Tadashi Takagi

A novel amplitude and phase linearizing technique for microwave power amplifiers

A novel amplitude and phase linearizing technique for microwave power amplifiers has been developed. It employs a series feedback amplifier with a large source inductance as a predistortion linearizer, which provides positive amplitude and negative phase deviations for input power and can compensate for AM-AM and AM-PM distortions of power amplifiers. Applying this technique to a 1.9 GHz MMIC power amplifier for use in the Japanese Personal Handy-Phone System (PHS), an improvement of adjacent channel leakage power (ACP) up to 7 dB has been achieved when it is used for /spl pi//4-shift QPSK signal.<<ETX>>

Second-harmonic reflector type high-gain FET frequency doubler operating in K-band

A high-gain FET frequency doubler with a second-harmonic reflector in the input circuit has been developed. The reflector position which gives maximum multiplication gain depends on line loss. The relation between multiplication gain and the reflector position varies with line loss. A K-band frequency doubler designed on this basis was fabricated, showing a multiplication gain of 6 dB.<<ETX>>

A low phase noise 19 GHz-band VCO using two different frequency resonators

A low phase noise 19 GHz-band VCO is presented in this paper. The VCO has a novel tuning circuit consisting of two resonators which have a different resonant frequency. With these two resonators, the Q factor of the tuning circuit of the VCO is improved, and low phase noise can be achieved. The measurement results of the developed VCO show phase noise from -120 dBc/Hz to -122 dBc/Hz at 1 MHz from the carrier over a 290 MHz tuning bandwidth in the 19 GHz-band. This VCO achieves one of the lowest recorded values of phase noise at K-band.

A Q-band high gain and low noise variable gain amplifier using dual gate HEMTs

A Q-band high gain and low noise Variable Gain Amplifier (VGA) using dual gate AlGaAs/InGaAs pseudomorphic HEMTs has been developed. The dual gate HEMT can be fabricated using the same process as the single gate HEMT with a gate length of 0.15 /spl mu/m. The Q-band VGA consists of a 1-stage low noise amplifier MMIC using a single gate HEMT and a 2-stage VGA MMIC using dual gate HEMTs. The VGA has a gain of more than 20 dB from 41 GHz to 52 GHz. A gain control range of more than 30 dB is obtained in the same frequency range. A minimum noise figure of 1.8 dB with an associated gain of 22 dB is achieved at 43 GHz when biased for a low noise figure. This performance is comparable with the best data ever reported for LNAs at Q-band including both GaAs based HEMTs and InP based HEMTs.

MMIC development for millimeter-wave space application

The latest millimeter-wave monolithic-microwave integrated-circuit (MMIC) developments and technologies at the Mitsubishi Electric Corporation, Kanagawa, Japan, concerning high power amplifiers, low-noise amplifiers and phase shifters have been summarized. It has been shown that high-efficiency, low-noise, and low-loss performance for millimeter-wave space applications can be achieved by employing pseudomorphic high electron-mobility transistor (p-HEMT) MMIC technology. The investigation for gamma-ray irradiation hardness has cleared that millimeter wave p-HEMT MMICs have over a 100 years of life against gamma-ray irradiation in the space environment.

A miniaturized X-band 4-stage LNA designed using a novel layout optimization technique

A novel layout optimization technique has been proposed and adapted to an X-band LNA. The layout pattern of the amplifier has been optimized in only two days by using simple equivalent circuits derived from electromagnetic simulation results. The amplifier has achieved a gain of 35 dB with a noise figure of 1.7 dB. These results have good agreement with simulated results, and the effective chip area is miniaturized to 4.8 mm/sup 2/.

Wideband VCO with triple tuned circuits in C-Ku band

This paper describes a wide-band voltage controlled oscillator (VCO) with the triple oscillation bandwidth and a better flatness of the phase noise in the oscillation bandwidth using triple varactor-tuned circuits. Altering capacitances of varactor diodes connected to every ports of a HBT in the same direction, the oscillation bandwidth of more than 1.5 octaves has been obtained. A fabricated VCO employing the triple-tuned circuits and a GaAs HBT has covered 1.56 octaves bandwidth achieving the phase noise of -114.9 dBc/Hz /spl plusmn/2.9 dB at 1 MHz offset from the carrier and the output power of 3.4dBm /spl plusmn/2 dB in C-Ku band.

Integrated even harmonic type direct conversion receiver for W-CDMA mobile terminals

This paper is the first demonstration of the overall performance of the integrated even harmonic type direct conversion receiver (EH-DCR) with the RAKE receiver. The configuration of the integrated EH-DCR and its evaluation results based on the 3GPP definition are indicated. The RX LTCC module with the SiGe RX-IC, and BiCMOS ABB-IC are developed to achieve high integration of the receiver with filters. The integrated EH-DCR with low second order distortion can achieve high sensitivity and selectivity of the W-CDMA receiver, even with interference due to the transmitting signal. Described evaluation results satisfy the specifications defined by 3GPP. This paper clarifies effectiveness of the integrated EH-DCR for the third generation mobile terminals.

A Ku-band low-loss stripline low-pass filter for LTCC modules with low-impedance lines to obtain plural transmission zeros

A Ku-band low temperature co-fired ceramic (LTCC) multi-layered stripline low-pass filter (LPF) is presented. By employing a low-impedance line as an inductive element in the resonator, plural transmission zeros can be obtained near passband. Therefore, the presented LPF realizes excellent attenuation characteristics despite a small number of resonators. The LPF has extremely low insertion loss and compact dimensions, an especially thin profile, and is suitable for RF-modules. An LPF with dimensions of 0.9 mm/spl times/0.9 mm/spl times/0.4 mm has been fabricated, and measured results show the validity of the proposed structure.

A W-band monolithic low noise AlGaAs/InGaAs pseudomorphic HEMT amplifier mounted on a small hermetically-sealed package with waveguide interface

A W-band monolithic low noise AlGaAs/InGaAs/GaAs pseudomorphic HEMT amplifier mounted on a small hermetically-sealed package has been developed for use in Advanced Microwave Scanning Radiometer. A six-stage amplifier cascading three two-stage MMIC amplifier chips is assembled on a small hermetically-sealed package with waveguide interface and has achieved a noise figure of 4.3 dB with a gain of 28.1 dB at 91 GHz. The overall amplifier measures 12/spl times/32.8/spl times/5.4 mm/sup 3/. This is the first W-band multi-stage monolithic low noise amplifier mounted on a hermetically-sealed package.<<ETX>>