Impedance projection based transconductance amplifier

A current feedback technique is proposed to realise the transposition of grounded impedance to a floating impedance or transconductance. This technique, that can be viewed as an impedance projection, also allows one to implement a new current conveyor topology and to extend applications based on transconductance amplification. A theoretical approach of this new technique using a grounded impedance, two classical transconductance amplifiers and one second generation current conveyor only is presented.     

On-wafer determination of impedance of planar 100 GHz double slotantenna

An on-wafer measurement strategy for determining the driving point impedance of a planar 100 GHz double slot antenna is presented. The technique is verified by comparison with a theoretical determination of the antenna impedance     

`Source-pull? technique at microwave frequencies

A technique to produce a variable and controlled source impedance is described in order to evaluate the performance of microwave devices under source impedance variable conditions. The procedure for a systematic error correction is also presented.     

A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element

A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element is presented. The basis for this technique is the theory of minimum-scattering (MS) antennas and, in particular, the interpretation of the mutual impedance between two canonical minimum-scattering (CMS) antennas as the first term in a perturbation series of the mutual impedance of arbitrary antennas. For the computation of the mutual impedance via the CMS approximation this pattern must be continued analytically into the complex domain. However, numerical codes provide radiation patterns only for real observation angles. To overcome this problem, the numerically calculated patterns are expanded in terms of spherical modes and the computation over complex angles is carried out analytically. Numerical results for collinear and linear arrays of parallel electric dipole antennas and rectangular probe-fed patch antennas are presented and a comparison is made with direct calculations using the WIPL-D code. Results presented show the good agreement between the CMS approximation and the WIPL-D code.     

Very low Q-factor impedance measurements using a lock-in amplifier technique†

A technique for very low Q-factor impedance measurements, based on a lock-in amplifier as a vector voltmeter, is presented. Some practical details are discussed. The accuracy of the measurements has been studied by comparison, using a bridge method. As an application, the forward bias impedance of a variety of p-n junction is presented.     

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.     

Low-output-impedance class AB bipolar voltage buffer

A new ±1.5 V class AB bipolar voltage buffer that can drive low load impedance is presented. A current compensation technique is used for achieving a low output impedance, resulting in a large unitary gain bandwidth and low distortion. Simulation results are included demonstrating the circuit performance     

Measurement of the electrical constitutive parameters of materials using antennas

A general technique is presented for measuring the electrical constitutive parameters of a material using a monopole (dipole) antenna. A normalized impedance that is only a function of the dimensionless parameterkh(wavenumber length) is defined for the antenna. The normalized impedance is expressed as a rational function, and the coefficients in this function are determined from a measurement of the impedance in a standard medium. The impedance measured in a material with unknown constitutive parameters is used with the rational function to form a polynomial inkh. The constitutive parameters of the medium are determined from a root of this polynomial. The measurement technique is implemented for a rational function of order three. The constitutive parameters of the alcohol 1-butanol and saline solutions were measured over a range of frequencies using the technique with cylindrical and conical monopole antennas. The measured constitutive parameters are in good agreement with those determined by previous investigators.     

Impedance boosting techniques based on BiCMOS technology

An impedance enhancement technique, based on a combination of bipolar and MOS devices, is presented. The technique uses negative active feedback action to boost the impedance level of a cascode circuit. This technique improves the gain of the conventional folded-cascode BiCMOS amplifier by the loop gain of the feedback loop. The BiCMOS-based impedance boosting circuit, compared to the CMOS version, offers the advantage of higher bandwidth together with higher output current capability. The SPICE simulations of a folded-cascode op amp based on this technique show that a 120 dB DC gain can be achieved. Application of the technique to a transducer resulted in a total harmonic distortion as low as 0.02% with 2 V_p-p input signals and an improvement of more than 10 dB in linearity, with respect to the case where no feedback was used     

A technique for power supply harmonic impedance estimation using acontrolled voltage disturbance

A method for power system impedance estimation is presented. The method employs a power converter to inject a voltage transient onto the supply system. As the technique employs controlled power electronic devices it may be used as a stand alone piece of a portable measurement equipment, or it may be embedded into the functions of an active shunt filter for improved harmonic control. The impedance is estimated through correlation of the measured voltage and current transients. Simulations and experimental results demonstrate the measurement technique is highly accurate and effective     

Analysis of a probe-fed short-circuited microstrip antenna

The input impedance of a probe-fed short-circuited microstrip antenna (SCMSA) is presented. The electric field expression under the microstrip patch by using the Wiener-Hopf technique is used and the electromotive force (EMF) method is applied. Analytical and experimental results for the impedance show the dependence on the dimensions and frequency     

Characterization of Packaged Microwave Diodes in Reduced-Height Waveguide

A technique for the measurement of package parasitic and equivalent-circuit parameters of microwave semiconductor devices at the frequency of operation is presented. In this method a two-port coupling circuit is found which transforms the impedance measured in rectangular waveguide to the terminals of the equivalent circuit used to represent the semiconductor device. This approach combines known properties of radial transmission lines and of impedance measurement in the TE/sub 10/-mode full-height waveguide to obtain an analytical referencing technique for a diode mounted across a reduced-height waveguide. Application of this technique is illustrated by measurements of several varactor diodes.     

The traveling-wave linear antenna with nondissipative loading

An approximate theory for a doubly impedance loaded, traveling-wave linear antenna is presented. The distribution of current on the thin, cylindrical antenna is determined approximately in terms of its dimensions and the impedance and position of the lumped impedance loading. From this result, the optimum loading required to excite an outward traveling current wave along most of the cylinder is determined. Significantly, it is indicated that a purely reactive loading may be utilized if its location is properly chosen. Expressions for the input impedance and radiation fields of the traveling-wave antenna are presented. An experimental study is made of a traveling-wave cylindrical antenna utilizing a purely nondissipative loading. Numerical results from the theory are compared with experimental data, and an excellent agreement is noted. The technique described may be utilized to realize a high-efficiency traveling-wave antenna.     

Coplanar waveguide fed wideband slot antenna

A new design for a coplanar waveguide (CPW) fed slot antenna is presented. The impedance matching and the radiation characteristics of this structure were studied using the method of moment technique. This antenna has an impedance bandwidth (for a VSWR<2) of 49% and a radiation bandwidth of 42% about its 4.8 GHz centre frequency, compared to the 12-20% impedance bandwidth of the standard CPW fed slot antenna. The cross-polarisation in both the principle planes is at least 20 dB below co-polarisation across the entire bandwidth. Simulated and measured results of the antenna are presented. This wideband antenna has significant applications in wireless technologies     

A bandwidth enhancement technique for mobile handset antennas using wavetraps

A novel technique for enhancing the impedance bandwidth of wireless terminal antennas is presented. By introducing resonant short circuit transmission lines to the long sides of the chassis edges, an effective electrical shortening of the terminal ground plane is achieved. This effect has been used to realize terminal ground planes with resonant lengths at high frequencies, such as GSM 1800/1900 MHz or UMTS 2 GHz, thereby extending the impedance bandwidth. The proposed technique has been validated by simulations and measurements. Three typical applications are presented where the introduction of wavetraps improves the bandwidth and/or in-band performance.     

An efficient method for analysis of arbitrary nonuniformtransmission lines

The analytical solution of an ideal linear varied nonuniform transmission line (LNTL) has been obtained and the exact linear two-port ABCD matrix of LNTL has been given correctly for the first time. By using cascaded LNTL sections to approximate an arbitrary characteristic impedance profile, a new technique has been presented in this paper for analyzing an arbitrary nonuniform transmission line (NTL). The technique is far better than the conventional technique in terms of the computational accuracy and intensity since it uses a piecewise-linear characteristic impedance profile in place of the stepped profile used by the conventional technique. Several numerical examples have been given to demonstrate the method     

Analysis and design of impedance-transforming planar Marchandbaluns

A technique for designing impedance-transforming baluns is presented in this paper. It is based on the Marchand balun with two identical coupled lines. By varying the coupling factor of the coupled sections, a wide range of impedance transforming ratios can be achieved. In addition, a resistive network added between the balun outputs is proposed to achieve balun output matching and isolation. Microstrip baluns, matched at all ports, for transforming from a 50-Ω source impedance to 40-Ω as well as 160-Ω load terminations are realized to demonstrate the technique     

Efficient technique for solving nonlinear mixer pumping problem

An efficient technique for solving the nonlinear mixer pumping problem is described. The technique can be applied to mixer configurations where the impedance presented to the diode at the local oscillator frequency and its harmonics are known.     

天线与非绝缘型复合材料载体的共形技术

提出了天线与非缘绝型复合材料载体共形的一种工作模式,并在理论上用有限元法对其进行了研究,在此基础上用有限元法计算了载体材料特性不同时天线的阻抗特性和辐射特性,最后给出了一个工程设计实例。     

Calculation of the characteristic impedance of TEM horn antennasusing the conformal mapping approach

A new conformal mapping technique for determining the characteristic impedance of TEM horn antennas is presented. The original work by Carrel [1958], on noncoplanar fin antennas of this type, predicts incorrect impedance values which do not agree with experimental results. The present paper discusses fully the source of the error in Carrel and details the successive mappings involved in the new approach. Verification of the method is provided by experimental results and by comparison with an alternative numerical technique