Morikazu Sagawa

Geometrical structures and fundamental characteristics of microwave stepped-impedance resonators

/spl lambda//sub g//4-,/spl lambda//sub g//2-, and /spl lambda//sub g/-type transmission-line stepped-impedance resonators (SIRs) have been proposed and various practical applications have been reported on the basis of the analysis related to each resonator. This paper standardizes these three types of SIRs and systematically summarizes their fundamental characteristics, such as resonance conditions, resonator length, spurious (higher order) responses, and equivalent circuits. Practical applications which employ features of three types of SIRs are investigated with demonstrations of specific structures. Original design formulas with respect to /spl lambda//sub g/-type dual-mode resonators are analytically derived. Advanced SIRs using composite material and multisteps are also introduced and their availability is discussed.

Miniaturized hairpin resonator filters and their application to receiver front-end MICs

The authors describe the fundamental characteristics of miniaturized hairpin resonators having parallel coupled lines and show their applications to bandpass filters and receiver front-end microwave integrated circuits (MICs). A method for calculating filter coupling parameters using a general-purpose microwave circuit simulator is presented. The bandpass filters have a suitable structure for MICs, and their size is one-half that of conventional hairpin resonators without increasing insertion losses. Trial receiver front-end MICs using these filters have been developed and have shown good characteristics such as low noise and a high image suppression ratio. They are applicable to a frequency range above the L-band. >

Varactor Tuned Bandpass Filters Using Microstrip-Line Ring Resonators

This paper describes the fundamental characteristics and experimental results of newly developed tunable bandpass filters using rnicrostrip-line ring resonators. The experimental filter has a steeper attenuation slope and less circuit instability than conventional filters, and it seems to be a suitable filter for MICs or MMICs.

Stripline dual-mode ring resonators and their application to microwave devices

This paper describes the fundamental properties of two orthogonal resonant modes within stripline ring resonators and their application to microwave devices. There are two principal methods for application of ring resonators, the first is by using two-port devices and the second four-port devices, in the case of two-port configurations, dual-mode filters using coupling between two degenerate modes have been studied as typical applications. In this paper, new methods for the coupling of two modes and their applications to practical devices, are proposed, and then experimental results for proof of the new structures are presented. Four-port configurations, which make use of two resonant modes as being independent or having no coupling between them, have a wider range of application to microwave devices. Microwave circuits such as tuned amplifiers and oscillators with novel structures are proposed, and their excellent characteristics are demonstrated. The experimental results obtained in this study on two and four-port devices make it clear that dual-mode ring resonators have great potential for application to various microwave devices.

A Design Method of Bandpass Filters Using Dielectric-Filled Coaxial Resonators (Short Papers)

Design formulas for capacitively coupled bandpass filters using dielectric-filled coaxial resonators are derived and experimentally verified. The most important advantage of this filter is its ability to provide wide stopband characteristics for harmonics suppression. Its features can be obtained from the configuration using both quarter-wavelength uniform impedance resonators (UIRs) and stepped impedance resonators (SIRs).

A novel millimeter-wave IC on Si substrate using flip-chip bonding technology

A new MM-wave IC, constructed by flip-chip bonded heterojunction transistors and microstrip lines formed on Si substrate, has been proposed and demonstrated. Good agreements between calculated and measured characteristics of this new IC (named MFIC: millimeter-wave flip-chip IC) have been obtained up to 60 GHz band by using micro bump bonding technology. Several MFICs such as HFET/HBT amplifiers have been fabricated to confirm their designed performance.<<ETX>>

Voltage controlled push-push oscillators using miniaturized hairpin resonators

The authors describe the fundamental characteristics of compact stepped impedance hairpin resonators with parallel coupled lines, and show their application to voltage-controlled push-push oscillators for UHF band operation. The experimental push-push oscillators built using these resonators provide low phase noise and wide tuning operation.<<ETX>>

Advanced technologies of low-power GaAs ICs and power modules for cellular telephones

Low-power GaAs ICs and power modules have been developed for 150-cc-type cellular telephones. The front-end IC and power splitter IC can operate under 3 V, and the dissipation current is only half that of Si bipolar ICs. The front-end IC, consisting of a low-noise amplifier, local amplifier, and downconverter, shows a conversion gain of 22 dB at a local power of -15 dBm. The power splitter IC, used in dividing the output power of the voltage-controlled oscillator and supplying the local power to two mixers, shows an output power of 0 dBm and internal isolation of over 25 dB. The power module as a transmitter, composed of a two-stage hybrid amplifier using GaAs MESFETs, can operate at 4.7 V and deliver an output power of 1.5 W at f=950 MHz.<<ETX>>

Adaptive predistortion linearizer with digital quadrature modem

Linearization of power amplifiers using baseband signal processing is an important technique applied in digital mobile communication equipment. However, the linearizer performance has been severely influenced by IQ gain/phase imbalance and DC offset in quadrature modems, significant elements of linearizers. In order to eliminate these detrimental influences, a linearizer using a digital quadrature modem has been developed. This paper describes an adaptive predistortion linearizer using a simplified digital quadrature modem with which experimental results of less than -63 dBc of ACI (adjacent channel interference) have been obtained. This excellent performance may be applied in base stations relating to mobile communication systems.

New type of push-push oscipliers for the frequency synthesizer

The authors describe the fundamental principles of novel voltage-controlled push-push oscipliers (oscillator/doubler) and show their application to a frequency synthesizer for L-band operation. The push-push oscipliers had 2 output ports. By means of a 0 degrees hybrid circuit, the external output power was obtained and the fundamental frequency was adequately suppressed at the same time. By applying the fundamental frequency, which was derived from a 180 degrees hybrid, to a prescaler of a phase-locked loop, the RF input power and the DC power consumption of the frequency synthesizer were reduced. The experimental frequency synthesizer had the advantages of high-frequency operation, compact size, and low power consumption.<<ETX>>