Connected devices and mobile applications require wireless network access that is resilient, secure and able to protect individuals’ privacy. For this reason, a massive number of harmonized standards and specifications have been developed by the wireless industry. Conformance to these standards and specifications is the way to accomplish resilient and secure wireless access.
More specifically, ETSI/3GPP has released an extensive conformance test specifications (TS 136 521-1 for LTE and TS 138 521-1 for 5G NR) that stipulate how and to what levels the radio properties of a mobile device should be verified in order to enable high quality wireless access. Two important objectives for the conformance test specification are to detail requirements applicable for any mobile device with respect to:
- Transmitter output spurious emissions
- Receiver blocking characteristics
(Receiver blocking characteristic is a measure of the receiver’s ability to receive a wanted signal in the presence of an unwanted interferer.)
Appropriate testing and conformance to these requirements are needed to safeguard the quality of the wireless access for an individual user as well as for the overall network performance.
In some cases, the performance requirements – and hence the test levels – are so stringent that the capabilities of conventional test instruments are not enough. This is in particular the case for commercially available:
- Spectrum analyzers – that do not have the dynamic range needed to fully verify transmitter output spurious emissions
- Signal generators – that exhibit too much broadband noise to adequately verify receiver blocking characteristics
To address this, Ranatec has developed the RI 266 – a state-of-the-art, programmable notch filter. The RI 266 extends the dynamic range in spurious emission measurements with at least 30 dB by selectively suppressing the wanted transmitted signal, while leaving the spurious outputs unaffected. Similarly, the RI 266 can be set up to lower the noise level at the wanted receive frequency from any signal generator with up to the same amount, thus enabling adequate verification of receiver blocking characteristics.
The RI 266 is intended for both formal conformance testing, performed by accredited test houses, as well internal verification by mobile device vendors.
Typical Test Setup
For the purpose of doing conformance testing of mobile devices, a generic, automated test set-up is typically established.
The Signaling units emulates the Radio Access Network base stations / access points in both downlink and uplink. A set of standard lab instruments (typically power meters, a spectrum analyzer and a signal generator) are required for calibration of the various signal paths as well performing some of the actual measurements. All these parts of the generic test set-up are typically supplied by the tier 1 players within wireless test equipment (Anritsu, Keysight or Rohde & Schwarz).
At the center of this generic test set-up sits the parts supplied by Ranatec:
- Signalling Selection and MIMO Multiplexing contains the programmable switches, couplers and attenuators needed to accommodate the adequate signal constellation in both uplink and downlink
- Signal Routing is the core of the test automation and provides flexible routing and level setting across the test system, by means of programmable switches, couplers and attenuators
- Frequency Extension contains switchable high-pass and low-pass filters to allow for spurious emission measurements over the entire frequency range up to 26.5 GHz
- Programmable Notch Filter refers to the Ranatec RI 26X family of tunable band reject filters
- DUT and MIMO Multiplexing is the correspondence of the Signalling Selection and MIMO Multiplexing and provides and adequate signal constellation in both uplink and downlink to/from the devices under test
The actual test set-up depends on the overall ambition in terms of coverage of standards and frequency bands, type and number of DUT:s used, the selection of signaling units and lab instrumentations – as well as the ambition level in terms of level of automation. Ranatec has developed a flexible and easy to use test automation platform to support almost any ambition level, tailored to the customer demands. The key component in any such set-up is the RI26X family of programmable notch filters.
An example of such a test set-up is shown in the picture below.