OTA Testing of Electronically Scanned Antenna Arrays [Application Notes]

Phased arrays in the last decade have made tremendous progress, mostly as a result of the maturity of silicon beamforming chipsets. With 5G communication links on the horizon, silicon beamformers have been front and center and commercial development has been accelerated, and as a result price economies have scaled
[1]
. System-level considerations are now being made, specifically regarding the level of integration
[2]
,
[3]
,
[4]
,
[5]
,
[6]
,
[7]
. There have been many papers in the literature which document various high-performance phased arrays. Some notable published papers on this topic include
[8]
, which presents a dual-band multistandard 5G millimeter-wave phased array;
[9]
, an area-efficient 5G millimeter-wave transceiver front end;
[10]
, a K-band hybrid packaged phased-array receiver with integrated antenna array;
[11]
, a 33.5–37.5 GHz beamforming transceiver with hybrid architecture phase shifters;
[12]
, a wide-band transmit and receive phased array which operates from 16 to 52 GHz;
[13]
, which presents a silicon beamforming chip which can support
C
-,
X
-,
Ku
-, and
Ka
-bands;
[14]
, a dual-polarized transmit phased array for a common data link;
[15]
, a 1024-element satellite communication receive-only phased array;
[16]
and
[17]
, which present a wafer-scaled phased array that operates in the
G
-band; and finally,
[18]
, which presents a
D
-band submillimeter wave beamforming transceiver in silicon germanium (SiGe). Much of the focus of these papers has been on radio-frequency integrated circuit (RFIC) development, where silicon and SiGe afford the ability to support multiple channels and therefore tighter integration, as well as nuanced design and integration of the beamformer with a printed circuit board (PCB) antenna array. However, only a few papers describe the necessary steps, as well as the equipment needed, to do a line-of-sight (LOS), over-the-air (OTA) microwave link using digitally modulated signals. This is, after all, the final use case for these types of electronically scanned antenna arrays, the ability to close LOS microwave links.