C. Meliani

Publications (23)3.57 Total impact

• Conference Proceeding: RF class-S power amplifiers: State-of-the-art results and potential

  A. Wentzel, C. Meliani, W. Heinrich
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  ABSTRACT: This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaN-HEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band-pass delta-sigma modulation with 1.68 Gbps sampling frequency. The respective efficiency is 34%. We find that these values strongly vary with coding efficiency of the modulation and reach 19 W with 59% for square-wave excitation. In order to clarify the potential of the PA in more detail, the S-class characteristics at power back-off and with varying oversampling ratio are presented as well.
  Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International; 06/2010
• Conference Proceeding: A simplified switch-based GaN HEMT model for RF switch-mode amplifiers

  A. Wentzel, F. Schnieder, C. Meliani, W. Heinrich
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  ABSTRACT: A simplified switch-based model is proposed for GaN-HEMTs, which is suitable for the design of switch-mode-type amplifiers, in both time and frequency domain. The model is validated using a current-mode class-S circuit, for signals up to 5 Gbps. This amplifier structure allows to check two important characteristics of this model: its capabilities to operate as a switch between two digital states and the broadband capabilities. Though much simpler than the conventional nonlinear HEMT models the simplified model shows very good agreement with measurements and excellent stability in time-domain simulations.
  Microwave Integrated Circuits Conference, 2009. EuMIC 2009. European; 10/2009
• Article: True Broadband Technique for On-Chip-Series Connection of TWAs Using Differential Distributed Amplifiers

  C. Meliani, W. Heinrich
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  ABSTRACT: A new technique for series connection of monolithic broadband travelling wave amplifiers (TWAs) is presented, using differential distributed architectures. This technique is intrinsically broadband because no series capacitor is used, it starts operating at dc up to cut-off frequency. With a GaAs heterojunction bipolar transistor monolithic microwave integrated circuit process, two on-chip-series coupled 18 dB gain and 23 GHz cut-off frequency TWAs are realized. Our approach avoids packaging steps and hybrid components. This is a very promising result for monolithic high-gain broadband amplifiers.
  IEEE Microwave and Wireless Components Letters 05/2009; · 1.72 Impact Factor
• Conference Proceeding: Design and Realization of an Output Network for a GaN-HEMT Current-Mode Class-S Power Amplifier at 450MHz

  A. Wentzel, C. Meliani, J. Flucke, E. Ersoy, W. Heinrich
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  ABSTRACT: This paper describes the design and realization of a hybrid lumped output network for a current-mode class-S power amplifier. It consist of a band pass filter, a balun and a broad-band constant current supply. The filter achieves a bandwidth of 300 MHz and 0.5 dB insertion loss. As a demonstrator for the class-S concept, the developed network together with a GaN MMIC switching stage and GaAs Schottky-diodes demonstrates a complete class-S power amplifier for a data rate of 1.8 Gbps for an analog signal frequency of 450 MHz. An output power of 2.7 W at 450 MHz with an efficiency of 19% and a very high power gain of 37 dB has been achieved. This is the first demonstration of class-S operation at these power levels for this frequency range.
  German Microwave Conference, 2009; 04/2009
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: Switch-mode amplifier ICs with over 90% efficiency for Class-S PAs using GaAs-HBTs and GaN-HEMTs

  C. Meliani, J. Flucke, A. Wentzel, J. Wurfl, W. Heinrich, G. Trankle
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  ABSTRACT: This paper reports on design and realization of monolithic switch-mode amplifiers for data rates up to 1.8 Gbps, suitable for Class-S and inverse class-D PA modules. GaN HEMT as well as high-voltage GaAs-HBT technologies are employed and compared. For digital signal transmission without output filtering, the chips achieve efficiencies of more than 90% at an output power of 5.4 W and 6.5 W with PAE values including the on-chip drivers, of 75% and 80% for GaAs-HBT and GaN-HEMT Ics respectively. These high efficiencies values are very promising since such PA chips represent the key building block for future class S systems.
  Microwave Symposium Digest, 2008 IEEE MTT-S International; 07/2008
• Source

  Available from: fbh-berlin.de

  Article: Bandwidth Potential of Cascode HBT-Based TWAs as a Function of Transistor Ratio

  C. Meliani, M. Rudolph, R. Doerner, W. Heinrich
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  ABSTRACT: The bandwidth potential of cascode HBT-based broadband amplifiers following the traveling-wave amplifier (TWA) concept is studied. An approximate expression for the gain of the circuit is derived, which is based on the transistor small-signal model and the artificial transmission-line parameters. In this way, a relation between the HBT cutoff frequencies f_T and f_max and the 3-dB cutoff frequency f_c of the amplifier is obtained. This is very useful for assessing the gain-bandwidth potential of a given HBT technology for cascode-based TWAs. Applying these results, we study the potential of two technologies with different f_max / f_T ratios, an InP technology with f_max / f_T of 120 GHz/190 GHz, and a GaAs technology with f_max / f_T of 170 GHz/36 GHz. The higher influence of /max (compared to f_t) on f_c is quantitatively demonstrated. TWAs in both technologies were realized and measured, and good agreement between measurement and theory is obtained.
  IEEE Transactions on Microwave Theory and Techniques 07/2008; · 1.85 Impact Factor
• Conference Proceeding: High-Frequency Time-Domain Measurement Technique for Class-S Amplifiers

  A. Wentzel, C. Meliani, J. Flucke, W. Heinrich
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  ABSTRACT: This paper introduces a measurement system for time-domain characterization of switch-mode amplifiers, particularly those of class-S type with differential output. GaN HEMTs are measured and achieve PAEs of 84% and 87% at 5 and 9 W output powers, respectively. The measurement technique is unique since it provides a differential load at the output, together with DC supply and a high-impedance output for differential probing using a real-time oscilloscope. This allows accurate and fast characterization of transistors in the switched mode.
  Microwave Conference (GeMIC), 2008 German; 04/2008
• Conference Proceeding: On Band-Pass Delta-Sigma Modulators Suitable for Microwave Class-S Power Amplifiers

  E. Ersoy, C. Meliani, I. Khalil, W. Heinrich
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  ABSTRACT: The design of a Delta-Sigma modulator (DSM) for class-S amplifiers for 2 GHz signals with 8 GS/s sampling rate is presented, with particular focus on the stability condition. The results are supported by experiments using a bit-pattern generator. Furthermore, the statistic occurrence of binary symbols in the bit pattern is investigated and a statistical measure for the stability condition is deduced.
  Microwave Conference (GeMIC), 2008 German; 04/2008
• Conference Proceeding: Hybrid 3 GHz Class-E Amplifier with High-Voltage GaAs-HBT

  J. Flucke, C. Meliani, W. Heinrich
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  ABSTRACT: This paper reports on design methodology and realization of a class¿E power amplifier (PA) at 3 GHz using a flipchip- mounted high-voltage GaAs HBT. The circuit achieves 39 dBm output power and 61 % PAE, corresponding to a collector efficiency as high as 79 %. In addition to the large-signal simulation aspects, we discuss particularly the problem of the practical realization of the circuit, especially avoiding parasitics by the package.
  Microwave Conference (GeMIC), 2008 German; 04/2008
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: Improved design methodology for a 2 GHz class-E hybrid power amplifier using packaged GaN-HEMTs

  J. Flucke, C. Meliani, F. Schnieder, W. Heinrich
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  ABSTRACT: This paper reports on design methodology and realization of a class-E power amplifier (PA) for 2 GHz using a packaged GaN-HEMT. The circuit achieves 36 dBm output power and 57% PAE, with drain efficiency as high as 62%. In addition to the large-signal simulation considerations, we discuss particularly the problem of input matching of the amplifier under class-E operation.
  Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: A Broadband GaN-MMIC power amplifier for L to X Bands

  C. Meliani, R. Behtash, J. Wiirfl, W. Heinrich, G. Trankle
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  ABSTRACT: A broadband GaN monolithic power amplifier covering the L to X bands is presented as is required for various applications in measurement set-ups and multi-band systems. It is based on 8 transistor cells with 4 times 50 mm gate width each following the distributed amplifier concept. The amplifier achieves 10 dB broadband small-signal gain and a 3 dB cut-off frequency of 11 GHz. The circuit delivers between 1.4 and 2.2 W over the bandwidth from 2 GHz up to 10 GHz. At the maximum output power a PAE higher than 20% is achieved.
  Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: A 2.4 GHz GaAs-HBT Class-E MMIC Amplifier with 65% PAE

  C. Meliani, M. Rudolph, P. Kurpas, L. Schmidt, C.N. Rheinfelder, W. Heinrich
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  ABSTRACT: A class-E amplifier in the 2 GHz band is presented. It is realized as a coplanar MMIC using a high-voltage GaAs-HBT process. At 37 dBm output power, a high PAE of 65% with 71% collector efficiency are achieved. The gain of the amplifier in the switch-mode region reaches 11 dB. These are very competitive values for PAE, collector efficiency, and output power and the highest ones using GaAs-HBT technology. The measured data is supported by in-depth circuit simulation results highlighting the special conditions and requirements of switch-mode operation.
  Microwave Symposium, 2007. IEEE/MTT-S International; 07/2007
• Conference Proceeding: A GaAs HBT Low Power 24 GHz Downconverter with On-Chip Local-Oscillator

  C. Meliani, M. Huber, G. Boeck, W. Heinrich
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  ABSTRACT: In this paper, the paper presents a low-power mixer with integrated local oscillator intended for use in a 24 GHz receiver front-end. The chip is realized using HBT GaAs technology. The voltage-controlled oscillator (VCO) provides a tuning range of 18% at a mean frequency of 21 GHz, with a low DC consumption of 21 mW. DC consumption of the mixer part is about 17 mW from a 3 V supply, with a mean gain of 14 dB and a sensitivity of -70 dBm. The MMIC demonstrates interesting potential for low-power RF terminals in the 24 GHz range
  European Microwave Integrated Circuits Conference, 2006. The 1st; 10/2006
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: A 24 GHz Active Antenna in Flip-Chip Technology with Integrated Frontend

  P.K. Talukder, M. Neuner, C. Meliani, F.J. Schmuckle, W. Heinrich
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  ABSTRACT: A novel slot antenna is presented which is realized using flip-chip technology and allows integration of active chips into the antenna. It is compatible with conventional planar assembly methods and exhibits resonant properties that can be used as an input/output filter. Combining 4 antennas one obtains a compact module with beam switching in all lateral directions. For 24 GHz, only 12 mm side length is required. The paper describes antenna design and presents measurement results of a 24 GHz version with integrated transmitter VCO
  Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: 24 GHz Low Power VCOs and Analog Frequency Dividers

  C. Meliani, F. Lenk, W. Heinrich
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  ABSTRACT: 24 GHz VCOs and frequency dividers with very low power consumption are presented. The circuits are realized as GaAs HBT MMICs. They comprise a VCO with high efficiency >17% and 12% tuning range at only 18 mW DC consumption as well as several frequency dividers. In order to minimize power consumption, the latter use the injection-locked frequency-divider (ILFD) concept. Divider ratios of 2 and 4 are realized, power consumption as low as 25 mW for a divider-by-2 is achieved. This demonstrates the capabilities of the analog concept in realizing dividers for mm-wave frequencies at DC consumption levels far below their digital counterparts
  Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
• Source

  Available from: unibo.it

  Conference Proceeding: On-chip GaAs-HBT broadband-coupled high-bitrate modulator driver TWAs

  C. Meliani, M. Rudolph, W. Heinrich
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  ABSTRACT: A technique to connect two broadband GaAs HBT TWAs is presented. It covers the full range from DC to high frequency and is suitable for high bitrate (40 Gb/s) transmission circuits. This behavior is achieved by modifying the response of one TWA so that it compensates the low-frequency losses. This technique is truly broadband because it uses only elements which are directly connected, and thus is not limited at very low frequencies. Each single TWA delivers 8 dB of broadband gain at a 3dB cut-off-frequency of 26 GHz. Using this interconnect technique, a total broadband gain of 14.5 dB is obtained.
  Microwave Conference, 2005 European; 11/2005
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: A 40 Gbps GaAs-HBT distributed amplifier with an over-fT cut-off frequency: analytical and experimental study

  C. Meliani, M. Rudolph, W. Heinrich
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  ABSTRACT: The bandwidth potential of HBT distributed amplifiers following the traveling-wave concept (TWA) is studied. Basic parameters are the transistor characteristics as well as the losses of the artificial transmission lines. As a result, a relation between f_T and f_max of the HBTs and the -3dB cut-off frequency of the amplifier is derived. Based on this, an over-f_T cut-off-frequency TWA is realized with 6 dB broadband gain and 42 GHz f_c using GaAs HBTs with 36 GHz f_T and 170 f_max.
  Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: Low phase noise X-band push-push oscillator with frequency divider

  M. Schott, F. Lenk, C. Meliani, W. Heinrich
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  ABSTRACT: A MMIC Colpitts oscillator in push-push configuration with integrated frequency divider using InGaP/GaAs HBTs is presented. The output is taken from the second harmonic port while the fundamental signal is fed to a frequency divider by two thus providing a reference signal at one quarter of the output frequency. The MMIC VCO reaches state-of-the-art phase-noise performance in X-band down to -120dBc/Hz at 1MHz offset frequency at high output power and a tuning range of 4%.
  Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
• Conference Proceeding: A GaAs-HBT broadband amplifier with near-f_T cut-off frequency for high-bitrate transmission

  C. Meliani, M. Rudolph, J. Hilsenbeck, W. Heinrich
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  ABSTRACT: Not Available
  Microwave Conference, 2004. 34th European; 11/2004
• Source

  Available from: fbh-berlin.de

  Conference Proceeding: A 40 Gbps broadband amplifler for modulator- driver applications using a GaAs HBT technology

  C. Meliani, M. Rudolph, J. Hilsenbeck, W. Heinrich
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  ABSTRACT: Not Available
  Bipolar/BiCMOS Circuits and Technology, 2004. Proceedings of the 2004 Meeting; 10/2004