KR100948029B1 - Dual band power amplifier - Google Patents

Abstract

The present invention relates to a power amplifier for RF transceivers operating in the 910 MHz and 2.45 GHz band, and more particularly, to provide an RF system-based power amplifier capable of maintaining isolation of each band in two bands of 910 MHz and 2.45 GHz. will be.

The power amplifier for an RFID transceiver of the present invention includes a matching circuit in the 910 MHz band implemented by a lumped constant element, a matching circuit in the 2.45 GHz band implemented by a distributed constant element, and a λ / 2 serial microstrip transmission line, and a microstrip transmission line. The furnace isolates the 910 MHz band from the 2.45 GHz band to improve performance degradation and circuit complexity issues caused by interference.

Power amplifier, band elimination filter, band pass filter, RFID, transmitter, transmission line

Description

Dual Band Power Amplifiers {DUAL BAND POWER AMPLIFIER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier used in a RFID system. In particular, in a RFID transceiver system, a RFT system-based dual band applying a transmission line to a power amplifier to prevent interference between carrier signals in transmitting a carrier signal in two frequency bands. It relates to a power amplifier.

In general, radio frequency identification (hereinafter referred to as RFID) is a non-contact recognition system that transmits and processes information of an object and an environment using a small semiconductor chip. It has been evaluated as a technology that replaces a bar code because it does not need it. It is also known as Dedicated Short Range Communication (DSRC) or wireless identification system.

In addition, a radio frequency identification system composed of a reader having a reading and decoding function and an RF tag having embedded unique information, operating software, a network, and the like processes information by identifying a tag having a flat surface attached to an object.

Here, the RF tag is composed of a semiconductor transponder chip (Transponder Chip) and the antenna, and is divided into passive and active, passive type is a system that operates by receiving energy from the radio signal of the reader without an internal power supply. Active, built-in RF tag battery for self-operation.

The RFID is a database having an RF tag attached to an object, a reader for reading or writing identification information held by the RF tag, and a function for storing information read from the reader. Database) and a network, which is a wireless communication network composed of each component.

1 is a block diagram schematically illustrating an RFID system to which a general power divider is applied. As shown in the figure, the RFID system 100 includes a transmitter (TX, 110) and a receiver (RX, 120).

The transmitter 110 includes a voltage controlled oscillator 111, a low pass filter 112, a power divider 113, a switch 114, a power amplifier 115, and a low pass filter 116. )

Here, the voltage controlled oscillator (VCO) 111 is a device capable of outputting a desired oscillation frequency with an externally applied voltage. The apparatus assigns a channel and assigns a frequency to a radio frequency (RF) or an intermediate frequency (IF). It acts as a local oscillator to convert to and generates a carrier that supplies power to the RF tag.

In addition, a low pass filter 112 is provided to remove harmonic components generated by the voltage controlled oscillator 111, and a power divider (PD) 113 is provided in the receiver 120. To send signals to a mixer (Mixer) 125 and a power amplifier (115).

In addition, the switch 114 is provided so that the carrier wave is not output to the power amplifier 115, the power amplifier 115 forms a signal input by the operation of the switch 114 to the required power level, low-pass filter A low pass filter (LPF) 116 is provided to remove harmonic components generated by the power amplifier 115, and an antenna is provided to transmit a signal passing through the low pass filter 116 to the RF tag. .

Meanwhile, the receiver 120 includes a band pass filter (BPF) 121, a low noise amplifier (LNA) 122, a low pass filter (LPF) 123, and a power divider (PD); 124, a mixer 125, a low pass filter (LPF) 126, an amplifier 127, a low pass filter (LPF) 128, and an A / D converter (ADC; Analog to Digital) Converter 129).

Here, the band pass filter 121 is provided to pass only the signal received through the antenna of the transmitter 110, that is, the modulated RF tag information, and the low noise amplifier 122 passes through the band pass filter 121. Since the input signal contains noise, it is provided to minimize noise and to amplify only a signal for modulated RF tag information.

In addition, the low pass filter 123 is provided to remove the harmonic components generated by the low noise amplifier 123, the power divider 124 is a quadrature division scheme of the signal input through the low pass filter 123 It is provided for distributing to I channel and Q channel.

In addition, the mixer 125 is provided to convert the distributed signal to a low frequency and mix, and the low pass filter 126 is provided to remove harmonic components generated in the mixed signal.

The amplifier 127 is provided to amplify the converted low signal, and once again passes the low pass filter 128 to remove harmonic components.

Then, the A / D converter 129 is provided to convert the analog signal into a digital signal, the digital signal passed through it is input to the CPU 140 to identify and process the information in the RF tag The processed information reads the data (DB) 150 built into the computer server through the interface.

FIG. 2 is a diagram illustrating the power amplifier of FIG. 1. As shown in the figure, the power amplifier 115 of the transmitter 110 processes the frequency of one band.

Conventional dual band power amplifiers include a method for switching several transceivers, a multiband amplifier using an ultra wideband amplifier, a bias control method for transistors, and a matching method for switching a matching circuit using a diode. .

However, switching multiple transceivers increases the size of the system, and when implemented in a wide band, it is difficult to obtain characteristics of the entire band. In addition, when implemented in other bands, it is difficult to obtain characteristics of the entire band. Consideration should also be given to the limitations associated with implementing unwanted and bias control circuits caused by other bands. The method of controlling the bias of the transistor requires an additional bias control circuit and it is difficult to obtain desired characteristics in the bias control range.

Disclosure of Invention The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an RDF system-based power amplifier capable of processing a dual band using one transistor.

Another object of the present invention is to implement a system having an excellent isolation of each band by configuring a λ / 2 serial microstrip transmission line operating as a band rejection filter for the 910MHz band and a bandpass filter in the 2.45GHz band. The purpose is to provide a dual-band power amplifier based on the RF system.

The dual band power amplifier according to the present invention for solving the above problems is a first input transmission line to which an input signal having a first frequency is applied, and cuts the input signal having the first frequency and has an input signal having a second frequency. A second input transmission line for passing through an amplifier, an amplifier for amplifying the power of a signal input to the first input transmission line and the second input transmission line, and a first output for outputting an output signal having a first frequency output from the amplifier And a second output transmission line for blocking an output signal having the first frequency output from the transmission line and the amplifier and outputting an output signal having a second frequency, wherein the second input transmission line and the second output transmission line Is characterized by consisting of a λ / 2 series microstrip transmission line.

The first input transmission line includes a lumped constant element matching circuit used for impedance matching in the first input transmission line.

The second input transmission line further includes a microstrip impedance matching circuit used for impedance matching in the second input transmission line.

The λ / 2 series microstrip transmission line of the second input transmission line and the microstrip impedance matching circuit are connected in series, and the length of the λ / 2 series microstrip transmission line of the second input transmission line is the second frequency. It is half the size of the input signal wavelength.

The first input transmission line and the second input transmission line are connected in parallel.

The first output transmission line includes a lumped constant element matching circuit used for impedance matching in the first output transmission line.

The second output transmission line further includes a microstrip impedance matching circuit used for impedance matching in the second output transmission line.

The λ / 2 series microstrip transmission line of the second output transmission line and the microstrip impedance matching circuit are connected in series, and the length of the λ / 2 series microstrip transmission line of the second output transmission line is the second frequency. It is half the size of the output signal wavelength.

The first output transmission line and the second output transmission line are connected in parallel.

The dual band power amplifier according to the present invention configured as described above uses a power amplifier including a series microstrip transmission line operating as a band elimination filter for the 910 MHz band and a bandpass filter in the 2.45 GHz band. In this case, two frequency bands are used, and each band has an isolation effect from each other.

Hereinafter, with reference to the accompanying drawings will be described specific details and embodiments of the present invention.

In order to achieve the above object, the present invention provides a power amplifier for an RFID transceiver for RF communication, a matching circuit using a lumped constant element in the 910MHz band, a matching circuit using a distribution integer element in the 2.45GHz band and two frequency bands It includes a λ / 2 series microstrip transmission line that isolates the matching circuit.

Here, the λ / 2 serial microstrip transmission line operates as a band rejection filter in the 910 MHz band, thereby isolating two frequency bands by suppressing a signal flowing into a 2.45 GHz matching circuit. This reduces the performance degradation and the complexity of the circuit. In general, a microstrip transmission line consists of a metal pattern and a dielectric supporting it.

3 is a block diagram schematically illustrating a power amplifier using a λ / 2 series microstrip transmission line according to the present invention. The power amplifier 300 of FIG. 3 used a MOSFET (MRF281SR1).

The power amplifier 300 has an input terminal connected to a lumped constant element matching circuit 310 for impedance matching between terminals in a 910 MHz RFID transmission signal and a distributed constant element matching circuit 320 for impedance matching in a 2.45 GHz RFID transmission signal. . In addition, the power amplifier 300 is an output terminal connected to the lumped constant element matching circuit 330 for impedance matching between the terminals in the 910MHz RFID transmission signal and the distribution constant element matching circuit 340 for impedance matching in the 2.45GHz RFID transmission signal Has The power amplifier 300 is powered by the power supply terminal VDD. Among the signals supplied by the power supply terminal, the RF signal is removed by the RFC element.

Filter circuits 350 and 360 are connected in series to an input / output terminal to which a 2.45 GHz RFID signal is input / output. The filter circuits 350 and 360 isolate the transmission signal of the 900 MHz band in the microstrip transmission line.

FIG. 4 is a design diagram illustrating the power amplifier of FIG. 3. As shown in the figure, the power amplifier 400 using the λ / 2 series microstrip transmission line according to the present invention has matching circuits 410, 420, 430, respectively, for input and output transmission lines divided on both sides for matching. And 440.

In order to isolate the signal from the input and output transmission signals of 900 MHz in the 2.45 GHz input and output transmission lines, a λ / 2 serial microstrip transmission line is inserted.

In addition, the overall size of the power amplifier 400 using the λ / 2 series microstrip transmission line according to the present invention is about 70mm X 40mm, consisting of a dual band and amplified signal and at the same time in series with the 2.45GHz input, output transmission line The microstrip transmission lines 450 and 460 operate openly for signals in the 900 MHz band other than the desired frequency of 2.45 GHz to form an easy matching circuit configuration and high isolation.

In Fig. 4, the stabilization resistor 470 is a resistor for improving the stability of the MOSFET power amplifier. This stabilization resistor is connected to the gate terminal of the MOSFET, which compensates for the very low input / output impedance of the MOSFET power amplifier and unstable characteristics at low frequencies. In FIG. 4, the blocking capacitor 480 blocks a DC signal flowing into the input / output terminal of the power amplifier. RFC 490 removes the RF signal from the power signal supplied to the power amplifier.

FIG. 5 is a design diagram of a λ / 2 series microstrip transmission line of the power amplifier of FIG. 4.

The microstrip filter circuit of the present invention is inserted into the input / output terminal of the matching circuit using a distribution constant element. It consists of a λ / 2-length microstrip transmission line at 2.45 GHz and can isolate the 910 MHz frequency into the frequency-sensitive microstrip matching circuit.

FIG. 6 is a graph illustrating a simulation result of the serial microstrip transmission line of FIG. 5. As shown in the figure, the λ / 2 serial microstrip transmission line according to the present invention was designed and implemented through Agilent's Advanced Design System (ADS) program. In the figure, S (1,1) Is a signal reflected from the input terminal P1 to the input terminal P1, and S (2,1) is a signal output from the input terminal P1 to the first output terminal P2. The reflection coefficient at 910 MHz is -8.67 dB and the reflection coefficient at 2.45 Ghz is -34.52 dB.

Here, it can be seen that the desired frequency has a characteristic of passing in the 2.45Ghz and cut off in the 900MHz band.

In the above described exemplary embodiments of the present invention by way of example, the scope of the present invention is not limited only to this specific embodiment and those skilled in the art within the scope of the claims of the present invention Changes may be made as appropriate.

1 is a block diagram schematically showing an RFID system to which a general power amplifier is applied;

2 is a view showing the power amplifier of FIG.

3 is a block diagram schematically illustrating a power amplifier using a serial microstrip transmission line;

4 is a schematic view of the power amplifier of FIG.

5 is a schematic diagram of a series microstrip transmission line of the power amplifier of FIG.

FIG. 6 is a graph illustrating a simulation result of the serial microstrip transmission line of FIG. 5.

           <Explanation of symbols on main parts of the drawings>

400: power amplifier 410, 420: input matching circuit

450, 460: serial microstrip transmission line 430, 440: output matching circuit

470: stabilization resistor 480: blocking capacitor

Claims (11)

A first input transmission line to which an input signal having a first frequency is applied; A second input transmission line for blocking the input signal having the first frequency and passing the input signal having the second frequency; An amplifier for amplifying the power of the signal input to the first input transmission line and the second input transmission line; A first output transmission line through which an output signal having a first frequency output from the amplifier is output; And And a second output transmission line for outputting the output signal having the second frequency and blocking the output signal having the first frequency output from the amplifier, The first input transmission line includes a lumped constant element matching circuit used for impedance matching in the first input transmission line, And the second input transmission line and the second output transmission line comprise a λ / 2 series microstrip transmission line. delete The method according to claim 1, And the second input transmission line further comprises a microstrip impedance matching circuit used for impedance matching in the second input transmission line. The method according to claim 3, And a λ / 2 series microstrip transmission line of the second input transmission line and the microstrip impedance matching circuit are connected in series. The method according to claim 3, And the length of the λ / 2 series microstrip transmission line of the second input transmission line is half the wavelength of the second frequency input signal. The method according to claim 1, And the first input transmission line and the second input transmission line are connected in parallel. The method according to claim 1, And wherein the first output transmission line comprises a lumped constant element matching circuit used for impedance matching in the first output transmission line. The method according to claim 1, And the second output transmission line further comprises a microstrip impedance matching circuit used for impedance matching in the second output transmission line. The method of claim 8, And the λ / 2 series microstrip transmission line of the second output transmission line and the microstrip impedance matching circuit are connected in series. The method of claim 8, And the length of the λ / 2 series microstrip transmission line of the second output transmission line is half the wavelength of the second frequency output signal. The method according to claim 1, And the first output transmission line and the second output transmission line are connected in parallel.

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