It can be seen that good performance is achieved over a wide bandwidth (2-8GHz), in good agreement with classical theory. l o @ H*G 511 REF 0 . 0 d0 5.0 d W & . The performance may be summarised as : operating frequency: coupling : phase difference: isolation : return loss: 5.0 f 3.0 GHz (120% bandwidth) 3.6 f 0.6 dB 90" f 1.5" 20 dB 20 dB Conclusion: These results should enable us to develop wideband circuits such as mixers or phase shifters using this technology. The ultimate limitations on performance will be the accuracy of the models used and the minimum dimensions that can be achieved, with adequate repeatability. 25th August 1992 D. Bourreau, B. Della, E. Daniel, C. Person and S. Toutain (ENST de Bretagne, BP 832,29285 Erest Cedex, France) References LEMB", P., PERSON, C., DELLA, E., TOUTAIN, S., and LE =LE, P.: 'Multi-layer thick-film technology for microwave integrated circuits'. M.I.O.P. '90 Microwaves and Optronics, 24-26 April 1990, Stuttgart, Germany 2 PRESSER,A.: 'Interdigitated microstrip coupler design' IEEE Trans., 1978, MlT-26, (lo),pp. 801-805 3 HP/MDS application software 1 START STIP 0.045000000 CHz 10.845000000 Ml Fig. Sa Return loss PARAMETRIC INTERACTION OF MAGNETOSTATIC WAVES IN UNIFORM NONSTATIONARY- M A GNETlSED GAR N ET FILM S. N. Dunaev and Y. K. Fetisov Indexina terms: Maqnetostatic waves, YIG-film The interaction of two magnetostatic waves (MSW)in a garnet film placed in a harmonically-modulated external magnetising field is experimentally investigated. An MSW frequency shift of up to MOMHz and interaction efficiency of up to a few percent were obtained. - START Introduction: Magnetostatic wave (MSW) excitation and proe.045ew0.0 0 . . . e . 5 4 . . 0 1 Fig. 5 ) Isolation MI MI s2l 1-9 l o g MAG REF 0 . 0 dB START 5TpI m.e~mmmemmwZ 10.e4500e" Fig. k Coupling and direct ports 1998 - pagation in planar structures with nonstationary parameters based on yttrium-iron-garnet (YIG) films are accompanied by various dynamic effects, such as MSW amplitude and phase modulation [l-23, MSW packet compression [SI, and MSW phase synchronisation [4]. These interactions have already been applied to microwave signal processing. We report the first observation of the parametric interaction of two MSWs in a garnet film placed in an external harmonically modulated magnetising field. The experimental setup is shown in Fig. 1. The MSW transmission line contained a YIG film of thickness d = 20ym, 117015CI 1994/11 M. Fig. 1 M S W transmission line ELECTRONICS LETTERS 8th October 1992 Vol. 28 No. 21 saturation magnetisation 4nM = 1750Gs, uniform resonance linewidth AH 0.5Oe, prepared by LPE technology on a gadolinium-gallium-garnet (GGG) substrate of 3 x 25 mmz dimensions. Two wideband microstrip transducers of 50pm width deposited on the film surface at a distance y = 0.4cm apart were used to excite and receive MSWs. The structure was placed in an external uniform DC magnetising field of H , = 1.95 kOe applied at an angle of 8,= 17' in the plane containing the normal to the film and the wave propagation direction. Field modulation with a frequency F = 20300 MHz and magnitude of up to h = lOOe was applied using an electromagnetic coil wound on the substrate MSWs were excited by a continuous electromagnetic (EM) signal of frequency f = 3-4GHz and power P = 1 mW. The spectra of reflected P , ( f ) and transmitted P 2 ( f )signals were investigated by using a directional coupler and a narrowband electronically tuned filter. as in the transmitted signals [4]. For F 2 100-300MHr. when f belonged to the MSBVW (or MSFVW) branch and frequencyf+ F in the other branch, the harmonic of the frequencyf+ F ( o r f - F ) appeared only in the reflected signal, as shown in Fig. 3. The power of the harmonic increased nonlinearly with an increase in the magnitude of the modulation field. Experimentul results and discussion: There are two kinds of MSW in the structure considered: magnetostatic forward volume wave (MSFVW) and magnetostatic backward volume wave (MSBVW). Both branches of the dispersion curve are well described by the simple equation kd = 1 psin2p + cos2D1 f f+F freqsevc! Fig. 3 Spectrum of reflected microwuce signal Horizontal scale: 60 MHz division , \I( - P ) where P = 1 + ( f H f M M f ;-f?, fil = Y H , f M = YM, y = 2.8 MHz/Oe, N = 0, 1, 2 . . . is the volume mode number, and H and 11 are the strength and angle of the internal magnetic field in the film, which differ from those of the external magnetising field because of demagnetising effects and may be easily calculated. MSFVW and MSBVW of the parallel wave vectors have oppositely directed group velocities. Under stationary conditions, the measured amplitude response L(f)and dispersion k ( f ) for MSVWs in the transmission line are presented in Fig. 2u and b. The shape of the amplitude response is determined by the EM MSW conversion efficiency and MSW propagation losses at each frequency. The theoretical dispersion curve (dashed line) was calculated using eqn. 2 for the main mode ( N = 1) and parameter values H = 0.8 kOe, fi = 45". Propagation of the waves with maximal wave numbers up to k = 300~x1-' were observed. Minimal insertion loss was equal to -15 dB for both MSFVWs and MSBVWs of wave numbers k 1125"'. The generation of a lateral harmonic is explained by the parametric interaction of two MSVWs in a space-uniform nonstationary medium when the following phase-matching conditions are satisfied: R,=R,, (2) f i + F = f 2 where ( R , , f , J and ( R 2 , . f 2are ) the wave vectors and the frequencies of the interacting waves, respectively, and F is the frequency of the magnetic field modulation. The nonsymmetry of reflected and transmitted signal spectra may be easily understood by taking into account the contradirectionality of the group velocities of the initial and generated waves. The input signal of frequency f excites a wave in the ferrite film of wave vector R I , whose power flow is directed to the output transducer. In the domain between the transducers a wave of frequencyf+ F ( o r f - F ) and wave vector R, = R I is generated, whose power flow is directed in the opposite direction. The last wave is registered by the input transducer. We describe the MSW interaction efficiency by a coefficient (3) where P , w s , ( f ) and P , M s w ( f TF ) are the powers of the initial and generated waves near the input transducer, respectively. q may be approximately expressed in terms of the measured amplitude response of the transmission line and powers of microwave signals P(f)and P i ( f k F ) : -10-30 -50 loss L , dB 0 U 100 2OC m ~ v e n u m b e rk,c" 300 m - Fig. 2 Amplitude response and dispersion churacreristlc o / M S W trum- mission line a Amplitude response h Dispersion curves After modulation, lateral harmonics appeared in both the reflected and transmitted signal spectra. The power of the harmonics and their number depended on thefposition in the dispersion curve and value of F . For F 5 50MHz, whenfwas placed in the middle part of the MSFVW or MSBVW frequency band, the previously observed harmonics of the frequencies/+ nF (n an integer) appeared in the reflected as well ELECTRONICS LETTERS 8th October 1992 Vol. 28 No. 21 where L(f)and L(f? F ) should be substituted in relative units. The dashed line in Fig. 3. shows the dependence of interaction efficiency q on field modulation frequency F for k 1 125cm calculated using eqn. 4 and experimentally obtained data. Maximal q. as expected, was obtained under exact synchronisation of the interacting waves. The interaction bandwidth at -3dB level was equal to 6 F = 100MHz; it decreased to 6 F 5 60MHz with an increase of k. Under exact synchronisation conditions, q increased with k increasing, that is, with an increase of interaction length y to wavelength i ratio, maximal value q = 3.2% was reached for y i l = 8 and then decreased for k 2 125cm . The last was due to the violation of the phase-matching conditions because of nonuniformity in the internal magnetising field in the film and a decrease of the modulation field magnitude at higher frequencies. ~ ' 1999 Conclusion: We believe that the efficiency of parametric MSW interaction may be increased up to several tens of a percent by increasing the modulating field magnitude and by using more uniform ferrite structures with lower losses. The phenomenon described is promising for applications in the design of microwave mixers and spectrum transformation devices. where a = {ak} is a sequence of independent, equiprobable, M-ary symbols from the set { 4 m ) = 2m - 1 - M: m = 1.2,. . . M}. The specular component is 10th August 1992 S. N.Dunaev and Y . K.Fetisov (Moscow Institute of Radio Engineering & Electronics and Automation, Vemadskogo 78, 117454 Moscow, where P. is the average power, 4 k = 4,- 1 + ak n/M p(t) is a unit energy pulse and diffuse component is References D. c., and MOORP. R.: ‘YIG magnetostatic mode serrodyne’, Proc. IEEE, 1966.54, pp. 685-686 2 REZENDE, s. M., and MORGENTHALW, P. R.: ‘Magnetostaticwaves in time-varying magnetic fields. I1 Experiment’, J. Appl. Phys., 1969, 40,pp. 537-545 1 WEBB, 3 PREQBRAZHENSKY, v. L., RYBAKOV, v. P., and m v , Y. IL: ‘Space4 time focusing of magnetostatic wave packet in a nonstationary medium’, JETP Lett. (Sou.), 1987,46, pp. 114-117 DUNAEV, s. N., and FETISOV, Y. K.: ‘Multimode oscillation and mode locking of magnetostatic wave delay line oscillator’,Electron. Lett., 1992,28, pp. 789-791 DPSK WITH SINUSOIDAL PULSE SHAPING IN RlClAN CHANNEL denotes convolution. The d(t, a) = -.j(Pd)S(t - td, a)e(t)exp (4) t) CiZnfD where P , is the average power, fD is the Doppler frequency shift, @ t ) is a zero-mean, complex, Gaussian process with autocorrelation RAT) which for an omnidirectional antenna used often in land mobile radio is Here Jo( ) is the zero order Bessel function of first kind, the bar denotes the average value and the subscript * denotes the complex conjugate. The noise in eqn. 1 is zero mean, Gaussian. The autocorrelation of &,U ) is R,(t, T, a) = 0.5& a)p*(t - T , a) = RAt, T, a) Indexing t e r m : Phase-shift keying, Mobile radio system, Satellite relay system The use of pulse shaping to combat multipath propagation effect in Rician channels is proposed. Because of the time delay td between the specular and diffuse signal components, pulse shaping can reduce their correlation. Analysis and numerical results are given. Introduction: The received signal of the satellite mobile channel (SMC) is composed of three parts: a specular component, a diffuse component and noise [I]. It has a Rician envelope. The diffuse component, caused by multipath scattering, makes the design of a satellite mobile communication system very challenging. The SMC can be characterised by a parameter K which is the ratio of powers of the specular and diffuse components. In a typical situation, the diffuse component makes up 10% of the received signal (K = 10) and has a delay of up to Sops [2]. In most communication systems, the pulse in the receiver is matched (both in time and shape) to the transmitted pulse to achieve a minimum probability of error. This probability is independent of the kind of pulse used in the system. In the SMC, although the diffuse signal has the same pulse as the specular signal, because of time delay, it is only partially correlated with the pulse in the receiver. Different pulses have different values of this correlation, and therefore we can select pulse shaping to reduce the effect of diffuse signals. - + R,(T) (6) RAT)= N o x S*(t - td - T, a) exp (2JnfDT) (7) j (8) -m I p(f)1’ exp Ci2nfT) df The signal ratio is related to the energy to noise ratio per bit by where E, is the bit energy. We can use the formulas [3,4] to compute the bit error probability (BEP). Analysis and numerical results: The BEP is largely affected by two factors: total value of RAt, 0, a) and intersymbol interference. When both of them are decreased, the performance of the system in Rician channel is close to that in Gaussian channel (K = 00). The total value of RAt, 0, a) is determined by three terms: P,, RdO) and I S(tk- t,, a).1’ P,and RdO) are fixed for given E,/N,, K and the type of antenna, but we can reduce the value of I S(tk - t,, U ) 1’ by choosing a proper pulse shape. Assuming a unit energy pulse, time limited to (-T/2, T/2),for k = 0, t o = T and 0 It , 5 T , we have s = Is(t0 - td, a)l’ = lexp ( - ; & O ) d - t d ) + exp ( - J & - l ) d T - td)12 (lo) where the first term of eqn. 10 depends on a, and the second term depends on a- (thus is intersymbol interference) which can be evaluated from G = g 2 ( T - t,). For binary symbols, we obtain w conjugate 4, Fig. 1 Model of receiver Signal and system: Fig. 1 shows a baseband equivalent model of the receiver. Assuming the system contains an automatic carrier tracking circuit and fD, (the maximum Doppler frequency) is much smaller than the signal bandwidth, the output of the receiver filter is (1) - = +n/2 s = g’(-t,) + g2(T - t,) ~ (11) The value of RAC, 0, a) is directly affected by pulse shaping and independent of the value of symbols. Two pulses used in the numerical analysis are pl(t) = J ( I / T ) u A ~ )PA^) = JWT) sin ( n t / T ) U d t ) (12) where U,@) is a rectangular pulse time limited to (- T/2, T/2). We show BEP, S and G as functions of t d / T for M = 2, ELECTRONICS LElTERS 8th October 1992 2000 ~ * RAt, T, a) = P, R ~ T ) S-( t,, ~ a) I. Korn and L. Wei r(t, a) = s(t, a) + p(t, U ) = s(t, a) + d(t, a) + n(t) (3) A t ) = p(-t)*p(t) Russia) Vol. 28 No. 21 ~~~

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