Katsuhiko Araki

A compact and low-phase-noise Ka-band pHEMT-based VCO

A low phase-noise Ka-band monolithic voltage-controlled oscillator (VCO) designed using the negative resistance concept is reported. A circuit fabricated using the three-dimensional monolithic microwave integrated circuit technology exhibits a high integration level; its size is a record at just 0.5 mm/sup 2/. On-wafer measurements demonstrate a low phase noise of -102 dBc/Hz at a 1-MHz offset. The VCO delivers an output power of 11.8 dBm at the center frequency of 28.3 GHz. The frequency tuning range is more than 3.8 GHz. Dependence of the circuit performance on the bias conditions is also reported and suggests that an optimum phase-noise characteristic can be achieved when biasing the transistor to optimize its transconductance and noise figure.

A 0.9-2.6 GHz broadband RF front-end for direct conversion transceivers

A broadband radio frequency (RF) front-end for direct conversion transceivers has been developed. The RF front-end consists of a broadband low-noise variable gain amplifier (LNVGA) and broadband quadrature mixers. The LNVGA achieves high linear characteristics by using a feedback circuit and broadband characteristics by not using reactance elements such as inductors or capacitors. The mixer achieves broadband characteristics through the incorporation of a in-phase power divider and a 45-degree power divider. The in-phase power divider achieves broadband characteristics through the addition of a compensation capacitor. The 45-degree power divider achieves broadband phase characteristics through the addition of capacity to increase the resonance point. From 0.9 GHz to 2.6 GHz, the LNVGA shows a noise figure of less than 2.1 dB and a gain of 28 /spl plusmn/ 1.6 dB. The mixer for a demodulator shows an amplitude error of less than 1.6 dB and a phase error of less than 3 degrees. The mixer for a modulator shows an image ratio of less than -30 dBc.

Analysis of balanced active doubler for broad-band operation - the frequency-tuning concept

A comprehensive analysis of an active balanced frequency doubler is described and proposed as a new concept: tuning the center frequency at which the doubler exhibits its highest performance to extend the usable bandwidth of the device. The concept is validated using a fabricated V-band pseudomorphic high electron-mobility transistor frequency doubler. For this device, a substantial improvement in the usable bandwidth (more than double) is achieved, demonstrating that the proposed concept is particularly suitable for the realization of high spectral purity and widely tunable V-band frequency sources.

A study on an onboard Ka-band phased-array-fed imaging reflector antenna

We proposed a new method for reducing the grating lobe level even when the number of radiating elements in the imaging reflector antenna is small. The most significant feature of this method is that the distance between the array plane and the center of subreflector is controlled so as to reduce the generated grating lobes. Using this method the magnification factor M can exceed the usually used value in order to decrease the number of radiating elements. This method is extremely low-cost because no additional components are added, and it does not decrease the reliability. An onboard phased-array-fed imaging reflector antenna was designed for the future Japanese Ka-band broadband satellite communication system by using the proposed method, and its performance met the system requirements.

BEAM FORMING FOR LARGE-SCALE PHASED ARRAY ANTENNAS

For high-data-rate satellite communication systems, the satellite must need high performance onboard equipment. To improve the onboard antenna performance in higher frequency band, the circuits scale of active phased array antennas take a tendency to become large. This paper presents a novel beam forming technique for onboard large-scale active phased array antennas. The proposed technique uses fewer phase control circuits than the conventional technique. The proposed technique is validated by antenna pattern simulations. The design of an onboard large-scale phased-array-fed reflector antenna based on the proposed technique is described for high-data-rate satellite communication systems.

Reduction of intermodulation distortion in active phased array antenna systems using a distortion controller

This paper describes a novel technique to compensate the intermodulation distortion (IM) of high power amplifiers in an active phased array antenna system. This technique uses IM phase control to break the strong association between carrier and IM. This technique can make the radiation patterns of carriers and IMs different on the active phased array antenna system. As a result, carrier power to intermodulation distortion power ratio (C/IM) is increased at the carrier beam direction. This paper shows the experimental result to confirm this technique using 6-element linear array.