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Science and technology are changing day by day, major technology companies are gradually paying attention to the millimeter wave technology of wireless communication, such as IC design manufacturers, antenna chip manufacturers, antenna wafer packaging plants, 77GHz vehicle radar operators, etc., have invested considerable efforts in this In order to make our products comply with the current new specifications 3GPP TR38.810 / 802.11ad / 802.11ay and fifth-generation mobile communications, etc., constantly try various measurement methods. There are two very important factors in the millimeter wave test method, one is "composite beamforming" and the other is "composite beam scanning", both of which affect the phase array of the object under test. The general millimeter wave test is performed by the omnidirectional radiation sensitivity of the horn antenna. However, using this type of test method will cause the object to be measured to be offset by 96 degrees at 1 mm during the composite beamforming. This is a very large error, which is The problems that have been troubled by various factories.
In order to assist manufacturers to improve the error in testing, Shuoxun Technology constantly tried to develop, and finally developed a test method for the object to be tested, named "TRC Flying CATR", after environmental erection and verification. After that, the previous large dish was reduced to a 6 inch, 9 inch, 15 inch small dish, combined with the feed antenna and the robot arm. In practice, the integrated beamforming can directly correspond to the phase center of the object to be tested, not only the air interface. A lot of interference factors have also helped manufacturers to save a lot of space for actual testing. In addition, the small dish CATR can also be installed in the isolation box to design a isolation box type millimeter wave system for the 77GHz vehicle radar manufacturer. It is named "TRC radar production line isolation box, Radar Box", which also utilizes The measurement of CATR and feeder antennas can help production line personnel to detect products conveniently, quickly and accurately, so that the products can be mass-produced quickly, and the new millimeter-wave CATR is currently the only one in Taiwan.
The millimeter wave (Millimeter Wave) is a radio transmission in the frequency band of 30 GHz to 300 GHz (wavelength 10 mm to 1 mm). In this band, the spectrum is obtained in comparison with the conventional high frequency (Very High Frequency, VHF) and UHF (Utlra High). Frequency, UHF) The frequency bands used for broadcast, television, and mobile communications are relatively easy, and many frequency bands are reserved and unused. Therefore, each wirelessly transmitted channel in the millimeter wave band can have a larger bandwidth (Band Width) to support higher speed data transmission.
In the millimeter wave band, Free Space Loss (FSL) and penetration barriers are larger than those currently used below 6 GHz, which improves mutual interference between users, while the wavelength of millimeter waves is currently used. The wavelength of radio products below 6 GHz is between one-twentieth and one-thirtieth, which makes the complex Phase Array Antenna integrated into the wafer (Antenna On Chip, AOC) and chip package (Antenna In Packaging, AIP) Integrate the wafer and antenna on the product's circuit board. The phase array antenna and the beam forming (Beam Forming) and beam scanning (Beam Steering) provide the antenna gain and directivity of the millimeter wave wireless product to less than 6 GHz. Increased radio products by at least 10dB, which not only improves signal quality, but also reduces mutual interference between High Channel or Adjacent Channel, plus the physical characteristics of the aforementioned millimeter wave, making the channel reusable , increase the capacity of the communication network.
At the beginning of this year, 3GPP announced the provisional standards for 5th generation mobile networks (5G). The second frequency range (Frequency Range, FR2) is 24.25GHz to 52.6GHz. By the way, the mainland 5G The millimeter wave band is 24.25 to 29.5 GHz and 37 to 43.5 GHz. Meanwhile, at the beginning of this year, the IEEE also passed the 802.11ay version 1.1 standard in the frequency band of 57 GHz to 64 GHz, and the transmission distance was increased from the original 10 meters to 100 meters. The throughput (Throughput) has increased to at least 20 Gbps, and many new chips are expected to appear on the market in the second half of next year.
The United Kingdom and the European Union set a sunset date for the 24 GHz Ultra Wide Band (UWB) vehicle radar in 2021, where the 21.65 GHz to 26.65 GHz is just in conflict with the band specified by the Fifth Generation Mobile Communications. Also added 76 GHz to 77 GHz Long Range Radar (LRR) and 77 GHz to 81 GHz Short Range Radar (SRR), plus the booming of electric and self-driving drones, the market The demand for anti-collision sensors is increasing, and more manufacturers are investing in the development of automotive radar.
In common with the above-mentioned millimeter wave wireless products, the common feature between them is to use phase array antennas, and the phase center of each group of antennas will follow its position in the phase array antenna, and the surrounding conditions (screws, plastic covers) , display, battery, isolation cover, and product housing paint, etc.) Regardless of the form of the antenna, these variables around the antenna environment. It has a great impact on the performance of Beam Forming and Bean steering, and some even cause the software control phase shifter (Phase Shifter) to not make the Bean steering reach the specified direction.
To illustrate the effects of the surrounding conditions of these phase arrays on design and production variation, 3GPP R4-1800889 simulates the impact of a 5G mobile phone's plastic cover and display on a 4x1 linear block array antenna. It can be known that the display and the plastic cover increase the antenna gain (Antenna Gain) by 2 dB. This assumes that the display has a dielectric constant of 7.25 to 29.5 GHz. What is the deviation of the real display in this band? And how to measure Antenna Gain for 5G phones? These will be the problems that manufacturers face when they are producing.
5G 802.11zd and radar and other millimeter wave products air interface measurement according to the current various standards require far field measurement, when using standard gain horn antenna (Standard Gain Horn, SHG) as the measurement antenna, then measure the antenna and The distance between millimeter wave products must be greater than 2D2/in. (The origin of this formula is to use an omnidirectional point source antenna as the measurement antenna to calculate the test distance required for the far field. The high directional horn antenna must follow its direction. Sexually increasing the distance), using this formula to rate the 7cm (longest side) size of the radar module (operating at 80GHz) requires a measuring distance of 5 meters.
In order to meet the measurement requirements of far-field distances of various millimeter-wave (ACC, AIP, chip and antenna integrated on the circuit board), ShuoXun offers small sizes (6 inches, 9 inches and 12 inches). The Compact Antenna Testing Rage (CATR) replaces the horn antenna (Corrugated Horn). The CATR is a Rolled Edge Reflector that is uniformly emitted by a wrinkled wave, and reflects a plane wave in accordance with the far field at a distance of several tens of centimeters from the reflector (depending on the size of the reflector).
Compact Antenna Testing Range，CATR
Comparing the two different measurement devices of CATR and SGH (Standard Gain Horn) have different characteristics as shown in Table 1, and analyze these differences in the table to the AOC, AIC or wafer and antenna integrated in the circuit board mm The impact of the development and manufacturing of wave products is as follows:
Table 1, Differences between CATR and SGH
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Measurement
Antenna
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SGH
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CATR
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Gain(dB)
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20dB
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40dB
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Angular Recognition
dB(X°)
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1dB(10°)
20dB(60°)
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1dB (2.7°) 20dB (4°)
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10cm DUT FF Range
(Meter)/FSL(dB)
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10 meter/90 dB
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0.3 meter /60 dB
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One of five Element of Phase Array antenna
failure Identification (dB)
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Large Deviation 0.4dB ~ 3dB.
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1.8dB ~2.1 dB less than Normal Power.
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Phase Ripple ( Y°)
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22.5°
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10°
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The Angular Recognition parameter shown in Table 1 is very important for the Bean steering of millimeter-wave phase-array antennas, especially the Long-Rang Radar (LRR) pointing angle and beam width. It takes 1 degree of accuracy. It can be seen from the table that comparing the far field pattern of CATR and SGH, the SGH 1dB Beam width is 10 degrees, the CATR is 2.7 degrees, and the angle SGH falling below the peak gain of 20 dB is 60 degrees, then the CATR is only 4 degrees. That is to say, when the Beam Steering is skewed, the recognition rate provided by SGH is poor. This is especially important for the testing of GO & NO GO on the production line.
In addition, the millimeter wave products that combine the wafer and the array antenna on the circuit board, when the production is assembled, the wafers emit multi-power amplifiers or receive low-frequency amplifiers, and when their pins are connected to the array antenna unit, there may be poor soldering. Or the array antenna unit itself has a problem. In the rightmost column of Table 1, there is the failure identification of any of the five groups of array antenna units. The difference in amplitude of the amplitude detected by SGH is 0.4dB to 3dB, and will follow the array antenna. The directivity of the unit and its location change. On the other hand, if the CATR measurement is used, when any group of antennas is bad and the pointing is not at the predicted angle and the deviation is greater than 4 degrees, the signal received by the CATR will be 20 dB smaller than normal; when the antenna unit is defective, it will be generated. When the deviation angle is extremely small, the CATR will receive 1.8 to 2.1 dB less than the normal signal.
5G user terminal equipment (such as mobile phones, tablet micro-bases, etc.) when transmitting noise in addition to the main wave to be measured 87 GHz, also requires long-distance shielding far-field test space, but can use CATR to carry out 5G in short distance Far field measurement, not only that, CATR antenna gain is high and measurement uncertainty is low. According to Table 1 antenna gain and FSL under the same conditions, CATR has 28dB more signal-to-noise ratio than SGH, spectrum analysis The noise level of the instrument in Resolution Bandwidth (RBW) RBW=1MHz is substituted into the receiving system. The system noise level of SGH has been restricted by regulations, but there is still 28dB of space if using CATR.
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