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Author

R. Knoechel

Bio: R. Knoechel is an academic researcher from University of Kiel. The author has contributed to research in topics: Amplifier & Band-pass filter. The author has an hindex of 7, co-authored 35 publications receiving 243 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a miniaturized bandstop filter (BSF) is introduced, which consists of one meander spurline and a pair of capacitively loaded stubs.
Abstract: A miniaturized bandstop filter (BSF) is introduced in this paper. The filter consists of one meander spurline and a pair of capacitively loaded stubs. The meander spurline with low resonant frequency and improved slowwave factor exhibits excellent resonant bandgap characteristics which can be modeled by a longitudinally coupled resonator. The design of the proposed microstrip BSF is presented, and its performance is measured. Measurements show that there is a stopband from 2.3 to 5.6 GHz with S 21 less than –20 dB. The total length of this BSF equals 23 mm.

47 citations

Proceedings ArticleDOI
11 Jun 2006
TL;DR: In this paper, an interesting effect of output power backoff (OPBO) efficiency improvement is presented which is present if 2 power amplifiers utilizing a reactive output Chireix coupling are combined with input power back-off and differential phase adjustment for maximum efficiency peaking.
Abstract: An interesting effect of output power back-off (OPBO) efficiency improvement is presented which is present if 2 power amplifiers (PA) utilizing a reactive output Chireix coupling are combined with input power back-off and differential phase adjustment for maximum efficiency peaking. The capability of significant efficiency improvement at power back-off is demonstrated and validated by means of simulations and measurements. The new design method delivers a power added efficiency (PAE) of 48% at 6dB OPBO and 35% at 10dB OPBO for a 25.7W Si-LDMOS PA at 2.14 GHz for a WCDMA basestation application.

36 citations

Journal ArticleDOI
17 Jan 2005
TL;DR: In this article, an implementation of a digital component separator for a linear amplification using nonlinear components (LINC) system on a field-programmable gate array is presented, which can be easily configured as an image-reject or direct-upconversion architecture for transmission of single or combined multicarrier wireless code-division multiple access (W-CDMA) signals.
Abstract: An implementation of a digital component separator for a linear amplification using nonlinear components (LINC) system on a field-programmable gate array is presented. It employs a flexible upconversion architecture, which can be easily configured as an image-reject or direct-upconversion architecture for transmission of single or combined multicarrier wireless code-division multiple-access (W-CDMA) signals and uses the phase-modulation method. Four direct digital synthesizers are applied as phase modulators, operating first on a low IF carrier varying from 0 to 1/4 of the sampling frequency. The sampling frequency can be chosen up to 32 times (122.88 MHz) the symbol rate of the W-CDMA chip rate of 3.84 Mbit/s. The system allows a flexible frequency assignment and spacing of one or two independent W-CDMA channels. This paper outlines how the envelope and phase information of two combined W-CDMA channels may be pre-calculated in real time. This information may be used for the generation of two phase-modulated signals, which are then supplied to a single LINC transmitter. The achieved performance is demonstrated for single and multicarrier application utilizing direct and/or image-reject upconversion including simulated and experimental data (adjacent channel power ratio, complementary cumulative distribution function, error vector magnitude).

32 citations

Proceedings ArticleDOI
15 Jun 2008
TL;DR: In this article, an analysis of a sequential power amplifier (SPA) in a transmitter with an FPGA-circuit at the input and a directional coupler at the output is presented.
Abstract: This paper presents an analysis of a sequential power amplifier (SPA) in a transmitter with an FPGA-circuit at the input and a directional coupler at the output. The nonlinear combining characteristics of the output coupler are investigated. The coupling strength and the ratio of maximum power of peaking and main amplifier are discussed as design parameters. A switched coupler is examined as the combiner. Due to the sequential transmitter concept the back-off efficiency can be significantly increased. E.g. using conventional class-B amplifiers a 10 dB back-off efficiency of 38% can be achieved. The average power added efficiency of the whole transmitter may be improved by 30% compared to conventional amplifiers. Design tradeoffs, theoretical performance and measurement results of the proposed transmitters are presented.

26 citations

Proceedings ArticleDOI
17 Dec 2007
TL;DR: A novel transmission line (TL) combiner is proposed having the same functionality as a Chireix-combiner with respect to its load impedance and combiner efficiency, but without the need of additional parallel compensating elements to improve the power backoff efficiency in highly efficient outphasing rf power amplifiers.
Abstract: A novel transmission line (TL) combiner is proposed having the same functionality as a Chireix-combiner with respect to its load impedance and combiner efficiency, but without the need of additional parallel compensating elements, which are necessary to improve the power backoff efficiency in highly efficient outphasing rf power amplifiers. Thus the design complexity is reduced and an alternative approach to Chireix-combiners becomes available. A detailed mathematical analysis of this TL- combiner is presented and design equations are derived. Its different physical operation and performance is demonstrated by a design example.

16 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: A taxonomy based on the layered model is presented and an extensive review on mmWave communications to point out the inadequacy of existing work and identify the future work.
Abstract: Millimeter wave (mmWave) communication has raised increasing attentions from both academia and industry due to its exceptional advantages. Compared with existing wireless communication techniques, such as WiFi and 4G, mmWave communications adopt much higher carrier frequencies and thus come with advantages including huge bandwidth, narrow beam, high transmission quality, and strong detection ability. These advantages can well address difficult situations caused by recent popular applications using wireless technologies. For example, mmWave communications can significantly alleviate the skyrocketing traffic demand of wireless communication from video streaming. Meanwhile, mmWave communications have several natural disadvantages, e.g., severe signal attenuation, easily blocked by obstacles, and small coverage, due to its short wavelengths. Hence, the major challenge is how to overcome its shortcomings while fully utilizing its advantages. In this paper, we present a taxonomy based on the layered model and give an extensive review on mmWave communications. Specially, we divide existing efforts into four categories that investigate: physical layer, medium access control (MAC) layer, network layer, and cross layer optimization, respectively. First, we present an overview of some technical details in physical layer. Second, we summarize available literature in MAC layer that pertains to protocols and scheduling schemes. Third, we make an in-depth survey of related research work in network layer, providing brain storming and methodology for enhancing the capacity and coverage of mmWave networks. Fourth, we analyze available research work related to cross layer allocation/optimization for mmWave communications. Fifth, we make a review of mmWave applications to illustrate how mmWave technology can be employed to satisfy other services. At the end of each section described above, we point out the inadequacy of existing work and identify the future work. Sixth, we present some available resources for mmWave communications, including related books about mmWave, commonly used mmWave frequencies, existing protocols based on mmWave, and experimental platforms. Finally, we have a simple summary and point out several promising future research directions.

380 citations

Journal ArticleDOI
TL;DR: In this paper, an improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented.
Abstract: A 90-W peak-power 2.14-GHz improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented. Independent control of the branch amplifiers by two in-phase/quadrature modulators enables optimum outphasing and input power leveling, yielding significant improvements in gain, efficiency, and linearity. In deep-power backoff operation, the outphasing angle of the branch amplifiers is kept constant below a certain power level. This results in class-B operation for the very low output power levels, yielding less reactive loading of the output stages, and therefore, improved efficiency in power backoff operation compared to the classical outphasing amplifiers. Based on these principles, the optimum design parameters and input signal conditioning are discussed. The resulting theoretical maximum achievable average efficiency for W-CDMA signals is presented. Experimental results support the foregoing theory and show high efficiency over a large bandwidth, while meeting the linearity specifications using low-cost low-complexity memoryless pre-distortion. These properties make this amplifier concept an interesting candidate for future multiband base-station implementations.

154 citations

Book
01 Sep 1992

119 citations

Proceedings ArticleDOI
05 Jun 2011
TL;DR: In this paper, a class-E Chireix outphasing power amplifier is presented that enables high efficiency across a wide power back-off range and RF bandwidth, while meeting the ACLR specifications.
Abstract: A class-E Chireix outphasing power amplifier is presented that enables high efficiency across a wide power back-off range and RF bandwidth. In this design the Chireix compensation elements and class-E loading conditions are provided by an asymmetric coupled-line power combiner. The class-E operated GaN HEMT switches are driven by high-speed, high-voltage CMOS drivers, implemented in a standard 65nm process technology. The proposed concept demonstrates 51.6% system average power efficiency and 65.1% average drain efficiency for a 7.5dB PAR WCDMA signal at 1.95GHz, while meeting the ACLR specifications. Moreover, the PA demonstrated more than 60% drain efficiency across a 6dB power back-off range and up to 19W peak power between 1800–2050MHz.

98 citations

Journal ArticleDOI
TL;DR: Operation with 64QAM OFDM modulation signals at 800-MHz bandwidth is reported, with up to 13-dBm output power and more than 17% PAE, without the use of digital predistortion.
Abstract: A review is presented of key power amplifier (PA) performance requirements for millimeter-wave 5G systems, along with a comparison of the potential of different semiconductor technologies for meeting those requirements. Output power, efficiency, and linearity considerations are highlighted, and related to semiconductor material characteristics. Prototype 5G PAs based on silicon technologies are then reviewed, with primary emphasis on CMOS-SOI. Stacked FET PAs based on nMOS and pMOS for 28-GHz operation are presented, along with outphasing and Doherty amplifiers. Peak power-added efficiency (PAE) up to 46% is demonstrated for a two-stack pMOS amplifier with saturation power (Psat) above 19 dBm. PAE at 6 dB backoff above 27% is shown for an nMOS Doherty PA with 22-dBm Psat. Operation with 64QAM OFDM modulation signals at 800-MHz bandwidth is reported, with up to 13-dBm output power and more than 17% PAE, without the use of digital predistortion. Future challenges for PA development are discussed.

84 citations