Radio integrated circuit receiver
The CMX994 is a direct conversion receiver IC. The receiver is fully integrated with a broadband Low Noise Amplifier (LNA) preceding the down-converter section and a high dynamic-range I/Q demodulator.
The receiver baseband section includes amplifiers and precise baseband filter stages. High-linearity down-converting mixers are immediately followed by a baseband filter stage.
The first stage of filtering is designed to remove off-channel blocking signals prior to baseband amplification. Following the filters, gain is applied via an on-chip variable gain amplifier.
LO generation is provided by an integer-N PLL and VCO negative-resistance amplifier suitable for VHF operation; an external LO may be used for other bands. LO dividers are provided for flexible multi-band operation.
The receiver I/Q chain includes the facility to correct for inherent dc offsets in the hardware. This process is intended to optimise the dynamic range of the system and must be controlled by the microprocessor or DSP that processes the I/Q signals from the IC.