Insertion loss of electronically variable magnetostatic wave delaylines

An investigation is presented of insertion loss and constant variable delays in electronically variable magnetostatic-volume-wave delay lines. The delay line has a conductor-dielectric-YIG-dielectric-conductor structure. Variable delays up to 300 MHz bandwidth have been obtained in a single volume-wave delay line by adjusting the direction and magnitude of the biasing DC magnetic field in a plane containing the normal to the YIG film and the direction of wave propagation. Insertion loss as a function of frequency has been obtained for different biasing field angles and also for the angles corresponding to variable constant delays. Good agreement between theoretically obtained insertion loss and experimental results is found. Electronically variable magnetostatic-wave delay lines have promising applications in broadband phased-array antennas at 1-20 GHz     

An electronically tunable microstrip bandpass filter using thin-film Barium-Strontium-Titanate (BST) varactors

A tunable third-order combline bandpass filter using thin-film barium-strontium-titanate varactors and fabricated on a sapphire substrate is reported. Application of 0-200-V bias varied the center frequency of the filter from 2.44 to 2.88 GHz (16% tuning) while achieving a 1-dB bandwidth of 400 MHz. The insertion loss varied from 5.1 dB at zero bias to 3.3 dB at full bias, while the return loss exceeded 13 dB over the range. The third-order intercept of the filter was found to be 41 dBm.     

Beryllium 100 ns acoustic delay line

A beryllium single crystal is used to fabricate an acoustic delay line. The sputtered ZnO transducers are deposited on the (0001) surfaces. A delay of 110 ns is obtained in the range 1000?2000 MHz with an insertion loss of about 50 dB and spurious responses below 70 dB.     

"Self-stabilized" cascaded negative-conductance amplifiers

A simple circuit is proposed for amplifiers that consist of cascaded negative-conductance stages. A biasing scheme is proposed that utilizes the incremental resistance of the active devices to reduce series resistance in the bias circuit. An experimental two-stage tunnel-diode amplifier of this design provides voltage gain of 10 dB ± 1 dB over a frequency range extending from below 200 Hz to above 25 MHz. The proposed circuit appears practical for design of monolithic circuits requiring broadband gain extending to gigahertz frequencies.     

Generation of spin waves in nonuniform magnetic fields, with application to magnetic delay lines

The theory of spin-wave generation in nonuniform magnetic fields is reviewed. Detailed theoretical results concerning the photon-magnon conversion, the magnon-phonon conversion, the frequency- and field-dependence of the delay time, and the insertion loss are presented. A general theory of the nonuniform demagnetizing field of nonellipsoidal samples is described. Experimental results concerning the field dependence of the delay time are presented both for the case in which the spin waves generated are exchange dominated and for the case in which they are dominated by the magnetostatic interaction. The insertion loss was found to vary with the applied magnetic field in an approximately periodic fashion showing two distinct periods of the order of 1 Oe and 100 Oe. The fast variation (period approximately 1 Oe) has been definitely identified as arising from the excitation of magnetoelastic resonances in the nonuniform magnetic field near the endfaces of the sample. The slow variation (period approrimately 100 Oe) is tentatively attributed to the interference of different partial waves arising from the reflection of the primary wave at the sidefaces of the sample.     

基于短波通信的射频前端电磁脉冲防护模块仿真与设计

随着通信系统面临的电磁工作环境越来越严峻,高功率容量、低插损、快响应时间的电磁脉冲防护模块对其射频前端电路的保护越发的重要起来.本文主要基于PIN二级管射频限幅的原理,构建了PIN二极管的时域等效电路模型,利用去嵌入阻抗场计算方法提取相应电路的S参数,优化设计匹配网络,并采用无源多级PIN二极管结构,设计了一个工作于0~200MHz,插入损耗小于0.15dB,驻波比小于1.4dB,响应时间小于1ns的短波通信电磁脉冲防护模块.结合PIN二极管时域等效电路模型,利用先进设计系统（Advanced Design System,ADS）仿真软件对电磁脉冲防护模块限幅性能进行仿真,并对加工出来的电磁脉冲防护模块进行了测试,结果验证了各项指标满足要求.     

22 ?s S band delay line

A 22 ?s acoustic delay line has been produced on spinel with a centre frequency of 2900 MHz, a bandwidth of 200 MHz and a total insertion loss of 44 dB.     

A 0.5-μm CMOS T/R switch for 900-MHz wireless applications

A single-pole double-throw transmit/receive switch for 3.0-V applications has been fabricated in a 0.5-μm CMOS process. An analysis shows that substrate resistances and source/drain-to-body capacitances must be lowered to decrease insertion loss. The switch exhibits a 0.7-dB insertion loss, a 17-dBm power 1-dB compression point (P_{1 dB}), and a 42-dB isolation at 928 MHz. The low insertion loss is achieved by optimizing the transistor widths and bias voltages, by minimizing the substrate resistances, and by dc biasing the transmit and receive nodes, which decreases the capacitances while increasing the power 1-dB compression point. The switch has adequate insertion loss, isolation, P_{1 dB}, and IP₃ for a number of 900-MHz ISM band applications requiring a moderate peak transmitter power level (~15 dBm)     

Surface-acoustic-wave oscillator tuned by magnetoelastic effect

A new technique for achieving frequency modulation with a surface-acoustic-wave delay-line oscillator is reported. A 339MHz s.a.w. delay line has been fabricated on an epitaxial garnet film. A significant phase-velocity shift has been measured as a function of an inplane magnetic field. An s.a.w. oscillator has been implemented with this delay line and its frequency has been controlled by the magnetoelastic effect. A frequency shift of 600kHz (a relative variation of 1.75 × 10-3) has been obtained by changing the biasing magnetic field.     

一种新型大带宽高通带平坦度延迟线的设计技术

采用倾斜换能器结构,通过优化设计,研制出中心频率800MHz,带宽200MHz,延迟时间为100ns～3μs且精确可控的声表面波延迟线。该系列产品的插入损耗约为-25dB,直通抑制大于35dB,三次渡越抑制大于50dB,200MHz通带内波纹小于1dB,产品综合性能指标优异。     

Multipassband electronically tunable magnetostatic wave filter

A new design for a multipassband microwave filter based on magnetostatic waves propagating in a multilayer planar ferrite structure is described. The experimentally realised filter had two passbands of 10 MHz bandwidth and 5-6 dB insertion loss separated by 400 MHz, and was tuned with an external magnetic field over the 2.5-4 GHz range.<>     

宽带接收机应用的超宽倍频程电调滤波器设计*

电调谐预选滤波器是宽带接收机的关键部件,直接影响到整机性能的好坏。设计了一种采用梳状滤波结构的电调滤波器,工作频段为200~600MHz,整个调谐范围内,1d B带宽约为12%,插入损耗小于3d B,输入二阶截点值大于60d Bm,输入三阶截点值大于20d Bm,输入输出端口驻波比小于1.8,测试和仿真结果吻合良好。该滤波器结构简单、体积小、工艺上易实现,还具有超宽倍频程的调谐范围及低插损、高截点值等优良电性能。     

Tunable microwave oscillators employing narrowband MSSW delay lines

A recently reported experimental study of microwave tunable oscillators employing narrowband magnetostatic-wave (MSW) delay lines is reviewed. The narrowbanding was achieved by usinglifted transducers with magnetostatic surface waves (MSSWs) which yielded a bandwidth of 10 MHz with an insertion loss of less than 20dB. This approach at delay-line narrowbanding does not work as well with the other MSW wave-types because of increased insertion loss. The mode-hopping problem which beset earlier studies of MSW delay-line oscillators was overcome in the present work but now a different problem arose, viz., frequency jumping, which occurred every time the electrical length of the circuit external to the delay line changed by 360 degrees. A maximum tuning range of about 600 MHz was obtained, with this range limited primarily by the Avantek GaAs FET amplifier that was used whose electrical length was equivalent to about 45 cm of air transmission line. It was concluded that, if the electrical length of the external circuit is sufficiently reduced (ideally made zero), singlemode operation over an octave bandwidth or more is possible.     

8-GHz Narrowband High-Temperature Superconducting Filter With High Selectivity and Flat Group Delay

This paper reports a development of a narrowband high-temperature superconducting filter with both high selectivity and flat group delay. The filter has a center frequency of 8.625 GHz and a 3-dB bandwidth of 42 MHz (a fractional bandwidth of 0.49%). In order to achieve both high band-edge steepness and excellent group-delay flatness, we introduce a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure. We also develop a novel low radiation resonator (double-folded resonator) to reduce the parasitic coupling and meet other requirements for the 8-GHz filter. The filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 1.6 dB and a return loss better than 15.5 dB. Band-edge steepness reaches over 11.7 dB/MHz at both the high- and low-frequency edges. The 60-dB rectangle ratio is less than 1.25. The out-of-band rejection is over 70 dB at 5.98 MHz from the 3-dB band edge. The variation of group delay is less than 23 ns over 33 MHz (78.5% of 3-dB bandwidth), and less than 30 ns over 34.5 MHz (82% of 3-dB bandwidth).      

Active GaAs MMIC band-pass filters with automatic frequency tuningand insertion loss control

This paper presents the design and measured performance of active tunable band-pass MMIC filters and matched MMIC control circuits, both fabricated using a standard 1-μm GaAs MESFET foundry process. The control circuits generate filter frequency-tuning and Q-control bias voltages by using a dual-loop master-slave control scheme. Separate 3-section filters cover 1.5-2.0 and 1.96-2.64-GHz bands with 3-dB bandwidths of 86±6 and 126±1.0 MHz, respectively. The control circuits automatically maintain the filter insertion loss to within ±0.5 dB over these tuning ranges, and regulate the center frequency and insertion loss to within better than ±1.2 MHz and ±0.3 dB over a temperature range of -50°C to +75°C     

Measurements and Statistical Modeling of 900 MHz Radio Propagation Channels for Microcellular and Personal Communications in Tunnels

This paper reports the results of measurements of 900 MHz narrow-band radio wave propagation in four tunnels with pedestrians and vehicles. Analysis of the measured data files shows that the power distance factor ranges from 1.87 to 4.44. The power attenation rate with distance is insensitive to the location of the transmit antenna in the cross section of a tunnel, but the transmit antenna insertion loss is. The log-normal distribution fits slow variation of the received signals. The Racian distribution closely describes fast fading in the straight sections of tunnels. However, the Rayleigh distribution does not fit the fast fading in the curved sections of tunnels, as expected.     

A Method for Measuring the Characteristics of an EMI Suppression Ferrite Core

Almost all digital equipment has electromagnetic interference (EMI) suppression ferrite cores to encircle cables, such as mains and peripheral cables. However, their EMI suppression capability is hardly evaluated from the impedance characteristics provided by the manufacturers. Hence, this paper proposes to characterize the ferrite cores in terms of the insertion loss and the reflection coefficient. Theoretical and experimental investigations are carried out to develop a measurement jig for these parameters in the frequency range from 30 to 1000 MHz. It consists of a cylindrical metal rod placed above a metal ground plane, yielding a characteristic impedance of 270 Omega. In addition, a simple method is proposed for measuring the insertion loss and the reflection coefficient of a ferrite core under test. It is found that the proposed method can provide insertion loss data with an error of less than plusmn1.2 dB by using commercially available matching networks (baluns). The reflection coefficient of a ferrite core can be measured with an error less than plusmn1.0 dB. The matching characteristics of the adapters are critical factors that deteriorate measurement accuracy     

Remotely tuned circulator

A rapidly and remotely tuned u.h.f. circulator has been constructed. It gives excellent isolation over a 5 MHz bandwidth, the centre frequency of which may be fixed anywhere within a 20 MHz range merely by changing the bias voltage on a varactor diode. The 20 MHz range chosen may itself be varied over a 200 MHz range by changing the values of certain capacitors.     

High-repetition-rate step-recovery-diode monostable circuits

Improved step-recovery-diode timing circuits are described that have very fast recovery time and freqency-invariant timing period. Output pulse durations from 2 to 100 ns may be generated with less than 10% variation over the frequency range 1?40 MHz.