Ultra-Fast Noise Parameters Measurements

Introduction

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Noise occurs naturally in any active device or circuit, and limits the minimum levels of useful signals. With a cell phone, for example, it can interfere with a weak signal, and interrupt a call. Therefore, it is important to design circuits to minimize the effects of noise. To do this, the noise must be quantified and measured in the form of noise parameters, comprised of Fmin, Gamma,opt (mag and phase), and Rn. Note, Noise Figure is a commonly referenced parameter when discussing LNAs, and most often refers to the 50ohm noise contribution of a device.

Ultra-Fast Noise Parameters

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A new ultra-fast noise parameter measurement method is able to improve overall calibration and measurement time by a factor of 100X-400X, bringing measurements that could once take tens or hundreds of hours to tens of minutes. The new method has two key features that contribute to the breakthrough speed improvement: 1) The tuner is characterized with one set of states (physical tuner positions) that are selected to give a reasonable impedance spread over the frequency band of interest; and 2) the noise power measurement is swept over the frequency range at each state, so that the tuner only moves to each position once. This takes advantage of the fast sweep capability of modern instruments, as well as saving time by minimizing tuner movement.

The new noise parameter measurement method provides two orders of magnitude speed improvement. It also produces data that is smoother and has less scatter than the traditional method. The fast measurement speed eliminates temperature drift, and using a VNA with an internal noise receiver simplifies the setup and makes it much more stable and consistent. The much higher speed makes it practical to always do a full in-situ calibration to minimize errors, and to measure more frequencies to get a better view of scatter and cyclical errors, and to be able to use smoothing with more confidence. The higher frequency density also enhances accuracy by reducing shifts due to aliasing.

The 50ohm Noise Figure of a device can be directly measured using the Noise Parameter system, or extrapolated from the Noise Figure contours. Direct measurement is achieved by using an impedance tuner to present exactly 50ohm to the DUT and measuring the associated noise figure (note, the tuner can correct for the non-50ohm system impedance normally presented without a tuner). Noise Figure extrapolation is a standard function within a noise parameter measurement system and uses mathematically determined contours to calculate the expected Noise Figure contribution at 50ohm.


Measured noise parameter data with 73 frequencies using the new method, no smoothing applied, showing Fmin (red), rn (blue), and Associated Gain (purple).


Typical 8-50 GHz single-sweep measurement using a Maury MT7553B01 Noise Receiver Module and a Maury MT984AU01 Automated Tuner with Agilent's PNA-X.

Typical setup for 0.8-18 GHz noise parameter measurements using a Maury MT982BU01 Automated Tuner with the Agilent PNA-X Network Analyzer.


Typical setup for 8-50 GHz noise parameter measurements using a Maury MT7553B01 Noise Receiver Module and a Maury MT984AU01 Automated Tuner with the Agilent PNA-X Network Analyzer.

Application Notes and Data Sheets

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• 5A-042 A New Noise Parameter Measurement Method Results in More than 100x Speed Improvement and Enhanced Measurement Accuracy
• 5C-084 Setting Up ultra-Fast Noise parameters Using the Agilent PNA-X
• 5C-085 Using an Impedance Tuner and Noise Receiver Module to Extend the Agilent PNA-X to 50 GHz Noise Parameters

• Maury Application Notes Library Maury Software and System Application Notes.

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Vector-Receiver Load Pull Measurements

Vector-receiver load pull is a modern and efficient methodology for load pull measurements. Low-loss couplers are placed between the tuners and device-under-test and are connected to a vector receiver such as a VNA. Doing so allows the a- and b-waves to be measured at the DUT reference plane in real-time, presenting vector information not normally made available. Vector-receiver load pull allows the direct measurement of actual impedances presented to the DUT without any assumptions of pre-characterized tuner positioning or losses. The delivered input power is derived from the a- and b-waves with incredible accuracy, which results in properly- defined power added efficiency. Output powers at each frequency, fundamental and multiple harmonics, are made available, as are multi-tone carrier and intermodulation powers. Time-domain NVNA measurements are easily implemented using appropriate hardware (Agilent PNA-X or VTD SWAP).

SOURCE PULL CONVERTER

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Because the a- and b-waves of the DUT are measured at the DUT reference plane, it is possible to measure the large signal input impedance of the device. With this information and through a patent-pending technique, it is possible to simulate the effect of matching the source of the device without having ever varied the source impedance. This "virtual source matching" is highly reliable at even extremely mismatched conditions, and allows for simulated source contours to be drawn. Trade-offs between maximum gain, efficiency and other parameters can be viewed in real-time without multiple source pull load pull iterations.

Typical setup for performing VNA-based load pull measurements using two Maury MT982-series Automated Tuners driven by the Maury IVCAD Advanced Measurement and Modeling Software


Typical vector-receiver load pull block diagram

The uses and Importance of Stub Tuners

There are various devices used to modify the impedance factor in various subsystems and devices used for calibration. One of such devices is Tuner that are used in various signal operating networks and related systems. These tuners are very useful in calibrating techniques where the impedance of the sources are to be adjusted to set with precise tuning of the frequencies. There are various types of tuners like as the Stub tuner and Slide screw tuner. These are different in the design but perform on the same basics of working. These tuners are used to measure the impedance settings and modify them as per the requirements.

The most important use of the stub tuner is to set the impedance matching which is critical for RF operation systems. These are widely used in carrying out the operations like as Load pull and noise measurements for both production and laboratory usages. The stub tuner is best suitable in the cases where continuous use of the tuner is not required. This is quite effective and provides the best alternative for other tuning devices. There are two types of stub tuners; dual stub tuner and multiple stub tuners. These tuners are basically impedance transformers. The stub tuners provide the various impedances in the given systems that are to be optimized. It is used to provide a variable shunt in the coaxial transmission susceptances situated at fixed distance. A stub tuner consists of the two or more short-circuited, variable length lines (stubs) connected at right angles to the primary transmission line. These tunable shorts are operated on the half wavelength at the minimum operating frequency.

These tuners provide the system to correct the phase and amplitude standards at the same time.  It is very useful to adjust the reflection coefficient of the phase and amplitude simultaneously. The distance between the stubs is the factor to specify the range on the impedance that the stub tuner can match and tune. These tuners re useful but can be misleading because of the unpredictable reflection behaviors in case of the multiple stub tuners. The multiple stub tuners cannot be used to match the amplitude and phase simultaneously. The multiple stub tuners are not easier to operate as they can create problems in effective reflection management.

There are various uses of the stub tuners that make them useful over other devices in Load Pull. While carrying a load pull the measure is recommended to be set at the maximum or approximately close to it. This is almost impossible in practical cases because of the power loss in the tuners itself therefore it becomes difficult to get the optimum net result at DUT reference plane.  However, if the mismatch range is not very high (5transistors or higher) the chances for a reasonable accuracy are high and falling below it becomes difficult to search around the optimum.

This method is useful and effective over the other methods as it is cost effective and don’t give negative effects like as self heating and transient trapped charges. The factors like as self heating and trapped charges can be producing misleading results of the tests. The pulsed IV testing process delivers the accurate data on the devices needed to improvise the devices. This is best suitable to measure the test results in RF devices like as the transistors, switched and amplifiers relating to nonlinear responses.

There are two types of test methods used for testing in the pulsed environment; i.e. pulsed IV sweeps and transient (single pulse) testing method. If the DUT is associated with the double channels including pulse source and a pulse measurement system the results can be recoreded easily. This makes it very cost effective.

The results produced under different biased conditions for the Pulsed IV measurement sweeps carried out in pulsed system can be easily compared with the results produced in DC tests. The graphs of the curves produced by showing drain voltage VD and drain current ID behavior under different bias conditions are similar to that of the pulsed testing.

The basics of the pulsed IV testing are set to provide the pulses with non-zero value for both gate and drain voltage, often referred to as the operating point or quiescent (q) point. This technique is very useful for condition and based on the applicability of the low-duty-cycle pulse to the DUT. This helps in avoiding the self-heating and carrier-trapping effects that can deviate the exact results. The method of  load pull testing is used to support the test results of overall measurements carried for a device.

The pulse width that is used in this technique ranges from milliseconds to nanoseconds.  The selection of the pulse widths depends upon the DUT, materials and test parameters. The standard source-measure units (SMUs) are usually used to measure the results on millisecond pulse widths. The shorter pulses (microseconds to nanoseconds) are generally more effective for avoiding self heating and charge-trapping effects. Therefore, short-pulse pulsed I-V testing of RF transistors generally allows the creation of more useful models.

Cables and Connections are Co-related to Each with Maximum Outputs to Generate

An RF cable is an option for cable that caters to a variety of connection use. Only where there is no option to use an RF cable is available, other sorts may be used. It is used for connecting the aerial to the TV and an RF cable is used to attach gadgets to gadgets, for example a TV with a VCR. A cheaper quality may be used for this purpose. For other purposes, a better quality must be preferred. The RF Cable Assembly, the Microwave cable assembly or a phaseflex cable assembly can also be used for the specified purpose. There are at times demanding conditions of the task at hand or where The RF Cable assembly, the Microwave cable assembly or a phaseflex cable assembly is required. There may be a need for flexing and there may be several levels of temperatures that The RF Cable assembly, the Microwave cable assembly or a phaseflex cable assembly would have to hold. In these cases a good manufacture is the best option. There are many manufacturers available for the manufacturing and assembling of these so many kinds of cables. There are manufacturers giving all kinds of guarantees.

The various claims however are to be taken logically and objectively. After all it is a matter of spending money and an investment you don’t want to get into again and again. The consistency in performance is the achievement that should be seen. The product with more consistency is the one that may be called as more reliable too. For example if the use of a gadget requires frequent connecting and disconnecting, the wires and assemblies should be strong enough. The cables need to be reliable. For some gadgets and works, these requirements are increased. For example in the case of VNA, the VNA Cable has to be so. The differences in results of ordinary and customized VNA cables are obvious. This has been tested and verified numerous times. Using high performance VNA Cable can show a major shift in results obtained.  Another kind may be the phase stable cable. This kind i.e. phase stable cable requires to be as much in line with the same requirements as of any good reliable and stable cable.

The unstable cable has damaging effects of systems, system performance and on the measurements. The accuracy of measurement cannot be guaranteed by low performance cables. So the phase stable cables must be of a good quality for accuracy.

Cables and Assemblies of Cables React Quickly with Great Results

The RF is cable is a cable that offers easy use. The RF cable can slide into the socket and pulled out easily. There are other versions or types of RF cables too. These types can include screwing up the cable and so on. The type of the screw may be more secure, but it is also of difficult use and not convenient. The best point in using the RF cable is to have a cable that is not so expensive. These are affordable cables. There are qualities of certain nature in affordable prices too.   There are the other forms of cables too. There are also the assemblies of cables.  There is the RF Cable assembly, the Microwave cable assembly or a phaseflex cable assembly. The RF Cable assembly, the Microwave cable assembly or a phaseflex cable assembly is made by making an assembly of the wires.

The assembly of wires can be made according to specific designs and so on. The design diagram or the plan to make the RF Cable assembly, the Microwave cable assembly or a phaseflex cable assembly is made according to the specifications required or needed. The RF Cable assembly, the Microwave Cable Assembly or a phaseflex cable assembly may be different kinds, but the basic structure of design is usually the same. The cables are arranged and cut according to the size that is needed. These are then joined together and the lose metal ends are connected. These are then assembled on a board to make an assembly. Finally the assembly is sleeved to protect it. These assemblies are also designed for safety purposes and also for the ease in use that they provide. Moreover the cost and the time of installing are also saved.

The working and performance can be checked through a test board. The VNA cables are also a kind that is reliable and accurate kind of cables. VNA Cables needs to be reliable and accurate. There is no way they are not so. The reason is this that the VNA needs to give reliable and perfect results. The VNA Cables are designed for this main purpose. The Phase Stable Cable is also the kind that needs to be as accurate and good performance giver as can be. The phase stable cable, for the stability of the phase needs to be heat resistant and flexible too. These qualities are in good quality Phase Stable Cables.

Traditional Noise Parameter Measurements

A traditional noise parameter measurement setup, it includes a vector network analyzer (VNA) and a separate noise figure analyzer. For s-parameter measurements, the tuner is set to 50 ohms, and the two RF switches connect the device under test (DUT) to the VNA. For noise measurements, the switches connect the noise source to the DUT input and the noise receiver to the DUT output. An optional load tuner (not shown) is sometimes used when the DUT is highly reflective, to reduce sensitivity to error.

The tuner is pre-characterized at every frequency independently. This means that there is a unique set of tuner positions for each frequency, ensuring a good spread of source impedance points at every frequency. The tuner can be characterized separately, or as part of an in-situ system calibration. The advantage of doing it separately is that the same tuner file can be used for a long time, and then a hybrid in-situ calibration can quickly get the remaining s-parameter blocks.

The in-situ system calibration normally uses two VNA calibrations: a 2-port calibration at the DUT reference planes, and a 1-port s22 calibration at the noise source reference plane. By subtracting error terms, the 2-port x-parameters from the noise source to the DUT can then be determined. If the optional load tuner is used, then a 1-port s11 calibration at the noise receiver reference plane is also used to determine the 2-port s-parameters from the DUT to the noise receiver.

A hybrid in-situ calibration uses tuner data that is already characterized. The same VNA calibrations are still used to determine the 2-port s-parameters from the noise source to the DUT plane, which are then de-embedded to remove the tuner s-parameters. The result will be s-parameter blocks that include everything except the tuner.

After the system TRL calibration, the traditional noise receiver calibration and DUT noise parameter measurement are both done one frequency at a time[3][4]. This is because the noise parameter extraction involves complex math that is sensitive to small errors, and the pattern of source impedance points is important to get well-conditioned data[2]. Measuring one frequency at a time solves this by allowing the impedance pattern to be selected in an optimal manner for each frequency.

Pulsed IV testing to precisely measure the RF Devices

There are various methods characterizing the devices working on the signal networks using RF and other frequencies. Pulsed IV is one of the methods used for testing the devices working on electronic signals like as microwave and RF frequencies. This can be applied to test and specify the characteristics of the DUT after carrying out the calibration process carefully.

The testing procedure that uses the Pulsed (IV) current has become more prevalent these days for evaluating performance of the semiconductor devices. This process of testing uses pulse sources that is supplying a current pulse to the device under test and do the measurements with pulse measurement device. The technique of Pulsed IV measurement is used mainly on the large signal analysis.

This method is useful and effective over the other methods as it is cost effective and don’t give negative effects like as self heating and transient trapped charges. The factors like as self heating and trapped charges can be producing misleading results of the tests. The pulsed IV testing process delivers the accurate data on the devices needed to improvise the devices. This is best suitable to measure the test results in RF devices like as the transistors, switched and amplifiers relating to nonlinear responses.

There are two types of test methods used for testing in the pulsed environment; i.e. pulsed IV sweeps and transient (single pulse) testing method. If the DUT is associated with the double channels including pulse source and a pulse measurement system the results can be recoreded easily. This makes it very cost effective.

The results produced under different biased conditions for the Pulsed IV measurement sweeps carried out in pulsed system can be easily compared with the results produced in DC tests. The graphs of the curves produced by showing drain voltage VD and drain current ID behavior under different bias conditions are similar to that of the pulsed testing.

The basics of the pulsed IV testing are set to provide the pulses with non-zero value for both gate and drain voltage, often referred to as the operating point or quiescent (q) point. This technique is very useful for condition and based on the applicability of the low-duty-cycle pulse to the DUT. This helps in avoiding the self-heating and carrier-trapping effects that can deviate the exact results. The method of load pull testing is used to support the test results of overall measurements carried for a device.

The pulse width that is used in this technique ranges from milliseconds to nanoseconds. The selection of the pulse widths depends upon the DUT, materials and test parameters. The standard source-measure units (SMUs) are usually used to measure the results on millisecond pulse widths. The shorter pulses (microseconds to nanoseconds) are generally more effective for avoiding self heating and charge-trapping effects. Therefore, short-pulse pulsed I-V testing of RF transistors generally allows the creation of more useful models.