Spectrum Elektrotechnik GmbH

INTRODUCTION: Impedance Transformers are passive linear coaxial components used to transform 50 Ohms impedance levels to 75 Ohms impedance levels or vice versa.

Application: Impedance Transformers are mainly used to connect components and measurement systems of different impedances. Signal sources and test systems using 50 Ohms impedances are mostly used. Some test systems may even be only available with 50 Ohms impedance. Employing an Impedance Transformer means that these 50 Ohms systems can be used for testing 75 Ohms components.

Resistance Network Impedance Transformers: These components are using a resistor network to transform from 75 Ohms to 50 Ohms or vice versa. As the resistors need to be small for integration into the coaxial circuit, and because of little reflections, the component is only specified for low power, normally 0.5 Watts, or even less. The operating frequency is only to a few hundred MHz, e.g. DC to 200 MHz. The insertion loss is high. Often the component is designed to have a voltage insertion loss of 10 dB.

Multiple Quarterwave Impedance Transformers: The unit consists of multiple sections of quaterwave length, properly cascaded for optimum performance and broad band properties. The operating bandwidths may be to 3.0 GHz with a max. insertion loss of 5 dB, an average power of 2 Watts and a peak power of 2 KW.

Inductive Impedance Transformers: These components consist of two windings, linked by a mutual magnetic field. The relationship between impedance of input and output depends on the ratio of the number of windings between primary and secondary coil. These components have low loss, but are only usable at lower frequencies. Normally the design is not used at all in coaxial Impedance Transformers.

Average Power Handling: This is the maximum allowable CW power to which the unit can be subjected to without suffering permanent damage.

Connectors: Impedance Transformers can be fitted with a number of connector styles. Of special interest are: N(50 Ohms) to N(75 Ohms), BNC(50 Ohms) to BNC(75 Ohms), TNC(50 Ohms) to TNC(75 Ohms), and 1.8/5.6 to 1.6/5.6. For special applications also units can be offered with different connector styles at the input and output.

Custom Designs: Spectrum Elektrotechnik GmbH has been designing and supplying special Impedance Transformers to suit particular requirements, such as certain bandwidths, unique mechanical outline, unusual mounting or special connector requirements, etc., etc.

Frequency and Bandwidth: As 75 Ohms systems are usually designed to operate at lower frequencies, there seems to be no need for Impedance Transformers operating at higher frequencies. Depending on the designs, Impedance Transformers may operate up to a few hundred MHz, only some are designed for frequencies to 3.0 GHz.

High Reliability Components: Impedance Transformers can also be supplied to Customers High Reliability Specifications, environmental, military or governmental requirements, and/ or to customer test procedures.

Impedance Transformers for other impedances: Basically a unit for any impedance transformation needed, can be designed. Depending on the operating frequency and bandwidth, the appropriate design will be chosen for low development cost.

Insertion Loss: This is the amount of power lost through the Impedance Transformer under matched conditions.

One dB Bandwidth: This is the frequency range over which the insertion loss variation is less than 1 dB, referenced to the midband insertion loss.

Operating Temperature Range: The temperature ranges from -54�C to +125�C, or even wider, depending on the application.

Peak Power Handling: This is the maximum allowable power to which the unit can be subjected to without suffering permanent damage, or without changing permanently the specified characteristics of the device. The peak power is transmitted at a certain pulse width and pulse repetition rate.

Standard Products: Although a number of products have been supplied to customers' orders, a standard product line on Impedance Transformers has not been designed yet. But there is a possibility that the product required has been designed already or that a design, very close to the requirement exists. Therefore please check your requirements with our sales force, or our engineering staff.

VSWR: VSWR is the ratio of the reflected signal and the incident signal. It is desired that the Impedance Transformers have little reflections. In reality, the units will show some reflections and discontinuities within the circuit, as no design is perfect, and manufacturing tolerances do not allow perfect designs anyway.