With the inception of wireless networks, the microwaves and RF industry experienced an uptick in investments and innovation. Although the commercial sector has had its ups and downs, this market has generally helped to make the RF segment busier and more prosperous. At the same time, the RF industry has remained true to its heritage by continuing to satisfy military needs. The increase in military activity in recent years also has nurtured technology development. Such heightened development in both the commercial and military sectors has resulted in a plethora of impressive new products in the RF and microwave industry. To honor these exceptional developments, the staff of Microwaves & RF has selected a list of the Top Products of 2006 (see table).

At the start of the year, for example, Micro Lambda Wireless' (www.microlambdawireless.com) silicon-germanium (SiGe)–based yttrium-iron-garnet (YIG) oscillators were announced. YIG oscillators tend to be used in designs that demand low phase noise, wide modulation bandwidths, and moderate tuning speed. By merging its YIG technology with low-noise, SiGe, heterojunction-bipolar-transistor (HBT) active devices, however, Micro Lambda also succeeded in lowering phase noise. The firm's efforts resulted in several new lines of YIG-tuned oscillators with coverage from 6 to 20 GHz. Their typical phase noise is as good as –130 dBc/Hz offset 100 kHz from 8-to-18-GHz carriers. The product lines comprise the MLXB-Extreme 1.25-in. cube oscillators, the MLXS-Extreme 1.75-in. spherical oscillators, and the MLXM-Extreme 1-in. cube oscillators. The MLXS-Extreme line, for example, offers three models with frequency ranges of 6 to 18 GHz, 8 to 18 GHz, and 8 to 20 GHz. Those models offer a guaranteed phase noise of –100 dBc/Hz offset 10 kHz from the carrier and –123 dBc/Hz offset 100 kHz from the carrier (Fig. 1).

Interestingly, two different types of oscillators share the 2006 Top Product title. The other oscillator product on the list is designed to replace YIGs. Just a month after Micro Lambda's YIG transistors graced the cover of Microwaves & RF, the April Cover Story detailed Synergy Microwave's (www.synergymwave.com) distributed-coupled-YIG-replacement (DCYR) oscillator series. Although YIG oscillators boast broadband, low-noise, high-frequency capabilities, they also are power hungry and large in size. In addition, having a YIG sphere mounted in an electromagnet's air gap is not conducive to integrated-circuit (IC) integration. YIG oscillators also have issues with thermal drift, vibration, electromagnetic interference (EMI), and more. The DCYR sources promise phase-noise performance that is comparable to the best YIG sources over wideband tuning ranges. Yet they do so at a fraction of the size and power consumption. They also vow to deliver faster tuning speed than YIG oscillators. The voltage-controlled oscillators, which span frequencies from 250 to 6000 MHz, provide typical measured phase noise of –132 dBc/Hz offset 100 kHz from carriers 250 to 1000 MHz. The oscillator's topology is based on multi-coupled, slow-wave (MCSW) planar resonators. This approach supports multi-octave tuning in a small package. Plus, it is compatible with IC fabrication processes. By dynamically optimizing the impedance transfer function and coupling factor across the planar, multi-coupled network's guided distributed medium, the topology allows for a substantial reduction in phase noise.

Like oscillators, amplifiers are the workhorses behind many RF and microwave applications. As such, new amplifiers are constantly being developed. Two such products made it into this year's list of top products. The first one, which hails from MITEQ, Inc. (www.miteq.com), is a surface-mount amplifier. Usually, adding an amplifier to an application demands a trade-off between size and difficulty of integration. A connectorized amplifier is easy to use, but it comes in a large package size. Yet smaller chip-and-wire amplifiers involve more labor when adding to a circuit or system. To provide the best of both of these amplifiers, the TSM series of true surface-mountable amplifiers covers frequency bands from 0.1 to 40.0 GHz. The amplifiers, which measure just 0.52 X 0.44 X 0.14 in., are actually usable to 45 GHz (Fig. 2). If proper surface-mounting practices are followed, the gain flatness of these broadband amplifiers vows to beat the performance of much larger, cascaded connectorized amplifiers. Five standard models comprise the TSM series surface-mount-technology (SMT) amplifiers. The model TSM1800, for example, operates from 100 MHz to 18 GHz with 22 dB gain and ±2.5 dB gain flatness. At the same time, it maintains a low noise figure of 3 dB. The amplifier delivers +10 dBm output power at the 1-dB compression point. It exhibits input/output VSWRs of 2.50:1 and draws 175 mA current from a +15-VDC supply.

The second amplifier, which was the focus of the May Cover Story, is an altogether different animal. By providing sufficient linearity and bandwidth, Hittite Microwave Corp.'s (www.hittite.com) HMC660LC4B track-and-hold (T/H) amplifier supports high-speed analog-to-digital converters (ADCs) in wideband data-acquisition applications. As the first member of a family of wideband T/H amplifiers, it allows designers to directly sample full-scale, 1-Vpp signals with as much as 4.5-GHz input bandwidth. Based on SiGe BiCMOS technology, the device has been characterized for 9-b T/H-mode linearity for input signals from DC to 4 GHz and a clock rate of 2 GHz. The amplifier can be used with high-speed ADCs to simplify the down-conversion signal path in digital receivers. Because it is wideband and operates at high frequencies, the T/H amplifier allows designers to operate at higher intermediate frequencies (IFs). It eliminates mixers, bandpass filters, amplifiers, and local oscillators (LOs). The HMC660LC4B's secret is its design topology, which allows a significant improvement in the trade-off among bandwidth, linearity, and hold-mode feed-through. That topology also overcomes the problem of sensitivity to input signal level, which is common in other commercial T/H circuits.

For amplifiers, higher-power transistors translate into less output stages for a given output-power level, less combining stages (and lost power from power-combining losses), smaller size, and decreased complexity (resulting in higher inherent reliability). In addition, judicious thermal design must be used--especially when a single device is capable of as much output power as the X-band (8-to-12-GHz) gallium-nitride (GaN) field-effect transistor (FET) from Toshiba America Electronic Components (www.toshiba.com/taec). This FET is covered in this issue's Product Technology section. It attains 81.3 W output power at 9.5 GHz, which is the highest output power yet reported for such a device at this frequency. Earlier this year, Toshiba offered samples and small quantities of 50-W GaN devices for WiMAX and cellular applications. The company has now optimized that transistor's epitaxial layer and device structure for performance at X-band frequencies. It claims that this device has about six times the power density of an equivalent-frequency gallium-arsenide (GaAs) FET. The transistor features a high-electron-mobility-transistor (HEMT) structure for high power at high frequencies. To achieve better performance, TAEC optimized the composition and thickness of the aluminum-gallium-nitride (AlGaN) and GaN layers.

Another transistor also takes the Top Product title for this year. Yet this one is an LDMOS transistor that is well suited for the high-frequency/very-high-frequency (HF/VHF) broadcast and ultra-high-frequency (UHF) radar markets. Hailing from Philips Semiconductors (www.philips.com), this device delivers 500 W CW output power from HF through 500 MHz. To satisfy its intended applications, it also is extremely compact. This unmatched transistor was optimized for UHF prior to testing. At 440 MHz, device gain was typically 12 dB from 100 to 500 MHz with 500 W output power across that range. The test conditions included dual drain voltage supplies of +32 VDC and quiescent current draw of 500 mA for each supply. At 500 MHz, compression is slightly uneven, thereby indicating raw power capability. Current draw and efficiency were measured under the same bias conditions and power ramp. At 440 MHz, the current draw is roughly 2.7 A for 100 W of output power. It rises to less than 5 W for 500 W output power. The drain efficiency is better than 40 percent at 500 W output power.

A small footprint also is emphasized in the SIM line of low-temperature-co-fired-ceramic (LTCC) mixers from Mini Circuits (www.minicircuits.com). LTCC components can be produced in a fraction of the size of conventional lumped-element or microstrip components. By merging LTCC with advanced semiconductor technologies, these broadband mixers cover bandwidths from 750 MHz to 15 GHz. This wide frequency range makes them suitable for a host of applications. For example, the model SIM-153+ LTCC double-balanced mixer can be used as both an upconverter and downconverter. As a result, it targets a wide range of commercial and military applications. At just 0.2X 0.18 X 0.08 in. (5.1 X 4.6 X 2.1 mm), the model SIM-153+ mixer is considerably smaller than commercial FET- and diode-based mixers (Fig. 3). Unlike some semiconductor mixers, it also is passive. In addition, this mixer requires no bias energy and is insensitive to electrostatic discharge (ESD). It operates with RF signals from 3.4 to 15.0 GHz and has an intermediate-frequency (IF) range of DC to 4.5 GHz.

The February Cover Story focused on a very different, but equally impressive product: an RF integrated circuit (RF IC). Due to the large number of wireless standards—and their seemingly constant evolution—design cycles seem nearly endless. With each new cellular or wireless-local-area-network (WLAN) standard, another chip set must be developed. A much-heralded answer to this design quagmire lies in a software approach. The Softransceiver RF IC from BitWave Semiconductor (www.bitwavesemiconductor.com), for instance, can adjust performance parameters like channel bandwidths and linearity under software control. With this RF IC architecture and the company's proprietary control software, this chip promises to serve nearly all wireless air-interface standards. It covers a total bandwidth of 700 to 4200 MHz. The transceiver IC fully supports third-generation (3G) cellular standards from the Universal Mobile Telecommunications System (UMTS) as well as IS-95B, 1xRTT, EV-DO, and the IEEE 802.11b/g WLANs. It partially supports older cellular standards, short-range wireless standards like Bluetooth, WiMAX and WiBro, position services like Global Positioning System (GPS), and more. Because the IC is fabricated with standard 0.13-µm digital CMOS, the RF/IF, mixed-signal, and digital components are housed on one chip.