Over-the-Air System Noise Temperature Measurement of Active Integrated Antennas in a Reverberation Chamber

Low noise receivers play an essential role in wireless systems in radio astronomy and 5G/6G applications. Especially in radioastronomy, the received signal strength is very weak. Therefore, maintaining a good Signal-to-Noise Ratio (SNR) is quite important. A known concept to reduce the system noise temperature is to use noise matching for the Low-Noise Amplifier (LNA) and the antenna to get the optimal SNR. Due to the integrated nature of these systems, it is challenging to measure the noise performance of the total system accurately. For example, existing methods such as the Radiometric or the G/T method can be sensitive to inaccuracies due to the dependency on the sky noise temperature, the radiation pattern of the antenna, or the size of the antenna [1, 2]. Therefore we developed a new method, which can estimate the Noise Figure (NF) of a wireless system over-the-air (OTA), independent of these factors. The new method uses the Reverberation Chamber (RC) to create a consistent and repeatable environment. The uniform behavior of the RC makes the method independent of the radiation pattern of the antenna. This method measures the integrated antenna as one system, so the efficiency of the antenna, the NF of the LNA, and the noise matching between the Antenna and LNA are all taken into account.

Low noise receivers play an essential role in wireless systems in radio astronomy and 5G/6G applications. Especially in radioastronomy, the received signal strength is very weak. Therefore, maintaining a good Signal-to-Noise Ratio (SNR) is quite important. A known concept to reduce the system noise temperature is to use noise matching for the Low-Noise Amplifier (LNA) and the antenna to get the optimal SNR. Due to the integrated nature of these systems, it is challenging to measure the noise performance of the total system accurately. For example, existing methods such as the Radiometric or the G/T method can be sensitive to inaccuracies due to the dependency on the sky noise temperature, the radiation pattern of the antenna, or the size of the antenna [1, 2]. Therefore we developed a new method, which can estimate the Noise Figure (NF) of a wireless system over-the-air (OTA), independent of these factors. The new method uses the Reverberation Chamber (RC) to create a consistent and repeatable environment. The uniform behavior of the RC makes the method independent of the radiation pattern of the antenna. This method measures the integrated antenna as one system, so the efficiency of the antenna, the NF of the LNA, and the noise matching between the Antenna and LNA are all taken into account.

The first results of this method show that the NF of an active integrated antenna can be determined within a 95% uncertainty margin of0.6dB, as shown in Figure 1. The uncertainty bar includes uncertainties in the measurement equipment, cables, and antenna placement in the RC. We used a horn antenna with a separate LNA connected to it to show a proof-of-concept. This allowed us to measure the system as a whole and separately to create a reference, where noise matching was taken into account. For the reference the antenna efficiency and amplifier NF are estimated using the 3-Antenna approach by Holloway and the Y-Factor method. The result shows that the error bars of both the new and reference methods overlap, which means the results are in good agreement.

To the best of the authors’ knowledge, this is the first time an OTA noise figure measurement is performed independent of the sky noise temperature, antenna placement, and antenna radiation pattern and gain. These results show that the new method can be applied to determine the NF of active wireless systems. It is important to note that this method also includes factors such as noise matching because the NF of the total system is characterized.