Toshiyuki Yakabe

Complete calibration of a six-port reflectometer with one sliding load and one short

A novel method is presented for calibrating a six-port reflectometer using only one sliding load of unknown reflection coefficient and one short as a calibration standard. The calibration procedure is derived from the fact that the Fourier coefficients of the periodic port power ratios corresponding to the sliding load positions are closely related to the six-port system parameters. The unknown reflection coefficient of the sliding load as well as the eleven system parameters at each frequency is determined in the procedure. The validity and utility of the proposed method are confirmed by experiments over the frequency range 8.5-12.0 GHz in 0.5 GHz steps with a rectangular waveguide sliding load and a polished metal standard short. >

Application of a six-port wave-correlator for a very low velocity measurement using the Doppler effect

A new technique is proposed for measuring the Doppler frequency of a moving object by using the six-port correlator. The examination of this new proposal has been done with an object moving at a very low speed. The experiment and simulation results show the target velocity around 0.2 mm/s has been successfully inferred, which proved the validity of the proposed scheme.

Six-port self-calibration based on active loads synthesis

An automatic method for self-calibrating six-port reflectometers is reported in this paper. It is based on the use of an active impedance synthesis system. This self-calibration method allows a completely autonomous operation, reduces measurement errors caused by the frequent connecting and disconnecting of calibration standards, and is suitable for low and high frequencies, where sliding shorts are difficult to manufacture. In addition, it simplifies operation of six-port reflectometers to nonspecialized users. The experimented impedance synthesis presented relies on an in-phase and quadrature vector modulator, and the entire system is computer controlled.

Accurate modeling for drain breakdown current of GaAs MESFET's

Extensive measurements of a drain breakdown current as a function of device bias are reported in this paper. To represent the measured drain breakdown currents accurately, a new modeling function and an equivalent circuit controlled by two voltages are proposed. This model, when integrated into a large-signal analysis program, improves the accuracy of the simulation.

Six-port based wave-correlator

A novel method for calibrating six-port based wave-correlators is reported in this paper. The calibration procedure uses only one phase shifter and offers simple formulas for determining the calibration parameters. Some experiments using a new six-port junction for the wave-correlator at X-band frequency was carried out and the results confirmed the validity and accuracy of the proposed method.

A large-signal switching MESFET model for intermodulation distortion analysis

This paper describes an improved large-signal model for predicting an intermodulation distortion (IMD) power characteristic of MESFETs in switching applications. The model is capable of modeling the voltage-dependent drain current and its derivatives, including gate-source and gate-drain capacitors. The drain current and its derivatives are described by a function of a voltage-dependent drain conductance. The model parameters are extracted from a measured drain conductance versus gate voltage characteristic of a MESFET. This paper also presents a new fully symmetric equivalent circuit for switching MESFETs. The IMD power characteristics calculated with the use of the proposed method are compared with experimental data taken from a monolithic microwave integrated circuit single-pole double-throw switch. Good agreements over the large gate voltages and input power levels are observed.

An X-band MMIC six-port correlator based vector network analyzer

This paper describes an MMIC six-port correlator based vector network analyzer (VNA). The MMIC six-port correlator was fabricated using hybrid couplers and integrated diode power detectors. The performance of the six-port correlator and the constructed X-band VNA was evaluated, and the measurement accuracy was confirmed.

A Vector Network Analyzer Based on Seven-Port Wave-Correlator

A seven-port wave-correlator based vector network analyzer is proposed. The seven-port wave-correlator is a combination of two six-port wave-correlators which share common components. Furthermore, the complex wave ratio measurement accuracy is improved since the input signals can be directly detected by the side-arm ports. A seven-port wave-correlator is fabricated using microstrip branch line couplers. The performance of the wave-correlator and the constructed network analyzer are evaluated, and the measurement accuracy is confirmed.

Six-port wave correlator theory and practical application to RF network analysis

This tutorial lecture is intended to introduce the basic concept and principle of the six-port wave correlator, and to present the latest advancements in its theory and techniques. The lecture starts with some fundamentals on the six-port reflectometer dating back to its first proposal by G. F. Engen. The key feature of the scheme is to measure the reflection coefficient of RF circuits without resorting to heterodyne conversion. This implies a possibility to measurement of S1 1 in both magnitude and phase, free from frequency limitation. Next, the concept is extended to a six-port wave correlator on which we focus from the viewpoint of establishing a new scheme for characterizing the full S matrix, like what can be carried out by vector network analyzers. Finally, we explore some specific microwave applications of the six-port network, such as beam direction finding, Doppler frequency measurement, etc.

Application of six-port wave-correlator for very low velocity measurement using Doppler effect

A new technique is proposed for measuring the Doppler frequency of a moving object by using the six-port correlator. The examination of this new proposal has been done with an object moving at a very low speed. The experiment and simulation results show the target velocity around 0.2 mm/s has been successfully inferred, which proved the validity of the proposed scheme.