摘要:

AbstractWhen the oscillation frequency of a laser diode is stabilized by means of the absorption line of atoms and molecules, a general method used was to apply infinitesi mel modulation directly on the bias current of the laser diode. However, this method has some disadvantages such as expanded oscillation spectral width and restriction of the stabilization frequency to the center frequency of the absorption line.In this paper, the laser light was stabilized by providing modulation indirectly instead of direct modulatin of the oscillation frequency. This is done by modulation of the reference frequency by means of the magneto‐optical effect of the absorption line of the atoms. Further, by comparison of three types of saturated absorption spectroscopy systems, the effect of the magneto‐optical phenomena on the stabilization was examined. As a result, it was found that this method provides a degree of stability comparable to or better than the direct modulation system. Also, the stabilization frequency can be swept and controlled in the range of about 1 GHz without degrading the degree of stabil

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOn the basis of the energy conservation relation between an electromagnetic wave and electron beam, the dynamic behavior of an open‐boundary Čerenkov laser is analyzed theoretically. Specifically, the power growth for the electromagnetic waves, the decrease in the beam drift velocity and its effect due to the growth of the electromagnetic wave, and the improvement in the growth characteristics by varying the permittivity of the dielectric constituting the waveguide are examined. First, it is shown that, since the growth of an electromagnetic wave causes the drift velocity of the electron beam to decrease and keeps the beam and wave out of the synchronism, the spatial growth rate at the frequency initially set decreases gradually and the growth of the electromagnetic power is prevented.Next, to keep the synchronism of the electron beam and electromagnetic wave, the permittivity of the dielectric waveguide can be increased gradually in the direction of wave propagation in accordance with the decrease in the beam drift velocity. This is shown to suppress the decrease in the spatial growth rate due to the decrease in the beam drift velocity and to improve the growth characteristics of the electromagnetic wa

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe principle of the method for excitation of magnetoelastic waves by a nonuniform magnetic field is described. In addition, the distribution of the nonuniform magnetic field appearing in the thin film by the demagnetization effect is obtained. Next, by using a yttrium iron garnet (YIG) thin film with a thickness of 100 μm and 5 × 15 mm2, an experiment of the magnetoelastic wave was carrid out at 3.5 GHz. the experimental results including the delay characteristics of the magnetoelastic wave have been compared with theoretical results. Also, the loss characteristics are studied experimentally from the viewpoint of dependence on the crystal axis. the minimum value of the loss of the magnetoelastic wave is 50 dB and the loss per delay of 1 μs is 30 dB when the crystal axes are oriented in 〈

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA design method is described for a high‐efficiency FET amplifier. First, a method is proposed to derive an optimum load impedance for the second harmonic and the fundamental waves by means of the second harmonic injection load‐pull method and the fundamental wave load‐pull method. Then, to realize the resulting load impedance, a small harmonic terminating circuit is studied which consists of a short phase‐adjustment transmission line and a second harmonic parallel resonant circuit made of lumped elements. Also, a method is shown for determining the FET gate width for each stage to maximize the efficiency of the multistage amplifier including the driver stages. the UHF monolithic four‐stage FET amplifier fabricated using this design method has exhibited a saturated output power of 31 dBm and a maximum drain efficiency of 6

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA highly compact GaAs power module designed for the portable analog telephone system has been developed [1]. the module is a two‐stage GaAs power amplifier operable at 4.7 V and is capable of delivering an output power of 32.2 dBm with a power‐added efficiency of 65 percent and harmonic levels less than −40 dBc at 900 MHz.Parameter extraction from two GaAs MESFETs (first‐ and second‐stage FETs) operable at 4.7 V, module design employing a front stage FET whose output characteristics are optimized at a load of 50 ω, and the optimization of harmonic control circuit suppressing the harmonics and improving the drain efficiency are performed by simulation and the obtained results are confirmed by e

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes a high‐efficiency linear power amplifier using an envelope feedback method for a digital cellular telephone. Adjacent channel interference due to the amplitude and phase distortions of the amplifier is analyzed for a π/4‐shift QPSK modulation scheme. From the analysis amplitude error compensation circuits are proposed and the limit of phase‐shift variation caused by AM/PM conversion is discussed. the drain power efficiency of 50 percent at the low operation voltage of 5.8 V is achieved experime

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA voltage‐controlled oscillator (VCO) with a small power consumption and an excellent signal‐to‐noise (C/N) ratio was developed for a portable telephone. In the domestic analog portable cellular portable telephone,C/Nis reguired to be more than 107 dBc/Hz at an offcarrier frequency of 12.5 kHz. to realize this value, the noise behavior was studied for a 900‐MHz oscillator using a small‐signal, high‐frequency silicon transistor.First, the relationship between the transistor noise and theC/N, the operating voltage and current dependence of theC/Nand the relationship between the collector breakdown voltage and the oscillator output were studied experimentally. A transistor was selected which is most suitable for a low‐noise VCO at a low operating current of 3 to 7 mA.Next, by using this transistor, the relationship between the unloadedQof the resonant circuit and theC/Nwas studied. It was found thatQof 60 is needed to obtain aC/Nwith a 3‐dB margin. On the other hand, with a view to miniaturizing the resonator, a dielectric coaxial resonator with a material having a relative permittivity of 90 was studied experimentally. AQof 200 was realized with a resonator having a cross‐sectional size of 1.8 × 1.8 mm2. By combining it with a varactor diode, aQof more than 60 was attained. Based on these results, a low‐noise VCO was realized which has dimensions of 10 × 10 × 3 mm and is operated with a power supply voltage of 3 V and a curren

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe bandpass filters installed in digital mobile communication equipment are required to have characteristics with low spurious responses over the broadband. In this paper, a bandpass filter with low spurious response based on a coplanar waveguide resonator (CPW‐BPF) is proposed which can be applied for MIC and MMIC and its characteristics are discussed. the suppression of the spurious responses is accomplished in this paper by the following method.First, a coplanar waveguide resonator filter is realized. Next, the resonator length is reduced to less than one‐twentieth of the wavelength at the center frequency. Finally, lumped capacitors are added to these reduced resonators in parallel and after that adjusted so that the desired bandpass characteristics are realized. This reduced CPW resonator can be considered approximately as an “L” near the center frequency of the passband. Therefore, by adding in parallel a capacitor, an “LC” resonator can be formed. As the result, the spurious responses concerning the resonant frequency are suppressed.The three‐stage CPW‐BPF fabricated by the proposed method has the center frequency of 1.0 GHz in the passband and a bandwidth of 100 MHz and can suppress the spurious responses to −40 dB up to 7.5 GHz and to −3

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractJosephson junctions with microstrip resonators fabricated. By observing the current steps caused by the mutual interaction between the high‐frequency current due to the ac Josephson effect and resonator, the dielectric constants of the dielectric thin films (a‐Si, SiO, and SiO2) and surface resistance of an Nb thin film at 4.2 K in the millimeter and submillimeter wavelength region were evaluated. As a result, it was found that this method was effective in determining the dielectric constant and surface resistance.In the device used, a Josephson junction was placed at the center of the microstrip resonator. the resonator length was varied from 217 to 2740 μm, the measurements were carried out at a frequency ranging from about 30 to 310 GHz, while the device was biased with dc voltage. the relative dielectric constants of the materials were rather independent of the frequency, where Ωa‐Si= 14.5 ± 0.5, ϵSiO5.5 ± 0.4, and ϵSiO2= 4.4 ± 0.4. the surface resistances of the Nb thin films were 1 to 6 mω when the frequencies were

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper proposes the (4, 5, 6)/11 code, which is a newn/mcode, constrained in that the minimum runlength of symbol “O” in the codeword is 2 and is suited to PR(1, 1) equalization. In PR(1) equalization, a pseudo‐PR(1, 1) characteristic is obtained by shifting the sampling points byTs/2(whereTsis the symbol interval). Assuming that the conventional Viterbi decoding is applied to the (4, 5, 6)/11 code, the error‐rate characteristic is examined by simulation, and the result is compared to that of the well‐known 4/11 code. It is shown as a result that the (4, 5, 6)/11 code has an excellent performance. Then a modified Viterbi decoding is considered by utilizing the run‐length constraint, and the performance is evaluated.The colored noise sequence is approximated by a simple Markov process and another modified Viterbi decoding utilizing the correlation of the noise sequence also is considered. It is shown as a result that the CN ratio is improved compared to the conventional Viterbi decoding by about 1.0 dB in the former and about 2.7 dB in the latter, at the error r

ISSN:8756-663X    

DOI:10.1002/ecjb.4420770310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY