A Si MMIC compatible ferroelectric varactor shunt switch for microwave applications

This letter describes a ferroelectric thin-film based varactor shunt switch, for microwave and millimeterwave switching applications. Our implementation is based on a coplanar waveguide transmission line shunted by a ferroelectric varactor. The concept of switching ON and OFF is based on the dielectric tunability of the ferroelectric barium strontium titanium oxide (BST) thin-films. From experimental verification, the isolation of a switch with a varactor area of 75/spl mu/m/sup 2/ was approximately 20dB at 35GHz and the insertion loss was below 4.5dB up to 35GHz. This letter addresses the design and experimental verification of the first ferroelectric varactor shunt switch with an Si monolithic microwave integrated circuit compatible process.     

Reliability analysis of MOS varactor in CMOS LC VCO

The paper investigates the reliability of MOS varactor tuned voltage-controlled oscillators (VCO). Due to the stress induced threshold voltage shift of the MOS varactor, the resonant tank degrades and the center frequency and phase noise of VCO deviate. The behavior is modeled and an adaptive body biasing scheme is proposed to make VCO resilient to reliability. In the mean time it does not degrade the VCO performance. An LC VCO at 24 GHz carrier frequency with adaptive body biasing is compared with VCO without such biasing design in PTM 65 nm technology. The ADS simulation results show that the biasing design helps improve the robustness of the VCO in resonant frequency. The design reduces the frequency sensitivity of VCO by 20% when subjected to threshold voltage degradation.     

A novel Schottky/2-DEG diode for millimeter- and submillimeter-wavemultiplier applications

A high-frequency diode is proposed for use as a frequency multiplier element in the millimeter- and submillimeter-wavelength regions. The Schottky/2-DEG diode utilizes a Schottky contact along the edge of a two-dimensional electron gas (2-DEG) structure. This geometry allows one to combine a very low series resistance due to the excellent transport properties of the 2-DEG with a high breakdown voltage caused by the 2-D electric field spreading in the depletion region (compared to a 1-D field variation in the conventional Schottky diode). The higher Fermi velocity of the 2-DEG leads to a less severe transit-time limitation of the frequency response     

Hysteresis prediction in autonomous microwave circuits usingcommercial software: application to a Ku-band MMIC VCO

In this paper, a new method is presented for the simulation of autonomous microwave circuits, using commercial software. The method, especially suitable for voltage-controlled oscillators (VCO's) and phase-locked circuits, allows the simulation of the whole solution curves as a function of any parameter, enabling the prediction of hysteresis phenomena, and thus a realistic determination of the operating bands. Immittance diagrams, providing all of the coexisting oscillating solutions, are traced using commercial software by means of a new technique. As a parameter varies, a switching-parameter continuation method is also used for tracing the possible turning points of the solution curve. The new simulation method has been applied to the design of a Ku-band monolithic microwave integrated circuit (MMIC) VCO. This circuit, which has been integrated using a commercial monolithic technology based on 0.2 μm gate length pseudomorphic HEMT's, constitutes a good example to illustrate the new simulation method capabilities. Frequency tuning and output power control are, respectively, obtained by varying the varactor and transistor voltage bias. On-wafer measurements and simulation results showed excellent agreement     

Quantum barrier varactor for coplanar waveguide applications

A quantum barrier varactor with a GaAs/AlGaAs/GaAs structure embedded in a coplanar waveguide has been fabricated. The configuration in the coplanar waveguide improves frequency-tripler performance by using a harmonic load-pull technique     

A three-terminal SOI gated varactor for RF applications

This paper presents a new CMOS compatible SOI gated varactor for use in RF ICs. With its additional third terminal, the device offers an exceptional large tuning range and a good quality factor. The result of the MEDICI simulation of the structure of the varactor has been confirmed with measured data. A VCO circuit that can potentially exploit the three-terminal property is also reported     

Eliminating threshold losses in MOS circuits by varactor bootstrapping

Threshold losses reduce speed and increase power consumption in MOS digital circuits. A method using a MOS varactor element to eliminate the effects of those losses is described.     

CAD techniques for microwave circuits

In little more than 10 years computer-aided design (CAD) of microwave circuits has moved from dumb terminals on mainframe computers to PCs, and now to powerful RISC workstations. Commercial CAD software now integrates the various stages of microwave circuit design: schematic capture, simulation and layout. This paper reviews the different CAD packages that are available for microwave circuit design. The basic principles employed in the modelling of microstrip circuits are introduced and the reasons for the extensive use of frequency-domain simulations are explored. The developments in nonlinear, electromagnetic and system-level simulation methods are described     

Eliminating threshold losses in MOS circuits by bootstrapping using varactor coupling

Threshold losses reduce speed and increase power consumption of MOS digital circuits. A method to eliminate these losses is described. This is accomplished by the application of bootstrapping, in which a temporarily isolated circuit node is capacitatively coupled to the input voltage. The advantages of a MOS varactor element and its use for the coupling capacitor are described.     

A novel compact electromagnetic-bandgap (EBG) structure and its applications for microwave circuits

A novel electromagnetic-bandgap (EBG) structure in a fork-like shape is investigated. This structure has an extremely compact size. A comparison has been carried out between the new structure and the conventional mushroom-like EBG structure. Simulations and experimental results have verified that the area of the fork-like structure is less than 40% of the latter. The presented structure also provides an additional degree of freedom to adjust the bandgap position, which is applied to design a novel reconfigurable multiband EBG structure. Several application examples have been demonstrated, including a double-element microstrip antenna array with low mutual coupling, notch-type antenna duplexer, and steerable array with a linearly discrete beamsteering of 20/spl deg/ in steps of 10/spl deg/ at 2.468 GHz.     

Statistical computer-aided design for microwave circuits

A useful methodology for microwave circuit design is presented. A statistical technique known as Design of Experiments is used in conjunction with computer-aided design (CAD) tools to obtain simple mathematical expressions for circuit responses. The response models can then be used to quantify response trade-offs, optimize designs, and minimize circuit variations. The use of this methodology puts the designer's intelligence back into design optimization while making “designing for circuit manufacturability” a more systematic and straightforward process. The method improves the design process, circuit performance, and manufacturability. Two design examples are presented in context to the new design methodology     

Practical microwave circuits for groove waveguides

Groove guides have been known for many years. No practical microwave circuits have yet been described although these types of transmission lines could be used in many cases. This paper discusses the physical realizability of some wide band designs such as matched load, directional coupler, hybrid coupler, bend and phase shifter. Both closed and open groove guides have been investigated. Optical type components seem to be inappropriate for groove guide transmission. The best way to design components for these guides is to adapt those of standard rectangular guides, which perturb only the Rf fields in the vicinity of the narrow walls and to optimize the dimensions of the groove structure as a function of the losses and the symmetry of the induced spurious modes.     

GaAs HBT's for microwave integrated circuits

The status of the microwave GaAs heterojunction bipolar transistor (HBT) technology is reviewed. Microwave circuits for advanced military and commercial systems continue to increase their dependence on the performance, functionality, and cost of active components fabricated using solid-state technology. The performance advantages provided by GaAs HBT's, for several critical circuit applications, have stimulated a worldwide development activity. Progress in HBT device technology and microwave circuit applications has been extremely rapid because of the broad availability of III-V compound semiconductor epitaxial materials and prior experience with GaAs field-effect transistors (FET's) and monolithic microwave integrated circuits (MMIC's). The great flexibility of HBT's in microwave circuits makes them prime candidates for applications in complex multifunctional microwave/digital IC's in next-generation systems     

Measurement techniques for monolithic microwave integrated circuits

Introduces the basic technologies that are associated with measurements of monolithic microwave integrated circuits. The use of test fixtures and wafer probe stations at ambient room temperature is reviewed and their role at thermal and cryogenic temperatures is discussed. With the increasing need for performing non-invasive measurements, advances in experimental field probing techniques are explored     

Uniplanar techniques for monolithic microwave integrated circuits

`Uniplanar' techniques have recently been introduced for the design of monolithic microwave integrated circuits (MMICs). The aim of these techniques is to achieve a higher level of integration of circuitry and to overcome the need for through-substrate via holes and the related back-face processing steps. This is achieved by using coplanar waveguide (CPW), slotline, and miniature `thin-film microstrip' transmission-line media as opposed to conventional microstrip. The design and performance of a number of uniplanar MMIC couplers, amplifiers, and other test circuits fabricated using the GEC-Marconi (Caswell) foundry are described     

Hybrid circuits for multioctave multiple-throw microwave switches

Single-pole multiple-throw microwave switches may be designed as extremely broad-band multistate low-pass filters. SPDT switch design using p-i-n diodes and high-impedance transmission line is described. Extension of the technique to multiple-throw switches is outlined. Two operating examples of the method, an 18-GHz bandwidth SPDT and a 12-GHz SP4T, are discussed.     

Modified suspended striplines for microwave integrated circuits

Suspended coupled striplines have very different even- and odd-mode phase velocities. A structure modified by the presence of a slot is proposed to obtain equalisation, a condition necessary to build broadband couplers. This modification has the advantage of preserving the suspended configuration.     

Circulators for microwave and millimeter-wave integrated circuits

The requirements for circulators for use in combination with microwave and millimeter-wave integrated circuits are reviewed, with special emphasis on modules for phased-array antennas. Recent advances in broadbanding and in miniaturization are summarized. Novel types of circulators that are fabricated by attaching a ferrite disc and a suitable coupling structure to the surface of a dielectric of semiconductor substrate (quasimonolithic integration) are described. Methods for achieving complete monolithic integration are also discussed     

Proton implantation isolation for microwave monolithic circuits

We show that proton implantation isolation effectively reduces RF losses for microwave monolithic integrated circuits and that the degree of effectiveness is a function of the induced damage depth. RF losses are mostly due to the current conduction in semiconducting active or buffer layer.