AM-PM distortion caused by transistor's signal-dependent input impedance

Rahkonen, Timo; Hietakangas, Simo; Aikio, Janne

doi:10.1109/ecctd.2011.6043830

Cited by 12 publications

(3 citation statements)

References 2 publications

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“…Design of RF amplifiers for ET applications is not trivial as V env tracks the envelope, the gate-source capacitance ( C gs ) of the transistor changes. This is similar to C ds mentioned above, introducing a mismatch and further AM–PM distortion [20]. This can be compensated for, by tuning the input matching network of the PA.…”

Section: Practical Implementationmentioning

confidence: 76%

An envelope tracking RF power amplifier with capacitive charge pump modulator

Watkins

Mimis

2016

Int. J. Microw. Wireless Technol.

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An envelope tracking (ET) radio frequency (RF) power amplifier (PA) is described intended for handsets and applications where a large number of PAs are needed. Instead of the usual split frequency architecture, a linear tracking charge pump structure is proposed. This allows the supply voltage of an RF PA to increase during the peaks of a high peak-to-average power ratio signal. When combined with an LDMOS RF PA, 42.9% efficiency was achieved at 31.3 dBm output power (POUT) when amplifying a 5 MHz bandwidth 8 dB PAPR 3rd Generation Partnership Project (3GPP) long term evolution signal. The first channel adjacent power ratio (ACPR) without digital pre-distortion was −30.4 dBc, meeting the 3GPP handset emission mask. The ACPR could be improved to −32.5 dBc by adopting a curved envelope shaping function at a reduced efficiency of 38.9%.

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Section: Practical Implementationmentioning

confidence: 76%

An envelope tracking RF power amplifier with capacitive charge pump modulator

Watkins

Mimis

2016

Int. J. Microw. Wireless Technol.

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“…Therefore, when controlling the gate bias, the impact can be observed not only in the gain but also in the varying output phase. The main reason for the transistor nonlinear AMPM behavior is usually the signal-dependent input capacitance that pulls the input matching and causes phase shift at the transistor input [34]. Similarly, varying the PA gate voltage changes the input capacitance and hence has a direct impact on the signal mean phase as well as the nonlinear AMPM.…”

Section: A Experimental Bias-dependent Lut Pa Modelmentioning

confidence: 99%

Combined Sidelobe Reduction and Omnidirectional Linearization of Phased Array by Using Tapered Power Amplifier Biasing and Digital Predistortion

Tervo

Khan

Aikio

et al. 2021

IEEE Trans. Microwave Theory Techn.

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Power amplifier (PA) efficiency and linearity are among the key drivers to reduce energy consumption while enabling high data rates in the fifth-generation (5G) millimeter-wave phased array transmitters. Analog per-branch phase and amplitude control is used to steer the beam, suppress the sidelobes, and form zeros to the desired spatial directions. The amplitude control of individual PA inputs makes nonlinearity vary from antenna to antenna, which challenges the common digital predistortion (DPD) used to linearize the array. In this article, we implement an amplitude control for beamforming by tuning the PA gate bias. Varying the output powers via PA biasing makes the nonlinear characteristics observed at the individual PA outputs similar that helps the array DPD to linearize also individual PAs. The technique is validated by both simulations and measurements. As a measurement platform, we use a 28-GHz phased array transceiver equipped with 64 antenna elements and 16 radio frequency chains. The desired beam shape is synthesized by controlling the per-antenna over-the-air-power with PA gate bias. Then, the system is linearized by training DPD with a reference antenna. The DPD is demonstrated with 100-MHz-wide 5G new radio modulated waveform. The best example case showed −23.5-dB maximum sidelobe level (SLL) with 4.9% error vector magnitude and −40.8-dB total radiated adjacent channel power ratio with DPD. The proposed approach enables simultaneous reduction of beam pattern SLL, achieves good linearity in all directions, and maintains the PA efficiency.

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“…When talking about the reasons of AM-PM distortion (amplitude-dependent phase shift) in amplifiers, two reasons are commonly mentioned. First, some of the circuit capacitance can be non-linear, or the Miller capacitance may appear to be signal-dependent due to compressing gain [5] (Fig. 2).…”

Section: Analysing the Am-pm In A Memoryless Amplifiermentioning

confidence: 99%

A New Interpretation to Groszkowski's Effect

Nokandi

Singh

Pärssinen

et al. 2019

2019 IEEE Nordic Circuits and Systems Conference (NORCAS): NORCHIP and International Symposium of System-on-Chip (SoC)

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This paper presents an alternative interpretation to Groszkowski's effect, which states that the oscillation frequency of a harmonic oscillator is shifted due to the higher harmonic currents flowing into the LC tank. Groszkowki's analysis starts by taking a strictly memoryless amplifier, to which he derives and expression for balance of reactive powers. Then he interprets the frequency shift as a matter of balance of reactive energy in the tank. Here we show that although a conductive amplifier is memoryless, it can still show phase shift at the fundamental tone. This is due to mixing of the fundamental and harmonics in the nonlinear i-v response of the amplifier. Now the new interpretation comes from the oscillation condition: if the amplifier shows phase shift, the tank needs to compensate it, and this causes the shift in the oscillation frequency. The mechanism is explained, analysed symbolically, and verified numerically.

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AM-PM distortion caused by transistor's signal-dependent input impedance

Cited by 12 publications

References 2 publications

An envelope tracking RF power amplifier with capacitive charge pump modulator

An envelope tracking RF power amplifier with capacitive charge pump modulator

Combined Sidelobe Reduction and Omnidirectional Linearization of Phased Array by Using Tapered Power Amplifier Biasing and Digital Predistortion

A New Interpretation to Groszkowski's Effect

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