Performance reviews of major RF microwave amplifiers

High-frequency amplifiers are available in a wide range of applications and can be used in almost all electronic devices, such as setting the noise figure of communication receivers and driving high-power signals for signal transmitter antennas. Types of high-frequency amplifiers include wideband and narrowband power amplifiers, low-noise amplifiers (LNAs), logarithmic amplifiers, operational amplifiers, transimpedance amplifiers (TIAs), and variable voltage amplifiers. They come in a variety of forms, including chips, devices in surface mount (SMT) packages, rack-mounted systems based on solid-state and vacuum tube devices, and more. This article describes some of the recently released RF/microwave amplifier products.

 

The smallest RF/microwave amplifiers are monolithic microwave integrated circuit (MMIC) devices. These devices are often used as gain blocks to compensate for the loss of passive signals in systems and circuits. There are many companies that offer MMIC amplifier chips and packaged MMIC amplifier modules, including Agilent, ADI, Filtronic, Hittite Microwave, Microwave Technology, Mimix Broadband, Mini-Circuits, and RFMD.

 

The HMC-ALH444 LNA chip from Hittite Microwave is ideal for commercial and military applications in the frequency range of 1~12GHz. The chip has a gain of 17dB at 10GHz and a low noise figure of only 1.75dB. The company also introduced GaAS high electron mobility transistor (HEMT) LNA chips at 65 GHz (Figure 1). The HMCALH382 chip provides 21dB gain in the 57~65GHz frequency range with a noise figure of 4dB. The chip delivers +12dBm of output power at 1dB of compression while drawing only 64mA from a single-ended +2.5V DC supply.

Microwave TechnologyMMA-021015It is another amplifier chip that uses AlGaAs/InGaAs pseudo-high electron mobility transistor (pHEMT) technology to achieve a noise figure of 4.8dB in the frequency range of 1~10GHz. The chip provides +17dBm output power and 18dB gain over the entire bandwidth, with +/-2.5dB gain flatness, and is designed to operate in a +6V DC system. The company also introduced a range of wideband medium power amplifiers, including the MMA-022020B amplifier with 22.5dBm output power at 1dB compression point and 8dB gain at 1~22GHz frequency.

 

In terms of bandwidth performance, few other MMIC chip amplifiers can match Agilent TechnologiesHMMC-5025Comparable. This distributed amplifier covers the 2~50GHz frequency range with 8.5dB small signal gain and +12dBm output power at 40GHz. The chip has a noise figure of only 5dB at 35GHz and 7dB at 50GHz. This seven-stage distributed amplifier chip has a gain control range of 30dB and each stage includes two cascaded GaAs FET devices.

 

Many MMIC amplifier suppliers also offer amplifiers with packages. For example, Mimix Broadband's CMM9000-QT two-stage feedback driver amplifier for the 1.5~6.0GHz frequency range is available in a 3×3mm surface-mount QFN package. The amplifier features 15dB of small-signal gain, +15dBm output power on 1dB compression, and integrates on-chip matching circuitry, RF choke inductor, and DC isolation capacitors. Analog Devices offers the ADL5320 predriver with 13.7dB gain and 4.2dB noise figure at 400~2,700 MHz operation and 25.6dBm output power at 2,140MHz, and the ADL5321 with 14dBm gain at 2,300~4,000MHz operating frequency, which provides +25dBm output power and 4dB noise figure at 2,600MHz.

Mini-Circuits offers several MMIC amplifier products with packages, including the ERA series. Among the many miniature ERA amplifiers with SMT packages, the ERA-1 amplifier provides more than 10dB of gain from DC to 8GHz and a typical output power of +12dBm at the 1dB compression point. The general-purpose amplifier has a low noise figure of 4.3dB and a typical third-order intercept point typical of +26dBm of high linearity.

 

Since these small MMIC amplifiers rarely provide more than 0.5W (+27dBm), larger circuits and packages are required to deliver high power. In a slightly larger size range, many companies offer amplifiers with coaxial connectors housed in aluminum housings. This amplifier provides higher power and dissipates more heat with the package and heat sink. For example, CTT offers narrowband and broadband power amplifiers for a wide range of commercial and military applications, covering 0.5~2.0GHz, 1.0~2.0GHz, 2~4GHz, 2~6GHz, 2~8GHz, 2~18GHz, and 2~20GHz frequency ranges, with up to +41dBm output power. Higher frequency models include the APW/265-3036 amplifier with 36dB gain in the 18.0~26.5GHz frequency range and +30dBm output power at 1dB compression point.

 

The advent of commercial wide-bandgap semiconductor devices, such as those made from silicon carbide (SiC) and gallium nitride (GaN), has provided amplifier design engineers with very power-dense devices. For example, British company Milmega uses Cree's SiC transistors in its UHF power amplifiers. At these frequencies, SiC MESFETs have greater power density than competing transistor technologies, enabling the design of amplifiers with higher power in smaller packages.

 

EMPOWER RF Systems' 1117-BBM3K5KEL type power amplifier uses GaN high power density devices. It has 20W typical output power at a 1dB compression point in the range of 500~2,500 MHz and provides 46dB gain and +/-1.5dB gain flatness.

 

Some power amplifiers rely on vacuum tubes rather than solid-state devices to produce high power outputs. For example, dB Control has introduced a new MPM series that includes a 6% duty cycle signal GHzdB-3757 amplifier that delivers 1,500kW peak power in the 6~18GHz range.

 

AR Worldwide's modular CMS1070 GaAs FET power amplifier can be used in WiMAX systems. IT PROVIDES +3,400DBM OUTPUT POWER AT A 1DB compression point in the range of 3,400~3,700MH, WITH A VARIABLE GAIN OF 20~50DB and a third-order interception point of +54dBm.

 

For satellite communications and other high-frequency applications, Endwave offers a range of solid-state amplifiers. The company recently released a pair of amplifier modules for satellite communications (Figure 3) with Ku-band units providing at least 40dB of gain, 0.5dB gain flatness, and +37dBm typical output power at 1dB compression point; Its Ka-band module provides at least 27dB of gain, 1dB gain flatness, and +36dBm output power at 1dB compression point. The noise figure of this module is very low, the noise figure of the Ku-band module is 4.5dB, and the noise figure of the Ka-band module is 6dB.