Vcxo Circuit Design

The basic circuit for a vcxo consists of a standard crystal oscillator but with an electronic means of tuning or pulling the frequency slightly.

Vcxo circuit design. The design of a high performance voltage controlled oscillator vco is not is not a trivial task. The basic circuit for an vcxo comprises a standard crystal oscillator but with an electronic means of tuning or pulling the frequency slightly. A clock generator is an oscillator that provides a timing signal to synchronize operations in digital circuits. Good detective work requires that you have a grasp of the fundamental problem which leads to better engineering solutions rather than just choosing another crystal or vcxo circuit.

This requires sound theoretical design followed by careful choice of all the components and then a good pcb layout. Tcxos use an element known as a voltage controlled crystal oscillator vcxo. Consideration of the circuit components used and the layout all play a role in determining the performance. Nonlinear effects in vcos.

Apart from that there are dedicated ic packages like lm566 lm567 etc. Also op amps multivibrator transistors 555 timers can also be utilised to build oscillating circuits. This is almost invariably achieved by using varactor or varicap diodes. Vcxo clock clk generators have been used in various applications such as digital tv digital audio adsl and stb.

A common design requirement is to frequency or phase lock a transceiver output to an input source known as loop recovered or slave timing. Included is a temperature sensor that when the temperature changes will apply a small correct voltage to a varactor which then produces a frequency that is equal and opposite to the change in frequency produced by the temperature. This application note provides the general structure for a vcxo clk generator key performance measurements guidelines for pcb design and a test setup for max9485 a vcxo clk gen chip for mpeg2 and ac 3 audio applications. This is almost invariably achieved using varactor or varicap diodes.

There are many types of vco circuits. Misbehaving vcxo will bring down the whole system the trick will be to prove that the vcxo is the culprit easier said than done. Oscillator circuit nonlinearities cause low frequency noise components to be up converted and to appear as noise sidebands on the vco output. In this application note transceiver refers to these types of transceivers.

Vcxo clock generators are used in many areas such as digital tv modems transmitters and computers. Design parameters for a vcxo clock generator are tuning voltage range center frequency frequency tuning range and the timing jitter. In most vcxos a pair of back to back diodes is placed across the crystal. Although this statement is intuitively obvious quantifying this mechanism is much more complex.

Crystal oscillator vcxo circuits by utilizing functionality within each serial gigabit transceiver. A very basic one can be built by just utilising a capacitor inductor and resistor to make a tank circuit.