A super regenerative receiver with main lobe filtering function

Abstract

The present invention discloses a super regenerative receiver with a main lobe filtering function, which relates to the field of communication technology and proposes a solution to 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 filter is also provided to filter out signal lobes other than the main signal lobe in the mixer output signal. The advantage is that through the asynchronous quenching technology and the main lobe filtering technology, spectrum aliasing is avoided, the system bandwidth requirement is reduced, the requirement for a high-precision clock is eliminated, and the signal quality of communication is improved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a super regenerative receiver with a main lobe filtering 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 main lobe filtering function to solve the problems existing in the above-mentioned prior art.

[0006] The super regenerative receiver with main lobe filtering 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 filter is also provided for filtering out signal lobes other than the main signal lobe in the mixer output signal.

[0012] The symbol rate of the RF signal is f s , the center frequency is f0, and the frequency of the quenching signal is f q , then f q >f s ; The output signal of the super regenerative amplifier contains multiple signal lobes with the same information as the RF signal, and the spacing of the signal lobes is f q And the center frequency of the main signal lobe is f0.

[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 third 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 inverting 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 main lobe filtering function described in the present invention has the advantages of avoiding spectrum aliasing, reducing system bandwidth requirements, eliminating the requirements for high-precision clocks, and improving communication signal quality through asynchronous quenching technology and main lobe filtering technology. 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 the main lobe filtering is performed by the filter.

[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 the main lobe filtering is performed by the filter.

[0028] Figure 6 It is the trajectory and constellation diagram of the super regenerative receiver demodulating the 64QAM 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 main lobe filtering 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 4 The output signal spectrum of the super regenerative amplifier SRA with asynchronous quenching is given, which shows similar sampling characteristics of the super regenerative amplifier SRA: the center frequency of the input RF signal is f0, and the frequency of the quenching signal 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 f0.

[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 third transistor M3, 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 f of the RF signal is s and the quenching signal frequency f q Equal to the transmission symbol rate f without crosstalkq 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. The present invention proposes to use a larger than 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 and 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 f LO =f0. The main advantage of the zero intermediate frequency scheme is that a low-pass filter can be used to implement main lobe filtering, and no spectrum aliasing will be generated due to mixing. In practice, the bandwidth of the mixer is limited, and the signal integrity of the high-order signal lobe may be damaged. However, the super-regenerative receiver proposed in the present invention filters out the high-order signal lobe, so it will not be affected, and the requirement for the mixer bandwidth is greatly reduced. Similarly, in the subsequent circuits of the super-regenerative receiver, the bandwidth requirements of all intermediate frequency circuits are also greatly reduced.

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

[0054] The present invention proposes to use a low-pass filter to filter out the high-order signal lobe and retain the main signal lobe. Due to the adoption of the aforementioned asynchronous quenching, the filter input signal is also sparse, and the filter is easy to implement. After low-pass filtering, the intermediate frequency output signal is equivalent to down-converting the radio frequency signal with a center frequency of f0 to DC, that is, 0 frequency.

[0055] The IF signal before and after filtering is shown in Figure 3In the paper, the effect of filtering in the time domain is shown: a smooth IF signal is extracted from the unprocessed IF signal of a super regenerative receiver SRR with a pulse shape by filtering. Figure 5 (a) before filtering and Figure 5 (b) shows the spectrum of the filtered I-channel intermediate frequency signal. It can be seen that there are no spectrum multi-signal lobes because it can be confirmed that the high-order signal lobes have been filtered out.

[0056] Figure 6 The demodulation constellation diagram of the super regenerative receiver SRR under 64QAM 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 that does not require quenching signal synchronization and has a Nyquist bandwidth for the intermediate frequency. It successfully realizes the demodulation of 64QAM signals and has a very low EVM.

[0057] Figure 7 A conventional direct frequency multiplication receiver is given as a comparative example 1, and Figure 8 A 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.

[0058] 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.

[0059] 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 filtering to retain the main signal lobe for communication solves the problem of large intermediate frequency bandwidth and the need for a high-speed ADC.

[0060] Finally, the super regenerative receiver with main lobe filtering function described in the present invention has the following technical advantages:

[0061] 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).

[0062] 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.

[0063] Low distortion and noise - The following three points reduce distortion or noise: (1) The proposed scheme does not have spectral aliasing, and the distortion caused by aliasing is eliminated compared to conventional super-regenerative receivers (SRR). (2) By using asynchronous quenching, the receiver allows narrowband operation or spectrum multiplexing to reduce single-channel in-band jitter, which can achieve lower distortion than conventional super-regenerative receivers (SRR). (3) The signal lobes outside the main signal lobe contain phase noise introduced by the quenching signal, and the signal-to-noise ratio is lower. This scheme filters out the signals outside the main lobe and reduces the noise.

[0064] 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 main lobe filtering 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 of the super regenerative amplifier 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 filter is also provided to filter out signal lobes other than the main signal lobe in the mixer output signal; 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; A 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.

2. A super regenerative receiver with main lobe filtering function according to claim 1, characterized in that: The symbol rate of the RF signal is f s , the center frequency is f0, and the frequency of the quenching signal is f q , then f q >f s ; The output signal of the super regenerative amplifier contains multiple signal lobes with the same information as the RF signal, and the spacing of the signal lobes is f q And the center frequency of the main signal lobe is f0.

3. A super regenerative receiver with main lobe filtering 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.

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