Wolfgang Bosch

High efficiency power amplifier input/output circuit topologies for base station and WLAN applications

The design and measured results of Class-F output and input circuits for high efficiency operation of power amplifiers is presented. With the circuits presented in this paper, drain efficiencies of 85% can be obtained if the 2/sup nd/ and 3/sup rd/ harmonics are controlled. Efficiencies rise to 95% if the 4/sup th/ and 5/sup th/ harmonics are also controlled. A Class-F input circuit proposed to overcome the negative effects on PAE and efficiency caused by input capacitance variation. By shaping the input waveform the Class-F circuit creates a 50% duty cycle which prevents excessive power dissipation on the gate resistance, hence preventing gain and PAE degradation. A 15 W power amplifier designed at 1.8 GHz was fabricated to validate the presented techniques. The amplifier was designed utilising a FCSL (Filtronic Compound Semiconductors Ltd.) pHEMT device with a total gate periphery of 24 mm. With an unmodulated carrier, 16 watts of output power at 76% drain efficiency and 16 dB small-signal gain was obtained. The amplifier delivered 5.2 watts with a PAE of 48% under EDGE modulation.

Design and Multiphysics Analysis of Direct and Cross-Coupled SIW Combline Filters Using Electric and Magnetic Couplings

In this paper, combline substrate integrated waveguide (SIW) filters using electric and magnetic couplings are thoroughly studied. Thus, a negative coupling scheme consisting on an open-ended coplanar probe is proposed and analyzed in detail. Several in-line 3-pole filters at C-band are designed, manufactured and measured showing how the presented approach can be used for implementing direct couplings while enabling an important size reduction and improved spurious-free band compared to conventional magnetic irises. A fully-packaged quasi-elliptic 4-pole filter is also designed at 5.75 GHz showing how the negative coupling structure can be used for introducing transmission zeros by means of cross-couplings between non-adjacent resonators. Finally, average and peak power handling capabilities of these filters have been also analyzed from a multiphysics point of view. Measured results validate the theoretical predictions confirming that combline SIW filters can handle significant levels of continuous and peak power, providing at the same time easy integration, compact size and advanced filtering responses.

Reduction of Aliasing Effects of RF PWM Modulated Signals by Cross Point Estimation

The trend in transmitter systems is to move the digital domain closer toward the antenna using digital modulators and drivers to reduce circuit complexity and to save power. One promising approach is the use of RF pulse width modulation (RF PWM). Unfortunately purely digital discrete time RF PWM suffers from aliasing problems which limit the achievable resolution. For a 40 MHz bandwidth signal at 2.6 GHz carrier frequency for example the achievable signal quality is limited to ~ 43 dBc. This paper describes the root cause of this effect, an error in the determination of the cross points, due to the sampled nature of the signal and proposes a method to compensate for it. It is shown that by interpolating the signal and estimating the cross points the signal quality can be significantly improved. The interpolation is simplified by interpolating the decomposed outphasing signals instead of the full signal. This has the advantage that a constant instead of a phase modulated reference function can be used. It is shown that by simple cross point estimation the signal quality can already be improved to 65 dBc. When either considering a second modulator or when using a delta sigma like noise shaping architecture the signal quality can be further enhanced to 75 dBc.

A silver inkjet printed ferrite NFC antenna

This paper presents a near field communication (NFC) antenna that is printed directly on a ferrite substrate using a silver inkjet printing process. Such a silver inkjet printed ferrite NFC antenna provides a minimum substrate thickness, a good operation on metal objects, and a small assembly effort. The NFC antenna performance is analysed by measurements based on the ISO/IEC standard 10373-6 for proximity identification cards test methods. For this, the antenna is connected to an NFC microchip. Measurements in a non-metal environment show that the ferrite antenna performs equally good a custom-built NFC antenna printed on photo paper substrate, despite additional losses in the ferrite substrate. In a metal environment the ferrite antenna clearly outperforms the photo paper antenna.

A novel 3D packaging concept for RF powered sensor grains

We present a novel three-dimensional (3D) embedded wafer-level ball grid array (eWLB) system in package (SiP) solution for biochips and micro labs. This 3D SiP includes three major components, a complementary metal oxide semiconductor (CMOS)-tunnel magneto resistance (TMR) sensor biochip for magnetic bead-sensing stacked on a radio frequency identification (RFID) microchip and a 13.56 MHz coil antenna for wireless energy and data transfer. The power supply and the serial peripheral interface (SPI) chip interconnections between the CMOS-TMR sensor biochip (slave) and the RFID microchip (master) are implemented with a novel embedded Z-line (EZL) vertical contact technology through the mold compound. The 13.56 MHz antenna is embedded into the fan-out area of the bottom redistribution layer of the eWLB. With this setup we are able to maximize the RFID reading distance and to ensure a displacement to the TMR sensor surface. We achieve an overall volume of the 3D SiP of only 5.6 mm × 3.6 mm × 0.7 mm applying the eWLB technology. Due to the RFID technology the developed 3D SiP does not need any external contacts and cabling. Therefore it can be encapsulated into harsh environments. In addition the top fan-out surface of the eWLB can be used for adhesive bonding to higher level analyzing setups. The results demonstrate that innovative SiP technology using the eWLB technology combined with chip and antenna design allow to realize modern subsystems e.g. for medical applications.

50 watt MMIC power amplifier design for 2 GHz applications

In this paper the design and the measurement of a 2 GHz 50 Watt (CW) MMIC power amplifier (PA) are discussed. The authors believe that this is the most powerful MMIC implementation that has been reported. The amplifier utilizes a class-F combining structure and realized using the company internal 0.5 /spl mu/m GaAs pHEMT power process. The MMIC measure 10/spl times/10 mm/sup 2/ and delivers 50 Watts of CW power at an efficiency greater than 45% over more than 10% bandwidth at a nominal 12 V supply voltage. The amplifier gain is 21 dB throughout the operational band.

Sensor add-on for batteryless UHF RFID tags enabling a low cost IoT infrastructure

The paper presents an antenna transducer prototype at 915MHz for a batteryless ultra high frequency (UHF) radio frequency identification (RFID) transponder (tag) sensor add-on. By using low cost and low maintenance batteryless RFID sensor tags in a home environment, a low cost internet of things (IoT) infrastructure can be provided. The batteryless or rather passive UHF RFID sensor tag is realized by using the tag antenna as the sensing device. The prototyped antenna transducer allows to detect three specific water filling levels in a can to sense for example the filling level of a coffee machine in a smart home environment. The transducer prototype provides a high efficiency of 92%and thus guarantees for the first time a reliable and stable power supply to the passive RFID tag chip at each sensing state.

SDR based RFID reader for passive tag localization using phase difference of arrival techniques

This paper presents a passive radio frequency identification (RFID) reader for a two dimensional localization of tagged objects in the ultra high frequency (UHF) band. The presented prototype is capable of simultaneously estimating the direction and the range of an object. This capability is provided by a single input multiple output (SIMO) antenna configuration in combination with phase difference of arrival (PDOA) techniques. The core of the prototype is a flexible software defined radio (SDR) that allows rapid prototyping and thus a fast system verification. The reader operates at three frequencies that makes the tag localization more robust, especially in multipath environments. The reader verification is shown by measurements in an anechoic chamber. An initial angular accuracy of 3 degrees for the tag direction and 23 cm for the tag range is accomplished in this first stage of the prototype development.

Passive RFID Sensor Tag Concept and Prototype Exploiting a Full Control of Amplitude and Phase of the Tag Signal

This paper presents a passive radio-frequency identification (RFID) sensor transponder (tag) concept that uses the antenna as the sensing device and exploits a full control of amplitude and phase of the tag signal by optimizing the tag antenna impedances in the different sensing states. This optimization is based on a sensor tag efficiency that evaluates the quality of the tag signal in terms of its amplitude for a reliable power transfer toward the passive tag chip and in terms of its phase for a transmission of the sensing states toward the RFID reader. An antenna transducer prototype for an RFID sensor tag is presented that verifies the concept by detecting three different water filling levels. The prototype achieves a high sensor tag efficiency of 92% at 915 MHz. A reliable power transfer to the passive tag chip is ensured by constant power transmission coefficients of about 90% in all three sensing states. In addition, the phase modulation quality is high and thus shows a high robustness for the detection of the sensing states at the reader. Furthermore, reasonably high tag modulation efficiencies are achieved with a minimum of 11% that ensure a reliable tag ID transmission in each sensing state.

A secure miniaturized wireless sensor node for a smart home demonstrator

Recently, the technology of wireless sensor networks (WSNs) experiences a growing use in home automation or advanced industry infrastructure applications. Despite a strong interest of industries in this technology, key issues like miniaturization and security of WSN nodes has not been solved yet. State-of-the-art WSN nodes do not provide credible security nor satisfying configurability and miniaturized implementations. This publication deals with these limitations and presents a WSN node that provides security, configurability, and a miniaturized design. To show the sensor node feasibility, the WSN node is implemented within a smart home demonstrator. Additionally, a miniaturized pre-study WSN node design is presented using the novel embedded wafer level ball grid array (eWLB) packaging technology. Furthermore, an eWLB based WSN node design is proposed that further miniaturize the presented WSN node.