A hardware design method for distance sensing and communication integrated system
By using high-isolation RF switches and FPGAs in contactless distance sensing and communication systems, communication and distance sensing are integrated, solving the problems of high hardware overhead and low spectrum utilization, and achieving a balance between high-precision distance sensing and communication.
Patent Information
- Application Number
- CN202310893293.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-20
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-07-20
AI Technical Summary
The separate deployment of the contactless distance perception system and the communication system results in large hardware overhead and low spectrum utilization, and the distance perception accuracy of the existing integrated design is insufficient.
A high-isolation RF switch is used to switch the mixer reference signal input, combined with FPGA to achieve the integration of communication and distance perception. Data processing and signal conversion are performed through FPGA to achieve three-mode switching.
Rationally utilize existing resources to realize communication, distance perception master and slave modes, improve spectrum utilization, and meet high-precision distance perception needs.
Smart Images
Figure CN116961689B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of hardware platform design, and in particular relates to a hardware design method for a distance sensing and communication integrated system. Background Art
[0002] Due to bandwidth and center frequency limitations, contactless distance sensing systems and communication systems are often deployed separately. To achieve higher distance sensing accuracy, contactless distance sensing systems occupy a relatively large bandwidth and therefore use a higher center frequency. To ensure communication reliability, communication systems typically select a relatively low center frequency, and the bandwidth used for communication is limited to the required bandwidth. Due to device and hardware limitations, the two systems are often deployed using different hardware to avoid interference between the systems. However, this approach results in suboptimal hardware overhead and spectrum utilization, resulting in significant waste of spectrum resources. Therefore, integrating distance sensing and communication is valuable research. Currently, there are mature solutions for integrating target sensing systems with communication systems to detect target properties. These solutions analyze the communication waveform reflected from the target surface to determine target properties and achieve target sensing. This solution can achieve target sensing while also providing distance sensing capabilities, but the distance sensing accuracy provided is lower than that of dedicated high-precision distance sensing systems. Therefore, for applications requiring only high-precision distance sensing and basic communication needs, a dedicated integrated distance sensing and communication system is still needed.
[0003] One waveform used in contactless high-precision distance sensing systems is FMCW (Frequency Modulated Continuous Wave). Its principle is to transmit a high-frequency continuous wave whose frequency changes over time according to the law of a sawtooth wave, and measure the frequency difference between the transmitted wave and the waveform reflected from the target surface to indirectly measure the electromagnetic wave propagation time between the system and the target object. The measured propagation time is then used to calculate the distance to be measured. A system block diagram using FMCW waves for distance sensing is shown below. Figure 1 shown.
[0004] The system controls a voltage-controlled oscillator (VCO) to generate an FMCW waveform with a sawtooth-like frequency. A modulator shifts the signal to a radio frequency (RF) before transmitting it from the transmitting antenna toward the target surface. The transmitted wave reflects off the target surface and propagates to the system's receiving antenna, where it is received. A mixer mixes the reflected and transmitted waves. Due to the stable frequency difference between the reflected and transmitted waves, the mixer outputs a beat signal with a stable frequency difference. This frequency contains the distance between the range sensing system and the target. After filtering out interference, the beat signal undergoes analog-to-digital conversion using an analog-to-digital converter (ADC). The resulting digital sequence is fed into the baseband processing unit to resolve the beat signal frequency and indirectly determine the target distance.
[0005] A general communication system uses a local oscillator (LO) to generate a high-frequency carrier, which is then transferred to the radio frequency and then transmitted through the transmitting antenna. During reception, the received signal obtained by the receiving antenna is first mixed with the carrier generated by the LO, and the communication signal on the radio frequency is transferred back to the baseband. After analog-to-digital conversion by the ADC, the digital sequence is sent to the baseband processing unit for further processing. The block diagram of a general communication system is shown below. Figure 2 shown.
[0006] contrast Figure 1 and Figure 2 ,It was found that the communication system and the distance ,measurement system can be reused to a certain extent in both the transmitting and receiving ,parts. Summary of the Invention
[0007] To address these issues, the present invention proposes an integrated communication and distance sensing platform that uses a high-isolation RF switch to switch mixer inputs. By switching the reference signal inputs to the mixers of the transmitting and receiving parts of each communicating party, three modes—communication, distance sensing master, and distance sensing slave—are implemented.
[0008] The technical solution of the present invention is:
[0009] A hardware design method for an integrated distance sensing and communication system uses a field-programmable gate array (FPGA) as a baseband processing unit. To implement communication functions, the transmitting FPGA performs constellation mapping on the transmitted data, generating a digital sequence that is sent to a digital-to-analog converter (DAC) for digital-to-analog conversion. The sequence is then modulated and transmitted. The receiving end demodulates the received signal and sends it to the ADC for analog-to-digital conversion. The receiving FPGA then demaps the received data.
[0010] When implementing the distance sensing function, the communication equipment is divided into a distance sensing host and a distance sensing slave. The implementation method of the distance sensing host is as follows: the FMCW waveform sequence of the signal generated by the host-side FPGA is mixed with the high-frequency LO generated by the host frequency synthesizer at the modulator after passing through the DAC, and the FMCW waveform is moved to the radio frequency. At the same time, the radio frequency waveform is transmitted to the demodulator at the host side through the path connected by the first radio frequency switch; the demodulator at the host side receives the signal transmitted by the slave and mixes it with the signal transmitted by the host side itself to obtain a beat frequency signal, which is sent to the host-side FPGA after analog-to-digital conversion is completed by the ADC. The beat frequency signal sequence is subjected to FFT transformation (Fast Fourier Transform, FFT) inside the FPGA to find the highest amplitude point in the spectrum and obtain the beat frequency signal frequency f b , thereby achieving distance perception;
[0011] The distance sensing slave is implemented by: the slave inputs the received signal into the demodulator and transmits the received signal to the slave's modulator through a path connected by a second RF switch. The slave's FPGA generates a DC signal, which is converted by the DAC and then mixed with the received signal in the slave's modulator to complete the signal forwarding.
[0012] The switching method for realizing the communication function and the distance sensing function is that, when realizing the communication function, the frequency synthesizer is connected to the modulator and the demodulator respectively through the radio frequency switch, and when realizing the distance sensing function, the radio frequency switch is adjusted so that the frequency synthesizer as the host is only connected to the modulator, and the output of the host-side modulator is connected to the reference signal input of the host-side demodulator through the radio frequency switch; the frequency synthesizer as the slave is only connected to the demodulator, and the input of the demodulator is also connected to the reference signal input of the modulator through the radio frequency switch.
[0013] The beneficial effects of the present invention are:
[0014] Compared with the existing technology, the hardware design method of the present invention can reasonably use existing resources to complete multiple functions. By switching the reference signal input of the mixer of the transmitting part and the receiving part of each communicating party, three modes of communication, distance sensing host and distance sensing slave can be realized. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 This is the block diagram of the existing FMCW distance sensing system.
[0016] Figure 2 It is a block diagram of the existing communication system.
[0017] Figure 3 It is a hardware structure diagram of the present invention.
[0018] Figure 4 It is a system block diagram of the communication mode of the present invention.
[0019] Figure 5 It is a block diagram of the distance perception mode system of the present invention. DETAILED DESCRIPTION
[0020] The present invention is described in detail below with reference to the accompanying drawings.
[0021] The principle of distance sensing is: let the FMCW continuous wave generated by the distance sensing system be s(t), and its instantaneous frequency f i Satisfy the following formula.
[0022]
[0023] Where f0 is the sweep start frequency, B is the sweep bandwidth, and T is the duration of one sweep. At this instantaneous frequency, the complex form of the FMCW continuous wave is as follows.
[0024]
[0025] After a round-trip propagation delay of τ, the reflected wave r(t) obtained by the receiving antenna can be expressed as follows.
[0026]
[0027] The reflected wave r(t) is mixed with the transmitted wave s(t) to obtain the target beat frequency signal.
[0028]
[0029] The beat signal frequencies correspond to the following.
[0030]
[0031] On the other hand, the propagation delay of the transmitted wave between the range perception system and the target should be expressed as:
[0032]
[0033] Where d is the distance between the distance sensing system and the target, and c is the speed of light. Combining equations (2-5) and (2-6), we obtain the following relationship between the distance between the two and the beat signal frequency.
[0034]
[0035] In view of this, the beat frequency signal needs to be sent to the baseband processing unit for further frequency resolution processing.
[0036] The communication mixing principle is as follows: Let b(t) be the baseband signal generated by the baseband processing unit and processed by the DAC. The local carrier C(t) maintained by the LO satisfies the following equation.
[0037]
[0038] Where, f c is the frequency of the local carrier. After the shift of the transmitting mixer, the transmitted signal is:
[0039]
[0040] For the receiver, after the receiving antenna obtains S(t), it is mixed with the receiver's LO to move the RF signal to the baseband. Let the moved signal be R(t), which satisfies:
[0041]
[0042] Under ideal conditions, R(t) = b(t), and the receiving end can obtain the baseband signal of the transmitting end without loss.
[0043] The hardware design block diagram of the present invention is as follows Figure 3 As shown in the figure, the core part of the platform will be composed of an FPGA as the baseband processing unit, a set of DACs and ADCs to complete the digital-to-analog and analog-to-digital conversion, a frequency synthesizer to synthesize the desired carrier frequency, a crystal oscillator to drive the FPGA, ADC, DAC and frequency synthesizer, a set of modems for mixing, and two RF switches to switch the reference signal input of the transmit channel modulator and the receive channel demodulator respectively. Other non-essential filters and power supply structures are not shown in the figure. Figure 3 It is reflected in.
[0044] By switching the RF switch, the platform provides three modes: communication, distance sensing master, and distance sensing slave. The communication mode is suitable for communication functions, while the distance sensing master and distance sensing slave modes are suitable for distance sensing functions. Compared to the high-precision distance sensing system's method of measuring reflections on the target surface, the two parties completing distance sensing in the communication system are usually two sets of communication equipment. In some cases, due to the size or orientation of the equipment, it is difficult to reflect on the desired target surface using traditional reflection-based measurement methods. Therefore, the device under test needs to receive and forward the measurement waveform as an equivalent form of surface reflection.
[0045] When the platform provides communication functions, the reference inputs of the modulators and demodulators on both the transmitting and receiving sides of the platform are switched to the outputs of the frequency synthesizers to provide a stable carrier C(t). The FPGA, which serves as the baseband processing unit in the transmitting channel, performs constellation mapping on the user's sent data and generates a digital sequence to send to the DAC; the FPGA in the receiving channel receives the ADC sampled data and demaps it to prepare for subsequent processing. At this time, the baseband processing units of both platforms provide basic communication functions. The block diagram of both platforms in this mode is as follows Figure 4 shown.
[0046] When the platform provides distance sensing function, both sides of the platform will be divided into distance sensing master and distance sensing slave, corresponding to distance sensing master mode and distance sensing slave mode respectively. Figure 5 shown.
[0047] In the distance sensing host mode, the FPGA transmit channel controls the frequency step word of the direct frequency synthesizer to generate an FMCW waveform. The RF switch is switched to the frequency synthesizer, and the modulator moves the FMCW wave to the RF transmitter. At the same time, the receive channel receives the forwarded waveform. The RF switch is switched to the transmit channel, and the demodulator mixes the forwarded waveform with the transmit waveform to obtain a beat frequency signal. After analog-to-digital conversion, it is sent to the FPGA. By performing an FFT transformation on the beat frequency signal sequence inside the FPGA, the highest amplitude point in the spectrum is found to obtain the beat frequency signal frequency f b After that, the target distance is measured using the aforementioned formula.
[0048] In distance sensing slave mode, the platform's transmit channel needs to forward the waveform obtained by the receive channel. The FPGA generates a DC signal on the output channel. The RF switch then switches to the receive channel. The modulator mixes the waveform obtained by the receive channel with the DC signal generated by the FPGA and transmits the mixed signal. The receive channel does not perform any other functions in distance sensing slave mode, so there are no requirements for the receive channel and the corresponding FPGA module.
Claims
1. A hardware design method for an integrated distance sensing and communication system. This method uses an FPGA as the baseband processing unit. To implement communication functions, the transmitting FPGA performs constellation mapping on the transmitted data, generating a digital sequence that is sent to the DAC for digital-to-analog conversion. This sequence is then modulated and transmitted. The receiving end receives the signal, demodulates it, and sends it to the ADC for analog-to-digital conversion. The receiving FPGA then demaps the received data. When implementing the distance sensing function, the communication device is divided into a distance sensing host and a distance sensing slave. The distance sensing host is implemented as follows: the FMCW waveform sequence of the signal generated by the host-side FPGA is mixed with the high-frequency LO generated by the host frequency synthesizer at the modulator after passing through the DAC, and the FMCW waveform is moved to the radio frequency. At the same time, the radio frequency waveform is transmitted to the demodulator on the host side through the path connected by the first radio frequency switch; the demodulator on the host side receives the signal transmitted by the slave and mixes it with the signal transmitted by the host side itself to obtain a beat frequency signal. The beat frequency signal is converted into digital form by the ADC and then sent to the host-side FPGA. The beat frequency signal sequence is subjected to FFT inside the FPGA to find the highest amplitude point in the spectrum and obtain the beat frequency signal frequency fb, thereby realizing distance sensing; The distance sensing slave is implemented by: the slave inputs the received signal into the demodulator and transmits the received signal to the slave's modulator through a path connected by a second RF switch. The slave's FPGA generates a DC signal, which is converted by the DAC and then mixed with the received signal in the slave's modulator to complete the signal forwarding. The switching method for realizing the communication function and the distance sensing function is that, when realizing the communication function, the frequency synthesizer is connected to the modulator and the demodulator respectively through the radio frequency switch, and when realizing the distance sensing function, the radio frequency switch is adjusted so that the frequency synthesizer as the host is only connected to the modulator, and the output of the host-side modulator is connected to the reference signal input of the host-side demodulator through the radio frequency switch; the frequency synthesizer as the slave is only connected to the demodulator, and the input of the demodulator is also connected to the reference signal input of the modulator through the radio frequency switch.