Impedance matching with a series transmission line section

A generalization of the transmission line quarter-wave impedance matching transformer is presented. The resultant series-section transformer can match complex as well as pure resistance loads to a transmission line, and the choice of the characteristic impedance of the matching section is not restricted to a single value.     

A review of localization systems for robotic endoscopic capsules

Obscure gastrointestinal (GI) bleeding, Crohn disease, Celiac disease, small bower tumors, and other disorders that occur in the GI tract have always been challenging to be diagnosed and treated due to the inevitable difficulty in accessing such a complex environment within the human body. With the invention of wireless capsule endoscope, the next generation of the traditional cabled endoscope, not only a dream has come true for the patients who have experienced a great discomfort and unpleasantness caused by the conventional endoscopic method, but also a new research field has been opened to develop a complete miniature robotic device that is swallowable and has full functions of diagnosis and treatment of the GI diseases. However, such an ideal device needs to be equipped with a highly accurate localization system to be able to exactly determine the location of lesions in the GI tract and provide essential feedback to an actuation mechanism controlling the device's movement. This paper presents a comprehensive overview of the localization systems for robotic endoscopic capsules, for which the motivation, challenges, and possible solutions of the proposed localization methods are also discussed.     

Impedance matching considerations for ferrite Faraday rotators

When a linearly polarized plane wave propagates from a dielectric medium into a medium with Faraday rotation, a reflected wave will always occur at the interface. This reflection is necessary because the normal-mode wave impedances in the medium with Faraday rotation are nondegenerate, while the equivalent normal-mode wave impedances for the dielectric medium are degenerate. Therefore it is not possible to match both normal modes simultaneously at the interface. This paper investigates the peculiar reflected wave associated with impedance matching of Faraday rotators, and shows that it should have minimal impact on practical devices.     

Impedance matching arrangement for quadrifilar helix antennas

A ring arrangement of four wires near to the excitation point of a quadrifilar helix antenna can be used to achieve an impedance match. The matching technique is applicable to resonant, fractional turn antennas, and to shaped conical beam backfire mode antennas     

Optimum source admittance matching for low-noise receivers without transformer

The noise behaviour for various connections of two 2-ports has been theoretically considered previously. A generalisation of the results yields an equation for the noise factor of n parallel 2-ports. It follows from this equation that the optimum source admittance for low-noise receivers can be matched without a transformer, a fact which may be very useful in the v.h.f. and u.h.f. ranges, where lossless impedance transformation is difficult.     

Impedance matching for complex loads through nonuniformtransmission lines

A numerical method for designing nonuniform transmission lines (NTLs) to match complex loads is presented. This method is based on solving an inverse problem derived from the telegrapher's equation. The matched NTLs are expected to have bandpass characteristics covering the sampling frequency points. A numerical algorithm is provided and verified by examples     

Impedance matching improvement for a class of wideband antennas

A simple and efficient technique for improving the impedance matching of a class of wideband antennas is presented. These antennas have impedance characteristics that exhibit dual (or multiple) resonance. The results obtained are in good agreement with the experimental test.     

Impedance matching of an infinite phased array by dielectric sheets

Present design work on driving-point-impedance matching in wide-angle phased arrays relies on experimental trial and error; this letter presents an analytical solution to this important practical problem.     

Behavioral-level event-driven power management for DECT digital receivers

Power management is a low-power design technique applicable in almost all design levels. Here, the idea of exploiting events to trigger the shut-down of hardware resources is applied at the behavioral-level of a DECT digital receiver design. Power management involves a trade-off between the power savings arising from the power-down (or shut-down) parts of the system and the power increase due to the additional logic for the generation of the shutdown signals. For that purpose, taking into account the digital receiver's characteristics, a behavioral-level power management technique is introduced. The efficiency of the proposed technique is proven by its application on an industrial DECT receiver, where a power saving of 50% in terms of the dynamic power consumption is achieved.     

Impedance criterion for power modules comparison

It is well known that power modules must exhibit as low as possible stray inductance. However, the total inductance of a power module is not the only parameter to indicate the electrical quality of the packaging. In this paper, mathematical criteria will be given, which will allow the evaluation of power modules interconnects with regard to several objectives: equal current constraints among the different paralleled dies, power-drive, and even drive-drive interactions.     

Design of inductive p-i-n diode matching for optical receivers withincreased bit-rate operation

We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples     

电磁吸波材料中的阻抗匹配条件

电磁吸波材料研制中一个关键性问题就是匹配规律问题.根据电磁波与材料相互作用的原理,从电磁波在材料中传播的波阻抗关系出发,探讨并提出了电磁波在电磁吸波材料表面无反射吸收时的阻抗匹配条件,讨论了该匹配条件的物理意义,并应用电磁场数值方法验证了其正确性和适用性.该匹配条件简单明晰,它对于研制高水平的电磁吸波材料具有重要的指导作用.     

Fast stochastic power control algorithms for nonlinear multiuser receivers

Uplink communication in a cellular radio network is considered where the base station in each cell employs linear or nonlinear (decision feedback) multiuser receivers. For any such receiver, the problem of interest is that of minimizing the total transmit power under the constraint that all the users of the network achieve their quality-of-service objective in terms of signal-to-interference ratio (SIR). When the solution is feasible for the desired SIR requirements, the optimum powers are computed with a distributed iterative power control strategy suitable for implementation at each base station. While the deterministic algorithm requires both in-cell and out-of-cell user information, the stochastic algorithm proposed in this paper can be implemented at the base stations in a truly distributed manner requiring knowledge of only in-cell parameters. Such an algorithm was proposed previously for the case where base stations use linear (single user) matched filter (MF) receivers. However, the feasibility region in terms of attainable SIRs for a well-designed multiuser receiver, particularly for a nonlinear receiver that employs decision feedback, is generally much larger than it is for the linear MF receiver. The stochastic power control algorithm in this paper, for linear or nonlinear multiuser receivers, converges in the mean-square sense to the minimal powers when the target SIRs are feasible. The second major focus of this paper is to improve the convergence properties of the conventional stochastic approximation based power control strategy by using the more recent results on averaging. Convergence issues of both the "nonaveraged" and "averaged" algorithms are investigated, and numerical examples are presented to demonstrate the performance improvement due to averaging.     

Impedance matching a phased-array antenna over wide scan angles by connecting circuits

In a phased-array steerable-beam antenna, the active impedance of the radiating elements exhibits considerable change with scan angle. Because of this change, it is ordinarily possible to match the active impedance at only one angle. However, by the addition of lossless circuits which interconnect the element lines, good impedance match over a wide range of scan angles may be obtained. The effects of connecting circuits are easily analyzed in terms of simple equivalent circuits when the array is infinite. For this reason, and because no change is required in the radiating element, the connecting-circuit method is well suited for application to phased arrays containing a large number of regularly-spaced elements. As an example of the use of connecting circuits for wide-angle matching of an array, calculations are made for an infinite planar array of dipoles. Scanning the beam of this array within a120degcone is assumed to cause a mismatch as great as 14-db SWR at some angles when no connecting circuits are used. With the addition of a set of connecting circuits in theEplane of the array and another set in theHplane, this limit is reduced to 4.5-db SWR. The improvement in this impedance match corresponds to a 2.3-db increase of gain realized by the antenna.     

Impedance specifications for stable DC distributed power systems

In a DC distributed power system, the interaction between individually designed power modules/subsystems may cause the instability of the whole system. In a small-signal sense, system level stability is determined by the impedance ratio Z_o/Z_i. Here, Z _o is the output impedance of the source module/subsystem, and Z_i is the input impedance of the load module/subsystem. As a result, an effective way to prevent system instability is defining impedance specifications for modules/subsystems. This paper briefly summarizes existing works and introduces the authors' contribution in defining impedance specifications. A new forbidden region for impedance ratio Z_o/Z_i on the S-plane is proposed as the system stability margin requirement. Based on this proposed forbidden region, the impedance specifications of individual loads are established. Further, a very practical measurement approach is developed to examine whether or not the system stability margin requirement of the forbidden region is satisfied     

Impedance matching of tapered slot antenna using a dielectrictransformer

A new impedance matching technique for tapered slot antennas using a dielectric transformer is presented. The technique is demonstrated by measuring the input impedance, VSWR and the gain of a Vivaldi antenna (VA). Measured results at Ka-band frequencies are presented and discussed     

Spreading and power allocation for multiple antenna transmission using decorrelating receivers

We propose a new scheme for multiple antenna transmission in the context of spread-spectrum signaling. The new scheme consists of using shifted Gold sequences to modulate independent information on the multiple antennas. We show that this strategy of using multiphase spreading (MPS) on different antennas greatly improves the throughput over currently known spread-spectrum multiple-antenna methods. We also find the optimal power allocation strategy among multiple transmit antennas for a fixed rate of channel state information, which might be provided via a feedback link, at the transmitter. We demonstrate the differences in optimal power distribution for maximizing capacity and minimizing probability of outage. When the transmission from the two antennas uses orthogonal spreading, we find that optimizing the power does not give much gain over the equal power transmission. However, when the transmissions are not orthogonal as in the case of MPS, then allocating power to maximize throughput gives considerable gain over equal power transmission. We also consider the effect of imperfections in the feedback channel on the optimal power allocation and show that our power allocation scheme is robust to feedback errors.     

CTL码和TC码的特点及应用

在电视制作和播出中,CTL码和TC码是目前应用得最为广泛的两种时间计数编码.电子编辑和播出控制中节目入点和出点的确定与节目长度的统计、节目编排、素材磁带的管理等都是利用这两种编码方式进行的.本文将对这两种编码方式做简单介绍和对比分析,并根据目前许多兄弟台具备TC码条件却仍使用CTL码的情况,提出一个推广TC码的倡议,有不当的地方,请各位同行指正.     

彩电回扫式开关电源的设计

详细介绍了回扫式开关电源的设计,特别是其关键部分－－开关变压器的设计及电磁兼容设计,并以彩电用开关电源为例,详述了开关电源的设计过程。     

InGaAs dual pin photodiode with minimised series resistance for low noise balanced receivers

Monolithically integrated planar front-illuminated InGaAs dual pin photodiodes (PD) with a series resistance less than 10 Omega have been fabricated for optical coherent receiver application. The PDs exhibit a very low dark current around 100 pA at -10 V, a high quantum efficiency (over 90%) and a 3 dB bandwidth of more than 10 GHz. The photosensitive area diameter is 50 mu m/sup 2/, which offers large fibre alignment tolerances. A 2.5 dB improvement of the average input noise current density of an optical front end comprising the dual pin PD and a tuned electronic preamplifier has been demonstrated.<>