Receiver bridges RF and digital
13 February 2008
Sampling high dynamic range signals in RF applications relies on ADC capabilities as well as amplifier output and matching impedances.
Coupling of the digital outputs into the sensitive analogue input is also a design challenge to bear in mind. The layout can also affect ADC performance, so a device that can take on the responsibility of impedance matching, filter design and layout can reduce design time.
Following on from the µModule announcement in Electronic Product Design, December 2007, Linear Technology has introduced the first in a series of SiP (system in a package) signal chain receiver modules.
The LTM9001 is a semi-customisable IF/baseband receiver subsystem that includes a 16bit ADC sampling up to 160Msample/sec, an anti-aliasing filter, and fixed gain differential ADC driver for communications and instrumentation.
The device can be used with pin-compatible product families and configured for different sampling rates. The differential ADC driver can be substituted for fixed gain versions ranging from 8dB up to 26dB. The anti-aliasing filters can also be configured as low-pass or bandpass filter versions, accepting input frequencies as high as 300MHz.
The LTM9001 is packaged in a 11.25mm x 11.25mm LGA package, using a multi-layer substrate that shields sensitive analogue lines from the digital traces. The LGA pads are positioned on the bottom of the package so that input and clock signals are separated from the digital outputs. Bypass capacitance is placed inside the module and close to the die, saving space, cost and providing a performance advantage over traditional packaging. As no external capacitance required, the receiver consumes approximately half the space of the discrete implementation.
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