Some of the most important decisions an RF engineer will make when designing a new system are choosing the right type of crystal oscillator and determining which signal output is the best fit for their application. Each type of oscillator and output signal comes with its own set of advantages and disadvantages.
In this article, we'll discuss temperature compensated crystal oscillators (TCXOs) and the clipped sine waves they produce. We'll also cover some of their most common applications.
What Are TCXOs & How Are They Different from OCXOs?
While oven controlled crystal oscillators (OCXOs) make use of a special enclosure (the oven) to maintain a consistent temperature around the crystal, TCXOs use a different method to cope with temperature changes
With a TCXO, there is no enclosure around the crystal to prevent ambient temperatures from affecting the frequency. Instead, the TCXO contains a compensation network that is able to sense changes in ambient temperature and adjust the voltage applied to the crystal in an exact inverse to these changes. Correcting the voltage in this way cancels out the effects of the surrounding air temperature and keeps the frequency stable.
Related: The TCXO Oscillator: 5 Elements of Temperature Compensated Oscillators
In many applications, a TCXO is a more economical and technically sound choice. Although OCXOs generally have the best performance in terms of reducing phase noise, TCXO designs typically only use about 1% of the current draw of an OCXO, making them ideal for devices where power supply is limited. They are also physically smaller than OCXOs and have shorter warm up times than oven-controlled designs.
Related: Temperature Compensated Crystal Oscillators (TCXOs): Performance & Common Types
What Are Clipped Sine Waves?
Sine wave outputs are the natural, default output of a crystal oscillator. Such signals will have a “pure” sinusoidal shape resembling rounded peaks and valleys. “Clipped” sine waves, however, are different: these waves are created by limiting the output of the signal to prevent it from reaching its normal highs and lows.
Clipping can be done gradually, so that the output still follows the original frequency path but at a reduced gain (soft clipping), or sharply so that it flattens out at the bottom of the wave and likewise reaches a flattened plateau at the top (hard clipping). Devices that generate clipped sine wave outputs have a lower power draw than full digital logic outputs and are ideally suited for TCXO designs.
Related: Which Crystal Oscillator Output Signal Is Best for Your Application?
Common Applications for Clipped Sine Wave TCXOs
Clipped sine wave TCXOs are a great fit for small devices where power availability is limited. TCXOs are widely used in telecommunications applications, positioning, navigation, and timing (PNT) systems, and more.
For years, TCXOs have been used in cell phones, tablets, portable radios, and other mobile electronics. They are also commonly used in GPS devices and in microwave and satellite communication systems. As the Internet of Things (IoT) continues to expand and advance, many connected devices will make use of TCXOs as well.
If you’re looking for a solution that combines low cost, minimal power consumption, and high performance, a clipped sine wave TCXO might be the answer.
Related: How TCXOs Improve Oscillator Stability & Aging with Low Power Consumption
Bliley Takes You Further
At Bliley Technologies, we have almost 100 years of experience working with crystal oscillators, providing solutions for defense and commercial systems across a wide variety of markets. We’re proud to design and manufacture some of the best TCXO designs on the market — all right here in the USA.
No matter what your needs are, we’ll help you find the right oscillator for your application. Explore our full line of TCXOs and see what sets our technology apart.
