Zbynek Skvor

A novel vector network analyzer

A calibration procedure for perturbation two-port vector network analyzer is presented. It consists of a variable perturbation two-port placed between a device under test and a scalar network analyzer. A measured vector reflection coefficient is determined on the basis of amplitude only readings. A full correction of systematic errors is possible. The new principle was experimentally confirmed in the frequency band up to 14 GHz.

Experimental verification of a distributed amplifier oscillator

New electronically tunable oscillator arrangement, based on a distributed amplifier, has been verified experimentally. The device possesses broadband, continuous and instant tuning and a good harmonic purity of the output signal. It is found suitable to be used in MMICs.

The UWB Amplifier 3.1-10.6 GHz

The general principle of an ultra-wideband (UWB) amplifier design in the planar structure using the common available monolithic amplifier is proposed in this paper. The structure of the amplifier is designed in order to accomplish the conditions of the transmission of UWB impulses (flat gain and constant group delay over FCC approved frequency band) with a minimum distortion. The roll-of stage is used for the compensation of the declining gain and biasing of the monolithic amplifier. The demonstration of the distortion and the assessment criteria of distortion are also presented. The experimentally manufactured amplifier demonstrates a gain of 7.1plusmn0.6 dB and a group delay variation of 7 ps from 4 to 9.3 GH and 25 ps over the whole band.

Hidden problems in precise calibration on microstrip

A study of calibration problems on microstrip with respect to interaction of electromagnetic fields around SMA to microstrip launcher and microstrip short was carried out in frequency band up to 26 GHz. Omni Spectra SMA to microstrip launcher, 50 Omega microstrip line on Arlon CuClad 223 0.508 mm thick substrate and microstrip shorts with reflective wall above the upper side of substrate as a calibration elements were used for simulations in CST Microwave Studio. Strong influence of dimensions of shorts and distance between the shorts and the launcher on simulated calibration data was observed. Reasonable dimensions of the short and the distance between the short and the launcher making possible correct precise calibration were determined.

Evaluation and Correction of Cable Phase Stability in High Frequency Near-Field Measurement

In case of the near-field measurement, the radiated field by the measured antenna is received by two- dimensional scanner in defined points. During the process of the field scanning, the cable between the VNA and the scanner antenna is moved and its parameters are changed. This paper deals with the evaluation of the cable parameters changes. The dominant change is represented by the phase deviation of the cable transmission coefficient. The paper also proposes the method of the cable errors correction and evaluation of the correction method efficiency. The correction can be based on the full calibration at the reference plane of the scanner antenna feeding in all points of scanned field. The aforementioned approach is more time consuming than the proposed method, where the full calibration is performed in one selected point, while the correction of the cable parameters is based on the estimation based on the input impedance of the cable loaded by the scanner antenna.

Assembly influence on S-parameters of packaged transistor

A proper analysis of the assembly influence on small-signal parameters of packaged transistor has been done. The S-parameters differences caused by assembly change are computed using the standard method and three new proposed methods that exploit 3-D model of the transistor package. The differences, accuracy and suitability of these methods are discussed. The results were verified experimentally for particular packaged transistor in frequency range 45 MHz-18 GHz.

A now concept of PTP vector network analyzer

A new concept for vector network analyzers design based on a perturbation two-port (PTP) is presented. The approach uses redundant states of the PTP. The best states of the PTP for a certain place in Smith chart and frequency are chosen to determine a reflection coefficient with minimum uncertainty. Four criteria for the selection are designed. The criteria were tested on measured parameters of different states of the PTP. Significant improvements in PTP bandwidth and uncertainty of measured data were achieved. Summary Six-port vector network analyzers (VNA) are well known for decades, [1]. Similar concept using only a scalar network analyzer and a PTP was designed in [2], where only a basic principle was designed and experimentally verified using a PTP with properties far from optimum. No recommendations for the structure of the PTP were given. Some suggestions for an optimum three state PTP can be found in [3], yet the states of the PTP are unpractical for a realization and are suitable only in a narrow frequency bandwidth. The main demand in the PTP design is to realize optimum states valid on the whole Smith chart in wide frequency band. These demands can be hardly satisfied with any minimum 3-states PTP. The solution is a new concept of the PTP vector network analyzer based on redundant multi-state PTP. It releases the demands on PTP so that they must be satisfied only in a part of Smith chart. The concept can be summarized into three key steps. • over-determination of measured data using more than three minimum states of the PTP • approximate determination of measured reflection coefficient in Smith chart using proper three PTP states • state the measured reflection coefficient more precisely applying the best PTP states determined in given frequency in corresponding part of Smith chart by proper test criteria The purpose of this paper is to present proper criteria for the PTP state selection and a new circuit solution for individual states of the 7-state PTP. Theory A typical arrangement of the new PTP vector network analyzer with seven switched PTP states is presented in Fig.1. P m 1 PTP 7 PTP 2 PTP 1

Precise microwave measurement of liquid level

A simple interferometric waveguide setup has been developed, enabling for precise distance measurement of liquid level. Total reflection from the liquid surface is not necessary. For the most common case of lossy liquids, reflection phase must be determined properly. This may be accomplished by the use of a waveguide short for calibration. The setup was tested in measurement of water level. Resolution of the order of micrometers was achieved in X-band.

Contactless distance measurement method

A new method capable of contactless distance measurement with high resolution has been proposed. The method is intended to measure distance differences smaller than one half of a wavelength. First experimental results are reported. The method is based on precise phase evaluation of signal reflected by the surface whose distance is measured. This is achieved using interference between the reflected and reference signals. Micrometer resolution at 10 GHz can be expected.

7 state PTP for vector network analyzer

A new, 7 state switched perturbation two-port (PTP) for vector measurement based on scalar measurement only was designed and realized in microstrip structure using PIN diodes. The structure was experimentally tested by means of vector measurements of different impedances in frequency band with relative bandwidth of 2.5 octave. Good agreement with data obtained using a precise vector network analyzer was achieved.