Quadrature demodulator for next-generation K-band satellite communications

Analog Devices Inc. ADMV4540 K-Band Quadrature Demodulator is a highly integrated quadrature demodulator with an integrated synthesiser ideal for next-generation K-band satellite communication. The RF front end of the device comprises two LNA paths, each with an optimal cascaded, 5dB, double-sideband noise figure at maximum gain while minimising external components. The dual paths permit support for antenna polarisation. Selection of the LNA path can be made via the SPI.

The LNA output of the device is downconverted to baseband utilising an I/Q mixer. The I/Q mixer output is then fed into fully differential low noise and low distortion programmable filters and VGAs. Each channel can reject large, out-of-band interferers while reliably increasing the wanted signal, reducing the bandwidth and resolution needs on the ADCs of the system. The excellent matching between channels and the high SFDR, overall gain, and bandwidth settings make it ideal for satellite communication systems with dense constellations, multiple carriers, and nearby interferers.

The three filter corners of 125MHz, 250MHz, and 500MHz are programmable via an SPI. The filters deliver a sixth-order Butterworth response with -3dB corner frequencies of 141MHz, 282MHz, and 565MHz. For operation beyond 565MHz, the filter can be disabled and bypassed, thereby expanding the -3dB bandwidth up to 900MHz.

The device includes an integrated fractional-N PLL and a low phase noise VCO. These integrated functions generate the necessary on-chip LO signal for the two double balanced I/Q mixers, removing the demand for external frequency synthesis. The VCO utilises an internal automatic calibration routine that allows the PLL to select the necessary settings and lock.

The Analog Devices Inc. ADMV4540 K-Band Quadrature Demodulator is available in a 48-terminal, RoHS compliant, 7mm x 7mm LGA package with an exposed paddle. The device operates on a 3.3V supply with less than 3.2W of total power dissipation.