The ADF41513 is an ultralow noise frequency synthesizer that can be used to implement local oscillators (LOs) as high as 26.5 GHz in the upconversion and downconversion sections of wireless receivers and transmitters.The ADF41513 is designed on a high performance silicon geranium (SiGe), bipolar complementary metal-oxide semiconductor (BiCMOS) process, achieving a normalized phase noise floor of −235 dBc/Hz. The phase frequency detector (PFD) operates up to 250 MHz (integer N mode)/125 MHz (fractional-N mode) for improved phase noise and spur performance. The variable modulus, ∑-Δ modulator allows extremely fine resolution when using a 49-bit divide value. The ADF41513 can be used as an integer N phase-locked loop (PLL), or it can be used as a fractional-N PLL with either a fixed modulus for subhertz frequency resolution or variable modulus for subhertz exact frequency resolution.A complete PLL is implemented when the synthesizer is used with an external loop filter and voltage controlled oscillator (VCO). The 26.5 GHz bandwidth eliminates the need for a frequency doubler or divider stage, simplifying system architecture and reducing cost. The ADF41513 is packaged in a compact, 24-lead, 4 mm × 4 mm LFCSPApplicationsTest equipment and instrumentationWireless infrastructureMicrowave point to point and multipoint radiosVery small aperture terminal (VSAT) radiosAerospace and defense