Transceiver circuit and self-correction method

Abstract

Embodiments of the present disclosure relate to a transceiver circuit and a self-correction method, wherein the transceiver circuit is configured to couple an oscillator crystal. The transceiver circuit includes a local oscillator, a filter circuit, a control circuit, and a radio frequency signal generating circuit. The local oscillator includes a capacitive element. The local oscillator is configured to generate a phase-locked loop signal based on the oscillation frequency of the oscillation crystal and the capacitance value of the capacitive element. The filter circuit is configured to generate a filter signal according to the phase-locked loop signal. The control circuit is configured to adjust the capacitance value to an adjusted capacitance value according to the filter signal and the phase-locked loop signal. The local oscillator is also configured to generate a corrected local oscillation signal according to the oscillation frequency and the adjusted capacitance value. The radio frequency signal generating circuit is configured to generate a radio frequency signal according to the corrected local oscillation signal and the baseband signal.

Description

Technical Field

[0001] The embodiments described in the present disclosure are related to a calibration technology, and more particularly to a transceiver circuit and a self-calibration method capable of calibrating frequency offset problems. Background Art

[0002] With the development of communication technology, the transceiver circuits between two electronic devices can use wireless communication technology to transmit data. However, when environmental conditions change (eg, temperature rises), the transceiver circuits may experience frequency offset problems. Summary of the invention

[0003] Some embodiments of the present disclosure relate to a transceiver circuit. The transceiver circuit is configured to couple an oscillator crystal. The transceiver circuit includes a local oscillator, a filter circuit, a control circuit, and a radio frequency signal generating circuit. The local oscillator includes a capacitive element. The local oscillator is configured to generate a phase-locked loop signal based on the oscillation frequency of the oscillation crystal and the capacitance value of the capacitive element. The filter circuit is configured to generate a filter signal according to the phase-locked loop signal. The control circuit is configured to adjust the capacitance value to an adjusted capacitance value according to the filter signal and the phase-locked loop signal. The local oscillator is also configured to generate a corrected local oscillation signal according to the oscillation frequency and the adjusted capacitance value. The radio frequency signal generating circuit is configured to generate a radio frequency signal according to the corrected local oscillation signal and the baseband signal.

[0004] Some embodiments of the present disclosure are related to a self-calibration method. The self-calibration method includes: generating a phase-locked loop signal by a local oscillator based on the oscillation frequency of an oscillation crystal and the capacitance value of a capacitive element; generating a filter signal by a filter circuit according to the phase-locked loop signal; adjusting the capacitance value to an adjusted capacitance value by a control circuit according to the filter signal and the phase-locked loop signal; generating a corrected local oscillation signal by a local oscillator according to the oscillation frequency and the adjusted capacitance value; and generating a radio frequency signal by a radio frequency signal generating circuit according to the corrected local oscillation signal and a baseband signal.

[0005] In summary, the transceiver circuit and self-correction method disclosed in the present invention can correct the frequency offset problem quickly and in real time, and can be applied to different transceiver devices and different oscillator crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more clearly understood, the following is a description of the accompanying drawings:

[0007] Figure 1 is a schematic diagram of a transceiver circuit and an oscillator crystal according to some embodiments of the present disclosure;

[0008] Figure 2 It is illustrated according to some embodiments of the present disclosure Figure 1 Frequency response diagram of the filter circuit;

[0009] Figure 3 is a circuit diagram of a capacitive element according to some embodiments of the present disclosure; and

[0010] Figure 4 is a flow chart of a self-calibration method according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0011] As used herein, the term “coupled” may also refer to “electrically coupled”, and the term “connected” may also refer to “electrically connected.” “Coupled” and “connected” may also refer to two or more elements cooperating or interacting with each other.

[0012] refer to Figure 1 . Figure 1 Schematic diagram of a transceiver circuit 100 and an oscillator crystal CY according to some embodiments of the present disclosure. The transceiver circuit 100 can be coupled to the oscillator crystal CY and work in conjunction with the oscillator crystal CY to achieve a specific function (e.g., generate a radio frequency signal RS). In some embodiments, the transceiver circuit 100 can be a single chip system (System on Chip, SoC) or a part of a single chip system.

[0013] by Figure 1 For example, the transceiver circuit 100 includes a local oscillator 110, a filter circuit 120, a control circuit 130, and a radio frequency signal generating circuit 140. The filter circuit 120 is coupled to the local oscillator 110. The control circuit 130 is coupled to the local oscillator 110 and the filter circuit 120. The radio frequency signal generating circuit 140 is coupled to the local oscillator 110.

[0014] by Figure 1 For example, the local oscillator 110 includes a capacitive element C, a phase-locked loop circuit 112, and a frequency divider 114. The phase-locked loop circuit 112 is coupled to an oscillating crystal CY and the capacitive element C. The frequency divider 114 is coupled to the phase-locked loop circuit 112. The phase-locked loop circuit 112 may generate a phase-locked loop signal PS based on an oscillation frequency of the oscillating crystal CY and a capacitance value of the capacitive element C. In some embodiments, the oscillation frequency of the oscillating crystal CY may have a frequency offset due to changes in environmental conditions.

[0015] by Figure 1For example, the filter circuit 120 is coupled to the phase-locked loop circuit 112 to receive the phase-locked loop signal PS. The filter circuit 120 can generate a filter signal FS according to the phase-locked loop signal PS. In some embodiments, the filter circuit 120 is a band-pass filter. The band-pass filter can be implemented by a transmission line, but the present disclosure is not limited thereto.

[0016] refer to Figure 2 . Figure 2 It is illustrated according to some embodiments of the present disclosure Figure 1 The target frequency TF is the frequency of the phase-locked loop signal PS when the oscillation frequency of the oscillation crystal CY does not shift. Figure 2 For example, the frequency response of the filter circuit 120 is designed to have the lowest reflection coefficient at the target frequency TF (i.e., the valley of the curve in the figure). That is, when the oscillation frequency of the oscillation crystal CY does not shift, most of the components corresponding to the target frequency TF in the phase-locked loop signal PS input into the filter circuit 120 will pass through the filter circuit 120, while most of the remaining components of the phase-locked loop signal PS input into the filter circuit 120 will be filtered out by the filter circuit 120.

[0017] It should be particularly noted that since the component characteristics of the filter circuit 120 are less susceptible to changes in environmental conditions (such as temperature rise, etc.), even if the oscillation frequency of the oscillation crystal CY shifts due to changes in environmental conditions, the frequency response of the filter circuit 120 is less likely to change due to changes in environmental conditions.

[0018] Reference again Figure 1 The control circuit 130 can adjust the capacitance of the capacitive element C in the local oscillator 110 according to the filter signal FS and the phase-locked loop signal PS. For example, the control circuit 130 includes a mixer 132 , a comparison circuit 134 , and a driving circuit 136 .

[0019] The mixer 132 is coupled to the filter circuit 120 and the phase-locked loop circuit 112 to receive the filter signal FS and the phase-locked loop signal PS, respectively. The mixer 132 can perform a mixing process on the filter signal FS and the phase-locked loop signal PS to generate a direct current signal DC. When the oscillation frequency of the oscillation crystal CY does not have a frequency shift (i.e., corresponds to the target frequency TF), the frequency of the phase-locked loop signal PS also does not have a frequency shift (also corresponds to the target frequency TF). Since the frequency of the phase-locked loop signal PS corresponds to the target frequency TF, the phase-locked loop signal PS input into the filter circuit 120 passes through the filter circuit 120 with almost no attenuation (e.g., the phase-locked loop signal PS is input to the filter circuit 120). Figure 2On the other hand, since the phase-locked loop signal PS directly input to the mixer 132 from the phase-locked loop circuit 112 does not flow through other electronic components, the signal energy of the phase-locked loop signal PS input to the mixer 132 is also almost not attenuated. The DC signal DC generated by the mixer 132 according to the filtered signal FS with almost no attenuation of energy and the phase-locked loop signal PS with almost no attenuation of energy will have a maximum DC voltage value. This DC voltage value can be pre-stored in a storage circuit or register as the maximum DC voltage DCM.

[0020] On the contrary, when the frequency of the oscillator crystal CY shifts due to changes in environmental conditions (i.e., does not correspond to the target frequency TF), the frequency of the phase-locked loop signal PS also shifts (also does not correspond to the target frequency TF). Since the frequency of the phase-locked loop signal PS does not correctly correspond to the target frequency TF, many components of the phase-locked loop signal PS input into the filter circuit 120 will be filtered out by the filter circuit 120 (e.g., Figure 2 At the non-trough position shown in the curve, the reflection coefficient of the section not corresponding to the target frequency TF will increase). Equivalently, the signal energy of the filter signal FS is greatly attenuated. On the other hand, since the phase-locked loop signal PS directly input into the mixer 132 from the phase-locked loop circuit 112 does not flow through other electronic components, the signal energy of the phase-locked loop signal PS input into the mixer 132 is almost not attenuated. In this case, the DC signal DC generated by the mixer 132 based on the filter signal FS with greatly attenuated energy and the phase-locked loop signal PS with almost no attenuation will not have the maximum DC voltage value.

[0021] Based on the above principle, the comparison circuit 134 can compare the voltage of the DC signal DC with the maximum DC voltage DCM to generate a comparison result CR. The driving circuit 136 can generate a control signal CT1 according to the comparison result CR to adjust the capacitance value of the capacitive element C in the local oscillator 110. For example, if the comparison result CR indicates that the voltage of the DC signal DC is equal to the maximum DC voltage DCM, it means that the oscillation crystal CY has not undergone frequency deviation. In this case, there is no need to calibrate the phase-locked loop signal PS. In other words, there is no need to adjust the capacitance value of the capacitive element C. If the comparison result CR indicates that the voltage of the DC signal DC is less than the maximum DC voltage DCM (because the phase-locked loop signal PS will generate a filter signal FS with greatly attenuated energy after passing through the filter circuit 120), it means that the oscillation crystal CY has undergone frequency deviation. In this case, the phase-locked loop signal PS needs to be calibrated. In other words, the capacitance value of the capacitive element C needs to be adjusted.

[0022] In some embodiments, the driving circuit 136 can adjust the capacitance value of the capacitive element C. These capacitance values ​​correspond to different DC voltages, and the maximum DC voltage DCM is the largest one of these DC voltages. In some embodiments, the driving circuit 136 can adjust the capacitance value of the capacitive element C to a capacitance value corresponding to the maximum DC voltage DCM. How the control signal CT1 adjusts the capacitance value of the capacitive element C will be described in the following paragraphs. Figure 3 Have a discussion.

[0023] Next, the PLL circuit 112 may generate a calibrated PLL signal PS' according to the oscillation frequency of the oscillating crystal CY and the adjusted capacitance value, and the frequency divider 114 may perform a frequency division process on the calibrated PLL signal PS' to generate a calibrated local oscillation signal OS'.

[0024] The RF signal generating circuit 140 can generate a RF signal RS according to the calibrated local oscillation signal OS' and the baseband signal BS. For example, the RF signal generating circuit 140 includes a baseband circuit 142, a mixer 144, and a RF circuit 146. The mixer 144 is coupled to the mixer 114 and the baseband circuit 142 to receive the calibrated local oscillation signal OS' and the baseband signal BS, respectively. The mixer 144 can perform a mixing process on the calibrated local oscillation signal OS' and the baseband signal BS to generate a mixing signal MS. The RF circuit 146 is coupled to the mixer 144 to receive the mixing signal MS. The RF circuit 146 can generate a RF signal RS according to the mixing signal MS.

[0025] refer to Figure 3 . Figure 3 Detailed circuit diagram of the capacitive element C according to some embodiments of the present disclosure. In some embodiments, the capacitive element C in the local oscillator 110 can be implemented by a switched capacitor array, and the capacitance value of the capacitive element C can be dynamically adjusted. For example, the control signal CT1 can correspond to a specific capacitance index value (cap index). When the capacitance index value increases, the capacitance value of the capacitive element C decreases, so that the frequency of the corrected phase-locked loop signal PS' increases. When the capacitance index value decreases, the capacitance value of the capacitive element C increases, so that the frequency of the corrected phase-locked loop signal PS' decreases.

[0026] by Figure 3 For example, the capacitive element C includes capacitors C1 -Cn and switches T1 -Tn. Figure 1 The control signal CT1 generated by the driving circuit 136 can be used to control the switches T1 -Tn to be turned on or off, so as to adjust the capacitance value of the capacitive element C.

[0027] Figure 3The implementation of the capacitive element C is for illustrative purposes only, but the present disclosure is not limited thereto. Various implementations of the capacitive element C (eg, the number of capacitors, the number of switches, the coupling method, etc.) are all within the scope of the present disclosure.

[0028] In some related technologies, a temperature sensor needs to be set up in the system and a lookup table needs to be established in advance to establish the capacitance adjustment amount under various temperatures. Then, the detected temperature is fed back to the driving circuit, and the driving circuit uses the lookup table for correction. This will be time-consuming and cannot be corrected in real time. In addition, because the oscillator crystal has individual yield and applicability issues (for example: different manufacturer specifications or adjustments), a lookup table cannot be applied to different transceivers or different oscillator crystals.

[0029] Compared to the above related art, the transceiver circuit 100 disclosed in the present invention does not need to establish a lookup table, thus saving time and achieving real-time calibration. In addition, the transceiver circuit 100 disclosed in the present invention has a self-calibration mechanism, thus being applicable to different transceiver devices or different oscillator crystals.

[0030] refer to Figure 4 . Figure 4 is a flow chart of a self-calibration method 400 according to some embodiments of the present disclosure. In some embodiments, the self-calibration method 400 may be applied to Figure 1 The self-calibration method 400 includes operations S410, S420, S430, S440, and S450.

[0031] In operation S410, the local oscillator 110 generates a phase-locked loop signal PS based on the oscillation frequency of the oscillation crystal CY and the capacitance of the capacitive element C. In some embodiments, the phase-locked loop circuit 112 in the local oscillator 110 can generate the phase-locked loop signal PS according to the oscillation frequency of the oscillation crystal CY and the capacitance of the capacitive element C.

[0032] In operation S420, the filter circuit 120 generates a filter signal FS according to the phase-locked loop signal PS. In some embodiments, the filter circuit 120 is implemented as a bandpass filter.

[0033] In operation S430, the control circuit 130 adjusts the capacitance value (adjusted capacitance value) of the capacitive element C according to the filter signal FS and the phase-locked loop signal PS. In some embodiments, when the frequency of the oscillation crystal CY shifts due to changes in environmental conditions, the signal energy of the phase-locked loop signal PS input into the mixer 132 is almost not attenuated, but the signal energy of the filter signal FS is greatly attenuated. In this case, the DC signal DC generated by the mixer 132 does not have the maximum DC voltage value, so that the comparison circuit 134 generates a comparison result CR accordingly. Then, the driving circuit 136 can generate a control signal CT1 according to the comparison result CR to adjust the capacitance value of the capacitive element C in the local oscillator 110.

[0034] In operation S440, the local oscillator 110 generates a corrected local oscillation signal OS' according to the oscillation frequency of the oscillation crystal CY and the adjusted capacitance value of the capacitive element C. In some embodiments, the adjusted capacitance value of the capacitive element C can further correct the frequency offset of the phase-locked loop signal PS, so that the frequency divider 114 can perform a frequency division process on the corrected phase-locked loop signal PS' to generate the corrected local oscillation signal OS'.

[0035] In operation S450, the RF signal generating circuit 140 generates a RF signal RS according to the calibrated local oscillation signal OS' and the baseband signal BS. In some embodiments, the mixer 144 may perform a mixing process on the calibrated local oscillation signal OS' and the baseband signal BS to generate a mixed signal MS. The RF circuit 146 may generate a RF signal RS according to the mixed signal MS.

[0036] In summary, the transceiver circuit and self-correction method disclosed in the present invention can correct the frequency offset problem quickly and in real time, and can be applied to different transceiver devices and different oscillator crystals.

[0037] Various functional elements and function blocks are disclosed herein. For those skilled in the art, a function block may be implemented by circuits (whether dedicated circuits or general purpose circuits operating under the control of one or more processors and coded instructions), which generally include transistors or other circuit elements for controlling the operation of electrical circuits corresponding to the functions and operations described herein. It is further understood that the specific structure and interconnection of circuit elements generally may be determined by a compiler, such as a Register Transfer Language (RTL) compiler. The Register Transfer Language compiler operates on a script that is quite similar to assembly language code, compiling the script into a form used to lay out or fabricate the final circuit.

[0038] Although the present disclosure has been disclosed in the above-mentioned embodiments, it is not intended to limit the present disclosure. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be determined by the definition of the attached claims.

[0039]

Explanation of symbols

[0040] 100: Transceiver circuit

[0041] 110: Local Oscillator

[0042] 112: Phase-locked loop circuit

[0043] 114: Frequency divider

[0044] 120: Filter circuit

[0045] 130: Control circuit

[0046] 132: Mixer

[0047] 134: Comparison Circuit

[0048] 136: Driving circuit

[0049] 140: RF signal generation circuit

[0050] 142: Baseband circuit

[0051] 144: Mixer

[0052] 146: RF Circuit

[0053] 400: Self-correction method

[0054] CY: Oscillating crystal

[0055] TF: Target frequency

[0056] C: Capacitive element

[0057] C1-Cn: Capacitor

[0058] T1-Tn: Switch

[0059] CT1: Control signal

[0060] PS: Phase-locked loop signal

[0061] PS': Corrected phase-locked loop signal

[0062] FS: Filter signal

[0063] OS': Corrected local oscillation signal

[0064] BS: Baseband signal

[0065] MS: Mixing signal

[0066] RS: Radio Frequency Signal

[0067] DC: Direct current signal

[0068] DCM: Maximum DC voltage

[0069] CR: Comparison results

[0070] S410, S420, S430, S440, S450: Operation

Claims

1. A transceiver circuit, configured to be coupled to an oscillating crystal, wherein the transceiver circuit comprises: A local oscillator comprising a capacitive element, wherein the local oscillator is configured to generate a phase-locked loop signal based on an oscillation frequency of the oscillation crystal and a capacitance value of the capacitive element; a filter circuit configured to generate a filter signal according to the phase-locked loop signal; a control circuit configured to adjust the capacitance value to an adjusted capacitance value according to the filtered signal and the phase-locked loop signal, wherein the local oscillator is further configured to generate a corrected local oscillation signal according to the oscillation frequency and the adjusted capacitance value; as well as The radio frequency signal generating circuit is configured to generate a radio frequency signal according to the corrected local oscillation signal and the baseband signal. 2 . The transceiver circuit according to claim 1 , wherein the filter circuit is a bandpass filter. The transceiver circuit according to claim 2 , wherein the bandpass filter is implemented by a transmission line.

4. The transceiver circuit according to claim 1, wherein the control circuit comprises: A mixer configured to perform a mixing process on the filtered signal and the phase-locked loop signal to generate a DC signal; a comparison circuit configured to compare the DC signal with a maximum DC voltage to generate a comparison result; and The driving circuit is configured to adjust the capacitance value to the adjusted capacitance value according to the comparison result. 5 . The transceiver circuit according to claim 4 , wherein the capacitive element corresponds to a plurality of capacitance values, the plurality of capacitance values ​​correspond to a plurality of DC voltages respectively, and the maximum DC voltage is a maximum one of the plurality of DC voltages.

6. The transceiver circuit according to claim 1, wherein the local oscillator comprises: a phase-locked loop circuit configured to generate a corrected phase-locked loop signal based on the oscillation frequency and the adjusted capacitance value; and The frequency divider is configured to perform a frequency division procedure on the corrected phase-locked loop signal to generate a corrected local oscillation signal.

7. The transceiver circuit according to claim 1, wherein the radio frequency signal generating circuit comprises: A baseband circuit, configured to generate the baseband signal; a mixer configured to perform a mixing process on the corrected local oscillation signal and the baseband signal to generate a mixed signal; and The radio frequency circuit is configured to generate the radio frequency signal according to the mixing signal. The transceiver circuit according to claim 1 , wherein the capacitive element is a switched capacitor array.

9. A self-calibration method, comprising: Generate a phase-locked loop signal by means of a local oscillator based on an oscillation frequency of an oscillation crystal and a capacitance value of a capacitive element; generating a filtering signal according to the phase-locked loop signal by a filtering circuit; adjusting the capacitance value to an adjusted capacitance value according to the filter signal and the phase-locked loop signal by a control circuit; generating a calibrated local oscillation signal by the local oscillator according to the oscillation frequency and the adjusted capacitance value; as well as The radio frequency signal generating circuit generates a radio frequency signal according to the corrected local oscillation signal and the baseband signal.

10. The self-calibration method according to claim 9, further comprising: Performing a mixing process on the filtered signal and the phase-locked loop signal by a mixer in the control circuit to generate a DC signal; By using a comparison circuit in the control circuit, the DC signal is compared with a maximum DC voltage to generate a comparison result; and The driving circuit in the control circuit adjusts the capacitance value to the adjusted capacitance value according to the comparison result.

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