Spectrum Elektrotechnik GmbH

INTRODUCTION: Lightning has potential damaging effects on electronic equipment. Therefore modern equipment usually incorporates surge suppressors in the RF path in order to protect the equipment.
Spectrum Elektrotechnik GmbH has developed several types of lightning surge suppressors. They were engineered especially for the cellular communications industry. The designs are usually employing in the connector or the adapter a built-in fuse. But it has to be noted that the surge suppressor needs maintenance and replacement as soon as it has done its job of protection.
Another method for protecting the circuits against lightning, is the use of quarter wave stub devices. They have the advantage of being maintenance free, offer high attenuation and effectively a short circuit to incoming pulses outside the operating frequency. On the other hand they have the big disadvantage of needing to be tuned by the stub length to the center frequency, the equipment is working at, and have an operating bandwidth which is very narrow and usually only in the range of only +/- 70 MHz around the center frequency.

Application: Not protecting equipment against lightning strikes and allowing the energy of the surge to enter the equipment is a quite dangerous practice and usually ends up in destroyed equipment.
Lightning surge suppressing devices are therefore likely to be found in most applications, especially when modern systems are being designed. The protection of the equipment of cellular communication base station, connected directly with the antenna is one of the most important criteria.
Good applications for surge suppressors are also the protection of transceivers of radios on vehicles. The arc suppression device is usually built into the input connector at the long whip antenna.

Connectors: Surge Suppression devices are available with a large variety of connectors, such as 7/16, HN, N, SMA, etc., meeting the appropriate standard interface specifications, such as MIL-Standards, DIN- or IEC- Specifications.

Custom Designs: Designs have been made to suit particular specifications, such as unique mechanical outline, unusual mounting, special electrical requirements, rough environment, etc., etc. Experienced engineers are available and they are interested to hear about the system needs and they are eager to offer solutions that meet exactly the requirements needed in the application.

Frequency: The frequency range for the connectors and adapters being equipped with surge suppression is usually below 3.0 GHz.
Operating Temperature Range: The temperature ranges from -54�C to +125�C, or even wider, depending on the application, the design and the materials used. Engineering can usually offer something that fits perfectly the system use.

Risetime/Voltage: Depending on the design and the type of fuse being incorporated, the devices will trigger in microseconds, or even nanoseconds. The pulse rise time is normally very fast and measured in kV/�s.

VSWR: VSWR is the ratio of the reflected signal and the incident signal. Because of the built in fuse, incorporated in the RF path, electrically the device is not ideal at all anymore. But as the fuse is normally small, compared to the wavelength of the operating frequency, the voltage standing wave ratio is in general still good enough for the application, or in other words: a degredation in VSWR is not noticeable. Corrective actions integrated in the design, will help in addition to keep the reflected signal to a minimum.

Schematic cross section view of a lightning surge suppressor, to demonstrate the structural arrangement between outer conductor, center conductor and fuse.

The picture shows a four hole flange mount adapter with surge suppression, being used between the antenna and the vehicle mount radio equipment.