Abstract
The frequency of analog signals or the data rate of digital signals is continuously increasing. For many high frequency applications like wireless telecommunication, CATV, ATE etc. relays are needed to switch these signals. With the HF3 relay Tyco Electronics AXICOM offers a low cost, high performance, high frequency relay capable to handle signals up to 3 GHz. Excellent isolation, insertion loss and V.S.W.R. is provided to the highest frequency level. It offers currently the smallest physical dimensions and surface mount capability for cost effective assembly processes.
1. Introduction
The frequency level of signals in telecommunication e.g. wireless, CATV and ATE applications are constantly increasing due to increasing transmission rates. Standard telecom and signal relays cannot handle signals higher than 500 Mhz as they do not have the required characteristics (insulation, impedance and insertion loss etc.). All mentioned broadband applications, which are all emerging markets, are working with signals between 1 and 3 GHz.
Electromechanical relays have following advantages over semiconductor switches:
- Contacts do not cause any signal distortion as amplitude distortion, phase distortion, cross modulation, or mutual modulation
- Open contacts are gas insulated providing excellent high frequency insulation
- Metal contacts are suppressing insertion loss.
- High Frequency characteristics of electromechanical relays are not influenced by temperature
As discussed above, electromechanical switches have significant advantages compared to semiconductor solutions for high frequency applications. The major disadvantages so far where the big dimensions, the high cost and the missing SMD capability for the breakthrough on the market. The target for the development of the HF3 relay was the combination of the well known high frequency performance advantages with the surface mount technology (SMT) and manufacturing technology of standard telecom-relays. The result is a synthesis of an excellent RF design technology with a well proven highly efficient manufacturing technology, which allows to achieve interesting manufacturing costs.
Product Description
The HF3 relay is a high frequency relay suitable to handle signals up to 3GHz. With outside dimensions of 15 x 7,5 x 10 mm it is currently the smallest design on the market and one of the only RF relays which can be soldered with SMD processes.
Two versions with different impedance (50 and 75 O )are available in order to serve both main application fields. ATE and wireless communications which both require a 50 O and CATV and satellite receivers which require a 75 O impedance.
2. HF3 Relay - Design and Characteristics
Basically for the internal design of RF relays three design principles can be applied as shown in Figure 1. All design principles consist of a signal layer, ground layer and a dielectric layer where the electric field is concentrated between signal and ground layer. Micro-strip and coplanar designs are widely used for RF PCB designs, whereas a coaxial design is used for cables. In order to realize a 50 O version as well as a 75 O version the coplanar design principle offers better possibilities to realize both versions in similar designs, which can be manufactured on the same manufacturing line. The difference between the 50 O and the 75 O version is the width of the terminals and the dielectrics to achieve a perfect match of the relay impedance to prevent any signal reflection.
The actuator used for the HF3 relay is a high sensitive, polarized magnetic circuit working with low power consumption as non-latching as well as latching switching characteristics with 1 or to coils.
The design is based on a modified standard telecom relay suitable to apply high volume manufacturing methods, which ensure low manufacturing cost and a high quality manufacturing with low failure rate.
