20-09-2012, 11:19 AM
LINE REFLECT REFLECT
LRR line-reflect-reflect technique.doc (Size: 284 KB / Downloads: 25)
INTRODUCTION
LRR- LINE REFLECT REFLECT is a new self-calibration procedure for the calibration of vector network analyzers (VNA). VNA measure the complex transmission and reflection characteristics of microwave devices. The analyzers have to be calibrated in order to eliminate systematic errors from the measurement results.
The LRR calibration circuits consist of partly unknown standards, where L symbolizes a line element and R represents a symmetrical reflection standard. The calibration circuits are all of equal mechanical length. The obstacle, a symmetrical-reciprocal network is placed at three consecutive positions. The network consists of reflections, which might show a transmission. The calibration structures can be realized very easily as etched structures in microstrip technology.
Tunnel diodes
These are also known as Esaki diodes. It is a specially made PN junction device which exhibits negative resistance over part of the forward bias characteristic. Both the P and the N regions are heavily doped. The tunneling effect is a majority carrier effect and is very fast. It is useful for oscillation and amplification purposes. Because of the thin junction and shot transit time, it is useful for microwave applications in fast switching circuits.
Transferred electron devices
These are all two terminal negative resistance solid state devices which has no PN junction. Gunn diode is one of the transferred electron devices and which works with the principle that there will be periodic fluctuations in the current passing through an n-type GaAs substrate when the applied voltage increases a critical value i.e. 2-4Kv/cm.
VECTOR NETWORK ANALYZERS
It measures the complex transmission and reflection characteristics of microwave devices. This is achieved by comparing the signal input to the device, with the signal either transmitted through or reflected back from the device. They incorporate very narrow bandwidth receivers tuned to the signal source frequency and give a direct readout of the four coefficients contained in a scattering matrix-the scattering or ‘s’ parameters, each of which has magnitude and phase elements. The network analyzer was controlled by an external personal computer. The raw measurement data have been read out and processed on a computer.
MICROSTRIP LINES
Prior to 1965 nearly all microwave equipment utilized coaxial, waveguide, or parallel strip-line circuits. In recent years microstrip lines have been used extensively because they provide one free and accessible surface on which solid state devices can be placed. It is an unsymmetrical stripline, that is a parallel plate transmission line having dielectric substrate, one face of which is metalised ground and the other(top) face has a thin conducting strip of certain width ‘w’ and thickness ‘t’. Sometimes a coverplate is used for shielding purposes but it is kept much farther away than the ground plane so as not to affect the microstrip field lines. It is also called an open strip line. Modes on microstrip are only quasi transverse electromagnetic (TEM). Thus the theory of Tem- coupled lines applies only approximately.
Microstrip transmission lines consisting of a conductive ribbon attached to a dielectric sheet with conductive backing are widely used in microwave technology. Because such lines are easily fabricated by printed-circuit manufacturing techniques, they have a technical merit. Most microstrip lines are made from boards of copper with a thickness of 1.4 or 2.8 mils. Line width of less than 0.1 is uncommon.
CONCLUSION
LRR technique is a new self-calibration procedure. The calibration circuits are all of equal mechanical length. This is advantageous for the calibration of vector network analyzers, such as, for instance, for applications where the connectors of the analyzers measurement ports cannot be displaced. The robust functionality is confirmed by measurements, and for that the calibration circuits can be realized in microstrip technology. In the LRR method two solutions are there and depending on the realized calibration structures, the appropriate way should be chosen in order to improve the accuracy.
LRR line-reflect-reflect technique.doc (Size: 284 KB / Downloads: 25)
INTRODUCTION
LRR- LINE REFLECT REFLECT is a new self-calibration procedure for the calibration of vector network analyzers (VNA). VNA measure the complex transmission and reflection characteristics of microwave devices. The analyzers have to be calibrated in order to eliminate systematic errors from the measurement results.
The LRR calibration circuits consist of partly unknown standards, where L symbolizes a line element and R represents a symmetrical reflection standard. The calibration circuits are all of equal mechanical length. The obstacle, a symmetrical-reciprocal network is placed at three consecutive positions. The network consists of reflections, which might show a transmission. The calibration structures can be realized very easily as etched structures in microstrip technology.
Tunnel diodes
These are also known as Esaki diodes. It is a specially made PN junction device which exhibits negative resistance over part of the forward bias characteristic. Both the P and the N regions are heavily doped. The tunneling effect is a majority carrier effect and is very fast. It is useful for oscillation and amplification purposes. Because of the thin junction and shot transit time, it is useful for microwave applications in fast switching circuits.
Transferred electron devices
These are all two terminal negative resistance solid state devices which has no PN junction. Gunn diode is one of the transferred electron devices and which works with the principle that there will be periodic fluctuations in the current passing through an n-type GaAs substrate when the applied voltage increases a critical value i.e. 2-4Kv/cm.
VECTOR NETWORK ANALYZERS
It measures the complex transmission and reflection characteristics of microwave devices. This is achieved by comparing the signal input to the device, with the signal either transmitted through or reflected back from the device. They incorporate very narrow bandwidth receivers tuned to the signal source frequency and give a direct readout of the four coefficients contained in a scattering matrix-the scattering or ‘s’ parameters, each of which has magnitude and phase elements. The network analyzer was controlled by an external personal computer. The raw measurement data have been read out and processed on a computer.
MICROSTRIP LINES
Prior to 1965 nearly all microwave equipment utilized coaxial, waveguide, or parallel strip-line circuits. In recent years microstrip lines have been used extensively because they provide one free and accessible surface on which solid state devices can be placed. It is an unsymmetrical stripline, that is a parallel plate transmission line having dielectric substrate, one face of which is metalised ground and the other(top) face has a thin conducting strip of certain width ‘w’ and thickness ‘t’. Sometimes a coverplate is used for shielding purposes but it is kept much farther away than the ground plane so as not to affect the microstrip field lines. It is also called an open strip line. Modes on microstrip are only quasi transverse electromagnetic (TEM). Thus the theory of Tem- coupled lines applies only approximately.
Microstrip transmission lines consisting of a conductive ribbon attached to a dielectric sheet with conductive backing are widely used in microwave technology. Because such lines are easily fabricated by printed-circuit manufacturing techniques, they have a technical merit. Most microstrip lines are made from boards of copper with a thickness of 1.4 or 2.8 mils. Line width of less than 0.1 is uncommon.
CONCLUSION
LRR technique is a new self-calibration procedure. The calibration circuits are all of equal mechanical length. This is advantageous for the calibration of vector network analyzers, such as, for instance, for applications where the connectors of the analyzers measurement ports cannot be displaced. The robust functionality is confirmed by measurements, and for that the calibration circuits can be realized in microstrip technology. In the LRR method two solutions are there and depending on the realized calibration structures, the appropriate way should be chosen in order to improve the accuracy.