CN103279777A - Wireless surface acoustic wave temperature measurement system reader-writer - Google Patents

Abstract

The invention discloses a reader/writer of a wireless surface acoustic wave temperature measurement system, which comprises a signal generation unit 101, an amplification unit 102, a band-pass filter 103, a radio frequency switch 104, a crystal oscillator 105, a local oscillator 106, and a band-pass filter 107 , a low noise amplifier 108 , a filter 109 , an intermediate frequency amplifier 110 , an analog-to-digital conversion module 111 , and a digital signal processing module 112 . The reader/writer adopts a double phase-locked loop structure, which ensures that the transceiver reaches the desired frequency and provides a guarantee for accurate temperature measurement.

Description

A wireless surface acoustic wave temperature measurement system reader

technical field

The invention belongs to the cross application of wireless radio frequency technology and surface acoustic wave technology, in particular to a wireless surface acoustic wave temperature measuring circuit and a surface acoustic wave radio frequency identification reader-writer based on DSP technology.

Background technique

Surface acoustic wave (SAW) is a mechanical wave propagating on the surface of piezoelectric crystal, its sound speed is only one hundred thousandth of the electromagnetic wave speed, and the propagation attenuation is very small. Through the interdigital interchanger, the electrical signal is converted into an acoustic signal, and it is limited to spread on the surface of the substrate. It is used in the measurement of pressure, temperature and other parameters with high accuracy, such as a publication with the publication number CN202305058U A resonant SAW temperature sensor automatic test system, this test system is huge and complex, and cannot test multiple sensors at the same time. Temperature reader, there is still no related technology disclosure of wireless surface acoustic wave temperature measurement reader at present; Another example is a kind of improved UHF RFID reader whose publication number is CN102622571A, although this reader has a far operating distance , but its encoding method is only used to identify information, and cannot achieve the function of measuring temperature. For this reason, we hope to provide a wireless surface acoustic wave temperature measurement system reader that can accurately measure multiple sensors at the same time.

Contents of the invention

In view of the above shortcomings of the prior art, the object of the present invention is to provide a reader-writer for a wireless surface acoustic wave temperature measurement system, so that multiple readers are not needed when measuring multiple sensors, and the accuracy of temperature detection is improved.

The purpose of the present invention is achieved by the following means:

A wireless surface acoustic wave temperature measurement system reader, characterized in that it consists of a signal generation unit 101, an amplification unit 102, a band-pass filter 103, a radio frequency switch 104, a crystal oscillator 105, a local oscillator 106, and a band-pass filter 107, low noise amplifier 108, filter 109, intermediate frequency amplifier 110, analog-to-digital conversion module 111, digital signal processing module 112 constitute; wherein crystal oscillator 105 produces the most original reference frequency, and frequency is sent to signal generating unit 101 and this machine simultaneously Oscillator 106, the frequency processed by the signal generation unit passes through the amplification unit 102 and the band-pass filter 103, and transmits the inquiry signal through the radio frequency switch 104; the radio frequency switch 104 receives the response signal sent back by the front-end sensor, and sends the response signal to the band-pass The filter 107 is amplified by the preamplifier 108, and mixed with the frequency sent by the local oscillator 106 before, and the mixed signal is passed through the intermediate frequency amplifier 110, and then the signal is sent to the analog-to-digital conversion module 111 and The digital signal processing module 112 performs processing to obtain the temperature value.

Using the device of the present invention, the crystal oscillator 105 produces the most original reference frequency, and the frequency is sent to the signal generation unit 101 and the local oscillator 106 at the same time, and the frequency processed by the signal generation unit passes through the amplification unit 102 and the bandpass filter 103, The inquiry signal is transmitted by the radio frequency switch 104; the radio frequency switch 104 receives the response signal sent back by the front-end sensor, sends the response signal to the bandpass filter 107, and then amplifies it through the preamplifier 108, which is the same as the frequency sent by the local oscillator 106 before. Perform frequency mixing processing, pass the mixed signal through the intermediate frequency amplifier 110, and then send the signal to the analog-to-digital conversion module 111 and the digital signal processing module 112 for processing to obtain the temperature value.

The RF switch chip is connected to the receiving module and the transmitting module at the same time to form an independent receiving and transmitting gate; the RF switch chip is connected to the multi-channel antenna expansion circuit at the same time to maintain the linearity of the signal; the low-noise amplifier used in the preamplifier module is connected to the RF switch module band-pass filter; the amplified signal output by the low noise amplifier enters the intermediate frequency amplifier; the information is transmitted to the DSP for processing through the intermediate frequency amplifier; in the sending module, the reference frequency is amplified and filtered and then connected to the RF switch; at the same time, the reference frequency is also passed through this The machine oscillator is mixed with the received signal to ensure the accuracy; the RF switch is connected to multiple antenna terminals, and each antenna can be connected to multiple sensors to measure the temperature of multiple points at the same time.

Working principle of the present invention:

The crystal oscillator 105 generates the most original reference frequency, and sends the frequency to the signal generation unit 101 and the local oscillator 106 at the same time, and the frequency processed by the signal generation unit passes through the amplification unit 102 and the band-pass filter 103, and transmits the inquiry through the radio frequency switch 104 signal; the radio frequency switch 104 receives the response signal sent back by the front-end sensor, sends the response signal to the bandpass filter 107, and then amplifies it through the preamplifier 108, and performs mixing processing with the frequency sent by the previous local oscillator 106, and the The mixed signal passes through the intermediate frequency amplifier 110, and then sends the signal to the analog-to-digital conversion module 111 and the digital signal processing module 112 for processing to obtain a temperature value.

First of all, the local oscillator is generated by two phase-locked loops with high stability, and plays an important role in the entire circuit as a reference for transmitting inquiry signals and detecting response signals.

Secondly, in the transmitting module, the crystal oscillator 105 generates the most original reference signal, the signal generation unit 101 intercepts the required pulse width, up-converts the frequency, and then amplifies and filters to obtain the pulse, and then transmits it from the antenna through the pre-power amplifier , forming an interrogation signal.

Next, in the receiving module, the RF switch is set to the waiting state, and the time is selected to be 1.2-2us. After the response signal reaches the receiving module, it first passes through the bandpass filter 107 for filtering processing. After the filtering processing, the signal is amplified by the RF amplifier 108. , which is a low-noise amplifier. After radio frequency filtering and amplification, the signal is down-converted with the local oscillator 106; The amplified H signal is sent to DSP for calculation after analog-to-digital conversion, and the temperature value t is calculated by formula (1).

t=(f _r -f _s )／S _k +t ₀ (1)

Where t ₀ is the reference temperature value, _fr is the received response frequency value with frequency offset, f _s is the frequency of the search signal sent out, S _k is the frequency offset temperature characteristic of the SAW sensor (according to different sensor characteristics, for example There is 7K=1℃).

The RF switch belongs to single pole double throw (SPDT), the selection time is 1.2-2us, the high level selects the transmission, the low level selects the receiving signal, maintains linearity, and provides isolation between the transmission and reception chains, while achieving the smallest possible insertion loss.

Before mixing, through the phase-locked loop structure shown in Figure 2, a stable and ideal mixing frequency is obtained. What enters the phase-locked loop is a stable reference source that is the same as the transmitter, and then passes through the frequency divider and voltage Control the oscillator to obtain the expected stable mixing frequency and mix with the received signal.

Adopt above-mentioned technology, the obvious effect of the present invention is:

The multi-antenna multi-sensor mode is adopted, and each antenna terminal is externally connected with multiple sensors, and the resonant frequency of each sensor is different, which ensures that the temperature of multiple points can be measured at the same time.

Intermittent rectangular rectangular pulses are used as signal excitation to maintain linearity and provide isolation between the transmit and receive chains while achieving the lowest possible insertion loss.

The dual phase-locked loop structure is adopted to ensure the stability of the signal, while maintaining the frequency tightness of the transceiver module, which provides a stable guarantee for the separation of changing frequency components.

Multiple antenna channels are used, the main channel is selected through the radio frequency switch, and the entire reader is guaranteed to work in time-division multiplexing mode.

Description of drawings

Fig. 1 is the implementation block diagram of the reader of the wireless surface acoustic wave temperature measuring system of the present invention

Fig. 2 is the phase-locked loop structure of the reader of the wireless surface acoustic wave temperature measuring system of the present invention

Figure 3 is a schematic diagram of the working process of Figure 1

Figure 4 is a schematic diagram of the working process of Figure 2

Fig. 5 is a connection diagram of the radio frequency switch module of the reader-writer of the wireless surface acoustic wave temperature measurement system of the present invention.

Detailed ways

A specific embodiment of the present invention: a reader/writer for a wireless surface acoustic wave temperature measurement system, the reader includes a sending signal generating unit, a sending signal amplifying unit, a sending signal bandpass filter, a radio frequency switch, and a local oscillator , a received signal band-pass filter, a low noise amplifier, a filter, an intermediate frequency amplifier, an analog-to-digital conversion module, a digital signal processing module and a plurality of antenna terminals. The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the solution of the present invention consists of a transmission signal generation unit 101, a transmission signal amplification unit 102, a transmission signal bandpass filter 103, a radio frequency switch 104 (selection time 1.2-2us), a crystal oscillator 105, a local oscillator 106, A received signal bandpass filter 107, a low noise amplifier 108, a filter 109, an intermediate frequency amplifier 110, an analog-to-digital conversion module 111, and a digital signal processing module 112 are formed. Among them, the crystal oscillator 105 generates the most original reference frequency, and sends the frequency to the transmission signal generation unit 101 and the local oscillator 106 at the same time, and the frequency processed by the transmission signal generation unit passes through the transmission signal amplification unit 102 and the transmission signal bandpass filter 103 , the inquiry signal is transmitted through the radio frequency switch 104; the radio frequency switch 104 receives the response signal sent back by the front-end sensor, sends the response signal to the received signal bandpass filter 107, and then amplifies it through the preamplifier 108, and sends it to the previous local oscillator 106 The incoming frequency is mixed, and the mixed signal passes through the intermediate frequency amplifier 110, and then the signal is sent to the analog-to-digital conversion module 111 and the digital signal processing module 112 for processing to obtain the temperature value. The calculation method is shown in formula 1.

FIG. 2 is a block diagram of the transmission signal generation unit 101 in the present invention. The crystal oscillator 105 generates the most original reference frequency. The reference frequency signal is sent to the reference frequency divider 1015, and the signal is sent to the phase detector 1014. After passing through the phase detector, it passes through the loop filter 1011, and then through the voltage-controlled oscillator 1012, and then enters the feedback frequency divider 1013 to form a PLL. PLL. The generated signal is sent to the transmission signal amplifying unit 102 .

Fig. 5 is the radio frequency switch module of the wireless surface acoustic wave temperature measurement system reader of the present invention, the radio frequency switch 104 is connected in parallel with a plurality of downstream radio frequency switches to receive different response signal antenna terminals, in order to facilitate the selection of the reader signal sending and receiving direction, the radio frequency switch 104 adopts a dual-way control switch, and selects different paths for receiving and transmitting; the downstream radio frequency switches (1042, 1043, 1044) use a single-way switch, and each antenna terminal is connected to multiple front-end sensors with different sensing resonant frequencies. Each of the downstream RF switches has its own antenna, and each antenna is connected to a different sensor to achieve multi-point detection. Sensors exist independently, and different sensors have different resonance frequencies, so the reader is required to send detection signals of different frequencies on the same antenna. The downstream RF switch selects the transmitting antenna, and only one of them can be turned on at the same time. The reader can only send or receive signals from a certain antenna at the same time.

Claims (2)

1. wireless acoustic surface wave temp measuring system read write line, it is characterized in that, constituted by signal generation unit 101, amplifying unit 102, bandpass filter 103, radio-frequency (RF) switch 104, crystal oscillator 105, local oscillator 106, bandpass filter 107, low noise amplifier 108, wave filter 109, intermediate frequency amplifier 110, analog-to-digital conversion module 111, digital signal processing module 112; Wherein crystal oscillator 105 produces the most original reference frequency, simultaneously frequency is delivered to signal generation unit 101 and local oscillator 106, pass through amplifying unit 102 and bandpass filter 103 again through the frequency that the signal generation unit is handled, by radio-frequency (RF) switch 104 emission interrogation signals; The response signal that radio-frequency (RF) switch 104 receiving front-end sensors are passed back, response signal is delivered to bandpass filter 107, amplify through prime amplifier 108 again, carry out Frequency mixing processing with the frequency that local oscillator 106 is before sent here, signal after the mixing is passed through intermediate frequency amplifier 110, again signal is delivered to analog-to-digital conversion module 111 and digital signal processing module 112 is handled, obtain temperature value.

2. the surface acoustic wave temp measuring system read write line according to claim 1, it is characterized in that, it is characterized in that described radio-frequency (RF) switch 104 a plurality of downstreams in parallel radio-frequency (RF) switch receive different response signal antenna terminals, each antenna articulates all different front end sensors of a plurality of sensing resonance frequencies.

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