous solutions have been characterized for concentration ranging from 80 g/L down to 0.3 g/L and are identified with the normalized insertion loss at optimal frequency. The sensitivity of the sensor has consequently been estimated at 7.6 × 10−3 dB/(g/L); together with the experimental uncertainty; the resolution of the sensor comes to 0.4 g/L. These results demonstrate the potentialities of such a sensor for the quantitative analysis of glucose in aqueous solution.

Inverse class‐FX‐band SiGe HBT power amplifier with 44% PAE and 24.5 dBm peak output power

ABSTRACTAn X‐band power amplifier (PA) implemented in a silicon‐germanium (SiGe) heterojunction bipolar transistor technology is presented. The SiGe PA was designed for inverse class‐F mode using thin‐film microstrip (TFMS) lines, eliminating the use of conventional band‐limiting lumped inductors and transformers. Thus, simultaneous high efficiency and minimized in‐band variation were achieved for X‐band (8–12 GHz) applications. In addition, for boosting peak output power (Pout), the common‐base transistor in the PA core was designed to operate in a weak avalanche region, which allowed dynamic collector‐to‐base voltage to swing beyond the collector‐base breakdown voltage with open emitter without performance degradation. The fabricated SiGe PA demonstrates a high power‐added efficiency (PAE) of 43.2% and a peak Pout of 24.3 dBm at 10 GHz. Benefitting from the utilization of TFMS lines, the PA exhibits a flat response for both PAE (33.3–44%) and peak Pout (23.1–24.5 dBm) for the entire X‐band frequency range. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2868–2871, 2016

Heterogeneous Packaging of Organic Electro-Optic Modulators With RF Substrates

As organic-based electro-optic (EO) modulators continually improve toward meeting the high performance required by new and developing photonic technologies, the challenge of compact and low loss packaging needs to be addressed.Because organic-based EO modulators and RF circuitry are traditionally built on different substrates homogeneous integration would require developing new designs and fabrication processes. In addition, the organic-based EO modulators most often implement microstrip transmission lines for optimal poling and modulation field overlap meaning the ground plane is encapsulated and unavailable for direct contact. In this letter, a heterogeneous RF packaging scheme featuring a wire bond transition between a ceramic feed coplanar waveguide and a thin-film polymer microstrip is presented. The transition introduces less than 1 dB of RF loss at 50 GHz and was demonstrated on an organic-based EO phase modulator which generated optical sidebands out to 40 GHz.

A millimeter-wave CMOS power amplifier design using high-Q slow-wave transmission lines

A three-stage 60-GHz power amplifier (PA) has been implemented in a 65 nm Complementary Metal Oxide Semiconductor (CMOS) technology. High-quality-factor slow-wave coplanar waveguides (S-CPW) were used for input, output and inter-stage matching networks to improve the performance. Being biased for Class-A operation, the PA exhibits a measured power gain G of 18.3 dB at the working frequency, with a 3-dB bandwidth of 8.5 GHz. The measured 1-dB output compression point (OCP1dB) and the maximum saturated output power Psat are 12 dBm and 14.2 dBm, respectively, with a DC power consumption of 156 mW under 1.2 V voltage supply. The measured peak power added efficiency PAE is 16%. The die area is 0.52 mm2 (875 × 600 μm2) including all the pads, whereas the effective area is only 0.24 mm2. In addition, the performance improvement of the PA in terms of G, OCP1dB, Psat, PAE and the figure of merit using S-CPW instead of thin film microstrip have been demonstrated. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2015.

Suppression of Parasitic Substrate Modes in Multilayer Integrated Circuits

Integrated circuits (ICs) with multilayer backend process and a large front-side ground plane support the propagation of parasitic substrate modes. These modes resonate at frequencies that typically are within the bandwidth of circuits operating close to and in the submillimeter-wave range, i.e., beyond 300 GHz. The resonances cause unwanted coupling and feedback, which result in circuit instability and degraded performance for circuits operating in the range of these resonances. A common method to suppress these modes from propagating is to use numerous through-wafer vias distributed over the entire circuit. In this letter, we present a study of substrate modes in multilayer ICs with thin-film microstrip interconnects at 125–330 GHz. We show that a doped Si carrier underneath the circuit effectively eliminates the effect of substrate modes on the circuit functionality. This method requires no backside processed through-wafer vias and no backside metallization.

Basic Study on RF Characteristics of Thin-Film Transmission Line Employing ML/CPW Composite Structure on Silicon Substrate and Its Application to a Highly Miniaturized Impedance Transformer

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated on a silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the device with the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited a shorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. When the TFTL with the proposed structure was fabricated to have a length of <TEX>${\lambda}/8$</TEX>, it showed a loss of less than 1.12 dB at up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant, <TEX>${\beta}$</TEX>, and the effective permittivity, <TEX>${\varepsilon}_{eff}$</TEX>, to have values higher than those of a device with only a conventional coplanar waveguide and a thin film microstrip line. The TFTL with the proposed structure showed a <TEX>${\beta}$</TEX> of 0.53~2.96 rad/mm and an <TEX>${\varepsilon}_{eff}$</TEX> of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricated on a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricated using a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RF performance for broadband.

InP DHBT Amplifier Modules Operating Between 150–300 GHz Using Membrane Technology

In this paper, we present WR05 (140–220 GHz) and WR03 (220–325 GHz) five-stage amplifier modules with novel membrane microstrip-to-waveguide transitions. The modules use a 250-nm InP double heterojunction bipolar transistor (DHBT) technology and multilayer thin-film microstrip transmission lines. The waveguide transitions use $E$ -plane probes on 3- $\mu$ m-thin GaAs membrane substrate. Beam lead connectors integrated on the transition eliminate the need of highly reactive bond wires. In addition, process steps such as backside metallization, backside vias, and nonrectangular dicing of the integrated circuits (ICs) are not required. The WR05 amplifier module demonstrates a peak gain of 24 dB at 245 GHz and more than 10-dB gain from 155 to 270 GHz. The WR-03 module has 19-dB gain from 230 to 254 GHz with input and output return loss better than 10 dB from 225 to 330 GHz. The two modules were also characterized in terms of noise. The minimum noise figures were measured to 9.7 dB at 195 GHz and 10.8 dB at 240 GHz for the WR05 and WR03 modules, respectively. To the authors' best knowledge, these are the first published results on an InP DHBT amplifier modules operating at these high frequencies. It is also the first time that membrane technology is used for IC packaging, regardless of IC technology.

Metal Layer Losses in Thin-Film Microstrip on LTCC

Thin-film microstrip transmission lines fabricated using a Ti adhesion layer followed by layered Cu, Pt, and Au films are measured to determine tradeoffs between manufacturability issues and microwave performance. Since Ti metal has approximately 25 times the resistance of Cu, and currents in a microstrip line flow mainly at the interface with the substrate where the Ti is located, there is the possibility of increased RF signal losses with this structure. It is found that Ti adhesion layers of ≤200-nm thickness cause minimal loss through 40 GHz on DuPont 9K7 low-temperature cofired ceramic substrates, so there is no significant electrical penalty for employing a metal stackup optimized for mechanical durability. These measurements, together with analysis and simulations suggest this will hold in general as long as the thinner, higher resistance adhesion metal is well below one skin depth in thickness at the operating frequency.

220-GHz High-Efficiency InP HBT Power Amplifiers

This paper reports on two power amplifier (PA) monolithic microwave integrated circuits (MMICs) operating at frequencies around 220 GHz. The PAs use 250-nm InP HBTs and thin-film microstrip technology formed with a benzocyclobutene dielectric. Both PAs utilize a two-emitter-finger HBT unit-cell with each finger having an emitter area of 0.25×6 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The single-stage amplifier MMIC has six two-emitter HBTs in parallel for a total emitter area of 18 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This amplifier has ~ 5 dB of small-signal gain from 210 to 230 GHz. It has demonstrated saturated output power of 90 mW at 210 and power-added efficiency (PAE) of 10%. This is the highest PAE number demonstrated at these frequencies. The two-stage PA uses three single-stage PAs, one as a driver and two in a balanced configuration in the second stage. The total output emitter area is 18 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This PA demonstrated saturated output > 100 mW and PAE ≥ 4% from 210 to 225 GHz.

Superconductor-Insulator-Superconductor Mixers for the 2 mm Band (129-174 GHz)

We present the design, construction and performance of backshort-tuned Single Side Band (SSB) and of fixed-tuned Double Side Band (DSB) Superconductor-Insulator-Superconductor (SIS) mixers covering the frequency range of 129-174 GHz (2 mm band). Receivers employing these SSB mixers have been continuously operated for astronomical observations on the six antennas of the IRAM Plateau de Bure Intereferometer (PdBI) since 2007 and on the IRAM 30 m Pico Veleta (PV) radio telescope since 2009. The DSB version of the mixer was employed in a prototype of a four-element focal plane array that was tested on the IRAM 30 m radio telescope. Both SSB and DSB mixers employ the same chip and are based on a wideband single ended probe transition from WR6 full-height waveguide to thin-film microstrip line and on a series array of two Nb/Al-AlOx/Nb junctions. The measured receiver noise for the four-element DSB mixer array pumped by a Gunn oscillator cascaded with a frequency doubler was in the range 25-35 K across the 135-168 GHz LO band. The PdBI and PV receivers equipped with the SSB mixers have measured noise temperatures in the range of 30 K to 60 K and an image sideband rejection below -10 dB over the 129-174 GHz RF band. The measurement results agree well with the predictions obtained through detailed simulations of the SIS receivers based on the standard theory of quantum mixing.

50-Gb/s Direct Conversion QPSK Modulator and Demodulator MMICs for Terahertz Communications at 300 GHz

We demonstrate direct quadrature modulator and demodulator monolithic microwave integrated circuits for future terahertz communications at 300 GHz based on the quadrature phase-shift keying (QPSK) modulation format. For the modulating and demodulating signal, we employed half-Gilbert cell mixers, which provide balanced signaling and moderate performance in conversion efficiency with a simple circuit configuration. In order to maintain the balance performance of the modulator and demodulator, passive baluns and couplers are implemented with thin-film microstrip lines, which exhibit less insertion loss than inverted microstrip lines (IMSLs), while the active mixers are based on IMSLs for short interconnections. The half-Gilbert-cell mixers have a wide enough operation bandwidth for high-throughput communications of more than 10% at 300 GHz. According to the static constellation of the modulator, imbalance is expected to be less than approximately ±0.6 dB ∠4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . A nonchip back-to-back experiment was conducted at up to 60 Gb/s, and 50-Gb/s operation was verified with a low bit error rate on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> or less. The results demonstrate that the QPSK modulation scheme can be applied to double the data rate at terahertz frequencies.

A Short Wavelength and Low Loss Thin-Film Transmission Line Employing ML/CPW Composite Structure on Silicon Substrate

In this work, a thin-film transmission line (TFTL) employing microstrip line/coplanar waveguide (ML/CPW) on silicon substrate was proposed, and its RF characteristics were investigated. The TFTL employing ML/CPW composite structure exhibited the wavelength shorter than conventional coplanar waveguide and thin-film microstrip line. Concretely, at 10 GHz, the wavelength of conventional coplanar waveguide and thin film waveguide is 10.35 and 7.83 mm, while the wavelength of the TFTL employing ML/CPW composite structure was 6.26 mm, which was 60.5 % of the conventional coplanar waveguide. The TFTL employing ML/CPW composite structure with a length of λ/8 showed the loss less than 1.12 dB up to 30 GHz, which was lower than conventional coplanar waveguide and thin-film microstrip line. Above results indicates that the TFTL employing ML/CPW composite structure is a promising candidate for application to a miniaturization of RF components on silicon RFIC.

A 35-to-83 GHz Multiconductor-Lines Signal Combiner for High Linear and Wideband Mixer

This letter proposes a broadband and low-loss multiconductor-lines signal combiner in 90 nm CMOS. The signal combiner consists of one broadside-coupled balun, two broadband in-phase power dividers, one edge-coupled balun, and four impedance-transformation lines. By using thin-film microstrip lines to avoid the loss from silicon substrate, the signal combiner has a simulated insertion loss of 8.1 dB and port-to-port isolations better than 42 dB from 35 to 83 GHz. The signal combiner is then integrated into a source-pumped mixer, and a -1±1.5-dB conversion gain and a 13 dBm average input IP3 at a 6.5 mW total dc power are achieved in measurements.

Broadband Complementary Metal-Oxide Semiconductor Interconnection Transmission Line Measurements With Generalized Probe Transition Characterization and Verification of Multiline Thru-Reflect-Line Calibration

This paper presents extraction techniques and measurement results for broadband complementary metal-oxide semiconductor (CMOS) interconnection transmission line (TL) measurements with generalized probe transition characterization and verification of multiline thru-reflect-line (TRL) calibration. Initially, the probe transition is represented by a transmission matrix instead of the conventional shunt/series model, with detailed parameter evaluation procedures using measured data from two lines that are twice in length. Subsequently, an additional long TL that fully exhibits the TL characteristics at low frequencies is characterized, whereas the matrix manipulations with the other two TL measured data are adapted for high-frequency regions to avoid the ill-conditioned problem. Consequently, broadband characterization for CMOS TL is achieved in a cost-effective manner. With an additional reflect test structure, the multiline TRL calibration can be performed as well for verification. The proposed method is examined by thin-film microstrip lines using CMOS 90-nm one-poly/nine-metal technology with measurement frequencies from 2 to 110 GHz.

Fully Integrated ASK Receiver MMIC for Terahertz Communications at 300 GHz

An ASK receiver MMIC operating at 300 GHz for future terahertz communications is presented. In the receiver IC, we fully integrated all necessary components-a receiving dipole antenna, high gain RF amplifier, envelop detector for demodulating ASK signal and output differential data amplifier-in a 1000×2500 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area. A silicon lens was used to compensate for the small gain of the on-chip antenna. To ensure reliable and stable operation, we designed the MMIC with a thin-film microstrip line, which is expected to suppress crosstalk between the on-chip antenna and the RF amplifier through the substrate and silicon lens. The packaged receiver module with the silicon lens is expected to provide approximately 24-dBi beam directivity. Measured RF and baseband bandwidths are around 30 and 15 GHz, respectively, when a single bias of 3.3 V and total current of around 86 mA are applied. With the receiver module, simple wireless data transmission was conducted for up to 24 Gbps in the 300-GHz band. At 12.5 Gbps, error-free data transmission (bit error rate <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> ) over 0.3 m was achieved with the transmission power of - 16-dBm and a 25-dBi transmitting antenna. With -10-dBm transmission power, measured Q-factors of the received eye patterns were larger than 6 for up to 20 Gbps, which implies that the bit error rate will be less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> .

Modeling and simulating the nerve axon as a thin-film microstrip

Since Hodgkin and Huxley described the nerve axon as a cable (H–H model), many efforts have been made to find more approximated transmission line models representing the nerve axon. This paper describes a simple model that represents the nerve axon in two parts: the internodal space as a lossy thin-film microstrip line and the node of Ranvier as an active complex load. The complex load terminating the transmission line is given by the variable impedance of a tunnel diode. First, the internodal space is circuitally analyzed and electromagnetically simulated as a lossy thin-film microstrip line terminated on a complex fixed load. The transmission line circuit theory, the two-port network analysis, and a two-dimensional finite difference time domain method are used for such a task by forcing a strip subatomic metallization. Then, the transfer function of the internodal space, cascaded with the node of Ranvier, is equated to the transfer function of a transmission line section that includes a tunnel diode. This procedure is carried out in order to obtain the diode's variable impedance. The diode was introduced by Nagumo, Arimoto, and Yoshizawa for simulating the nerve axon as an active transmission line. The active transmission line is represented by the FitzHugh simplified H–H model known as the Bonhoeffer–van der Pol model.

273-GHz 2X Subharmonic Up-Conversion Mixer for System-on-Package Applications

In this paper, a 273-GHz 2X subharmonic passive mixer is proposed for system-on-package applications. The mixer is designed and implemented using thin-film microstrip line on a three-layer package platform. The antiparallel-diode-pair-based mixer up-converts the 135-GHz IF input signal to 273 GHz with a 69-GHz local oscillator. The isolation between the IF and RF ports is achieved by a duplexer. The duplexer is composed of two dual-mode bandpass filters with uniform/nonuniform square ring resonators. The mixer is fabricated and measured, and the measured single-sideband conversion loss is 17.7 dB with an output RF of 270 GHz.

Design of broadside-coupled parallel line millimetre-wave filters by standard 0.18-μm complimentary metal oxide semiconductor technology

An equivalent circuit technique is used to design a class of compacted millimetre-wave band-pass filters in the standard 0.18-mu m complimentary metal oxide semiconductor (CMOS) process. Thin film microstrip is fabricated on a lossy silicon substrate to r

Characterisation and application of embedded lumped elements in multilayer advanced thick-film multichip-module technology

This study presents the characterisation and modelling of embedded multilayer and miniaturised lumped element inductors and capacitors in thin-film microstrip (TFMS) configuration with remarkably high performance using cost-effective photoimageable thick film multichip-module (MCM) technology. The proposed miniaturised multi-turn spiral inductors are designed with circular geometry and removal of the ground plane underneath the coil structure to improve the self-resonance frequency (SRF) as well as the quality factor (Q). The circular 2.5 turn spiral inductor has inductance of 3.7 nH, a high SRF of 8.4 GHz, high-quality factor and measures only 0.6×0.7 mm2. Using the high-performance lumped elements, a fully embedded TFMS low-pass filter (LPF) is demonstrated with a remarkably low-passband insertion loss of 0.3 dB, return loss better than 25 dB, wide spurious free stop band attenuation &gt;45 dB and yet highly miniaturised, measuring only 5.4×1.1×0.3 mm3. The measured response characteristics are in excellent agreement with the predicted response. The miniaturised filter is highly suitable for use as a discrete component or as part of the intermediate frequency (IF) section of a compact integrated microwave or millimetre-wave MCM. This represents one of the highest passive component performances ever reported for ceramic-based MCM technology.