A six-phase 1 / 3 duty cycle local oscillator transmitter

Abstract

The application belongs to the technical field of wireless communication, and particularly relates to a six-phase 1 / 3 duty cycle local oscillator (LO) transmitter. The transmitter comprises a transistor level active part and a passive network part based on transformer synthesis; wherein the active part is realized by a linear or nonlinear, pure analog or full digital type power amplifier; the passive network part realizes the synthesis of six-phase signals, impedance transformation and conversion from differential to single-ended by using a transformer. Compared with the currently more used 1 / 2 duty cycle quadrature architecture transmitter, the LO signal used in the application has no third harmonic component, the frequency spectrum band out of the generated signal is cleaner, and due to the adoption of the six-phase architecture, the average efficiency under high output power is effectively improved, and due to the larger coverage range on the IQ complex plane, better linearity is achieved through slight clipping under low backoff average power, the efficiency under high output power is effectively improved, and the distortion phenomenon in the demodulation and modulation process of signals is reduced.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to a transmitter. Background Technology

[0002] The rapid development of wireless communication technology has dramatically changed people's lives. Smartphones and tablets supporting 3G / 4G, 3GPP / LTE, mobile communications, WLAN, and WiMAX have become standard equipment in daily life. To meet the demand of a large number of users for high-definition image and video transmission, these communication standards typically employ Orthogonal Frequency Division Multiplexing (OFDM) modulation to improve data transmission rates and spectrum utilization. However, OFDM modulation introduces the Peak Averaging Ratio (PAPR) problem. To ensure linearity at peak power, transmitters typically operate in power backoff mode, resulting in a significant decrease in transmission efficiency. Furthermore, these communication protocols impose stringent requirements on the suppression of out-of-band spurious emissions; for example, LTE requires out-of-band spurious emissions at the base station (BS) to be less than -30 dBm.

[0003] The transmitter is a critical component of the radio frequency (RF) front-end chip and also the most power-consuming part of the entire chip. As CMOS technology shrinks to deep submicron and nanometer dimensions, RF front-end chips have gradually achieved full integration with digital baseband chips, significantly reducing the overall system cost. However, due to limitations in CMOS technology, such as high substrate loss, low power supply voltage, and low breakdown voltage, high-efficiency, high-linearity transmitter integration has remained a research challenge, impacting the battery life and thermal management of the entire communication system.

[0004] Currently, both domestic and international academic and industrial communities have proposed various solutions for high-efficiency, high-linearity transmitters, such as power back-off technology, negative feedback technology, feedforward technology, and predistortion technology. However, most of these research results come at the cost of other performance indicators, such as efficiency, stability, and system complexity. Furthermore, the orthogonal architecture, which has advantages in broadband transmission performance, has a smaller coverage area in the IQ complex plane compared to the polar architecture (POLAR). This necessitates deep clipping of the modulated signal at low back-off average power, resulting in poorer linearity. In contrast, the six-phase 1 / 3 duty cycle local oscillator transmitter can completely eliminate the main out-of-band spurious component—the third harmonic—achieving excellent out-of-band consistency. Moreover, due to its wider coverage in the complex plane, it can achieve better EVM even at low back-off average output power through slight clipping. Furthermore, the six-phase architecture effectively improves the average efficiency at high output power.

[0005] To address the aforementioned problems with transmitters, this invention proposes a six-phase 1 / 3 duty cycle local oscillator transmitter. Compared to orthogonal architectures, the transmitter architecture proposed in this invention effectively solves out-of-band consistency issues, linearity problems for 3GPP / LTE, WLAN, and WiMAX modulated signals under low backoff average power, and improves transmitter efficiency. Summary of the Invention

[0006] The purpose of this invention is to propose a six-phase 1 / 3 duty cycle local oscillator transmitter with good out-of-band consistency, better linearity under low back-off average power, and effective improvement in output efficiency under high output power.

[0007] The six-phase 1 / 3 duty cycle local oscillator transmitter proposed in this invention achieves complete elimination of third-order harmonics by using a 1 / 3 duty cycle local oscillator signal LO, maintaining good out-of-band linearity. Furthermore, by employing a six-phase synthesis method, a wider coverage range can be achieved in the IQ complex plane, resulting in better linearity after slight trimming at low backoff average power. Moreover, due to the six-phase architecture, the average efficiency at high output power is effectively improved.

[0008] The six-phase 1 / 3 duty cycle local oscillator transmitter provided by this invention consists of a transistor-level active section and a passive network section based on transformer synthesis. The active section is implemented using linear or nonlinear, purely analog or fully digital power amplifiers. The passive network section uses transformers to achieve six-phase signal synthesis, impedance transformation, and differential-to-single-ended conversion. The six-phase signal synthesis principle is referenced below. Figure 2 In the left diagram, traditional IQ orthogonal synthesis refers to vector synthesis using LOs with a 90° phase difference, with the output expression being: A cos(wt) + Q sin(wt). Hexa-phase synthesis, on the other hand, uses LOs with a 60° phase difference as carriers for vector synthesis, with the output expression being N1 cos(wt) + N2 cos(wt) + 60°.

[0009] The transmitter architecture proposed in this invention is described in [reference needed]. Figure 1 As shown, it includes: a signal processing module 410, an active section of a power amplifier 420, a passive matching network based on transformer synthesis 430, an output load 440, and a frequency synthesizer 450. The signal processing module 410 is used to clip, limit, filter, and upsample the baseband I / Q quadrature signal, converting it into the N1 and N2 signals required for the six phases. The frequency synthesizer 450 is used to provide a local oscillation signal to the transmitter. The frequency synthesizer 450 generates six LO local oscillator signals with a phase difference of 60° 1 / 3 duty cycle. Based on the baseband signal data, a pair of adjacent 60° LO signals are selected as carriers through the MUX to upconvert the baseband signal.

[0010] Its signal flow is as follows:

[0011] First, the baseband I / Q quadrature signals are clipped, limited, filtered, and upsampled by the signal processing module 410, and then converted into the N1 and N2 signals required for the six phases. The N1 and N2 output signals are then fed into the active section 420 of the power amplifier. Next, the synthesis of the six-phase signals and the differential-to-single-ended conversion are realized at the transformer of the passive matching network 430.

[0012] In this invention, the signal processing module requires special design, and its structure is referenced. Figure 4 It consists of a baseband signal serial-to-parallel conversion module, a zero-order interpolation module, an FIR filter module, and an orthogonal-to-six-phase conversion module for amplitude and phase signals. The phase signal is used to select which pair of adjacent local oscillator signals to use as carriers for vector synthesis, avoiding phase continuity in the IQ complex plane. Logically, in two adjacent regions, the LO corresponding to N2 in the first region is the LO corresponding to N1 in the second region. For example, in the region with an amplitude angle of 0°-60°, N1 corresponds to... LO, N2 corresponds to For the LO, N1 does not correspond in the 60°-120° region. LO is the corresponding LO, N2 corresponds to LO.

[0013] In this invention, the active output of the transmitter is a square wave with a 1 / 3 duty cycle, thereby fundamentally eliminating the third-order harmonic components to obtain a clean out-of-band spectrum, meeting the MASK requirements of wireless communication applications such as 3GPP / LTE, WLAN, and WiMAX / 5G NR.

[0014] In this invention, a six-phase local oscillator (LO) signal synthesis method is used to cover the IQ complex plane, thereby improving the coverage range of the IQ complex plane, making it closer to the coverage range of a polarized POLAR transmitter, and increasing the average efficiency and the number of peak efficiency points under high output power. By clipping the modulation signal, better linearity can be achieved within a smaller power back-off range to meet the linearity requirements of wireless communication applications such as 3GPP / LTE, WLAN, and WiMAX.

[0015] The six-phase 1 / 3 duty cycle local oscillator transmitter proposed in this invention can completely eliminate the main component of out-of-band spurious signals—the third harmonic—thus achieving excellent out-of-band consistency. Furthermore, due to its wider coverage in the IQ complex plane, it can achieve better vector amplitude error (EVM) with slight clipping even at low backoff average output power. At the same time, compared to orthogonal architecture transmitters with the same duty cycle local oscillator signal (LO), the six-phase architecture transmitter of this invention has higher output efficiency.

[0016] The advantages of this invention are that, compared with the commonly used 1 / 2 duty cycle local oscillator quadrature architecture power amplifier, the 1 / 3 duty cycle local oscillator signal LO used has no third-order harmonic components, resulting in a cleaner out-of-band signal. Furthermore, due to the use of a six-phase architecture, the IQ complex plane coverage is larger, and better linearity can be achieved through slight clipping at low back-off average power. It also effectively improves efficiency at high output power and greatly reduces distortion during demodulation and modulation of the signal. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the transmitter structure of the six-phase 1 / 3 duty cycle local oscillator of the present invention.

[0018] Figure 2 EVM for demodulating WIFI 40M signals for six-phase and orthogonal transmitters under IQ complex plane coverage and backoff power.

[0019] Figure 3 The efficiency of a transmitter with a six-phase 1 / 3 duty cycle local oscillator in the IQ plane.

[0020] Figure 4 To adapt to the six-phase architecture signal processing module.

[0021] In the diagram, the following numbers are used: 410 is the signal processing module, 420 is the active part of the power amplifier, 430 is the passive matching network based on transformer synthesis, 440 is the output load, and 450 is the frequency synthesizer. Detailed Implementation

[0022] Figure 1 The present invention presents a transmitter structure for a six-phase 1 / 3 duty cycle local oscillator, comprising: a signal processing module 410, an active power amplifier section 420, a passive matching network based on transformer synthesis 430, an output load 440, and a frequency synthesizer 450. The signal processing module 410 is used for clipping, limiting, filtering, and upsampling the baseband I / Q quadrature signals, converting them into the required N1 and N2 signals for the six phases. The frequency synthesizer 450 provides the transmitter with a local oscillation signal. The signal flow is as follows:

[0023] First, the baseband I / Q quadrature signal is clipped, limited, filtered, upsampled, and converted into the N1 and N2 signals required for the six phases by the signal processing module 410. The N1 and N2 output signals are then fed into the active section 420 of the power amplifier. Then, the synthesis of the six-phase signal and the differential-to-single-ended conversion are realized at the transformer of the passive matching network 430.

[0024] like Figure 2As shown, the six-phase 1 / 3 duty cycle local oscillator transmitter proposed in this invention has a larger coverage area in the IQ complex plane compared with the traditional IQ orthogonal architecture transmitter. When demodulating the modulated signal, it performs a lighter signal clipping under the same back-off power, and has better linearity and smaller vector amplitude error.

[0025] Figure 3 The peak efficiency point distribution diagram of the six-phase 1 / 3 duty cycle local oscillator transmitter proposed in this invention in the IQ complex plane is given. It can be seen from the figure that compared with the 12 peak efficiency points of the traditional IQ orthogonal architecture transmitter, there are 18 more peak efficiency points in the entire plane, indicating that it has higher output efficiency under high output power.

[0026] Table 1 shows the ratios of the amplitudes of each harmonic component to the fundamental frequency of the local oscillator signal used in the transmitter with the six-phase 1 / 3 duty cycle local oscillator proposed in this invention and the traditional IQ quadrature architecture transmitter using a 1 / 2 duty cycle local oscillator. It can be seen that the 1 / 3 duty cycle local oscillator signal used in this invention has an ideal third harmonic component of 0, and the even harmonics will become 0 during differential operation. Therefore, after mixing with the baseband signal, it has a cleaner out-of-band spectrum, which can meet the mask requirements of common communication protocols.

[0027] Therefore, the six-phase 1 / 3 duty cycle local oscillator transmitter proposed in this invention uses a 1 / 3 duty cycle local oscillator signal LO as the carrier and employs vector addition of local oscillator signals with a 60° phase difference, resulting in a clear and concise system structure. Compared to the commonly used IQ orthogonal architecture transmitters that employ a 1 / 2 duty cycle local oscillator signal, it reduces third-order harmonic components, producing a cleaner out-of-band signal that easily meets the requirements of most communication protocols. Furthermore, due to the six-phase architecture, it offers a wider IQ complex plane coverage, a higher peak efficiency point, and higher efficiency at low backoff average power. It can also achieve better linearity through slight clipping, thus meeting the efficiency and linearity requirements of different transmission systems.

[0028] Table 1

[0029]

Claims

1. A transmitter with a six-phase 1 / 3 duty cycle local oscillator, characterized in that, It includes a transistor-level active section and a transformer-based passive network section; wherein, the active section is implemented using a linear or nonlinear, purely analog or fully digital power amplifier; the passive network section uses a transformer to realize the synthesis of six-phase signals, impedance transformation and differential-to-single-ended conversion; the six-phase signal synthesis refers to using the local oscillator signal LO with a phase difference of 60° as the carrier for vector synthesis, and its output expression is N1cos(wt)+N2cos(wt)+60°; specifically including: a signal processing module (410), an active section of the power amplifier (420), a transformer-based passive matching network (430), an output load (440) and a frequency synthesizer (450): wherein, the signal processing module (410) is used to clip, limit, filter and upsample the baseband I / Q quadrature signal, and convert it into the N1 and N2 signals required for six-phase synthesis; the frequency synthesizer (450) is used to provide the transmitter with a local oscillation signal; its signal flow is as follows: First, the baseband I / Q quadrature signal is clipped, limited, filtered, and upsampled by the signal processing module (410) and converted into the N1 and N2 signals required for the six phases. The N1 and N2 output signals are then fed into the active part (420) of the power amplifier. Then, the synthesis, impedance transformation, and differential-to-single-ended conversion of the six-phase signal are realized at the transformer of the passive matching network (430). The active section of the power amplifier outputs a square wave with a 1 / 3 duty cycle, thereby fundamentally eliminating the third-order harmonic components to obtain a clean out-of-band spectrum, meeting the MASK requirements of 3GPP / LTE, WLAN, and WiMAX / 5G NR wireless communication applications. The signal processing module consists of a baseband signal serial-to-parallel conversion module, a zero-order interpolation module, an FIR filter module, and an orthogonal-to-six-phase conversion module for amplitude and phase signals. The phase signal is used to select which set of adjacent local oscillator signals to use as the carrier for vector synthesis. To avoid phase continuity in the IQ complex plane, logically, in two adjacent regions, the LO corresponding to N2 in the first region is the LO corresponding to N1 in the second region. In the region with an amplitude of 0°-60°, N1 corresponds to the LO at φ0°, and N2 corresponds to the LO at φ60°. In the region with an amplitude of 60°-120°, N1 does not correspond to the LO at φ60° but rather to the LO at φ120°, and N2 corresponds to the LO at φ60°.

2. The transmitter with a six-phase 1 / 3 duty cycle local oscillator according to claim 1, characterized in that, The IQ complex plane is covered by a six-phase local oscillator signal LO synthesis method, thereby improving the coverage range of the IQ complex plane and making it closer to the coverage range of polarized transmitters. This increases the average efficiency and the number of peak efficiency points under high output power. With the modulation signal clipped, better linearity is achieved within a smaller power back-off range to meet the linearity requirements of 3GPP / LTE, WLAN, and WiMAX wireless communication applications.

3. The transmitter with a six-phase 1 / 3 duty cycle local oscillator according to claim 1, characterized in that, The main component of out-of-band spurious signals—the third harmonic—is completely eliminated, resulting in excellent out-of-band consistency. Furthermore, due to its wider coverage in the IQ complex plane, it achieves better vector amplitude error through slight clipping at low backoff average output power. At the same time, the six-phase architecture transmitter has higher output efficiency compared to orthogonal architecture transmitters with the same duty cycle local oscillator signal (LO).

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