A current mode receiver and receiving method

Abstract

The application discloses a current mode receiver and a receiving method, which comprise a low-noise trans-impedance amplifier, a mixer, a current mode low-pass filter and a current mode ADC; the low-noise trans-impedance amplifier converts a radio frequency power signal into a radio frequency current signal; the mixer down-converts the radio frequency current signal into a baseband current signal; the current mode low-pass filter amplifies and filters the baseband current signal and transmits the baseband current signal to the current mode ADC through a current mirror or a direct coupling mode; and the current mode ADC quantizes the baseband current signal and outputs a digital signal. The current mode receiver provided by the application can effectively contain the current mode ADC through a simple interface circuit, can reduce nonlinear conversion from voltage to current and can realize a high-bandwidth, low-power-consumption, simple-structure and high-linearity receiver.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of receivers, in particular to a current-mode receiver and a receiving method. BACKGROUND

[0002] In the field of receivers, signal processing requires increasingly high speed and high frequency, and the continuous evolution of advanced integrated circuit technology, the current-mode receiver increasingly shows advantages and continuously appears in practical applications. For the traditional voltage-mode receiver, the low-noise amplifier, the mixer, the filter and the analog-to-digital converter in the signal path are all processing voltage signals. In the current-mode receiver, the voltage signal is converted into a current signal after passing through the low-noise trans-impedance amplifier, and then the modules in the signal path are all processing current signals. The current-mode circuit has the following three differences relative to the voltage-mode circuit: first, the most significant difference is that the node impedance in the current-mode circuit is small, because the voltage-mode circuit must set a high-impedance node inside the circuit for voltage-to-current (V-I) conversion. Therefore, the structure of the current-mode circuit is simplified, and the number of components is reduced. Without the introduction of a high-impedance node, the required operating voltage and power consumption are also lower, and at the same time, since the bandwidth is inversely proportional to the product of resistance and capacitance, the circuit operating speed is also improved, and the high-frequency performance is enhanced. In addition, in advanced processes, the reduction of the power supply voltage also reduces the nonlinearity introduced by the large voltage swing of the high-impedance node, and the linearity is improved. Second, another difference between the current-mode circuit and the voltage-mode circuit is that it is easier to implement the most basic signal processing in analog technology, such as addition, subtraction, integration, etc., using current signals than using voltage signals, and the processing speed is also faster. Third, due to the reduced input impedance of CCO-Based ADC and CT-ΣΔ ADC, the use of current-mode sampling reduces the full-swing power of the ADC input, which reduces the requirement for analog baseband linearity.

[0003] As an indispensable module in the receiver, the performance of the ADC gradually becomes the key factor limiting the performance of the entire receiver. CCO-Based ADC and CT-ΣΔ ADC, as two ADC architectures with their own advantages, have received more and more attention.

[0004] For the CCO-Based ADC in Figure 1 , it is more compatible with advanced processes, and has the advantages of high speed, low voltage, low power consumption and self-first-order noise shaping. At the same time, it is different from Figure 2The traditional VCO-Based (voltage-controlled oscillator) ADC needs to convert the input voltage signal into VCO bias current to control the oscillation frequency of the inverter chain, specifically, a transistor is connected to the VCO, and the gate-source voltage VGS is changed by the input voltage Vin, thereby controlling the drain current of the transistor. However, since the transconductance gm of the transistor is not constant with VGS, the VCO is not strictly linear. However, the bias current of the CCO in the CCO-Based ADC is the output current signal of the previous stage, which is theoretically linearly related to the oscillation frequency of the CCO, thus avoiding the nonlinear conversion circuit of V-I in the VCO which requires a large hardware and power consumption, and greatly reducing the need for complex and high-power digital calibration modules for calibration of nonlinearity.

[0005] For the CT-ΣΔ ADC, as the feature size of integrated circuit technology continues to shrink, the delay of the comparator and digital logic also continues to decrease. Moreover, it has anti-aliasing filter and N-order quantization noise shaping function, effectively improving the signal-to-noise ratio. And its input impedance is resistance rather than switched capacitor, so it does not need a high-power input buffer. Therefore, the CT-ΣΔ ADC is also very compatible with advanced technology, and has high signal-to-noise ratio, high speed, low power consumption, various structures, and wide application.

[0006] In addition, the CCO-Based ADC and the CT-ΣΔ ADC are current-mode ADCs, which are highly compatible with current-mode receivers. Because the mainstream voltage-mode ADC needs a transimpedance amplifier to convert the current signal of the analog front end into a voltage signal for processing. This transimpedance amplifier has high power consumption and linearity requirements, especially for large bandwidth receiver design. The introduction of these two types of current-mode ADCs reduces the transimpedance amplifier, and reduces the complexity and design difficulty of the receiver.

[0007] For these technologies, many literatures also introduce very pioneering and meaningful work. For current-mode receiver, document 1 uses a single low noise transconductance amplifier (LNTA) to drive the current-mode passive mixer, and then connects to the low input impedance transimpedance amplifier. The wideband common-gate LNTA with positive and negative feedback improves the gain and noise figure without changing the fixed relationship between the input matching, transconductance gain and output impedance. In addition, the LNTA load impedance boosting technology can suppress the noise amplification caused by the transimpedance amplifier. Document 2 uses LNA (Low Noise Amplifier) + mixer + current-mode Sallen-Key low-pass filter + current amplifier to achieve wide bandwidth and wide gain dynamic range, as well as low noise and high linearity. However, documents 1 and 2 still use traditional voltage-mode ADCs, which require complex and high-power transimpedance amplifiers, making the structure more complex. For the combination of voltage-mode receiver and VCO-Based ADC, document 3 proposes an embedded Sinc2 anti-aliasing filter, which effectively combines the mixer and VCO, simplifies the baseband circuit and the interface circuit of the ADC, and realizes low power consumption, high sampling rate and high signal-to-noise ratio. However, this product samples the voltage-mode analog front-end, and does not use the more advantageous current-mode analog front-end. In terms of improving the linearity of the VCO, document 4 proposes a digital calibration method, which maximizes the dynamic range by taking the input voltage range of the modulator as the center, and automatically changes the center frequency of the VCO when the sampling frequency changes to achieve reconfigurability. Then by injecting three independent PN (Pseudo-Noise) signals, the first-order, second-order and third-order nonlinear coefficients are measured, and then the nonlinear coefficients are calibrated. Although the digital calibration method is more general, and the algorithm can be adjusted according to different needs, digital calibration requires a large number of digital modules, and the algorithm complexity is high, which requires large hardware and power consumption. For current-mode receivers containing CT-ΣΔ ADC, document 5 proposes a current-mode receiver that embeds the filter of the analog front-end into the CT-ΣΔ ADC, reducing the use of transimpedance amplifiers, effectively reducing the structural complexity and reducing the overall power consumption. However, this product uses a semi-digital filter in the feedback loop, which has a certain impact on the stability and performance of the system. Moreover, the coupling degree between the analog front-end and the ADC is high, which is not convenient to change the structure of the CT-ΣΔ ADC to improve the performance.

[0008] References:

[0009] 1 J. Kim and J. Silva-Martinez, "Low-Power, Low-Cost CMOS Direct- Conversion Receiver Front-End for Multistandard Applications," IEEE Journal of Solid- State Circuits, vol. 48, no. 9, 2013, pp. 2090-2103.

[0010] 2 H.-Y. Shih, C.-N. Kuo, W.-H. Chen, T.-Y. Yang, and K.-C. Juang, "A 250MHz 14dB-NF 73dB-Gain 82dB-DR Analog Baseband Chain With Digital-Assisted DC-Offset Calibration for Ultra-Wideband," IEEE Journal of Solid-State Circuits, vol. 45, no. 2, 2010, pp. 338-350.

[0011] 3 A digital-intensive receiver front-end using VCO-based ADC with an embedded 2nd-Order anti-aliasing Sinc filter in 90nm CMOS," 2011 IEEE International Solid-State Circuits Conference, 2011, pp. 176-178.

[0012] 4 Taylor, G, and Galton, I. "A Mostly-Digital Variable-Rate Continuous-Time Delta-Sigma Modulator ADC." IEEE Journal of Solid-State Circuits, vol. 45, no. 12, 2010, pp. 2634-2646.

[0013] 5, S. Subramanian and H. Hashemi, "A Direct Delta-Sigma Receiver with Current-Mode Digitally-Synthesized Frequency-Translated RF Filtering," 2018 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), 2018, pp. 92-95. SUMMARY

[0014] The application aims to solve the technical problems of low receiver bandwidth, high power consumption, complex structure and low linearity, and provides a current-mode receiver and a receiving method.

[0015] The technical problem of the application is solved by the following technical scheme:

[0016] A current-mode receiver comprises a low-noise trans-impedance amplifier, a mixer, a current-mode low-pass filter and a current-mode ADC.

[0017] The low-noise trans-impedance amplifier is used to convert a received radio frequency power signal into a radio frequency current signal.

[0018] The mixer is used to down-convert the radio frequency current signal into a baseband current signal.

[0019] The current-mode low-pass filter is used to amplify and filter the baseband current signal, and transmit the baseband current signal to the current-mode ADC through a current mirror or in a direct coupling manner.

[0020] The current-mode ADC is used to quantize the baseband current signal and output a digital signal.

[0021] In some embodiments, the current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, and the baseband current signal output by the alternating current filter and the direct current generated by the adjustable direct current source are input into the current-controlled oscillator through a current mirror.

[0022] In some embodiments, the current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, and the alternating current output by the alternating current filter and the direct current output by the adjustable direct current source are input into the current-controlled oscillator in a direct coupling manner.

[0023] In some embodiments, the current-mode ADC is a CT-Sigma-Delta ADC, the current-mode low-pass filter is an AC current filter capable of outputting only AC current, the AC current filter outputs a common-mode voltage consistent with the input common-mode voltage of the operational amplifier, and the AC current filter directly couples the baseband current signal to the current-mode CT-Sigma-Delta ADC.

[0024] In some embodiments, in the circuit of the AC current filter, the gain is adjusted by changing the transistor size of the output stage of the AC current filter, which can change the swing of the signal current under different processes, voltages, and temperatures, stabilize the ring-oscillation frequency of the current-controlled oscillator, and enable the ADC to have the same quantization range; and the switching circuit of the transistor can serve as an interface for digital calibration.

[0025] In some embodiments, the adjustable DC current source is in an array form, the adjustable DC current source array can change the size of the DC current according to application requirements, can adjust the size of the common-mode current according to different processes, voltages, and temperatures, and stabilize the center frequency of the current-controlled oscillator; and the switching circuit of the adjustable DC current source array can serve as an interface for digital calibration.

[0026] In some embodiments, the RF current signal output by the low-noise trans-impedance amplifier is transmitted to the mixer through a DC-blocking capacitor.

[0027] In some embodiments, the mixer down-converts the RF current signal output by the low-noise trans-impedance amplifier into a baseband current signal through a high-frequency local oscillator signal, the high-frequency local oscillator signal is provided by a phase-locked loop to generate a double-frequency signal, the double-frequency signal is divided by two by a frequency divider, and the high-frequency local oscillator signal with a 25% duty cycle is converted from a high-frequency local oscillator signal with a 50% duty cycle.

[0028] The application also provides a receiving method of a current-mode receiver, characterized by receiving and quantizing an analog signal by using the current-mode receiver described above, comprising the following steps:

[0029] S1: converting a received RF power signal into an RF current signal by a low-noise trans-impedance amplifier;

[0030] S2: down-converting the RF current signal into a baseband current signal by a mixer;

[0031] S3: amplifying and filtering the baseband current signal by a current-mode low-pass filter, and directly coupling the baseband current signal to a current-mode ADC by a current mirror or in a direct coupling manner;

[0032] S4: quantizing the baseband current signal by a current-mode ADC, and outputting a digital signal.

[0033] The beneficial effects of the present application compared with the prior art include:

[0034] The present application has the following beneficial effects:

[0035] The current mode receiver provided by the present application can effectively contain a current mode ADC through a simple interface circuit, can reduce the nonlinear conversion from voltage to current, and can reduce the complex and high-power transimpedance amplifier, V-I conversion circuit and digital calibration circuit in the prior art, so that a receiver with high bandwidth, low power consumption, simple structure and high linearity is realized.

[0036] In addition, in some embodiments, the following beneficial effects are also achieved:

[0037] The high-frequency local oscillator signal is provided by a phase-locked loop, is divided by two by a frequency divider, and is converted into a 25% duty cycle high-frequency local oscillator signal by a 50% duty cycle, which not only reduces the noise deterioration caused by the overlap of the IQ two paths of the receiver, but also increases the receiver link gain, improves the receiver sensitivity, and reduces the requirement for the linearity of the ADC.

[0038] By changing the transistor size of the output stage of the alternating current filter, the gain can be adjusted, the signal current swing can be changed under different PVT (Process, Voltage, Temperature), the current-controlled oscillator ring vibration frequency remains unchanged, and the ADC has the same quantization range. For the center frequency, an adjustable DC current source is used, that is, the common-mode current is adjusted according to different PVT, so that the center frequency of the current-controlled oscillator is basically unchanged. The adjustable DC current source is in an array form, and the size of the DC current can be changed according to application requirements. In addition, the switch circuit of the adjustable DC current source array can also be used as an interface for digital calibration, which is convenient for further optimization.

[0039] The common-mode current is not required at the input end of the CT-Sigma-Delta ADC, the common-mode voltage output by the alternating current filter is consistent with the input common-mode voltage of the operational amplifier in the ADC, the high-bandwidth alternating current amplifier is effectively combined with the CT-Sigma-Delta ADC, the combination of the two also saves the input resistance of the CT-Sigma-Delta ADC which has a greater impact on linearity, and adjustment of the input resistance is avoided; and the interface circuit can still use the gain adjustment function of the second current mode low-pass filter to increase the resolution of the ADC to optimize the signal-to-noise ratio of the ADC.

[0040] Other beneficial effects of the embodiments of the present application will be further described below. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a schematic diagram of a prior art CCO-based ADC;

[0042] Figure 2 is a schematic diagram of a prior art VCO-based ADC;

[0043] Figure 3 is a schematic diagram of a current-mode receiver structure in an embodiment of the present application;

[0044] Figure 4 is a schematic diagram of a current-mode receiver structure in an embodiment of the present application comprising a CCO-based ADC;

[0045] Figure 5 is a receiving method of a current-mode receiver in an embodiment of the present application;

[0046] Figure 6 is a schematic diagram of a current-mode low-pass filter in an embodiment of the present application;

[0047] Figure 7 is a schematic diagram of an interface between an AC current amplifier and a CCO in an embodiment of the present application;

[0048] Figure 8 is another schematic diagram of an interface between an AC current amplifier and a CCO in an embodiment of the present application;

[0049] Figure 9 is a schematic diagram of an interface between an AC current amplifier and a CT-ΣΔ ADC in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The present application will be further described below with reference to the drawings and in conjunction with preferred embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0051] It should be noted that the terms left, right, up, down, top, bottom, etc. in the embodiments are only relative concepts or are referenced to the normal use state of the product, and should not be considered as limiting.

[0052] A prior art CCO-based ADC schematic diagram is shown in Figure 1 The input current Iin includes common-mode current and AC current, which is injected into N inverters as bias current. After the inverter chain starts oscillating, the outputs of the N inverters are integrated by the oscillation frequency with respect to time, obtaining N phase information, which is converted into N digital codes by N frequency-to-digital converters, and the digital codes are outputted to a full adder to output the quantization result DOUT (digital output) in digital form.

[0053] The prior art VCO-based ADC schematic diagram is shown in Figure 2 The input voltage Vin includes common-mode voltage and alternating voltage, the current obtained through V-I conversion of the transistor is injected into N inverters as bias current, the outputs of the N inverters are integrated by the oscillation frequency after the inverter chain composed of the inverters starts oscillation, N phase information is obtained, N digital codes are obtained through N frequency-to-digital converters, and the digital codes are output through a full adder to output the quantization result DOUT in digital form.

[0054] The embodiment of the present application is summarized as follows:

[0055] The embodiment of the present application proposes a current-mode receiver, and a schematic diagram of the current-mode receiver is shown in Figure 3 The current-mode receiver includes a low-noise trans-impedance amplifier, a mixer, a current-mode low-pass filter and a current-mode ADC.

[0056] The low-noise trans-impedance amplifier is used to convert the received radio frequency power signal into a radio frequency current signal, so that all the subsequent circuit modules process the current signal, so that the advantages of the current-mode receiver are fully utilized; the radio frequency current signal output by the low-noise trans-impedance amplifier is transmitted to the mixer through a DC blocking capacitor.

[0057] The mixer is used to down-convert the radio frequency current signal into a baseband current signal; the mixer down-converts the radio frequency current signal output by the low-noise trans-impedance amplifier into a baseband current signal through a high-frequency local oscillator signal, the high-frequency local oscillator signal is provided by a phase-locked loop to generate a double-frequency signal, the double-frequency signal is divided by two through a frequency divider, and the high-frequency local oscillator signal with a 25% duty cycle is converted from a 50% duty cycle high-frequency local oscillator signal.

[0058] The current-mode low-pass filter is used to amplify and filter the baseband current signal, and the baseband current signal is transmitted to the current-mode ADC through a current mirror or in a direct coupling manner.

[0059] The current-mode ADC is used to quantize the baseband current signal and output a digital signal. The current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an alternating current filter that can only output alternating current, and the baseband current signal output by the alternating current filter and the direct current generated by the adjustable direct current source are input into the current-controlled oscillator through the current mirror. In the circuit of the alternating current filter, the gain is adjusted by changing the size of the transistor of the output stage of the alternating current filter, so that the signal current is changed under different processes, voltages and temperatures, the ring vibration frequency of the current-controlled oscillator is kept stable, and the ADC can have the same quantization range; the switching circuit of the transistor can be used as an interface for digital calibration.

[0060] In another embodiment, the current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an AC current filter capable of outputting only AC current, the AC current filter is connected in parallel with an adjustable DC current source, and the AC current output by the AC current filter and the DC current output by the adjustable DC current source are input into the current-controlled oscillator. The adjustable DC current source is in an array form, the adjustable DC current source array is capable of changing the size of the DC current according to application requirements and adjusting the size of the common-mode current according to different processes, voltages, and temperatures to stabilize the center frequency of the current-controlled oscillator; and the switching circuit of the adjustable DC current source array can serve as an interface for digital calibration.

[0061] In another embodiment, the current-mode ADC is a CT-Sigma-Delta ADC, the current-mode low-pass filter is an AC current filter capable of outputting only AC current, the AC current filter outputs a common-mode voltage consistent with the input common-mode voltage of the operational amplifier, and the AC current filter directly couples the baseband current signal to the current-mode CT-Sigma-Delta ADC.

[0062] As shown in Figure 5 The present application also provides a receiving method of a current-mode receiver, which comprises the following steps:

[0063] S1: converting a received radio frequency power signal into a radio frequency current signal through a low-noise transconductance amplifier;

[0064] S2: down-converting the radio frequency current signal into a baseband current signal through a mixer;

[0065] S3: amplifying and filtering the baseband current signal through a current-mode low-pass filter and directly coupling the baseband current signal to a current-mode ADC through a current mirror or in a direct coupling manner;

[0066] S4: quantizing the baseband current signal through the current-mode ADC and outputting a digital signal.

[0067] Embodiment:

[0068] As shown in Figure 4As shown, the embodiment provides a current mode receiver comprising a CCO-Based ADC (Current Control Oscillator-based Analog-to-Digital Converter), whose signal path includes: a low noise trans-impedance amplifier (LNTA), a mixer (MIXER), a current mode low pass filter (current mode LPF), a current mode ADC (Analog-to-Digital Converter), a phase-locked loop (PLL) providing a high-frequency local oscillator signal, and a divider (Divider). First, the signal is input through the low noise trans-impedance amplifier, which converts the radio frequency power signal received by the antenna into a radio frequency current signal, so that all subsequent circuit modules process current signals, so that the advantages of the current mode receiver are fully utilized; the radio frequency current signal is transmitted to the mixer through the DC blocking capacitor (Cdc) in Figure 4 , the radio frequency current signal output by the low noise trans-impedance amplifier is down-converted into a baseband current signal by the high-frequency local oscillator signal, the high-frequency local oscillator signal provides a double-frequency signal by the phase-locked loop (Phase Lock Loop, PLL), is divided by two by the divider (Divider), and is converted into a 25% duty cycle high-frequency local oscillator signal by a 50% duty cycle. Not only does it reduce the noise deterioration caused by the overlap of the IQ two-way of the receiver, but it also increases the receiver link gain, improves the receiver sensitivity, and reduces the requirement for ADC linearity; the subsequent current mode low pass filter is essentially a variable gain current amplifier with a pole, as shown in Figure 6 , the current mode low pass filter is a variable gain current amplifier, so it mainly has two functions:

[0069] 1. Amplify the current signal, increase the resolution of the ADC, reduce the offset (offset) requirement of the comparator in the ADC, reduce the quantization noise, and improve the signal-to-noise ratio of the ADC;

[0070] 2. Filter out out-of-band interference to prevent out-of-band signals from aliasing into the band to cause large harmonics and deteriorate linearity.

[0071] Finally, the baseband current signal output by the current mode low pass filter is injected into the current mode ADC through a current mirror or direct coupling, and the digital signal is obtained by quantizing the baseband current signal by the current mode ADC.

[0072] As shown in Figure 6As shown, the baseband current signal is inputted by INN and INP, and is converted from current signal to voltage signal by the complementary current mirror input stage, the current mirror mirror tube is M1 / M5 / M4 / M8, at the same time, the voltage amplifier A, M1 / M2 / M3 / M4 constitute a negative feedback loop, vcm is the negative input terminal of the voltage amplifier, which ensures that the input potential of the current amplifier is stable near the common mode level of vcm, Rc and Cc are Miller capacitor resistors, which improve the loop stability, Rz and Cz are neutralizing capacitor resistors, which introduce additional zero and pole, and expand the bandwidth of the current amplifier. The current amplifier is in a symmetrical form, that is, a fully differential amplifier, and the output is OUTN and OUTP, which can effectively suppress secondary nonlinearity, suppress common mode noise, etc. Vp and vn are the bias levels of the common gate tubes M3 and M7, and VSS is the ground or power supply.

[0073] The key of the current-mode receiver in the embodiment of the present application is the interface between the current-mode low-pass filter and the current-mode ADC. For the current-controlled oscillator (CCO) based ADC, the bias current of the CCO is composed of a DC current and an AC current. It is noted that Figure 1 The bias current in the middle is injected from the top of the inverter, but the bias current can also be injected from the bottom.

[0074] The interface circuit proposed in the embodiment of the present application is to input the baseband current signal outputted by the AC current filter and the DC current generated by the adjustable DC current source into the current-controlled oscillator through the current mirror, as shown in Figure 7 As shown, as a differential structure, Figure 7 The current amplifier in the middle only uses half of the circuit as an example, and the actual current is in a differential form, that is, the other half of the circuit is also used with Figure 7 The circuits are in a mirror relationship. Figure 7 The AC current AC outputted by the current amplifier in the middle and the DC current (DC) which can be tuned are jointly copied and injected into N current-controlled oscillators through the current mirror. This application is suitable for the case where the voltage swing of the current-controlled oscillator changes greatly, because the change of the voltage swing of the current-controlled oscillator may be hundreds of millivolts in size with the change of the signal current.

[0075] Another proposed structure is that an AC current filter and a parallel adjustable DC current source are used, the AC current generated by the former and the DC current generated by the latter are jointly injected into the current-controlled oscillator. As shown in Figure 8As shown, the AC output current of the current amplifier, along with an adjustable DC current, is directly injected into N current-controlled oscillators. This structure reduces the use of current mirrors and is suitable for situations where the voltage swing of the current-controlled oscillators varies little, because the current-controlled oscillators are directly connected to the output of the current amplifier. The common-mode level of the amplifier's output cannot vary significantly, otherwise performance will be severely affected. However, the current amplifier at the interface front end can be used as follows... Figure 6 The complementary structure realizes the current mirror, which has higher linearity and relatively larger output swing compared with ordinary current mirror.

[0076] Because the oscillation frequency range and center frequency of a current-controlled oscillator vary significantly depending on different processes, voltages, and temperatures (PVT), tuning is required, i.e., changing the transistor size in the output stage of the AC current filter. The oscillation frequency range is directly proportional to the swing of the signal current. Therefore, an adjustable-gain current amplifier is used, such as... Figure 6 The transistors on the left and right sides of the middle, Figure 6 The ADC uses a 4-bit transistor for adjustment, but the number of transistors can be increased or decreased depending on the application to meet different precision and application requirements. Adjusting the gain using this method allows for changes in the signal current swing under different PVT conditions, while maintaining a constant current-controlled oscillator ring frequency, ensuring the ADC has a consistent quantization range. For the center frequency, a specific method is used... Figure 7 , Figure 8 The adjustable DC current source in this example adjusts the common-mode current based on different PVT values, thereby keeping the center frequency of the current-controlled oscillator essentially constant. Similarly, this adjustable DC current source is in array form, allowing the DC current magnitude to be changed according to application requirements. Furthermore, the switching circuitry of these adjustable DC current source arrays can also serve as an interface for digital calibration, facilitating further optimization.

[0077] For CT-ΣΔADC, one proposed interface structure involves subtracting the feedback current I_DAC of the DAC (Digital-to-Analog Converter) from the output current Iin of the AC current filter, and directly injecting the resulting residual current I_RES into the CT-ΣΔADC, as follows: Figure 9Because the input end of the CT-S ADC does not need common-mode current, only the common-mode voltage of the alternating current filter output needs to be consistent with the input common-mode voltage (VCM) of the operational amplifier in the ADC, so that the high-bandwidth alternating current amplifier is effectively combined with the CT-S ADC. At the same time, the combination of the two also saves the input resistance of the CT-S ADC which has a greater impact on linearity, avoiding the adjustment of the input resistance. Similarly, the interface circuit can still use the gain adjustment function of the alternating current amplifier to increase the resolution of the ADC to optimize the signal-to-noise ratio of the ADC.

[0078] Figure 9 The alternating current filter outputs alternating current as the input current Iin of the CT-S ADC, and the residual error circuit I_RES obtained by subtracting the feedback circuit I_DAC of the DAC from the alternating current becomes the integral current of the analog integrator (the operational amplifier + cross-capacitance in the figure), and the integral voltage is obtained by the quantizer to obtain the quantization result DOUT in digital form, and at the same time, the quantization result also drives the DAC to generate I_DAC. Note that, Figure 9 Only the first-order filtered CT-S ADC is shown in the figure, and there are many CT-S ADC structures in practice, and the figure focuses on the interface circuit without input resistance and direct coupling.

[0079] In summary, the current-mode receiver architecture containing the current-mode ADC, after the low-noise transconductance amplifier realizes the output of the current signal, then through the mixer to down-convert the signal to the baseband signal, and through the amplification and filtering of the current-mode low-pass filter, the signal is transmitted to the current-mode ADC for quantization by using a simple current mirror or a direct coupling method, and the center frequency and the oscillation frequency range of the current-controlled oscillator are adjusted efficiently. That is, the current-mode receiver effectively contains the current-mode ADC through the simple interface circuit, reduces the high complexity and high power consumption of the transimpedance amplifier, the V-I conversion circuit and the digital calibration circuit in the prior art, and finally realizes a high-bandwidth, low-power, simple-structure and high-linearity receiver.

[0080] The above is a further detailed description of the present application in combination with a specific preferred embodiment, and the specific implementation of the present application cannot be limited to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of equivalent substitutions or obvious modifications can be made, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present application.

Claims

1. A current-mode receiver, characterized by: The current-mode receiver comprises a low-noise trans-impedance amplifier, a mixer, a current-mode low-pass filter and a current-mode ADC. The low-noise trans-impedance amplifier is used to convert a received radio frequency power signal into a radio frequency current signal. The mixer is used to down-convert the radio frequency current signal into a baseband current signal. The current-mode low-pass filter is used to amplify and filter the baseband current signal and transmit the baseband current signal to the current-mode ADC through a current mirror or in a direct coupling manner. The current-mode ADC is used to quantize the baseband current signal and output a digital signal. The current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, and the baseband current signal output by the alternating current filter and a direct current generated by an adjustable direct current source are input into the current-controlled oscillator through a current mirror. The current-mode ADC is an ADC with a current-controlled oscillator, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, and the alternating current output by the alternating current filter and the direct current output by the adjustable direct current source are directly coupled to be input into the current-controlled oscillator. The current-mode ADC is a CT-ΣΔ ADC, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, the common-mode voltage output by the alternating current filter is consistent with the input common-mode voltage of the operational amplifier, and the alternating current filter directly couples the baseband current signal to the current-mode CT-ΣΔ ADC.

2. The current mode receiver of claim 1, characterized in that: In the circuit of the alternating current filter, the gain is adjusted by changing the transistor size of the output stage of the alternating current filter, so that the swing of the signal current is changed under different processes, voltages and temperatures, the ring vibration frequency of the current-controlled oscillator is kept stable, and the ADC can have the same quantization range; the switching circuit of the transistor can serve as an interface for digital calibration.

3. The current mode receiver of claim 1, wherein: The adjustable direct current source is in an array form, the adjustable direct current source array can change the size of the direct current according to application requirements, can adjust the size of the common-mode current according to different processes, voltages and temperatures, and stabilize the center frequency of the current-controlled oscillator; the switching circuit of the adjustable direct current source array can serve as an interface for digital calibration.

4. The current mode receiver of claim 1, wherein: The radio frequency current signal output by the low-noise trans-impedance amplifier is transmitted to the mixer through a direct-current isolation capacitor.

5. The current mode receiver of claim 1, wherein: The mixer down-converts the radio frequency current signal output by the low-noise trans-impedance amplifier into a baseband current signal through a high-frequency local oscillator signal, the high-frequency local oscillator signal is a double-frequency signal provided by a phase-locked loop, is halved by a frequency divider, and is converted into a high-frequency local oscillator signal with a 25% duty cycle from a 50% duty cycle.

6. A receiving method of a current mode receiver, characterized by, The current-mode receiver is used to receive and quantize an analog signal, and comprises the following steps: S1: converting a received radio frequency power signal into a radio frequency current signal through a low-noise trans-impedance amplifier; S2: down-converting the radio frequency current signal into a baseband current signal through a mixer; S3: amplifying and filtering the baseband current signal through a current-mode low-pass filter, and transmitting the baseband current signal to a current-mode ADC through a current mirror or in a direct coupling manner; S4: quantizing the baseband current signal through the current-mode ADC, and outputting a digital signal.

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