Local Oscillator, Wireless Communication System and Control Method Thereof

Abstract

The present invention discloses a local oscillator, a wireless communication system and a control method thereof. The local oscillator includes: a look-up table LUT, a matching filter H_F, a noise detector NDET, a power detector PDET, a delay unit DL, a variable gain amplifier GBB, and a digital phase-locked loop; the digital phase-locked loop includes an oscillator, a multi-mode frequency divider MMDIV, a time-to-digital converter TDC, and a digital loop filter DLF. The local oscillator, the wireless communication system and the control method thereof proposed by the present invention can eliminate the frequency pulling of an oscillator (such as a voltage-controlled oscillator VCO or a digitally controlled oscillator DCO), and improve the quality of the LO signal.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and relates to a communication system, and particularly to a local oscillator, a wireless communication system and a control method thereof. Background Art

[0002] Modern wireless communication systems generally consist of three major modules, namely a signal receiving link (RX), a signal transmitting link (TX), and a local oscillator (LO), as Figure 1 shown. The working principle during signal transmission can be described as follows: The digital baseband signal is up-converted with the local oscillator signal by an up-converter (UPMX) to shift the signal spectrum to the radio frequency, and then is sent to the antenna through a power amplifier (PA). When receiving a signal, the signal received from the antenna is amplified by a low-noise amplifier (LNA), and then is down-converted with the local oscillator signal by a down-converter (DNMX) to shift the signal spectrum near the direct current, and then is sent to the digital baseband for processing after passing through a low-pass filter (LPF) and an analog-to-digital converter (ADC).

[0003] A VCO is a voltage-controlled oscillator, and there is a frequency pulling phenomenon in the oscillator. The frequency pulling will cause the output frequency of the oscillator to change, thereby affecting the quality of the transmitted signal. Under the following conditions, there will be frequency pulling: (1) The interference frequency is near the oscillation frequency of the oscillator; (2) The harmonic of the interference frequency is near the oscillation frequency of the oscillator; (3) The interference frequency is near the harmonic of the oscillation frequency of the oscillator. In addition, similar to the voltage-controlled oscillator VCO, the digitally controlled oscillator DCO also has the same frequency pulling problem. The difference between the two is that in the voltage-controlled oscillator VCO, the oscillation frequency is controlled by the input voltage, and in the digitally controlled oscillator DCO, the oscillation frequency is controlled by the input digital code.

[0004] In Figure 1 the system shown, when the signal is transmitted, the local oscillator signal is obtained after frequency division of the voltage-controlled oscillator (VCO) signal, so the second harmonic of the transmitted signal will coincide with the VCO signal frequency. As Figure 2 shown, the radio frequency signal transmitted by the PA will pull the VCO, thereby affecting the quality of the transmitted signal.

[0005] The VCO frequency pulling will bring some negative effects. The negative effects brought by the VCO frequency pulling are discussed in the following two cases.

[0006] The first case is when the transmitted signal is a constant envelope. In this case, when the PA output is established, the PA output power is constant, and the frequency pulling effect of the VCO is to bring a fixed phase shift. Considering that the LO is composed of a phase-locked loop (PLL), the fixed phase shift on the VCO will be corrected by the PLL, but there may be a re-locking of the PLL during this process.

[0007] The second case is that the transmitted signal is a variable envelope signal. At this time, the frequency pulling of the PA on the VCO is a time-varying interference. The PLL in the LO cannot always cancel out the interference of the frequency pulling, resulting in jitter on the LO output clock. After the baseband signal and the LO signal are up-converted, additional noise will be introduced into the RF signal.

[0008] Traditional methods for eliminating VCO frequency pulling include:

[0009] (1) Place the PA and the VCO at two corners of the chip, so that the interference source is as far away from the VCO as possible, making the attenuation on the coupling path greater, the interference energy received by the VCO lower, and the frequency pulling effect weaker. This method is limited by the chip area.

[0010] (2) Separate the power supply and ground of the PA and the VCO in the chip to reduce the interference received by the VCO from the power supply and ground. This method will increase the chip packaging cost.

[0011] (3) Use an 8-shaped inductor for the VCO, so that less energy of the inductor in the signal transmission link is coupled into the VCO inductor. This method requires an 8-shaped inductor with a relatively larger area than the traditional inductor, and the PA inductor is located on the symmetry axis of the 8-shaped inductor to achieve the best effect.

[0012] (4) The frequency pulling of the PA on the VCO is divided into the influence on the amplitude of the VCO and the influence on the instantaneous frequency of the VCO. Add control words for the amplitude and frequency of the VCO to the VCO, and by adjusting the amplitude and frequency control words of the VCO, the influence of the frequency pulling is cancelled. This method generally requires complex calibration to cancel the frequency pulling.

[0013] (5) Use the OSLO scheme, as Figure 3 shown. In this case the 5th-order component of the LO frequency and the 8th-order component of the VCO are at the same frequency. The frequency pulling in this scheme is smaller than Figure 1 the frequency pulling in. This method increases the LO power consumption and design complexity.

[0014] In view of this, there is an urgent need to design a new composition of a wireless communication system today to overcome at least some of the above-mentioned defects existing in the existing composition of the wireless communication system. Summary of the Invention

[0015] The present invention provides a local oscillator, a wireless communication system and its control method, which can eliminate the frequency pulling of the oscillator and improve the quality of the LO signal.

[0016] To solve the above technical problems, according to one aspect of the present invention, the following technical solution is adopted:

[0017] A local oscillator, the local oscillator comprising: a look-up table LUT, a matching filter H_F, a noise detector NDET, a power detector PDET, a delay unit DL, a variable gain amplifier GBB, and a digital phase-locked loop;

[0018] The digital phase-locked loop includes an oscillator, a multi-mode frequency divider MMDIV, a time-to-digital converter TDC, and a digital loop filter DLF;

[0019] The output end of the power detector PDET is connected to the input end of the delay unit DL, and the output end of the delay unit DL is connected to the input end of the variable gain amplifier GBB;

[0020] The output end of the time-to-digital converter TDC is respectively connected to the input end of the noise detector NDET, the input end of the look-up table LUT, and the input end of the digital loop filter DLF;

[0021] The output end of the noise detector NDET is connected to the variable gain amplifier GBB, the output end of the look-up table LUT is connected to the oscillator, and the output end of the digital loop filter DLF is connected to the oscillator;

[0022] The output end of the oscillator is connected to the input end of the multi-mode frequency divider MMDIV, and the output end of the multi-mode frequency divider MMDIV is connected to the input end of the time-to-digital converter TDC.

[0023] As an embodiment of the present invention, the local oscillator further includes an in-phase / quadrature divider IQDIV, and the output end of the oscillator is connected to the input end of the in-phase / quadrature divider IQDIV.

[0024] As an embodiment of the present invention, the look-up table LUT is used to sequentially write input signal values in a write mode at the period of a reference clock signal, and sequentially read out the stored values to the output end at the period of the reference clock signal in a read mode; the noise detector NDET is used to detect the energy of the input noise signal; the power detector PDET is used to detect the power of the input signal; the delay unit DL is used to output the input signal after delaying it for one or more periods at the period of the reference clock.

[0025] As an embodiment of the present invention, the oscillator includes a numerically controlled oscillator DCO or a voltage controlled oscillator VCO.

[0026] According to another aspect of the present invention, the following technical solution is adopted:

[0027] A wireless communication system includes the above local oscillator.

[0028] As an embodiment of the present invention, the wireless communication system further includes a signal transmission link TX, and the signal transmission link TX is connected to the local oscillator.

[0029] As an embodiment of the present invention, the signal transmission link TX includes a digital-to-analog converter DAC, a low-pass filter LPF, and a power amplifier PA; the output end of the digital-to-analog converter DAC is connected to the input end of the low-pass filter LPF, and the output end of the low-pass filter LPF is connected to the input end of the power amplifier PA; the output end of the power amplifier PA is connected to the antenna.

[0030] As an embodiment of the present invention, the local oscillator further includes an in-phase / quadrature divider IQDIV, the output end of the oscillator is connected to the input end of the in-phase / quadrature divider IQDIV, and the output end of the in-phase / quadrature divider IQDIV is connected to the input end of the power amplifier PA.

[0031] According to another aspect of the present invention, the following technical solution is adopted:

[0032] A control method for the above wireless communication system, the control method includes:

[0033] When the power amplifier PA starts to work, set the look-up table LUT to the write mode; write the output data of the time-to-digital converter TDC into the look-up table LUT and save it until the digital phase-locked loop is stable again.

[0034] As an embodiment of the present invention, the control method further includes: every time the power amplifier PA is switched from off to on later, the look-up table LUT is in the read mode, and the matched filter H_F outputs normally to offset the frequency pulling effect brought by the power amplifier PA.

[0035] As an embodiment of the present invention, the control method further includes:

[0036] When the oscillator is not subject to frequency pulling, the noise energy in the output signal of the time-to-digital converter TDC is the thermal noise, quantization noise, and flicker noise in the local oscillator LO;

[0037] When the oscillator is subject to frequency pulling, additional noise due to frequency pulling will be superimposed on the output signal of the time-to-digital converter TDC;

[0038] Adjust the gain of the variable gain amplifier GBB so that the noise in the output signal of the time-to-digital converter TDC is minimized, and at this time, the disturbance due to frequency pulling is also minimized;

[0039] The delay unit DL is used to match the amplitude information in the input baseband signal to the delay of the oscillator being subject to frequency pulling.

[0040] As an implementation manner of the present invention, the local oscillator of the wireless communication system further includes a second delay unit and a second variable gain amplifier. The second delay unit DL and the second variable gain amplifier GBB serve as a second compensation circuit COMP2; the delay unit DL and the variable gain amplifier GBB serve as a first compensation circuit COMP1;

[0041] The control method includes:

[0042] Turn off the power amplifier PA and the first compensation circuit COMP1; at this time, the upmixer UPMX is the main frequency pulling source;

[0043] Adjust the second compensation circuit COMP2 so that the noise detected by the noise detector NDET is minimized. At this time, the frequency pulling caused by the upmixer UPMX is eliminated;

[0044] Start the power amplifier PA and the first compensation circuit COMP1, and adjust the gain of the variable gain amplifier GBB so that the noise in the output signal of the time-to-digital converter TDC reaches the minimum. At this time, the disturbance caused by frequency pulling is also minimized; the delay unit DL is used to match the amplitude information in the input baseband signal to the delay of the oscillator affected by frequency pulling;

[0045] During subsequent normal use, the first compensation circuit COMP1 and the second compensation circuit COMP2 maintain the parameter values that have been adjusted to the optimal values and can work.

[0046] The beneficial effects of the present invention are as follows: The local oscillator, wireless communication system and its control method proposed by the present invention can eliminate the frequency pulling of the oscillator (such as a voltage-controlled oscillator VCO or a numerically controlled oscillator DCO) and improve the quality of the LO signal.

[0047] The present invention adopts the structure of a digital phase-locked loop to eliminate the influence of frequency pulling and has the following advantages:

[0048] (1) Compared with the traditional PFDCP, the TDC outputs a digital signal, so the digital signal output by the TDC can be conveniently stored, read and signal processed.

[0049] (2) The noise energy in the digital signal output by the TDC can be conveniently detected and used as a basis for judging whether the gain of the GBB reaches the optimal value.

[0050] (3) The outputs of the GBB and the DLF are both digital control words and can be directly added.

[0051] (4) Implementing the NDET, LUT, GBB and H_F in the digital domain has a low cost.

[0052] (5) The present invention can simultaneously eliminate the frequency pulling of the PA on the VCO (also applicable to DCO) during the startup process and the working process.

[0053] (6) The present invention can eliminate the frequency pulling of other modules in the transmission link on the VCO (also applicable to DCO). Description of the Drawings

[0054] Figure 1 It is a block diagram of an existing wireless transceiver.

[0055] Figure 2 It is a schematic diagram of oscillator frequency pulling.

[0056] Figure 3 It is a schematic diagram of using the OSLO scheme to eliminate oscillator frequency pulling.

[0057] Figure 4 It is a schematic diagram of the composition of the wireless communication system in an embodiment of the present invention.

[0058] Figure 5 It is a schematic diagram of the composition of the wireless communication system in an embodiment of the present invention (eliminating frequency pulling during the process of the PA turning from off to working).

[0059] Figure 6 It is a disturbance signal flow diagram when the PA is turned on in an embodiment of the present invention.

[0060] Figure 7 It is a signal flow diagram for eliminating the frequency pulling of the oscillator when the PA is turned on in an embodiment of the present invention.

[0061] Figure 8 It is a schematic diagram of the composition of the wireless communication system in an embodiment of the present invention (eliminating frequency pulling of the amplitude modulation signal).

[0062] Figure 9 It is a schematic diagram of the composition of the wireless communication system in an embodiment of the present invention (eliminating frequency pulling of the UPMX and the PA on the oscillator).

[0063] Figure 10 It is a schematic diagram of the working principle of the DCO in an embodiment of the present invention.

[0064] Figure 11 It is a schematic diagram of the working principle of the VCO in an embodiment of the present invention.

[0065] Figure 12 It is a schematic diagram of the working principle of the DCO in an embodiment of the present invention. Detailed Description of the Invention

[0066] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0067] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with the embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0068] The description of this part only focuses on several typical embodiments, and the present invention is not limited to the scope described in the embodiments. The mutual replacement of the same or similar prior art means and some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0069] "Connection" in the specification includes both direct connection and indirect connection.

[0070] The present invention discloses a local oscillator. Figure 4 is a schematic diagram of the composition of a wireless communication system in an embodiment of the present invention; please refer to Figure 4 , the local oscillator includes: a lookup table LUT, a matching filter H_F, a noise detector NDET, a power detector PDET, a delay unit DL, a variable gain amplifier GBB, and a digital phase-locked loop; the digital phase-locked loop includes an oscillator, a multi-mode frequency divider MMDIV, a time-to-digital converter TDC, and a digital loop filter DLF.

[0071] As Figure 4 shown, in an embodiment of the present invention, the oscillator includes a digitally controlled oscillator DCO. Figure 10 is a schematic diagram of the working principle of the DCO in an embodiment of the present invention; as Figure 10 shown, the input signal of the digitally controlled oscillator DCO is a digital signal, and a digital-to-analog conversion circuit DAC is required to convert the digital signal into a control circuit. The digitally controlled oscillator DCO outputs a frequency controlled by the input voltage; of course, the digitally controlled oscillator DCO can also adopt other structural forms, please refer to Figure 12 , and the switch connected to the capacitor array 12 is closed or turned off by digital signal control to achieve the control of the output frequency.

[0072] In another embodiment of the present invention, the oscillator includes a digital-to-analog conversion circuit and a voltage-controlled oscillator VCO. Figure 11 is a schematic diagram of the working principle of the VCO in an embodiment of the present invention; as Figure 11 shown, the input signal of the voltage-controlled oscillator VCO is a control voltage (so there is no digital-to-analog conversion circuit DAC), and the voltage-controlled oscillator VCO outputs a frequency controlled by the input voltage. By adding a digital-to-analog conversion circuit DAC to the voltage-controlled oscillator VCO, it can be regarded as a digitally controlled oscillator DCO, so it is also applicable to the present invention.

[0073] Please continue to refer to Figure 4, the output terminal of the power detector PDET is connected to the input terminal of the delay unit DL, and the output terminal of the delay unit DL is connected to the input terminal of the variable gain amplifier GBB. The output terminal of the time-to-digital converter TDC is respectively connected to the input terminal of the noise detector NDET, the input terminal of the look-up table LUT, and the input terminal of the digital loop filter DLF. The output terminal of the noise detector NDET is connected to the variable gain amplifier GBB, the output terminal of the look-up table LUT is connected to the digitally controlled oscillator DCO, and the output terminal of the digital loop filter DLF is connected to the digitally controlled oscillator DCO. The output terminal of the digitally controlled oscillator DCO is connected to the input terminal of the multi-mode frequency divider MMDIV, and the output terminal of the multi-mode frequency divider MMDIV is connected to the input terminal of the time-to-digital converter TDC.

[0074] In an embodiment of the present invention, the local oscillator further includes an in-phase / quadrature divider IQDIV, and the output terminal of the digitally controlled oscillator DCO is connected to the input terminal of the in-phase / quadrature divider IQDIV. In one embodiment, the function of the in-phase / quadrature divider IQDIV is to divide the input signal frequency by 2 and generate in-phase and quadrature signals (IQ signals) simultaneously.

[0075] In one embodiment, the look-up table LUT is used to sequentially write the input signal values in cycles of the reference clock signal in the write mode, and sequentially read the stored values to the output terminal in cycles of the reference clock signal in the read mode.

[0076] The noise detector NDET is used to detect the energy of the input noise signal; the power detector PDET is used to detect the power of the input signal; the delay unit DL is used to delay the input signal by one or more cycles with the reference clock as the period and then output it.

[0077] The present invention also discloses a wireless communication system, including the above-mentioned local oscillator.

[0078] Figure 4 It is a schematic diagram of the composition of the wireless communication system in an embodiment of the present invention; please refer to Figure 4 , in an embodiment of the present invention, the wireless communication system further includes a signal transmission link TX, and the signal transmission link TX is connected to the local oscillator. In one embodiment, the signal transmission link TX includes a digital-to-analog converter DAC, a low-pass filter LPF, and a power amplifier PA; the output terminal of the digital-to-analog converter DAC is connected to the input terminal of the low-pass filter LPF, the output terminal of the low-pass filter LPF is connected to the input terminal of the power amplifier PA; the output terminal of the power amplifier PA is connected to the antenna.

[0079] In an embodiment of the present invention, the local oscillator further includes an in-phase / quadrature divider IQDIV. The output terminal of the numerically controlled oscillator DCO is connected to the input terminal of the in-phase / quadrature divider IQDIV, and the output terminal of the in-phase / quadrature divider IQDIV is connected to the input terminal of the power amplifier PA.

[0080] The present invention further discloses a control method for the above wireless communication system. The control method includes: when the power amplifier PA starts to work, setting the look-up table LUT to the write mode; writing the output data of the time-to-digital converter TDC into the look-up table LUT and saving it until the digital phase-locked loop becomes stable again.

[0081] In an embodiment, the control method further includes: every time the power amplifier PA is switched from off to on later, the look-up table LUT is in the read mode, and the matched filter H_F outputs normally to cancel the frequency pulling effect brought by the power amplifier PA.

[0082] In an embodiment of the present invention, the control method further includes:

[0083] When the numerically controlled oscillator DCO (in an embodiment, the oscillator can also be a voltage-controlled oscillator VCO) is not affected by frequency pulling, the noise energy in the output signal of the time-to-digital converter TDC is the thermal noise, quantization noise, and flicker noise in the local oscillator LO.

[0084] When the numerically controlled oscillator DCO is affected by frequency pulling, additional noise caused by frequency pulling will be superimposed on the output signal of the time-to-digital converter TDC.

[0085] Adjust the gain of the variable gain amplifier GBB so that the noise in the output signal of the time-to-digital converter TDC is minimized, and at this time, the disturbance caused by frequency pulling is also minimized.

[0086] The delay unit DL is used to match the amplitude information in the input baseband signal through the PA to the delay of the numerically controlled oscillator DCO affected by frequency pulling.

[0087] In an embodiment of the present invention, the local oscillator of the wireless communication system further includes a second delay unit and a second variable gain amplifier. The second delay unit DL and the second variable gain amplifier GBB serve as the second compensation circuit COMP2; the delay unit DL and the variable gain amplifier GBB serve as the first compensation circuit COMP1.

[0088] The control method includes:

[0089] Turn off the power amplifier PA and the first compensation circuit COMP1; at this time, the upconverter UPMX is the main source of frequency pulling.

[0090] Adjust the second compensation circuit COMP2 to minimize the noise detected by NDET. At this time, the frequency pulling caused by UPMX is eliminated;

[0091] Start the power amplifier PA and the first compensation circuit COMP1, and adjust the gain of the variable gain amplifier GBB to minimize the noise in the output signal of the time-to-digital converter TDC. At this time, the disturbance caused by frequency pulling is also minimized; The delay unit DL is used to match the amplitude information in the input baseband signal to the delay of the numerically controlled oscillator DCO due to frequency pulling;

[0092] During subsequent normal use, the first compensation circuit COMP1 and the second compensation circuit COMP2 maintain the parameter values that have been adjusted to the optimal values and can then work.

[0093] In an embodiment of the present invention, the wireless communication system of the present invention can eliminate the frequency pulling caused by the turning on of PA.

[0094] During the process of PA turning from off to working, the VCO (also applicable to DCO) will be subject to frequency pulling. The present invention can eliminate the frequency pulling effect of the process of PA turning from the off state to the working state on the VCO. As Figure 5 shown.

[0095] The working process is described as follows:

[0096] a) Turn off PA and set the H_F output to all 0

[0097] b) Enable PA to make it start working, set the LUT to the write mode, write the TDC output data into the LUT, and save it until the PLL is stable again; then set the LUT to the read mode;

[0098] c) Every time PA is switched from off to working later, the LUT is in the read mode and the H_F outputs normally to offset the frequency pulling effect brought by PA.

[0099] The transfer function of H_F can be obtained by the following analysis method:

[0100] The influence of frequency pulling on the VCO can be expressed as an additive noise, denoted as X; the transfer function of the multi-mode frequency divider (MMDIV) is denoted as 1 / N; the gain of the time-to-digital converter (TDC) is denoted as G_TDC; the transfer function of the digital loop filter (DLF) is denoted as H_LF; the transfer function of the numerically controlled oscillator (DCO) is denoted as H_DCO. Denote the data written into the LUT as Y, and the loop signal flow diagram is as Figure 6 shown, then the following equation holds:

[0101]

[0102] When the LUT is set to the readout mode, the signal flow diagram is as Figure 7 shown. In order to ensure that the LO output clock is not affected by frequency pulling, after the influences of signals X and Y are superimposed, the result at the PLL output is 0, and the following equation holds:

[0103] Y × H_F × H_DCO + X = 0 Equation 2

[0104] From the above two equations, we can obtain:

[0105]

[0106] According to the above method, the frequency pulling on the VCO caused by the PA turn-on can be eliminated.

[0107] If necessary, the frequency pulling on the VCO caused by the PA turn-off can be eliminated in the same way.

[0108] In an embodiment of the present invention, the wireless communication system of the present invention can eliminate the frequency pulling caused by the amplitude modulation signal.

[0109] If the PA output signal is an amplitude modulation signal, the frequency pulling on the VCO (which also applies to the DCO) is related to the PA output power. Using the Figure 8 circuit shown can eliminate the frequency pulling on the VCO when the PA outputs an amplitude modulation signal. Among them, PDET is a power detector that can detect the amplitude component in the baseband signal; NDET is a noise detection circuit that can detect the magnitude of the noise energy in the TDC output signal; GBB is a variable gain amplifier whose gain is controlled by the NDET output.

[0110] The working principle is described as follows: When the VCO is not affected by frequency pulling, the noise energy in the TDC output signal is the thermal noise, quantization noise, and flicker noise in the LO circuit; when the VCO is affected by frequency pulling, additional noise caused by frequency pulling will be superimposed on the TDC output signal. Adjust the gain of GBB to minimize the noise in the TDC output signal. At this time, the perturbation caused by frequency pulling is also minimized. Among them, the DL module is used to match the amplitude information in the input baseband signal to the delay of the voltage-controlled oscillator VCO (or numerically controlled oscillator DCO) affected by frequency pulling.

[0111] In the present invention, the extraction of the PA output envelope information is implemented in the digital baseband part. In some designs, in order to detect the PA output power for PA output power adjustment, an envelope detector is provided at the PA output. In these designs, the output of this envelope detector can be directly utilized. The advantage of this method is that it can save Figure 8 the PKDET module in

[0112] In an embodiment of the present invention, the wireless communication system of the present invention can eliminate the frequency pulling caused by the upmixer.

[0113] Generally speaking, the VCO frequency pulling mainly comes from the PA in the transmission link. After eliminating the influence of the PA by the method described above, the frequency pulling of the upmixer (UPMX) or the power preamplifier (PPA) on the VCO will dominate. The present invention also proposes a method to eliminate the frequency pulling of other modules in the transmission link on the VCO. Taking the elimination of the frequency pulling caused by the UPMX as an example for illustration.

[0114] Figure 9 is a transmitter block diagram that can simultaneously eliminate the frequency pulling effects of the UPMX and the PA on the VCO. The modules that play a canceling role are COMP1 and COMP2. The module COMP1 that eliminates the influence of the PA is already included in the Figure 4 block diagram. COMP2 is the module used to eliminate the influence of the UPMX.

[0115] The specific implementation process is as follows: First, turn off the PA and COMP1. At this time, the UPMX is the main source of frequency pulling. Adjust COMP2 so that the noise detected by NDET is minimized. At this time, the frequency pulling caused by the UPMX is eliminated; then start the PA and COMP1, and according to the operation of eliminating the influence of the PA in the above text, adjust DL and GBB in COMP1 to eliminate the frequency pulling caused by the PA; during subsequent normal use, COMP1 and COMP2 maintain the parameter values that have been adjusted to the optimal values and can work.

[0116] Using the method proposed by the present invention, it is also possible to eliminate the frequency pulling caused by the UPMX during startup. According to the method proposed by the present invention, it is also possible to eliminate the frequency pulling of other modules in the system on the voltage-controlled oscillator VCO (or the numerically controlled oscillator DCO). Different sources of frequency pulling are generally independent and can be linearly superimposed. The method proposed in the present invention can be easily extended to eliminate various sources of frequency pulling of the voltage-controlled oscillator VCO (or the numerically controlled oscillator DCO).

[0117] In summary, the local oscillator, wireless communication system and its control method proposed by the present invention can eliminate the frequency pulling of the oscillator (such as the voltage-controlled oscillator VCO, the numerically controlled oscillator DCO) and improve the quality of the LO signal.

[0118] The present invention adopts the structure of a digital phase-locked loop to eliminate the influence of frequency pulling and has the following advantages:

[0119] (1) Compared with the traditional PFDCP, the TDC outputs a digital signal, so the digital signal output by the TDC can be conveniently saved, read, and signal processed.

[0120] (2) The noise energy in the digital signal output by the TDC can be conveniently detected and used as a basis for determining whether the gain of the GBB reaches the optimum.

[0121] (3) The outputs of the GBB and the DLF are both digital control words and can be directly added.

[0122] (4) Implementing NDET, LUT, GBB, and H_F in the digital domain has low cost.

[0123] (5) The present invention can simultaneously eliminate the frequency pulling of the voltage-controlled oscillator VCO (or the digitally controlled oscillator DCO) by the PA during the startup process and the working process.

[0124] (6) The present invention can eliminate the frequency pulling of other modules in the transmission link on the voltage-controlled oscillator VCO (or the digitally controlled oscillator DCO).

[0125] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0126] The description and application of the present invention here are illustrative and do not intend to limit the scope of the present invention to the above embodiments. The effects or advantages involved in the embodiments may not be reflected in the embodiments due to various factors. The description of the effects or advantages is not used to limit the embodiments. The deformations and changes of the disclosed embodiments here are possible, and the substitutions and equivalent various components of the embodiments are well known to those of ordinary skill in the art. Those skilled in the art should clearly understand that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the present invention. Other deformations and changes can be made to the disclosed embodiments here without departing from the scope and spirit of the present invention.

Claims

1. A local oscillator, characterized in that, The local oscillator includes: a look-up table LUT, a matching filter H_F, a noise detector NDET, a power detector PDET, a delay unit DL, a variable gain amplifier GBB, and a digital phase-locked loop; The digital phase-locked loop includes an oscillator, a multi-mode frequency divider MMDIV, a time-to-digital converter TDC, and a digital loop filter DLF; The input end of the power detector PDET receives a baseband signal, the output end of the power detector PDET is connected to the input end of the delay unit DL, and the output end of the delay unit DL is connected to the input end of the variable gain amplifier GBB; The output end of the time-to-digital converter TDC is respectively connected to the input end of the noise detector NDET, the input end of the look-up table LUT, and the input end of the digital loop filter DLF; The output end of the noise detector NDET is connected to the variable gain amplifier GBB, the output end of the look-up table LUT is connected to the oscillator, and the output end of the digital loop filter DLF is connected to the oscillator; The input end of the matching filter H_F is connected to the output end of the look-up table LUT, and the output end of the matching filter H_F is connected to the digital phase-locked loop; The output end of the oscillator is connected to the input end of the multi-mode frequency divider MMDIV, the output end of the multi-mode frequency divider MMDIV is connected to the first input end of the time-to-digital converter TDC, and the second input end of the time-to-digital converter TDC receives a clock signal.

2. The local oscillator according to claim 1, wherein: The local oscillator further includes an in-phase / quadrature frequency divider IQDIV, and the output end of the oscillator is connected to the input end of the in-phase / quadrature frequency divider IQDIV.

3. The local oscillator according to claim 1, wherein: The look-up table LUT is used to sequentially write input signal values in a cycle of a reference clock signal in the write mode; in the read mode, the stored values are sequentially read out to the output end in a cycle of the reference clock signal; The noise detector NDET is used to detect the energy of the input noise signal; The power detector PDET is used to detect the power of the input signal; The delay unit DL is used to output the input signal after being delayed by one or more cycles with the reference clock as the cycle.

4. The local oscillator according to any one of claims 1 to 3, wherein: The oscillator includes a digitally controlled oscillator DCO or a voltage-controlled oscillator VCO.

5. A wireless communication system, characterized in that, Includes the local oscillator according to any one of claims 1 to 4.

6. The wireless communication system according to claim 5, wherein: The wireless communication system further includes a signal transmission link TX, and the signal transmission link TX is connected to the local oscillator; The signal transmission link TX includes a digital-to-analog converter DAC, a low-pass filter LPF, and a power amplifier PA; the output end of the digital-to-analog converter DAC is connected to the input end of the low-pass filter LPF, the output end of the low-pass filter LPF is connected to the input end of the power amplifier PA; the output end of the power amplifier PA is connected to an antenna.

7. A control method for a wireless communication system, characterized in that, The control method is based on the wireless communication system according to claim 6; the control method includes: When the power amplifier PA starts to work, the look-up table LUT is set to the write mode; the output data of the time-to-digital converter TDC is written into the look-up table LUT and saved, and the data is saved until the digital phase-locked loop is stable again.

8. The control method according to claim 7, characterized in that: The control method further includes: every time the power amplifier PA is switched from off to working later, the look-up table LUT is in the read mode, the matched filter H_F outputs normally, and the frequency pulling effect brought by the power amplifier PA is cancelled.

9. The control method according to claim 7, characterized in that: The control method further includes: When the oscillator is not subject to frequency pulling, the noise energy in the output signal of the time-to-digital converter TDC is the thermal noise, quantization noise and flicker noise in the local oscillator LO; When the oscillator is subject to frequency pulling, additional noise caused by frequency pulling is superimposed on the output signal of the time-to-digital converter TDC; Adjust the gain of the variable gain amplifier GBB so that the noise in the output signal of the time-to-digital converter TDC is minimized, and at this time the disturbance caused by frequency pulling is also minimized; The delay unit DL is used to match the amplitude information in the input baseband signal to the delay of the oscillator being subject to frequency pulling through the power amplifier PA.

10. The control method according to claim 7, characterized in that: The local oscillator of the wireless communication system further includes a second delay unit and a second variable gain amplifier, and the second delay unit and the second variable gain amplifier serve as the second compensation circuit COMP2; the delay unit DL and the variable gain amplifier GBB serve as the first compensation circuit COMP1; The control method includes: Turn off the power amplifier PA and the first compensation circuit COMP1; at this time, the up-conversion mixer UPMX is the main source of frequency pulling; Adjust the second compensation circuit COMP2 so that the noise detected by the noise detector NDET is minimized, and at this time the frequency pulling caused by the up-conversion mixer UPMX is eliminated; Start the power amplifier PA and the first compensation circuit COMP1, adjust the gain of the variable gain amplifier GBB so that the noise in the output signal of the time-to-digital converter TDC is minimized, and at this time the disturbance caused by frequency pulling is also minimized; the delay unit DL is used to match the amplitude information in the input baseband signal to the delay of the oscillator being subject to frequency pulling; During subsequent normal use, the first compensation circuit COMP1 and the second compensation circuit COMP2 maintain the parameter values that have been adjusted to the optimal values and can work.

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