Tunable Bandreject Filter for Carrier Aggregation Measurements

The Tunable Bandreject Filter

The Ranatec RI 268 Tunable Bandreject filter is designed to support spurious emission and receiver blocking measurements for communication units, such as mobile, bluetooth or WiFi devices. The filter is tuned to suppress the channel in use, to make good conditions for measuring very weak spurious signals close to it. It has consistent behaviour from 600-8000 MHz and very steep 10 MHz slopes at the filter edges.

In a carrier aggregation scenario, more than one channel are used simultaneously. Then all of them need to be suppressed at the same time. This can be achieved by using the RI 268 Tunable Bandreject Filter together with the RI 4278 Frequency Extension Box, which has a proper set of fixed low and high pass filters.

Dual Band Suppression

In order to suppress more than one operating channel, the Tunable Bandreject Filter and the Frequency Extension Filter Box are used in series. Below is a schematic of the RI 4278 Frequency Extension Box prepared for the proper connectivity.

We note that the box allows for switching in a lowpass or highpass filter of choice and then the RI 268 Tunable Bandreject Filter is integrated in the setup. This means that both a low or high band and the high performance bandreject frequencies will be suppressed simultaneously.

Carrier Aggregation Suppression Example

As an example, we consider spurious emission measurements close to the high side of a 10 MHz channel in mobile communication band 5 at 839-849 MHz when it is aggregated with band 1. We use a lowpass filter in the RI 4278 Frequency Extension Box to suppress band 1 at 1920-1980 MHz and at the same time tune the band reject filter to make its upper band reject edge align with the upper edge of the channel 5 frequency band. This is illustrated in the figure below.

We see that band 1 (filled blue) is indeed suppressed by the lowpass filter (blue line) and that band 5 (filled green) is suppressed by the tunable bandreject filter (green line). This provides for high dynamic range measurements within 860-1400 MHz. (As a bonus, we can also measure within 450-680 MHz.)

Similar arrangements need to be made for all measurements regions of all carrier aggregation channel combinations. Ranatec can offer support in sorting out the variations.

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If you would like more information about this topic, please call or e-mail Charlotte Ornstein at +46 317061660 charlotte.ornstein@ranatec.com.