Designing for spectral conformity: Issues in power amplifier design

Baylis, Charles; Wang, Loria; Moldovan, Matthew; Martin, Josh; Miller, Hunter; Cohen, Larry; Graaf, Jean de

doi:10.1109/wdd.2010.5592610

Cited by 9 publications

(4 citation statements)

References 3 publications

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“…6(a)). The pulse amplitude has been shaped with five different windowing functions typically employed in pulse-compressed radar transmitters [32], [36], [39]: rectangular, Tukey, Hanning, triangular, and Blackman. A linear frequency modulation at 0 (no frequency chirp), 10 and 20 MHz has been applied to the pulse to increase the bandwidth (i.e.…”

Section: Resultsmentioning

confidence: 99%

Multilevel Supply-Modulated Chireix Outphasing With Continuous Input Modulation

Cappello

Barton

Florian

et al. 2017

IEEE Trans. Microwave Theory Techn.

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This work presents a dynamic characterization of a multi-level Chireix outphasing (ML-CO) power amplifier (PA) with modulated signals. The ML-CO technique combines the advantages of envelope tracking and outphasing architectures by limiting the supply modulation to discrete levels with an efficient power-DAC modulator and using outphasing for fine amplitude control. We describe an experimental test bench that supplies the required phase-and time-aligned modulated signals for outphasing and supply modulation simultaneously. Pulsed characterization is used to design a multi-level memory-less polynomial DPD. The linearized ML-CO GaN X-band MMIC PA is demonstrated with fixed input drive levels for 9.3-dB PAPR, 1.4-MHz and 11.3-dB PAPR, 10-MHz LTE signals with a 9.7 GHz carrier. For both signals, the average total power consumption is reduced by a factor of two when supply modulation is used. An investigation of control signal generation strategies is presented, including combinations of discrete supply and continuous input modulation. A simple exponential function tracks the optimal efficiency trajectory of the ML-CO PA, enabling overall efficiency improvements within 9 and 27 percentage points. This control strategy is applied to radar pulses with amplitude shaping and frequency chirp, with efficiency improvement of up to 11.8 percentage points compared to constant-supply operation, with 29 dB improvement in spectral confinement.

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Section: Resultsmentioning

confidence: 99%

Multilevel Supply-Modulated Chireix Outphasing With Continuous Input Modulation

Cappello

Barton

Florian

et al. 2017

IEEE Trans. Microwave Theory Techn.

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“…Out-of-band emissions can be generated by a saturated transmit power amplifier [9], [10]. An amplifier is said to be in saturation when it is forced out of its linear region into a non-linear mode near the 1-dB compression point.…”

Section: Ofdm Transmitter Saturationmentioning

confidence: 99%

On intermittent OFDM transmitter saturation and radar system performance

Cordill

Seguin

2014

2014 IEEE International Symposium on Electromagnetic Compatibility (EMC)

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The effects of spectral crowding are becoming acutely problematic as new wireless systems are being deployed in adjacent bands to legacy systems. Current spectrum management practices seek to control and limit persistent out-of-band emissions, but fall short on addressing intermittent emissions. Such intermittent interference can be caused by the occasional saturation of a transmitting power amplifier, resulting in unintended emissions into adjacent bands. Such transmitter saturations are common for the high peak-to-average power waveforms commonly found in OFDM systems. This work seeks to quantify the performance degradation of a notional radar system in the face of intermittent interference falling in the radar's operating bandwidth. The results show a rise in the false alarm rate of the radar system in proportion to the saturation rate of the adjacent band system.

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“…ACPR is an appropriate metric to quantify the spectral spreading for the following reasons: (i) the leakage of power into adjacent channels is precisely the problem that we seek to solve through this real‐time optimisation solution, (ii) the consideration of adjacent‐band power ratio, the same metric with a slightly different name, is recommended by the International Telecommunication Union (ITU) in standard ITU‐R SM.1541 [11] as a significant quantity for assessing unwanted emissions in adjacent bands and (iii) the signal is wideband, so ACPR is the quantity that can be easily measured in a real‐time spectral environment. The spectral spreading results from intermodulation between in‐band frequency components [12, 13]. The allowable adjacent‐channel power is based upon the amount of interfering power that the device in the neighbouring band can tolerate and still operate successfully.…”

Section: Introductionmentioning

confidence: 99%

Direct algorithm for the Pareto load‐pull optimisation of power‐added efficiency and adjacent‐channel power ratio

Fellows¹,

Baylis²,

Martin

et al. 2014

IET Radar, Sonar & Navigation

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Adaptive radar systems will be required to operate in different frequency bands with spectrum requirements that will likely change both in time and with geographic region. A new algorithm is presented that allows direct optimisation of an amplifier's load reflection coefficient to find a Pareto optimum between the power-added efficiency (PAE) and adjacentchannel power ratio. Comparisons of simulation and measurement results are presented. The new algorithm's results compare well with traditionally acquired data and show consistency between the optimum values for PAE that are obtained from different starting points. Measurement comparison is performed with the previous optimisation algorithm reported by the authors, and results show that up to a 50% reduction in the number of measured experimental queries can be obtained. This translates into a significant time savings in reconfiguring a radar transmitter power amplifier.

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Designing for spectral conformity: Issues in power amplifier design

Cited by 9 publications

References 3 publications

Multilevel Supply-Modulated Chireix Outphasing With Continuous Input Modulation

Multilevel Supply-Modulated Chireix Outphasing With Continuous Input Modulation

On intermittent OFDM transmitter saturation and radar system performance

Direct algorithm for the Pareto load‐pull optimisation of power‐added efficiency and adjacent‐channel power ratio

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