SAR Measurements for Combined 5G and LTE RF Devices

Abstract

The present invention relates to SAR measurement for combined 5G and LTE RF devices. A method for measuring the specific absorption rate (SAR) of a mobile device under test (DUT) enabled for combined LTE RF and 5G RF transmission is disclosed, the method comprising the following steps: a) providing a mobile device under test (DUT) operable under LTE RF and 5G standards, b) setting the DUT to a mode of transmitting at a maximum power level according to the 5G standard and simultaneously transmitting at a lower power level of the LTE RF standard, c) performing a SAR scan and measuring the 5G signal without considering any contribution from the LTE RF signal, d) setting the DUT to a mode of transmitting at maximum power at maximum power in the LTE RF standard without transmitting according to the 5G standard, e) performing a SAR scan and measuring the LTE RF standard signal, f) combining the results of step c) and step e) to obtain a combined SAR value.

Description

Technical Field

[0001] The present invention generally relates to the field of measuring Specific Absorption Rate (SAR). Background Art

[0002] SAR is a measurement of the rate of absorption of RF (Radio Frequency) energy by the human body from a mobile device (e.g., a cell phone) under test. SAR measurements are performed using protocols defined below, for example:

[0003] - IEC 62209-1Ed.2.0: Human exposure to radio frequency fields from hand-held and body-mounted wireless communication devices – Human body models, apparatus and procedures – Part 1: Procedure for determining the specific absorption rate (SAR) for hand-held devices used against the ear in the frequency range of 300 MHz to 3 GHz;

[0004] - IEC 62209-2Ed.1.0: Human exposure to radio-frequency fields from hand-held and body-mounted wireless communication devices – Human body model, apparatus and procedures – Part 2: Procedure for determining the specific absorption rate (SAR) of wireless communication devices in the frequency range of 30 MHz to 6 GHz when used close to the body; and

[0005] - IEC 62209-2:2010 is for any wireless communication device capable of emitting an electromagnetic field (EMF) intended for use in a manner described by the manufacturer at a distance of up to 200 mm (inclusive) from the human body, i.e. when held in the hand or in front of the face, carried on the body, combined with other transmitting or non-emitting devices or accessories (such as a belt clip, camera or Bluetooth accessory), or embedded in clothing. For transmitters used close to the ear, the procedures of IEC 62209-1:2005 are applicable. IEC 62209-2:2010 is for RF exposure in the frequency range of 30 MHz to 6 GHz and can be used to measure simultaneous exposure from multiple RF sources used close to the human body. Definitions and assessment procedures are provided for the following general categories of device types: body-mounted, body-supported, desktop, face-front, hand-held, laptop, limb-mounted, multi-band, push-to-talk, and clothing-integrated. The types of devices considered include, but are not limited to, mobile phones, wireless microphones, auxiliary broadcasting equipment, and radio transmitters in personal computers. IEC 62209-2:2010 gives guidance on repeatable and conservative measurement methods for determining compliance of wireless devices with SAR limits.

[0006] The initial release of 5G New Radio (NR) is expected to be based primarily on operations in Non-Stand Alone (NSA) mode. 5G NR NSA requires LTE as an anchor to support NR signaling and control, and 5G NR is primarily used for high-speed user data transmission.

[0007] As an interim step for 5G NR deployment, 3GPP specifies a non-standalone configuration using dual connectivity (DC) between the UE and the NR base station (gNB-5G) and the LTE base station (eNB-4G). The EPC core network is connected to the eNB. All control plane functions are handled by LTE, and NR is only used for data in the user plane. 5G is activated only when higher data rates are required.

[0008] It is expected that the initial deployment of NR will be primarily in TDD mode to optimize throughput. Although some deployments may limit the TDD DL:UL transmission ratio to a lower value (e.g., 25% to 30%), 3GPP Rel.15 places no restrictions on the uplink / downlink transmission duty cycle. The transmission duty factor required to perform SAR measurements should be determined based on the operating characteristics and capabilities of the individual products. If the device is capable of supporting 100% duty factor in the uplink, all SAR measurements should be performed at 100% duty factor. In special cases where the DUT hardware does not support 100% duty cycle, testing with the maximum possible duty cycle is required. 3GPP Rel.15 specifies CP-OFDM and DFTS-OFDM as OFDM waveforms supported by 5G NR. In addition to the maximum output power, signal modulation for subcarriers, aggregate channel bandwidth, resource block (RB) configuration, and maximum power reduction (MPR) can also affect the PAPR (Peak to Average Power Ratio) of the NR signal, which will need to be considered to determine the applicable wireless mode required for SAR measurement.

[0009] Until phone booth support is available, 5G product manufacturers will need to provide NR test mode support for SAR measurements. The radio transmission configuration used in the test mode should be equivalent to the radio transmission configuration required by the certification body for conformance testing; for example, channel bandwidth, subcarrier spacing, RB allocation configuration, etc. Whether the DL:UL configuration for TDD is static or dynamic, the highest transmission duty cycle will need to be considered based on the product capabilities to determine the appropriate test configuration. Summary of the invention

[0010] Therefore, the object is to provide an improved method for SAR measurements for combined 5G and LTE RF devices.

[0011] The objects of the invention are achieved by what is presented in the attached independent claim. Advantageous implementations of the invention are further defined in the dependent claims.

[0012] According to a first aspect, the present invention relates to a method for measuring the specific absorption rate (SAR) of a mobile device under test (DUT) enabled for combined LTE RF and 5G RF transmissions, the method comprising the following steps: a) providing a DUT capable of operating under LTE RF and 5G standards, b) setting the DUT in a mode for transmitting at a maximum power level according to the 5G standard and simultaneously transmitting at a lower power level of the LTE RF standard, c) performing a SAR scan and measuring the 5G signal without considering any contribution from the LTE RF signal, d) setting the DUT in a mode for transmitting at maximum power at maximum power in the LTE RF standard without transmitting according to the 5G standard, e) performing a SAR scan and measuring the LTE RF standard signal, f) combining the results of step c) and step e) to obtain a SAR value for the LTE and 5G combination.

[0013] This provides the advantage that a simple method is provided to measure the SAR value.

[0014] In one implementation of the method of the first aspect, the 5G standard is a 5G NRNSA mode with LTE RF as an anchor point.

[0015] This offers the advantage that the measurement of SAR values ​​is performed using well-known standards and patterns.

[0016] In another embodiment of the method of the first aspect, in step b), the DUT is caused to establish a link with a communication transceiver base station in accordance with the 5G standard, wherein all data transmissions are performed in accordance with the 5G standard and all non-data transmissions, such as signaling and synchronization, are performed in accordance with the LTE RF standard.

[0017] In another embodiment of the method of the first aspect, the LTE RF standard transmission in step b) is performed at a minimum power level required to maintain the LTE RF link.

[0018] In another embodiment of the method of the first aspect, the LTE RF standard transmission in step b) is performed at a power level at least 10 dB, preferably at least 20 dB, more preferably at least 30 dB lower than a power level of the LTE RF standard transmission.

[0019] In another embodiment of the method of the first aspect, a diode-based detector probe is used in steps c) and e).

[0020] This provides the advantage that well known detector probes are used to provide SAR values.

[0021] According to a second aspect, the invention relates to a program of instructions storable on a computer-readable medium, said program being used to cause a computer to execute the steps of the method according to the first aspect or any one of its implementation forms. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described below with reference to the accompanying drawings.

[0023] Figure 1 An embodiment of a method for measuring the specific absorption rate (SAR) of a mobile device under test according to the present invention is shown;

[0024] Figure 2 An experimental setup for performing a method for measuring the specific absorption rate (SAR) of a mobile device under test according to an embodiment is shown; and

[0025] Figure 3 An embodiment of a method for measuring the specific absorption rate (SAR) of a mobile device under test according to the present invention is shown. DETAILED DESCRIPTION

[0026] Various aspects of the invention are described herein in the context of a method for measuring the specific absorption rate (SAR) of a mobile device under test.

[0027] The present invention is described more fully below with reference to the accompanying drawings, in which various aspects of the invention are shown. However, the present invention can be implemented in many different forms and should not be construed as being limited to the various aspects of the invention presented by the present disclosure. Rather, these aspects are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The various aspects of the invention shown in the accompanying drawings may not be drawn to scale. On the contrary, the sizes of various features may be enlarged or reduced for clarity. In addition, some drawings may be simplified for clarity. Therefore, the drawings may not show all components of a given device.

[0028] Various aspects of a method for measuring the specific absorption rate (SAR) of a mobile device under test will be presented. However, those skilled in the art will readily appreciate that these aspects can be extended to various aspects of a method for measuring the specific absorption rate (SAR) of a mobile device under test without departing from the present invention.

[0029] Now refer to Figure 1, shows a method 100 for measuring the specific absorption rate (SAR) of a mobile device under test (DUT) according to one embodiment, wherein the mobile device under test (DUT) is enabled for combined LTE RF and 5G RF transmission.

[0030] The method 100 comprises the following steps:

[0031] a) providing (101) a mobile device under test (DUT) operable under LTE RF and 5G standards;

[0032] b) setting (102) the DUT to a mode for transmitting at a maximum power level according to the 5G standard and simultaneously transmitting at a lower power level according to the LTE RF standard;

[0033] c) performing a (103) SAR scan and measuring the 5G signal without considering any contribution from the LTE RF signal;

[0034] d) setting (104) the DUT to a mode for transmitting at maximum power at maximum power in the LTE RF standard and not transmitting according to the 5G standard;

[0035] e) performing (105) a SAR scan and measuring LTE RF standard signals; and

[0036] f) combining (106) the results of step c) and step e) to obtain a combined SAR value.

[0037] In one embodiment, due to the operational flexibility introduced by 5G NR and certain specific requirements described above for NSA, independent exposure testing of LTE and NR is suitable to overcome SAR measurement difficulties and simplify testing considerations. By keeping 4G LTE and 5G NR SAR measurements separate, the independently evaluated SAR can be scaled according to the operating parameters specific to each wireless technology to accommodate the diverse flexibility supported by 5G NR; for example, simultaneous transmission of different technologies (NR, LTE, Wi-Fi, and Bluetooth). When different transmission duty cycles or maximum output powers can be applied to the NR configuration (signal modulation, channel bandwidth, and RB allocation in the frequency band), the SAR results can be scaled according to the output power and transmission duty cycle.

[0038] Figure 2 An experimental setup 200 for performing the method 100 for measuring the specific absorption rate (SAR) of a mobile device under test (DUT) according to an embodiment is shown.

[0039] As mentioned in the background of the invention, wireless devices are typically evaluated for compliance with regulatory exposure limits according to IEC 62209-1 / -2 / -3 standards, IEEE 1528, or IEC / IEEE 63195. At frequencies below 10 GHz, the specific absorption rate (SAR) is the measured quantity. At frequencies above 10 GHz, the relevant metric is the near-field power density (PD).

[0040] The reference compliance measurement system for both quantities usually consists of a 6-axis robot 201 that moves a diode detection probe 201a on a defined grid, measuring the electric field strength of at least two or three components in the near field of the DUT. In the case of SAR, the probe is moved in a human body model 202 that reproduces the dielectric properties in the same range as a human head or body. For PD, the measurements are made in air.

[0041] The diode detection probe 201a cannot distinguish between different energy contributions at different frequencies or from different communication standards. This can be problematic in the case of 5G NR NSA mode where an LTE link and 5G NR transmissions occur in parallel. In practice, the diode detection probe 201a is typically calibrated for each frequency or band at intervals of 100 MHz and for each signal type (e.g., modulation, resource block allocation, etc.). When the probe 201a integrates two signals being transmitted simultaneously, the contributions of the two signals are mixed together, and the lack of phase information makes it difficult to apply the correct probe calibration coefficients.

[0042] In one embodiment, RF probes are used instead of diode detection probes for spectrum analysis.

[0043] Embodiments of the present invention are applicable to diode test probe 201a, which is considered a reference in human exposure measurements due to its very small size and metal content (low RF impact when used near a DUT) and accurate and traceable calibration.

[0044] During near-field exposure measurements, if Figure 2 As shown, the following steps can be performed:

[0045] 1. Place the device DUT near the head or human body model 202 for measurements below 10 GHz (measurements above 10 GHz are performed in air);

[0046] 2. Set the DUT to transmit at maximum power in various test modes, for which SAR (below 10 GHz) or NF power density (above 10 GHz) is measured. The DUT is controlled via a communication transceiver base station (BTS) 203;

[0047] 3. Typically, a 6-axis robot moves the diode detection probe 201a in a human body model 202, which contains a fluid that simulates tissue;

[0048] 4. Assuming that the DUT is transmitting in 5G NR NSA, the 5G NR signal and the LTE link signal are mixed together during transmission;

[0049] 5. The diode detection probe 201a needs to be calibrated for frequencies typically spaced 100 MHz apart and for all types of signal waveforms; and

[0050] 6. When two signals are mixed as in 5G NR NSA, the diode delivers a voltage that is not easily correlated to the electric field because LTE and 5G NR may not be separated after detection, so the correct calibration coefficient cannot be applied.

[0051] In an embodiment of the present invention, it is assumed that the DUT operates in 5G NR NSA mode. The communication BTS 203 controls the DUT to minimize the transmitted LTE RF signal without losing the link. Typically, the LTE FR signal is set to be at least 10dBm lower than the 5G NR DUT RF signal. In this way, the measured SAR is not significantly affected by the LTE signal, so the correct 5G NR diode calibration coefficient can be applied. The impact of LTE can be considered as an uncertainty factor.

[0052] Some steps of a method 100 for determining SAR values ​​in 5G NSA are given below:

[0053] 1) Establish a link between the DUT and the communicating BTS in 5G NR NSA mode, i.e., perform data transmission in 5G and all non-data transmission in LTE;

[0054] 2) Forcing the LTE link to operate at a lower power than 5G NR by the communicating BTS; and

[0055] 3) Perform SAR measurements.

[0056] The LTE link is forced by the communicating BTS to be at least 10dB, 20dB, etc. lower power than 5G NR.

[0057] LTE SAR can be evaluated alone without 5G connectivity, i.e. SA LTE. A combination between LTE SA SAR and 5G NSA LTE SAR (low power in LTE) can also occur, with the worst case exposure corresponding to a strong LTE and strong 5G scenario.

[0058] Figure 3 An embodiment of a method 100 for measuring the specific absorption rate (SAR) of a mobile device under test (DUT) according to the present invention is shown.

[0059] The method 100 further comprises the following steps:

[0060] - Set the DUT to transmit at maximum power in the considered 5G NR NSA mode with a minimum level LTE RF signal (S1);

[0061] - Perform a full SAR scan and measure SAR for the 5G NR NSA signal by applying the corresponding probe coefficients to 5G NR, ignoring the LTE signal (S2);

[0062] - Set the DUT to transmit an LTE RF signal similar to a standalone anchor signal (without 5NR) at the maximum allowed power of the anchor (S3);

[0063] - Performing a complete SAR scan and measuring SAR for the LTE RF signal by applying the corresponding probe coefficients to the LTE RF (S4); and

[0064] - Combining the two SAR measurements by applying one of the standard methods for calculating combined SAR to a plurality of transmissions (S5).

[0065] All features of all embodiments described, shown and / or claimed herein may be combined with each other.

[0066] Although various embodiments of the present invention have been described above, it should be understood that these embodiments are presented only by way of example and not limitation. Various changes can be made to the disclosed embodiments according to the disclosure herein without departing from the spirit of the scope of the present invention. Therefore, the breadth and scope of the present invention should not be limited by any of the embodiments described above. On the contrary, the scope of the present invention should be limited according to the appended claims and their equivalents.

[0067] Although the present invention is shown and described with respect to one or more implementations, equivalent changes and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. In addition, although specific features of the present invention may be disclosed with respect to only one of a plurality of implementations, such features may be combined with one or more other features of other implementations, which may be desirable and advantageous for any given or specific application.

Claims

1. A method (100) for measuring the specific absorption rate of a mobile device under test enabled for combined LTE RF and 5G RF transmissions, the method (100) comprising the following steps: a) providing (101) a mobile device under test capable of operating under LTE RF and 5G standards; b) setting (102) the mobile device under test to a mode in which it transmits at a maximum power level according to the 5G standard and simultaneously transmits at a lower power level according to the LTE RF standard; c) performing (103) a specific absorption rate scan and measuring the 5G signal without taking into account any contribution from the LTE RF signal; d) setting (104) the mobile device under test to a mode in which the mobile device transmits at maximum power at maximum power in the LTE RF standard and not in accordance with the 5G standard; e) performing (105) a specific absorption rate scan and measuring an LTE RF standard signal; f) combining (106) the results of step c) and step e) to obtain a combined specific absorption rate value.

2. The method (100) according to claim 1, in, The 5G standard is the 5G NR NSA mode.

3. The method (100) according to claim 1 or 2, in, In step b), the mobile device under test establishes a link with a communication transceiver base station (203) according to the 5G standard, Among them, all data transmission is performed according to the 5G standard, and all non-data transmission is performed according to the LTE RF standard, and the non-data transmission includes signaling and synchronization.

4. The method (100) according to claim 1 or 2, in, In step b) the transmission of the LTE RF standard is performed at the minimum power level required to maintain the LTE RF link.

5. The method (100) according to claim 1 or 2, in, The transmission of the LTE RF standard is performed in step b) at a power level at least 10 dB lower than a power level of the transmission of the LTE RF standard.

6. The method (100) according to claim 5, in, The transmission of the LTE RF standard is performed in step b) at a power level which is at least 20 dB or at least 30 dB lower than a power level of the transmission of the LTE RF standard.

7. The method (100) according to claim 1 or 2, in, In step c) and step e) a diode based detector probe is used.

8. A computer-readable medium capable of storing an instruction program for causing a computer to execute the steps of the method (100) according to any one of claims 1 to 7.

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