Masatoshi Nakayama

A microwave miniaturized linearizer using a parallel diode with a bias feed resistance

A miniaturized linearizer using a parallel diode has been developed. It is composed of a parallel diode and a resistance for d.c. bias feed. The linearizer utilizes a nonlinear resistive element of the diode. In this paper, the operation principle of the linearizer is described. The parallel diode provides a high temperature stability and readiness of bias voltage adjustment. BY applying this linearizer to an S-band power amplifier, an improvement of ACP of 5 dB and power added efficiency of 8.5% has been achieved for the /spl pi//4-shift QPSK modulated signal.

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.

Millimeter and submillimeter-wave quasi-optical oscillator with multi-elements

A multi-element oscillator with a quasi-optical resonator is reported. The resonator consists of a Fabry-Perot cavity with a grooved mirror. It has capability for power-combining of solid-state sources in the millimeter-wave region, X-band models consisting of Gunn diodes or GaAs MESFETs are demonstrated. Power-combining and frequency-locking of 18 diodes and six FETs have been successfully observed. A 50-GHz-band Gunn diode oscillator using the resonator is also reported. >

A microwave miniaturized linearizer using a parallel diode

A miniaturized linearizer using a parallel diode has been developed. It is composed of a parallel diode and a resistance for d.c. bias feed. The linearizer utilizes a nonlinear resistive element of the diode. In this paper, the operation principle of the linearizer is described. The parallel diode provides a high temperature stability and readiness of bias voltage adjustment. BY applying this linearizer to an S-band power amplifier, an improvement of ACP of 5 dB and power added efficiency of 8.5% has been achieved for the /spl pi//4-shift QPSK modulated signal.

Impedance matching in active integrated antenna receiver front end design

The active integrated antenna (AIA) concept has been realized in the design of integrated amplifier front end, which enables its applications in novel adaptive antenna systems. To address the problem of mismatch between antenna element and amplifier, we present the matching renditions of both gain impedance and noise figure minimum impedance. In addition, the application of these principles is demonstrated in the design of ultra-compact helical AIA receiver front end for operation at 2.1 GHz. Amplifier simulation and measurements have been carried out to confirm the design procedure. It is shown that the proposed configuration can be successfully used in novel wireless handsets.

Millimeter and submillimeter wave quasi-optical oscillator with multi-elements

A multi-element oscillator with a quasi-optical resonator is reported. The resonator consists of a Fabry-Perot cavity with a grooved mirror. It has capability for power-combining of solid-state sources in the millimeter-wave region, X-band models consisting of Gunn diodes or GaAs MESFETs are demonstrated. Power-combining and frequency-locking of 18 diodes and six FETs have been successfully observed. A 50-GHz-band Gunn diode oscillator using the resonator is also reported.<<ETX>>

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).

Quasi-Optical Resonator Far Millimeter And Submillimeter Wave Solid-State Sources

A new cavity for millimeter and submillimeter wave solid-state oscillators is demonstrated. The resonator consists of a Fabry-Perot resonator with a grooved mirror. It has a capability for power com-bining. Experimental results from X-band models of the resonator are presented. Frequency-locking and power-combining with six Gunn diodes are demonstrated.