Automatic gain adjusting device and method for zero intermediate frequency receiver and magnetic resonance imaging system
By introducing an automatic gain adjustment device in the zero intermediate frequency receiver, the gain of the receiver is adjusted in real time by using the combination of a control module and a fixed gain amplifier, the problem of insufficient dynamic range of the receiver in wireless coil applications in the MRI system is solved, and gain control with low cost and high reliability is achieved.
Patent Information
- Application Number
- CN202311635519.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-30
- Publication Date
- 2025-05-30
AI Technical Summary
In the wireless coil application of existing zero-intermediate frequency receivers in MRI systems, the antenna position is fixed and the antenna position at the transmitter end moves with the scanning position, resulting in a change in the signal intensity range and a high dynamic range is required. However, the existing improvement solutions are costly, complex gain adjustment and limited application range.
An automatic gain adjustment device is adopted, which includes a control module and a fixed gain amplifier. The input power of the ADC is detected in real time through the control module, and the gain of the adjustable attenuator in the zero-intermediate frequency receiver is adjusted so that the input power of the ADC always tends toward the target input power by enabling or not enabling the enable port of the fixed gain amplifier.
It reduces the cost of improving the dynamic range of the zero-intermediate frequency receiver, simplifies the gain adjustment process, improves the reliability and adaptability of the system, and is suitable for scenarios with different gain control needs.
Smart Images
Figure CN120074558A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of wireless coils, in particular to an automatic gain adjustment device, method and MRI (Magnetic Resonance Imaging) system for a zero intermediate frequency receiver. Background Art
[0002] In an MRI system, compared with traditional coils, wireless coils are expected to become a new application trend in magnetic resonance imaging due to their advantages such as no need to connect to the hospital bed, good user experience, and easy cleaning. Figure 1 FIG. 1 is a schematic diagram of a wireless coil for MR signal transmission and reception in an existing MRI system. Among them, the wireless coil 11 at the transmitting end transmits the collected real-time MR signal to the low-noise amplifier 12 for noise reduction and amplification processing, and then transmits it to the ADC (Analog to Digital Converter) 13 for analog-to-digital conversion. After that, it is transmitted to the FPGA (Field Programmable Gate Array) 14 for encoding, and then transmitted to the modulator 15 to be modulated into a high-frequency signal and transmitted through the antenna. The high-frequency signal is received by the antenna at the receiving end and enters the zero intermediate frequency receiver 16 for zero intermediate frequency processing, and then transmitted to the digital signal processing module 17 for decoding. The decoded signal is transmitted to the image reconstruction system 18 through an optical fiber. In the whole link, the receiver selects a zero intermediate frequency receiver, which has high integration, short R & D cycle and low cost.
[0003] Figure 2 FIG. 2 is a schematic structural diagram of an existing zero intermediate frequency receiver 16, which mainly includes: a variable attenuator 21, a low-noise amplifier 22, an oscillator 23, a demodulator 24, a filter 25 and an ADC 26, etc. Among them, the high-frequency signal received by the antenna at the receiving end is first attenuated by the variable attenuator 21, then noise-reduced and amplified by the low-noise amplifier 22, and then down-converted with the local oscillator signal generated by the oscillator 23 to form a zero intermediate frequency signal. After that, the noise in the zero intermediate frequency signal is filtered by the filter 24, and then the zero intermediate frequency signal is digitized by the ADC 26, and then the digital signal is sent to the subsequent module for further processing. The variable attenuator 21 inside a typical zero intermediate frequency receiver can achieve a gain control with a dynamic range of 30 dB (decibels). However, in the application of wireless coils in an MRI system, the position of the antenna of the zero intermediate frequency receiver is fixed, while the position of the antenna at the transmitting end moves with different scanning parts. Therefore, the signal intensity at the receiving end varies within a large range, posing a high dynamic range requirement for the receiver.
[0004] There are mainly the following three existing solutions to improve the dynamic range of the zero intermediate frequency receiver:
[0005] 1. RF gain adjustable scheme. An additional digitally controlled attenuator or an analog adjustable attenuator implemented with PIN diodes is added to the front end of the zero-IF receiver. Figure 3 As shown in the schematic diagram of an existing RF gain adjustable scheme, as Figure 3 shown, a low-noise amplifier 31, an adjustable attenuator 32, and a filter 33 are added to the front end of the zero-IF receiver 16.
[0006] 2. Baseband gain adjustable scheme. When permitted by the baseband interface of the zero-IF receiver 16, a new baseband adjustable amplifier is added. Figure 4 As shown in the schematic diagram of an existing baseband gain adjustable scheme, as Figure 4 shown, a filter 41, an adjustable baseband amplifier 42, and an ADC 43 are added to the back end of the zero-IF receiver 16.
[0007] 3. Simultaneously adopt the RF gain adjustable scheme and the baseband gain adjustable scheme.
[0008] The disadvantages of the above three schemes are as follows: Since the prices of the adjustable attenuator and the baseband adjustable amplifier are relatively high, the cost is high; moreover, the gains of the adjustable attenuator and the baseband adjustable amplifier need to be adjusted in real time or periodically, and the implementation is complex; furthermore, since the adjustable ranges of the adjustable attenuator and the baseband adjustable amplifier are limited, they can only adapt to scenarios with certain gain control requirements. SUMMARY OF THE INVENTION
[0009] In view of this, on the one hand, an embodiment of the present invention proposes an automatic gain adjustment device for a zero-IF receiver to reduce the cost required to improve the dynamic range of the zero-IF receiver; on the other hand, an MRI system is proposed to reduce the cost required to improve the dynamic range of the zero-IF receiver.
[0010] An automatic gain adjustment device for a zero-IF receiver, the device includes: a control module and at least one fixed-gain amplifier, wherein the fixed-gain amplifier has an enable port;
[0011] The control module is connected to the enable port of the at least one fixed-gain amplifier;
[0012] The control module is connected to the adjustable attenuator in the zero-IF receiver;
[0013] The control module is connected to the analog-to-digital converter ADC in the zero-IF receiver;
[0014] The signal input end of the at least one fixed-gain amplifier is connected to the receiving antenna of the zero-IF receiver;
[0015] The signal output end of the at least one fixed-gain amplifier is connected to the signal input end of the adjustable attenuator in the zero-IF receiver.
[0016] When there are multiple fixed-gain amplifiers, the fixed-gain amplifiers are cascaded.
[0017] The signal input terminal of the first-stage fixed-gain amplifier is connected to the receiving antenna of the zero-IF receiver.
[0018] The signal output terminal of the last-stage fixed-gain amplifier is connected to the signal input terminal of the adjustable attenuator in the zero-IF receiver.
[0019] The control module enables each fixed-gain amplifier through the enable port, so that the gain of each fixed-gain amplifier is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power.
[0020] The device further includes: a filter attenuation circuit. When there is only one fixed-gain amplifier, the filter attenuation circuit is cascaded between the first-stage fixed-gain amplifier and the adjustable attenuator in the zero-IF receiver; when there are multiple fixed-gain amplifiers, the filter attenuation circuit is cascaded between the first-stage fixed-gain amplifier and the second-stage fixed-gain amplifier.
[0021] The number of the fixed-gain amplifiers is determined according to the following method:
[0022] According to the power range of the received signal of the antenna of the zero-IF receiver and the target input power of the ADC in the zero-IF receiver, determine the gain control range; according to the gain difference of the adjustable attenuator in the zero-IF receiver and the gain difference of each fixed-gain amplifier, determine the number of fixed-gain amplifiers required to meet the gain control range.
[0023] The control module is used for:
[0024] Output non-enable signals to the enable ports of each fixed-gain amplifier respectively, and adjust the gain of the adjustable attenuator in the zero-IF receiver to the minimum gain;
[0025] Detect the input power of the ADC in the zero-IF receiver in real time or periodically;
[0026] If the input power of the ADC is not less than the target input power, keep each fixed-gain amplifier in the non-enabled state, and at the same time keep the gain of the adjustable attenuator in the zero-IF receiver at the minimum gain;
[0027] If the input power of the ADC is greater than the first power threshold and less than the target input power, then increase the gain of the adjustable attenuator in the zero-IF receiver until the input power of the ADC is equal to the target input power; wherein, the first power threshold is equal to the target input power of the ADC minus the gain adjustment setting value, and the gain adjustment setting value is the smaller value of the gain difference of the adjustable attenuator and the fixed gain of the next fixed gain amplifier to be enabled;
[0028] If the input power of the ADC is not greater than the first power threshold, then send an enable signal to the enable port of the next fixed gain amplifier to be enabled;
[0029] If all the fixed gain amplifiers are in the enabled state, and the input power of the ADC is not less than the second power threshold and less than the target input power, then increase the gain of the adjustable attenuator in the zero-IF receiver until the input power of the ADC is equal to the target input power; wherein, the second power threshold is equal to the target input power of the ADC minus the gain difference of the adjustable attenuator;
[0030] If all the fixed gain amplifiers are in the enabled state, and the input power of the ADC is less than the second power threshold, then keep each fixed gain amplifier in the enabled state and keep the gain of the adjustable attenuator in the zero-IF receiver at the maximum gain.
[0031] When there is only one fixed gain amplifier, the fixed gain amplifier is: a low-noise fixed gain amplifier;
[0032] When there are multiple fixed gain amplifiers, the first-stage fixed gain amplifier is: a low-noise fixed gain amplifier.
[0033] When there are multiple fixed gain amplifiers, the other fixed gain amplifiers except the first-stage fixed gain amplifier are: fixed gain amplifiers with high saturation power.
[0034] The device is located in a magnetic resonance imaging system.
[0035] The control module is located in the digital signal processing module in the zero-IF receiver.
[0036] An automatic gain adjustment method is applied to the automatic gain adjustment device for a zero-IF receiver as described above, and the method includes:
[0037] The control module controls each fixed gain amplifier to be in the enabled or disabled state, so that the gain of each fixed gain amplifier is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power;
[0038] Moreover, the first-stage fixed-gain amplifier receives the high-frequency signal from the antenna of the zero-IF receiver, and amplifies or attenuates the signal with a fixed gain or an insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed-gain amplifier or the adjustable attenuator in the zero-IF receiver.
[0039] Any fixed-gain amplifier except the first-stage fixed-gain amplifier receives the signal from the previous-stage fixed-gain amplifier, and amplifies or attenuates the signal with a fixed gain or an insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed-gain amplifier or the adjustable attenuator in the zero-IF receiver.
[0040] The control module enables or disables each fixed-gain amplifier, so that the gain of each fixed-gain amplifier is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power, including:
[0041] Output a disable signal to each enable port of each fixed-gain amplifier, and adjust the gain of the adjustable attenuator in the zero-IF receiver to the minimum gain.
[0042] Detect the input power of the ADC in the zero-IF receiver in real time or periodically.
[0043] If the input power of the ADC is not less than the target input power, keep each fixed-gain amplifier in the disabled state, and at the same time keep the gain of the adjustable attenuator in the zero-IF receiver as the minimum gain.
[0044] If the input power of the ADC is greater than the first power threshold and less than the target input power, control the gain of the adjustable attenuator in the zero-IF receiver to increase until the input power of the ADC is equal to the target input power; wherein, the first power threshold is equal to the target input power of the ADC minus the gain adjustment setting value, and the gain adjustment setting value is: the smaller value of the gain difference of the adjustable attenuator and the fixed gain of the next fixed-gain amplifier to be enabled.
[0045] If the input power of the ADC is not greater than the first power threshold, send an enable signal to the enable port of the next fixed-gain amplifier to be enabled.
[0046] If all fixed-gain amplifiers are in the enabled state, and the input power of the ADC is not less than the second power threshold and less than the target input power, control the gain of the adjustable attenuator in the zero-IF receiver to increase until the input power of the ADC is equal to the target input power; wherein, the second power threshold is equal to the target input power of the ADC minus the gain difference of the adjustable attenuator.
[0047] If all fixed-gain amplifiers are in the enabled state and the input power of the ADC is less than the second power threshold, each fixed-gain amplifier is maintained in the enabled state, and at the same time, the gain of the adjustable attenuator in the zero-IF receiver is maintained at the maximum gain.
[0048] The filter attenuation circuit receives the signal output by the first-stage fixed-gain amplifier, filters the signal, attenuates the filtered signal, and outputs the attenuated signal to the next-stage fixed-gain amplifier or the adjustable attenuator in the zero-IF receiver.
[0049] A magnetic resonance imaging (MRI) system, wherein the MRI system includes the automatic gain adjustment device for a zero-IF receiver as described in any one of the above.
[0050] In the embodiments of the present invention, by adding one or more fixed-gain amplifiers with enable ports at the front end of the adjustable attenuator in the zero-IF receiver, and adding a control module for controlling the enabled or disabled state of each fixed-gain amplifier and the gain of the adjustable attenuator in the zero-IF receiver, automatic gain control of the signal on the link from the antenna of the zero-IF receiver to the ADC is achieved, so that the input power of the ADC always tends to the target input power. And since only fixed-gain amplifiers and a control module are added, the cost is low. And because fixed-gain amplifiers are used, there is no need to adjust the gain, the control is simple, the probability of device damage is low, and the reliability is high. Moreover, by adjusting the number of cascaded fixed-gain amplifiers, scenarios with different gain control requirements can be adapted. BRIEF DESCRIPTION OF THE DRAWINGS
[0051] The following will make the above and other features and advantages of the present invention clearer to those of ordinary skill in the art by describing the preferred embodiments of the present invention in detail with reference to the accompanying drawings, wherein:
[0052] Figure 1 is a schematic diagram of using a wireless coil for MR signal transmission and reception in an existing MRI system;
[0053] Figure 2 is a schematic structural diagram of an existing zero-IF receiver;
[0054] Figure 3 is a schematic diagram of an existing radio frequency gain adjustable scheme;
[0055] Figure 4 is a schematic diagram of an existing baseband gain adjustable scheme;
[0056] Figure 5 is a schematic structural diagram of the automatic gain adjustment device for a zero-IF receiver provided by an embodiment of the present invention;
[0057] Figure 6 Schematic diagram of an automatic gain adjustment device for a zero - IF receiver provided by another embodiment of the present invention;
[0058] Figure 7 Flowchart of the automatic gain adjustment method provided by an embodiment of the present invention;
[0059] Figure 8 Flowchart of the method for the control module to perform automatic gain adjustment provided by an embodiment of the present invention;
[0060] Figure 9 Diagram showing the gains of each device in the automatic gain adjustment device set at different received signal powers as shown in Table 1;
[0061] Figure 10 Diagram showing the total gain of the overall link and the input power of the ADC at different received signal powers as shown in Table 1;
[0062] Figure 11 In the application example of the present invention, when the gain of the adjustable attenuator is set to the minimum gain: - 30 dB, diagram of the input power of the ADC when the gains of the two - stage fixed - gain amplifiers are set to different values;
[0063] Among them, the reference numerals are as follows:
[0064]
[0065] Detailed implementation manners
[0066] To make the objectives, technical solutions and advantages of the present invention clearer, the following examples are given to further elaborate on the present invention in detail.
[0067] Figure 5 Schematic diagram of an automatic gain adjustment device 50 for a zero - IF receiver provided by an embodiment of the present invention. The device 50 mainly includes: a control module 51 and at least one fixed - gain amplifier 52. Among them, the fixed - gain amplifier 52 has an enable port 521;
[0068] The control module 51 is respectively connected to each enable port 521 of each fixed - gain amplifier 52; in practical applications, the control module 51 is electrically connected (such as: wire connection) to each enable port 521 of each fixed - gain amplifier 52;
[0069] The control module 51 is connected to the adjustable attenuator 21 in the zero - IF receiver 16; in practical applications, the control module 51 is signal - connected (such as: bus connection) to the adjustable attenuator 21 in the zero - IF receiver 16;
[0070] The control module 51 is connected to the ADC 26 in the zero-IF receiver 16; in practical applications, the control module 51 is signal-connected to the ADC 26 in the zero-IF receiver 16 (such as: bus connection);
[0071] The signal input end of at least one fixed-gain amplifier 52 is connected to the receiving antenna of the zero-IF receiver 16; in practical applications, the signal input end of at least one fixed-gain amplifier 52 is electrically connected to the receiving antenna of the zero-IF receiver 16 (such as: wire connection);
[0072] The signal output end of at least one fixed-gain amplifier 52 is connected to the signal input end of the adjustable attenuator 21 in the zero-IF receiver 16; in practical applications, the signal output end of at least one fixed-gain amplifier 52 is electrically connected to the signal input end of the zero-IF receiver 16 (such as: wire connection).
[0073] In an alternative embodiment, when there are multiple fixed-gain amplifiers 52, the fixed-gain amplifiers 52 are cascaded; and, the signal input end of the first-stage fixed-gain amplifier 52 is connected to the receiving antenna of the zero-IF receiver 16; the signal output end of the last-stage fixed-gain amplifier 52 is connected to the signal input end of the adjustable attenuator 21 in the zero-IF receiver 16. In practical applications, the signal input end of the first-stage fixed-gain amplifier 52 is electrically connected to the receiving antenna of the zero-IF receiver 16 (such as: wire connection); the signal output end of the last-stage fixed-gain amplifier 52 is electrically connected to the signal input end of the adjustable attenuator 21 in the zero-IF receiver 16 (such as: wire connection).
[0074] The control module 51 enables or disables each fixed-gain amplifier 52 by controlling the enable port 521 of each fixed-gain amplifier 52, so that the gain of each fixed-gain amplifier 52 is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator 21 in the zero-IF receiver 16, so that: the input power of the ADC 26 in the zero-IF receiver 16 always tends to the target input power.
[0075] Among them, for the fixed-gain amplifier 52, when it is in the enabled state, its gain is a fixed gain, and when it is in the disabled state, its gain is an insertion loss. For example: the fixed gain of a fixed-gain amplifier 52 is 10 dB, and the insertion loss is -15 dB, then: when the fixed-gain amplifier 52 is in the enabled state, its gain is 10 dB, and when the fixed-gain amplifier 52 is in the disabled state, its gain is -15 dB.
[0076] It should be noted that when the automatic gain adjustment device 50 includes multiple fixed gain amplifiers 52, the models of the fixed gain amplifiers 52 can be different, that is, the fixed gains and / or insertion losses of the fixed gain amplifiers 52 can be different.
[0077] In the above embodiment, by adding one or more fixed gain amplifiers with enable ports at the front end of the adjustable attenuator in the zero-IF receiver, and adding a control module for controlling the enable or disable state of each fixed gain amplifier and the gain of the adjustable attenuator in the zero-IF receiver, automatic gain control of the signal on the link from the antenna of the zero-IF receiver to the ADC is achieved, so that the input power of the ADC always tends to the target input power. Moreover, since only the fixed gain amplifier and the control module are added, the cost is low. And because the fixed gain amplifier is used, there is no need to adjust the gain, the control is simple, the probability of device damage is low, and the reliability is high. Also, by adjusting the number of cascaded fixed gain amplifiers, it can adapt to scenarios with different gain control requirements.
[0078] Figure 6 FIG. is a schematic structural diagram of an automatic gain adjustment device 60 for a zero-IF receiver provided in another embodiment of the present invention. Compared with Figure 5 the automatic gain adjustment device 50 shown, the automatic gain adjustment device 60 further includes: a filter attenuation circuit 53. And when there is only one fixed gain amplifier 52, the filter attenuation circuit 53 is cascaded between the first-stage fixed gain amplifier 52 and the adjustable attenuator 21 in the zero-IF receiver 16; when there are multiple fixed gain amplifiers 52, the filter attenuation circuit 53 is cascaded between the first-stage fixed gain amplifier 52 and the second-stage fixed gain amplifier 52. Figure 6 This is an example when there are multiple fixed gain amplifiers 52.
[0079] The filter attenuation circuit 53 can selectively receive useful signals, suppress out-of-band strong interference, and attenuate the power of useful signals, so that the output signal does not cause saturation of the subsequent circuit.
[0080] Whether it is the automatic gain adjustment device 50 or the automatic gain adjustment device 60, the number of fixed gain amplifiers 52 used is determined in the following manner: According to the power range of the received signal of the antenna of the zero-IF receiver 16 and the target input power of the ADC 26 in the zero-IF receiver 16, the gain control range is determined. According to the gain difference of the adjustable attenuator 21 in the zero-IF receiver 16 and the gain difference of each fixed gain amplifier 52, the number of fixed gain amplifiers 52 required to meet the gain control range is determined.
[0081] Among them, the gain difference of the adjustable attenuator 21, that is, the difference between the maximum gain and the minimum gain of the adjustable attenuator. For example, if the adjustable range of the gain of the adjustable attenuator 21 is 0 to -30 dB, then the gain difference of the adjustable attenuator 21 is 0 - (-30) = 30 dB; the gain difference of the fixed-gain amplifier 52, that is, the difference between the fixed gain of the fixed-gain amplifier 52 and the insertion loss. For example, if the fixed gain of a fixed-gain amplifier 52 is 10 dB and the insertion loss is -15 dB, then the gain difference of this fixed-gain amplifier 52 is 10 - (-15) = 25 dB.
[0082] For example: the power range of the received signal of the antenna of the zero-IF receiver 16 is [-a, b], and the target input power of the ADC 26 is -c. Then [-c - b, -c - (-a)], that is, [-c - b, -c + a] is the gain control range. After cascading the adjustable attenuator 21 and the required fixed-gain amplifiers 52 in the zero-IF receiver 16, the total gain of the cascade only needs to satisfy the gain control range.
[0083] In an alternative embodiment, the control module 51 is specifically configured to:
[0084] Output a disenable signal to each enable port 521 of each fixed-gain amplifier 52 respectively, and adjust the gain of the adjustable attenuator 21 in the zero-IF receiver 16 to the minimum gain;
[0085] Detect the input power of the ADC 26 in the zero-IF receiver 16 in real time or periodically;
[0086] If the input power of the ADC 26 is not less than the target input power, keep each fixed-gain amplifier 52 in the disenable state, and at the same time keep the gain of the adjustable attenuator 21 in the zero-IF receiver 16 at the minimum gain;
[0087] If the input power of the ADC 26 is greater than the first power threshold and less than the target input power, control the gain of the adjustable attenuator 21 in the zero-IF receiver 16 to increase until the input power of the ADC 26 is equal to the target input power; among them, the first power threshold is equal to the target input power of the ADC 26 minus the gain adjustment setting value, and the gain adjustment setting value is the smaller value between the gain difference of the adjustable attenuator 21 and the fixed gain of the next fixed-gain amplifier 52 to be enabled;
[0088] If the input power of the ADC 26 is not greater than the first power threshold, send an enable signal to the enable port 521 of the next fixed-gain amplifier 52 to be enabled;
[0089] If all fixed gain amplifiers 52 are in the enabled state, and the input power of ADC 26 is not less than the second power threshold and less than the target input power, then increase the gain of the adjustable attenuator 21 in the zero-IF receiver 16 until the input power of ADC 26 is equal to the target input power; wherein, the second power threshold is equal to the target input power of ADC 26 minus the gain difference of the adjustable attenuator 21.
[0090] If all fixed gain amplifiers 52 are in the enabled state, and the input power of ADC 26 is less than the second power threshold, then keep each fixed gain amplifier 52 in the enabled state, and at the same time keep the gain of the adjustable attenuator 21 in the zero-IF receiver 16 at the maximum gain.
[0091] In practical applications, when there is only one fixed gain amplifier 52, the fixed gain amplifier 52 is: a low-noise fixed gain amplifier. When there are multiple fixed gain amplifiers 52, the first-stage fixed gain amplifier 52 can be: a low-noise fixed gain amplifier. When there are multiple fixed gain amplifiers 52, the other fixed gain amplifiers 52 except the first-stage fixed gain amplifier 52 can be: fixed gain amplifiers with high saturation power.
[0092] In an alternative embodiment, the automatic gain adjustment device 50 and the automatic gain adjustment device 60 are located in the MRI system.
[0093] In an alternative embodiment, the control module 51 is located in the digital signal processing module 17 in the zero-IF receiver 16. At this time, the communication between the control module 51 and the ADC 26 is realized through the signal connection (such as: bus) between the digital signal processing module 17 and the ADC 26.
[0094] An embodiment of the present invention further provides an MRI system, including the automatic gain adjustment device 50 or 60 for the zero-IF receiver described in any of the above embodiments.
[0095] Figure 7 It is a flowchart of the automatic gain adjustment method provided by the embodiment of the present invention, which is applied in the automatic gain adjustment device 50 or 60 for the zero-IF receiver described above. The specific steps are as follows:
[0096] Step 701: The control module 51 makes the gain of each fixed gain amplifier 52 a fixed gain or an insertion loss by controlling each fixed gain amplifier 52 to be in the enabled or disabled state, and adjusts the gain of the adjustable attenuator 21 in the zero-IF receiver 16 so that: the input power of the ADC 26 in the zero-IF receiver 16 always tends to the target input power.
[0097] Here, "tends to" the target input power means: as close as possible, and preferably equal to the target input power.
[0098] Step 702: The first-stage fixed-gain amplifier 52 receives the high-frequency signal from the antenna of the zero-IF receiver 16, and amplifies or attenuates the signal using a fixed gain or insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed-gain amplifier 52 or the adjustable attenuator 21 of the zero-IF receiver 16.
[0099] In this step, if there is only one fixed-gain amplifier 52, the first-stage fixed-gain amplifier 52 sends the amplified or attenuated signal to the adjustable attenuator 21 in the zero-IF receiver 16; if there are multiple fixed-gain amplifiers 52, the first-stage fixed-gain amplifier 52 sends the amplified or attenuated signal to the second-stage fixed-gain amplifier 52.
[0100] In an alternative embodiment, if a filter-attenuation circuit 53 is cascaded after the first-stage fixed-gain amplifier 52, the filter-attenuation circuit 53 receives the signal output by the first-stage fixed-gain amplifier 52, filters the signal, and attenuates the filtered signal, and outputs the attenuated signal to the subsequent fixed-gain amplifier 52 or the adjustable attenuator 21 in the zero-IF receiver 16.
[0101] Among them, if there is only one fixed-gain amplifier 52, the filter-attenuation circuit 53 sends the attenuated signal to the adjustable attenuator 21 in the zero-IF receiver 16; if there are multiple fixed-gain amplifiers 52, the filter-attenuation circuit 53 sends the attenuated signal to the second-stage fixed-gain amplifier 52.
[0102] Step 703: Any fixed-gain amplifier 52 other than the first-stage fixed-gain amplifier 52 receives the signal from the previous-stage fixed-gain amplifier 52, and amplifies or attenuates the signal using a fixed gain or insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed-gain amplifier 52 or the adjustable attenuator 21 of the zero-IF receiver 16.
[0103] In this step, if the fixed-gain amplifier 52 is the last-stage fixed-gain amplifier, the amplified or attenuated signal is sent to the adjustable attenuator 21 of the zero-IF receiver 16, otherwise it is sent to the next-stage fixed-gain amplifier 52.
[0104] Figure 8 The figure is a flowchart of the method for the control module 51 provided by the embodiment of the present invention to perform automatic gain adjustment, and the specific steps are as follows:
[0105] Step 801: The control module 51 outputs a disenable signal to each enable port 521 of each fixed gain amplifier 52 respectively, and adjusts the gain of the adjustable attenuator 21 in the zero-IF receiver 16 to the minimum gain.
[0106] Step 802: Obtain the input power of the ADC 26 from the ADC 26 in the zero-IF receiver 16 in real time or periodically.
[0107] Step 803: Determine whether the input power of the ADC 26 is not less than the target input power. If so, execute Step 804; otherwise, execute Step 805.
[0108] Step 804: Keep each fixed gain amplifier 52 in the disenable state, and at the same time keep the gain of the adjustable attenuator 21 in the zero-IF receiver 16 at the minimum gain, and this process ends.
[0109] Step 805: Determine whether the input power of the ADC 26 is greater than the first power threshold and less than the target input power. If so, execute Step 806; otherwise, execute Step 807.
[0110] Step 806: Control the gain of the adjustable attenuator 21 in the zero-IF receiver 16 to increase until the input power of the ADC 26 is equal to the target input power, and this process ends.
[0111] Wherein, the first power threshold is equal to the target input power of the ADC 26 minus the gain adjustment setting value, and the gain adjustment setting value is the smaller value between the gain difference of the adjustable attenuator 21 and the fixed gain of the next fixed gain amplifier 52 to be enabled. Wherein, when the control module 51 enables each fixed gain amplifier 52, it can be enabled one by one according to a preset order. For example: in the order from the first stage to the last stage, or in the order from the last stage to the first stage. The "next fixed gain amplifier 52 to be enabled" in this step refers to the next fixed gain amplifier 52 that should be alternately enabled according to the preset order. For example: the preset order is in the order from the first stage to the last stage, and currently the first to third stage fixed gain amplifiers 52 have all been enabled, then the next fixed gain amplifier 52 to be enabled is the fourth stage fixed gain amplifier 52.
[0112] Step 807: Send an enable signal to the enable port 521 of the next fixed gain amplifier 52 to be enabled.
[0113] Step 808: Determine whether all fixed gain amplifiers 52 have been enabled. If so, execute Step 809; otherwise, return to Step 805.
[0114] Step 809: Determine whether the input power of ADC26 is not less than the second power threshold and less than the target input power. If so, execute Step 810; otherwise, execute Step 811.
[0115] Step 810: Control the gain of the adjustable attenuator 21 in the zero-IF receiver 16 to increase until the input power of ADC26 is equal to the target input power, and this process ends.
[0116] Among them, the second power threshold is equal to the target input power of ADC26 minus the gain difference of the adjustable attenuator 21.
[0117] Step 811: Keep each fixed-gain amplifier 52 in the enabled state, and at the same time keep the gain of the adjustable attenuator 21 in the zero-IF receiver 16 at the maximum gain.
[0118] The following gives an application example of the present invention:
[0119] In this example, the frequency band of the signal received by the antenna of the zero-IF receiver is the 5.8G frequency band.
[0120] In this example, the adjustable range of the gain of the adjustable attenuator in the zero-IF receiver is: 0 to -30 dB;
[0121] In this example, the power range of the signal received by the antenna of the zero-IF receiver is -45 dBm (decibel milliwatt) to 35 dBm, and the full-scale input power of the ADC in the zero-IF receiver is -13 dBm. In this example, the target input power of the ADC is -28 dBm, that is, an automatic gain adjustment device needs to be designed to make the input of the zero-IF receiver meet -15 dBFS (full decibel scale). It can be known that the gain control range is: [-28 - 35, -28 - (-45)], that is, [-63, 17].
[0122] This example uses an automatic gain adjustment device 60. Among them, the gain of the filter attenuation circuit 53 is -3 dB. In this example, the fixed gain of the 5.8G frequency band fixed-gain amplifier when enabled is 10 dB, and the insertion loss when not enabled is -15 dB, and the gain difference is 25 dB. Combining the gain difference of the adjustable attenuator: 30 dB and the gain of the filter attenuation circuit -3 dB, it can be known that using two-stage fixed-gain amplifiers can meet the gain control range [-63, 17] requirements.
[0123] In this example, the process of the control module 51 for automatic gain adjustment is as follows:
[0124] First, a initial state is given: set the gains of all levels to the lowest, that is, neither of the two fixed-gain amplifiers 52 is enabled, and the gain is the insertion loss: -15 dB. The gain of the adjustable attenuator 21 is set to the minimum gain: -30 dB. At this time, the total gain of the entire link is: -15 - 3 - 15 - 30 = -63 dB;
[0125] Obtain the input power Pin of the ADC 26 in real time and judge:
[0126] If Pin >= -28 dBm, the total gain of the entire link remains unchanged at -63 dB. At this time, the input power of the ADC 26 reaches the upper limit, and the maximum attenuation is maintained to protect the circuit;
[0127] If -53 dBm < Pin < -28 dBm, adjust the gain of the adjustable attenuator 21 (the adjustment range is -5 to -30 dB) until it satisfies: -29 dBm < Pin < -27 dBm; where, -53 dBm is obtained from -28 dBm - 25 dBm, and 25 dBm is the smaller value of the gain difference of 30 dB of the adjustable attenuator 21 and the gain difference of 25 dB of the first-stage fixed-gain amplifier 52; Since in practical applications, it is difficult to make the input power of the ADC 26 exactly equal to the target input power of -28 dBm, therefore, an error of ±1 dB is allowed here, that is, the input power pin of the ADC 26 satisfies: -29 dBm < Pin < -27 dBm, which is considered to reach the adjustment target, and the specific size of the error can be set according to actual requirements or experience, etc.;
[0128] If Pin <= -53 dBm, it means that the input signal of the ADC 26 is weak and the front-end attenuation is too large, and amplification is required. Then enable the first-stage fixed-gain amplifier. At this time, the total gain of the entire link is: 10 - 3 - 15 - 30 = -38 dB. Detect the input power pin of the ADC and judge:
[0129] If -53 dBm < Pin < -28 dBm, adjust the gain of the adjustable attenuator 21 (the adjustment range is -5 to -30 dB) until it satisfies: -29 dBm < Pin < -27 dBm; where, -53 dBm is obtained from -28 dBm - 25 dBm, and 25 dBm is the smaller value of the gain difference of 30 dB of the adjustable attenuator 21 and the gain difference of 25 dB of the second-stage fixed-gain amplifier 52;
[0130] If Pin <= -53 dBm, it indicates that the input signal of ADC 26 is weak and the front-end attenuation is excessive, requiring amplification. Then, enable the second-stage fixed-gain amplifier. At this time, both two-stage fixed-gain amplifiers are enabled, and the total gain of the entire link is: 10 - 3 + 10 - 30 = -13 dB. Detect the input power pin of the ADC and make a judgment:
[0131] If -58 dBm < Pin < -28 dBm, then adjust the gain of the adjustable attenuator 21 (the adjustment range is 0 to -30 dB) until it satisfies: -29 dBm < Pin < -27 dBm; among them, -58 dBm is obtained from -28 dBm - 30 dBm, and 30 dBm is obtained from: the gain difference of the adjustable attenuator 21 is 30 dB;
[0132] If Pin < -58 dBm, at this time, the input power of the ADC reaches the lower limit. Maintain the maximum gain of the entire link 10 - 3 + 10 - 0 = 17 dB to make the input power of the ADC as close as possible to the target input power of -28 dBm.
[0133] Table 1 shows the automatic gain adjustment strategy when adjusting the input power of the ADC to the target input power when the antenna of the zero-IF receiver receives signals with different powers (referred to as the received signal power):
[0134]
[0135]
[0136] Table 1
[0137] Figure 9 It is a diagram showing the gains of each device in the automatic gain adjustment device 60 set under different received signal powers as shown in Table 1. Among them, the abscissa is the received signal power, the ordinate is the gain, the small hollow circle is the gain of the first-stage fixed-gain amplifier, the small hollow rectangle is the gain of the second-stage fixed-gain amplifier, and the small hollow triangle is the received signal power.
[0138] Figure 10 It is a diagram showing the total gain of the entire link and the input power of the ADC under different received signal powers as shown in Table 1. Among them, the abscissa is the received signal power, the ordinate is the gain or power, the small hollow circle is the input power of the ADC, and the small hollow rectangle is the total gain of the entire link.
[0139] Figure 11In this example, when the gain of the adjustable attenuator 21 is set to the minimum gain: -30 dB, the diagram of the input power of the ADC when the two-stage fixed-gain amplifiers are set to different gains. Among them, the abscissa is the received signal power, the ordinate is the gain or power, the small hollow circles are the gains of the first-stage fixed-gain amplifier, the small hollow rectangles are the gains of the second-stage fixed-gain amplifier, and the small solid circles are the input power of the ADC.
[0140] Those skilled in the art can understand that the features recited in the various embodiments and / or claims of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recited in this application. In particular, without departing from the spirit and teachings of this application, the features recited in the various embodiments and / or claims of this application can be combined and / or combined in various ways, and all such combinations and / or combinations fall within the scope disclosed in this application.
[0141] Specific embodiments are used herein to illustrate the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application, and is not used to limit the present application. For those skilled in the art, according to the idea, spirit and principle of the present application, changes can be made in the specific implementation manner and application scope, and any modifications, equivalent replacements, improvements, etc. made by them should be included in the scope protected by the present application.
Claims
1. An automatic gain adjustment device for a zero-IF receiver, characterized in that, the device includes: a control module and at least one fixed-gain amplifier, wherein the fixed-gain amplifier has an enable port; the control module is connected to the enable port of the at least one fixed-gain amplifier; the control module is connected to an adjustable attenuator in the zero-IF receiver; the control module is connected to an analog-to-digital converter ADC in the zero-IF receiver; the signal input end of the at least one fixed-gain amplifier is connected to the receiving antenna of the zero-IF receiver; the signal output end of the at least one fixed-gain amplifier is connected to the signal input end of the adjustable attenuator in the zero-IF receiver.
2. The device according to claim 1, characterized in that, when there are multiple fixed-gain amplifiers, the fixed-gain amplifiers are cascaded; the signal input end of the first-stage fixed-gain amplifier is connected to the receiving antenna of the zero-IF receiver; the signal output end of the last-stage fixed-gain amplifier is connected to the signal input end of the adjustable attenuator in the zero-IF receiver.
3. The device according to claim 1, characterized in that, the control module makes the gain of each fixed-gain amplifier be a fixed gain or an insertion loss by controlling the enable ports of the fixed-gain amplifiers, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power.
4. The device according to claim 1, characterized in that, the device further includes: a filter attenuation circuit, and when there is only one fixed-gain amplifier, the filter attenuation circuit is cascaded between the first-stage fixed-gain amplifier and the adjustable attenuator in the zero-IF receiver; when there are multiple fixed-gain amplifiers, the filter attenuation circuit is cascaded between the first-stage fixed-gain amplifier and the second-stage fixed-gain amplifier.
5. The device according to claim 1, characterized in that, the number of the fixed-gain amplifiers is determined according to the following method: determine the gain control range according to the power range of the received signal of the antenna of the zero-IF receiver and the target input power of the ADC in the zero-IF receiver; determine the number of fixed-gain amplifiers required to meet the gain control range according to the gain difference of the adjustable attenuator in the zero-IF receiver and the gain difference of each fixed-gain amplifier.
6. The device according to claim 1, characterized in that, the control module is used for: outputting a disenable signal to each enable port of each fixed-gain amplifier respectively, and adjusting the gain of the adjustable attenuator in the zero-IF receiver to the minimum gain; detecting the input power of the ADC in the zero-IF receiver in real time or periodically; if the input power of the ADC is not less than the target input power, keep each fixed-gain amplifier in the disenable state, and at the same time keep the gain of the adjustable attenuator in the zero-IF receiver at the minimum gain; If the input power of the ADC is greater than the first power threshold and less than the target input power, then increase the gain of the adjustable attenuator in the zero-IF receiver until the input power of the ADC is equal to the target input power; wherein, the first power threshold is equal to the target input power of the ADC minus the gain adjustment setting value, and the gain adjustment setting value is the smaller value between the gain difference of the adjustable attenuator and the fixed gain of the next fixed gain amplifier to be enabled. If the input power of the ADC is not greater than the first power threshold, then send an enable signal to the enable port of the next fixed gain amplifier to be enabled. If all fixed gain amplifiers are in the enabled state, and the input power of the ADC is not less than the second power threshold and less than the target input power, then increase the gain of the adjustable attenuator in the zero-IF receiver until the input power of the ADC is equal to the target input power; wherein, the second power threshold is equal to the target input power of the ADC minus the gain difference of the adjustable attenuator. If all fixed gain amplifiers are in the enabled state, and the input power of the ADC is less than the second power threshold, then keep each fixed gain amplifier in the enabled state and keep the gain of the adjustable attenuator in the zero-IF receiver at the maximum gain.
7. The device according to claim 1, characterized in that when there is only one fixed gain amplifier, the fixed gain amplifier is: a low-noise fixed gain amplifier; when there are multiple fixed gain amplifiers, the first-stage fixed gain amplifier is: a low-noise fixed gain amplifier.
8. The device according to claim 1, characterized in that when there are multiple fixed gain amplifiers, the other fixed gain amplifiers except the first-stage fixed gain amplifier are: fixed gain amplifiers with high saturation power.
9. An automatic gain adjustment method, characterized in that applied to the automatic gain adjustment device for a zero-IF receiver as described in any one of claims 1 to 8, the method includes: The control module controls each fixed gain amplifier to be in the enabled or disabled state, so that the gain of each fixed gain amplifier is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power.
10. The method according to claim 9, characterized in that when there are multiple fixed gain amplifiers, each fixed gain amplifier is cascaded; The first-stage fixed gain amplifier receives the high-frequency signal from the antenna of the zero-IF receiver, and amplifies or attenuates the signal with a fixed gain or an insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed gain amplifier or the adjustable attenuator in the zero-IF receiver; Any fixed gain amplifier except the first-stage fixed gain amplifier receives the signal from the previous-stage fixed gain amplifier, and amplifies or attenuates the signal with a fixed gain or an insertion loss according to the current enabled or disabled state, and sends the amplified or attenuated signal to the subsequent fixed gain amplifier or the adjustable attenuator in the zero-IF receiver.
11. The method according to claim 9, wherein, the control module enables or disables each fixed-gain amplifier, so that the gain of each fixed-gain amplifier is a fixed gain or an insertion loss, and adjusts the gain of the adjustable attenuator in the zero-IF receiver, so that: the input power of the ADC in the zero-IF receiver always tends to the target input power, including: outputting a disable signal to each enable port of each fixed-gain amplifier, and adjusting the gain of the adjustable attenuator in the zero-IF receiver to the minimum gain; detecting the input power of the ADC in the zero-IF receiver in real time or periodically; if the input power of the ADC is not less than the target input power, keeping each fixed-gain amplifier in the disabled state, and at the same time keeping the gain of the adjustable attenuator in the zero-IF receiver at the minimum gain; if the input power of the ADC is greater than the first power threshold and less than the target input power, controlling the gain of the adjustable attenuator in the zero-IF receiver to increase until the input power of the ADC is equal to the target input power; wherein, the first power threshold is equal to the target input power of the ADC minus the gain adjustment setting value, and the gain adjustment setting value is: the smaller value of the gain difference of the adjustable attenuator and the fixed gain of the next fixed-gain amplifier to be enabled; if the input power of the ADC is not greater than the first power threshold, sending an enable signal to the enable port of the next fixed-gain amplifier to be enabled; if all fixed-gain amplifiers are in the enabled state, and the input power of the ADC is not less than the second power threshold and less than the target input power, controlling the gain of the adjustable attenuator in the zero-IF receiver to increase until the input power of the ADC is equal to the target input power; wherein, the second power threshold is equal to the target input power of the ADC minus the gain difference of the adjustable attenuator; if all fixed-gain amplifiers are in the enabled state, and the input power of the ADC is less than the second power threshold, keeping each fixed-gain amplifier in the enabled state, and at the same time keeping the gain of the adjustable attenuator in the zero-IF receiver at the maximum gain.
12. The method according to claim 9, wherein, the filter attenuation circuit receives the signal output by the first-stage fixed-gain amplifier, filters the signal, and attenuates the filtered signal, and outputs the attenuated signal to the next-stage fixed-gain amplifier or the adjustable attenuator in the zero-IF receiver.
13. A magnetic resonance imaging (MRI) system, wherein, the MRI system includes the automatic gain adjustment device for a zero-IF receiver according to any one of claims 1 to 8.