Conferences

A Novel Architecture Reduces Uncertainties of the Precision RF and Microwave Switched Attenuator

Scale fidelity or log conformance calibration of high performance spectrum analysers and an increasing demand for linearity verification of power sensors are both strong motivators for reduced uncertainties in attenuation. The achievable performance of a precision RF and microwave switched attenuator is typically compromised by its mismatch, and the source, the load and transmission line mismatch conditions around it. A novel signal levelling and switching architecture has significantly reduced mismatch and its potential impact. This paper presents the new architecture, integrated within a purpose designed RF Reference source and attenuator along with results achieved and quantified benefits at import and export of calibration.

Advancements in Tunability - Applications beyond the Antenna

The increasing complexity and performance requirements of the RF Front End necessitate incorporating means to recover and improve performance for a given air access channel having both fixed and variable environmental parameters. An obvious first application of tunability is the antenna, where decreasing volumetric allowances and the ever present hand and head TRP influences, benefits greatly from real-time, adaptive tuning networks. Scanning beyond antennas, other applications are beginning to benefit tremendously from incorporating methods of real time RF tunability to address challenges such as manufacturing variances, environmental fluctuations, and changing performance needs over a wider range of air access schemes. This paper will provide examples of several of these applications along with the design challenges surrounding each. Examples will include: • real-time amplifier adaptation between constant envelope and complex linear modulation requirements • in-situ tuning on the manufacturing line to compensate for finite production variations • controlled optimization of filter rejection levels

Compact Low Pass Filter with Ultra-Wide Pass and Stopbands Using Stepped Impedance Resonators and Novel Techniques

The design procedure of a compact ultra-wideband (UWB) stepped impedance resonator (SIR) low pass filter (LPF) is presented in this paper. A SIR LPF with 15.5 GHz cut-off frequency miniaturized by meander line technique is designed and it is shown that offsetting the stepped impedance resonators, as well as indenting the tap location greatly improves rejection bandwidth. By cascading multiple filters the passband is increased while maintaining good rejection bandwidth. The proposed filter is simulated in EM software, fabricated, and tested on a high dielectric ceramic. The results show an improved stopband and passband performance compared with similar topologies with a drastic reduction in filter size.

High Current TLP Characterization: An Effective Tool for the Development of Semiconductor Devices and ESD Protection Solutions

The classical Transmission Line Pulse (TLP) system consists of a 50 Ohm high voltage pulse generator, a high speed sampling oscilloscope, a Source Meter Unit (SMU) and a host PC. The typical range of the pulse waveform parameters are: amplitude in the range of up to ±4 kV, output currents up to ±80 A, pulse width in the range of 1 ns up to 1.6 µs, pulse rise time in the range from 100 ps to 50 ns. The transient voltage and currents at the device under test (DUT) are recorded using a high speed sampling oscilloscope with e.g. 12 GHz bandwidth and 40 GS/s sampling rate. Such a measurement system can be used very effectively to investigate transient characteristics of semiconductor devices or circuits in the high voltage and high current time domain, such as: • High current I-V characteristics of devices and circuits in pulsed operation mode: the “TLP-characteristic” • Turn-on/off transient characteristics of the device • Breakdown effects • Charge recovery effects (reverse and forward recovery times of diodes) • Safe Operating Area (SOA) or Wunsch-Bell characteristic • Ruggedness of transistors (RF-LDMOS, DMOS, CMOS, BJT, …) • MOS gate oxide reliability • Packaging and handling ESD (ANSI/ESDA/JEDEC JS-001-2010) • Human-Metal-Model (HMM) and system level ESD (IEC-61000-4-2) This presentation will give an introduction about the basic principle of a high voltage TLP generator and how it can be used effectively for ESD design, general troubleshooting and device characterization. Live demonstrations and measurements of the ESD performance of RF transistors, transient voltage suppressor (TVS) diodes and MMICs will be performed at the HPPI exhibition stand throughout the two-day conference.

Novel infra-red (IR) thermal measurements on GaAs micro-coolers

Electronic devices are shrinking in size and new materials such as gallium nitride (GaN) are being introduced, resulting in higher dissipated power densities. Therefore, new and novel technologies are required to remove the heat and to thermally characterise the devices. A particular example of a device that will require these thermal management technologies is the gallium arsenide (GaAs) planar Gunn diode which is being developed for millimetre-wave and terahertz (THz) frequencies, and in which the dissipated power density will be very high (approximately 106 W/cm2). This paper will review preliminary thermal and electrical characterisation of a GaAs electro-thermal micro-cooler with the aim of its integration with the planar Gunn diodes, thus increasing the efficiency of the latter. The thermal characterisation of these electro-thermo coolers brings its own set of unique measurement problems. A comparative temperature measurement has been developed using infra-red (IR) thermal microscopy and novel micro-particle sensors. The measurement technique will be described in detail and preliminary measurements on simple superlattice electro-thermal GaAs micro-coolers will be presented.

Phase Locking Techniques Adaptable for a Range of RF Microwave Sources

The use of programmable frequency synthesisers enables the flexibility of adapting a pre-made phase-locked loop (PLL) circuit to control a wide range of microwave sources, e.g. voltage controlled oscillators (VCOs), dielectric resonance oscillators (DROs). This flexibility greatly reduces the cost and time of production and maintenance compared to the conventional method of using discrete components (e.g. frequency detector, divider etc.). This paper discusses the methodology for the design and production of a microwave VCO and the phase locking circuit that can be adapted to frequency synthesise the VCO. Hybrid chip and wire technology on an Alumina substrate was used for the VCO and surface-mount technology (SMT) for the phase-locked loop. The computational modelling and design was carried out with AWR Microwave Office. Programming the phase locking circuit enables the output frequency (or frequencies) to be precisely locked within the frequency range of the VCO or multiples of the VCO’s frequency. This serial information is then programmed on a memory chip to enable automated operation when the unit is powered up. Whilst reducing production time and cost, this approach, achieves synthesised frequency sources up to and beyond 20GHz with competitive phase noise (e.g. 100dBc @100kHz offset), suitable for either commercial or military applications.

Using active load pull to realise harmonic efficiency enhancement in MMIC amplifiers

This presentation will outline the importance of including harmonic load pull in the characterisation of transistors and the benefits of integrating measurement – simulation and design in a single environment. The design of a 5-10GHz 0.5W driver stage MMIC demonstrating the methodology will be outlined.