Third-order intermodulation measurements of microstrip bandpass filters based on high-temperature superconductors

The insufficient power-handling capability of high-temperature superconducting microwave filters has been a serious barrier to their application. To clarify the key parameters for improving the power-handling capability of RF filters based on high-temperature superconductors (HTSs) with microstrip structures, we synthesized bandpass filters with different layouts using several kinds of HTS thin films and performed third-order intermodulation measurements on them. The experimental results indicate that increasing the film thickness and utilizing molecular-beam-epitaxy-grown films of NdBa/sub 2/Cu/sub 3/O/sub 7/ (NBCO) are effective in obtaining microstrip filters with high power-handling capability. For NBCO filters, we also investigated the effects of oxygen annealing, passband width, and the frequencies of the input signals on the power-handling capability.     

Measurement of intermodulation products generated by structuralcomponents

A computer-controlled measurement system is described, developed to investigate intermodulation products generated by nonlinear junctions in antenna towers, mast support and mounting components. Results are presented which suggest that certain mechanical features, commonly encountered in some components, should be regarded as more likely to be associated with this cause of interference     

Measuring television transposer intermodulation distortion

The authors examine the behavior of the intermodulation (IM) level during one line period and propose a measuring method allowing the use of a standard or a modified color-bar test signal. The latter enables the nonlinearity of the transposer to be minimized in the line synchronization region, and this is shown to minimize vision/sound crossmodulation. Differential gain and phase can also be optimized. Measurements indicate that minimization of the IM level with the three-tone method often causes unacceptable IM limits at other colors. The measurement technique is based on sampling the demodulated color-bar signal for short intervals corresponding to a selected color. This allows the simultaneous measurement of IM level at seven different points on the transposer's characteristic     

Zolotarev bandpass filters

Zolotarev rational functions may be used in certain bandpass filter applications for which two narrower passbands are required. Coupled-resonator low-pass prototypes for narrow bandpass filters based on even- and odd-degree Zolotarev functions are synthesized using a transformed variable. Compared to other filters, those with Zolotarev responses have sharper skirt selectivity, resulting in lower passband distortion     

Inductorless bandpass filters

The technique of designing inductorless filters by replacing the inductors in conventional LC filters with gyrators and capacitors is considered for the special case of the high-quality channel bandpass filters used in multiplex telephony. One particular gyrator circuit, which has been found to be very satisfactory, using two operational amplifiers and four resistors, is analyzed in some detail. The difficulties of simulating floating inductors are discussed, and ways of designing filters to avoid the necessity of such simulations are proposed. The dynamic range of a filter is defined and the factors controlling it are described. Detailed measured results of two specific channel filter designs are included.     

Integrated bandpass filters

The letter presents some new results associated with one bandpass (b.p.) filter configuration of the integrated uniform R0-C0KR0 structure consisting of two rectangular resistive films, one having per-unit-length (p.u.l.) constant series resistance R0 and the other KR0 (where K is a dimensionless constant), separated from each other by a dielectric film having p.u.l. constant shunt capacitance C0. It is shown that the output voltage in the b.p. region may be made almost constant for the load fluctuations in the wide range R0 ? Rt < ? (where Rt = load resistance) by selecting K ? 0.3. The range of variation of Rt producing constant output voltage in the b.p. region is found to be narrower for increasing value of K.     

Third-order intermodulation distortion in microwave amplifier

Third-order intermodulation distortions of a microwave GaAs f.e.t. amplifier are analysed using a simple nonlinear model for the device. If the amplifier has strong feedback at low frequencies, the second-order interactions may dominate and degrade the third-order distortions. Solutions are presented to eliminate this distortion degradation. The analysis is very well substantiated by measurements.     

Millimiter-wave stripline bandpass filters

The possibility to use thin (1 mm or less) pseudocombline structures of λ/2 resonators made of sections of symmetric transmission strip lines from a dielectric material with ε _r = 2.2 as millimeter-wave bandpass filters is shown. It is established that the relative bandwidth of such filters can reach FBW = 0.1. Designs of stripline pseudocombline filters with alternating signs of the coupling coefficients, which are characterized by improved selectivity due to the attenuation poles located on both sides of the passband, are proposed; the filters contain stepped-impedance “half-wave” resonators with a new feature. The results of the computer simulation of the frequency characteristics of the filters in the frequency band of 31–122 GHz and the comparison of them with the characteristics of other filters are presented.     

Millimeter-wave tune-all bandpass filters

Distributed microelectromechanical varactors on a coplanar waveguide have been used to design a two- and four-pole bandpass tune-all filters. The two-pole initial bandwidth is 6.4% at 44.05 GHz with a mid-band insertion loss of 3.2 dB and with matching better than 15 dB. The four-pole initial bandwidth is 6.1% at 43.25 GHz with a mid-band insertion loss of 6.5 dB and with matching better than 10 dB. The use of microelectromechanical system bridges allows a continuous tuning for both center frequency and bandwidth. The varactors biasing network has been designed so that the center frequency and bandwidth can be tuned separately. The two-pole filter center frequency can be changed from 44.05 to 41.55 GHz (5.6% tuning range), while the bandwidth can be independently changed from 2.8 to 2.05 GHz. The four-pole filter center frequency can be changed from 43.25 to 40.95 GHz (5.3% tuning range) and the bandwidth can be changed from 2.65 to 1.9 GHz.     

Realisability of bandpass filters

The traditional method of realising attenuation poles by resonant circuits is questioned. It is shown that, under some conditions, it is possible to depart from the conventional solution.     

Origins of intermodulation distortion in transferred-electron amplifiers

Computer simulations and experiments on cathode-notch transferred-electron amplifiers have been carried out to relate one source of intermodulation distortion to the shape of the velocity-field characteristic of GaAs. Other sources of nonlinearity are caused by signal-dependent phase relationships between current and voltage when space-charge propagation effects are important.     

Third-order intermodulation distortion in coherent subcarrier-multiplexed systems

Distortion due to third-order intermodulation products in coherent optical subcarrier-multiplexed communication systems is investigated. It is shown that intermodulation distortion limits both the number of data channels and the maximum obtainable carrier-to-noise ratio. Analysis is restricted to systems operating over one octave. Experimental results on the optimal phase modulation (PM) index based on the number and frequency allocation of the microwave channels are discussed. The conditions for optimal performance with respect to channel number and phase modulation index are given.<>     

Multichannel intermodulation distortion in high-speed GaInAsP lasers

We present an experimental study of intermodulation distortion (IMD) in high-speed, long-wavelength GaInAsP lasers modulated up to 8 GHz. It is found that three-tone distortion products are the dominant contribution to IMD interference when the number of subcarriers is large. These distortion data are used with a simple theory to predict accurately the measured signal/noise ratio for each channel of a multichannel subcarrier system.     

Some arithmetically symmetrical bandpass filters

A combination of the conventional and Matthaei lowpass-bandpass transformations is shown to result in some bandpass filters with very good arithmetic symmetry.     

变容管电调微波带通滤波器

本文叙述采用梳状线结构的变容管电调微波带通滤波器的设计理论和方法。推导出梳状线带通滤波器的输入、输出耦合网络的参数条件,以补偿带通滤波器的谐振器之间电磁耦合随不同调谐频率的变化;并给出使带通滤波器的绝对带宽或通带回波损耗在调谐频率范围内变化最小时,梳状线谐振器的电长度应满足的相应条件,由此来保证电调带通滤波器在较宽的调谐频率范围内具有较高的通带回波损耗,且保持带通滤波器的响应形状和绝对带宽基本不变。此外,还讨论了由电调变容管的Q值引起的带通滤波器的通带有功损耗问题。文中给出了具体的设计公式。最后,给出了一个L波段变容管电调带通滤波器的研制实例和测试结果。     

Universal curves for bandpass filters

Universal curves are presented which permit the determination of bandpass poles when band-edge frequencies and low-pass poles are known. These curves are also useful for band-reject filters.     

Signal×noise intermodulation in translinear filters

The instantaneous companding behaviour of translinear filters forces the use of large-signal equations to calculate the equivalent output noise level of these filters. By using a current-mode approach, it is shown that nonlinear noise calculations become possible for translinear filters     

Novel reduced-size coplanar-waveguide bandpass filters

Two novel reduced-size coplanar-waveguide (CPW) bandpass filters are proposed. Specifically, the bended short-end parallel stubs together with the folded open-end series stubs are utilized to design a broadband filter, and the slow-wave structures are adopted to implement a narrowband filter. In this study, the proposed filters are examined, theoretically and experimentally     

Linearity and third-order intermodulation distortion in DFBsemiconductor lasers

This paper presents a systematic investigation of the third-order intermodulation distortion characteristics in distributed feedback (DFB) semiconductor lasers. The influence of several nonlinearities, such as longitudinal spatial hole burning, gain compression, and relaxation oscillation, is considered. Detailed analysis shows that it is possible to make different nonlinearities cancel one another to give a low intermodulation distortion by choosing the appropriate DFB structure and beat conditions. Specifically, conditions for cancellation between spatial hole burning and gain compression nonlinearities are introduced     

Implication of transistor frequency dependence on intermodulation distortion

An analysis is presented for third-order and second-order nonlinear distortion as a function of frequency for a transistor biased in the common-emitter configuration. It is found that, at high frequency, it is the curvature in the loaded cutoff frequency versus collector current curve that determines the degree of intermodulation distortion. Design proposals for obtaining linear cutoff frequency curves (i.e., small third-order distortion) will be discussed.