The pressure is on basestation designers to reduce size, cut power consumption, and speed up time-to-market. Each of these requirements is a major development problem to solve. But designers can achieve all three by using Linear Technology’s LTM9004 and RF-to-digital µModule receivers, which integrate the key components for 3G and 4G basestation receivers (WCDMA, TD-SCDMA, LTE, etc.) and smart antenna WiMAX basestations.

The integrated µModule receivers dramatically reduce board space, integrating the RF mixer/demodulator, amplifiers, passive filtering, and 14-bit, 125-Msample/s analog-to-digital converters (ADCs) in one conveniently small package. The LTM9004 implements a direct conversion architecture with an I/Q demodulator, low-pass filter, and a dual ADC. The LTM9005 implements an IF-sampling architecture with a down-converting mixer, a surface acoustic wave (SAW) filter, and a single ADC.

This high level of integration enables smaller boards or higher-channel-count systems, alleviating issues related to the separation and routing of signals while providing a significant reduction in design and debug time. These receivers harness years of signal chain design experience and offer it in an easy-to-use 22- by 15-mm µModule package.

Wireless carriers are under intense pressure to reduce equipment costs and the related operating expenses. Furthermore, the design trends include the need for smaller, lighter, lower-power basestations such as remote radio heads (RRH) that can be mounted on the tower with the antenna; high-density, high-channel-count macrocell basestations with higher efficiency; and the use of small, digital repeaters. The µModule receivers address these needs directly.

The LTM9004 and LTM9005 use only 25% of the board space area of discrete designs in addition to reducing the time and effort required for optimizing the design and layout of dozens of high-frequency components. This leads to lower development costs, fewer components to source and stock, and faster time-to-market.

Most receiver architectures use direct conversion, IF-sampling, or both. The LTM9004 implements direct conversion, which demodulates the RF signal directly in a pair of I/Q mixers and down-converts to dc (0 MHz in the frequency domain). This simplifies the filter, allowing the use of basic LC low-pass filters with a 10-MHz cutoff (20-MHz signal bandwidth). The input frequency range is 800 MHz to 2.7 GHz. Power consumption is 1.8 W. A 700-MHz version is in the works. Other filter options are available for different signal bandwidths.

The LTM9005 implements intermediate frequency (IF) sampling and down-converts to an IF of 140 MHz or 153.6 MHz. The digitized signal is then demodulated in the digital domain. The 20-MHz signal filtering is performed with a SAW filter integrated in the LTM9005. Input frequency ranges from 400 MHz to 3.8 GHz. Power consumption is 1.3 W. Other filter bandwidths are available.

The LTM9004 and LTM9005 are packaged in a space-saving 22- by 15-mm land-grid array (LGA) package, using a multilayer substrate that shields sensitive analog lines from the digital traces to minimize digital feedback. Supply and reference bypass capacitors are placed inside the package, tightly coupled to the die, providing a space, cost, and performance advantage over traditional packaging.

The LTM9004 and LTM9005 are sampling today with production volumes next quarter, priced at $75.00 each in 1000-piece quantities. Demo boards and samples are available.

Linear Technology Inc.