US20120071108A1

US20120071108A1 - Radio Frequency Signal Control Module and Radio Frequency Signal Controlling Method

Info

Publication number: US20120071108A1
Application number: US13/113,296
Authority: US
Inventors: Wen-Wei Yang; Da-Wei Sung
Original assignee: MediaTek Inc
Current assignee: MediaTek Inc
Priority date: 2010-09-20
Filing date: 2011-05-23
Publication date: 2012-03-22
Also published as: US20120069885A1; TW201215202A; JP2012065321A; CN102438300A; US9161321B2

Abstract

A radio frequency (RF) signal control module is provided. The RF signal control module includes a detection and control device detecting at least one radio coupling value in a transmission band according to a radio coupling signal and generating a control signal for controlling transmission power an RF signal to be transmitted according to the detected radio coupling value.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/384,523 filed Sep. 20, 2010 and entitled “OMNI-DIRECTIONAL SAR CALIBRATION”. The entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a radio frequency (RF) signal control module, and more particularly to an RF signal control module that is capable of omni-directional detection of radio coupling values and accordingly controlling the transmission power of a communications device.
2. Description of the Related Art
Specific absorption rate (SAR) is a measure of the rate at which radio frequency (RF) energy is absorbed by a human body when exposed to a radio-frequency electromagnetic field. It is defined as the power absorbed per mass of tissue and has units of Watts per kilogram. SAR is usually averaged either over the whole body, or over a small sample volume (typically 1 g or 10 g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass. It may be calculated from the electric field within the tissue as:
$SAR = \frac{σ {\langle E \rangle}^{2}}{2 ρ},$
where σ represents the sample electrical conductivity, |E| represents the magnitude of the electric field and ρ represents the sample density.
Conventionally, a proximity sensor is embedded in an electronic device for SAR calibration. Once the proximity sensor has detected that a human body is close to the electronic device, a maximum RF transmission power is limited. However, the proximity sensor is a directional device. The more directions that are required to be detected for calibration, the more proximity sensors required to be provided.
Therefore, a novel design for transmission power detection and control without directional limitations is highly required.

BRIEF SUMMARY OF THE INVENTION

A radio frequency (RF) signal control module and RF signal controlling method are provided. An embodiment of an RF signal control module comprises a detection and control device. The detection and control device detects at least one radio coupling value in a transmission band according to a radio coupling signal and generates a control signal for controlling transmission power of an RF signal to be transmitted according to the detected radio coupling value.
An embodiment of an RF signal controlling method comprises: detecting an amount of change of a radio coupling value according to a radio coupling signal; determining whether the amount of radio coupling value change has exceeded a predetermined threshold; and limiting a maximum transmission power of an RF signal to be transmitted or lowering a transmission power of an RF signal to be transmitted by a level according to the detected radio coupling value when the amount of radio coupling value change has exceeded the predetermined threshold.
A detailed description is given in the following embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 shows a schematic block diagram of a communications apparatus according to an embodiment of the invention;

FIG. 2 shows a schematic block diagram of the RF signal control module according to an embodiment of the invention;

FIG. 3 shows a schematic block diagram of a communications apparatus according to an embodiment of the invention;

FIG. 4 shows a schematic block diagram of a communications apparatus according to another embodiment of the invention;

FIG. 5 shows a schematic diagram of a coupler 528 according to an embodiment of the invention;

FIG. 6 shows a schematic block diagram of the detection and control device according to an embodiment of the invention;

FIG. 7 shows a schematic block diagram of a communications apparatus equipped with multiple transmission antennas according to another embodiment of the invention;

FIG. 8 shows a schematic block diagram of a communications apparatus equipped with multiple transmission antennas according to another embodiment of the invention; and

FIG. 9 shows a flow chart of an RF signal controlling method according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
FIG. 1 shows a schematic block diagram of a communications apparatus according to an embodiment of the invention. The communications apparatus 100 may at least comprise a transceiver module 102 and a radio frequency (RF) signal control module 104. The transceiver module 102 is arranged to generate an RF signal S_RFto be transmitted to the air interface. The RF signal control module 104 is arranged to generate a control signal S_Ctrlto adjust transmission power utilized by the transceiver module 102 for transmitting the RF signal S_RF. It should be noted that for clear illustration of the invention concept, only the devices related to the proposed design are illustrated in FIG. 1, and therefore, the invention should not be limited thereto.
According to an embodiment of the invention, the RF signal control module 104 obtains or receives a radio coupling signal S_Coupleand generates the control signal S_Ctrlaccording to the radio coupling signal S_Couple. In the embodiments of the invention, the radio coupling signal S_Coupleis corresponding to transmission of the RF signal S_RF.
FIG. 2 shows a schematic block diagram of the RF signal control module according to an embodiment of the invention. The RF signal control module 104 may comprise a radio coupling device 202 and a detection and control device 204. The radio coupling device 202 is arranged to obtain or receive the radio coupling signal S_Couplein a transmission band through a radio coupling path established between a transmission antenna transmitting the RF signal S_RFand the RF signal control module 104 (which will be discussed in more detail in the following paragraphs). The detection and control device 204 is arranged to detect at least one radio coupling value according to the radio coupling signal S_Couple, and generates the control signal S_Ctrlfor controlling transmission power of the RF signal S_RFto be transmitted later according to the detected radio coupling value.
According to an embodiment of the invention, the radio coupling device 202 may be implemented by a sensor antenna for receiving the radio coupling signal S_Couple. In the embodiment, the radio coupling signal S_Couplemay be a faded version of the RF signal S_RF. FIG. 3 shows a schematic block diagram of a communications apparatus 300 according to an embodiment of the invention. As shown in FIG. 3, the transceiver module 302 is coupled to a transmission antenna 324 for transmitting the RF signal S_RFgenerated thereby. Note that in some embodiments, the transmission antenna 324 may also be integrated in the transceiver module 302 and the invention should not be limited thereto. The RF signal control module 104 may comprise the detection and control device 304 and a sensor antenna 326. The transmitted RF signal S_RFmay be received by the sensor antenna 326 from the radio coupling path 330 between the transmission antenna 324 and the sensor antenna 326. Because the radio coupling is omni-directional and fixed from the transmission antenna 324 to the sensor antenna 326, according to an embodiment of the invention, the detection and control device 304 may detect and monitor the power or phase of the radio coupling signal S_Couple, or any other radio coupling value according to the radio coupling signal S_Couple, and determine whether a currently detected radio coupling value has exceeded a predetermined threshold determined when there is no human body close to the communications apparatus 300. When the radio coupling value is determined to have exceeded the predetermined threshold, the detection and control device 304 may determine that there is at least one human body close to the communications apparatus 300, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 302 or lowering the transmission power of the RF signal S_RFto be transmitted later by a certain level. Therefore, the possible RF energy absorbed by the human body when exposed to radio frequency electromagnetic field is reduced. Note that in some embodiments of the invention, the predetermined threshold may also be set as an amount of possible change of the radio coupling value determined when there is no human body close to the communications apparatus 300. The detection and control device 304 may detect and monitor the amount of change of the radio coupling value. When the amount of radio coupling value change has exceeded the predetermined threshold, the detection and control device 304 may determine that there is at least one human body close to the communications apparatus 300, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 302 or lowering the transmission power of the RF signal S_RFto be transmitted later by a certain level. Note also that in other embodiments, the predetermined threshold may also be set as a percentage or an absolute value of predetermined radio coupling value or an amount of possible change of the radio coupling value determined when there is no human body close to the communications apparatus, or may be set as other values based on the similar concepts, and the invention should not be limited to the examples as described above.
According to an embodiment of the invention, an ideal radio coupling value or the ideal amount of possible change of the radio coupling value when there is no human body close to the communications apparatus is first determined. For example, suppose that when there is no human body close to the communications apparatus 300, the power of the transmitted RF signal S_RFis 23 dBm and the power of the received radio coupling signal S_Coupleis −7 dBm, and therefore, the ideal radio coupling path loss is obtained by (−7−23)=30 dBm. A 10% margin may be applied, so that the predetermined threshold of the radio coupling path loss may be determined as 33 dBm. In other words, once a currently obtained radio coupling path loss determined by the detection and control device 304 has exceeded 33 dBm, the detection and control device 304 may determine that there is at least one human body close to the communications apparatus 300, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 302.
For another example, an ideal phase of the received radio coupling signal S_Couplemay first be measured when there is no human body close to the communications apparatus 300. The phase component may be obtained from the imaginary part of the received radio coupling signal S_Couple. A suitable margin may also be applied, so as to determine one or more predetermined thresholds corresponding to the phase of the received radio coupling signal S_Couple. Once a currently obtained phase of the received radio coupling signal S_Coupleis determined to be different from the predetermined threshold(s), the detection and control device 304 may determine that there is at least one human body close to the communications apparatus 300, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 302 or lowering the transmission power of the RF signal S_RFto be transmitted later by a certain level.
According to another embodiment of the invention, the radio coupling device 202 may be implemented by a coupler for obtaining the radio coupling signal S_Couple. In the embodiment, the radio coupling signal S_Couplemay be a reflected (or returned) version of the RF signal S_RF. FIG. 4 shows a schematic block diagram of a communications apparatus 400 according to another embodiment of the invention. As shown in FIG. 4, a coupler 428 is coupled between a transmission antenna 424 for transmitting the RF signal S_RFand a power amplifier 422. The power amplifier 422 is comprised in the transceiver module 402. Note that in some embodiments, the transmission antenna 424 may also be integrated in the transceiver module 402 and the invention should not be limited thereto. Note also that in some embodiments, the coupler may be integrated in the power amplifier 422, or embedded on the printed circuit board, and the invention should not be limited thereto. FIG. 5 shows a schematic diagram of a coupler 528 according to an embodiment of the invention. The coupler 528 may comprise an input port 501 for receiving the RF signal S_RFfrom the power amplifier 422, a transmitted port 502 for outputting the RF signal S_RFand receiving the reflected (or returned) RF signal S′_RF, a coupled port 503 for coupling the reflected (or returned) RF signal S′_RFto generate the radio coupling signal S_Coupleand an isolated port 504. Referring back to FIG. 4, according to an embodiment of the invention, the detection and control device 404 may detect and monitor the power or phase of the radio coupling signal S_Couple, or any other radio coupling value (such as an impedance of the transmission antenna 424) according to the radio coupling signal S_Couple, and determine whether the radio coupling value or the amount of radio coupling value change has exceeded a predetermined threshold determined when there is no human body close to the communications apparatus 400. When the radio coupling value or the amount of radio coupling value change is determined to have exceeded the predetermined threshold, the detection and control device 404 may determine that there is at least one human body close to the communications apparatus 400, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 402 or lowering the transmission power of the RF signal S_RFto be transmitted later by a certain level. Therefore, the possible RF energy absorbed by the human body when exposed to radio frequency electromagnetic field is reduced.
For example, an ideal impedance of the transmission antenna 424 may first be measured when there is no human body close to the communications apparatus 400. The impedance of the transmission antenna 424 may be obtained by measuring an S parameter corresponding to the transmission antenna 424. For example, when the coupler 428 is a multi-port device with port 1 P1 and port 2 P2, the measured input return loss S₁₁may be representable of the impedance of the transmission antenna 424. To be more specific, the detection and control device 404 may obtain an ideal input return loss S₁₁according to a ratio of the radio coupling signal S_Coupleto the RF signal S_RFwhen there is no human body close to the communications apparatus 400. Suppose that the obtained ideal input return loss S₁₁is expressed by S₁₁=a+bj, where the a and b are real numbers, and j is a mathematical symbol which is called the imaginary unit. The detection and control device 404 may take the imaginary part number b as the radio coupling value to represent the impedance of the transmission antenna 424. Similarly, a suitable margin may also be applied, so as to determine the predetermined threshold corresponding to the impedance of the transmission antenna 424. Once a currently obtained input return loss S_ii(or currently obtained impedance of the transmission antenna 424) is determined to have exceeded the predetermined threshold, the detection and control device 404 may determine that there is at least one human body close to the communications apparatus 400, and generate the control signal S_Ctrlfor limiting the maximum transmission power of the transceiver module 402 or lowering the transmission power of the RF signal S_RFto be transmitted later by a certain level.
Note that in other embodiments of the invention, the other information obtained from the measured input return loss S₁₁may also be taken as the radio coupling value. For example, the real part number a, or a combination of the real part and imaginary part numbers a and b, such as √{square root over (a²+b²)}, may also be taken as the radio coupling value. Besides the input return loss S₁₁, the insertion loss S₂₁may also be obtained as the radio coupling value and the invention should not be limited thereto. For example, when the insertion loss S₂₁is expressed by S₂₁=c+dj, where the c and d are real numbers, the real part number c, the imaginary part number d, or a combination of the real part and imaginary part numbers c and d, such as √{square root over (c²+d²)}, may also be taken as the radio coupling value.
FIG. 6 shows a schematic block diagram of the detection and control device according to an embodiment of the invention. The detection and control device 604 may comprise a detector 641, a sampler 642, a comparator 643 and a memory 644. According to an embodiment of the invention, the detector 641 may receive the radio coupling signal S_Couplefrom the radio coupling device, and detect the radio coupling value and/or the amount of radio coupling value change according to the radio coupling signal S_Couple. For example, the detector 641 may detect the power and/or power change of the radio coupling signal S_Coupleby performing waveform to voltage conversion. For another example, the detector 641 may detect the phase and/or phase change of the radio coupling signal S_Coupleby extracting the imaginary part of the radio coupling signal S_Couple. For yet another example, the detector 641 may detect the impedance and/or impedance change of the transmission antenna by measuring the S parameter in the transceiver network. The value S_Vdetected by the detector 641 may further be sampled by the sampler 642. The sampler 642 may be, for example, an analog to digital converter. The sampled value S_V′ may be further passed to the comparator 643. The comparator 643 may compare the sampled value S_V′ with a predetermined threshold value TH stored in the memory 644, and generate the control signal S_Ctrlaccording to the comparison result. Note that FIG. 6 only shows one exemplary design of the detection and control device, and the invention should not be limited thereto. In addition, in the embodiments of the invention, the detection and control device may be implemented by dedicated hardware, or the functions performed by the detection and control device as described above may be coded as some software instructions executed by a general purpose processor. Therefore, the invention should not be limited to either cases.
FIG. 7 shows a schematic block diagram of a communications apparatus equipped with multiple transmission antennas according to another embodiment of the invention. The communications apparatus 700 may at least comprise two transmission antennas 724 and 726 for simultaneously transmitting the RF signal (the MIMO case) or not simultaneously transmitting the RF signal (the antenna selection case). In the embodiment, two radio coupling devices 706 and 708 are utilized and disposed close to the transmission antennas 724 and 726 for detecting the radio coupling signals, respectively. For example, for the MIMO case, both of the transmission antennas 724 and 726 are utilized for transmitting the RF signals. The radio coupling devices 706 and 708 disposed close to the transmission antennas 724 and 726 may respectively detect the radio coupling signals reflected to the transmission antennas 724 and the transmission antennas 726, or detect the radio coupling signal coupled from the transmission antennas 726 (or 724) to the transmission antennas 724 (or 726). For another example, for the antenna selection case, when the transmission antennas 724 is utilized for transmitting the RF signal and the transmission antennas 726 is not utilized for transmitting the RF signal, the radio coupling device 708 corresponding to the transmission antennas 726 may be utilized to detect the radio coupling signal coupled from the transmission antennas 724 to the transmission antennas 726, and vise versa. The received coupling signals are further transmitted to the detection and control device 704 for transmission power control. It should be noted that FIG. 7 is a simplified block diagram with a lot of devices configured inside of the commutations device omitted for clear illustration of the invention concept. Therefore, the invention should not be limited thereto. It should also be noted that when there are more than one transmission antenna utilized for transmitting the RF signals (for example, the MIMO case), the radio coupling value(s) may be obtained according to one radio coupling signal corresponding to either one transmission antenna, or according to the radio coupling signals obtained corresponding to the multiple transmission antennas, or according to a combination result of the radio coupling signals corresponding to multiple transmission antennas, or others. The way to determine the predetermined threshold may also be varied based on the mechanism of obtaining the radio coupling value.
FIG. 8 shows a schematic block diagram of a communications apparatus equipped with multiple transmission antennas according to another embodiment of the invention. The communications apparatus 800 may at least comprise two transmission antennas 824 and 826 for simultaneously transmitting the RF signal (the MIMO case) or not simultaneously transmitting the RF signal (the antenna selection case). In the embodiment, one radio coupling device 806 is utilized and disposed close to (or between) the transmission antennas 824 and 826 for detecting the radio coupling signal. For example, for the MIMO case, both of the transmission antennas 824 and 826 are utilized for transmitting the RF signals. The radio coupling device 806 may detect the radio coupling signals reflected to the transmission antennas 824 and the transmission antennas 826, or detect the radio coupling signal coupled from the transmission antennas 826 (or 824) to the transmission antennas 824 (or 826). For another example, for the antenna selection case, when the transmission antennas 824 is utilized for transmitting the RF signal and the transmission antennas 826 is not utilized for transmitting the RF signal, the radio coupling device 806 may be utilized to detect the radio coupling signal coupled from the transmission antennas 824 to the transmission antennas 826, and vise versa. The received coupling signals are further transmitted to the detection and control device 804 for transmission power control. It should be noted that FIG. 8 is a simplified block diagram with a lot of devices configured inside of the commutations device omitted for clear illustration of the invention concept. Therefore, the invention should not be limited thereto. It should also be noted that in some embodiments of the invention, for the antenna selection case as previously described, the transmission antenna that is not utilized for transmitting the RF signal may also function as the radio coupling device for receiving or obtaining the radio coupling signal S_Couple. In this case, a dedicated radio coupling device (such as the radio coupling device 706, 708 or 806 as shown in FIG. 7 and FIG. 8) can be omitted.
FIG. 9 shows a flow chart of an RF signal controlling method according to an embodiment of the invention. To begin, an amount of change of a radio coupling value corresponding to a communications apparatus may be detected according to a radio coupling signal (Step S902). Next, it is determined whether the amount of radio coupling value change has exceeded a predetermined threshold (Step S904). When the amount of radio coupling value change has not exceeded a predetermined threshold, it is determined that there is no human body close to the corresponding communications apparatus and the process may be ended. Otherwise, a maximum transmission power of the communications apparatus for transmitting an RF signal may be limited or a transmission power of the RF signal S_RFto be transmitted later may be lowered by a certain level according to the amount of radio coupling value change (Step S906). Note that when it is determined that there is any human body close to the corresponding communications apparatus, the maximum transmission power is limited to a smaller possible value as defined by the corresponding specifications so as to reduce possible RF energy absorbed by the human body. In other embodiments, the transmission power of the communications apparatus for transmitting an RF signal may also be directly reduced according to the detected radio coupling value, and the invention should not be limited thereto. The flow as shown in FIG. 9 may be repeated periodically, so as to dynamically control the transmission power of the communications apparatus.
The above-described embodiments of the present invention can be implemented in any of numerous ways. For example, the embodiments may be implemented using hardware, software or a combination thereof. It should be appreciated that any component or collection of components that perform the functions described above can be generically considered as one or more processors that control the above discussed function. The one or more processors can be implemented in numerous ways, such as with dedicated hardware, or with general purpose hardware that is programmed using microcodes or software to perform the functions recited above.
While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the present invention shall be defined and protected by the following claims and their equivalents.

Claims

What is claimed is:

1. A radio frequency (RF) signal control module, comprising:

a detection and control device, detecting at least one radio coupling value in a transmission band according to a radio coupling signal and generating a control signal for controlling transmission power of an RF signal to be transmitted according to the detected radio coupling value.

2. The RF signal control module as claimed in claim 1, further comprising:

a radio coupling device, obtaining the radio coupling signal from a radio coupling path between a transmission antenna utilized for transmitting the RF signal and the radio coupling device.

3. The RF signal control module as claimed in claim 2, wherein the radio coupling device is an antenna.

4. The RF signal control module as claimed in claim 2, wherein the radio coupling device is a coupler.

5. The RF signal control module as claimed in claim 1, wherein the radio coupling value is power of the radio coupling signal.

6. The RF signal control module as claimed in claim 1, wherein the radio coupling value is a phase of the radio coupling signal.

7. The RF signal control module as claimed in claim 1, wherein the radio coupling value is an impedance of a transmission antenna utilized for transmitting the RF signal.

8. The RF signal control module as claimed in claim 1, wherein the radio coupling signal is a faded version of the RF signal.

9. The RF signal control module as claimed in claim 1, wherein the radio coupling signal is a reflected version of the RF signal.

10. The RF signal control module as claimed in claim 1, wherein the radio coupling value is detected by measuring an S parameter corresponding to a transmission antenna utilized for transmitting the RF signal.

11. The RF signal control module as claimed in claim 1, wherein the detection and control device further comprises:

a memory, storing a predetermined threshold value;

a detector, detecting the radio coupling value according to the radio coupling signal;

a sampler, sampling the detected radio coupling value to obtain a sampled radio coupling value; and

a comparator, comparing the sampled radio coupling value with the predetermined threshold value and generating the control signal according to a comparison result.

12. A radio frequency (RF) signal controlling method, comprising:

detecting an amount of change of a radio coupling value according to a radio coupling signal;

determining whether the amount of radio coupling value change has exceeded a predetermined threshold; and

limiting a maximum transmission power of an RF signal to be transmitted or lowering a transmission power of an RF signal to be transmitted by a level when the amount of radio coupling value change has exceeded the predetermined threshold.

13. The method as claimed in claim 12, further comprising:

obtaining the radio coupling signal from a radio coupling path coupled to a transmission antenna utilized for transmitting an RF signal.

14. The method as claimed in claim 12, wherein the radio coupling signal is a faded version of the RF signal.

15. The method as claimed in claim 12, wherein the radio coupling signal is a reflected version of the RF signal.

16. The method as claimed in claim 12, wherein the radio coupling value is power of the radio coupling signal.

17. The method as claimed in claim 12, wherein the radio coupling value is a phase of the radio coupling signal.

18. The method as claimed in claim 12, wherein the radio coupling value is an impedance of a transmission antenna utilized for transmitting the RF signal.

19. The method as claimed in claim 12, wherein the detecting step further comprising:

measuring an S parameter corresponding to a transmission antenna utilized for transmitting an RF signal.