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Direct conversion I/Q demodulator

Direct conversion I/Q demodulator

Low power semiconductor specialist, CML Microcircuits has added a new Direct Conversion Receiver IC (DCRx) to its family of rf integrated circuits.

The CMX994 targets the next generation of multimode Software Defined Radios (SDR) for wireless data and two way radio applications. Its design is said to provide the optimum route for on board integration, allowing a small rf receiver to be realised with a minimum of external components in both zero IF and low IF systems.

Until recently, most radios have used the superheterodyne (Superhet) receiver, however enhancements in semiconductor technology have enabled the integration of DCRx. A DCRx mixes the wanted rf signal down to 0Hz in a single quadrature mixing process using a local oscillator (LO) tuned to the wanted rf channel frequency.

Selectivity filtering and gain can now take place at baseband with practical, low power, analogue and digital circuits. DCRx also eliminates the need for an image reject filter.

Key features of the CMX994 include on chip VCO for VHF applications, an operating range of 100MHz to 600MHz, precision baseband filtering with selectable bandwidths and the smallest pcb area, typically less than 50% of a dual superhet. Another feature is the single ended rf connections meaning no baluns are required.

According to CML, the small size and flexibility of Direct Conversion make it a key element for the next generation of multimode SDRs for wireless data and digital two way radio applications.

The CMX994 is available now, operates at 3 to 3.6V and comes in a Q4 40pin VQFN package.

Author
CML Microcircuits

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