Skyworks Introduces New Frequency Synthesizer for Land Mobile Radios

Skyworks has introduced the SKY72310-11, a 50 MHz to 2.1 GHz fractional-N frequency synthesizer for high-performance Land Mobile Radio / Professional Mobile Radio (LMR/PMR) systems. This synthesizer is a key building block of a phase-locked loop (PLL), providing ultra-fine frequency resolution and low phase-noise performance.  Its low power consumption of 4 mA @ 3V, 900 MHz provides extended battery life. Utilizing a configurable Delta Sigma architecture, a 10 or 18-bit modulator enables system designers to tradeoff step size, phase noise, and reference spurious performance. The SKY72310-11 simplifies transmitter designs and is ideal for rugged portable and mobile two-way radios used in business as well as and mission-critical applications. 

The SKY72310-11 provides ultra-fine frequency resolution, fast switching speed, and low phase-noise performance. This synthesizer 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 synthesizer to be used in very narrowband wireless applications. With proper temperature sensing or through control channels, the synthesizer’s 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 ovenized crystal oscillators, reducing parts count and associated component cost. The device’s fine step size can also be used for Doppler shift corrections. 

Reference crystals or oscillators up to 50 MHz can be used with the SKY72310-11. The crystal frequency is divided down by independent programmable dividers (1 to 32) for the synthesizer. The phase detector can operate at a maximum speed of 50 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 μs can be achieved. The lower in-band phase noise also permits the use of lower cost Voltage Controlled Oscillators (VCOs) in customer applications.