U9391C/F/G/M Comb Generators

U9391C/F/G Comb Generators

The Keysight Technologies, Inc. U9391C/F/G comb generators were developed to provide precision phase calibration, for non-linear measurements using the PNA-X nonlinear vector network analyser (NVNA), referenced to the National Institute of Standards and Technology (NIST) standard. Additionally, the comb generators can be used to calibrate PNA and PNA-X network analyzers for phase and delay measurements of frequency converters without requiring reference or calibration mixers.

U9391C/F/G comb generators are based on Keysight InP MMIC technology 1 to ensure superior phase stability of the combs. Combining a frequency divider with a wide input signal frequency range allows for a broad range of possible harmonics spacing, making this suitable for characterizing non-linear devices. This module has a trigger output which enables synchronization with the pulse’s repetition frequency.

Keysight’s new patented comb generators offers the advantage of wide bandwidth output (10 MHz - 26.5 GHz, 10 MHz to 50 GHz, and 10 MHz to 67 GHz) and small minimum tone spacing (10 MHz). When driven by low phase noise sources, this comb generator will operate at frequencies lower than 10 MHz, but performance is not guaranteed. The input power and fundamental frequency have lower sensitivity than other comb generators. This means a comb generator calibrated at a single power level and frequency can be used across a wide range of input power levels and frequencies.

Accurate transfer of NIST standard

Keysight characterizes the U9391C/F/G comb generators’ phase standard using a precision calibration technique that is traceable to NIST. Each comb generator’s amplitude and phase data is stored in the module’s memory

Comb generator configuration

U9391C/F/G comb generator are controlled via a USB connection. The units need to be powered by separate power supplies (see page 5 for more detail). The network analyzer software automatically controls the U9391C/F/G units via USB after they have been designated as phase reference and/or calibration modules. The phase calibration procedure is carried out by following the on-screen instructions on the PNA or PNA-X.

Squaring circuit

The 10 MHz reference output on the back panel of the PNA/PNA-X can be used as the driving source for comb generator. U9391-60009 sine-to-square wave converter is recommended to be used in this setup, as comb generator is not able to work at its optimum condition with input sine-wave below 100 MHz.

The sine-to-square wave converter is provided with U9391C/F/G and shall be connected between the 10 MHz reference output and the input to comb generator.

Applications

NVNA

Two units of U9391C/F/G are required to carry out non-linear measurements. One unit is used as the phase reference module and the second unit as the phase calibration module.

The U9391C/F/G units need to be powered by separate power supplies. The NVNA software automatically controls the U9391C/F/G units via USB after they have been designated as phase reference and calibration modules respectively.

The phase calibration procedure is carried out by following the on-screen instructions on the PNA-X. After completing the calibration, the U9391C/F/G unit used for phase calibration can be disconnected. The other unit will be used as the phase reference and must remain connected while the measurement is carried out.

In most NVNA measurements, an external signal generator is used as driving source to drive comb generator that works as phase reference.

For measurements which require 10 MHz driving source, the 10 MHz reference output of PNA/PNA-X can be used. This setup will enable the NVNA measure­ment however with less accuracy in phase as compared with the conventional configuration using signal generator.

SMC+Phase

The scalar mixer/converter plus phase (SMC+Phase) measurement class, avail­able on PNA and PNA-X network analyzers, provides fully calibrated conversion gain/loss, relative phase, and absolute group delay measurements of mixers and frequency converters without the need for reference mixers. To calibrate the relative phase and absolute group delay of the test setup, either a calibration mixer or a U9391 Series comb generator can be used. The calibration is typically performed directly at the test ports of the network analyzer, without the adverse effects of test cables. This first-tier calibration is very stable when the instrument is in an environment with little temperature variation, and can be used for many months. Step two adds an S-parameter calibration at the desired reference planes, and is typically performed over the frequency range of interest for a particular DUT. This second-tier calibration removes the effects of all of the adapters and cables used to connect the instrument to the DUT, and extends the magnitude and phase calibration planes of the first-tier calibration to the reference planes of the second tier calibration. When using an U9391G comb generator for calibration up to 67 GHz, an additional high-pass filter is required. Two back-to-back Keysight V281A waveguide-to-coax adapters are recom­mended. In SMC+Phase application, 10 MHz reference output of the PNA/PNA-X is used as the driving source to comb generator in Phase Reference Calibration. As such, U9391-60009 sine-to-square wave converter needs to be used.

Wideband calibration

U9391C/F/G comb generators used with Keysight Signal Optimizer software (K3101A) enable wideband calibrations of signal analyzers and oscilloscopes. The Signal Optimizer software can establish a calibration plane at the DUT connection for transmit and receive with Keysight U9391/F/G comb generator calibration which flattens the amplitude and phase in wideband signals at RF, uW, mmWave frequencies for 5G. This makes it easier for 5G R&D engineers who are challenged to build reliable, accurate, and repeatable test systems especially for wideband calibrations. Following the calibration instructions, engineers can perform system calibration easier and simpler than ever.

The Signal Optimizer software provides a connection diagram from customers’ DUT, receiver and transmitter hardware, calibration controller PC with Signal Optimizer, and all the necessary accessories such as cables and connectors including the U9391C/F/G comb generator.

Drive power supply

The U9391C/F/G can be powered by DC power supply via the banana plug cable provided. Table 3-1 shows the drive power supply specification of U9391C/F/G U9391C/F/G Drive Power Supply Specification.