M. Joao Rosario

Low cost LTCC filters for a 30GHz satellite system

This paper deals with the improvement on low cost LTCC technology to achieve the specifications of planar filters for a 30GHz Satellite system transmitter. Test structures were fabricated on low cost LTCC technology, presently available for lower frequencies, to characterise its performances up to 40GHz. From this study, guidelines for the design of 30GHz circuits were obtained. Based on these results and their constraints, several solutions for a 30GHz transmitter filter were designed. A comparison between the LTCC filters with active and passive alternative solutions implemented on GaAs monolithic technology is also presented. The feasibility of millimeterwave filters on LTCC with a reasonable yield for mass production is demonstrated.

Monolithic mixers with MESFETs technology to up and down convert between C and V band

In this paper the design of singly balanced mixers to convert C to V hand signals are presented. A step by step design technique is described, based on harmonic balance simulations. The mixer devices are Schottky diodes compatible with a GaAs MESFET technology. The mixer was optimised for minimum conversion losses on the widest possible bandwidth when used as an up or downconverter in order to be used on a large number of applications. The experiments show a minimum conversion losses on the range of 6 to 8 dB for both applications (up and downconverter) and a 3 dB bandwidth larger then 6 GHz.<<ETX>>In this paper the design of singly balanced mixers to convert C to V band signals are presented. A step by step design technique is described, based on harmonic balance simulations. The mixer devices are Schottky diodes compatible with a GaAs MESFET technology. The mixer was optimised for minimum conversion losses on the widest possible bandwidth when used as an up or downconverter in order to be used on a large number of applications. The experiments show a minimum conversion losses on the range of 6 to 8 dB for both applications (up and downconverter) and a 3 dB bandwidth larger then 6 GHz.<<ETX>>

Optimal design of MESFET frequency multipliers

In this paper, a design criterium for optimizing frequency doubler terminations for maximum output power (Pout) and conversion gain (Gc) is proposed. The design technique, based at a first step on linear S parameters, leads to the calculation of the MESFET terminations. Although rather simple, this approximation led to promising results: with this method, the highest output power-conversion gain trade-off ever reported was achieved and, also, the experimental and simulation results agreed closely.

A Wideband CMOS LNA Integrated with Balun and Linear Digital Gain Control

Design and simulation of a wideband monolithic single-ended-input/differential-output low noise amplifier, with active balun and digital gain control integrated on the same die, is described. The digital circuit comprises an internal 6 bit DAC and a 4 bit input logic control, allowing the gain response to have a linear approximation with 16 dynamic levels. The fully integrated circuit was implemented in a 0.35 mum AMS CMOS standard technology and simulated with BSIM3 model The circuit presents a 16 dB dynamic gain variation in a 1.4-1. 7 GHz band (25 dB of maximum differential gain), a phase and transducer gain magnitude errors less than 1.6deg and 0.2 dB, respectively, in a 300 MHz span, a 1.24 dB noise figure at maximum gain, a -23 dBm input-referred 1 dB compression point at maximum gain, a -12 dBm IIP3, 50 Omega input and output match, while drawing less than 7.5 mA from a 1.7 V power supply, including analog and digital system.

Accuracy of the Simulation of V band MMICs Typical Microstrip Elements with CAD Programs

In this paper a comparison of the simulation of MMICs typical microstrip elements, such as transmission lines, open rectangular stubs and radial stubs, with commercial CAD circuit and electromagnetic simulators with on-wafer measurements up to 70GHz, will be presented. Conclusions about the simulators accuracy and corrected models for each element will be presented.

Modelling SMD capacitor for microstrip circuits

Simple models and a parameter extraction technique for low-cost SMD capacitors mounted on microstrip lines are presented. The models are simple networks, easily implemented in currently available microwave CAD (computer-aided design) programs. Their element values are obtained from the results of vector network analyzer measurements on microstrip structures. Therefore, the models include intrinsically mounting discontinuities. The transmission line parameters values are obtained from the first series self-resonance measured for a ground connection, and the RLC parameter values are obtained from parallel resonances measured with series connection.<<ETX>>

High performance monolithic frequency doubler

Using 0.5¿m GaAs MESFET technology, we have implemented a 7.5 to 15GHz monolithic frequency doubler which has a conversion gain of 2dB and a fundamnental signal suppression of 20dB for a 5dBm@7.5GHz input signal. A design criteria established by the authors, that leads to the calculation of the active device termination to optimise the output power (Pout) - conversion gain (Gconv) trade-off was used. To improve the simulations accuracy a non-linear model for the MESFET based on a modification of Tajima model was derived. The measured performances of the circuit demonstrates an excellent agreement with the linear and non-linear simulations and confi.ms the design approach.

A design technique for MESFET mixers based on SPICE program

A design technique for MESFET mixers is described. This technique is based on a mixer analysis program (MIXAN) developed to obtain the value of conversion gain and optimum source and load impedances for any local oscillator power and DC bias. The MIXAN program uses SPICE as a subroutine to determine large-signal current and voltage waveforms. By using MIXAN, it is possible to obtain the operating conditions for maximum conversion gain. The good agreement between experimental and theoretical values for X-band drain and gate mixers proves the validity of the design technique.<<ETX>>A design technique for MESFET mixers is described. This technique is based on a mixer analysis program (MIXAN) developed to obtain the value of conversion gain and optimum source and load impedances for any local oscillator power and DC bias. The MIXAN program uses SPICE as a subroutine to determine large-signal current and voltage waveforms. By using MIXAN, it is possible to obtain the operating conditions for maximum conversion gain. The good agreement between experimental and theoretical values for X-band drain and gate mixers proves the validity of the design technique. >

CMOS Active-Balun Integrated with Low-Noise Amplifier for IEEE 802.11B/G /2.4GHz WLAN Transceiver

This paper describes the design and simulation of an innovative monolithic active balun integrated with low noise amplifier. The single-ended-to-differential signal transformation circuit comprises a differential signal generation circuit, which is able to receive a single-ended signal and generate a pair of signals having a 180deg (differential) relationship phase. The fully integrated circuit, to be used in 802.11b/g WLAN transceivers, is implemented in a 0.35 mum AMS CMOS standard technology. The simulations, optimized to noise performance, minimum differential phase and magnitude error, were performed with BSIM3 model. The complete circuit presents 20.6 dB of differential power gain at 2.4 GHz, a phase and a transducer gain magnitude errors less than 0.2deg and 0.04 dB, respectively, in a 1 GHz span around 2.4 GHz, a 3.7 dB noise figure, a 2 dBm output-referred 1 dB compression point, 50 Omega input and output match, while drawing 11 mA from a 3 V power supply.

An Improved MESFETs Model Including Average Thermal Conditions, Breakdown, Sub-threshold and Gate Diode ON Operation

A large signal model for MESFETs is presented. It uses the Curtice model for the intrinsic MESFET, in order to be compatible with existing CAD programs. To increase the accuracy for high level driving conditions, the operation within drain breakdown region, the gate diode conduction, and the sub-threshold conduction for high VDS values are considered. For parameter extraction, the I(V) characteristics should be measured under the same thermal conditions that occur in experimental circuits. Accordingly, the MESFET is characterized under pulsed conditions, with high or low level equal to the DC bias. A good agreement between experimental and simulation results, not only for the parameter extraction conditions, but also for non-linear circuits such as mixers, were obtained.