The SKY73134-11 is a wideband integer-N frequency synthesiser with an approximately 6 GHz locking range. It includes four differential voltage controlled oscillators (VCOs) which cover the output frequency range from 2,8 GHz to 6,2 GHz. By applying internal VCO division by 1, 2, 3, 4 or 8, the output frequency range can be increased from 0,35 GHz to 6,2 GHz, monitored at the RF output.
The direct, non-divided internal VCO frequency can also be monitored at the bidirectional VCO pins. The VCO selection can be automatic based on the target RF output. The device’s flexible configuration allows the loop to be locked by an external VCO or external phase locked loop (PLL), or the device can use the divider chain only.
The SKY73134-11 is controlled by a bidirectional read/write serial to parallel interface. It is manufactured with a BiCMOS 0,18 m SiGe process and provided in a compact, 32-pin RF land grid array (RFLGA).
The SKY72300-362 direct digital modulation fractional-N frequency synthesiser provides ultra-fine frequency resolution, fast switching speed and low phase-noise performance. This synthesiser is a key building block for high-performance radio system designs that require low power and fine step size.
The ultra-fine step size of less than 100 Hz allows this IC to be used in very narrowband wireless applications. With proper temperature sensing or through control channels, this fine step size can compensate for crystal oscillator or intermediate frequency (IF) filter drift. As a result, crystal oscillators or crystals can replace temperature-compensated or ovenised crystal oscillators, reducing parts count and associated component cost. The device’s fine step size can also be used for Doppler shift corrections.
The SKY72300-362 has a phase noise floor of –90 dBc/Hz up to 2,1 GHz operation as measured inside the loop bandwidth. This is permitted by the on-chip low-noise dividers and low divide ratios provided by the device’s high fractionality.
Reference crystals or oscillators up to 50 MHz can be used with the SKY72300-362. The crystal frequency is divided down by independent programmable dividers (1 to 32) for the main and auxiliary synthesisers. The phase detectors can operate at a maximum speed of 25 MHz, which allows better phase noise due to the lower division value.
With a high reference frequency, the loop bandwidths can also be increased. Larger loop bandwidths improve the settling times and reduce in-band phase noise. Therefore, typical switching times of less than 100 seconds can be achieved. The lower in-band phase noise also permits the use of lower-cost voltage controlled oscillators (VCOs) in customer applications.
The SKY72300-362 has a frequency power steering circuit that helps the loop filter to steer the VCO when the frequency is too fast or too slow, further enhancing acquisition time. The unit operates with a three-wire, high-speed serial interface.
A combination of large bandwidth, fine resolution and the three-wire, high-speed serial interface allows for a direct frequency modulation of the VCO. This supports any continuous phase, constant envelope modulation scheme such as FM, FSK, MSK or GMSK. This capability can eliminate the need for in-phase and quadrature (I/Q) digital-to-analog converters, quadrature up-converters, and IF filters from the transmitter portion of the radio system.
The device is packaged in a 24-pin QFN package.
Finally, the SKY74038 is a complete, low-power 2,6 GHz/800 MHz dual frequency synthesiser that provides both RF and IF channels. Fractional-N operation offers low phase noise, fast settling time and low spurious tones for RF channels. A standard integer-N division is used for IF channels.
The three-wire serial interface provides programmable control of the frequency synthesiser to support dual-conversion transceivers. The SKY74038 is available as a 20-pin TSSOP (-13 option) or as a lead-free 20-pin TSSOP (-21 option).
For more information contact Marinus Rudman, Hi-Q Electronics, +27 (0)21 595 1307, [email protected], www.hi-q.co.za
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