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TCXO, Temperature Compensated Crystal Oscillator

As the name indicated a temperature compensated crystal oscillator provides a means of counteracting the frequency change caused by temperature change in a crystal oscillator.

The letters TCXO stand for Temperature Compensated Xtal Oscillator - Xtal is short from crystal and implies a quartz crystal resonator. The TCXO module is able to provide considerably improved performance over that of a standard crystal oscillator, especially in terms of frequency stability over a temperature range.

By measuring the temperature and applying a correction voltage to a VCXO, the frequency stability over a temperature range is considerably improved whilst keeping costs low - using an oven controlled crystal oscillator, OCXO would be considerably more costly and much larger in size.

Often a wide range of TCXOs of varying frequencies, supply voltages and packages is available from many distributors, enabling these electronic components or modules to be used in many general electronic designs, RF circuit designs, etc.

Temperature performance of crystal oscillator

Crystal oscillators are able to provide a much better level of performance than that provided by LC resonator circuits. Nevertheless crystal oscillators are still affected by temperature.

TCXO solution

TCXO adjusts the frequency of the oscillator to compensate for the changes that will occur as a result of temperature changes. To achieve this, the main element within a TCXO is a Voltage Controlled Crystal Oscillator, VCXO. This is connected to a circuit that senses the temperature and applies a small correction voltage to the oscillator as shown below.

INTRODUCTION

The history of the development in crystal filter technology, from the initial concepts of Cady to the current wide range of products, provides a fascinating chapter in the development of today’s highly complex electronic products. The crystal filter has been a particularly critical element in the development of narrowband communications systems. The desire to send multiple voice messages on a single telephone line resulted in the introduction of carrier telephone systems in 1916. These early systems used LC filters in the 10 to 40 kHz frequency range. However, the bandwidth limitations caused by realizable coil Q’s were quickly recognized. In 1929, W.P. Mason of Bell Laboratories developed methods for incorporating crystals into LC lattice filter networks. This work resulted in the development of a 60 to 108 kHz basic group-band filter set used to frequency multiplex 12 voice channels. This work is described in Mason’s 1934 paper which was the basis for essentially all crystal filter designs generated during the next 20 years. During this period the major application for crystal filters was in carrier telephone equipment. However, in the mid-1950s, newer narrowband radio communications systems were developed both for military and commercial use which required high-frequency, stable, narrow-bandwidth filters. In most cases, crystal filters were the answer for these filtering applications and a new manufacturing industry was formed to supply these needs. Other applications quickly followed in navigation and radar equipment, in new fire-control systems, and missile control systems. This increased level of activity resulted in new filter design procedures and substantial improvement in the quality of high-frequency filter crystals.

Ceramic Filtration

Locally manufactured ceramic filters have traditionally been used throughout the world to treat household water. Currently, the most widely implemented ceramic filter is the Potters for Peace design. The filter is flowerpot shaped, holds about 8-10 liters of water, and sits inside a plastic or ceramic receptacle. To use the ceramic filters, families fill the top receptacle or the ceramic filter itself with water, which flows through the ceramic filter or filters into a storage receptacle. The treated water is then accessed via a spigot embedded within the water storage receptacle. The filters are produced locally at ceramics facilities, and then impregnated with colloidal silver to ensure complete removal of bacteria in treated water and to prevent growth of bacteria within the filter itself. Numerous other locally-made and commercial ceramic filters are widely available in developed and developing countries. The filter is flowerpot shaped, holds about 8-10 liters of water, and sits inside a plastic or ceramic receptacle. To use the ceramic filters, families fill the top receptacle or the ceramic filter itself with water, which flows through the ceramic filter or filters into a storage receptacle. The treated water is then accessed via a spigot embedded within the water storage receptacle. The filters are produced locally at ceramics facilities, and then impregnated with colloidal silver to ensure complete removal of bacteria in treated water and to prevent growth of bacteria within the filter itself. Numerous other locally-made and commercial ceramic filters are widely available in developed and developing countries.

What Is a Ceramic Resonator?

ceramic resonator is an electric component that exhibits a series resonant and a parallel resonant center frequency. It exhibits a piezoelectric characteristic that makes the ceramic material generate minute electrical energy when subjected to electromechanical expansion and compression. The resulting mechanical energy component produces the electric component and vice versa, and the result is a complex reactance that leads to resonance observed as the characteristic of having a center frequency. Materials such as lead zirconium titanate have a ceramic piezoelectric characteristic.

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