CN115765773A - Current mode receiver and receiving method - Google Patents

Abstract

The invention discloses a current mode receiver and a receiving method, comprising a low noise transconductance amplifier, a frequency mixer, a current mode low-pass filter and a current mode ADC; the low-noise transconductance amplifier converts the 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; the current-mode ADC quantizes the baseband current signal and outputs a digital signal. According to the current mode receiver provided by the invention, through the arrangement of the low-noise transconductance amplifier, the frequency mixer, the current mode low-pass filter, the current mode ADC and the like, the current mode receiver can effectively comprise the current mode ADC through a simple interface circuit, the nonlinear conversion from voltage to current can be reduced, and the receiver with high bandwidth, low power consumption, simple structure and high linearity is realized.

Description

Current mode receiver and receiving method

Technical Field

The present invention relates to the field of receivers, and in particular, to a current mode receiver and a receiving method.

Background

In the receiver field, signal processing requires higher speed and higher frequency, and the advanced process of integrated circuit is continuously evolving, and current mode receivers increasingly exhibit advantages and are continuously appearing in practical applications. For a conventional voltage mode receiver, voltage signals are processed by low noise amplifiers, mixers, filters, analog-to-digital converters and other modules in a signal path of the conventional voltage mode receiver. In the current mode receiver, a voltage signal is converted into a current signal after passing through a low-noise transconductance amplifier, and then the current signal is processed by all modules in a signal path. The current mode differs from the voltage mode circuit by three differences: one, the biggest 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 to perform voltage-to-current (V-I) conversion. Therefore, the structure of the current mode circuit is simplified, and the number of elements is reduced. High-impedance nodes are not required to be introduced, the required working voltage and power consumption are low, and meanwhile, the bandwidth is inversely proportional to the product of the resistance and the capacitance, so that the working speed of the circuit is improved, and the high-frequency performance is enhanced; in addition, in the advanced process, the reduction of the power supply voltage can reduce the nonlinearity caused by the large voltage swing of the high-impedance node, and the linearity is improved. The current mode circuit is different from the voltage mode circuit in the most basic signal processing in the analog technology, such as addition, subtraction, integration and the like, and the current signal is easier to realize and the processing speed is higher than the voltage signal; thirdly, because the input impedance of high-speed ADCs such as CCO-based ADCs, CT-sigma delta ADCs and the like is reduced, the full swing power of the input of the ADC is reduced by adopting current mode sampling, and the requirement on the linearity of an analog baseband is reduced.

The ADC is an indispensable module in the receiver, and its performance gradually becomes a key factor limiting the performance of the whole receiver. The CCO-base ADC and the CT- Σ Δ ADC have attracted more and more attention as two advantageous ADC architectures.

For the CCO-based adc in fig. 1, it is more compatible with advanced technology, and has the advantages of high speed, low voltage, low power consumption, and self-contained first-order noise shaping. Meanwhile, it is different from the conventional VCO-Based (voltage-controlled oscillator) ADC in fig. 2 in that an input voltage signal needs to be converted into a VCO bias current to control the oscillation frequency of an inverter chain, specifically, a transistor is connected to the VCO, and a gate-source voltage VGS is changed by the input voltage Vin, so as to control the drain current of the transistor. But the VCO is not strictly linear since the transconductance gm of the transistors is not constant with VGS. However, the bias current of the CCO in the CCO-based adc is the output current signal of the previous stage, and the signal theoretically has a linear relationship with the oscillation frequency of the CCO, so that a V-I nonlinear conversion circuit requiring large hardware and power consumption overhead in the VCO is avoided, and the requirement of a complex and high-power-consumption digital calibration module used for calibrating nonlinearity is greatly reduced.

As the feature size of the integrated circuit process is reduced, the delay of the comparator and the digital logic of the CT- Σ Δ ADC is also reduced. Moreover, the self-contained anti-aliasing filter and N-order quantization noise shaping function effectively improves the signal-to-noise ratio. And the input impedance is a resistor instead of a switched capacitor, so that a high-power-consumption input buffer is not needed. Therefore, the CT-sigma delta ADC is also very compatible with an advanced process, and has the advantages of high signal-to-noise ratio, high speed, low power consumption, various structures and wide application.

In addition, the CCO-based ADC and the CT- Σ Δ ADC are highly matched with a current-mode receiver as a current-mode ADC. Because the mainstream voltage mode ADC needs a transimpedance amplifier, the current signal of the analog front end is converted into a voltage signal for processing. The transimpedance amplifier has high power consumption and linearity requirements, especially for large bandwidth receiver designs. And due to the introduction of the two types of current mode ADCs, trans-impedance amplifiers are reduced, and the complexity and the design difficulty of a receiver are reduced.

For these techniques, many documents also describe work that is very pioneering and meaningful for reference. For a current-mode receiver, a single Low Noise Transconductance Amplifier (LNTA) in document 1 drives a current-mode passive mixer, which is then connected to a transimpedance amplifier with low input impedance. The broadband common-gate LNTA with positive and negative feedback improves gain and noise coefficient under the condition of not changing the fixed relation among input matching, transconductance gain and output impedance, and in addition, the LNTA load impedance lifting technology can inhibit noise amplification caused by a transimpedance amplifier. Document 2 adopts an LNA (Low Noise Amplifier), a mixer, a current modulo Sallen-Key Low-pass filter, and a current Amplifier, and realizes a wide bandwidth and a wide gain dynamic range, as well as Low Noise and high linearity. However, documents 1 and 2 still sample the conventional voltage-mode ADC, and require a complicated transimpedance amplifier with high power consumption, which makes the structure complicated. For the combination of the voltage mode receiver and the VCO-based ADC, document 3 proposes an embedded Sinc2 anti-aliasing filter, which effectively combines the mixer and the 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. But the analog front end of the product sampling voltage mode does not use the analog front end of the more advantageous current mode. In terms of improving the linearity of the VCO, document 4 proposes a method of digital calibration, that is, maximizing the dynamic range centering on the modulator input voltage range, and automatically changing the center frequency of the VCO when the sampling frequency is changed to realize reconfigurability. First, second and third order nonlinear coefficients are measured by injecting three independent PN (Pseudo-Noise) signals, and then calibrated using the nonlinear coefficients. Although the digital calibration mode is general and the algorithm can be adjusted according to different requirements, the digital calibration needs a large number of digital modules, the algorithm complexity is high, and the hardware and power consumption overhead is high. For a current mode receiver including a CT- Σ Δ ADC, document 5 proposes a current mode receiver in which a filter of an analog front end is embedded in the CT- Σ Δ ADC, which reduces the use of a transimpedance amplifier, effectively reduces the structural complexity, and reduces the overall power consumption. But the product uses a half digital filter in a feedback loop, and has certain influence on the stability and the performance of the system. And the coupling degree of the analog front end and the ADC is high, so that the structure of the CT-sigma delta ADC is not convenient to change to improve the performance.

Reference documents:

1,J.Kim and J.Silva-Martinez,“Low-Power,Low-Cost CMOS Direct-Conversion Receiver Front-End for Multistandard Applications,”IEEE Journal ofSolid-State Circuits,vol.48,no.9,2013,pp.2090-2103.

2,H.-Y.Shih,C.-N.Kuo,W.-H.Chen,T.-Y.Yang and K.-C.Juang,“A250MHz 14dB-NF 73dB-Gain 82dB-DRAnalog 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.

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

4,Taylor,G,and Galton,I.“A Mostly-Digital Variable-Rate Continuous-Time Delta-SigmaModulatorADC.”IEEE Journal ofSolid-State Circuits,vol.45,no.12,2010,pp.2634–2646.

5,S.Subramanian and H.Hashemi,"A DirectΔΣReceiver with Current-Mode Digitally-Synthesized Frequency-Translated RF Filtering,"2018IEEE Radio Frequency Integrated Circuits Symposium(RFIC),2018,pp.92-95.

disclosure of Invention

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

The technical problem of the invention is solved by the following technical scheme:

a current mode receiver comprises a low noise transconductance amplifier, a mixer, a current mode low pass filter and a current mode ADC;

the low-noise transconductance amplifier is used for converting the received radio-frequency power signal into a radio-frequency current signal;

the mixer is used for down-converting the radio frequency current signal into a baseband current signal;

the current mode low-pass filter is used for amplifying and filtering the baseband current signal and transmitting the baseband current signal to the current mode ADC through a current mirror or in a direct coupling mode;

the current-mode ADC is used for quantizing the baseband current signal and outputting a digital signal.

In some embodiments, 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, and a baseband current signal output by the ac current filter and a dc current generated by an adjustable dc current source are input to the current-controlled oscillator via a current mirror.

In some embodiments, 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, and the ac current filter is connected to 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 to the current controlled oscillator together in a direct coupling manner.

In some embodiments, the current-mode ADC is a CT- Σ Δ ADC, the current-mode low-pass filter is an alternating current filter capable of outputting only alternating current, the alternating current filter output common-mode voltage is coincident with the input common-mode voltage of the operational amplifier, and the alternating current filter passes the baseband current signal to the current-mode CT- Σ Δ ADC in a direct coupling manner.

In some embodiments, in the circuit of the ac current filter, the transistor size of the output stage of the ac current filter is changed to adjust the gain, so that the swing of the signal current can be changed under different processes, voltages, and temperatures, and the ring oscillation frequency of the current controlled oscillator is kept stable, so that the ADC can have the same quantization range; the switching circuit of the transistor can be used as an interface for digital calibration.

In some embodiments, the adjustable dc current source is in an array form, and the adjustable dc current source array can change the magnitude of the dc current according to the application requirement, adjust the magnitude of the common mode current according to different processes, voltages, and temperatures, and stabilize the center frequency of the current control oscillator; the switching circuit of the adjustable dc current source array can be used as an interface for digital calibration.

In some embodiments, the rf current signal output by the low noise transconductance amplifier is transmitted to the mixer through a dc blocking capacitor.

In some embodiments, the mixer down-converts the rf current signal output by the lna into a baseband current signal by a high frequency local oscillator signal, which is provided by a phase locked loop to be a double frequency signal, divided by two by a frequency divider, and converted from a 50% duty cycle to a 25% duty cycle high frequency local oscillator signal.

The invention also provides a receiving method of the current mode receiver, which is characterized in that the current mode receiver is adopted to receive and quantize the analog signal, and the method comprises the following steps:

s1: converting the received radio frequency power signal into a radio frequency current signal through a low noise transconductance amplifier;

s2: down-converting the radio frequency current signal into a baseband current signal by a mixer;

s3: amplifying and filtering the baseband current signal through a current-mode low-pass filter, and transferring the baseband current signal to a current-mode ADC through a current mirror or in a direct coupling manner;

s4: the baseband current signal is quantized by a current-mode ADC and a digital signal is output.

Compared with the prior art, the invention has the advantages that:

the invention has the following beneficial effects:

according to the current mode receiver, through the arrangement of the technical characteristics of the low-noise transconductance amplifier, the frequency mixer, the current mode low-pass filter, the current mode ADC and the like, the current mode receiver can effectively comprise the current mode ADC through a simple interface circuit, the nonlinear conversion from voltage to current can be reduced, and the complicated and high-power-consumption transimpedance amplifier, the V-I conversion circuit and the digital calibration circuit in the prior art are reduced, so that the receiver with high bandwidth, low power consumption, simple structure and high linearity is realized.

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

the high-frequency local oscillator signal is provided with a double-frequency signal by the phase-locked loop, is subjected to frequency division by the frequency divider, and is converted into the high-frequency local oscillator signal with the 25% duty ratio from the 50% duty ratio, so that the noise deterioration caused by the overlapping of IQ two paths of the receiver is reduced, the link gain of the receiver is increased, the sensitivity of the receiver is improved, and the requirement on the linearity of the ADC is reduced.

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 can be changed under different PVTs (Process, voltage, temperature), the ring oscillation frequency of the current control oscillator is kept unchanged, and the ADC has the same quantization range. For the central frequency, an adjustable direct current source is adopted, namely the magnitude of the common-mode current is adjusted according to different PVTs, so that the central frequency of the current control oscillator is controlled to be basically unchanged. The adjustable direct current source is in an array form, and the size of direct current can be changed according to application requirements. In addition, the switching circuit of the adjustable direct current source array can also be used as an interface for digital calibration, so that further optimization in the follow-up process is facilitated.

Common-mode current is not needed at the input end of the CT-sigma delta ADC, the output common-mode voltage of 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 and the CT-sigma delta ADC are effectively combined, meanwhile, the input resistance of the CT-sigma delta ADC, which has a large influence on linearity, is saved due to the combination of the AC amplifier and the CT-sigma delta ADC, and the adjustment of the input resistance is avoided; and the interface circuit can still utilize the gain adjustment function of the second current-mode low-pass filter to optimize the signal-to-noise ratio of the ADC by increasing the resolution of the ADC.

Other advantages of embodiments of the present invention will be further described below.

Drawings

FIG. 1 is a schematic diagram of a prior art current controlled oscillator based analog to digital converter;

FIG. 2 is a schematic diagram of a prior art voltage controlled oscillator based analog to digital converter;

FIG. 3 is a schematic diagram of a current-mode receiver according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a current-mode receiver including a current-controlled oscillator-based analog-to-digital converter according to an embodiment of the present invention;

FIG. 5 is a receiving method of a current-mode receiver in an embodiment of the invention;

FIG. 6 is a schematic diagram of a current-mode low pass filter in an embodiment of the invention;

FIG. 7 is a schematic diagram of an interface between an AC current amplifier and a current controlled oscillator according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of an alternative interface between an AC current amplifier and a current controlled oscillator in an embodiment of the present invention;

fig. 9 is a schematic diagram of an interface between an ac current amplifier and a CT- Σ Δ ADC according to an embodiment of the present invention.

Detailed Description

The invention will be further described with reference to the accompanying drawings and preferred embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

It should be noted that the terms of orientation such as left, right, upper, lower, top and bottom in the present embodiment are only relative concepts or are referred to the normal use status of the product, and should not be considered as limiting.

In the schematic diagram of the CCO-based adc in the prior art, as shown in fig. 1, an input current Iin includes a common mode current and an alternating current, and is injected into N inverters as a bias current. After the inverter chain formed by the inverters starts to oscillate, the output ends of the N inverters are subjected to time integration by the oscillation frequency to obtain N phase information, the phase information is subjected to N frequency-to-digital converters to obtain N digital codes, and the digital codes are subjected to a full adder to output a quantization result DOUT (digital output) represented by a number.

In the prior art, a schematic diagram of a VCO-based adc is shown in fig. 2, an input voltage Vin includes a common mode voltage and an alternating current voltage, a current obtained through V-I conversion of a transistor is injected into N inverters as a bias current, after an inverter chain formed by the inverters starts to oscillate, output ends of the N inverters integrate time by an oscillation frequency to obtain N phase information, the phase information obtains N digital codes through N frequency-to-digital converters, and the digital codes output a quantization result DOUT represented by a number through a full adder.

The summary of the embodiments of the present invention is as follows:

the embodiment of the invention provides a current mode receiver, and the schematic diagram of the current mode receiver is shown in fig. 3, and the current mode receiver comprises a low noise transconductance amplifier, a mixer, a current mode low-pass filter and a current mode ADC;

the low-noise transconductance amplifier is used for converting the received radio-frequency power signal into a radio-frequency current signal; therefore, all the circuit modules behind the current-mode receiver process the current signals, so that the advantages of the current-mode receiver are fully utilized; the radio frequency current signal output by the low noise transconductance amplifier is transmitted to the mixer through the blocking capacitor.

The mixer is used for down-converting the radio frequency current signal into a baseband current signal; the frequency mixer down-converts the radio frequency current signal output by the low-noise transconductance amplifier into a baseband current signal through a high-frequency local oscillator signal, the high-frequency local oscillator signal provides a double-frequency signal through a phase-locked loop, the double-frequency signal is subjected to frequency division by a frequency divider, and the double-frequency signal is converted into the high-frequency local oscillator signal with the duty ratio of 25% through 50%.

The current mode low-pass filter is used for amplifying and filtering the baseband current signal and transmitting the baseband current signal to the current mode ADC through a current mirror or in a direct coupling mode;

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

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 the 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 to the current controlled oscillator together. The adjustable direct current source is in an array form, the adjustable direct current source array can change the magnitude of direct current according to application requirements, can adjust the magnitude of common-mode current according to different processes, voltages and temperatures, and stabilizes the central frequency of the current control oscillator; the switching circuit of the adjustable direct current source array can be used as an interface for digital calibration.

In another embodiment, the current mode ADC is a CT- Σ Δ (Continuous-Time 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 that is consistent with the input common mode voltage of the operational amplifier, and the ac current filter passes the baseband current signal to the current mode CT- Σ Δ ADC in a direct coupling manner.

As shown in fig. 5, an embodiment of the present invention further provides a receiving method of a current-mode receiver, including the following steps:

s1: converting the received radio frequency power signal into a radio frequency current signal through a low noise transconductance amplifier;

s2: down-converting the radio frequency current signal into a baseband current signal by 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 mode;

s4: the baseband current signal is quantized by a current-mode ADC and a digital signal is output.

Example (b):

as shown in fig. 4, the present embodiment provides a current-mode receiver including a CCO-based adc (analog-to-digital converter based on a current controlled oscillator), and a signal path thereof includes: low Noise Transconductance Amplifier (LNTA), MIXER (MIXER), current mode low pass filter (current mode LPF), current-to-Digital Converter (ADC), phase Locked Loop (PLL) providing high frequency local oscillator signal, and frequency Divider (Divider). Firstly, a signal is input through a low-noise transconductance amplifier, the low-noise transconductance amplifier converts a radio-frequency power signal received by an antenna into a radio-frequency current signal, and all circuit modules behind the low-noise transconductance amplifier process the current signal, so that the advantages of a current mode receiver are fully utilized; the radio frequency current signal is transmitted to the mixer through a blocking capacitor (Cdc) in fig. 4, the radio frequency current signal output by the low noise transconductance amplifier is down-converted into a baseband current signal through a high frequency local oscillator signal, the high frequency local oscillator signal provides a double frequency signal by a Phase Lock Loop (PLL), the double frequency signal is divided by a frequency Divider (Divider), and the double frequency signal is converted into a high frequency local oscillator signal with a duty ratio of 25% by a 50% duty ratio, so that not only is noise deterioration caused by overlapping of two paths of an IQ receiver reduced, but also the gain of a link of the receiver is increased, the sensitivity of the receiver is improved, and the requirement on the linearity of the ADC is reduced; the subsequent current-mode low-pass filter, which is also essentially a variable-gain current amplifier with poles, is a variable-gain current amplifier as shown in fig. 6, and thus has two main functions:

1. amplifying a current signal, increasing the resolution of the ADC, reducing offset requirements on a comparator in the ADC, reducing quantization noise and improving the signal-to-noise ratio of the ADC;

2. and filtering out-of-band interference, and preventing out-of-band signals from aliasing to the in-band to cause larger harmonic waves and deteriorate linearity.

And finally, injecting the baseband current signal output by the current mode low-pass filter into a current mode ADC through a current mirror or a direct coupling mode, and quantizing the baseband current signal by the current mode ADC to obtain a digital signal.

As shown in FIG. 6, baseband current signals are input from INN and INP, the current signals are converted into voltage signals through a complementary current mirror input stage, the current mirror image tube is M1/M5/M4/M8, meanwhile, a voltage amplifier A and M1/M2/M3/M4 form a negative feedback loop, vcm is a negative input end of the voltage amplifier, the input potential of the current amplifier is guaranteed to be stabilized near a vcm common mode level, rc and Cc are miller capacitance resistors, the loop stability is improved, rz and Cz are neutralization capacitance resistors, an extra zero pole is introduced, and the bandwidth of the current amplifier is expanded. The current amplifier is a symmetrical form, namely a fully differential amplifier, the output is OUTN and OUTP, and secondary nonlinearity, common mode noise and the like can be effectively inhibited. Vp and vn are bias levels of the common-gate transistors M3 and M7, and VSS is ground or power.

The key of the current-mode receiver in the embodiment of the invention is the interface of the current-mode low-pass filter and the current-mode ADC. For current controlled oscillator based analog to digital converters, the bias current of the Current Controlled Oscillator (CCO) consists of a dc current and an ac current, note that the bias current is injected from the top of the inverter in fig. 1, but the bias current can also be injected from the bottom.

An interface circuit provided in an embodiment of the present invention inputs a baseband current signal output by an ac current filter and a dc current generated by an adjustable dc current source into a current controlled oscillator through a current mirror, as shown in fig. 7, as a differential structure, a current amplifier in fig. 7 uses only half of circuits as an illustration, an actual current is in a differential form, that is, the other half of the circuits is in a mirror image relationship with the circuit in fig. 7. The current amplifier in fig. 7 outputs an alternating current AC, which is injected into N current-controlled oscillators together with a Direct Current (DC) that can be regulated (tuning) by current mirror replication. This application is applicable to the case where the current controlled oscillator voltage swing varies widely, since the current controlled oscillator voltage swing may vary by as much as several hundred millivolts as the signal current varies.

The other proposed structure is an alternating current filter which is connected with an adjustable direct current source in parallel, and alternating current generated by the alternating current filter and direct current generated by the direct current source are injected into the current control oscillator together. As shown in fig. 8, the current amplifier outputs an AC current AC, which is directly injected into the N current-controlled oscillators together with a dc current that can be regulated (tuning). The structure reduces the use of a current mirror, and is suitable for the condition that the voltage swing of the current control oscillator changes slightly, because the current control oscillator is directly connected with the output end of the current amplifier, the output common mode level of the amplifier cannot change greatly, otherwise, the performance can be seriously influenced. However, the current amplifier at the front end of the interface may adopt a complementary structure as shown in fig. 6 to implement a current mirror, which has high linearity and relatively larger output swing compared to a common current mirror.

Since the oscillation frequency range and the center frequency of the current controlled oscillator vary greatly for different processes, voltages, and temperatures (PVT), tuning, i.e., changing the transistor size of the output stage of the ac current filter, is required. For the oscillation frequency range, the oscillation frequency range is in direct proportion to the swing of the signal current. Therefore, a current amplifier with adjustable gain is adopted, such as transistors on the left and right sides in fig. 6, and a transistor with 4 bits in fig. 6 is adopted for adjustment, and the bit number of the transistor can be increased or decreased according to practical application, so as to meet the requirements of different precisions and application scenes. By using the method to adjust the gain, the swing amplitude of the signal current can be changed under different PVTs, the ring oscillation frequency of the current control oscillator is kept unchanged, and the ADC has the same quantization range. For the center frequency, the adjustable direct current source in fig. 7 and 8 is adopted, that is, the magnitude of the common mode current is adjusted according to different PVTs, so that the center frequency of the current control oscillator is controlled to be basically unchanged. Also, the adjustable dc current source is in an array form, and the dc current can be changed according to the application requirement. In addition, the switching circuits of the adjustable direct current source arrays can also be used as interfaces for digital calibration, so that further optimization in the follow-up process is facilitated.

For CT- Σ Δ ADC, one proposed interface structure is to subtract the feedback current I _ DAC of the DAC (Digital-to-Analog Converter) from the output current Iin of the ac current filter, and directly inject the residual current I _ RES into CT- Σ Δ ADC, as shown in fig. 9. Because the input end of the CT-sigma delta ADC does not need common-mode current, only the output common-mode voltage of the alternating current filter is required to be consistent with the input common-mode Voltage (VCM) of the operational amplifier in the ADC, and therefore the efficient combination of the high-bandwidth alternating current amplifier and the CT-sigma delta ADC is realized. Meanwhile, the combination of the two also saves the input resistance of the CT-sigma delta ADC which has larger influence on the linearity, and avoids the adjustment of the input resistance. Also, the interface circuit can still utilize the gain adjustment function of the AC current amplifier to optimize the signal-to-noise ratio of the ADC by increasing the resolution of the ADC.

The ac current filter in fig. 9 outputs an ac current as an input current Iin of the CT- Σ Δ ADC, and a residual circuit I _ RES obtained by subtracting the input current Iin from a feedback circuit I _ DAC of the DAC becomes an integrated current of an analog integrator (operational amplifier + cross-over capacitor in the figure), and the integrated voltage is used to obtain a digital quantization result DOUT through a quantizer, and this quantization result also drives the DAC to generate the I _ DAC. Note that fig. 9 shows only a CT- Σ Δ ADC with first-order filtering, and actually there are very many CT- Σ Δ ADC structures.

In summary, in the current-mode receiver architecture including the current-mode ADC, after the output of the current signal is realized by the low-noise transconductance amplifier, the signal is down-converted to the baseband signal by the mixer, amplified and filtered by the current-mode low-pass filter, and then the signal is transferred to the current-mode ADC for quantization by using a simple current mirror or a direct coupling manner, and the circuit is efficiently used for adjusting the center frequency and the oscillation frequency range of the current-controlled oscillator. The embodiment of the invention realizes that the current mode receiver effectively comprises the current mode ADC through the simple interface circuit, reduces the trans-impedance amplifier, the V-I conversion circuit and the digital calibration circuit which have higher complexity and higher power consumption in the prior art, and finally realizes the receiver with high bandwidth, low power consumption, simple structure and high linearity.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. It will be apparent to those skilled in the art that various equivalent substitutions and obvious modifications can be made without departing from the spirit of the invention, and all changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (9)

1. A current-mode receiver, characterized by: the low-noise transconductance amplifier comprises a low-noise transconductance amplifier, a frequency mixer, a current-mode low-pass filter and a current-mode ADC;

the low-noise transconductance amplifier is used for converting the received radio-frequency power signal into a radio-frequency current signal;

the mixer is used for down-converting the radio frequency current signal into a baseband current signal;

the current-mode low-pass filter is used for amplifying and filtering the baseband current signal and transmitting the baseband current signal to the current-mode ADC through a current mirror or in a direct coupling mode;

the current-mode ADC is used for quantizing the baseband current signal and outputting a digital signal.

2. The current-mode receiver of claim 1, wherein: the current mode ADC is an ADC with a current control oscillator, the current mode low-pass filter is an alternating current filter only capable of outputting alternating current, and a baseband current signal output by the alternating current filter and direct current generated by an adjustable direct current source are input into the current control oscillator through a current mirror.

3. The current-mode receiver of claim 1, wherein: the current mode ADC is an ADC with a current control oscillator, the current mode low-pass filter is an alternating current filter only capable of outputting alternating current, the alternating current filter is connected with an adjustable direct current source, 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 control oscillator together in a direct coupling mode.

4. The current-mode receiver of claim 1, wherein: the current mode ADC is a CT- Σ Δ ADC, the current mode low-pass filter is an alternating current filter capable of outputting only alternating current, the alternating current filter outputs a common-mode voltage that is identical to an input common-mode voltage of an operational amplifier, and the alternating current filter passes the baseband current signal to the current mode CT- Σ Δ ADC in a direct coupling manner.

5. The current-mode receiver of claim 2, wherein: in the circuit of the alternating current filter, the gain is adjusted by changing the size of a transistor of an output stage of the alternating current filter, so that the swing amplitude of signal current can be changed under different processes, voltages and temperatures, the ring oscillation frequency of the current control oscillator is kept stable, and an ADC (analog to digital converter) can have the same quantization range; the switching circuit of the transistor can be used as an interface for digital calibration.

6. The current-mode receiver of claim 3, wherein: the adjustable direct current source is in an array form, the adjustable direct current source array can change the size of direct current according to application requirements, can adjust the size of common-mode current according to different processes, voltages and temperatures, and stabilizes the central frequency of the current control oscillator; the switching circuit of the adjustable dc current source array can be used as an interface for digital calibration.

7. The current-mode receiver of claim 1, wherein: and the radio-frequency current signal output by the low-noise transconductance amplifier is transmitted to the mixer through a blocking capacitor.

8. The current-mode receiver of claim 1, wherein: the frequency mixer down-converts the radio frequency current signal output by the low-noise transconductance amplifier into a baseband current signal through a high-frequency local oscillator signal, the high-frequency local oscillator signal provides a double-frequency signal through a phase-locked loop, the double-frequency signal is subjected to frequency division by a frequency divider, and the double-frequency signal is converted into a high-frequency local oscillator signal with 25% duty ratio through 50% duty ratio.

9. A receiving method of a current-mode receiver, characterized in that receiving and quantizing an analog signal with a current-mode receiver according to any one of claims 1 to 8, comprises the steps of:

s1: converting the received radio frequency power signal into a radio frequency current signal through a low noise transconductance amplifier;

s2: down-converting the radio frequency current signal into a baseband current signal by a mixer;

s3: amplifying and filtering the baseband current signal through a current-mode low-pass filter, and transferring the baseband current signal to a current-mode ADC through a current mirror or in a direct coupling manner;

s4: the baseband current signal is quantized by a current-mode ADC and a digital signal is output.

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