TWI516063B - Ask modulator and transmitter having the same - Google Patents

Description

Amplitude shift key modulator and transmitter including the amplitude shift key modulator

The present invention relates to an amplitude shift keying (ASK) modulator in a radio frequency identification (RFID) system, and more particularly to an amplitude shift key modulator included in an RFID system. launcher.

RFID technology has been widely used in a variety of applications, such as electronic payment, security and inventory. A typical RFID system includes a reader, a tag, and a database platform.

ASK is the most common way to communicate with RFID. FIG. 1A illustrates an ASK modulation method. Referring to FIG. 1A, a signal S1 having an amplitude "A" can be modulated into a signal S2 having an amplitude "B". A key parameter of the so-called modulation depth in ASK modulation is defined as follows: modulation depth = . 100%. In general, the modulation depth must be higher than 90%. If not, there may be electromagnetic radiation problems.

FIG. 1B illustrates another ASK modulation method. Referring to Fig. 1B, a signal S3 having an amplitude "A'" can be modulated into a signal S4 having an amplitude "B'", and B' = 0 in this example. In this example, the modulation depth according to the above formula is 100%, so-called On-off keying (OOK). In this case, an external tag may not work because the received signal S4 has no power to activate the tag. Therefore, it is very important to control this modulation depth in an RFID system.

Figure 1C is a schematic diagram of a conventional ASK modulator. Referring to FIG. 1C, an ASK modulator 1 includes an oscillator 10, a buffer amplifier 11, a modulation device 12, a bandpass filter 13, an antenna 14, and a low pass filter 15. Tune The variable device 12 further includes a p-intrinsic-n (PIN) diode modulator 121, a power amplifying circuit 122 and a voltage-current converting circuit 123.

The PIN diode modulator 121 inevitably generates noise or spurious radiation components amplified by the power amplifying circuit 122. Therefore, the bandpass filter 13 for eliminating unwanted noise or parasitic radiation components is indispensable for the ASK modulator. Furthermore, the low pass filter 15 can receive a digital signal from a terminal "a" and generate an analog signal to control the modulation device 12, which represents the modulation device 12 can be only two voltage levels (ie, high (VDD). ) and low (ground) level control. Therefore, the low pass filter 15 is a key component in the ASK modulator 1. However, the use of the low pass filter 15 and the band pass filter 13 increases the cost of the ASK modulator 1.

Moreover, the PIN diode (not shown) of the PIN diode modulator 121 is an active component that causes a noise signal. However, these unwanted noise signals may not be cancelled by the power amplifying circuit 122 but amplified.

In addition, a PIN diode may not be integrated into a wafer with other electronic components of an ASK modulator. Figure 1D is a schematic illustration of a conventional ASK modulator 1'. Referring to FIG. 1D, the ASK modulator 1' includes an oscillator 10', a buffer amplifier 11', a control circuit 16', a PIN diode modulator 121', a power amplifier 122' and an antenna 14. '. Control circuit 16' may include a micro control unit (not shown) and/or a digital processor (not shown). The buffer amplifier 11', the control circuit 16' and the power amplifier 122' can be integrated into a wafer to form an integrated circuit (IC) 17'. As shown in FIG. 1D, the IC 17' has five pins t1, t2, t3, t4 and t5, wherein the pin t1 receives the carrier signal from the oscillator 10'; the pin t2 connects the output of the buffer amplifier 11'. To the PIN diode modulator 121'; the pin t3 is used to transmit a control signal to the PIN diode modulator 121'; the pin t4 is connected to the PIN diode modulator 121' to the power amplifier 122' The input terminal; and the pin t5 are connected to the output end of the power amplifier 122' to the antenna 14'. The additional pins t2 and t4 of IC 17' can cause more harmonic or spurious signals and also increase the packaging cost of the ASK modulator 1'.

Therefore, it is necessary to provide a cost-effective adjustment using a simplified circuit. Transformer.

An example of the present invention may provide a modulator having a first terminal for receiving a carrier signal, and a second terminal for receiving a first control signal to control a frequency band of the carrier signal, and a first The three terminals are configured to receive a second control signal to control a modulation depth of the carrier signal.

Some examples of the present invention may also provide a transmitter, the transmitter includes a carrier generator for generating a carrier signal, an amplifying circuit having an input terminal connected to the carrier generator, and a first terminal connection a modulator to an output of the amplifier circuit; and an antenna having an input coupled to the modulator.

Some examples of the present invention may also provide a modulator comprising a variable resistor provided with a voltage level; a switch connected in series to the variable resistor; and a parallel connection to the switch a resistor; a second resistor connected in series to the first resistor; a first inductor having a first terminal coupled to the second resistor and a second for receiving a carrier signal a terminal; a PIN diode having an anode connected to the second terminal of the first inductor; and a cathode for outputting a modulated signal; and a second inductor having a connection The first terminal of the cathode of the PIN diode and a second terminal, wherein the second terminal is grounded.

Other features and advantages of the invention will be set forth in part in the description in the description. The features and advantages of the present invention will be understood and attained by the <RTIgt;

It is to be understood that the foregoing general descriptions

Reference will now be made in detail to the embodiments of the invention, Wherever possible, the same reference numerals will be used to refer to the

2A is a block diagram of a transmitter 2 in an RFID system in accordance with one example of the present invention. Referring to FIG. 2A, the transmitter 2 can include a micro control unit (MCU) 21, a digital processor 22, a carrier generator 23, a buffer amplifier 24, a power amplifier 25, and a modulator 26. With an antenna 27.

The digital processor 22 is connectable to the MCU 21. The carrier generator 23 can be connected to a buffer amplifier 24, which in turn is connected in series to the power amplifier 25. Modulator 26 can be coupled between power amplifier 25 and antenna 27. The modulator 26 can also have two terminals "T1" and "T2", both of which are coupled to the digital processor 22.

The carrier generator 23 can generate a signal TS1 of frequency f _ts1 , which can then be transmitted to the buffer amplifier 24 . The buffer amplifier 24 can receive the signal TS1, then amplify the voltage of the signal TS1, and thereby output an amplified signal TS2, which can be transmitted to the power amplifier 25. The power amplifier 25 amplifies the power of the signal TS2 and outputs an amplified signal TS3 to the modulator 26. In an example, the frequency f _ts1 can be, but is not limited to, approximately 433.92 megahertz (MHz), and the amplifiers 24 and 25 can linearly amplify the signals TS1 and TS2. In another example, the frequency f _ts1 can be, but is not limited to, approximately 915 MHz.

The modulator 26 can receive the signal TS3 from the power amplifier 25 and output a modulated signal TS4 to the antenna 27. The digital processor 22, which is controllable by the MCU 21, generates control signals and transmits the control signals to the terminal T1 and/or the terminal T2 to control the frequency band and/or modulation depth of the signal TS4. In another example, terminal T2 is not necessarily connected to digital processor 22 but can be connected to a direct current (DC) voltage source. The harmonic or spurious signals that may be caused by the modulator 26 are not amplified because the modulator 26 is disposed in the next stage of the power amplifier 25. Therefore, the harmonic or spurious signals caused by the modulator 26 can be minimized to improve the transmission quality.

Still referring to FIG. 2A, the MCU 21, the digital processor 22, the buffer amplifier 24, and the power amplifier 25 can be added to an integrated circuit (IC) 28 in another example. The IC 28 may include a pin t5 for receiving the signal TS1 from the carrier generator 23 and another pin t6 connectable to a terminal T3 of the modulator 26 for transmitting the signal TS3. IC 28 may also include pins t7 and t8 that may be coupled to terminals T2 and T1 of modulator 26 to transmit control signals. By means of the circuit configuration of the transmitter 2, in a conventional modulator, an output pin for connecting the buffer amplifier to an additional pin of the modulator (refer to pin t2 shown in FIG. 1D), and The additional pins that connect the modulator to the input of the power amplifier (see pin t4 shown in Figure 1D) are eliminated in IC 28. The reduced number of pins advantageously minimizes such harmonic or spurious signals and also saves on the packaging cost of the IC 28. Furthermore, the modulator 26 is controlled by a digital signal from the MCU 21 or the digital processor 22, and thus is used to convert a digital signal into a low-pass filter of an analog signal (see the low-pass filter 15 shown in FIG. 1C). Can also be excluded. In another example, MCU 21 and digital processor 22 can be integrated into a control circuit (not shown).

2B further illustrates a block diagram of the modulator 26 of FIG. 2A in accordance with an example of the present invention. Referring to FIG. 2B, the modulator 26 can include a variable resistor VR, two resistors R1 and R2, two inductors L1 and L2, a switch SW, a diode 261, and a transistor Q1.

The variable resistor VR can have a terminal connected to a voltage terminal VDD that supplies a direct current (DC) voltage level. The other terminal of the variable resistor VR is connectable to the resistor R1 and the switch SW connected in parallel. The switch SW can be connected to the terminal T1 and then to the digital processor 22. In this example, the switch SW can include, but is not limited to, a transistor. The resistor R2 can be connected in series to the resistor R1 and the inductor L1. The inductor L1 may have one end connected to the output of the power amplifier 25 and the anode of the diode 261 (ie, the terminal T3). The inductor L2 may have a terminal (i.e., terminal T4) connected to the cathode of the diode 261 and the antenna 27, and another terminal grounded. The transistor Q1 can have a first terminal connected to the terminal T2. The transistor Q1 There may be a second terminal and a third terminal, and the resistor R2 is connectable between the second and third terminals of the transistor Q1. In one example, the transistor Q1 can be, but not limited to, a complementary metal-oxide-semiconductor (CMOS) transistor. In another example, the diode 261 can be, but is not limited to, a PIN (p-intrinsic-n) dipole.

FIG. 3A illustrates a modulation method in accordance with an example of the present invention. Referring to FIG. 3A, a control signal CS1 from the digital processor 22 can be transmitted to the terminal T1 (refer to FIG. 2B) to turn the switch SW on/off. In this example, when the control signal CS1 is relatively low, the switch SW is off (open circuit), and the modulator 26 can perform the ASK modulation. In other words, the digital processor 22 can determine whether the modulator 26 is to perform the ASK modulation. When the control signal CS1 is relatively high, the switch SW is turned on (closed loop), and the modulator 26 can stop performing the ASK modulation. The digital processor 22 can transmit a control signal and control the frequency band of the signal TS4 in this manner.

Still referring to FIG. 3A, another control signal CS2 from the digital processor 22 can be transmitted to the terminal T2 (please refer to FIG. 2B) to change the modulation depth of the signal TS4. In this example, the control signal CS2 is relatively low, and the modulator 26 can perform ASK modulation with a 75% modulation depth.

FIG. 3B illustrates a modulation method in accordance with an example of the present invention. Referring to Fig. 3B, a control signal CS1' from the digital processor 22 can be transmitted to the terminal T1 (refer to Fig. 2B) to turn the switch SW on/off. In this example, when the control signal CS1' is relatively low, the switch SW is off (open circuit) and the modulator 26 can perform the ASK modulation. In other words, the digital processor 22 can determine whether the modulator 26 is to perform the ASK modulation. When the control signal CS1' is relatively high, the switch SW is open (closed loop), and the modulator 26 can stop performing the ASK modulation. The digital processor 22 can control the frequency band of the signal TS4 in this manner.

Still referring to FIG. 3B, another control signal CS2' from the digital processor 22 or from an external device can be transmitted to the terminal T2 (please refer to FIG. 2B) to change the The modulation depth of the signal TS4. In this example, when the control signal CS2' is relatively low, and the modulator 26 can perform ASK modulation with a 75% modulation depth. When the control signal CS2' is relatively high, and the modulator 26 can perform ASK modulation with a 50% modulation depth. The modulation depth may not be limited to the above, but may be changed in other examples.

Referring back to FIG. 2B, in an example, the resistance of the variable resistor VR ranges from 10 Ω to 50 kΩ, and the resistance of each of the resistors R1 and R2 is 10 kΩ, and each of the inductors L1 and L2 One has an inductance of 100 nH (Nano-Henry). However, the values of the above resistance and inductance can be varied in another example to change the modulation depth.

Those skilled in the art should be aware that changes can be made to the above examples without departing from the broad inventive concepts. Therefore, it is understood that the invention is not limited to the specific examples of the invention, but is intended to cover the modifications of the invention and the scope of the invention as defined by the appended claims.

In addition, in describing a representative example of the present invention, the present specification may represent the method and/or process of the present invention as a specific sequence of steps; however, since the scope of the method or process is not specific to the particulars set forth herein The order of the steps, so the method or process should not be limited to the particular order of steps described. It is also possible to be familiar with the sequence of other steps as a person skilled in the art. Therefore, the specific order of steps set forth in this specification should not be construed as limiting the scope of the application. In addition, the scope of application for the method and/or process of the present invention should not be limited to the implementation of the order of the steps in the written form, which is readily understood by those skilled in the art, and the order may be changed and still It is intended to be within the spirit and scope of the invention.

1‧‧‧ASK modulator

1'‧‧‧ASK modulator

2‧‧‧transmitter

10‧‧‧Oscillator

10’‧‧‧Oscillator

11‧‧‧Buffer amplifier

11'‧‧‧Buffer amplifier

12‧‧‧Transformation device

13‧‧‧Bandpass filter

14‧‧‧Antenna

14’‧‧‧Antenna

15‧‧‧Low-pass filter

16’‧‧‧Control circuit

17'‧‧‧ Integrated circuit

21‧‧‧Micro Control Unit

22‧‧‧Digital Processor

23‧‧‧Carrier generator

24‧‧‧Buffer amplifier

25‧‧‧Power Amplifier

26‧‧‧Transformer

27‧‧‧Antenna

28‧‧‧Integrated circuit

121‧‧‧p-type essential n-type (PIN) diode modulator

121'‧‧‧p-type essential n-type (PIN) diode modulator

122‧‧‧Power amplifier circuit

122'‧‧‧Power Amplifier

123‧‧‧Voltage-current conversion circuit

261‧‧‧ diode

The foregoing summary of the invention, as well as the above detailed description For the purposes of illustration of the present invention, various drawings are illustrated in the drawings. However, it should be understood that the invention is not limited to the precise arrangements and devices disclosed. In the drawings: FIG. 1A illustrates an ASK modulation mode; FIG. 1B illustrates another ASK modulation mode; FIG. 1C is a schematic diagram of a conventional ASK modulator 1; FIG. 1D is a conventional ASK modulator 1' 2A is a block diagram of a transmitter 2 in an RFID system according to an example of the present invention; and FIG. 2B is another block diagram of the modulator 26 shown in FIG. 2A according to an example of the present invention; FIG. 3A illustrates A modulation mode according to an example of the present invention; FIG. 3B illustrates a modulation mode according to an example of the present invention.

2‧‧‧transmitter

21‧‧‧Micro Control Unit

22‧‧‧Digital Processor

23‧‧‧Carrier generator

24‧‧‧Buffer amplifier

25‧‧‧Power Amplifier

26‧‧‧Transformer

27‧‧‧Antenna

28‧‧‧Integrated circuit

Claims (18)

An amplitude shift key modulator in a radio frequency identification system, comprising: a first terminal for receiving a carrier signal; and a second terminal for receiving a first control signal to determine whether the carrier signal is executed An amplitude shift key is modulated to control a frequency band of the carrier signal; a third terminal is configured to receive a second control signal to control an amplitude shift key modulation depth of the carrier signal; and a PIN diode, It has an output connected to an amplifying circuit and an anode of the second terminal, and a cathode connected to an antenna. The modulator of claim 1, wherein the second terminal and the third terminal are connected to a control unit. The modulator of claim 1, wherein the third terminal is connected to a direct current (DC) voltage source. The modulator of claim 2 or 3, wherein the modulator further comprises a carrier generator, and the amplifying circuit is connected between the carrier generator and the first terminal of the modulator, wherein The modulator has a fourth terminal coupled to the antenna. The modulator of claim 4, wherein the modulator comprises: a variable resistor provided with a voltage level; a switch connected in series to the variable resistor and electrically coupled To the second terminal of the modulator; a first resistor connected in parallel to the switch; a second resistor connected in series to the first resistor; a first inductor having a connection a first terminal of the second resistor, and a second terminal connected to an output end of the amplifying circuit, and the anode of the PIN diode is connected to the second terminal of the first inductor; and a a second inductor having a first terminal and a second terminal connected to the cathode of the PIN diode, wherein the second terminal is grounded. The modulator of claim 5, further comprising a transistor having a first terminal, a second terminal and a third terminal connected to the third terminal of the modulator, The second resistor is connected between the second and third terminals of the transistor. A modulator according to claim 6 wherein the transistor is a complementary metal oxide semiconductor (CMOS) transistor. The modulator of claim 4, wherein the amplifying circuit comprises a buffer amplifier. A modulator according to claim 8 wherein the amplifying circuit comprises a power amplifier connected in series to the buffer amplifier. A transmitter including an amplitude shift key modulator in a radio frequency identification system, comprising: a carrier generator for generating a carrier signal; an amplifying circuit having an input terminal connected to the carrier generator; a modulator having a first terminal connected to an output of the amplifying circuit for receiving a first control signal to determine whether the carrier signal performs an amplitude shift key modulation to control the carrier signal a second terminal of the frequency band, and a third terminal for receiving a second control signal for controlling an amplitude shift key modulation depth of the carrier signal; an antenna having an input connected to the modulator And a PIN diode having an output connected to the amplifier circuit and an anode of the second terminal, and a cathode connected to the antenna. The transmitter of claim 10, wherein the third terminal of the modulator is connected to a direct current (DC) voltage source, the DC voltage source supplying a voltage level to the third terminal of the modulator The amplitude shift key is controlled to control the amplitude of the carrier signal. The transmitter of claim 10 or 11, wherein the modulator comprises: a variable resistor provided with a voltage level; a switch connected in series to the variable resistor, and electrically a second terminal coupled to the modulator; a first resistor connected in parallel to the switch; a second resistor connected in series to the first resistor; a first inductor having a connection a first terminal to the second resistor, and a second terminal connected to the output end of the amplifying circuit, and the PIN diode An anode is coupled to the second terminal of the first inductor; and a second inductor having a first terminal and a second terminal connected to the cathode of the PIN diode, wherein the second terminal is Ground. A modulating device comprising: a variable resistor provided with a voltage level; a switch connected in series to the variable resistor; a first resistor connected in parallel to the switch; a second resistor connected in series to the first resistor; a first inductor having a first terminal coupled to the second resistor; and a second terminal for receiving a carrier signal; a PIN a diode having an anode connected to the second terminal of the first inductor, and a cathode for outputting a modulated signal; and a second inductor having a connection to the PIN diode a first terminal of the cathode and a second terminal, wherein the second terminal is grounded. A modulator according to claim 13 wherein the switch receives a first control signal to control a frequency band of the carrier signal. The modulator of claim 14, wherein the modulator further comprises a transistor having a first terminal, a second terminal and a third terminal, wherein the second resistor is connected to the Between the second and third terminals. The modulator of claim 15 wherein the first terminal of the transistor receives a second control signal to control a modulation depth of the carrier signal. The modulator of claim 13 wherein the anode of the PIN diode and the second terminal of the first inductor are coupled to an output of a power amplifier. The modulator of claim 13, wherein the cathode of the PIN diode is connected to an antenna.