Kenichi Horiguchi

High efficiency feed-forward amplifier using RF predistortion linearizer and the modified Doherty amplifier

The prototype model of the high efficiency feed-forward amplifier using RF predistortion linearizer and the modified Doherty amplifier is developed, and the performance of the developed amplifier is examined experimentally. The efficiency of 13.6% with the output power of 45W is achieved under the condition that ACLR (Adjacent Channel Leakage Power Ratio) is -55 dBc in 3 GPP test method at room temperature of +25/spl deg/C. This is the top level performance among the previously reported feed-forward amplifiers for cellular base stations. In concerning with the modified Doherty amplifier, which is the key component to enhance the efficiency of feed-forward amplifier, the design method and its performance is described in detail.

A 1.9 GHz single-chip RF front-end GaAs MMIC with low-distortion cascode FET mixer for personal handy-phone system terminals

This paper describes new single-chip RF front-end GaAs MMIC for 1.9 GHz Japanese PHS handheld terminals. The IC consists of a high power amplifier, a T/R switch, a low noise amplifier, a newly developed low distortion cascode FET mixer and a negative voltage generator for FET gate bias voltage. The IC has high performance as an RF front-end for PHS terminals.This paper describes new single-chip RF front-end GaAs MMIC for 1.9 GHz Japanese PHS handheld terminals. The IC consists of a high power amplifier, a T/R switch, a low noise amplifier, a newly developed low distortion cascode FET mixer and a negative voltage generator for FET gate bias voltage. The IC has high performance as RF front-end for terminals.

Efficiency Enhancement of 250W Doherty Power Amplifiers Using Virtual Open Stub Techniques for UHF-band OFDM Applications

We propose a new efficiency enhancement method of Doherty power amplifiers (PAs) using virtual open stub techniques. In this method, we consider a peak amplifiers output line as a virtual capacitive open stub only seen at low power level. Using this method, we can transform the low power load impedance seen from the carrier amplifier into higher than the impedance of classical Doherty PA (>100ohm). The relations of the load impedance and the length of the virtual open stub are derived analytically. The developed UHF-band 250W 2-way Doherty PA has been achieved a drain efficiency of 42.1% and an intermodulation (IM) distortion of -27.3dBc at an output power of 44.1dBm (10dB output backed-off) under an integrated services digital broadcasting-terrestrial (ISDB-T) OFDM signal. To the best of our knowledge, these results are the highest backed-off efficiency ever reported among the over 40dBm saturation high power Doherty amplifiers

A high efficiency and low Rx-noise three power mode power amplifier for W-CDMA handsets

This paper presents a high efficiency and low Receive-band noise power (Rx-Noise) three power mode power amplifier for W-CDMA handsets. The number of Switches in output matching circuit and bypass circuit are reduced to realize high efficiency in high-power mode operation. A switched feedback circuit is applied to the first-stage amplifier to achieve low Rx-noise performance. While satisfying adjacent channel power ratio (ACLR) of less than -40 dBc under the measurement condition of a 1.95 GHz W-CDMA (R99) modulated signal and a 3.4 V supply voltage, our developed amplifier achieves 28.25 dBm of high output power with power added efficiency (PAE) as high as 40% in the high power mode, 17.0 dBm with 23% of PAE in the middle power mode, and 7.0 dBm with 13% in the low power mode. Good Rx-noise characteristics of -136 dBm/Hz (190 MHz offset) at 28.25 dBm is achieved by using the switching feedback circuit.

Optimization analysis of feedforward power amplifier

The efficiency optimization of a feedforward low distortion power amplifier is presented. Based on the principle of distortion compensation, the main amplifier output power, that of subamplifier, and amplifier efficiency have been accurately derived. In the present analysis, the coupling coefficient of main signal and distortion paths is selected as the optimization parameter because it may essentially affect the amplifier performance. Simulation results have been obtained for different values of signal cancel ratio and adjacent channel leakage power. The analysis contributes to the design improvement of a power amplifier of mobile communication base stations.

Efficiency Enhancement of a Digital Predistortion Doherty Amplifier Transmitter Using a Virtual Open Stub Technique

This paper proposes a design method of a Doherty amplifier, which can determine the most efficient backed-off point of the amplifier by adjusting a load modulation parameter. The parameter is defined through the design of output transmission line of a carrier and a peak amplifier using a virtual open stub technique. This paper describes the design results using the technique to optimize efficiency of a Doherty amplifier for an orthogonal frequency division multiplexing (OFDM) signal, and parameter adjustment for a linearized Doherty amplifier using an adaptive digital predistortion (ADPD). Applying this method, the developed 250W ADPD Doherty amplifier has achieved drain efficiency of 43.4% and intermodulation (IM) distortion of -48.3 dBc with output power of 44.1 dBm (10.1 dB output backed-off) at 563 MHz using an OFDM signal for integrated services digital broadcasting-terrestrial (ISDB-T).

A high-efficiency and high-gain, plastic packaged GaN HEMT for 3.5-GHz-band LTE base stations

A plastic packaged GaN HEMT is presented for 3.5-GHz-band LTE small-cell base-station applications. A pair of GaN HEMT dies and MIM capacitors is assembled in the package for Doherty amplifier use. Optimized drain bonding wire length enhances high efficiency operation. The input prematching with the MIM capacitors suppresses insertion loss and improves power gain. Measurements of a single-chain amplifier using the GaN HEMT show a high drain efficiency of 66.3% and a high power gain of 16.2 dB at 3.5 GHz, regardless of plastic packaging. A Doherty amplifier demonstration with the GaN HEMT shows a drain efficiency as high as 51.2% and an output power of 36.0 dBm at ACLR of -50 dBc. This is the first demonstration of a plastic packaged GaN HEMT Doherty amplifier in the 3.5-GHz band.

A broadband Rx band noise reduction circuit with CMOS switch for multi-band power amplifier

A broadband Rx band noise reduction circuit for multi-band power amplifiers (PA) is presented. The proposed Rx band noise reduction circuit consists of a Single-Pole Double-Throw (SPDT) switch and an LC resonator with resonant frequency is at the difference frequency between transmit and receive bands. By controlling the connection path of the LC resonator with the SPDT switch, the proposed Rx band noise reduction circuit achieves broadband Rx band noise suppression. In this paper, to clarify the impact of the proposed circuit, the proposed circuit is applied to a multi-band PA. As a result, the proposed Rx noise reduction circuit offers broadband out-of-band noise suppression and improved Rx noise power. In addition, the PA achieves more than 28.5 dBm of output power with power added efficiency (PAE) as high as 37% with a corresponding Rx-noise power of -136.5 dBm/Hz.