Linear Technology releases RF-to-digital receivers

The LTM9004 and LTM9005 receivers offer a reduction in board space, integrating the RF mixer/demodulator, amplifiers, passive filtering and 14-bit, 125Msps analogue-to-digital converters (ADCs) in one small package.

The LTM9004 implements a direct conversion architecture with an I/Q demodulator, a low-pass filter and a dual ADC.

The LTM9005 implements an IF-sampling architecture with a down-converting mixer, a surface acoustical 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 reduction in design and debug time.

The receivers harness years of signal chain design experience and offer it in an easy-to-use 22 x 15mm Umodule package, according to the company.

Cellular service providers are under pressure to reduce capital and operating expenses.

Supporting trends include the need for smaller, lighter, lower-power basestations such as remote radio heads (RRHs) that can be mounted on the tower with the antenna; high-density, high-channel-count macro-cell basestations with higher efficiency; and the use of small, digital repeaters.

These Umodule receivers are designed to address these trends directly.

At only 25 per cent of the board space area of discrete designs, the LTM9004 and the LTM9005 save space and reduce the time and effort required for optimising the design and layout of dozens of high-frequency components.

This leads to lower development costs, fewer components to source and stock and faster times to market.

Two receiver architectures dominate basestation designs: direct conversion and IF sampling.

Direct conversion demodulates the RF signal and down-converts to DC (0MHz in the frequency domain).

This simplifies the filter, permitting low-pass filters with a 10MHz cut-off (20MHz signal bandwidth).

The LTM9004 implements this architecture.

Other filter options are available for different signal bandwidths.

IF sampling down-converts to an intermediate frequency - 140MHz in this case - and the signal is demodulated in the digital domain.

The 20MHz signal filtering is done with a surface acoustical wave filter integrated in the LTM9005.

Other filter bandwidths are available.

Both the LTM9004 and the LTM9005 are packaged in a space-saving 22 x 15mm LGA package, utilising a multilayer substrate that shields sensitive analogue lines from the digital traces to minimise digital feedback.

Supply and reference bypass capacitance is placed inside the Umodule package, tightly coupled to the die, providing a space, cost and performance advantage over traditional packaging.

The LTM9004 and the LTM9005 are available in production volumes, priced at USD75 each in 1,000-piece quantities.