Comment on the equivalent circuit of a receiving antenna

For original article see Van Bladel (IEEE Antennas Propag. Mag., vol.44, no.1, p.164-5, 2002). The author comments on the above article in the context of a long-standing paradox that arises when an equivalent circuit is used to characterize the electrical properties of a receiving antenna.     

Miniloop antenna operation and equivalent circuit

The equivalent circuit and principles of operation of a miniloop antenna (i.e., a larger, tuned outer loop inductively coupled to a smaller inner loop) are established and verified. Both classical and moment methods for determining the circuit parameters are presented and compared. Based on the equivalent circuit, the features of the miniloop are contrasted to those of the single, outer loop as a system element, where factors such as signal bandwidth, efficiency, and problems of matching to the transmission line are considered.     

An equivalent circuit for the tee-fed slot antenna

In this paper an equivalent circuit is developed for a tee-fed slot antenna, and the equation describing its input impedance is derived. The input impedance for several antennas is computed and compared with experimentally obtained data.     

Limitations of the Thevenin and Norton equivalent circuits for a receiving antenna

The investigation carried out in this paper was stimulated by a recent paper published by Love (2002), in which the appropriateness of the use of the Thevenin and Norton equivalent circuits for a receiving antenna was questioned. A review of the available literature led to the conclusion that the limitations inherent in the Thevenin and Norton equivalent circuits had not been adequately examined, and this led to the investigation that is reported on in this paper. The Thevenin and Norton equivalent circuits are useful in the reduction of the equivalent circuit for a transmitting-receiving antenna system to simpler networks that facilitate the evaluation of the received power. One finds in the literature that the calculated power dissipation within these equivalent circuits is often equated to the reradiated and scattered power from the receiving antenna. Such calculations are not correct, because power dissipation in the network from which the Thevenin and Norton equivalent circuits were obtained cannot be made using the Thevenin and Norton equivalent circuits. However, as we will show, the Thevenin and Norton equivalent circuits can be used to find a reradiated electromagnetic field that is a part of the total field scattered by a receiving antenna. As part of the derivation of this new result, we develop a derivation of the Thevenin and Norton equivalent circuits from the basic principles of uniqueness and superposition applied to electromagnetic fields.     

Comment on "Limitations of the Thevenin and Norton equivalent circuits for a receiving antenna"

The author comments that Collin (see IEEE Antennas and Propagation Magazine, vol.45, p.119-124, 2003) points out some of the attributes of the constant-power equivalent circuit for a receiving antenna. However, he disagrees with the writer's statement that the internal power dissipated in the circuit can be equated to the reradiated, or scattered, power from the antenna. A reflector antenna is not at all like the slightly lossy dielectric bodies and the perfectly conducting targets treated in the classical literature. It is a highly "lossy" structure that absorbs nearly all the power incident upon it.     

On the equivalent circuit representation of the slittedparallel-plate waveguide filled with a dielectric

An investigation of the equivalent π circuit representation for the transverse slit in the wall of a transverse electromagnetic (TEM) parallel-plate waveguide is presented. For the narrow slit, approximate analytic expressions for the equivalent circuit parameters are given in terms of the centerline representation and, for the arbitrarily width slit, the equivalent circuit parameters are considered by the method of moments in terms of both the centerline representation and edge representation, and various characteristics of the equivalent π admittance circuit representation are discussed. A critical look is taken at the validity of the previous model of th E-plane gap coupling between two rectangular microstrip patch antennas, and the improved model is considered for the narrow slit (gap) width case     

Remarks on "Comments on the limitations of the Thevenin and Norton equivalent circuits for a receiving antenna"

Collin (see IEEE Antennas and Propagation Magazine, no.45, p.119-124, 2003) remarks that Love (see IEEE Antennas and Propagation Magazine, vol.45, no.4, p.98-99, 2003) has misinterpreted his. In the paper under discussion, he did not discuss the efficiency of a receiving antenna or give any comment on the maximum efficiency a parabolic receiving antenna could have. Love's statement that it appears that Collin believes most receiving antennas cannot have an efficiency greater than 50% is speculation on his part.     

The equivalent circuit of a joining two-port

An equivalent circuit of a joining two-port is proposed. The two-port provides for the stability and convergence of the results of semi-natural modeling of a partitioned linear dynamical system to the results of numerical modeling of the integral original system. The functional properties of the obtained two-port are investigated. It is shown that the obtained results are coupled with the well-known results in the decomposition methods and system modeling by parts. It is supposed that the obtained two-port is one of the simplest hypostases of the Poincare–Steklov operator.     

Origins of the equivalent circuit concept: the voltage-source equivalent

This paper describes the development of the voltage-source equivalent circuit. A subsequent paper concerns the current-source equivalent and summarizes the story. The formal roots of equivalent circuits are Ohm's Law, Kirchoff's Laws, and the Principle of Superposition.     

Origins of the equivalent circuit concept: the current-source equivalent

The voltage-source equivalent was first derived by Hermann von Helmholtz (1821-1894) in an 1853 paper. Exactly thirty years later in 1883, Leon Charles Thevenin (1857-1926) published the same result, apparently unaware of Helmholtz's work. The generality of the equivalent source network was not appreciated until forty-three years later. Then, in 1926, Edward Lawry Norton (1898-1983) wrote an internal Bell Laboratory technical report that described in passing the usefulness in some applications of using the current-source form of the equivalent circuit. In that same year, Hans Ferdinand Mayer (1895-1980) published the same result and detailed it fully. As detailed subsequently, these people intertwine in interesting ways.     

On the validity of a new extrinsic equivalent circuit including noise of HEMTs required for millimeter wave circuit design

In this paper, we propose a reliable extrinsic equivalent circuit of high electron mobility transistor (hemt) to determine both the S and noise parameters in the millimeter wave range from characterizations performed below 40 GHz. Only three extrinsic elements have to be determined instead of eight (at least) in the case of the conventional equivalent circuit. We show the validity of the proposed extrinsic equivalent circuit by S parameters and noise figure measurements up to W band (75-110 GHz).     

On the relationship between the transmitting and receiving properties of an antenna

The response of a linear, passive antenna in free space to an incident plane wave is related to its far-field radiation in the reverse direction bybar{h}^{r}=bar{h}^{t}. The vector effective heightbar{h}^{r}characterizes the voltage across the open-circuit antenna terminals induced by an incident plane-wave field, and the correspondingbar{h}^{t}characterizes the far-field radiation of the antenna when driven by a current injected into the same terminals. This relationship, which is shown to follow from the well-known reciprocity principle, both includes phase and makes mathematically explicit the polarization relation involved in the identity of the transmit and receive patterns of an antenna.     

New skin-effect equivalent circuit

An accurate equivalent network for modelling the skin-effect is presented. No specific approximation in the frequency behaviour is used. The method is therefore applicable whatever the geometry of the microstrip line, especially when the thickness is greater than the width. The frequency-dependent parameters of a transmission microstrip line as well as the attenuation are simulated using SPICE.<>     

Noise equivalent circuit of a semiconductor laser diode

The noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and modulation characteristics of a laser diode combined with electronic components. The intrinsic junction voltage noise spectrum and the light intensity fluctuation of a current driven laser diode are calculated as a function of bias current and frequency.     

Current distribution on a receiving dipole antenna

The current distribution on a receiving dipole antenna is dependent on its feed-point load impedance. Calculations based on the modified King-Middleton approximation have been made of the distribution for antenna half lengths of 0.1, 0.2, 0.25, and0.3 lambda. Representative values of the antenna load impedance, resistive, capacitive, and inductive, are used to show their effects on the antenna current distribution.     

一种紧凑型双圆极化有源接收天线设计

设计了一种S波段紧凑型双圆极化有源接收天线,该有源接收天线将微带贴片天线与90°混合电桥、低噪声放大器集成设计,既实现了有源天线的整体小型化又提高了各器件间的连接效率;并通过背馈玻璃绝缘子和一种半差分的方式馈电,在改善微带贴片天线方向图对称性的同时,简化了传统差分式馈电的复杂结构.仿真和实测结果表明,该有源接收天线在2.2~2.3 GHz内端口驻波比小于1.47,噪声系数小于0.73 dB,主瓣内轴比小于2.4 dB,G/T值大于-13.9 dB/K,与已有公开文献的有源接收单元天线相比,在保持结构紧凑的同时,其G/T值有较大幅度提升.     

On the equivalent generator voltage and generator internal impedance for receiving antennas

In the circuit model of receiving antennas, it is commonly assumed that there is no coupling between the load and the equivalent generator. Then the equivalent generator voltage is assumed to be the open-circuit voltage and the generator internal impedance is assumed to be the input impedance in the transmitting mode. In this investigation, these voltages and impedances are computed numerically for cylindrical antennas. From the numerical results, it is found that these two assumptions are not correct individually. However, it is found that the uncoupled-circuit model can yield correct results for the load current. Further, the validity of the uncoupled-circuit formula of the load current is proved by using the reciprocity theorem. Thereby, it is concluded that the uncoupled-circuit model can yield the correct result for the load current, but the open-circuit voltage and the input impedance are not at all identical to the equivalent generator voltage and the generator internal impedance, respectively.     

The terminal voltage of a receiving dipole antenna

The terminal voltage of a receiving dipole antenna is dependent on the antenna current distribution which in turn is dependent on its feed-point load impedance. Computed results of the terminal voltage are presented for dipole antenna half-lengths up to1.0 lambda. Representative values of the antenna load impedance, resistive, inductive and capacitive, are used to show their effects on the terminal voltage.