Active and passive components with adequate bandwidths can become integral parts of RF/microwave test setups.
This is an example of a broadband two-way power divider suitable for splitting signals in test setups. It spans 0.5 to 6.0 GHz and can handle as much as 250 W CW input power. (Photo courtesy of Narda Microwave East.)
Accurate microwave measurements require the right test equipment, but often more than that. Sometimes, additions are needed for optimum performance and/or functionality from the test setup. These additions often come in the form of power dividers/combiners, switches, filters, amplifiers, and other broadband components that can in some way help to make the measurements easier.
A list of such suppliers would be too long for this short article. Instead, a sampling of some of their components will be presented, along with how they might help to improve different RF/microwave measurement setups and measurements.
The definition for “broadband,” as in broadband components, has somewhat flexible meaning depending upon the application of interest. In most cases, broadband will mean a frequency range that exceeds the frequency span of the application to be tested. Many of the suppliers mentioned in this article offer numerous kinds of high-frequency components with wide frequency ranges. In most cases, custom versions of components are available—often with multiple functions, such as a frequency mixer combined with a local-oscillator (LO) amplifier to allow the use of a lower-power LO source. Those requiring a more detailed product search can utilize resources such as the Microwaves & RF Product Data Directory.
Power dividers are among the more useful broadband components in a test laboratory, owing to their capability to produce multiple test signals from one feed. They are available in many package forms—from coaxial units that can readily be introduced to a test system to smaller, surface-mount housings. For example, model P2D180900L is a two-way power divider from Synergy Microwave Corp. that spans 1800 to 9000 MHz with less than 1.2 dB insertion loss through 8 GHz. Supplied in a compact RoHS-compliant surface-mount package, this power divider can be used to construct a broadband test fixture for use with high-frequency analyzers.
For very broadband test applications, model ZFRSC-183+ is a two-way power splitter/combiner from Mini-Circuits that supports use from DC to 18 GHz. It is coaxial, with SMA connectors, and achieves low typical insertion loss of 0.7 dB above the 6-dB power division. The resistive power divider/combiner does not provide high isolation (typically between 6 and 7 dB through 17 GHz), although the company recommends the addition of a broadband amplifier to boost isolation as needed to a test setup.
Directional couplers, which allow tapping a small portion of a signal path for test purposes, are invaluable components to assist with RF/microwave tests. They are available with extremely broad bandwidths from a number of different suppliers and with several different connector choices to suit the requirements of a test setup.
Krytar, to give one example, offers coaxial directional couplers in various frequency bands to 18 GHz, including the 16-dB model 1850 directional coupler with frequency range spanning 500 MHz to 18.5 GHz. It exhibits less than 1.1-dB insertion loss across its broad bandwidth and it can handle as much as 20 W average input power and as much as 3 kW input power for very short peaks. Standard connectors are SMA female, although Type-N female connectors are available as an option. A coupler like the 1850 would make it possible to maintain signal flow in a system under study while extracting a small amount of the signal for analysis.
Anatech Electronics, which also makes directional couplers, may be better known for its RF/microwave filters, which allow the removal of unwanted interference and the isolation of desired signals in a test setup. The firm offers a number of different filter technologies featuring, for example, bandpass filters from 300 kHz to 20 GHz with 2 to 15 sections—as well as bandwidths from 1 to 100%—to serve a wide range of test-and-measurement filtering needs.
The firm also offers an array of connectors with its filters, including SMA, Type-N, and BNC connector types. Typical bandpass topologies include Butterworth, Chebyshev, and Elliptic types, using a range of technologies such as inductive-capacitive (LC) filters, surface-acoustic-wave (SAW) filters, cavity bandpass filters, crystal bandpass filters, and ceramic bandpass filters.
MITEQ provides many broadband components suitable for test-and-measurement applications, including directional couplers, mixers, multipliers, bias tees, phase shifters, terminations, and both solid-state and traveling-wave-tube (TWT) amplifiers for boosting test signal levels. As an example, model AMF-3F-26004000-33-8P is one of the firm’s coaxial low-noise amplifiers (LNAs) with over 18-dB gain from 26 to 40 GHz. It has a maximum full-band noise figure of 3.3 dB, with a typical value of about 3.0 dB. The minimum output power at 1-dB compression is +8 dBm with typical output third-order intercept point of +16 dBm. The amplifier draws less than 200 mA current from a single +15-VDC supply and is only 0.45 x 0.75 in. with field-replaceable 2.92-mm coaxial connectors.
Another broadband amplifier supplier, RF-Lambda, supplies power amplifiers and LNAs with manual and digital control interfaces. Many of these are suitable for test applications through 40 GHz, and they are supplied in coaxial and waveguide housings. An example of the LNAs is model RLNA20G40GA with 35-dB gain from 20 to 40 GHz. It is supplied with 2.92-mm (K) connectors and achieves a 4.5-dB noise figure and +10-dBm output power at 1-dB compression. The broadband amplifier measures 0.79 x 0.59 x 0.39 in. (20 x 15 x 10 mm).
M/A-COM Technology Solutions, one of the longest-running names in the industry, offers extensive lines of broadband active and passive components suitable for use in test-and-measurement applications. Product lines include digital attenuators, limiters, phase shifters, power detectors, and switches. Several different silicon- and GaAs-based semiconductor technologies account for switch products spanning DC to 70 GHz in a variety of different package styles, including coaxial packages suitable for use with test-and-measurement applications. The firm also offers a large number of switches for use at 75 Ω, intended for cable-television (CATV) applications.
Another well-established name in the industry, Narda Microwave East, offers many lines of high-performance switching and passive component products suitable for use in test applications. Its model 2382-2 is a two-way power divider for use from 500 MHz to 6.0 GHz (see figure). It handles as much as 250 W CW power, maintaining exceptional amplitude and phase balance, low insertion loss, and high isolation. It achieves insertion loss of 1.5 dB or less across the bandwidth, with better than 9-dB isolation from 500 MHz to 1 GHz and 17-dB isolation from 1 to 6 GHz. It measures 3.5 x 2.5 x 1.0 in. with Type-N connectors.
When the need for testing is at millimeter-wave frequencies, Spacek Labs offers a range of components starting at 18 GHz. These include amplifiers, detectors, filters, frequency multipliers and converters, frequency sources, and mixers. The mixers/converters make it possible to frequency translate signals from a millimeter-wave band to a lower intermediate-frequency (IF) signal within the operating range of a signal analyzer.
Spectrum Microwave’s lines of broadband mixers, formerly Magnum Microwave, are available in versions with connectors and in surface-mount and drop-in packages from use from 0.5 to 26.5 GHz. The company targets many mixers for specific communications bands, but also offers broadband mixers for test-and-measurement applications. As an example, connector-housed mixers in the MM9xxG-40 series operate across RF and LO frequency ranges of 0.5 to 18.0 GHz and yield an IF range of DC to 300 MHz, making them ideal for broadband frequency translation of test signals. They operate with +7 to +19 dBm LO power and 7-dB typical conversion loss, using SMA connectors.
Of course, many of the leading test-equipment manufacturers also supply broadband active and passive components in support of their instrumentation, and a visit to a favorite test-and-measurement website can usually reveal their available components; these include attenuators, mixers, switches, detectors, amplifiers, and power dividers/combiners. By way of example, Agilent Technologies offers a wide variety of RF/microwave test components, such as the model 87405C preamplifier with 25-dB gain and ±1.5-dB gain flatness from 100 MHz to 18 GHz. The broadband amplifier features 6-dB noise figure from 0.1 to 4.0 GHz and 4.5-dB noise figure from 4 to 18 GHz with +15-dBm output power at 1-dB compression.