Special applications of the relay switching unit KRE-4000

Andreas Weiss

In News Posted

Our KRE-4000 series relay switching units are mainly used for the automation of EMC tests. They control the switching between the individual power amplifiers to enable a broadband measurement according to test standard without manual switching. The selection of the relays is done individually according to the customer’s requirements (frequency range up to 50 GHz possible). However, the application of the switch panels from MTS Systemtechnik is not limited to this relatively simple case. By means of examples the flexible application of this powerful device concept will be shown.

Amplifier matrix KVE-1/6/1-TFRO

It serves as a remote preamplifier in the shielding chamber. In order to cover the required frequency range from 100 kHz to 26.5 GHz, five different low noise amplifiers are built in, which can be optionally switched into the signal path via RF relays. The LNAs have a noise level in the range from ±1.0 dB typ. to ±2.0 dB typ. and a gain between 31 dB and 50 dB. The four amplifiers operating above 1 GHz each have an additional bandpass filter to protect the input. To ensure that as few interference signals as possible are emitted from the matrix, the included power supply unit is longitudinally regulated and the control input is designed as a fiber optic connection.

Amplifier matrix

Relay switching unit KRE-4123-ESCU

This simple switching unit is used to select up to four different network simulations for a test receiver by means of built-in RF relays. In addition, 10 dB or 20 dB attenuation can be switched into the signal path if required. The unselected LISN’s are terminated with 50 Ω each. A maximum input power of 50 W CW per connection is possible. The device can be operated via RS-232, via USB, as well as by means of the built-in touch panel display.

Relay Switching Unit

Switching matrix MX-3/6/3-MASTER / MX-2X6/3-SLAVE

This complex 4-way matrix makes it possible to remotely distribute six different RF power amplifiers flexibly to three different neighbouring shielding chambers. Each shielded chamber is assigned a signal generator and two power meters (see picture), which always switch synchronously with the shielded chambers. This comfortable switching device allows an optimal utilization of very expensive investment (HF power amplifier) and saves high costs.
The matrix can be controlled by three different IEEE-488 interfaces (one per shielding chamber). It is not possible to select an amplifier that is already connected to another shielding chamber, so that no measurement in progress may be interrupted.
As a special feature there is also an interlock connection for all three shielding chambers. This ensures that the selected amplifier does not receive an input signal at any time when the door is open by switching the input to a 50Ω termination. Additionally, there is an interlock output for each amplifier. For safety reasons, the connection is electromechanical and therefore independent of the firmware.
The matrix has a minimum isolation of 110 dB and can be used up to 6 GHz. The power section of the matrix can be loaded with a maximum of 1000 watts CW up to 1 GHz and 400 watts CW up to 6 GHz with an insertion loss of only 1.5 dB up to 4 GHz and 2.0 dB up to 6 GHz.

Switching Matrix


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