Passive low noise amplifier based on n-way transformer
By using an N-channel transformer-based passive low-noise amplifier and a differential structure on-chip transformer with switched capacitors, the problems of adjustable frequency bands in wireless receiver filters and large area in traditional passive low-noise amplifiers are solved, achieving high-quality filtering and small-area integration.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI JIAOTONG UNIV
- Filing Date
- 2023-03-14
- Publication Date
- 2026-07-10
AI Technical Summary
Existing wireless receivers have off-chip filters that cannot adjust the frequency band and cannot be integrated into silicon chips. Furthermore, traditional passive low-noise amplifiers are large in area, expensive, and lack linearity.
A passive low-noise amplifier based on an N-channel transformer is adopted, utilizing a differential structure fully switched capacitor on-chip transformer to achieve adjustable center frequency and high-quality filtering, thereby reducing chip area and improving integration.
It achieves passive voltage gain and high-quality filtering, reduces chip area, improves compatibility and integration with advanced processes, and has higher linearity and anti-blocking capability.
Smart Images
Figure CN116232239B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a technology in the field of amplifiers, specifically a passive low-noise amplifier based on an N-channel transformer. Background Technology
[0002] In traditional wireless receiver architectures, after radio frequency (RF) signals are received by the antenna, they need to pass through an off-chip surface acoustic wave (SAW) filter or a bulk acoustic wave (BAW) filter to remove interference from adjacent frequency bands, and then be amplified by a low-noise amplifier for further signal processing. However, these filters are limited by their structure and can only be used in a relatively fixed frequency band, and cannot be adjusted. Therefore, a dedicated filter needs to be designed for each communication standard. Furthermore, these filters cannot be integrated into a silicon chip, are bulky, and expensive.
[0003] To eliminate off-chip SAW or BAW filters in receiver systems and improve integration, some studies have proposed active low-noise amplifiers based on N-channel filtering technology. These amplifiers combine the characteristics of filters and low-noise amplifiers, but their linearity is limited by the active nature of the transconductance amplifier.
[0004] To improve linearity, passive low-noise amplifiers based on on-chip spiral transformers have been proposed. By eliminating active transistors, passive low-noise amplifiers offer higher linearity and better blocking immunity while providing in-band gain. However, this type of passive low-noise amplifier requires a large area due to the use of on-chip spiral transformers, and its size cannot be reduced with the advancement of process nodes, limiting its application. Summary of the Invention
[0005] To address the aforementioned shortcomings of existing technologies, this invention proposes a passive low-noise amplifier based on an N-channel transformer. By using a differential structure with an N-channel on-chip transformer based entirely on switched capacitors, the chip area of the passive low-noise amplifier is significantly reduced, while also exhibiting better compatibility and integration capabilities.
[0006] This invention is achieved through the following technical solution:
[0007] This invention relates to a passive low-noise amplifier based on an N-channel transformer, comprising: an on-chip transformer consisting of at least four parallel switched capacitors and two amplifier feedback loops, wherein: the positive input and negative output terminals of the on-chip transformer are respectively connected to a first amplifier feedback loop, and the negative input and positive output terminals are respectively connected to a second amplifier feedback loop, achieving passive voltage gain by stacking voltages using switched capacitors; the capacitor terminals and switch terminals of the first amplifier feedback loop are respectively connected to the positive input and negative output terminals of the on-chip transformer, and the capacitor terminals and switch terminals of the second amplifier feedback loop are respectively connected to the negative input and positive output terminals of the on-chip transformer, achieving adjustable center frequency and high-quality filtering using multiple capacitors.
[0008] The on-chip transformer has a differential structure, comprising two transformer sub-units consisting of at least four switched capacitors connected in parallel. The forward and reverse inputs of each transformer sub-unit serve as the inputs of a passive low-noise amplifier (LNOA), the output of the first transformer sub-unit serves as the forward output of the LNOA, and the output of the second transformer sub-unit serves as the reverse output of the LNOA. Each transformer sub-unit consists of N sets of switched capacitors connected in parallel as secondary sub-units. Each secondary sub-unit consists of one capacitor and two switches, with the clocks driving the two switches having a 180-degree phase difference. The first capacitor and the first switch are connected in series and positioned between the forward and reverse inputs of the LNOA, and the second switch is positioned between the first capacitor and the forward and reverse outputs of the LNOA. The switches in the N sets of secondary sub-units are respectively connected at a frequency f. LO The N-phase non-overlapping clock drive charges the capacitor until the voltage across the capacitor reaches the average voltage corresponding to the input signal when the switch is closed, after several clock cycles.
[0009] The amplifier feedback loop includes at least four parallel switched-capacitor branches, wherein each branch consists of a capacitor and a switch connected in series, with the other end of the capacitor connected to the input of the passive low-noise amplifier and the other end of the switch connected to the output of the passive low-noise amplifier. Each switch is driven by non-overlapping clock signals of different phases.
[0010] Technical effect
[0011] This invention utilizes an N-channel filtering technique based on switched capacitors to achieve a 3x passive RF voltage gain, constructing an N-channel transformer with a 1:3 conversion ratio, and applying it to a passive low-noise amplifier. Compared to existing pure capacitor-based electronic transformers, which require the phase of the switches to be aligned with the phase of the RF signal to charge the capacitor to its maximum voltage V within the corresponding cycle for voltage stacking amplification, and which require charging within a quarter of the signal cycle, this invention uses an N-channel transformer structure to provide passive voltage gain and high-quality filtering. Furthermore, compared to passive low-noise amplifiers based on on-chip spiral transformers, it occupies less space and has higher integration density. In addition, since this passive low-noise amplifier consists only of switches and capacitors, it has better compatibility and integration capabilities for future low-power, small-size advanced processes. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the passive low-noise amplifier based on an N-channel transformer according to the present invention;
[0013] Figure 2 This is an RLC equivalent model diagram of the N-channel on-chip transformer based on switched capacitors according to the present invention;
[0014] Figure 3 This is a schematic diagram of the working principle of the N-channel on-chip transformer based on switched capacitors of the present invention;
[0015] Figure 4 This is the chip implementation layout of the passive low-noise amplifier based on an N-channel transformer according to the present invention;
[0016] Figure 5 This is a schematic diagram showing the changes in gain and S11 parameters of the passive low-noise amplifier circuit with frequency at different LO frequencies in the embodiment.
[0017] Figure 6 The diagram shows the NF, in-band IIP3, and out-of-band IIP3 of the passive low-noise amplifier circuit at different LO frequencies in the embodiment. Detailed Implementation
[0018] like Figure 1 As shown, this embodiment relates to a passive low-noise amplifier based on an N-channel transformer, including: a differential structure on-chip transformer consisting of four parallel switched capacitors and two amplifier feedback loops, wherein: the positive input terminal and the negative output terminal of the on-chip transformer are respectively connected to the first set of feedback loops, and the negative input terminal and the positive output terminal are respectively connected to the second set of feedback loops.
[0019] like Figure 2 The diagram shown is an RLC equivalent model of the on-chip transformer in this embodiment. This on-chip transformer can be equivalent to two mutually coupled RLC resonant cavities with a coupling coefficient of 1 and a conversion ratio of 3, where: R... T1 ,LT, C T The resistance, inductance, and capacitance of the first equivalent resonant cavity, R T2 ,n 2 L T, C T / n 2 The resistance, inductance, and capacitance equivalent to the second equivalent resonant cavity are calculated using the following formulas for a four-way transformer:
[0020] like Figure 3 As shown in Figure a, the switch has a frequency of f LO Four-phase non-overlapping clock Driven. This example uses the operation of one set of switched capacitors, driven by a clock. as well as Driven by the circuit's time constant being much larger than the switch's on-time, the circuit operates in mixing mode. Therefore, after many clock cycles, the voltage across capacitor C0 will gradually charge to the average voltage corresponding to the input signal when the switch is closed. When the voltage across the capacitor is 2V0 at this point, VRF,INP and VRF,INN... The average voltages of the corresponding signals during phase are +V0 and -V0, such as Figure 3 b and Figure 3 As shown in c. Next, in When the phase is active, another set of switches closes. At this time, at the output terminal, the voltage of the input signal is subtracted from the voltage across the capacitor, making the output voltage equal to 3V0, which is three times the input voltage. The operating principle is the same for other sets of switched capacitors. Therefore, this transformer can operate at radio frequency, providing three times the passive voltage gain. Furthermore, since this circuit has no power gain, the output impedance is amplified to nine times the input impedance, making it a 1:3 N-way transformer.
[0021] A passive low-noise amplifier based on an N-channel transformer was designed using a 55nm CMOS process. The corresponding chip layout is shown below. Figure 4 As shown in the figure, the results indicate that the active area occupied by the chip is only 0.09 mm². 2 .
[0022] Based on specific practical experiments and design using 55nm process technology, the simulation results are as follows: Figure 5 , Figure 6 As shown. The results show that it can perform frequency adjustment in the range of 0.2-1.6 GHz, with a gain of 6.2-8.8 dB, corresponding to S... 11All parameters are less than -10dB, with in-band IIP3 ranging from 5.04 to 14.17dBm, out-of-band IIP3 ranging from 24.52 to 27.16dBm, NF ranging from 2.31 to 3.68dBm, bandwidth of 20MHz, power consumption of 0.7 to 3.1mW, and footprint of 0.09mm². 2 .
[0023] Compared to existing technologies, this device employs an N-way transformer with a 1:3 conversion ratio, achieving a higher conversion ratio and a 3x passive gain. Furthermore, compared to other methods, this passive low-noise amplifier (0.88mm) 2 The area occupied has been greatly reduced.
[0024] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.
Claims
1. A passive low-noise amplifier based on an N-channel transformer, characterized in that, include: An on-chip transformer consisting of at least four parallel switched capacitors and two amplifier feedback loops are provided. The positive input and negative output of the on-chip transformer are connected to the first amplifier feedback loop, and the negative input and positive output are connected to the second amplifier feedback loop. Passive voltage gain is achieved by stacking the voltages using switched capacitors. The capacitor and switch terminals of the first amplifier feedback loop are connected to the positive input and negative output of the on-chip transformer, respectively, and the capacitor and switch terminals of the second amplifier feedback loop are connected to the negative input and positive output of the on-chip transformer, respectively. Adjustable center frequency and high-quality filtering are achieved using multiple capacitors. The on-chip transformer is a differential structure, comprising: two transformer sub-units consisting of at least four switched capacitors connected in parallel, wherein: the positive and negative input terminals of the transformer sub-units serve as the input terminals of a passive low-noise amplifier, the output terminal of the first transformer sub-unit serves as the positive output terminal of the passive low-noise amplifier, and the output terminal of the second transformer sub-unit serves as the negative output terminal of the passive low-noise amplifier. Each transformer subunit consists of N sets of secondary subunits connected in parallel with switched capacitors. Each secondary subunit comprises one capacitor and two switches, with the clocks driving the two switches having a 180-degree phase difference. The first capacitor and the first switch are connected in series and positioned between the inverting and non-inverting inputs of the passive low-noise amplifier. The second switch is positioned between the first capacitor and the inverting and non-inverting outputs of the passive low-noise amplifier. The switches in the N sets of secondary subunits are connected at a frequency of f. LO The N-phase non-overlapping clock drive charges the capacitor until the voltage across the capacitor reaches the average voltage corresponding to the input signal when the switch is closed, after several clock cycles.
2. The passive low-noise amplifier based on N-channel transformers according to claim 1, characterized in that, The amplifier feedback loop includes at least four parallel switched capacitor branches, wherein each branch consists of a capacitor and a switch connected in series, the other end of the capacitor is connected to the input terminal of the passive low noise amplifier, and the other end of the switch is connected to the output terminal of the passive low noise amplifier. Each switch is driven by non-overlapping clock signals of different phases.
3. The passive low-noise amplifier based on N-channel transformers according to claim 1, characterized in that, The on-chip transformer is equivalent to two mutually coupled RLC resonant cavities with a coupling coefficient of 1 and a conversion ratio of 3, where: R T1 , L T, C T The resistance, inductance, and capacitance of the first equivalent resonant cavity, R T2 , n 2 L T, C T / n 2 The resistance, inductance, and capacitance equivalent to the second equivalent resonant cavity, for a four-way transformer, are as follows: .