Third harmonic suppression radio frequency transmitter

Abstract

The invention discloses a third harmonic suppression radio frequency transmitter, which comprises a gain boosting modulator, a third harmonic suppression filter and a power amplifier driver, and is characterized in that the gain boosting modulator is used for performing out-of-band noise suppression on an orthogonal baseband signal to obtain a radio frequency output signal; the third harmonic suppression filter is used for carrying out third harmonic suppression on the radio frequency output signal to obtain a radio frequency harmonic suppression signal, and the power amplifier driver is used for carrying out power amplification on the radio frequency harmonic suppression signal to obtain a radio frequency amplification signal and further sending the radio frequency amplification signal to an external load. The gain boosting modulator is driven by a first local oscillator signal with a first duty ratio, and the third harmonic suppression filter is driven by a second local oscillator signal with a second duty ratio. According to the invention, out-of-band noise generated by a baseband circuit and a mixer in a transmitting link can be effectively suppressed, a third harmonic term at a 3xfLO can be suppressed, a CIM3 nonlinear term is further suppressed, and the method can be widely applied to the technical field of wireless communication.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a third harmonic suppression radio frequency transmitter. Background Art

[0002] Third-order anti-intermodulation (3 rd -Order Counter Inter-modulation, CIM3) is a quantitative indicator of the nonlinearity of the amplifier or TX channel. CIM3 is usually composed of the third harmonic component of the local oscillator signal (3xf LO ) is generated and appears at the output of the modulator. The frequency component of CIM3 is at the local oscillator frequency f LO It is difficult to filter out the spurious spectrum of the transmitted signal, which will eventually cause the spurious spectrum of the transmitted signal to exceed the spectrum mask limit, affecting the receiver frequency band. If the frequency of the transmitted signal is the local oscillator frequency + baseband frequency (i.e. f LO +f BB ), then the frequency component of CIM3 is defined as f LO -3xf BB ; If the frequency component of the transmitted signal is the local oscillator frequency minus the baseband frequency (i.e. f LO -f BB ), then define the CIM3 frequency component as f LO +3xf BB , f LO -3xf BB or LO +3xf BB Appears at the local oscillator frequency f LO In order to suppress CIM3 items, existing technologies usually consume large power or area, which makes it difficult to balance costs. At the same time, the noise of the baseband circuit and mixer of the transmission link cannot be effectively suppressed: 1) A passive LC filter is introduced at the output of the modulator to suppress the third harmonic component, thereby suppressing the CIM3 term. However, the on-chip inductor or transformer usually occupies a large area (1.04mm2), increasing the chip cost. 2) A multi-phase LO circuit is used to modulate the baseband signal and effectively suppress the third harmonic, thereby suppressing the CIM3 term, but at a high power consumption cost (216mW).

[0003] In addition, the prior art only relies on the baseband filter to suppress the out-of-band noise and spurs of the DAC, and the noise of the baseband circuit and the mixer cannot be effectively suppressed. Summary of the invention

[0004] To solve the above technical problems, the object of the present invention is to provide a third harmonic suppression radio frequency transmitter, which can suppress CIM3 nonlinear terms and effectively attenuate out-of-band noise.

[0005] To achieve the above-mentioned purpose, one aspect of an embodiment of the present application proposes a third harmonic suppression RF transmitter, including a gain boost modulator, a third harmonic suppression filter and a power amplifier driver, wherein the first input end of the gain boost modulator is used to receive an orthogonal baseband signal, the output end of the gain boost modulator is connected to the first input end of the third harmonic suppression filter, the output end of the third harmonic suppression filter is connected to the input end of the power amplifier driver, the output end of the power amplifier driver is used to connect an external load, the gain boost modulator is used to suppress out-of-band noise on the orthogonal baseband signal to obtain a RF output signal, the third harmonic suppression filter is used to suppress the third harmonic of the RF output signal to obtain a RF harmonic suppression signal, the power amplifier driver is used to power amplify the RF harmonic suppression signal to obtain a RF amplified signal, and then send the RF amplified signal to the external load, wherein the gain boost modulator is driven by a first local oscillator signal with a first duty cycle, and the third harmonic suppression filter is driven by a second local oscillator signal with a second duty cycle.

[0006] In some embodiments, the gain boost modulator includes an RC filter, one end of the RC filter is used to input the orthogonal baseband signal, the other end of the RC filter is connected to one end of the third harmonic suppression filter, and the RC filter is used to filter the orthogonal baseband signal to achieve preliminary suppression of out-of-band noise.

[0007] In some embodiments, the gain boost modulator also includes a first switch and a transconductance amplifier, one end of the first switch is connected to one end of the RC filter, the other end of the first switch is connected to one end of the transconductance amplifier, the other end of the transconductance amplifier is connected between the third harmonic suppression filter and the power amplifier driver, the first switch is used to up-convert the filtered orthogonal baseband signal according to the first local oscillator signal to obtain a radio frequency input signal, and the transconductance amplifier is used to amplify the radio frequency input signal to obtain a first radio frequency signal.

[0008] In some embodiments, the gain boost modulator also includes a first capacitor and a second switch, one end of the first capacitor is connected between the RC filter and the first switch, the other end of the first capacitor is connected to one end of the second switch, the other end of the second switch is connected between the transconductance amplifier and the third harmonic suppression filter, the first capacitor is used to filter the first RF signal, and the second switch is used to down-convert the filtered first RF signal according to the first local oscillator signal to obtain the RF output signal.

[0009] In some embodiments, the third harmonic suppression filter includes a first switched capacitor network, a second switched capacitor network, and a third switched capacitor network, wherein the first switched capacitor network, the second switched capacitor network, and the third switched capacitor network are all connected to the output end of the gain boost modulator, and the first switched capacitor network, the second switched capacitor network, and the third switched capacitor network are also all connected to the input end of the power amplifier driver, the first switched capacitor network is used to perform a first harmonic suppression on the RF output signal according to the second local oscillator signal, the second switched capacitor network is used to perform a second harmonic suppression on the RF output signal according to the second local oscillator signal, and the third switched capacitor network is used to perform a third harmonic suppression on the RF output signal according to the second local oscillator signal to obtain the RF harmonic suppression signal.

[0010] In some embodiments, the first switch capacitor network, the second switch capacitor network and the third switch capacitor network each include a third switch and a second capacitor, the output end of the gain boost modulator and the input end of the power amplifier driver are both connected to one end of the third switch, and the other end of the third switch is grounded through the second capacitor, wherein each of the third switches is driven by the second local oscillator signal with a second duty cycle.

[0011] In some embodiments, the third harmonic suppression RF transmitter also includes a first signal generating circuit and a second signal generating circuit, the output end of the first signal generating circuit is connected to the second input end of the gain boost modulator, the output end of the second signal generating circuit is connected to the second input end of the third harmonic suppression filter, the first signal generating circuit is used to generate the first local oscillator signal of a first duty cycle and output the first local oscillator signal to the gain boost modulator, and the second signal generating circuit is used to generate the second local oscillator signal of a second duty cycle and output the second local oscillator signal to the third harmonic suppression filter.

[0012] In some embodiments, the first signal generating circuit includes an input buffer, a divide-by-two circuit, a first logic circuit and an output buffer, one end of the input buffer is used to input a differential clock signal, the other end of the input buffer is connected to one end of the divide-by-two circuit, the other end of the divide-by-two circuit is connected to one end of the first logic circuit, the other end of the first logic circuit is connected to one end of the output buffer, and the other end of the output buffer is connected to a second input end of the gain boost modulator, the input buffer is used to amplify the differential clock signal, the divide-by-two circuit is used to obtain a third local oscillator signal with a third duty cycle according to the amplified differential clock signal, the first logic circuit is used to obtain the first local oscillator signal with a first duty cycle according to the third local oscillator signal and the differential clock signal, and the output buffer is used to perform timing control on the first local oscillator signal to obtain a non-overlapping first local oscillator signal, and then output the non-overlapping first local oscillator signal to the gain boost modulator.

[0013] In some embodiments, the second signal generating circuit includes a trigger and a second logic circuit, one end of the trigger is used to input a clock signal, the other end of the trigger is connected to one end of the second logic circuit, the other end of the second logic circuit is connected to the second input end of the third harmonic suppression filter, the trigger and the second logic circuit are used to obtain the second local oscillator signal with a second duty cycle according to the clock signal, and then output the second local oscillator signal to the third harmonic suppression filter.

[0014] In some embodiments, the first duty cycle is 25% and the second duty cycle is 33%.

[0015] The beneficial effects of the present invention are as follows: a third harmonic suppression radio frequency transmitter of the present invention comprises a gain boost modulator, a third harmonic suppression filter and a power amplifier driver, wherein the gain boost modulator is used to suppress out-of-band noise of an input orthogonal baseband signal to obtain a radio frequency output signal, the third harmonic suppression filter is used to suppress the third harmonic of the radio frequency output signal to obtain a radio frequency harmonic suppression signal, the power amplifier driver is used to amplify the radio frequency harmonic suppression signal to obtain a radio frequency amplified signal, and then send the radio frequency amplified signal to an external load, wherein the gain boost modulator is driven by a first local oscillator signal of a first duty cycle, and can effectively suppress out-of-band noise generated by a baseband circuit and a mixer in a transmission link, and the third harmonic suppression filter is driven by a second local oscillator signal of a second duty cycle, and can suppress 3xf LO The third harmonic term at the position is suppressed, thereby suppressing the CIM3 nonlinear term. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution in the embodiments of the present invention, the following introduction is made to the drawings required for use in the embodiments of the present invention. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solution of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A structural block diagram of a third harmonic suppression radio frequency transmitter provided by an embodiment of the present invention; Figure 2 A schematic diagram of a first local oscillator signal with a duty cycle of 25% provided in an embodiment of the present invention; Figure 3 A schematic diagram of a second local oscillator signal with a duty cycle of 33% provided in an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a third harmonic suppression radio frequency transmitter provided by an embodiment of the present invention; Figure 5 A circuit schematic diagram of a first signal generating circuit provided by an embodiment of the present invention; Figure 6 A circuit schematic diagram of a second signal generating circuit provided by an embodiment of the present invention; Figure 7 The embodiment of the present invention provides a radio frequency input signal V i,RF and the RF output signal V o,RF Gain curve graph of the node; Figure 8 The RF output signal V provided by the embodiment of the present invention o,RF Long-distance spectrum gain response diagram at ; Fig. 9 A gain response diagram of a third harmonic suppression radio frequency transmitter at different frequencies provided by an embodiment of the present invention; Fig.10 The simulated CIM3 items and output noise at different frequencies provided by the embodiment of the present invention.

[0018] Reference numeral: R BB , resistance; C BB , capacitor; SW L , first switch; SW R , second switch; SW T , the third switch; C F , the first capacitor; C T , second capacitor; -Gm, transconductance amplifier. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of the present application. They are only examples of devices and methods consistent with some aspects of the embodiments of the present application as detailed in the attached claims.

[0020] It is understood that the terms "first", "second", etc. used in this application can be used to describe various concepts in this article, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another concept. For example, without departing from the scope of the embodiment of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if" and "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determination".

[0021] The terms "at least one", "multiple", "each", "any", etc. used in this application, at least one includes one, two or more, multiple includes two or more, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0022] Before describing the embodiments of the present application in detail, some nouns and terms involved in the embodiments of the present application are first described. The nouns and terms involved in the embodiments of the present application are subject to the following explanations.

[0023] CIM3 (3 rd -OrderCounterInter-modulation), third-order anti-intermodulation: It is a quantitative indicator of nonlinearity and has an important impact on the transmitted signal of the transmitter.

[0024] DAC (Digital to Analog Converter) digital to analog converter.

[0025] BB (Baseband) baseband.

[0026] f LO (Frequency of LO) local oscillator frequency.

[0027] f BB (Frequency of baseband) baseband frequency.

[0028] PA (Power Amplifier) ​​power amplifier.

[0029] PAD (Power Amplifier Driver) power amplifier driver.

[0030] OB (Out-of-Band): Out-of-band.

[0031] HRR3 (3rd-Order Harmonic-Rejection Ratio) third harmonic rejection ratio.

[0032] Third-order anti-intermodulation (3 rd -Order Counter Inter-modulation, CIM3) is a quantitative indicator of the nonlinearity of the amplifier or TX channel. CIM3 is usually composed of the third harmonic component of the local oscillator signal (3xf LO ) is generated and appears at the output of the modulator. The frequency component of CIM3 is at the local oscillator frequency f LO It is difficult to filter out the spurious spectrum of the transmitted signal, which will eventually cause the spurious spectrum of the transmitted signal to exceed the spectrum mask limit, affecting the receiver frequency band. If the frequency of the transmitted signal is the local oscillator frequency + baseband frequency (i.e. f LO +f BB ), then the frequency component of CIM3 is defined as f LO -3xf BB ; If the frequency component of the transmitted signal is the local oscillator frequency minus the baseband frequency (i.e. f LO -f BB ), then define the CIM3 frequency component as f LO +3xf BB , f LO -3xf BB or LO +3xf BB Appears at the local oscillator frequency f LO In order to suppress CIM3 items, existing technologies usually consume large power or area, which makes it difficult to balance costs. At the same time, the noise of the baseband circuit and mixer of the transmission link cannot be effectively suppressed: 1) A passive LC filter is introduced at the output of the modulator to suppress the third harmonic component, thereby suppressing the CIM3 term. However, the on-chip inductor or transformer usually occupies a large area (1.04mm2), increasing the chip cost. 2) A multi-phase LO circuit is used to modulate the baseband signal and effectively suppress the third harmonic, thereby suppressing the CIM3 term, but at a high power consumption cost (216mW).

[0033] In addition, the prior art only relies on the baseband filter to suppress the out-of-band noise and spurs of the DAC, and the noise of the baseband circuit and the mixer cannot be effectively suppressed.

[0034] To this end, an embodiment of the present invention proposes a third harmonic suppression radio frequency transmitter, including a gain boost modulator, a third harmonic suppression filter and a power amplifier driver, wherein the gain boost modulator is used to suppress out-of-band noise on an input orthogonal baseband signal to obtain a radio frequency output signal, the third harmonic suppression filter is used to suppress the third harmonic of the radio frequency output signal to obtain a radio frequency harmonic suppression signal, and the power amplifier driver is used to amplify the radio frequency harmonic suppression signal to obtain a radio frequency amplified signal, and then send the radio frequency amplified signal to an external load, wherein the gain boost modulator is driven by a first local oscillator signal with a first duty cycle, and can effectively suppress the out-of-band noise generated by a baseband circuit and a mixer in a transmission link, and the third harmonic suppression filter is driven by a second local oscillator signal with a second duty cycle, and can suppress 3xf LO The third harmonic term at the position is suppressed, thereby suppressing the CIM3 nonlinear term.

[0035] Reference Figure 1 , Figure 1 A structural block diagram of a third harmonic suppression radio frequency transmitter provided in an embodiment of the present invention. The embodiment of the present invention proposes a third harmonic suppression radio frequency transmitter, including a gain boost modulator, a third harmonic suppression filter and a power amplifier driver. The first input end of the gain boost modulator is used to receive an orthogonal baseband signal, the output end of the gain boost modulator is connected to the first input end of the third harmonic suppression filter, the output end of the third harmonic suppression filter is connected to the input end of the power amplifier driver, the output end of the power amplifier driver is used to connect an external load, the gain boost modulator is used to suppress out-of-band noise on the orthogonal baseband signal to obtain a radio frequency output signal, the third harmonic suppression filter is used to suppress the third harmonic of the radio frequency output signal to obtain a radio frequency harmonic suppression signal, the power amplifier driver is used to power amplify the radio frequency harmonic suppression signal to obtain a radio frequency amplified signal, and then send the radio frequency amplified signal to the external load, wherein the gain boost modulator is driven by a first local oscillator signal with a first duty cycle, and the third harmonic suppression filter is driven by a second local oscillator signal with a second duty cycle.

[0036] As a further optional implementation, the first duty cycle is 25% and the second duty cycle is 33%.

[0037] Specifically, Figure 2 The figure shows the schematic diagram of the first local oscillator signal with a duty cycle of 25%. Figure 3The figure shows a schematic diagram of a second local oscillator signal with a duty cycle of 33%. In the embodiment of the present invention, the quadrature baseband signal input to the gain boost modulator is a typical quadrature BB input (i.e., differential and I / Q signals). The gain boost modulator is driven by the first local oscillator signal with a duty cycle of 25%, and the third harmonic suppression filter is driven by the second local oscillator signal with a duty cycle of 33% to achieve 3xf suppression. LO The third harmonic term at the RF output signal V o,RF It is finally amplified by the PA driver (i.e. power amplifier driver) and transmitted to a 50Ω external load.

[0038] Reference Figure 4 , Figure 4 A structural schematic diagram of a third harmonic suppression RF transmitter provided in an embodiment of the present invention, further as an optional implementation mode, the gain boost modulator includes an RC filter, one end of the RC filter is used to input an orthogonal baseband signal, the other end of the RC filter is connected to one end of the third harmonic suppression filter, and the RC filter is used to filter the orthogonal baseband signal to achieve preliminary suppression of out-of-band noise.

[0039] Specifically, the input quadrature baseband signal is connected by resistor R BB and capacitor C BB The passive RC low-pass filter (i.e. RC filter) composed of the two filters initially suppresses the out-of-band noise output by the digital-to-analog converter DAC and only allows low-frequency signals to pass through.

[0040] Reference Figure 4 As an optional embodiment, the gain boost modulator further includes a first switch SW L and transconductance amplifier -Gm, the first switch SW L One end of the first switch SW is connected to one end of the RC filter. L The other end of the first switch SW is connected to one end of the transconductance amplifier -Gm, and the other end of the transconductance amplifier -Gm is connected between the third harmonic suppression filter and the power amplifier driver. L It is used to up-convert the filtered orthogonal baseband signal according to the first local oscillator signal to obtain a radio frequency input signal, and the transconductance amplifier -Gm is used to amplify the radio frequency input signal to obtain a first radio frequency signal.

[0041] Specifically, the gain boost modulator in the embodiment of the present invention adopts a closed-loop structure to achieve better OB noise (out-of-band noise) suppression. L The transconductance amplifier -Gm forms a feedforward path, and the orthogonal baseband signal after filtering is passed through the first switch SW L Perform up-conversion processing, that is, increase its frequency to the radio frequency (RF) range to obtain the RF input signal V i，RFThe RF input signal V is obtained after up-conversion i，RF Enter the transconductance amplifier-G m In the process, it is converted into a current signal and amplified to obtain a first radio frequency signal, so as to improve the strength of the radio frequency input signal and maintain a certain integrity in subsequent processing.

[0042] Among them, up conversion refers to the process of converting an input signal with a certain frequency into an output signal with a higher frequency.

[0043] Reference Figure 4 As an optional embodiment, the gain boost modulator further includes a first capacitor C F and the second switch SW R , the first capacitor C F One end is connected to the RC filter and the first switch SW L Between, the first capacitor C F The other end of the second switch SW R One end of the second switch SW R The other end is connected between the transconductance amplifier -Gm and the third harmonic suppression filter, and the first capacitor C F The second switch SW is used to filter the first radio frequency signal. R It is used to perform down-conversion processing on the filtered first radio frequency signal according to the first local oscillator signal to obtain a radio frequency output signal.

[0044] Specifically, the feedback path in the closed-loop structure consists of a first capacitor C F and the second switch SW R constitute. Figure 4 The block diagram corresponding to the gain boost modulator in the figure is composed of four layers of the same circuit structure, that is, the gain boost modulator includes four resistors R BB , four capacitors C BB , four first switches SW L , four first capacitors C F and four second switches SW R , where the first switch SW L and the second switch SW R Driven by the first local oscillator signal (LO1, LO2, LO3, LO4) with a duty cycle of 25%. The first capacitor C F is a feedback capacitor, used as a Miller capacitor to provide filtering characteristics, and the second switch SW R The loop is closed by down-converting the first local oscillator signal with a 25% duty cycle.

[0045] Down conversion is the opposite of up conversion, and refers to converting an input signal with a certain frequency into an output signal with a lower frequency.

[0046] It should be noted that the bandpass characteristic is formed by the RC filter and the passive switch mixer in the gain boost modulator, and only signals within a specific frequency range can pass, while signals of other frequencies are suppressed. F For example, the RF input signal V after inverting amplification i，RF and the gain-boosted modulator output RF output signal V o，RF The first capacitor C F The top and bottom plates of the transconductance amplifier are connected to the top and bottom plates of the transconductance amplifier. Therefore, according to the Miller effect, the equivalent capacitance at the input of the transconductance amplifier-Gm increases by approximately a multiple of the loop gain. For this gain-boosted modulator, the RF output signal experiences a high-Q bandpass filter response at both the input and output of the transconductance amplifier-Gm.

[0047] Reference Figure 4 , further as an optional implementation, the third harmonic suppression filter includes a first switched capacitor network, a second switched capacitor network and a third switched capacitor network, the first switched capacitor network, the second switched capacitor network and the third switched capacitor network are all connected to the output end of the gain boost modulator, the first switched capacitor network, the second switched capacitor network and the third switched capacitor network are also all connected to the input end of the power amplifier driver, the first switched capacitor network is used to perform a first harmonic suppression on the RF output signal according to the second local oscillator signal, the second switched capacitor network is used to perform a second harmonic suppression on the RF output signal according to the second local oscillator signal, and the third switched capacitor network is used to perform a third harmonic suppression on the RF output signal according to the second local oscillator signal to obtain a RF harmonic suppression signal.

[0048] Reference Figure 4 As an optional implementation, the first switch capacitor network, the second switch capacitor network and the third switch capacitor network all include a third switch SW T and the second capacitor C T The output of the gain-boosting modulator and the input of the power amplifier driver are connected to the third switch SW T One end of the third switch SW T The other end is connected through the second capacitor C T ground, wherein each third switch SW T Both are driven by a second local oscillator signal with a second duty cycle.

[0049] Specifically, Figure 4The block diagram corresponding to the third harmonic suppression filter in the figure is composed of a first switch capacitor network, a second switch capacitor network and a third switch capacitor network with the same three-layer circuit structure. T The second local oscillator signal (LO A ,LO B ,LO C ) drive. The third harmonic suppression filter technology is mainly based on a multi-channel filter driven by a second local oscillator signal with a 33% duty cycle. The odd harmonic selectivity and suppression can be approximately analyzed by the following formula: ; in, shows the main harmonic components produced by the multi-channel filter, is the odd harmonic order, is the duty cycle of each local oscillator signal, and In the ideal non-overlapping clock case (i.e. ), the attenuation of the third harmonic reaches the maximum. Therefore, the embodiment of the present invention selects a three-way switched capacitor network driven by a second local oscillator signal with a duty cycle of 33% to achieve third harmonic suppression (i.e. ).

[0050] Reference Figure 1 , further as an optional implementation, the third harmonic suppression RF transmitter also includes a first signal generating circuit and a second signal generating circuit, the output end of the first signal generating circuit is connected to the second input end of the gain boost modulator, the output end of the second signal generating circuit is connected to the second input end of the third harmonic suppression filter, the first signal generating circuit is used to generate a first local oscillator signal with a first duty cycle, and output the first local oscillator signal to the gain boost modulator, the second signal generating circuit is used to generate a second local oscillator signal with a second duty cycle, and output the second local oscillator signal to the third harmonic suppression filter.

[0051] Reference Figure 5 , Figure 5This is a circuit schematic diagram of a first signal generating circuit. Further as an optional implementation, the first signal generating circuit includes an input buffer, a divide-by-two circuit, a first logic circuit and an output buffer. One end of the input buffer is used to input a differential clock signal. The other end of the input buffer is connected to one end of the divide-by-two circuit. The other end of the divide-by-two circuit is connected to one end of the first logic circuit. The other end of the first logic circuit is connected to one end of the output buffer. The other end of the output buffer is connected to a second input end of the gain boost modulator. The input buffer is used to amplify the differential clock signal. The divide-by-two circuit is used to obtain a third local oscillator signal with a third duty cycle based on the amplified differential clock signal. The first logic circuit is used to obtain a first local oscillator signal with a first duty cycle based on the third local oscillator signal and the differential clock signal. The output buffer is used to perform timing control on the first local oscillator signal to obtain a non-overlapping first local oscillator signal, and then output the non-overlapping first local oscillator signal to the gain boost modulator.

[0052] It should be noted that the differential clock signals (2LO_P and 2LO_N) operate at 2xf LO frequency.

[0053] Specifically, with 2xf LO The running differential clock signals (2LO_P and 2LO_N) are first amplified by the input buffer and then generated by a divide-by-two circuit to generate a third local oscillator signal (i.e., 50%) with a third duty cycle. Figure 3 LO_I+, LO_I-, LO_Q+, LO_Q- in ). Then, the third local oscillator signal (LO_I+, LO_I-, LO_Q+, LO_Q-) with a duty cycle of 50% and the differential clock signal (2LO_P and 2LO_N) are input into the first logic circuit. The first logic circuit is composed of an AND logic gate. When the input differential clock signal (2LO_P and 2LO_N) and the third local oscillator signal (LO_I+, LO_I-, LO_Q+, LO_Q-) with a duty cycle of 50% are both at a high level, the output of the AND logic gate is a high level, and a first local oscillator signal with a duty cycle of 25% is obtained. Finally, a non-overlapping first local oscillator signal (LO1, LO2, LO3, LO4) with a duty cycle of 25% is generated through the output buffer.

[0054] It is understandable that since the frequency of the differential clock signal (2LO_P and 2LO_N) is twice that of the first local oscillator signal (2xf LO), and both are high at the same time in certain periods of time. Therefore, through the operation of the AND logic gate, a pulse narrower than the original 50% duty cycle third local oscillator signal can be generated, that is, the 25% duty cycle first local oscillator signal. Because the output signal will be high only during the period when the 50% duty cycle third local oscillator signal and the differential clock signal are both valid, and this period is exactly half of the valid period of the original third local oscillator signal.

[0055] Reference Figure 6 , Figure 6 This is a circuit schematic diagram of a second signal generating circuit. Further as an optional implementation, the second signal generating circuit includes a trigger and a second logic circuit, one end of the trigger is used to input a clock signal, the other end of the trigger is connected to one end of the second logic circuit, the other end of the second logic circuit is connected to a second input end of the third harmonic suppression filter, the trigger and the second logic circuit are used to obtain a second local oscillator signal with a second duty cycle according to the clock signal, and then output the second local oscillator signal to the third harmonic suppression filter.

[0056] It should be noted that the clock signal 3LO operates at 3xf LO frequency.

[0057] Specifically, the second signal generation circuit is composed of a traditional D flip-flop (DFF) and a NOR logic gate, which ultimately generates a second local oscillator signal (LO A ,LO B ,LO C ).

[0058] The structure and working principle of a third harmonic suppression radio frequency transmitter according to an embodiment of the present invention are described above. It can be appreciated that, compared with a conventional transmitter, the present invention includes a gain boost modulator, a third harmonic suppression filter, and a power amplifier driver. The first switch and the second switch in the gain boost modulator are driven by a first local oscillator signal (LO1, LO2, LO3, LO4) with a duty cycle of 25%, and the three third switches in the third harmonic suppression filter are driven by a second local oscillator signal (LO1, LO2, LO3, LO4) with a duty cycle of 33%. A ,LO B ,LO C ) drive, which can suppress the third harmonic of the transmitter, thereby optimizing the CIM3 nonlinear term, and attenuating the out-of-band noise generated by the baseband circuit and mixer in the transmission link.

[0059] In order to further verify the reliability of the embodiment of the present invention, the effect of the embodiment of the present invention is further described below in combination with simulation experiment results.

[0060] The simulation results show that Figure 7 The RF input signal Vi,RF and the RF output signal V o,RF The node gain curve provides a high-Q bandpass filter characteristic, for example, it provides 10dB of out-of-band suppression at 80MHz frequency offset, effectively suppressing the out-of-band noise of the digital-to-analog converter DAC, baseband and modulator. Figure 8 The RF output signal V o,RF The long-range spectral gain response at Figure 8 It can be seen that by using the third harmonic suppression filter, the third harmonic suppression ratio (HRR3) reaches 28dB. Fig. 9 The gain response of a third harmonic suppressed RF transmitter at different frequencies is shown. Fig. 9 It can be seen that when the frequency is 2.2GHz, the OB suppression at 80MHz frequency offset is 13.9dB. Fig.10 Shown are the simulated CIM3 terms and output noise at different frequencies, given by Fig.10 It can be seen that when the transmit power is 2.2dBm, the simulation results of the CIM3 term and output noise (at 80MHz frequency offset) at different frequencies are <-47dBc and <-155dBc / Hz respectively.

[0061] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0063] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A third harmonic suppression radio frequency transmitter, characterized in that: It includes a gain boost modulator, a third harmonic suppression filter and a power amplifier driver, wherein the first input end of the gain boost modulator is used to receive an orthogonal baseband signal, the output end of the gain boost modulator is connected to the first input end of the third harmonic suppression filter, the output end of the third harmonic suppression filter is connected to the input end of the power amplifier driver, the output end of the power amplifier driver is used to connect an external load, the gain boost modulator is used to suppress out-of-band noise on the orthogonal baseband signal to obtain a radio frequency output signal, the third harmonic suppression filter is used to suppress the third harmonic of the radio frequency output signal to obtain a radio frequency harmonic suppression signal, the power amplifier driver is used to power amplify the radio frequency harmonic suppression signal to obtain a radio frequency amplified signal, and then send the radio frequency amplified signal to the external load, wherein the gain boost modulator is driven by a first local oscillator signal with a first duty cycle, and the third harmonic suppression filter is driven by a second local oscillator signal with a second duty cycle.

2. A third harmonic suppression radio frequency transmitter according to claim 1, characterized in that: The gain boost modulator includes an RC filter, one end of the RC filter is used to input the orthogonal baseband signal, the other end of the RC filter is connected to one end of the third harmonic suppression filter, and the RC filter is used to filter the orthogonal baseband signal to achieve preliminary suppression of out-of-band noise.

3. A third harmonic suppression radio frequency transmitter according to claim 2, characterized in that: The gain boost modulator also includes a first switch and a transconductance amplifier, one end of the first switch is connected to one end of the RC filter, the other end of the first switch is connected to one end of the transconductance amplifier, the other end of the transconductance amplifier is connected between the third harmonic suppression filter and the power amplifier driver, the first switch is used to up-convert the filtered orthogonal baseband signal according to the first local oscillator signal to obtain a radio frequency input signal, and the transconductance amplifier is used to amplify the radio frequency input signal to obtain a first radio frequency signal.

4. A third harmonic suppression radio frequency transmitter according to claim 3, characterized in that: The gain boost modulator also includes a first capacitor and a second switch, one end of the first capacitor is connected between the RC filter and the first switch, the other end of the first capacitor is connected to one end of the second switch, the other end of the second switch is connected between the transconductance amplifier and the third harmonic suppression filter, the first capacitor is used to filter the first RF signal, and the second switch is used to down-convert the filtered first RF signal according to the first local oscillator signal to obtain the RF output signal.

5. The third harmonic suppression radio frequency transmitter according to claim 1, characterized in that: The third harmonic suppression filter includes a first switched capacitor network, a second switched capacitor network and a third switched capacitor network, wherein the first switched capacitor network, the second switched capacitor network and the third switched capacitor network are all connected to the output end of the gain boost modulator, and the first switched capacitor network, the second switched capacitor network and the third switched capacitor network are also all connected to the input end of the power amplifier driver, the first switched capacitor network is used to perform a first harmonic suppression on the RF output signal according to the second local oscillator signal, the second switched capacitor network is used to perform a second harmonic suppression on the RF output signal according to the second local oscillator signal, and the third switched capacitor network is used to perform a third harmonic suppression on the RF output signal according to the second local oscillator signal to obtain the RF harmonic suppression signal.

6. A third harmonic suppression radio frequency transmitter according to claim 5, characterized in that: The first switch capacitor network, the second switch capacitor network and the third switch capacitor network each include a third switch and a second capacitor, the output end of the gain boost modulator and the input end of the power amplifier driver are both connected to one end of the third switch, and the other end of the third switch is grounded through the second capacitor, wherein each of the third switches is driven by the second local oscillator signal with a second duty cycle.

7. The third harmonic suppression radio frequency transmitter according to claim 1, characterized in that: The third harmonic suppression RF transmitter also includes a first signal generating circuit and a second signal generating circuit, the output end of the first signal generating circuit is connected to the second input end of the gain boost modulator, the output end of the second signal generating circuit is connected to the second input end of the third harmonic suppression filter, the first signal generating circuit is used to generate the first local oscillator signal of a first duty cycle and output the first local oscillator signal to the gain boost modulator, and the second signal generating circuit is used to generate the second local oscillator signal of a second duty cycle and output the second local oscillator signal to the third harmonic suppression filter.

8. A third harmonic suppression radio frequency transmitter according to claim 7, characterized in that: The first signal generating circuit includes an input buffer, a divide-by-two circuit, a first logic circuit and an output buffer. One end of the input buffer is used to input a differential clock signal. The other end of the input buffer is connected to one end of the divide-by-two circuit. The other end of the divide-by-two circuit is connected to one end of the first logic circuit. The other end of the first logic circuit is connected to one end of the output buffer. The other end of the output buffer is connected to the second input end of the gain boost modulator. The input buffer is used to amplify the differential clock signal. The divide-by-two circuit is used to obtain a third local oscillator signal with a third duty cycle according to the amplified differential clock signal. The first logic circuit is used to obtain the first local oscillator signal with a first duty cycle according to the third local oscillator signal and the differential clock signal. The output buffer is used to perform timing control on the first local oscillator signal to obtain a non-overlapping first local oscillator signal, and then output the non-overlapping first local oscillator signal to the gain boost modulator.

9. The third harmonic suppression radio frequency transmitter according to claim 7, characterized in that: The second signal generating circuit includes a trigger and a second logic circuit, one end of the trigger is used to input a clock signal, the other end of the trigger is connected to one end of the second logic circuit, the other end of the second logic circuit is connected to the second input end of the third harmonic suppression filter, the trigger and the second logic circuit are used to obtain the second local oscillator signal with a second duty cycle according to the clock signal, and then output the second local oscillator signal to the third harmonic suppression filter.

10. A third harmonic suppression radio frequency transmitter according to any one of claims 1 to 9, characterized in that: The first duty cycle is 25%, and the second duty cycle is 33%.

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