Smoke box low-frequency broadband linear frequency modulation signal transmitting and receiving device

Abstract

The utility model provides a smoke box low-frequency broadband linear frequency modulation signal transmitting and receiving device, which solves the problems of limited radar signal bandwidth and the like, and comprises a main frequency synthesis and closed loop calibration circuit, the main frequency synthesis and closed loop calibration circuit is connected with a transmitting link circuit, the transmitting link circuit is connected with a receiving link circuit, and the receiving link circuit is connected with a receiving link circuit. The transmitting link is connected with a baseband signal sampling and processing circuit through a local oscillator signal generating and distributing circuit. The utility model has the advantages of higher frequency modulation slope, stable operation and the like.

Description

Technical Field

[0001] This utility model belongs to the technical field of tobacco detection equipment, specifically relating to a low-frequency broadband linear frequency modulation signal transceiver for tobacco boxes. Background Technology

[0002] Currently, commonly used methods for generating broadband linear frequency modulation (LFM) signals include: (1) Voltage-controlled oscillator (VCO) method: VCO is used to generate broadband LFM signals. By adjusting the control voltage of VCO, the output frequency can be linearly changed. The advantage of this method is that it is simple in principle and relatively direct in implementation. The disadvantage is that VCO has frequency drift problems with time and temperature, making it difficult to meet the requirements of high frequency modulation linearity and high frequency stability. (2) Direct digital synthesis (DDS) method: DDS method uses digital control circuits to precisely control the output waveform, frequency, amplitude, and phase to generate a near-ideal linear frequency modulation signal. The advantage of this method is that it is highly flexible and can precisely control the output waveform and parameters. The disadvantage is that the all-digital structure may lead to high spurious levels and it is difficult to generate signals with high frequency or wide bandwidth. (3) Phase-locked loop (PLL) method: This method locks the frequency and phase of the output signal to a reference signal. It consists of a voltage-controlled oscillator (VCO), a phase detector (PD), a loop filter (LF), etc. When generating a broadband linear frequency modulation signal, the PLL changes its output frequency by adjusting the control voltage of the VCO. The advantages of this method are high precision and stability. The disadvantage is that the locking time of the PLL is relatively long, which makes it difficult to meet the application scenarios that require a high frequency modulation slope.

[0003] This invention, combined with the actual application requirements of tobacco detection, can complete the real-time detection of the measured target. Therefore, a low-frequency broadband linear frequency modulation signal transceiver for tobacco boxes is designed. This device uses a mirror suppression mixer as the transmitting front end, which simplifies the radar transmitting and receiving links, ensuring both the high linearity of the transmitted signal and the generation of radar signals with high frequency modulation slope. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a reasonably designed smoke box low-frequency broadband linear frequency modulation signal transceiver that can generate radar signals with high frequency modulation slope.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, comprising a main frequency synthesis and closed-loop calibration circuit, the main frequency synthesis and closed-loop calibration circuit being connected to a transmission link circuit, the transmission link being connected to a receiving link circuit, and the transmission link being connected to a baseband signal sampling and processing circuit through a local oscillator signal generation and distribution circuit.

[0006] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the main frequency synthesis and closed-loop calibration circuit includes a digital sampling control circuit. The tuning voltage terminal of the digital sampling control circuit is connected to a second divider via a voltage-controlled oscillator. The second divider is connected to the frequency measurement terminal of the digital sampling control circuit.

[0007] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the voltage-controlled oscillator is selected as the TFNTG96 model, and the digital sampling control circuit is selected as the SM435B model.

[0008] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the transmitting link circuit includes a first divider connected to a voltage-controlled oscillator, the first divider being connected to a first image rejection mixer via a coupler, and the first image rejection mixer being connected to a transmitting antenna via a power amplifier.

[0009] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the first image suppression mixer is selected as the TRF37B32 model.

[0010] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the local oscillator signal generation and distribution circuit includes an amplifier connected to a coupler, the amplifier being connected to a first 90° bridge, a first image suppression mixer being connected to an intermediate frequency signal source via a second 90° bridge, and the intermediate frequency signal source being connected to a third 90° bridge.

[0011] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the intermediate frequency signal source is model AD9910.

[0012] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the receiving link circuit includes a second image rejection mixer connected to a first 90° bridge. The second image rejection mixer is connected to a receiving antenna via a low-noise amplifier. The second image rejection mixer is connected to a power divider circuit via an intermediate frequency signal filtering and amplification circuit. The power divider circuit is connected to a third 90° bridge via an intermediate frequency mixer.

[0013] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the second image suppression mixer is a TRF37B32 model, and the intermediate frequency mixer is an LTC5510 model.

[0014] In the aforementioned low-frequency broadband linear frequency modulation signal transceiver for a cigarette box, the baseband signal sampling and processing circuit includes an I / Q acquisition module that is located within the digital sampling control circuit and connected to the intermediate frequency mixer.

[0015] Compared with existing technologies, the advantages of this utility model are as follows: the voltage-controlled oscillator combined with an external frequency conversion module generates a radar signal with a high frequency modulation slope, covering a frequency band far exceeding that of traditional fixed frequency or narrowband frequency modulation systems; the frequency after frequency division of the voltage-controlled oscillator is monitored in real time through a digital sampling control circuit, and the tuning voltage is dynamically adjusted, which greatly reduces the frequency deviation problem of traditional open-loop oscillators; the receiving link uses a low-noise amplifier, which significantly improves the weak signal detection capability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the device composition of this utility model;

[0017] Figure 2 This is a schematic diagram of the closed-loop calibration components of this utility model;

[0018] In the diagram, the components are: digital sampling control circuit 1, voltage-controlled oscillator 12, second divider 13, frequency measurement terminal 14, transmitting antenna 2, first divider 21, coupler 22, first image rejection mixer 23, power amplifier 24, amplifier 3, first 90° bridge 31, second 90° bridge 32, third 90° bridge 33, intermediate frequency signal source 34, second image rejection mixer 4, low noise amplifier 41, receiving antenna 42, intermediate frequency signal filtering and amplification circuit 43, power divider circuit 44, intermediate frequency mixer 45, and I / Q acquisition module 5. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1-2 As shown, a low-frequency broadband linear frequency modulation signal transceiver for a cigarette box includes a main frequency synthesis and closed-loop calibration circuit. The main frequency synthesis and closed-loop calibration circuit is connected to a transmit link circuit, and the transmit link is connected to a receive link circuit. The transmit link is connected to a baseband signal sampling and processing circuit through a local oscillator signal generation and distribution circuit.

[0021] Specifically, the main frequency synthesis and closed-loop calibration circuit includes a digital sampling control circuit 1, which performs frequency measurement after frequency division of the voltage-controlled oscillator 12, generates the tuning voltage, and acquires the echo baseband I / Q signal. The tuning voltage terminal 11 of the digital sampling control circuit 1 is connected to a second divider 13 via the voltage-controlled oscillator 12. The voltage-controlled oscillator 12 generates a broadband linear frequency modulated (LFM) signal in the 4GHz-8GHz range. The second divider 13 divides the signal generated by the voltage-controlled oscillator 12 to a lower frequency for closed-loop calibration of the voltage-controlled oscillator 12. The second divider 13 is connected to the frequency measurement terminal 14 of the digital sampling control circuit 1. The main frequency synthesis and closed-loop calibration circuit performs closed-loop calibration of the voltage-controlled oscillator 12 to complete the broadband signal calibration of the voltage-controlled oscillator 12. After calibration, the digital sampling control circuit 1 controls the tuning voltage to make the voltage-controlled oscillator 12 output a broadband LFM signal with high linearity in the 4GHz-8GHz range.

[0022] Specifically, the voltage-controlled oscillator 12 is a TFNTG96 model, and the digital sampling control circuit 1 is an SM435B model. The 4GHz-8GHz wideband linear frequency modulation signal output by the voltage-controlled oscillator 12 is passed through the second divider 13 to generate 1GHz-2GHz and 2GHz-4GHz linear frequency modulation signals respectively. Then, by splicing the two signals, a complete 1GHz-4GHz linear frequency modulation signal is output.

[0023] In addition, the transmit link circuit includes a first divider 21 connected to the voltage-controlled oscillator 12. The first divider 21 is connected to a first image rejection mixer 23 via a coupler 22, which couples the transmit branch signal to the receive channel. The first image rejection mixer 23 is connected to the transmit antenna 2 via a power amplifier 24, which amplifies the transmit signal to the expected power. The transmit link circuit uses one path of the linear frequency modulated signal as the transmit signal, which is amplified and transmitted after passing through the first image rejection mixer 23. The other path is used as the local oscillator signal for the receive link circuit. The first image rejection mixer 23 and the second image rejection mixer 4 are responsible for the down-conversion processing of the transmit signal and the receive signal.

[0024] Meanwhile, the first image suppression mixer 23 is a TRF37B32 model.

[0025] As can be seen, the local oscillator signal generation and distribution circuit includes an amplifier 3 connected to the coupler 22 to amplify the coupled output signal. The amplifier 3 is connected to a first 90° bridge 31. The first image rejection mixer 23 is connected to an intermediate frequency signal source 34 through a second 90° bridge 32. The intermediate frequency signal source 34 is connected to a third 90° bridge 33. Each 90° bridge completes the quadrature generation of the local oscillator signal of the mixer. The intermediate frequency signal source 34 generates a 70MHz point frequency signal. Since this signal participates in the transmission and reception path, the frequency accuracy and stability requirements of this signal are not high, and an open-loop VCO can be used.

[0026] It is clear that the intermediate frequency signal source 34 uses the AD9910 model.

[0027] Preferably, the receiving link circuit includes a second image rejection mixer 4 connected to the first 90° bridge 31. The second image rejection mixer 4 is connected to the receiving antenna 42 via a low-noise amplifier 41, which amplifies the received echo signal. The second image rejection mixer 4 is connected to the intermediate frequency (IF) filtering and amplification circuit 43 via an IF signal filtering and amplification circuit. It is connected to a power divider circuit 44 to split the IF echo signal into two paths. The power divider circuit 44 is connected to the third 90° bridge 33 via an IF mixer 45 to complete the down-conversion processing of the IF echo signal.

[0028] Obviously, the second image suppression mixer 4 is a TRF37B32 model, and the intermediate frequency mixer 45 is an LTC5510 model.

[0029] Meanwhile, the baseband signal sampling and processing circuit includes an I / Q acquisition module 5 located within the digital sampling control circuit 1 and connected to the intermediate frequency mixer 45. The received echo signal undergoes I / Q demodulation of the baseband signal through two down-conversion processes, and the echo signal is digitized by the I / Q acquisition module 5 in the digital sampling control circuit 1.

[0030] The voltage-controlled oscillator 12 outputs a 4GHz-8GHz wideband linear frequency modulated (LFM) signal with a period of T0 and a 4GHz-8GHz wideband LFM signal with a width of 2×T0. When the period is T0, divider 1 is set to divide by 4; when the period is 2×T0, divider 1 is set to divide by 2. At this time, the frequency range of the generated LFM signal is 1GHz-4GHz, and the corresponding modulation slope is 3GHz / 3T0. One path of this signal is sent to the receiving end through coupler 22 as the local oscillator signal of the receiving link circuit. The other path is directly subjected to image rejection mixing. The local oscillator signal of the image rejection mixer is generated by intermediate frequency mixer 45. Intermediate frequency mixer 45 generates a standard 70MHz single-point frequency signal. After mixing, the signal is amplified by power amplifier 24 and then directly fed into transmitting antenna 2 to complete the radiation of the measured signal. The receiving antenna 42 receives the echo signal. After the echo signal is amplified by the low-noise amplifier 41, it is down-converted to an intermediate frequency (IF) signal of about 70MHz by the image suppression mixer. The IF signal is then amplified by the IF signal filtering and amplification circuit 43. The amplified IF signal is output as two IF signals with the same amplitude and phase by the power divider circuit 44. The two signals are mixed with a quadrature 70MHz point frequency signal to complete the baseband processing of the echo signal and output two baseband I / Q signals. The two I / Q signals are digitized by the digital sampling control circuit 1.

[0031] The digital sampling control circuit 1 generates equally spaced control quantities, D0 to Dn. To ensure the linearity of the linear frequency modulation signal, the smallest step size can be used, for example, using a 10-bit DA converter. The digital quantity generated by the digital sampling control circuit 1 ranges from 0 to 1023. When the control code generated by the digital sampling control circuit 1 is D0, the voltage value V0 after passing through the digital-to-analog converter (DA) link is given. At this time, the corresponding VCO output frequency is f0. Since the frequency of the VCO output signal is relatively high, it is difficult to directly measure the frequency using the digital sampling control circuit 1. Therefore, the VCO output signal needs to be distributed. For example, when the VCO output frequency is 4GHz-8GHz, after a 64-fold frequency division, the output frequency is 62.5MHz-125MHz. The digital sampling control circuit 1 uses a time window with a pulse width of T1 to count the frequency of the D0 product and obtain the count value N0. From this, the corresponding frequency value can be obtained as (N0×64 / T1). This process is repeated to complete the measurement of each frequency point from D0 to Dn. To ensure the accuracy of the frequency measurement, the measurement time T1 needs to be increased. By selecting an equally spaced frequency step from the measured frequency values ​​and outputting the corresponding control code, the closed-loop calibration of the linear frequency modulation signal can be completed.

[0032] In summary, the principle of this embodiment is as follows: a broadband oscillator is used to output a broadband linear frequency modulated signal of 4GHz-8GHz. A divider is used to convert the frequency of the transmitted signal from 4GHz-8GHz to 1GHz-4GHz. A mirror suppression mixer is used to output a probe signal. The echo signal is down-converted and digitally sampled by the receiving link circuit.

[0033] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

[0034] Although this document extensively uses terms such as digital sampling control circuit 1, voltage-controlled oscillator 12, second divider 13, frequency measurement terminal 14, transmitting antenna 2, first divider 21, coupler 22, first image rejection mixer 23, power amplifier 24, amplifier 3, first 90° bridge 31, second 90° bridge 32, third 90° bridge 33, intermediate frequency signal source 34, second image rejection mixer 4, low noise amplifier 41, receiving antenna 42, intermediate frequency signal filtering and amplification circuit 43, power divider circuit 44, intermediate frequency mixer 45, and I / Q acquisition module 5, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any additional limitation would contradict the spirit of this utility model.

Claims

1. A smoke box low frequency wideband chirp transceiver apparatus, characterized by, The main frequency synthesis and closed loop calibration circuit is connected with a transmitting link circuit, the transmitting link is connected with a receiving link circuit, and the transmitting link is connected with a baseband signal sampling and processing circuit through a local oscillator signal generation and distribution circuit.

2. The smoke box low-frequency wide-band linear frequency modulation signal transceiver device according to claim 1, characterized in that, The main frequency synthesis and closed loop calibration circuit comprises a digital sampling control circuit (1), a tuning voltage end (11) of the digital sampling control circuit (1) is connected with a second divider (13) through a voltage controlled oscillator (12), and the second divider (13) is connected with a frequency measurement end (14) of the digital sampling control circuit (1).

3. The smoke box low-frequency wide-band linear frequency modulation signal transceiver device according to claim 2, characterized in that, The voltage controlled oscillator (12) is selected from a TFN TG96 model, and the digital sampling control circuit (1) is selected from an SM435B model.

4. The smoke box low-frequency wide-band linear frequency modulation signal transceiver device according to claim 2, characterized in that, The transmitting link circuit comprises a first divider (21) connected with the voltage controlled oscillator (12), the first divider (21) is connected with a first image rejection mixer (23) through a coupler (22), and the first image rejection mixer (23) is connected with a transmitting antenna (2) through a power amplifier (24).

5. The smoke box low-frequency wide-band linear frequency modulation signal transceiver device according to claim 4, characterized in that, The first image rejection mixer (23) is selected from a TRF37B32 model.

6. The smoke box low-frequency wide-band linear frequency modulation signal transceiver device according to claim 4, characterized in that, The local oscillator signal generation and distribution circuit comprises an amplifier (3) connected with the coupler (22), the amplifier (3) is connected with a first 90° bridge (31), the first image rejection mixer (23) is connected with an intermediate frequency signal source (34) through a second 90° bridge (32), and the intermediate frequency signal source (34) is connected with a third 90° bridge (33).

7. The low-frequency wideband chirp transceiver of claim 6, wherein, The intermediate frequency signal source (34) is selected from an AD9910 model.

8. The low-frequency wideband chirp transceiver of claim 6, wherein, The receiving link circuit comprises a second image rejection mixer (4) connected with the first 90° bridge (31), the second image rejection mixer (4) is connected with a receiving antenna (42) through a low noise amplifier (41), the second image rejection mixer (4) is connected with a power dividing circuit (44) through an intermediate frequency signal filtering and amplifying circuit (43), and the power dividing circuit (44) is connected with the third 90° bridge (33) through an intermediate frequency mixer (45).

9. The low-frequency wideband chirp transceiving device of claim 8, wherein, The second image rejection mixer (4) is selected from a TRF37B32 model, and the intermediate frequency mixer (45) is selected from an LTC5510 model.

10. The low-frequency wideband chirp transceiver of claim 8, wherein, The baseband signal sampling and processing circuit comprises an I / Q acquisition module (5) arranged in the digital sampling control circuit (1) and connected with the intermediate frequency mixer (45).

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