A built-in antenna test system, BATS, comprising: a processing element; a measurement fixture; and an interface, wherein the interface is configured to position a device under test (150; 1706; 2202; 2302; 2420) DUT, inside the measurement fixture, wherein the interface provides power and data connections to the DUT (150; 1706; 2202; 2302; 2420); and an array of antennas (502; 904; 2112; 2204; 2212), wherein the system is characterized in that: the array of antennas (502; 904; 2112; 2204; 2212) is inside the measurement fixture and within a transition zone between a near field boundary and a far field boundary with respect to the DUT (150; 1706; 2202; 2302; 2420), wherein the near field boundary and the far field boundary depend on transmission frequency and size of the DUT antenna array (150; 1706; 2202; 2302; 2420), wherein the array of antennas (502; 904; 2112; 2204; 2212) is configured to test radio frequency, RF, characteristics of a beamformed signal transmitted by the DUT (150; 1706; 2202; 2302; 2420), wherein each respective antenna of the array of antennas (502; 904; 2112; 2204; 2212) is connected to a respective diode detector, wherein each diode detector converts a measurement of field strength to a respective direct current, DC, voltage measurement, wherein the plurality of respective DC voltage measurements comprise a measured pattern of DC voltages measurements, wherein the BATS is configured to compare the measured pattern of DC voltage measurements to a field pattern signature associated with an expected pattern of DC voltage measurements, wherein the comparison is useable for production testing or screening of the DUT (150; 1706; 2202; 2302; 2420). a processing element; a measurement fixture; and an interface, wherein the interface is configured to position a device under test (150; 1706; 2202; 2302; 2420) DUT, inside the measurement fixture, wherein the interface provides power and data connections to the DUT (150; 1706; 2202; 2302; 2420); and an array of antennas (502; 904; 2112; 2204; 2212), wherein the system is characterized in that: the array of antennas (502; 904; 2112; 2204; 2212) is inside the measurement fixture and within a transition zone between a near field boundary and a far field boundary with respect to the DUT (150; 1706; 2202; 2302; 2420), wherein the near field boundary and the far field boundary depend on transmission frequency and size of the DUT antenna array (150; 1706; 2202; 2302; 2420), wherein the array of antennas (502; 904; 2112; 2204; 2212) is configured to test radio frequency, RF, characteristics of a beamformed signal transmitted by the DUT (150; 1706; 2202; 2302; 2420), wherein each respective antenna of the array of antennas (502; 904; 2112; 2204; 2212) is connected to a respective diode detector, wherein each diode detector converts a measurement of field strength to a respective direct current, DC, voltage measurement, wherein the plurality of respective DC voltage measurements comprise a measured pattern of DC voltages measurements, wherein the BATS is configured to compare the measured pattern of DC voltage measurements to a field pattern signature associated with an expected pattern of DC voltage measurements, wherein the comparison is useable for production testing or screening of the DUT (150; 1706; 2202; 2302; 2420).