Anirudh Venkatesan, Mini-Circuits Engineering
The advent of 5G networks has already begun ushering in a whole new generation of wireless devices and applications, and device manufacturers are racing to be the first to market. In order to meet the 5G standard for commercial wireless communication, device manufacturers need to develop powerful transmitters and receivers that operate in the millimeter wave range. This comes with a number of challenges, one of which is testing and qualification. Due to the wireless nature of these devices, manufacturers need to conduct testing in real-world conditions, which isn’t possible using the conventional approach of connecting devices under test (DUTs) to instruments with coaxial cables. Over-the-air (OTA) testing allows engineers to more realistically simulate real-world device performance in the lab environment.
OTA testing uses antennas instead of cables to transmit and receive RF channel power. It is often conducted in anechoic chambers where designers can introduce different conditions such as interfering signals and monitor any effects on performance. Since most communication devices include both transmit and receive capabilities, both the transmit power and receive sensitivity need to be tested. Each path requires a different setup, but both cases require the use of suitable wideband amplifiers, either to drive power to the antenna on the transmit side or to amplify small signals on the receive side. Emerging applications in the 5G New Radio FR2 frequency bands (n257, n258, n259, n260, n261) necessitate high-performance amplifiers with specific noise figure and output power specifications over wide bandwidths up to 40 GHz and higher.
This article will briefly describe common test setups for OTA testing of transmit and receive signal chains and illustrate uses for Mini-Circuits’ ultra-wideband connectorized amplifiers within these setups. Note that in this article, we will be considering a cell phone as the DUT for illustration, but the same tests are applicable for other wireless devices as well.
Total Radiated Power (TRP)
Total Radiated Power (TRP) testing measures the total power radiated by a transmitter in a cell phone or other device in a given RF channel. This involves testing how much power is delivered to the cell phone’s antenna by the RF power amplifier in the transmitter chain, and how good the antenna is at converting this RF power into radiated power. A typical TRP setup is shown Figure 1.
Figure 1: Simplified diagram of a Total Radiated Power (TRP) test setup.
This setup requires a low noise amplifier for the receiver front-end between the antenna and the spectrum analyzer. One such amplifier used by Mini-Circuits customers in such setups is the ZVA-24443G1+. With an operating frequency range from 24 to 43.5 GHz, this model is ideal for TRP testing in the 5G FR2 bands (up to n259). It has a nominal gain of 45 dB with gain flatness of ±3 dB and a low noise figure of around 1.7 dB. Selected specs for this model as well as the ZVA-18403G+, also suitable for TRP testing in the 5G FR2 bands, are shown below in Table 1.
|Model No.||Freq. Range (GHz)||Gain (dB)||Gain Flatness (dB)||Noise Figure (dB)|
|ZVA-24443G1+||24 – 43.5||45||±3||1.7|
Table 1: Wideband LNAs suitable for high-frequency TRP testing.
Total Isotropic Sensitivity (TIS)
The purpose of Total Isotropic Sensitivity (TIS) testing is to measure the cell phone antenna’s ability to receive low power signals. This is an iterative process that involves measuring the power received by the cell phone in a given RF channel. The measurement involves incrementally reducing the power at the setup transmitter antenna and measuring the bit error rate (BER) at the cell phone. Once a specified maximum BER is reached, the corresponding received power is recorded as the sensitivity. A typical TRP set up is shown Figure 2.
Figure 2: Simplified diagram of a Total Isotropic Sensitivity (TIS) test setup.
The transmit antenna of the setup sends the test signal to the cell phone’s antenna. The signal power is boosted by an amplifier to compensate for the path loss such that useable power is received at the cell phone’s antenna. In this case, the amplifier in the setup acts as a typical power amplifier in a transmit chain. Therefore, it needs to have a sufficient output power for an accurate measurement. Again, for 5G OTA measurements, these power amplifiers need to have a relatively high output power at high frequencies up to 40 GHz and beyond.
Mini-Circuits’ ZVA-24443G1+ discussed above has also proved useful in TIS testing, with an output power at 1 dB compression (P1dB) of +23 dBm. For higher output power with even wider frequency coverage, Mini-Circuits’ new ZVE-453+ series of wideband medium power amplifiers are ideal for TIS testing setups. Specs for these models are summarized in Table 2 below. Performance curves for gain and output power are shown in Figure 3. All models in the ZVE-453+ series operate on a single, positive supply voltage from 10 to 15V and feature internal voltage regulation and sequencing as well as built-in over-voltage and reverse voltage protection. They’re available from stock with and without a heatsink and 2.4 mm RF connectors. An optional PSAT control pin and 2.92 mm connectors are also available on request.
|Model No.||Freq. Range (GHz)||Gain (dB)||Gain Flatness (dB)||P1dB (dBm)|
|ZVA-24443G1+||24 – 43.5||45||±3||+23|
Table 2: Amplifiers suitable for high-frequency TIS testing.
Figure 3: Typical gain and output power performance for Mini-Circuits’ ZVE-453+ series of wideband medium power amplifiers.