GaAs-based broadband wireless and wireline communications component maker Anadigics Inc of Warren, NJ, USA has introduced a new style of RF power amplifier (PA) optimized to power 3G and 4G small-cell base-stations. Paired with digital or RF pre-distortion systems, the highly integrated designs create easy-to-use solutions that deliver very high efficiencies with the stringent linearity required for WCDMA, HSPA, and LTE networks, the firm claims. The new PAs are also packaged in compact (8mm by 14mm by 1.3mm) surface-mount modules that incorporate circuit components normally required separately.
The first Anadigics product to demonstrate this new power amplifier approach is the ASC7517. Operating in the 2100-2170MHz frequency band, the ACS7517 delivers 1.4W of power using only a 2.85V and 5V supply, while operating with a power efficiency of 28%. Used in a pre-distortion system, the PA supports the stringent adjacent channel level rejection (ACLR) requirements of WCDMA, HSPA, and LTE systems without compromising efficiency. The multi-stage PA also provides 42dB of RF gain, eliminating the need for driver amplifiers.
The ACS7517 uses a Doherty architecture, but does not require negative voltage supplies, separate control voltage for the integrated peaking amplifier, or critical supply sequencing. In addition, the PA does not require voltage adjustments to perform optimally over a wide operating temperature range of -40°C to +85°C. The package integrates both the RF matching and power combining circuit elements to save PCB space and provide a cost-effective solution that is much less complex than a traditional Doherty solution, it is claimed.
"Wireless data use continues to increase rapidly, placing tremendous demands on existing infrastructure networks," notes Glenn Eswein, director of product marketing for wireless infrastructure products at Anadigics. "Many operators are turning to small-cell base stations as a pragmatic solution for capacity-stressed 3G and 4G networks, but power consumption remains a significant concern, especially for multi-band and MIMO [multiple input, multiple output] applications," he adds. "Anadigics' new PA solution, demonstrated by the ASC7517, enables OEMs to develop simpler, smaller and more power-efficient designs using RF linearization techniques, without compromising data rate or linearity performance."
The ASC7517's performance is demonstrated for a Band 1 (2110-2170MHz) small-cell base station application using the SC1894 adaptive RF power amplifier linearizer (RFPAL) made by Scintera of Sunnyvale, CA, USA. The combined solution delivers 1.25W of linear power, with the PA operating at 27% efficiency. With either a single 20MHz-channel LTE signal or four simultaneous 5MHz-channel-bandwidth WCDMA signals, the solution provides ACLR performance better than -48dBc at rated power.
Engineering evaluation samples of the ASC7517 are available now for qualified programs. Anadigics is also developing other pre-distortion-optimized power amplifiers that will support different frequency bands and output power levels.
Anadigics is demonstrating the RF amplifier solution for Band 1 (using its ASC7517 power amplifier and Scintera's SC1894 RFPAL) in booth 718 at the 2013 IEEE MTT-S International Microwave Symposium (IMS) in Seattle, WA, USA (4–6 June).
