Data Sheet

HMC1166

Rev. 0 | Page 9 of 12

THEORY OF OPERATION

The HMC1166 voltage controlled oscillator is a free running

voltage controlled frequency source. The output frequency is

controlled by applying a variable tune voltage to the VTUNE port.

Because VTUNE is varied from the lowest to the highest allowed

voltage, the VCO output frequency increases from the lowest to

the highest operating frequency. This VCO output frequency

change with the applied VTUNE input results in the VCO

frequency sensitivity characteristic (MHz/V). The VCO

frequency sensitivity is not constant and varies across the

tunable range.

The HMC1166 VCO is specified to cover the minimum to

maximum frequencies specified in this data sheet over the entire

specified temperature range, including the VCO frequency drift

(MHz/°C). In addition, for low phase noise operation, drive the

VTUNE port from a low noise voltage source. Excessive noise

on the VTUNE port results in poor phase noise performance.

The tune port modulation bandwidth is typically greater than

10 MHz.

To achieve optimum VCO phase noise performance when using

the HMC1166, it is important to use a low noise power supply

use low noise regulators, otherwise, bias line noise may corrupt

the low phase noise output of the HMC1166.

Internally, the radio frequency (RF) output frequency is generated

from a doubler circuit. This generation results in an unwanted

low level output signal present at half the RFOUT frequency

(RFOUT/2). If necessary, this undesired spurious signal can be

further filtered on the customer application board using a band

pass filter. The RFOUT/2 output signal is available directly at the

RFOUT/2 port. The RFOUT/2 port commonly drives a phase-

locked loop (PLL)/synthesizer for phase locking the HMC1166

output if needed.

Lastly, the HMC1166 RFOUT port incorporates an internal

buffer amplifier to provide good output matching. The internal

buffer amplifier also isolates the VCO core from the output load

and minimizes the VCO frequency change with the changes to

the output load impedance (pulling).