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Inside Frequency Control

Common Applications for Clipped Sinewave TCXOs

Posted by Bliley Technologies on Aug 29, 2017 6:30:00 AM

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One of the most important decisions an RF engineer will make when designing a new system is choosing the right type of oscillator, and determining what signal output will be the best fit for the application. Each come with their own set of advantages and disadvantages. In this article, wer're talking about temperature controlled crystal oscillatos (TCXO) and the clipped sinewaves they produce. We'll cover the pros and cons of the TCXO and its signal type, as well as some common applications that these oscillators are used with.

TCXO Explained

We’ve talked a lot about oven-controlled crystal oscillators (OCXO), which make use of a special enclosure (the oven) to maintain a consistent temperature around the crystal. As the name implies, the TCXO serves the same purpose but does it in a different way.

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 which is able to sense changes in ambient temperatures, and adjust the voltage applied to the crystal in an exact inverse to these changes. Correcting the voltage in this way allows it to cancel out the effects of changes in the surrounding air temperature, and keep the frequency stable.

OCXOs generally have the best performance in terms of reducing phase noise. However, TXCO 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 an oven-controlled design. In many applications, a TCXO is a more economical and technically sound choice.

Be sure to check out our TCXO guide for a more detailed explanation of how TCXO technology works and how it relates to crystal stability and aging.

Where do Clipped Sinewaves Fit Into This?

Sinewave outputs are the natural, default output of a crystal oscillator. Such signals will have a “pure” sinusoidal shape resembling rounded peaks and valleys. “Clipped” sinewaves, 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 sinewave outputs have a lower power draw than full digital logic outputs and are ideally suited for TCXO designs.

What Applications Make Use of Clipped Sinewave TCXO Designs?

Clipped sinewave TCXO designs are a great fit for small devices where power availability is limited. TCXOs are widely used in telecommunications applications, positioning, navigation 

iphone-6-apple-ios-iphone-50603.jpegand timing (PNT) systems, and more. For years, these types of designs have been used in cell phones, tablets, portable radios and other mobile electronics. They are also commonly used in GPS devices, and microwave and satellite communication systems. As the “Internet of Things” continues to expand and advance, many of these new, connected devices will make use of TCXO designs as well.

If you’re looking for a combination of low cost, minimal power consumption, and high performance, a clipped sinewave TCXO might be just the right solution.

At Bliley Technologies, we have over 80 years of experience working with crystal oscillator tech, 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 selection of TCXO products today and see what makes us different.

Common Oscillators

Topics: crystal oscillators