Jinsung Choi

A Polar Transmitter With CMOS Programmable Hysteretic-Controlled Hybrid Switching Supply Modulator for Multistandard Applications

This paper presents the realization of a linear polar transmitter supporting multistandard applications. The harmonic-tuned class-AB biased (class-AB/F) power amplifier (PA) with the novel envelope shaping method linearly amplifies the input signal with high efficiency. The hybrid switching supply modulator with programmable hysteretic comparator enables the multimode operation whatever the envelope signal characteristics such as the peak-to-average power ratio and the bandwidth are. The designed polar transmitter is fabricated with CMOS 0.13-mum technology and InGaP/GaAs 2-mum HBT process for the supply modulator and the PA, respectively. For the IEEE 802.16e m-WiMax signal, it shows a power-added efficiency (PAE), an average output power (Pout), and a gain of 34.3%, 23.9 dBm, and 27.9 dB, respectively. Without any predistortion techniques, it satisfies the overall spectrum emission mask specifications. The relative constellation error and the error vector magnitude for the m-WiMax signal are -30.5 dB and 2.98%, respectively. For a WCDMA signal, it presents a PAE, a Pout, and a gain of 46%, 29 dBm, and 27.8 dB, respectively. For the EDGE signal, it delivers a PAE of 45.3% at a Pout of 27.8 dBm with a gain of 29.4 dB. There is about a 7% improvement of the overall PAE for EDGE through the optimum multimode operation.

High efficiency and wideband envelope tracking power amplifier with sweet spot tracking

This paper describes the implementation of a high efficiency and wideband envelope tracking power amplifier with sweet spot tracking. By modulating supply voltage of power amplifier (PA), efficiency can be increased significantly. And linearity is improved by envelope shaping and sweet spot tracking. The supply modulator has a combined structure of a switching amplifier and a linear amplifier to achieve high efficiency as well as wide bandwidth. The measurement results show efficiencies of 36.4/34.1 % for 10/20 MHz long term evolution (LTE) signals with peak to average power ratio (PAPR) of 7.5/7.42 dB.

A

This paper demonstrates a new polar transmitter architecture, which uses the digitized envelope signal to control the drain voltage of a switching mode power amplifier (PA). It is based on a novel polar modulation using the constant envelope modulated signal. Among the various constant envelope modulators, the DeltaSigma modulator is chosen for its noise-shaping characteristic. It enables the use of a highly efficient switching amplifier with high linearity. For demonstration, the overall transmitter is implemented and tested with a code-division multiple-access IS-95A signal. The class-D and class-F amplifiers are designed and compared for the optimum operation. The experimental results show that the amplifier with small device size is suitable for this application because of the fast switching requirement. For the class-F amplifier, the measured power-added efficiency is 51.7% at 22.1 dBm and the overall efficiency (considering the amplified quantization noise) is 31%. The adjacent channel power ratios at 885 kHz and 1.98 MHz are lower than -44.9 and -55.6 dBc at the output power range from 10.8 to 22.1 dBm without any pre-distortion techniques. The overall efficiency is improved to 48.6% with a three-level quantized DeltaSigma modulator. The results clearly show that the highly efficient switching mode PA can be controlled efficiently using a digital signal from the DeltaSigma envelope modulation technique.

\Delta\Sigma

This paper presents an optimized envelope tracking (ET) operation of a Doherty amplifier. Compared to the general ET/envelope elimination and restoration transmitter, it has an advantage of the extended dynamic range of 6 dB for the load modulation of a Doherty amplifier. Moreover, by modulating the supply voltage of the carrier amplifier, while that of the peaking amplifier is fixed, the supply modulator provides just half of the current for the same power amplifier output power. It results in a reduced chip size and the crest factor of the supply modulating signal is reduced by 6 dB, enhancing the efficiency of the supply modulator. The designed ET transmitter consisting of the Doherty amplifier and the supply modulator are fabricated in 2- mum HBT and 0.13-mum CMOS processes, respectively. It presents the efficiency improvement over the broad output power region. Especially at the 16-dB backed-off power level, more than 23% of power-added efficiency (PAE) is achieved. For WiBro application, it shows the PAE of 38.6% at an output power of 24.22 dBm with a gain of 24.62 dB. The error vector magnitude is 3.64%.

-Digitized Polar RF Transmitter

The class-AB/F power amplifier (PA), a multimode PA, which can operate at both class-AB and class-F modes, is analyzed and compared with the conventional class-F and class-AB PAs. The open-circuited third harmonic control circuit enhances the efficiency of the PA without deteriorating the linearity of class-AB mode of the PA. The voltage and current waveforms are simulated to evaluate the appropriate operation for the modes. To demonstrate the multimode PA, the PA is implemented using an InGaP/GaAs HBT process and it is tested with reverse-link IS-95A code division multiple access (CDMA) and PCS1900 global system for mobile communications signals in the personal communications service band. The class-AB operation for a CDMA signal delivers a power-added efficiency (PAE) of 38.9% and an adjacent channel power ratio of 49.5 and 56.5 dBc at the offset of 1.25 and 2.25 MHz, respectively, at the output power of 28 dBm. The maximum PAE of 64.7% under the class-F operation is measured at 32.5-dBm output power for a GSM signal. The class-AB/F PA is a good candidate for the multimode PA of next-generation wireless communication systems.

Optimized Envelope Tracking Operation of Doherty Power Amplifier for High Efficiency Over an Extended Dynamic Range

As a wireless handset deals with multiple application standards concurrently, RF transmitters and power amplifiers are required to be more power efficient and reconfigurable. In this paper, we review the recent advances in the design of the power amplifiers and transmitters. Then, the systematic design approaches to improve the performance with the digital baseband signal processing are introduced for the next generation mobile handset.

A Highly Efficient and Linear Class-AB/F Power Amplifier for Multimode Operation

This letter presents the design and experimental results of a 1.8/2.14 GHz dual-band CMOS low-noise amplifier (LNA), which is usable for code division multiple access and wideband code division multiple access applications. To achieve the narrow-band gain and impedance matching at both bands, an extra capacitor in parallel with the Cgs of the main transistor and a harmonic tuned load are switched. Except for the output blocking capacitor and series inductor, all components are integrated on a single-chip. The LNA is designed using a 0.13mum- CMOS process and employs a supply voltage of 1.5 V and dissipates a dc power of 7.5 mW. The measured performances are gains of 14.54 dB and 16.6 dB, and noise figures of 1.75 dB and 1.97 dB at the two frequency bands, respectively. The linearity parameters of and P1dBin are -16dBm and -5.8 dBm at the 1.8 GHz, -14.8 dBm and -5.3 dBm at the 2.14 GHz, respectively.

Power Amplifiers and Transmitters for Next Generation Mobile Handsets

The Doherty power amplifier for mobile WiMAX application is fully integrated in 1.2×1.2 mm2 using a 2-µm InGaP/GaAs HBT process. The direct input power dividing technique is employed on a chip. Broadband input and output matching techniques are used for broadband Doherty operation. A 1.5 times larger peaking amplifier than carrier amplifier is used to have high efficiency for IEEE 802.16e m-WiMAX signal, which has 9.6 dB crest factor and 8.75 MHz bandwidth. The PA with a supply voltage of 3.4V has an EVM of 2.3% and a PAE of 31.5% at an output power of 24.75 dBm and an operating frequency of 2.6 GHz. The PAE of over 30.3% and the output power of over 24.6 dBm with the EVM of lower than 3.15% and the gain variation of 0.2 dB are achieved across 2.5∼2.7 GHz without any assistant technique for linearization.

A Sub-2 dB NF Dual-Band CMOS LNA for CDMA/WCDMA Applications

A wideband envelope tracking power amplifier, which is robust to battery depletion, is introduced. An integrated boost converter keeps a stable operation of the PA supply modulator. Even at the battery depletion from 4.2V to 2.8V, there is no significant degradation of output power and linearity in the power amplifier. Moreover, the efficiency degradation by the additional regulator is minimized for the novel supply modulator architecture proposed in this work. The fabricated 2.535GHz envelope tracking power amplifier presents max/min power-added efficiencies of 32.3/26.2% for 10MHz BW 3GPP LTE standard along the battery voltage from 4.2V to 2.8V.

30.3% PAE HBT Doherty power amplifier for 2.5∼2.7 GHz mobile WiMAX

The input power drive of Doherty power amplifier (PA) is analyzed and a proper input dividing technique without a coupler is introduced. The efficiency and linearity are enhanced by the uneven power drive and proposed output matching circuits. The PA circuit is realized using a 2-µm InGaP/GaAs HBT process and combined using merged lumped-components for Doherty operation. For wireless broadband (WiBro) application, which has 9.54 dB crest factor and 8.75 MHz bandwidth, the PA has EVM of 3% and PAE of 40.2% at an output power of 26 dBm. This data represents that the PA has an excellent efficiency and linearity performance for handset applications, while eliminating the burden of a coupler.