A super regenerative receiver with subsampling function

Abstract

The present invention discloses a super regenerative receiver with a sub-sampling function, which relates to the field of communication technology, and proposes this solution to solve the problem of spectrum aliasing in the prior art. It is characterized in that the quenching signal is not synchronized with the radio frequency signal; a sampler is also provided, and the quenching signal is used as a sampling clock to sub-sample the intermediate frequency signal output by the mixer. The advantage is that since the quenching signal is used as the sampling clock, it does not require an additional clock circuit. And compared with the oversampling method in the prior art, the sampling rate is greatly reduced. Sub-sampling is performed on the intermediate frequency signal output by the mixer, because its spectrum has a multi-lobe feature and occupies a large bandwidth, but the bandwidth of the radio frequency signal is less than the sampling rate under asynchronous quenching, so sub-sampling will not cause spectrum aliasing.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a super regenerative receiver with a sub-sampling function. Background Art

[0002] Super regenerative receiver (SRR) can achieve high gain with low power consumption and has good performance at RF and even millimeter wave frequencies. It is a very competitive new solution for digital modulation receivers. However, existing technologies lack good support for digital communication systems, which is mainly reflected in the following two points:

[0003] (1) The frequency domain output of the super-regenerative circuit has multiple signal lobes, whose bandwidth is larger than the input signal bandwidth, and usually requires high-multiple oversampling, which seriously damages the simplicity of the complete communication system.

[0004] (2) The quenching signal is a synchronous signal, that is, the quenching signal frequency is the same as the symbol rate. This requires the circuit to introduce a clock that is synchronized with the input signal, which ultimately adds additional circuit structures. In addition, synchronous quenching will also cause spectrum aliasing problems. Summary of the invention

[0005] The object of the present invention is to provide a super regenerative receiver with a sub-sampling function to solve the problems existing in the above-mentioned prior art.

[0006] The super regenerative receiver with sub-sampling function described in the present invention comprises a super regenerative amplifier and a mixer;

[0007] The super regenerative amplifier is used to amplify the input radio frequency signal and then send it to the mixer, and the frequency response is controlled by the quenching signal;

[0008] The mixer is used to down-convert the amplified radio frequency signal to an intermediate frequency;

[0009] It is characterized in that

[0010] The quenching signal is not synchronized with the radio frequency signal;

[0011] A sampler is also provided to perform sub-sampling on the intermediate frequency signal output by the mixer using the quenching signal as a sampling clock.

[0012] The symbol rate of the RF signal is f s , the center frequency is f 0, the frequency of the quenching signal is f q , then f q > f s; When the quenching signal is used as the sampling clock, the spacing between the signal lobes in the intermediate frequency signal spectrum is f q And contain the same information, each signal lobe overlaps at 0 frequency to achieve subsampling.

[0013] The frequency of the local oscillator signal of the mixer is the same as the center frequency of the radio frequency signal.

[0014] The super regenerative amplifier structure is specifically as follows:

[0015] The source of the first transistor is grounded, the drain of the first transistor is connected to the in-phase differential output terminal, and the gate of the first transistor is connected to the in-phase differential input terminal;

[0016] The source of the second transistor is connected to the drain of the fifth transistor, the drain of the second transistor is connected to the in-phase differential output terminal, and the gate of the second transistor is connected to the in-phase differential output terminal;

[0017] The source of the third transistor is connected to the drain of the fifth transistor, the drain of the third transistor is connected to the inverting differential output terminal, and the gate of the third transistor is connected to the in-phase differential output terminal;

[0018] The source of the fourth transistor is grounded, the drain of the fourth transistor is connected to the inverting differential output terminal, and the gate of the fourth transistor is connected to the inverting differential input terminal;

[0019] The source of the fifth transistor is grounded, and the gate of the fifth transistor is connected to the quenching signal;

[0020] The first inductor is connected in series between VDD and the in-phase differential output terminal;

[0021] The second inductor is connected in series between VDD and the inverting differential output terminal.

[0022] The super regenerative receiver with sub-sampling function described in the present invention has the advantage that, since the quenching signal is used as the sampling clock, it does not need to add an additional clock circuit. And compared with the oversampling method in the prior art, the sampling rate is greatly reduced. Sub-sampling is performed on the intermediate frequency signal output by the mixer, because its spectrum has a multi-lobe feature and occupies a large bandwidth. However, the bandwidth of the RF signal is less than the sampling rate under asynchronous quenching, so sub-sampling does not cause spectrum aliasing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the super regenerative receiver described in the present invention.

[0024] Figure 2 It is a structural schematic diagram of the super regenerative amplifier SRA described in the present invention.

[0025] Figure 3 It is a schematic diagram of the time domain waveform of the analog intermediate frequency signal before and after sub-sampling by the sampler.

[0026] Figure 4 It is a schematic diagram of the spectrum of the output signal of the super regenerative amplifier SRA in the present invention.

[0027] Figure 5 It is a schematic diagram of the spectrum of the analog intermediate frequency signal before and after sub-sampling by the sampler.

[0028] Figure 6 It is the trajectory and constellation diagram of the super regenerative receiver demodulating the 64 QAM signal in the present invention.

[0029] Figure 7 It is a structural schematic diagram of comparative example 1.

[0030] Figure 8 It is a structural schematic diagram of comparative example 2.

[0031] Reference numerals:

[0032] L1-first inductor, L2-second inductor;

[0033] M1-first transistor, M2-second transistor, M3-third transistor, M4-fourth transistor, M5-fifth transistor. DETAILED DESCRIPTION

[0034] The structure of a super regenerative receiver with sub-sampling function described in the present invention is as follows: Figure 1 As shown, the transient waveform or spectrum at each node is also shown in the figure.

[0035] The radio frequency signal RF received by the super regenerative receiver is input to the input terminal of the super regenerative amplifier SRA, and the quenching signal Quench is input to the quenching terminal of the super regenerative amplifier SRA. The super regenerative amplifier SRA behaves as an oscillator controlled by a periodic quenching signal, and its start-up and decay periods are synchronized with the quenching signal. The super regenerative amplifier SRA consists of a frequency selection network and a time-varying feedback β(t) controlled by the quenching signal. The frequency selection network is such as an RLC resonant cavity, and its frequency response is represented by H(s). When the feedback is strong enough to meet the oscillator start-up conditions, the super regenerative amplifier SRA starts and amplifies the input radio frequency signal. When the feedback is weak, the super regenerative amplifier SRA oscillates and decays until the next quenching cycle, when the super regenerative amplifier SRA starts again and amplifies the signal.

[0036] The quenching signal can be a sine wave, a square wave with a certain duty cycle, a sawtooth wave, etc.

[0037] The oscillation signal established by the super regenerative amplifier SRA is related to the injected RF signal. In the time domain, the signal near the amplification start time node of the super regenerative amplifier SRA cycle has a pulse characteristic. Figure 4The output signal spectrum of the super regenerative amplifier SRA under asynchronous quenching is given, which shows similar sampling characteristics of the super regenerative amplifier SRA: the center frequency of the input RF signal is f 0, the quenching signal frequency is f q When , its output has multiple signal lobes containing the same information as the RF signal, with a spacing of f q And the center frequency of the main signal lobe is f 0.

[0038] like Figure 2 As shown, the super regenerative amplifier structure is specifically as follows:

[0039] A source of the first transistor M1 is grounded, a drain of the first transistor M1 is connected to the in-phase differential output terminal, and a gate of the first transistor M1 is connected to the in-phase differential input terminal;

[0040] The source of the second transistor M2 is connected to the drain of the fifth transistor M5, the drain of the second transistor M2 is connected to the in-phase differential output terminal, and the gate of the second transistor M2 is connected to the in-phase differential output terminal;

[0041] The source of the third transistor M3 is connected to the drain of the fifth transistor M5, the drain of the third transistor M3 is connected to the inverting differential output terminal, and the gate of the third transistor M3 is connected to the in-phase differential output terminal;

[0042] The source of the fourth transistor M4 is grounded, the drain of the fourth transistor M4 is connected to the inverting differential output terminal, and the gate of the fourth transistor M4 is connected to the inverting differential input terminal;

[0043] The source of the fifth transistor M5 is grounded, and the gate of the fifth transistor M5 is connected to the quenching signal;

[0044] The first inductor L1 is connected in series between VDD and the in-phase differential output terminal;

[0045] The second inductor L2 is connected in series between VDD and the inverting differential output terminal.

[0046] The working principle of the super regenerative amplifier SRA is that the cross-coupled pair composed of the second transistor M2 and the third transistor M3 is used to generate negative resistance, and the magnitude of the negative resistance is controlled by the tail current. The fifth transistor M5 is used as a tail current tube, and its gate is connected to the quenching signal, which is a periodic signal, so it controls the periodic change of the negative resistance of the cross-coupled pair. The change of the negative resistance is related to the Figure 1 The two inductors and the parasitic capacitance of the first transistor M1, the second transistor M2, the third transistor M3, the fourth transistor M4 and the output resistance form an RLC parallel resonant network. Figure 1 The frequency selection network corresponds to.

[0047] Figure 1 The circuit implementations of the remaining modules, including mixers, filters, etc., adopt the common knowledge of those skilled in the art.

[0048] The asynchronous quenching technology proposed in the present invention replaces the synchronous quenching technology in the prior art and has obvious advantages:

[0049] In the prior art, the symbol rate of the RF signal f s The quenching signal frequency f q Equal transmission symbol rate without crosstalk f q The theoretical minimum bandwidth of the RF signal is f q . But in practical applications, the symbol rate f s The bandwidth of the RF signal will be greater than f q At this time, the signal lobes will be aliased, and the signal integrity will be irreversibly damaged. f q > f s In this case, the output signal spectrum is relatively sparse and no aliasing occurs.

[0050] About the symbol rate f s The quenching signal frequency f q Unit explanation: The unit of rate is baud, and the unit of frequency is hertz. Although the two have different names in the technical field, they have substantially the same dimension 1 / s. Therefore, those skilled in the art can regard baud as an evolution of hertz in the field of communication engineering, thus confirming that the two are comparable.

[0051] The asynchronous quenching technology proposed in the invention also has the following advantages: 1. Since a synchronous low-jitter quenching signal is no longer required, the complexity of the circuit system is reduced. 2. The frequency response of the super regenerative amplifier SRA is related to the quenching signal. The quenching signal is not synchronized with the RF signal symbol clock, so it can be fixed through a simple circuit design without adding a complex clock circuit.

[0052] The mixer down-converts the output signal of the super regenerative amplifier SRA to an intermediate frequency. In this embodiment, a zero intermediate frequency solution is selected, that is, the mixer local oscillator signal LO frequency is f LO = f0. The main advantage of the zero-IF solution is that the image signal of the zero-IF receiver is the RF signal, and even if the IF signal of the super-regenerative receiver is a broadband signal with multiple signal lobes, no spectrum aliasing will occur due to mixing.

[0053] The subsampling technology proposed in the present invention replaces the existing high-rate oversampling technology:

[0054] The frequency spectrum of the intermediate frequency signal output by the mixer is f q The present invention adopts a quenching signal asynchronous with the symbol rate as the sampling clock, so that the signal near the 0 frequency after sampling is the superposition of the signal lobes of the original intermediate frequency signal.

[0055] Compared with the conventional oversampling method, this subsampling method is very simple. Since the quenching signal is used as the sampling clock, it does not require an additional clock signal circuit. And compared with the oversampling method, the sampling rate is greatly reduced. Subsampling is performed on the intermediate frequency signal output by the mixer. Because its spectrum has multi-lobe characteristics and occupies a large bandwidth, the RF signal bandwidth is less than the sampling rate in the case of asynchronous quenching, so subsampling will not cause spectrum aliasing.

[0056] In practical applications, the sampler can be replaced by various sample holders.

[0057] The IF signal before and after subsampling is shown in Figure 3 In the figure, the time domain waveforms before and after sampling are shown: the rectangular intermediate frequency signal is extracted from the unprocessed intermediate frequency signal of the super regenerative receiver SRR with a pulse shape by subsampling. Figure 5 (a) shows the sample before and after Figure 5 (b) shows the spectrum of the sampled I-channel intermediate frequency signal. It can be seen that the spectrum of the rectangular intermediate frequency signal has a sinc function envelope.

[0058] Figure 6 The demodulation constellation diagram of the super regenerative receiver SRR under 64 QAM modulation is given. Figures 1 to 5 It is obvious that the super regenerative receiver SRR proposed in the present invention is a quasi-direct conversion receiver without quenching signal synchronization, which successfully realizes the demodulation of 64 QAM signal and has very low EVM.

[0059] Figure 7 A conventional direct frequency multiplication receiver is given as a comparative example 1, and Figure 8A conventional super-regenerative receiver is given as comparative example 2. To demonstrate the relevant working principle, the signal spectrum at each key node is also plotted in the corresponding figure. Conventional direct / conversion receivers use ordinary amplifiers and are down-converted to DC once. They do not have the spectrum multi-lobes in super-regenerative circuits. Even if filtering is used, its purpose is to filter out out-of-band interference or achieve matched filtering. Direct conversion receivers have a wide range of applications, but they still cannot meet technical requirements in some low-power scenarios and millimeter wave bands.

[0060] In a conventional super regenerative receiver SRR, the quenching rate is synchronized with the RF signal symbol rate and requires a small jitter to achieve alignment, which not only increases the complexity of the system clock scheme, but also brings two problems: Since the quenching rate is equal to the RF signal symbol rate, there will be aliasing of the signal lobes output by each super regenerative amplifier SRA. At the same time, the large bandwidth intermediate frequency signal is difficult to process, requiring a high-speed ADC and high-energy high-speed digital signal processing.

[0061] In summary, the main improvements of the present invention over the conventional super regenerative receiver SRR are: 1. The use of asynchronous quenching solves the problem of high-precision quenching signals and spectrum aliasing that need to be synchronized with the input signal symbol rate. 2. The use of subsampling technology to process large-bandwidth sparse multi-lobed intermediate frequency signals solves the problem that the intermediate frequency bandwidth is large and needs to be matched with a high-speed ADC.

[0062] Finally, the super regenerative receiver with sub-sampling function described in the present invention is

[0063] The main advantages of the implementation plan are:

[0064] Low complexity - Compared to conventional super-regenerative receivers (SRRs), the proposed scheme does not require a high-precision clock synchronized to the symbol rate, which greatly reduces the complexity of the clock system. In addition, the reduction in IF bandwidth reduces the requirements on the ADC (allowing sampling at the Nyquist frequency).

[0065] High energy efficiency - The proposed solution uses a super-regenerative amplifier as the main RF amplifier, which has the characteristics of high gain and low power consumption. In addition, in a complete receiver, especially in a high-speed communication system, the clock system and ADC occupy a large amount of power consumption, and the complexity is reduced while improving energy efficiency.

[0066] Low distortion and noise - The following three points reduce distortion or noise: (1) The proposed scheme does not have spectral aliasing. Compared with the conventional super-regenerative receiver SRR, the distortion caused by aliasing is eliminated. (2) The use of asynchronous quenching allows the receiver to operate in a narrowband or reduce the single-channel in-band jitter by spectrum multiplexing, which can achieve lower distortion than the conventional super-regenerative receiver SRR. (3) In the subsampling scheme, each signal lobe is coherent and superimposed in voltage, while the noise in each signal lobe is incoherent and superimposed in power. Compared with a single signal lobe, the signal-to-noise ratio of the sub-sampling signal is improved. (4) The subsampling scheme is conducive to the implementation of matched filters: Conventional super-regenerative receivers SRR use synchronous quenching, and the mid-frequency signal is difficult to match filter, while the proposed scheme can use digital filters to implement matched filters. Matched filters help improve the signal-to-noise ratio.

[0067] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A super regenerative receiver with sub-sampling function, comprising a super regenerative amplifier and a mixer; The super regenerative amplifier is used to amplify the input radio frequency signal and then send it to the mixer, and the frequency response is controlled by the quenching signal; The mixer is used to down-convert the amplified radio frequency signal to an intermediate frequency; It is characterized in that The quenching signal is not synchronized with the radio frequency signal; A sampler is also provided to perform sub-sampling on the intermediate frequency signal output by the mixer using the quenching signal as a sampling clock; The symbol rate of the RF signal is f s , the center frequency is f 0, the frequency of the quenching signal is f q , then f q > f s ; When the quenching signal is used as the sampling clock, the spacing between the signal lobes in the intermediate frequency signal spectrum is f q And contain the same information, each signal lobe overlaps at 0 frequency to achieve subsampling.

2. A super regenerative receiver with sub-sampling function according to claim 1, characterized in that: The frequency of the local oscillator signal of the mixer is the same as the center frequency of the radio frequency signal.

3. A super regenerative receiver with sub-sampling function according to claim 1, characterized in that: The super regenerative amplifier structure is specifically as follows: The source of the first transistor (M1) is grounded, the drain of the first transistor (M1) is connected to the in-phase differential output terminal, and the gate of the first transistor (M1) is connected to the in-phase differential input terminal; The source of the second transistor (M2) is connected to the drain of the fifth transistor (M5), the drain of the second transistor (M2) is connected to the in-phase differential output terminal, and the gate of the second transistor (M2) is connected to the in-phase differential output terminal; The source of the third transistor (M3) is connected to the drain of the fifth transistor (M5), the drain of the third transistor (M3) is connected to the inverting differential output terminal, and the gate of the third transistor (M3) is connected to the in-phase differential output terminal; The source of the fourth transistor (M4) is grounded, the drain of the fourth transistor (M4) is connected to the inverting differential output terminal, and the gate of the fourth transistor (M4) is connected to the inverting differential input terminal; The source of the fifth transistor (M5) is grounded, and the gate of the fifth transistor (M5) is connected to the quenching signal; The first inductor (L1) is connected in series between VDD and the in-phase differential output terminal; The second inductor (L2) is connected in series between VDD and the inverting differential output terminal.

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