Martin Randus

A simple method for extreme impedances measurement - experimental testing

This paper directly follows and extends, where a novel method for measurement of extreme impedances is described theoretically. In this paper experiments proving that the method can significantly improve stability of a measurement system are described. Using Agilent PNA E8364A vector network analyzer (VNA) the method is able to measure reflection coefficient with stability improved 36-times in magnitude and 354-times in phase compared to the classical method of reflection coefficient measurement. Further, validity of the error model and related equations stated in are verified by real measurement of SMD resistors (size 0603) in microwave test fixture. Values of the measured SMD resistors range from 12 kOmega up to 330 kOmega. A novel calibration technique using three different resistors as calibration standards is used. The measured values of impedances reasonably agree with assumed values.

A Method for Direct Impedance Measurement in Microwave and Millimeter-Wave Bands

A novel method for direct impedance measurement using a common vector network analyzer (VNA) is introduced and experimentally verified. In commonly used methods, the input impedance or admittance of a device-under-test (DUT) is derived from the measured value of its reflection coefficient causing serious inaccuracy problems for very high and very low impedances. The proposed method makes it possible to measure a quantity that is, in the ideal case, directly proportional to the value of input impedance or admittance of the DUT, enabling accurate and stable measurement of impedances that are extremely different from the common 50-Ω reference impedance. The method can significantly reduce errors caused by the VNA.

A novel method for direct impedance measurement in microwave and mm-wave bands

A novel method for direct impedance measurement using a common vector network analyzer (VNA) is introduced. In commonly used methods impedance or admitance of a device under test (DUT) is derived from measured value of its reflection coefficient causing serious accuracy problems for very high or very low impedances. The proposed method makes possible to measure quantity directly proportional to the value of the impedance or admittance of the DUT. This enables us to accurately measure even impedances that are extremely different from value of the 50Ω reference impedance. The method can also significantly reduce effect of uncertainties of the VNA. A suitable calibration technique is suggested and fully mathematically described. The concept of the new method was verified by software simulation.

Generalized method for broadband measurement of extreme impedances

This paper describes generalization of a method for extreme impedances measurement published in [1] and [2]. The transmission coefficient measured by a vector network analyzer (VNA) results from summation or difference between reflection coefficients of a reference and measured impedance. The resulting signal is then amplified by an amplifier in order to gain very high resolution of impedances. Two types of wideband passive 4-port network solutions were designed and tested. With current components frequency band 0.7–10 GHz was achieved.

Calculation of maximal applicable gain for the generalized and the direct method for extreme impedances measurement

A mathematical approach for determining the maximal applicable gain of amplifiers, that are used in two recently introduced methods for measurement of extreme input impedances using a common vector network analyzer (VNA) — the generalized method and the direct method — is presented. These two measurement methods exhibit outstanding measurement sensitivity for extreme impedance values — impedances significantly higher or lower than the 50Ω reference impedance of common measurement systems. The measurement sensitivity is better when gain of the used amplifiers is higher. However, the gain is limited by nonlinearity of the amplifiers and the receivers of the vector network analyzer. Therefore, the gain calculation is derived to make possible to fully exploit the capabilities of the measurement methods without loosing accuracy due to nonlinear effects. An example of calculation for one experimental setup is also presented.

A procedure for measurement of s-parameters and eye-diagram of backplane using two-port VNA

A procedure for measurement of eye-diagram of a backplane based on single-ended two port s-parameters was designed and experimentally verified. Eye-diagram was derived using impulse response corresponding to calculated differential s-parameters of backplane pair lines. FCI AirMax VS connectors were used to connect the backplane. The procedure was verified in frequency band up to 5 GHz and transmission rate 1.25 Gbits/s.

Measurement of extreme impedances

This paper provides an experimental verification of a novel method for measurement of extreme impedances which was theoretically described earlier. In this paper experiments proving that the method can significantly improve stability of a measurement system are described. Using Agilent PNA E8364A vector network analyzer the method is able to measure reflection coefficient with stability improved 36-times in magnitude and 354-times in phase compared to the classical method of reflection coefficient measurement. Further, validity of the error model and related equations stated in the earlier paper are verified by real measurement of SMD resistors (size 0603) in microwave test fixture. Values of the measured SMD resistors range from 12 kΩ up to 330 kΩ. A novel calibration technique using three different resistors as calibration standards is used. The measured values of impedances reasonably agree with assumed values.

Design of SMA 50 Ω Load Using 3D EM Field Simulator: Comparison with Reality

The subject of this paper is to provide a comparison of 3D EM field simulation results of 0603 size SMD resistors with corresponding real data obtained by precise vector measurements. The simulated results were obtained by 3D EM field simulator CST Microwave Studio with time-domain solver. The comparison is shown on a design of an optimized 50 Omega load composed of a common SMA flange connector and a set of 0603 size SMD resistors. The resistors are soldered between the inner conductor of the coaxial SMA connector and the flange. Several arrangements of the SMD resistors ranging from single-resistor arrangement to four-resistor pattern as well as different orientation of the resistive layer of the SMD resistors are discussed. Step discontinuity of the inner conductor of a real SMA connector is subsequently also involved in 3D EM field simulation and these results are compared with precise vector measurements.

Broadband Medium-Power Transistor Amplifier 12-18 GHz

A medium-power two-stage transistor microwave amplifier for frequency band of 12 to 18 GHz using eight packaged HEMTs has been designed and developed. Gain over 16 dB, output power P-1 db > 22 dBm and return loss better than 10 dB both on the input and output has been achieved in the whole band. The input and output are DC grounded to protect the amplifier from electrostatic discharge (ESD). Mutually linked AWR microwave office circuit simulator, 3D EM field simulator CST microwave studio and precise small-signal s-parameters vector measurements were used for the design.