Masahiro Kiyokawa

Gaussian-beam antenna

An antenna with Gaussian-beam pattern is proposed for applications to quasi-optical techniques, including integration with MMIC in millimeter- and submillimeter-wave regions. A Fabry-Perot resonator consisting of a concave spherical mirror with partially transparent surface and a plane mirror with coupling region is used to transform a guided-wave mode into Gaussian-beam TEM00 q. A Feature of Gasussian-beam pattern is evidenced by experiments at X-band.

Millimeter-wave Gaussian-beam antenna and integration with planar circuits

A quasi-planar antenna, which uses a dielectric loaded Gaussian-beam resonator is developed for 60 GHz. The resonator antenna with a Gaussian distribution of the aperture electric field is formed with a spherical and a plane mirror surfaces, which were fabricated on both sides of a piano-convex fused quartz lens with 20 mm diameter and 1.3 mm thickness. This new antenna features a very low sidelobe level (<-30 dB) and a high radiation efficiency (>90%). Antenna characteristics and integration with a mixer circuit are described.

A new quasi-optical oscillator with Gaussian output beam

An oscillator with a new quasi-optical resonator, called a Gaussian-beam oscillator, is described. The resonator consists of a plane mirror substrate and a concave spherical mirror with a highly reflective, partially transparent region. A high Q factor, obtained by this spherical mirror, results in a low phase noise of the oscillator and the output power is extracted from this region as a Gaussian beam. This oscillator also features an active circuit fabricated behind the resonator. The configuration is suitable for millimeter-wave integrated circuits. Experimental validity is carried out from an X-band prototype.<<ETX>>

Dielectric loaded Gaussian beam oscillator in the 40 GHz band

A 40-GHz Gaussian output-beam oscillator, using a Gaussian-beam open resonator filled with a dielectric, is described. The dielectric resonator has a highly reflective convex spherical surface and a plane mirror surface having a coupling section with an active circuit. The circuit is fabricated using a commercial HEMT chip. The phase noise of -90 dBc/Hz at 100 kHz off carrier is expected. The output power is extracted as a Gaussian beam.<<ETX>>

A novel multistage active frequency multiplier

A new frequency multiplier, consisting in cascaded single-ended frequency doublers, is proposed as a promising constituent for Ka-band signal sources. Impedance matching at each interstage harmonic frequency is performed directly between transistors by means of a single transmission line. This multiplier translates a low-GHz input signal (∼ 0 dBm), with a conversion gain, into an output as a local oscillator, resulting in eliminated drive amplifiers. The validity of this topology is demonstrated by two, and three-stage multipliers to 14.25 GHz and 28.5 GHz, respectively, developed using medium power (H)FETs.

K band Gaussian beam oscillator

A K band Gaussian beam oscillator, with a new quasi-optical resonator, is described. The resonator consists of a plane mirror substrate and a concave spherical mirror with a highly reflective, partially transparent region. A high Q factor, obtained by using this spherical mirror, results in a low phase noise of the oscillator and the output power is extracted from this region as a Gaussian beam. This oscillator also features that an active circuit is fabricated behind the resonator. The configuration is suitable for the integration with MMIC. The phase noise of the 25.5 GHz oscillator is determined to be less than ¿80 dBc/Hz at 100 kHz off carrier.

Design of an 8.5/25.5 GHz active frequency tripler MMIC

The design of an active frequency tripler monolithic microwave integrated circuit (MMIC) for local multipoint communications systems (LMCS) will be described. The x3 multiplier was designed to operate over a 24–27GHz range, or 12% bandwidth, and uses a PHEMT device in common source configuration biased at a class AB quiescent point. Appropriate input and output matching circuits and terminations for undesired harmonics were designed for the multiplier. The circuit was fabricated at a commercial EHF GaAs MMIC foundry with a 0.2 µm low noise AlGaAs/GaAs PHEMT process. The overall chip size is 2.8mm × 1.4mm fabricated on a 100µm thick GaAs substrate. Conversion loss varies between 6dB and 8dB across the 24–27GHz output frequency band. Fundamental, fo, (8–9GHz) suppression is at least 15dB while 2fo (16–18GHz) suppression varies between 10dB and 16dB from the lower to upper edge of the frequency band. Maximum 3rd harmonic output power is about 4dBm with a minimum DC power consumption of 154mW.