Yasunori Atsumi

Wideband Planar Folded Dipole Antenna With Self-balanced Impedance Property

A planar folded dipole antenna that exhibits wideband characteristics is proposed. The antenna has simple planar construction without a ground plane and is easy to be assembled. Parameter values are adjusted in order to obtain wideband properties and compactness by using an electromagnetic simulator based on the method of moments. An experimental result centered at 1.7 GHz for 50 impedance matching shows that the antenna has bandwidth over 55% . The gains of the antenna are almost constant (2 dBi) in this frequency band and the radiation patterns are very similar to those of a normal dipole antenna. It is also shown that the antenna has a self-balanced impedance property in this frequency band.

A predistortion-type equi-path linearizer designed for radio-on-fiber system

A predistortion-type equi-path linearizer is created for a radio-on-fiber system based on wide-band code division multiple access; its main benefit is its simple optical circuit configuration. Experiments show that the phase difference between the carrier and third-order intermodulation (IM3) component of the laser diodes (LDs) is shifted by around 90/spl deg/ from that of the RF amplifier. To our knowledge, this is the first report to describe this phase shift, which is observed with both Fabry-Perot and distributed-feedback LDs. To counter this shift, we use additional phase shifters. The proposed design places a pre-amplifier between the linearizer and LD for lower power consumption and better insertion gain at the linearizer. Experimental and calculated results agree well, and more than 20-dB improvement in the IM3 components is obtained over the bandwidth of 60 MHz. The linearizer works well in the temperature range of 10/spl deg/C to 40/spl deg/C with a simple control circuit.

Wideband Folded Loop and Folded Dipole Antennas

In this paper, the aim is to investigate the folded loop antenna (FLA) without ground plane (GP) in detail, and to find optimum antenna parameters for wideband characteristics. In the analysis, the electromagnetic simulator IE3D based on the method of moment (MoM) is used. Consequently, it is shown that the folded construction at both ends of the FLA is not necessary for wideband properties, and planar folded dipole antenna (FDA) also has wideband characteristics

Design and fabrication of multiband p-i-n diode switches with ladder circuits

Single-pole double-throw switches composed of p-i-n diodes are proposed for multiband operations. A ladder resonance circuit is introduced to simplify their configuration and to reduce the cost. The isolation greater than 20 dB and the insertion loss less than 2 dB are achieved in experiments at three frequency bands: 1.6, 2.5, and 5.8 GHz. Resonance frequency variations are investigated in detail for two types of switches consisting of: 1) lumped circuit elements and 2) semimicrostrip elements. The variations on the semimicrostrip configuration are about 25% of those with lumped circuit elements. The proposed switch does not influence the switching speed and signal distortion characteristics. It also showed good temperature stability from -30/spl deg/C to +85/spl deg/C.

Frequency multiplexing technique for relative-intensity-noise reduction

A 10 dB relative-intensity-noise reduction is achieved by a novel scheme that multiplexes local-oscillation frequency and intermediate frequencies. Simulations conducted to evaluate relative-intensity-noise levels match well the experimentally obtained data.

Planar dual-band omni-directional UHF antennas employing a composite right/left-handed double-sided metal layer structure

This article presents planar dual-band omni-directional antennas employing a composite right/left-handed (CRLH) metamaterial for UHF applications. The antennas are compact and in a simple double-sided planar configuration without using vias or lumped-elements and have an omni-directional radiation pattern regardless of having a ground plane at the backside. A dual-band antenna operating at a pair of the negative (ƒ<inf>−1</inf>) and positive (ƒ<inf>+1</inf>) resonant frequencies is designed at 373/817MHz and the dual-band operation with omni-directional radiation patterns are demonstrated. The physical size of the presented antenna is λ<inf>−1</inf>/13 × λ<inf>−1</inf>/18 × λ<inf>−1</inf>/1005 at ƒ<inf>−1</inf>, and λ<inf>+1</inf>/8 × λ<inf>+1</inf>/6 × λ<inf>+1</inf>/459 at ƒ<inf>+1</inf>, where λ<inf>−1</inf> and λ<inf>+1</inf> are free space wavelengths at ƒ<inf>−1</inf> and ƒ<inf>+1</inf>, respectively. Maximum measured gains at ƒ<inf>−1</inf> and ƒ<inf>+1</inf> are −13.8dBi and −0.5dBi, respectively.

Distortion Reduction Filters for Radio-on-Fiber System

Three distortion reduction filters for radio-on-fiber systems are proposed and evaluated from the standpoint of improvements in in-band third order Intel-modulation (IM3) components (spurious components), insertion loss, temperature stability and so on. The basic filter configuration includes optical comb filter, RF (radiowave frequency) comb filter, and RF dual band rejection filter (DBRF). Experiments are conducted at 2 GHz band for frequency separation Δf=5 MHz and 100 MHz in the temperature range of -10°C to +50°C. These filters can reduce IM3 components even in the saturation region, unlike conventional linearizers. An optical comb filter can reduce IM3 components more than 20 dB and noise level around 10dB if its polarization controller is properly adjusted, but its insertion loss is large and stability against vibration is very poor. The proposed RF comb filter and RF-DBRF can reduce IM3 components by more than 20 dB and noise level by more than 3 dB. Their stability against vibration and temperature change is good, and insertion losses are 1-2 dB for Δf= 100 MHz.

Distortion Evaluation of Frequency-Converted Radio-on-Fiber System Employing RIN Reduction Technique

The distortion characteristics of a radio-over-fiber (ROF) system that uses the relative intensity noise (RIN) reduction technique is investigated in detail. The third-order intermodulation (IM3) and spurious free dynamic range (SFDR) characteristics of this system are measured using multi-reflection configurations. It is observed that the maximum deterioration in IM3 is 4 dB. However, SFDR is improved by 7 dB as CNR exceeds 12 dB. Moreover, we measure the adjacent channel leakage power ratio (ACLR) characteristics of this system in the multi-carrier transmission condition. The RIN reduction technique yields an ACLR improvement of 4.5 dB

Relative-intensity-noise reduction technique for frequency-converted radio-on-fiber system

A radio-on-fiber system is proposed that uses a frequency-multiplexing technique to reduce the relative intensity noise (RIN) caused by reflections at optical fiber connectors. It is based on the simultaneous transmission of IF and local oscillation (LO) frequency. Optimum LO frequency and optical modulation index that minimize RIN are investigated by experiments and calculations assuming the double and multiple reflection situations. The results agree well and RIN reduction of 17 dB is obtained in multiple reflection situations.