SSPA Drives Ka-band Links from 26 to 31 GHz

Amplification in the 26 to 31 GHz band is vital to a number of different terrestrial and satellite communication links, especially where the available bandwidth is needed for high data rates. For example, the spectrum is used in Ka-band satellite systems as the Tracking and Data Relay Satellite System (TDRSS). Closer to earth, the frequency band is home to terrestrial 28 GHz point-to-point and point-to-multipoint (PMP) systems, and in land- and sea-based terminals for common data link (CDL) and tactical common data link (TCDL) wireless and communications control links between manned and unmanned aircraft and land- and sea-based terminals.

To power transmitters for links in the 26 to 31 GHz frequency range, the engineers at MITEQ have developed the model AMF-5B-26003100-100-42P solid-state power amplifier (SSPA) as an alternative to the traveling-wave-tube amplifiers (TWTA) commonly used for transmitters at these frequencies. Based on GaAs pseudomorphic high electron mobility transistor (PHEMT) device technology, the AMF-5B-26003100-100-42P provides better than 15 W (+43 dBm) saturated output power from 26 to 31 GHz with high gain and low distortion, in a package that is a fraction of the size and weight of a TWTA.

The AMF-5B-26003100-100-42P SSPA is suitable for terrestrial and satellite communication links using complex modulation formats, either backed off from its saturated output level or operated under linear conditions. As measurements of saturated and linear output power show (see Figure 1), the amplifier is actually usable from 25.5 to 31.5 GHz. The plot of linear output power is the total output power based on a two-tone input and maintaining intermodulation distortion (IMD) of -25 dBc or better.

The compact SSPA provides generous gain of at least 40 dB, with peak-to-peak gain flatness that remains within a ±3 dB window, as shown in Figure 2. Over any 40 MHz segment of the total frequency range, the maximum gain slope is ±0.5 dB. The model AMF-5B-26003100-100-42P provides a 20 dB analog gain adjustment range for adapting to different input signal levels. With a gain control setting of 0 dB (0 dB attenuation), the SSPA's noise figure is 10 dB.

Figure 1 Measured data of saturated and linear output power for the AMF-5B-26003100-100-42P SSPA show usable output power across an additional 1 GHz of bandwidth.

Figure 2 Broadband gain of the AMF-5B-26003100-100-42P SSPA remains within a ± 3 dB window, with a gain slope of ± 0.5 dB for any 40 MHz band segment.

This solid-state power amplifier exhibits maximum input VSWR of 1.3:1 and maximum output VSWR of 1.5:1, indicating that it should deliver its rated output power level with minimal reflections in systems with characteristic impedance of 50 ohms. It minimizes IMD levels to better than -20 dBc for most of the operating frequency range even under saturated output power conditions, and to -25 dBc or better under linear operating conditions, making it suitable for single- and multiple-carrier applications. It also features tightly controlled group delay, with delay that is flat within ±40 ps across any 2 GHz band and within ±0.2 ns across the full 26 to 31 GHz band, as shown in Figure 3. Harmonics are a maximum of -40 dBc at both 1 and 3 dB output power levels, while spurious content is a maximum of -60 dBc when operating at 1 dB compression or under linear conditions.

Figure 3 Group delay of the model AMF-5B-26003100-100-42P SSPA is flat within ±40 ps across any 2 GHz band and within ±0.2 ns across the full 26 to 31 GHz band.

The model AMF-5B-26003100-100-42P typically consumes 150 W of power. It is designed to operate over a wide range of standard supply voltages, from +12 to +28 VDC, with options for supplies of +36 to +48 VDC. The SSPA can handle ambient temperatures from -40° to +60°C and baseplate temperatures from -40° to +85°C. It has a non-operating or storage temperature range of -50° to +70°C. It is built to operate at altitudes (atmospheric pressure) to 10,000 ft and 100 percent non-condensing relative humidity. This rugged power amplifier can withstand altitudes to 40,000 ft under non-operating conditions.

The amplifier is EMI and environmentally shielded, with integral voltage regulation and over temperature protection, as well as cooling, monitoring and control systems. For example, an alarm signal alerts an operator to over current or over temperature conditions. In addition, a high VSWR detector will determine when reflected power, such as caused by a bad load, exceeds a safe threshold level and shuts down the amplifier to prevent damage.

The SSPA is supplied in a rugged aluminum housing measuring 5" × 7" × 1.75" (127 × 177.8 × 44.45 mm) and typically weighing 2.5 lbs. (1.2 kg). The RF input and output ports use female K connectors, with an option for a WR-28 rectangular waveguide at the output port for Satcom systems equipped with waveguide flanges. The amplifier also includes a 20 dB coupled output sample port with a female K connector for power measurements.

MITEQ Inc., Hauppauge, NY
(631) 436-7400,
RS No. 303

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