Streamlining the Measurement Flow in Vector Network Analysis

February 17, 2015

  1. Introduction
  2. Viewing the Challenges from the User’s Perspective
  3. Designing for Enhanced Performance and Usability
  4. Implementing a Streamlined Measurement Flow
  5. Conclusion
  6. Related Information
Introduction

Two commonly held perceptions exist in the minds of RF engineers. Many feel that RF vector network analyzers (VNAs) are pretty much all the same: "An RF VNA is just an RF VNA." In addition, some view vector network analysis as a process that can be complex and time-consuming. Existing RF and microwave VNAs reinforce these perceptions because most are not user friendly, and different models from the same manufacturer typically lack consistent functionality and a common user interface (UI).

Independent of the UI, RF engineers working on leading-edge technologies are always seeking more capabilities and greater performance in new VNAs. For example, those who characterize the RF filter devices used in 4G and next-generation base transceiver stations (BTS) need much wider dynamic range—at least 10 dB more than currently available—to enable faster, more accurate measurements in the deep rejection bands of steep-skirted filters. In high-volume manufacturing of the RF devices used in smartphones and tablets, significant improvements in throughput are needed to meet aggressive ramp-up schedules.

Keysight is challenging these perceptions and addressing the technical expectations with a common platform for RF and microwave VNAs. The starting point is the new E5080A ENA vector network analyzer. The E5080A is the next-generation ENA, providing best-in-class performance, flexible functionality and advanced usability. With its intuitive, touch-based interface, the new ENA is designed to help users streamline their measurement flow and achieve better results in less time. On the production line, improved analog performance ensures faster throughput. In the R&D lab, better performance enables greater design margins, and enhanced usability helps ensure greater confidence in results and faster time-to-market.

The E5080A can be configured with two or four ports and a frequency range of 9 kHz to 4.5, 6.5 or 9.0 GHz. Banner specifications include extremely wide dynamic range of 147 dB (typical) and speeds as fast as 3 ms for a 201-point measurement with full two-port calibration. Most notable is the 12.1-inch touchscreen display, which is central to a graphical user interface (GUI) that accesses instrument software based on "best of" capabilities from the proven ENA and PNA families of Keysight VNAs (Figure 1).

Figure 1: With its combination of enhanced performance and advanced usability, the E5080A helps users achieve better results in less time.

Figure 1:With its combination of enhanced performance and advanced usability, the E5080A helps users achieve better results in less time.

Viewing the Challenges from the User’s Perspective

From an engineer's point of view, two key factors affect their experience with a VNA: analog performance and overall usability. Both factors come into play when they're making any type of measurement, simple or complex.

Analog performance ensures measurement accuracy, and this ultimately affects confidence in results. For example, wide dynamic range makes it possible to cover a larger variety of applications and component types. The ability to tune dynamic range lets the user balance measurement speed, accuracy and efficiency to suit specific test requirements.

Usability is important for basic measurements such as S-parameters, and it becomes especially important with complex tasks such as the characterization of mixers. In some current-generation VNAs, the GUI lacks a smooth, intuitive flow through the steps needed to correctly set up stimulus, response, calibration, channels and display traces.

On the surface, this is an issue because it can result in lost time. In R&D, an accumulation of time-consuming measurements can eventually ripple through as a schedule delay that causes a project to miss its target launch date.

More fundamentally, poor usability can lead to poor measurement results. This has two consequences. For one, problems with performance in the device-under-test (DUT) may either go undetected or result in misidentification of problems that don't actually exist. In addition, uncertain results can undermine an engineer's confidence in the accuracy and repeatability of their measurements: "Did I set it up correctly? Am I seeing the right thing? Am I getting useful results?" This can turn into lost time spent checking setups and rerunning measurements.

Designing for Enhanced Performance and Usability

To help ensure excellent results in less time, many customers have asked us to build measurement guidance into our instruments—and to present those guides on the screen of the VNA. This is a logical and feasible idea, given the processing power, memory and displays that can be built into new-generation VNAs. It's also an important and crucial idea, given the time pressures and design requirements most engineers face.

To address these needs, the Keysight design team pursued advances related to instrument performance and front-panel usability. On the performance front, one key goal was to retain or extend the performance of the ENA family while improving measurement speed. Using the popular E5071C as a benchmark, the E5080A provides an improvement in dynamic range of more than 10 dB, reaching 147 dB (typical, Figure 2).

Figure 2: The E5080A (red trace) provides greater dynamic range than the E5071C (gray trace).

Figure 2:The E5080A (red trace) provides greater dynamic range than the E5071C (gray trace).

The increase in dynamic range also provides a speed advantage because measurements can be made with a wider IF bandwidth (IFBW), enabling faster sweep rates. Two real-world test scenarios highlight the improvement in measurement speed. The first is characterization of a BTS filter: with its wide dynamic range, the E5080A is 10 times faster than the E5071C. The main reason is the ability to achieve the required dynamic range (>110 dB) while using a wider IFBW (10 kHz vs. 1 kHz).

In this case, the 10x wider IFBW translates into a 10x speed advantage — 0.17 s versus 1.6 s —because the analog measurement time dominates for IFBW settings ≤1 kHz. Measurements were made with 801 points, a full two-port calibration and the maximum source power level of reach model (+15 dBm for E5080A, +10 dBm for E5071C).

The second example is the testing of a handset duplexer. Measurements were made using a segment-sweep table with a total of 1,601 points, a full three-port calibration and +5 dBm source output power. To achieve the required 80 dB dynamic range, the respective IFBW settings were 300 kHz for the E5080A and 70 kHz for the E5071C. The resulting speed improvement is about 1.8x (60 ms versus 100 ms) due to the E5080A's improved measurement speed and enhanced dynamic range that enables use of a wider IFBW.

To provide a foundation for next-generation Keysight VNAs, the team set out to create a common platform that leverages the best attributes of the ENA and PNA families. For example, the ENA now includes a variety of useful firmware capabilities previously found in the PNA. These include the Smart Cal Wizard and the power meter as receiver (PMAR) function. The new ENA series also shares a common set of SCPI commands and, in the future, will support a variety of PNA software applications.

Two of the guiding principles were to remain familiar and comfortable for existing ENA/PNA users and also be intuitive and comfortable for new users. The net result is a GUI that will be helpful to engineers who, from time to time, need to make simple or complex measurements while characterizing or troubleshooting a variety of RF components or subsystems. It is also useful to experienced users who occasionally need to make highly complex measurements and will benefit from reminders about the crucial steps and settings.

Implementing a Streamlined Measurement Flow

A quick look at the E5080A reveals a few key attributes of the new platform and GUI. Most obvious is the 12.1-inch color display that occupies more than half of the front panel. To the right of the display, the interface places hardkeys in four logical clusters: Instrument, Response, Stimulus and Utility (Figure 3).

Figure 3: Placing the Instrument, Response and Stimulus hardkey groups next to the tabbed softkeys is the starting point for efficient measurement setups.

Figure 3:Placing the Instrument, Response and Stimulus hardkey groups next to the tabbed softkeys is the starting point for efficient measurement setups.

Measurement flow proceeds from right to left: front panel keys, touch-activated softkeys with tabs, and touch-driven trace displays and windows. By providing access to desired functions within very few steps, this approach helps the user quickly create complete measurement setups comfortably and confidently.

On the screen, the new toolbar and an array of context-sensitive popup menus provide direct access to essential features, enabling rapid changes to measurement setups (Figure 4). A long touch on the screen activates popup menus, and these present the most relevant choices without needing to access the softkeys. The user can also change the layout of measurement traces and windows with fingertip drag-and-drop operations.

Figure 4: The toolbar (upper left) and context popup menus (lower left) streamline measurement flow by putting frequently used functions at the user’s fingertip.

Figure 4:The toolbar (upper left) and context popup menus (lower left) streamline measurement flow by putting frequently used functions at the user’s fingertip.

In many cases, the best way to quickly start a measurement is the Setup key in the Instrument group. Pressing Setup activates a softkey menu that has two choices: Sweep Setup and Quick Start.

Choosing Sweep Setup opens a window containing a single dialog menu that presents the five fundamental measurement parameters: start frequency, stop frequency, power, points and IFBW. This is a useful guide for users of any experience level.

Quick Start goes a step farther by providing access to dialog menus that let the user open a variety of templates for common measurements (Figure 5). The window contains three tabs: S-parameters, Balanced and Other. Each presents a variety of common measurements and offers choices that guide the user through the setup process. Examples include configurations that calculate and display all nine S-parameters for a three-port device, perform single-ended-to-balanced measurements (with multiple display choices) and implement time-domain measurements.

Figure 5: Three tabs in the Quick Start dialog menu present templates for common measurements.

Figure 5:Three tabs in the Quick Start dialog menu present templates for common measurements.

A tab in the Quick Start menu lets the user create customized measurements. The essential hardkeys are Trace, Channel and Display on the front panel, and the underlying softkeys let the user add or delete traces, channels and windows. This makes it easy to create a complete set of measurements and, through the Utility group, save them as favorites that can be accessed through the toolbar.

Conclusion

The new-generation E5080A ENA unites three key attributes: best-in-class performance; a modern, touch-based GUI; and a converged platform based on the proven PNA and ENA analyzers. For end-user engineers, these capabilities streamline simple and complex measurements and enable better results in less time.

Every Keysight vector network analyzer is the ultimate expression of the company’s expertise in linear and nonlinear device characterization. On the production line, the ENA Series provides the throughput, repeatability and reliability needed to create accurate, dependable test stations—and transform parts into competitive components. In R&D, the touch-based ENA streamlines the measurement flow and enables better results in less time. With the ENA Series, engineers and their organizations are equipped to drive down the cost of test.

About Keysight Technologies

Keysight Technologies (NYSE:KEYS) is a global electronic measurement technology and market leader helping to transform its customers' measurement experience through innovations in wireless, modular, and software solutions. Keysight's electronic measurement instruments, systems, software and services are used in the design, development, manufacture, installation, deployment and operation of electronic equipment. The business had revenues of $2.9 billion in fiscal year 2014. Information about Keysight is available at www.keysight.com.

Related Information
Contacts:

Janet Smith, Americas
+1 970 679 5397
janet_smith@keysight.com
Twitter: @KeysightJSmith

Sarah Calnan, Europe
+44 (118) 927 5101
sarah_calnan@keysight.com

Connie Wong, Asia
+852 3197-7818
connie-ky_wong@keysight.com