KR100902397B1 - The apparatus for contrlling the sensitivity by using digital gating in receiver and the receiver comprising the same - Google Patents

Abstract

An apparatus controlling receive sensitivity by using a digital gating and a receiver including the same capable of easily controlling reception sensitivity is provided to supply a chipset for a DSRC capable of one-chip by using the digital gating in the receiver. An LNA(Low Noise Amplifier)(104) amplifies radio frequency received signal. The amplified signal is inputted to a mixer(106). The mixer converts the amplified signal. IF(Intermediate Frequency) signal is outputted through frequency-down-conversion. The mixer receives an LO(Local Oscillator) frequency signal from a frequency synthesizer(108). A detector compares the output of a log amplifier with the binary threshold value.

Description

 Apparatus for adjusting reception sensitivity using digital gating in a receiver and a receiver including the same {THE APPARATUS FOR CONTRLLING THE SENSITIVITY BY USING DIGITAL GATING IN RECEIVER AND THE RECEIVER COMPRISING THE SAME}

The present invention relates to a wireless communication system. More specifically, the present invention relates to receiver and transceiver chip sets for Dedicated Short Range Communication (“DSRC”).

DSRC stands for short range communication. This refers to a communication scheme and a standard for communicating at a short distance only based on an industrial / scientific / medical (ISM) band that does not require a radio wave license and some frequencies, without long-range interference. DSRC is a method of instantaneous exchange of a large amount of information through two-way wireless communication within a distance of several to several tens of meters. It is used in a narrow area, allowing reuse of frequencies in each area.

DSRC has recently been used in the Intelligent Transportation System (ITS), and the Electronic Toll Collecting System (ETCS) has been highlighted as part of the ITS. In addition, DSRC can be used in many ways, including parking lot management, logistics delivery management, gas station payments, and car shopping.

DSRC is spreading around the world, mainly in data-vehicle-to-vehicle or vehicle-to-infrastructure data communication, especially in Asia, especially in Korea and Japan. In the country, commercial services using 5.8GHz carriers have already been applied to ETCS and ITS. At present, the installation of infrastructure for ETCS is almost completed in the national highway network, and some cities are providing traffic information service to the public by using the ITS network.

The domestic DSRC specifications are as follows.

(a) Radio transmission carrier allocation: 5800 + k * 10 MHz (mandatory: k = 0, 1, optional: k = 4, 5)

(b) Modulation / demodulation method: ASK (Amplitude Shift Keying), modulation index is over 75%

(c) Method of switching between transmit / receive mode: TDD (Time Division Duplexing)

(d) Multiple Access Technology: Frequency Division Multiplexing (FDM) + Space Division Multiplexing (SDM)

(e) Receive Sensitivity Range: -76dBm (for ITS) ~ -40dBm (for ETCS)

(f) Transmission output power: +10 dBm

(g) Support for on-board equipment (OBE) movement speed: over 160 km / h

(h) OBE temperature range: -40 ℃ ~ 85 ℃

Among the above-listed standards, the reception sensitivity range shows that the domestic DSRC standard requires -76 dBm for ITS and -40 dBm (for ETCS) for ETCS. Receive sensitivity refers to the minimum signal input level at which the receiver can operate, depending on the characteristics or performance of the receiver element. Receive sensitivity is determined based on the bit error rate (BER) and is an important measure of receiver performance.

It can be seen that in order to perform the charging normally while the OBE is moving in a narrow ETCS region at a very high speed, it has a characteristic that a very fast BER and a very fast transition time between transmission and reception modes are required. In addition, the use of SDM as a part of the multiple access technology means that unwanted interference signals may be generated from adjacent ETCS cells. Therefore, in order to prevent each other, precise transmission / reception power control is performed even within a wide temperature range. This means that it is necessary.

In DSRC, the wide range of free sensitivity control of OBE's design specifications is essential for supporting both ITS and ETCS simultaneously. In addition, in order to clearly define a communication area even within a wide temperature range, highly precise reception sensitivity is required with accurate transmission power. In particular, since the reception sensitivity in the ETCS determines whether the OBE enters the communication area as the strength of the reception power, more accurate sensitivity adjustment is required. If the reception sensitivity is less than the proper value, the OBE will try to communicate with the base station before it even enters the communication area, which may cause interference to the adjacent DSRC device. This is because the communication is performed only in a small area, thereby reducing the available communication time.

As a conventional method of adjusting reception sensitivity, a method of adjusting a gain of a receiver is used. In other words, adjusting the gain of the receiver changes the noise figure of the receiver. Using this characteristic, the maximum reception distance satisfying the BER of the receiver is adjusted.

2 is a graph illustrating the received power (P _IN ) vs. BER characteristic in a method of adjusting a reception sensitivity of a conventional receiver. In the graph of FIG. 2, the x axis represents the strength of the signal of the received signal, that is, the received power, and the y axis represents the BER of the receiver when the signal of the corresponding strength is received. Graph 201 is a BER graph of the received signal strength when the noise figure of the receiver is NF1, and graph 202 is a BER graph of the received signal strength when the noise figure of the receiver is NF2 (where NF1 < Satisfies NF2).

The receiver should operate when the received signal is greater than or equal to P _SEN1 , and if the BER is required to be less than or equal to -5 powers of 10 in the operating range, that is, when the receiver's reception sensitivity is required to be P _SEN1 , the noise figure of the receiver Must be set to NF1. Similarly, if the receiver is to be operated when the received signal is above P _SEN2 and the BER is required to be less than -5 powers of 10 in the operating range, i.e. when the receiver's reception sensitivity is required to be P _SEN2 , then The noise figure of the receiver should be set to NF2. That is, the noise figure of the receiver is changed according to the required reception sensitivity.

However, the problem of this adjustment method is that the system noise figure of the receiver is a value determined as a function of gain and noise figure of all the component circuits, so it is very difficult to adjust the noise figure linearly by adjusting the gain or noise figure of a specific circuit. It is difficult. In addition, BER, which has been obtained at the minimum input power with the maximum system performance index, is obtained by artificially deteriorating the performance of the system when the reception sensitivity is set large, and therefore, optimum performance cannot be obtained in terms of system performance. In addition, there is a problem that it is difficult to clearly define the communication distance.

On the other hand, the conventional base station terminal for DSRC is implemented in the form of a hybrid module (hybrid module) with a large manufacturing cost and a high cost, it consists of a large number of component chips and external components. Therefore, when a specific design change occurs in the DSRC base station terminal, the DSRC base station terminal is returned to the laboratory as a whole, there is an inconvenience that needs to be readjusted. And this incurs a burden of costs. In addition, the base station terminal for DSRC implemented in the form of such a hybrid module has a disadvantage that can not be integrated with chips such as GPS or DMB.

In order to solve the above problems, an object of the present invention is to provide a receiver for DSRC which is easy to adjust reception sensitivity without degrading the performance of the system.

In addition, by integrating the DSRC receiver based on the CMOS technology, it is an object to provide a DSRC chip set that can be chipped with a GPS or DMB chip.

In order to achieve the above object, a signal receiver according to an embodiment of the present invention, a low noise amplifier for amplifying a radio frequency (RF) received signal while minimizing amplification of noise included in the RF signal (Low noise) amplifier (LNA); A mixer configured to output an intermediate frequency (IF) signal by frequency-down converting the output signal of the LNA; A frequency synthesizer for generating a frequency signal for frequency down-conversion of the mixer and outputting the frequency signal to the mixer; A bandpass filter for passing only a band of a required channel among the output signals of the mixer; A log amplifier amplifying the output signal of the bandpass filter at a log scale and outputting a received signal strength indicator (RSSI) of the output signal of the bandpass filter; Compare the output of the log amplifier with a predetermined binary threshold, output a first value of a binary signal if the output of the log amplifier is less than the binary threshold, and the output of the log amplifier is A detector for outputting a second value of the binary signals when the binary threshold is greater than or equal to; A switch connected in series to the output of the detector; Compare the RSSI with a predetermined RSSI threshold, open the switch if the RSSI is below the predetermined RSSI threshold, and short the switch if the RSSI is above the predetermined RSSI threshold. and a switch controller for closing.

Here, preferably, the switch control unit comprises: an analog-to-digital converter (ADC) for converting the RSSI into a digital signal; An RSSI threshold generator for generating the RSSI threshold; And a comparator comparing the RSSI with the RSSI threshold and opening or shorting the switch.

Here, preferably, the RSSI threshold generation unit may include: a temperature sensor for measuring an ambient temperature; And a lookup table in which the RSSI threshold corresponding to the temperature measured by the temperature sensor is stored.

Here, preferably, the receiver alternately operates in a signal reception mode (Rx mode) for receiving a signal and a signal non-reception mode (Tx mode) for not receiving a signal,

The temperature sensor measures the ambient temperature only once when the signal receiving mode is started.

According to the present invention, it is possible to easily adjust the reception sensitivity without degrading the performance of the system in the DSRC.

In addition, by integrating the DSRC receiver based on the CMOS technology, it can be integrated with a GPS or DMS chip.

Hereinafter, a DSRC signal receiver according to the present invention will be described in detail with reference to the accompanying drawings. Throughout the drawings the same components have been represented using the same reference numerals.

1 is a diagram illustrating a receiver 100 according to an embodiment of the present invention.

The receiver 100 includes a low noise amplifier (“LNA”) 104, a mixer 106, a frequency synthesizer 108, a bandpass filter 110, and a log amplifier 112. ), A detector 114, a switch 116, and a switch controller 120.

LNA 104 amplifies a radio frequency received signal with minimal amplification of the noise contained in the signal. The signal amplified by the LNA 104 is input to the mixer 106. The mixer 106 converts the signal amplified by the LNA 104 into frequency-down converter and outputs an intermediate frequency (IF) signal. Mixer 106 receives a local oscillator (LO) frequency signal from frequency synthesizer 108 to frequency-downconvert the signal amplified at LNA 104. The LO frequency is set so that the following equation is true.

[Equation 1]

| LO frequency ± RF frequency | = IF frequency

The bandpass filter 110 selectively passes only a band of a required channel among the output signals of the mixer 106. The log amplifier 112 amplifies the output signal of the bandpass filter 110 at a log scale and adjusts the level of the received signal strength indicator RSSI of the output signal of the bandpass filter 110. Output

The detector 114 compares the output of the log amplifier 112 with a predetermined binary threshold and outputs the first value of the binary signal when the output of the log amplifier 112 is below the binary threshold. When the output of the log amplifier 112 is greater than or equal to the binary threshold, the second value of the binary signal is output. For example, the binary signal may be -1 or 1, the first value of the binary signal may be -1, and the second value may be 0. In this case, the binary threshold may be zero. Alternatively, the binary signal may be 0 or 1, the first value of the binary signal may be 0, and the second value may be 1. In this case, the binary threshold may be 0.5.

One end of the switch 116 is connected to the output terminal of the detector 114, and the other end thereof is connected to the output terminal (Out) of the receiver 100. do. When switch 116 is closed, the output of detector 114 is delivered to an output Out of receiver 100, and when switch 116 is open, output of detector 114 Is not transmitted to the output (Out) of the receiver (100).

The switch control unit 120 compares the RSSI output from the log amplifier 112 with a predetermined RSSI threshold, opens the switch 116 when the RSSI is below the RSSI threshold, and the RSSI is the RSSI. If it is above the threshold, close the switch.

That is, the detection result of the detector 114 is output to the outside of the receiver 100 only when the strength of the received signal is greater than or equal to a predetermined magnitude. Therefore, unlike the prior art in which the noise index of the receiver is deliberately degraded to adjust the range in which the receiver operates, according to the present invention, the performance indicators such as the gain and noise index of the receiver are maintained as good as possible, By arbitrarily adjusting only the RSSI threshold, the operating range of the receiver can be adjusted.

The reception power vs. BER characteristic in the case of using the reception sensitivity adjusting method of the receiver 100 according to the present invention is shown in FIG. 3.

In the graph of FIG. 3, the x-axis represents the strength of the signal of the received signal, that is, the received power, and the y-axis represents the BER of the receiver when the signal of the corresponding strength is received. Graph 301 is a graph showing the received power vs. BER characteristic when the receiver sensitivity is set to P _SEN1 , and graph 302 is a graph showing the received power vs. BER characteristic when the receiver sensitivity is set to P _SEN2 .

Referring to the graph 301, when the reception sensitivity of the receiver 100 is set to P _SEN1 , the switch controller 120 outputs the detector 114 to the output terminal of the receiver 100 when the received signal strength is less than P _SEN1 . Prevent delivery Alternatively, a digital signal that is completely independent of the received signal is output to the output terminal of the receiver 100. Therefore, BER in this case is 0.5. When the received signal strength is P _SEN1 or more, the receiver 100 has a normal BER characteristic according to the receiver 100 characteristic.

Referring to the graph 302, when the receiver sensitivity of the receiver 100 is set to P _SEN2 , the switch controller 120 outputs the detector 114 to the output terminal of the receiver 100 when the received signal strength is less than P _SEN2 . Prevent delivery Alternatively, a digital signal that is completely independent of the received signal is output to the output terminal of the receiver 100. Therefore, BER in this case is 0.5. If the received signal strength is P _SEN2 or more, the receiver 100 has a normal BER characteristic according to the receiver 100 characteristics.

When compared with the graph of the graph Fig. 2 shown in FIG. 3, FIG even when 3 changes the reception sensitivity DO causing deterioration of the performance such as the noise figure of the receiver, the reception sensitivity of the receiver, the receiver sensitivity in the case where P _SEN1 and receiver Regardless of the case of P _SEN2 , when the receiver is operating (BER <0.5), the received power vs. BER characteristics match. Therefore, compared with the conventional method, better BER characteristics can be obtained for a constant reception strength.

In the BER characteristic of the conventional method shown in Fig. 2, since the receiver sensitivity is adjusted by degrading the receiver performance such as the noise figure of the receiver, even if the receiver sensitivity is higher from P _SEN1 to P _SEN2 , The BER characteristic of the receiver is the same. In comparison with this, the advantages of the receiver according to the present invention can be more clearly understood.

Hereinafter, a method for adjusting reception sensitivity in the receiver 100 according to the present invention will be described in more detail. Referring back to FIG. 1, the switch controller 120 includes an analog-to-digital converter (ADC) 122, a threshold generator 130, and a comparator 124.

The ADC 122 converts the RSSI output from the log amplifier 112 into a digital value. The threshold generator 130 generates a RSSI threshold for determining whether the receiver operates when the RSSI is greater than or equal to a value. The RSSI threshold generated by the threshold generator 130 may be input by a producer or a user, or may be arbitrarily generated by the threshold generator 130 according to an operating environment of the receiver 100. The RSSI threshold generator 134 may include an I2C communication module (not shown) for communication with the outside of the receiver 100. Through the I2C communication module, the RSSI threshold inside the receiver 100 may be input and / or modified.

The comparator 124 compares the RSSI output from the log amplifier 112 with the RSSI threshold output from the RSSI threshold generator 130, and outputs a control signal to the switch 116 according to the comparison result. When the RSSI is smaller than the RSSI threshold, the comparator 124 outputs a control signal for opening the switch 116 to the switch 116, and when the RSSI is above the RSSI threshold, the comparator 124 shorts the switch 116. The control signal for outputting is output to the switch 116. As such, the output signal is turned on and off by turning the switch 116 on and off according to the RSSI. This approach is called digital gating.

As described above, in the receiver 100 according to the present invention, the reception sensitivity of the receiver 100 is adjusted according to the RSSI threshold generated by the RSSI threshold generator 130. That is, according to the present invention, the reception sensitivity is adjusted by digital gating. Therefore, the receiver sensitivity of the receiver 100 may be arbitrarily adjusted by arbitrarily adjusting the RSSI threshold generated by the RSSI threshold generator 130.

<Adjustment of reception sensitivity according to ambient temperature>

1, the RSSI threshold generator 130 of the receiver 100 according to another embodiment of the present invention includes a temperature sensor 132 and a lookup table 134. The temperature sensor 132 measures the temperature around the OBU that contains the receiver 100. The lookup table 134 stores RSSI thresholds corresponding to temperatures. The lookup table 134 includes a memory for storing temperature values and corresponding RSSI thresholds. The RSSI threshold corresponding to the temperature may be input at the time of production of the receiver 100 or may be input by the user during use of the receiver 100. In addition, the RSSI threshold corresponding to the temperature may be appropriately selected and input according to a use purpose, a use environment, and the like of the receiver 100.

The RSSI threshold generator 134 finds the RSSI threshold value corresponding to the temperature measured by the temperature sensor 132 in the lookup table 134 and outputs the RSSI threshold to the comparator 124.

As such, by selecting and using an appropriate RSSI threshold according to the ambient temperature, the system performance can be maintained approximately constant regardless of the ambient temperature. Therefore, the receiver 100 according to an embodiment of the present invention can be stably used even in a vehicle or the like having a large range of temperature change.

Low Noise Clocking of Temperature Compensation Circuit

Next, a low noise clocking characteristic of the temperature sensor 132 included in the receiver 100 according to another embodiment of the present invention will be described. The temperature sensor 132 converts a general temperature value, which is analog information, into digital temperature information. At this time, the sampling clock of the analog-to-digital converter (ADC) used may interfere with the transmission and reception signal. Therefore, the temperature sensor 132 periodically updates the temperature information in the reception standby mode to block the possibility of such interference, but in the reception mode (RX-mode) and the transmission mode (TX-mode), the reception mode and the transmission mode. Only update the temperature information when each starts.

4 is a timing diagram of a clock supplied to a temperature sensor 132 according to a transmission / reception mode of a DSRC including a receiver 100 according to the present invention. In FIG. 4, the section other than the reception mode (RX-mode) or the transmission mode (TX-mode) is a transmission / reception standby mode. In the transmission and reception standby mode, the clock CLK _ADC is periodically supplied to the analog-to-digital converter ADC of the temperature sensor 132. However, in the transmission mode RX-mode, the clock CLK _ADC is supplied only at the moment when the transmission mode RX-mode starts. Similarly, in the receive mode (TX-mode), the clock (CLK _ADC ) is supplied only at the beginning of the receive mode (TX-mode).

<DSRC transceiver chip set>

Next, referring to FIG. 5, the DSRC chip set 500 including the receiver 100 according to an exemplary embodiment of the present invention will be described. 5 is a block diagram of a DSRC chip set 500 according to another embodiment of the present invention. The internal components of the DSRC chip set 500 that match the receiver 100 will be omitted. The DSRC chip set 500 further includes a power amplifier 401, a mixer 402, and a pulse shaping filter 403.

From the outside of the DSRC chip set 500, a digital signal to be transmitted is input to an input terminal In of the DSRC chip 500. The input signal is limited in bandwidth by the pulse shaping filter 403. The output signal of the pulse shaping filter 403 is then frequency-up converted by the mixer 402. The LO frequency signal is fed from the frequency synthesizer 108 to the mixer 402 for frequency-up conversion in the mixer 402. The signal frequency-converted in the mixer 402 is amplified by the power amplifier 401.

An SPTD switch 404 is connected to the outside of the DSRC chip 500 to connect the DSRC chip 500 to the antenna according to the transmission / reception mode.

As such, the transmitter and receiver of the DSRC chip 500 are included in one single chip, and the LO frequency supplied to the transmitter and the receiver is supplied by the single frequency synthesizer 108, thereby reducing the chip area. In addition, by integrating a transceiver for DSRC based on CMOS technology, one-chip can be easily integrated with a GPS or DMS chip.

<IF frequency>

As another embodiment of the present invention, the IF frequency of the receiver 100 may be selected as the 10 MHz band. When the IF frequency is selected as the 10 MHz band, the band pass filter 203 also has a relatively low pass band of about 10 MHz, and thus can be integrated into a single chip by a complementary metal-oxide semiconductor (CMOS) process. In addition, since the 10 MHz frequency band is used as the IF frequency, an image removal circuit is not required separately. 6 is a frequency waveform of an RF signal and an image signal received and signal processed by the ASK receiver 200 according to the present invention.

The RF signal represents a radio frequency signal for DSRC according to the DSRC standard, and its intermediate frequencies are 5800 MHz, 5810 MHz, 5840 MHz, and 5850 MHz, respectively. When setting the IF frequency to 10 MHz, assuming low-side LO injection, the LO frequencies are 5790 MHz, 5800 MHz, 5830 MHz, and 5840 MHz, respectively. Thus, for each RF signal, signals in the 5780 MHz, 5790 MHz, 5820 MHz, and 5830 MHz bands are converted to 10 MHz IF frequencies as image signals. However, signals are not allocated to the 5820 MHz and 5830 MHz bands in the DSRC standard, and the 5780 MHz and 5790 MHz bands are frequency bands other than those specified in the DSRC standard. Therefore, separate image removal circuits are provided for these image signals. Not required. Similarly, even in the case of assuming up-side LO injection, the frequency band of the image signal is a band to which no signal is assigned in the DSRC standard or a frequency band other than the band defined in the DSRC standard, so that the image removal circuit There is no need. Therefore, the size of the receiver 100 can be reduced and the price can be lowered.

Although the receiver 100 and the DSRC chip set 500 according to the present invention have been described as being used in the DSRC as an example, this is merely illustrative, and the receiver 100 according to the present invention is within the scope of the inventive concept. Can be used in any communication system. Therefore, it should be understood that any receiver utilizing the spirit of the present invention as well as the DSRC receiver belongs to the scope of the present invention.

1 is a diagram illustrating a receiver 100 according to an embodiment of the present invention.

2 is a graph illustrating the received power (P _IN ) vs. BER characteristic in a method of adjusting a reception sensitivity of a conventional receiver.

3 is a graph showing received power vs. BER characteristic in a method for adjusting the reception sensitivity of a receiver according to the present invention.

4 is a timing diagram of a clock supplied to a temperature sensor 132 according to a transmission / reception mode of a DSRC including a receiver 100 according to the present invention.

5 is a block diagram of a DSRC chip set 500 according to another embodiment of the present invention.

Claims (3)

A low noise amplifier (LNA) for amplifying a radio frequency (RF) received signal while minimizing amplification of noise included in the RF signal; A mixer configured to output an intermediate frequency (IF) signal by frequency-down converting the output signal of the LNA; A frequency synthesizer for generating a frequency signal for frequency down-conversion of the mixer and outputting the frequency signal to the mixer; A bandpass filter for passing only a band of a required channel among the output signals of the mixer; A log amplifier amplifying the output signal of the bandpass filter at a log scale and outputting a received signal strength indicator (RSSI) of the output signal of the bandpass filter; Compare the output of the log amplifier with a predetermined binary threshold, output a first value of a binary signal if the output of the log amplifier is less than the binary threshold, and the output of the log amplifier is A detector for outputting a second value of the binary signals when the binary threshold is greater than or equal to; A switch connected in series to the output of the detector; And Compare the RSSI to a predetermined RSSI threshold, open the switch if the RSSI is less than the predetermined RSSI threshold, and short the switch if the RSSI is above the predetermined RSSI threshold. and a switch controller to close the receiver. The method of claim 1, The switch control unit, An analog-to-digital converter (ADC) for converting the RSSI into a digital signal; An RSSI threshold generator for generating the RSSI threshold; And And a comparator to compare the RSSI with the RSSI threshold and to open or connect the switch. The method of claim 2, The RSSI threshold generation unit, A temperature sensor for measuring an ambient temperature; And And a lookup table in which the RSSI threshold corresponding to the temperature measured by the temperature sensor is stored.

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