Tiny SDLVAs Tackle 20-GHz Bandwidth

Military system designers are often faced with processing input signals over a wide dynamic range. Many systems, such as direct-finding (DF) receivers, electronicintelligence (ELINT) receivers, electroniccountermeasures (ECM) systems, radar warning receivers (RWRs), and even in commercial and military instrumentation, it is often necessary to capture and analyze narrow pulses with large variations in amplitude. Traditionally, the successive detection log video amplifier (SDLVA) is the component of choice for this task. And today, when system designers need a high-performance SDLVA, they have two more choices with outstanding performance over the wide frequency range of 0.1 to 20.0 GHz: the models HMC613LC4B and HMC-C052 SDLVAs from Hittite Microwave Corp. (Chelmsford, MA). The former is supplied in a compact 4 x 4 mm ceramic package while the latter is housed in a miniature hermetic module. Both offer the signal-processing capability needed to capture and analyze narrow, highspeed RF pulses over wide dynamic ranges. The small size and low power requirements of these SDLVA solutions allows designers to incorporate this function into systems once limited to alternative signal-processing approaches, such as portable systems.

Broadband SDLVAs have never been considered "catalog" components. The wide-dynamic- range, pulse-processing capability has typically been realized with expensive hybrid assemblies based on discrete devices and extensive hand-tuning to meet a set of custom specifications. Until now, system designers implementing the SDLVA function were often forced to rely on solutions that required both a positive and negative DC voltage, occupied large form factors, and consumed and dissipated several watts of DC power. Typical SDLVAs have been expensive, often as high as $7,000 each in small quantities. With the introduction of the models HMC613LC4B (Fig. 1) and HMC-C052 (Fig. 2) SDLVAs from Hittite Microwave Corp., much has changed.

For designers looking to capture short pulsed signals with high amplitude accuracy, the HMC613LC4B SDLVA represents a compact, cost-effective solution. It is designed to convert pulsed RF signals at its input to a proportional DC voltage at its output. It handles input signals over wide frequency and amplitude ranges, while also preserving the amplitude information of the input signals.

In terms of performance, the HMC613LC4B SDLVA operates over the 0.1-to-20.0-GHz frequency range, provides a logging range to 62 dB, and delivers tangential signal sensitivity (TSS) of -64 dBm. It consumes only 83 mA current from a single +3.3-VDC DC supply when processing RF signals at -30 dBm input power. Ideal for EW and ELINT applications, the HMC613LC4B is capable of processing RF pulses in the 0.1-to-20.0-GHz frequency band with amplitudes from -57 to +5 dBm with only 4 ns rise times and 26 ns of recovery time.

The HMC613LC4B employs a successive compression topology that delivers extremely high dynamic range and conversion accuracy over its wide input frequency range (Fig. 3). As the input power is increased, successive RF amplifier stages move into saturation one by one creating an accurate approximation of the logarithmic function. The output of a series of detectors is summed into a single video amplifier for the purpose of providing a single detected output. When the HMC613LC4B is used in detection mode, the VIDEO OUT pin is connected to the Video FB pin via a 0-ohm resistor, providing a nominal logarithmic slope of 14 mV/dB and a typical intercept of -119 dBm at 10 GHz. The output gain stage of the HMC613LC4B may be modified by connecting appropriate external resistors between the VIDEO OUT and the VIDEO FB pin, and also between the VIDEO FB pin and ground. The HMC613LC4B also provides an EN (enable) pin, which is connected to Vcc (+3.3 VDC) during normal operation. If the enable pin is connected to ground, the SDLVA is disabled, and the total supply current is reduced to less than 3 mA. This is a useful feature for controlling total system power, particularly in high-speed channelized receiver designs, where multiple channels/SDLVAs are deployed.

Figures 4 and 5 show the typical logarithmic error and video output voltage performance of the HMC613LC4B over the -40 to +85C operating temperature range at 2 and 20 GHz. The typical flatness over the 2-to-20-GHz band from -55 to +5 dBm is shown in Fig. 6. Measurements on the HMC613LC4B typically reveal better than 2 dB flatness to 20 GHz at a -30-dBm input-power level. The maximum temperature-related deviation is 1 dB at any given frequency and power level over the full operating temperature range.

The HMC-C052 integrates the HMC613 bare die, a linear regulator, and off-chip components within a hermetically sealed package that can be used as a connectorized module (2.92 mm or SMP) or as a drop-in design. The HMC-C052 operates from 1 to 20 GHz with a TSS of -67 dBm, and draws only 86 mA current from a single +7 to +16 VDC supply. (The table compares the key specifications of the HMC613LC4B and the HMC-C052 SDLVAs.) The HMC-C052 operates from -55 to +85C and is housed in a miniature 22.6 x 21.6 x 5.84 mm package.

The miniature HCM-C052 module represents a space savings of more than 85 percent compared with existing typical broadband connectorized SDLVA devices with similar performance (Fig. 7). The connectorized HMC-C052 module can immediately replace existing broadband SDLVA modules, resulting in a lower-cost, reduced-power-dissipation (heat) solution occupying a significantly smaller form factor.

Hittite Microwave's design philosophy involves the careful selection of the best semiconductor processes and design techniques available for each component solution ensuring the delivery of market-leading product performance. This performance improvement allows the systems designer to maximize the true potential of the design to ultimately deliver a superior product. The block diagram for a RWR (Fig. 8) shows how a system design can be optimized by careful section of Hittite Microwave catalog components. In this application example, the RWR combines signal filtering, amplification, detection, and frequency measurement into one multifunction unit. In such a design, a system engineer is often seeking to reduce power consumption along with the overall size and weight of the RWR module. Any reduction in power consumption renders a double benefit, particularly in airborne or unmannedaerial- vehicle (UAV) applications, as a smaller, lighter power supply is required.

The HMC613LC4B or the HMC-C052 SDLVAs are key components required to implement the RWR function, and compared with traditional SDLVA solutions, provide significant savings in both power consumption and size for equivalent performance. The HMC613LC4B or the HMC-C052 SDLVA can be combined with a number of additional high-performance catalog components from Hittite Microwave to implement an RWR capable of measuring signals from 2 to 20 GHz. The simplified block diagram of Fig. 8 shows two amplitude measurement channels that allow direction finding by comparing the signal amplitude of the adjacent antennas. One of the amplitude channels is selected via the HMC547LP3E single-pole, doublethrow (SPDT) switch and feeds the RWR's instantaneous-frequency-measurement (IFM) circuit, thus performing a frequency measurement on an antenna pair. The HMC613LC4B SDLVAs provide the logarithmic video voltage signals that are usually digitized with a series of comparator circuits, prior to further processing. To meet military/ high-reliability or ruggedized system requirements, the RWR function may be implemented with hermetically sealed, connectorized modules (labeled in red) that are available as stock items.

The models HMC613LC4B and HMC-C052 SDLVAs combine wide input bandwidths, wide dynamic range, and fast rise/fall times with extremely compact packaging for system-level designers seeking alternatives to traditional microwave-integrated-circuits (MIC) hybrid and discrete-based SDLVAs. The HMC613LC4B and HMC-C052 facilitate accurate logarithmic power measurement of RF signals in the 0.1-to-20-GHz and 1-to-20-GHz ranges, respectively, in commercial, military, and space applications. These SDLVAs are also ideal for a myriad of applications including RWRs, DF receivers, IFM receivers, EW and ECM systems, phased-array antennas, radar altimeters, digital frequency discriminators, and RF test equipment.

In addition to these new SDLVA products, Hittite Microwave continues to expand its product portfolio and designers can now choose from more than 670 standard products spanning the frequency range from DC to 110 GHz, in 18 different product lines. Hittite Microwave Corp., 20 Alpha Rd., Chelmsford, MA 01824; (978) 250-3343; FAX: (978) 250-3373; E-mail: sales@hittite.com: Internet: www.hittite.com.