High power GaN‐HEMT SPDT switches for microwave applications

In this article, the design, fabrication, and on‐wafer test of X‐Band and 2–18 GHz wideband high‐power SPDT MMIC switches in AlGaN/GaN technology are presented. The switches have demonstrated state‐of‐the‐art performance and RF fabrication yield better than 65%. Linear and power measurements for different control voltages have been reported and an explanation of the dependence of the power performances on the control voltage is given. In particular, the X‐band switch exhibits a 0.4 dB compression level at 10 GHz when driven by a 38 dBm input signal. The wideband switch shows a compression level of 1 dB at an input drive higher than 38 dBm across the entire bandwidth. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

A straightforward design technique for narrowband multi‐stage low‐noise amplifiers with I/O conjugate match

Low‐noise amplifier (LNA) designers often struggle to simultaneously satisfy gain, noise, stability, and I/O matching requirements. In this article, a novel design technique, tailored for two‐stage low‐noise amplifiers, is presented. The proposed design method is completely deterministic and exploits inductive source degeneration to obtain a two‐stage LNA featuring perfect input and output match together with low noise figure (NF) and a pre‐determined gain, including stability analysis. A novel flowchart is provided together with the corresponding design chart that contains gain, matching, and stability information, therefore addressing all key figures‐of‐merit of a linear amplifier. The design chart is easily implementable in commercial Electronic Design Automation software, to aid designers in the difficult task of selecting the appropriate source degeneration inductor value. The noise performance, on the other hand, is the best possible since the matching networks are designed to provide the input of the two Field Effect Transistors with the optimum termination for noise. The design method is validated with two separate test vehicles operating respectively at Ka‐band (26.5‐31.5 GHz) and K‐band (20.0‐24.0 GHz). The realized Monolithic Microwave Integrated Circuits exhibit 18 dB gain for both versions, NF of 1.5 and 1.2 dB, respectively for the Ka‐band and K‐band version. Input and output matching are typically better than 12 and 15 dB.     

Experimental performances of 5 GHz harmonic-manipulated highefficiency microwave power amplifiers

The measured performances of 5 GHz single-stage power amplifiers are presented. The amplifying stages were designed using a recently proposed high efficiency design methodology. Improvements in terms of power-added efficiency of 12, 29 and 43% as compared to standard design approaches have been obtained     

Harmonic-loaded microwave power amplifiers: Nonlinear design procedure

A nonlinear design procedure for microwave power amplifiers is presented. The methodology makes use of a complete nonlinear model for the active device and an exact nonlinear analysis method. Suitable harmonic loading conditions for efficient power performance are imposed simultaneously and consistently with the analysis. The procedure is much faster than conventional repeated nonlinear analyses. © 1995 John Wiley & Sons, Inc.     

13-bit GaAs serial-to-parallel converter with compact layout for core-chip applications

Design and characterization of a 13 bit serial-to-parallel converter in GaAs technology for smart antennas are presented. The circuit has been realized with NOR-based super-buffered enhancement/depletion logic, and optimized for a compact layout. The serial-to-parallel converter operates properly well above the 20 kHz design clock frequency.     

A novel impedance pattern for fast noise measurements

Complete noise characterization of an active device implies the extraction of the minimum noise figure (F_min), noise resistance (R_n), and optimum value of the complex input reflection coefficient (Γ_opt). Such quantities can be obtained through a minimum of four noise figure measurements, associated to four different reflection coefficients at the input of the DUT, (Γ_in,k k = 1 · · · 4), forming an "impedance pattern." Measurement redundancy is usually required to reduce overall uncertainty, therefore forcing one to use, for the synthesis of a large number of different terminations, an impedance tuner. This paper introduces a novel four-points input pattern, which becomes an "optimum" trade-off between accuracy and complexity, while avoiding the use of a tuner: a drastic reduction in cost and complexity of the measurement bench therefore results     

RF power performance evaluation of surface channel diamond MESFETs

We experimentally investigate the large-signal radio frequency performances of surface-channel p-type diamond MESFETs fabricated on hydrogenated polycrystalline diamond. The devices under examination have a coplanar layout with two gate fingers, total gate periphery of 100 μm; in DC they exhibit a hole accumulation behavior with threshold voltage V_t ≈ 0-0.5 V and maximum drain current density of 120 mA/mm. The best small-signal radio frequency performances (maximum cutoff or transition frequency f_T and oscillation frequency f_max) were obtained close to the threshold and were of the order of 6 and 15 GHz, respectively. The power radio frequency response was characterized by driving the devices in class A at an operating frequency of 2 GHz and identifying through the active load-pull technique the optimum load for maximum power added efficiency. A power gain in linearity of 8 dB and an output power of approximately 0.2 W/mm with 22% power added efficiency were obtained on the optimum load impedance at a bias point V_DS = −14 V, V_GS = −1 V. To the best of our knowledge, these are the first large signal measurements ever reported for surface MESFET on polycrystalline diamond, and show the potential of such technology for the development of microwave power devices.     

Alternative approach to dynamic I/V characterisation of microwave FETs

A new and simple approach for the measurement of active device dynamic output I/V characteristics is presented. Device characterisation is performed making use of multi-harmonic exciting signal and variable loads at the output port. The measurement bench has been used to characterise a GaAs 1 mm gate periphery PHEMT as a test vehicle. The results, obtained making use of the proposed setup, successfully compare with those obtained via traditional pulsed measurement systems.     

Nonlinear mixed analysis/optimization algorithm for microwave poweramplifier design

A nonlinear mixed analysis/optimization algorithm for the design of microwave power amplifiers is presented. Matching conditions for optimum power and efficiency performance are imposed together with the balancing equations of the nonlinear analysis in a consistent way. The analysis/preoptimization of the power stage requires a computation time comparable to or smaller than a single conventional harmonic balance analysis. The algorithm forms the basis of a design procedure for the fulfilment of design specifications in terms of output power, power-added efficiency, and gain. Comparisons to the results of commercial CAD nonlinear analysis programs are presented     

Compensating for parasitic phase shift in microwave digitally controlled attenuators

Design issues of digitally controlled attenuators are considered: the parasitic phase shift effect, occurring with every change in the attenuator cell state, is highlighted, investigated and corrected. The technique adopted consists of inserting an appropriately sized capacitor in the attenuator cell topology, compensating for the above-mentioned parasitic phase shift. A design equation is inferred and an X-band MMIC 5-bit constant phase digital attenuator is designed as a test vehicle for the proposed approach.