Antenna Arrays and Performance Testing

Key Takeaways

• The use of antenna arrays can compensate for the high free space path loss caused by multiple antennas. 

• Through antenna array performance tests, engineers can confirm the suitability of a selected antenna array for a given application. 

• The performance of active array antennas with several frequencies, beam states, and transmit and receive modes can be evaluated using a method called spherical near-field scanning.

Antenna array performance tests evaluate antenna characteristics

5G is the future of communication. 5G networks not only offer enhanced broadband, highly reliable, low latency communication, and massive machine type communication—they also ensure low operational costs and enhanced capacity with higher flexibility. To achieve high throughput within budget, 5G systems employ antenna arrays.

The beamforming characteristic of antenna arrays significantly helps in reducing energy consumption, increasing gain, and improving directivity. Antenna arrays are widely used in present-day communication systems to obtain higher gain and narrow beamwidth. As the application increases, it is necessary to conduct an antenna array performance test to evaluate its characteristics. In this article, we will discuss antenna arrays and their performance testing methods. 

Antenna Arrays

5G communication requires multiple antennas to increase the system capacity with higher flexibility. The frequencies utilized in most 5G systems are in the centimeter or millimeter range for achieving wider bandwidth and higher throughput. The drawback of using multiple antennas is the high free space path loss. The free space path loss given by the Friis equation is dependent on the frequency, antenna gain, and propagation environment.

One compensation method for high free space path loss is the usage of antenna arrays. Incorporating antenna arrays improves the performance and spectral efficiency of wireless communication systems. The beamforming property of antenna arrays helps in providing higher gain, and thus compensates for the free space loss that can be caused by multiple antennas. Antenna arrays utilize a higher number of antenna elements to obtain the property of beamforming. The more antenna elements in antenna arrays, the higher the gain and narrower the beamwidth. The use of antenna arrays reduces energy consumption as well. 

Phased Antenna Arrays

Phased array antennas are a type of antenna array used in commercial as well as military applications. Phased array antennas possess the properties of changing the shape and direction of the radiation pattern without physically moving the antenna. A phased array antenna consists of antenna elements that transmit individual signals. The gain, directivity, and performance of each antenna element add to the overall performance of the phased array antenna. We will discuss the types and methods of performance testing of phased array antennas in the upcoming sections. 

Types of Phased Antenna Arrays

Generally, phased array antennas can be classified into:

1. Passive electronically steered array or passive antenna array: In a passive antenna array, all antenna elements use a single transmitter. Each antenna element depends on a phase shifter to phase shift the electromagnetic signal to regulate the antenna beam as required.

2. Active electronically steered array or active antenna array: The drawback of a single transmitter in a passive antenna array is corrected by using an active antenna array. The active antenna array consists of separate transmitters for each antenna element. It can simultaneously transmit several electromagnetic waves of different frequencies in different directions.

3. Digital beamforming antenna array: In digital beamforming antenna arrays, each antenna element consists of digital receivers that digitize the signal. Field programmable gate arrays (FPGA) are used to digitally form antenna beams. 

4. Hybrid beamforming antenna array: Hybrid beamforming phased array antennas are a combination of passive and active antenna arrays. To form a full array, subarrays are combined. Multiple subarrays in hybrid beamforming antenna arrays help form clusters of simultaneous antenna beams. 

Active Antenna Array Performance Tests 

With the evolution of integrated circuit technology, active antenna arrays are widely used. An active array antenna consists of transmitting as well as receiving modules controlled by a central computer. These modules can be operated as phased array antennas in both transmit and receive mode.

The performance test for an antenna array is dependent on factors such as the geometrical configuration of the array, the distance between antenna elements, amplitude, phase, and radiation pattern from individual antenna elements. Let’s take a look at the performance test for active array antennas, called spherical near-field scanning.

Spherical Near-Field Scanning

The performance of active array antennas with several frequencies, beam states, and transmit and receive modes can be evaluated using a modern method called spherical near-field scanning. This method eliminates the need for conducting the classical antenna pattern measurement test on a far-field range having sufficient length to record the amplitude and phase quantities independent of distance. The spherical near-field scanning method makes the antenna pattern and permits the far-field criterion on the range length to be circumvented.

The antenna array performance test for active array antennas can be performed indoors in a controlled environment. The amplitude and phase array quantities determined in the near-field range length using spherical near-field scanning are transformed into far-field, and the result obtained is the desired far-field pattern. The spherical near-field scanning procedure is performed for each frequency, beam state, and mode associated with active antenna arrays.

Through antenna array performance tests, engineers can confirm the suitability of a selected antenna array for a given application. Cadence offers tools that can simulate the performance of antenna arrays. Subscribe to our newsletter for the latest updates. If you’re looking to learn more about how Cadence has the solution for you, talk to our team of experts.