KR100853526B1 - Radio receiver becomes accomplished the gain control by the low pass filter - Google Patents

Abstract

A radio receiver for performing gain control by a low pass filter is provided to configure an LPF as a gm-C(transconductance-capacitor) filter by using OTA(Over The Air), perform gain tuning through the control of a first bias voltage applied to the LPF, and perform frequency tuning through the control of a second bias voltage, thereby simplifying the configuration of the radio receiver without a separate variable gain controller. A radio receiver includes a receiver(100) and an AGCL(Automation Gain Control Loop)(200). The receiver receives amplifies a RF(Radio Frequency) signal, and converts the amplified RF signal into a basebase signal. The AGCL controls the gain of the baseband signal converted through the receiver. The AGCL includes a first LPF(Low Pass Filter)(210), a second LPF(220), an RSSI(Received Signal Strength Indicator)(260), an MCU(Micro Control Unit)(250), first and second voltage-current converters(270,280), and a current-voltage converter(290). The first LPF has a first bias voltage terminal and a second bias voltage terminal, and tunes the frequency of a signal outputted through the receiver by the control of a bias voltage inputted to the second bias voltage terminal. The second LPF is connected to the output terminal of the first LPF, has a first bias voltage terminal and a second bias voltage terminal, and performs frequency tuning and gain tuning by the control of the bias voltage inputted through the first bias voltage terminal and the second bias voltage terminal. The RSSI detects the voltage level of a signal outputted from the first LPF and outputs a voltage varied linearly according to an input voltage. The MCU receives the output signal of the RSSI and outputs a reference voltage and a second bias voltage. The first and second voltage-current converters are connected to each of the output terminal of the RSSI and the output terminal of the MCU to convert output voltages into currents separately and output the converted currents. The current-voltage converter converts the sum of currents outputted from the first and second voltage-current converters into voltages and applies a bias voltage to the first bias voltage terminal of the second LPF.

Description

RADIO RECEIVER BECOMES ACCOMPLISHED THE GAIN CONTROL BY THE LOW PASS FILTER}

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the configuration of a wireless receiver in which gain control is performed by a low pass filter of the present invention.

FIG. 2 is a circuit diagram illustrating the low pass filter of FIG. 1. FIG.

3 is a block diagram showing an embodiment of the RSSI of FIG.

4 is a block diagram showing an embodiment of the LPF of FIG.

FIG. 5 is a partial configuration diagram illustrating another embodiment of the RSSI of FIG. 1. FIG.

FIG. 6 is a diagram illustrating some components of another embodiment of the RSSI of FIG. 1. FIG.

7 is a block diagram illustrating a wireless receiver having a conventional general automatic gain controller.

<Description of the symbols for the main parts of the drawings>

100: receiver

      110: low noise amplifier (LNA)

      120: radio signal variable gain amplifier (RF-VGA)

      130: Mixer

      140: oscillator (VCO)

200: Automatic Gain Control Loop (VGA Loop)

      210: first low pass filter (LPF)

      220: second low pass filter (LPF)

      230: buffer

      240: ADC

      250: MCU

      260: received signal strength detector (RSSI)

            261 limiting amplifier

            262: full-wave rectifier (FWR)

            263 low pass filter (LPF)

            264 current supply means

            265: NMOS FET

270: first voltage-to-current converter (VI Converter)
280: second voltage-to-current converter (VI Converter)

      290: I-V Converter

The present invention relates to a broadcast receiver, and more particularly, a low pass filter applicable to a multi-standard method by adjusting a bias voltage input to a low pass filter without a variable gain amplifier through an MCU to achieve gain and frequency tuning. The present invention relates to a wireless receiver in which gain control is performed.

In general, as portable digital broadcasting services such as DMB (Digital Multimedia Broadcasting) and DVB-H (Digital Video Broadcasting-Handheld) become commercially available, researches on RF tuners for digital broadcasting have been actively conducted.

The receiver of the RF tuner accepts an input signal whose amplitude varies from time to time with the distance from the transmitter. In order to transmit the radio frequency band (RF) of the radio frequency band (RF Band) received through the receiver to convert to a baseband signal (baseband) signal, so that the automatic gain controller (AGC: Automation Gain Controller) The function of is important.

In general, a super-heterodyne type receiver is a radio frequency band (RF band) received by the receiver to the radio (RF) signal of the intermediate frequency band (Intermediate Frequency Band; IF Band) ) And then convert the IF signal to the baseband signal repeatedly.

This structure adds nonlinear characteristics due to repetitive frequency conversions, resulting in intermodulation distortion or parasitic components. Therefore, SAW filters are used externally to remove intermodulation distortion or parasitic components, thereby increasing production costs. Causes cause.

In order to overcome this disadvantage, conventionally, a low-IF receiver using an image removal filter to remove an image is used. The image frequency is generated near the RF, which makes it difficult to completely remove the image, resulting in poor sensitivity, and due to I / Q mismatch. There is an image-band problem.

Therefore, in order to overcome these disadvantages, a direct conversion (Zero-IF) receiver is used as another conventional receiver.

The direct conversion receiver can be integrated into a single chip by demodulating the oscillator into a baseband signal without converting the RF signal of the RF band into an IF band. Therefore, the device can be miniaturized and the manufacturing process is simple.

However, the signal output from the Zero-IF receiver must match the band received as the input from the demodulator. Therefore, when the signal is used for a multi mode / multi band, According to an input frequency band of each demodulator, a frequency band of a low pass filter (LPF) output from a zero-IF receiver is required to be redesigned for a demodulator.

Here, the signal received from the antenna of the receiver in which the above-described receiver receives Digital Multimedia Broadcasting (DMB) and Digital Video Broadcasting-Handheld (DVB-H) is a signal in which a noise signal is mixed, and the signal is transmitted through a channel. The degree of attenuation of the signal varies depending on the path.

Therefore, the gain must be controlled through an automatic gain controller (AGC) so that the received signal can maintain a constant signal size.

7 is a block diagram showing a wireless receiver having a conventional general automatic gain controller, a low-noise amplifier (LNA) 11, a radio frequency-variable gain controller (RF-VGA) 12. And a receiver (1) comprising a mixer (Mixer, 12) and an oscillator (Voltage Control Oscillator; VCO, 14), and to tune the frequency and gain of the baseband converted signal through the receiver (1). First Low Pass Filter (LPF) 21, Variable Gain Amplifier 22, VGA, Buffer 23, Received Signal Strength Indication (RSSI) 25, Comparator 26, and Gain Controller 27 ), And an automatic gain control loop 2 including an ADC 23 and an MCU 28.

According to this configuration, the voltage level is detected using the RSSI 260 from the signal amplified while the noise is suppressed through the LNA 11, the result is compared with the reference value in the comparator 26, and then the variable gain amplifier 27 is obtained. ) To output the gain control signal to the variable gain amplifier 27.

However, according to the prior art, when the reception sensitivity is detected from the output signal of the LNA, the circuit design is difficult because it has a high frequency of several hundred MHz to several GHz and receives a very small signal of about -100 dBm to -40 dBm.

In addition, gain tuning is performed through the voltage control of the variable gain amplifier. Since the automatic gain controller must configure the low pass filter and the variable gain amplifier as necessary, there is an inefficient disadvantage due to a large power consumption and additional circuit configuration. .

An object of the present invention for solving the problems according to the prior art, the low pass filter is configured by gm-C using OTA, and the gain tuning through the first bias voltage adjustment applied to the low pass filter, the second The present invention provides a wireless receiver in which gain control is performed by a low pass filter that can simplify the configuration because frequency tuning is performed through bias voltage adjustment so that a separate variable gain amplifier is not configured.

A wireless receiver having gain control by the low pass filter of the present invention for solving the above technical problem is a baseband converted through a receiver and a receiver for receiving and amplifying an RF signal and converting the amplified RF signal to a baseband. A wireless receiver comprising an automatic gain control loop for controlling a gain of a signal, the automatic gain control loop having a first bias voltage terminal and a second bias voltage terminal and configured to control bias voltage input to the second bias voltage terminal. A first low pass filter for frequency tuning of the signal output through the receiver by means of the first low pass filter, and a first bias voltage terminal and a second bias voltage terminal connected to an output terminal of the first low pass filter. Bias Input Through Terminal and Second Bias Voltage Terminal A second low pass filter for performing frequency tuning and gain tuning by voltage control, and a voltage level that is linearly variable according to an input voltage [dBm] by detecting a voltage level of a signal output from the first low pass filter. A received signal strength detector for outputting V], an MCU receiving the output signal of the received signal strength detector and outputting a reference voltage and a second bias voltage, and an output terminal of the received signal strength detector and an output terminal of the MCU, respectively First and second voltage-current converters for converting output voltages into currents and outputting currents, and converting a sum of currents output from the first and second voltage-current converters into voltages to convert the output voltages into voltages. And a current-voltage converter applying a bias voltage to the first bias voltage terminal.

Here, the first low pass filter and the second low pass filter are composed of an RLC ladder type passive filter connected to a rear end of a third voltage-current converter and a third voltage-current converter, wherein the third The voltage-to-current converter is composed of an OTA whose gm value is adjusted through the first bias voltage terminal, and the resistor R of the passive filter is composed of an OTA whose gm value is adjusted through the second bias voltage terminal. The inductor L is composed of a plurality of OTAs and capacitors whose gm values are adjusted through the second bias voltage terminal, and the first low pass filter and the second low pass filter are applied through a second bias voltage terminal. Frequency control is achieved by a second bias voltage, and the second low pass filter is gain controlled by a first bias voltage applied through a first bias voltage terminal. It is.

The invention will become more apparent through the preferred embodiments described below with reference to the accompanying drawings. Hereinafter will be described in detail to enable those skilled in the art to easily understand and reproduce through embodiments of the present invention.

1 is a block diagram showing a configuration of a wireless receiver in which gain control is performed by a low pass filter of the present invention, and includes a receiver 100 and an automatic gain control loop 200.

The receiver 100 includes a low-noise amplifier (LNA) 110, a radio frequency-variable gain controller (RF-VGA, 120), a mixer (Mixer, 130), and a oscillator (Voltage Control). Oscillator; VCO, 140).

Here, the LNA 110 amplifies while suppressing noise amplification of the RF signal received through the antenna, and the RF-VGA 120 adjusts the gain of the signal amplified by the LNA 110 once again within a certain range of signals. Amplify by improving linearity.

In addition, the mixing unit 130 converts the frequency generated and supplied by the oscillator and the signal output from the RF-VGA 120 to convert to a baseband signal.

On the other hand, the automatic gain control loop (Automation Gain Control Loop, 200) is amplified by adjusting the frequency and gain of the signal is converted to the baseband from the receiver 100 and then output to the ADC 240 through the buffer 230 The first low pass filter (hereinafter referred to as 'first LPF'), the second low pass filter (hereinafter referred to as 'second LPF'), and the received signal strength detector ( 260 and MCU 250, first voltage-current converter 270, second voltage-current converter 280, and current-voltage converter 290.

Here, the first low pass filter 210 selects and filters only channels of a specific frequency band from the signal output through the receiver 100, and the second low pass filter 220 filters the first low pass filter 210. The filter selects and filters only channels with a specific frequency band from the signal output.

At this time, the first low pass filter 210 and the second low pass filter 220 have a first bias voltage terminal and a second bias voltage terminal, respectively, in accordance with a characteristic aspect of the present invention.

In addition, the first low pass filter and the second low pass filter 220 are frequency-tuned by controlling the second bias voltage applied to the second bias voltage terminal with the same magnitude at the same time, and the second low pass filter 220. The gain tuning is performed by the first bias voltage applied through the first bias voltage terminal. At this time, the gain of the first low pass filter 210 is fixed.

Here, the first bias voltage is controlled by the sum of the linear voltage output according to the RSSI input signal and the reference voltage output from the MCU, and the second bias voltage is a signal output from the MCU.

More specifically, the first low pass filter 210 and the second low pass filter 220 are configured as a third voltage-to-current converter (VI Converter) consisting of a gm-C filter using OTA as shown in FIG. And a passive filter of RLC ladder type connected to the rear end of the third voltage-to-current converter VI converter.

Here, the resistance R of the passive filter of the RLC ladder type is configured using an OTA, and the inductor L is composed of a plurality of OTAs and capacitors. At this time, the first bias terminal for adjusting the gm (trans-conductance) value of the OTA constituting the third voltage-to-current converter (VI Converter) 221, and the gm (trans) of the rear end of the third voltage-to-current converter (VI Converter) has a second bias voltage terminal to adjust the value.

With this configuration, gain tuning is achieved by controlling the first bias voltage applied to the OTA portion constituting the third V-I converter in each low pass filter.

In addition, when the second bias voltage is simultaneously controlled to the same magnitude, the gm value of the OTA is adjusted to perform frequency tuning.

The RSSI 260 is configured to detect a voltage level of the signal output from the first low pass filter 210 and output a voltage [V] that varies linearly according to the input voltage [dBm].

At this time, the RSSI 260 is used as a sensitivity indicator of the received signal, and the received signal sensitivity indicates power [dBm] and converts the detected power into a DC voltage level. The relationship between the voltage [V] and [dBm] Since it is expressed by, it is implemented by the principle of log amplifier.

That is, when a signal of various sizes is input, the linear DC voltage output is output according to the signal of the dBm size unit in order to output it as a signal of a constant size and input to the third current-voltage converter 221 of each low pass filter. The first bias voltage is influenced to adjust the voltage gain of the second low pass filter 220.

More specifically, the RSSI is connected to a plurality of limiting amplifiers LA 261 for amplifying an input signal and clipping at a predetermined level, as shown in FIG. 3, and connected to an output terminal of each LA 261 to output an output signal. A full wave rectifier (FWR) 262 for rectifying and generating an AC current, and an LPF 263 for outputting a linear DC voltage by removing ripple from the sum of AC currents output from the FWR 262. LA 261 and FWR 262 are configured in the form of a log amplifier via a cascade connection.

Here, in the embodiment of the present invention, a full wave rectifier is used, but a half wave rectifier may be used, and the LPF 263 may include a first resistor R1 that is variable to determine the magnitude of the output voltage of the RSSI as shown in FIG. 4. A first low pass filter part 263a including a first capacitor C1 for removing a ripple current of a signal output from the FWR 242 together with the first resistor R1 and an output from the FWR 262. The second low pass filter part comprising a second resistor (C2) connected to the output terminal of the signal ripple is removed by the second resistor (R2) and the second resistor (R2) serving as a resistance to the ripple current of the signal 263b.

In detail, since the lowest reference voltage is controlled by the value of R1, an output voltage increases as R1 increases, and a response time increases, and when C1 increases, a ripple current of the FWR 262 decreases and a response time increases. R2 removes the noise of the signal input to MCU (). If the size of R2 and C2 is larger, noise and ripple are eliminated, but the response time is longer because the time constant is longer.

, 대역폭을

라 하면, 단위 리미팅 증폭기의 이득과 대역폭은 아래의 수학식에 의해 결정된다.Since the plurality of LAs 261 and the FWRs 262 are connected in series, the number of LAs is determined in consideration of overall voltage gain, bandwidth, power consumption, and the like. Thus, the number of LAs is N, and the required total voltage gain

Bandwidth

In this case, the gain and bandwidth of the unit limiting amplifier are determined by the following equation.

[Equation 1]

Here, the first input signal is gradually amplified by the LA 241 with a constant voltage gain, and the signal, which is somewhat larger, is clipped at a constant level.

The signal amplified by LA () becomes an input signal of each FWR 262 to generate full-wave rectified AC current, and the sum of the output currents of each FWR () is applied to the LPF 263 composed of R and C. This eliminates ripple and outputs a voltage close to DC.

In addition, the present invention further includes a current supply means 264 in which the RSSI 260 is connected to the input terminal of the first resistor R1 as shown in FIG. 5, and the first as shown in FIG. 6. A current supply means 264 connected to the input terminal of the resistor R1 and an NMOS FET 265 having a source and a drain connected to both ends of the first resistor R1 may be further provided.

According to this configuration, the output of the RSSI by varying the magnitude of the voltage output by the first resistor R1 through the current control applied through the current supply means 264 or the voltage control input through the NMOS FET 265. The slope reference of the characteristic can be changed.

Here, the current supply means 264 is provided with a switching means to control the current supply through the digital on-off control, it can be used to control the current supply by the sweep control in another embodiment.

Accordingly, the present invention can be used by variously applying to the desired communication method by setting the current control mode through the R1 and the current supply means constituting the LPF 263 of the RSSI 260 according to the communication method to be used. .

According to this configuration, since the RSSI 260 receives the output of the first low pass filter 210 at the rear end of the receiver as an input signal, the RSSI 260 has a design of at least several tens of dB or more compared to receiving the output of the LNA in front of the existing mixer as the input signal. Can be facilitated.

In other words, when the signal is taken from the front end of the LNA according to the conventional method, it has a high frequency of several hundred MHz to several GHz and receives a very small signal of -100 dBm to -40 dBm. When imported, it has a low frequency range of several KHz ~ several tens of MHz, and it imports a large signal of about -70dBm ~ -10dBm, which facilitates the circuit design.

Meanwhile, the MCU250 recognizes the strength of the received signal by receiving the output signal of the RSSI 260 and selects a specific frequency channel by outputting a second bias voltage applied to the first low pass filter and the second low pass filter. In addition to this, a reference voltage for applying the first bias voltage is output.

In addition, the first voltage-to-current converter 270 is connected to the output terminal of the RSSI 260, the second voltage-to-current converter 280 is connected to the output terminal of the MCU 250, respectively, the output from the RSSI 260 and MCU 250 Convert the reference voltage to a current.

In addition, the current-voltage converter 290 converts the sum of currents output from the first and second voltage-current converters 270 and 280 into voltage to convert the first low pass filter 210 and the second low pass filter ( 220 is applied as the first bias voltage.

Looking at the operation of the radio receiver to gain control by the low pass filter of the present invention according to this configuration as follows.

First, the RF signal input through the antenna is amplified while the noise is suppressed through the LNA (110), and the amplified signal is adjusted once again through the RF-VGA (120) to improve linearity to a signal within a certain range. Amplified as much as possible.

Subsequently, the signal output from the RF-VGA 120 is converted into a baseband signal through the mixer 130 according to the oscillation control signal of the oscillator 140.

In addition, the first low pass filter 210 selects and filters only a channel having a specific frequency band from the signal output through the mixer 130 according to the second bias voltage controlled by the control signal of the MCU ().

Subsequently, the RSSI 260 outputs a linear DC voltage [V] with respect to the signal of the [dBm] magnitude unit output from the first low pass filter 210, and the MCU 250 determines a reference set according to the corresponding communication mode. Output voltage.

Accordingly, the voltages output by the RSSI 260 and the MCU 250 are converted into currents through the first and second voltage-to-current converters 270 and 280 connected to the respective output terminals, and the sum of the currents thus converted. The sum is converted through the current-voltage converter 290 and then applied to the first bias voltage of the second low pass filter 220.

Here, the first bias voltage acts as an OTA bias voltage of the third voltage-to-current converter 221 constituting the second low pass filter 220 to gain control.

Meanwhile, the MCU 250 applies the second bias voltage to the second low pass filter 220 simultaneously with the reference voltage output.

The second bias voltage is simultaneously applied to the third voltage-to-current converter of the second low pass filter 220 and to each of the OTAs constituting the resistor and the inductor with the same voltage, and the channel of the specific frequency band is applied by the second bias voltage. Only selected frequency tuning takes place.

Since the signal conversion process corresponds to a known technique, a detailed description thereof will be omitted.

As described above, the wireless receiver in which gain control is performed by the low pass filter of the present invention configures each component of the low pass filter as a gm-C filter using OTA, and uses the output voltage of the RSSI and the control voltage of the MCU as bias voltages. Therefore, the frequency tuning is performed through the low pass filter so that all gains are achieved, thereby simplifying the configuration because a separate variable gain amplifier (VGA) is not configured.

As described above, according to the embodiments of the present invention, the low pass filter is configured as gm-C using OTA, gain tuning is performed through the first bias voltage adjustment applied to the low pass filter, and the second bias voltage adjustment is performed. By tuning the frequency through the separate variable gain amplifier is not configured to simplify the configuration, there is an advantage to improve the ease of design.

In addition, the wireless receiver using the low pass filter of the present invention as a gain control signal can be used for multi-mode and multi-band by allowing the frequency and gain characteristics to be adjusted by controlling the output voltage of the MCU. There is an advantage that can be used for standard).

In addition, the present invention further comprises a current supply means for varying the current applied to the resistor constituting the low pass filter of the received signal strength detector so that the output voltage is variable and an NMOS FET, the current supply means according to the communication method to be used And since the frequency and gain characteristics of the band can be obtained by setting the NMOS FET variably, there is an advantage that can be applied to various communication schemes.

Although the present invention has been described with reference to the accompanying drawings, it will be apparent to those skilled in the art that many different and obvious modifications are possible without departing from the scope of the invention from this description. Therefore, the scope of the invention should be construed by the claims described to include many such variations.

Claims (6)

A wireless receiver comprising a receiver for receiving and amplifying an RF signal and converting the amplified RF signal to baseband and an automatic gain control loop for controlling the gain of the baseband signal converted through the receiver. The automatic gain control loop; A first low pass filter having a first bias voltage terminal and a second bias voltage terminal for frequency tuning of a signal output through the receiver by bias voltage control input to the second bias voltage terminal; In the first low pass filter, frequency tuning and gain tuning are performed by bias voltage control connected to an output terminal and having a first bias voltage terminal and a second bias voltage terminal and input through the first bias voltage terminal and the second bias voltage terminal. A second low pass filter, A received signal strength detector for detecting a voltage level of the signal output from the first low pass filter and outputting a voltage [V] that varies linearly according to an input voltage [dBm]; An MCU which receives an output signal of the received signal strength detector and outputs a reference voltage and a second bias voltage; First and second voltage-current converters respectively connected to an output terminal of the received signal strength detector and an output terminal of the MCU to convert an output voltage into a current and output the current; And a current-to-voltage converter for converting a sum of currents output from the first and second voltage-to-current converters into voltages to apply a bias voltage to the first bias voltage terminal of the second low pass filter. A radio receiver in which gain control is performed by a low pass filter. The method of claim 1, The first low pass filter and the second low pass filter; A third voltage-current converter, It is connected to the rear end of the third voltage-to-current converter and consists of a passive filter of RLC ladder type combined with a resistor (R), an inductor (L), and a capacitor (C), The third voltage-to-current converter is configured with an OTA whose gm value is adjusted through the first bias voltage terminal, The resistor R of the passive filter includes an OTA in which a gm value is adjusted through the second bias voltage terminal, and the inductor L includes a plurality of OTAs and capacitors in which a gm value is adjusted through the second bias voltage terminal. Consisting of The first low pass filter and the second low pass filter are frequency controlled by a second bias voltage applied through a second bias voltage terminal, And the second low pass filter is gain controlled by a first bias voltage applied through a first bias voltage terminal. The method of claim 2, The received signal strength detector; Multiple limiting amplifiers that amplify the input signal and clip it at a constant level; A plurality of rectifiers for rectifying an output signal of each limiting amplifier to generate an AC current, and And a low pass filter that removes ripple with respect to the sum of the AC currents output from the rectifier and outputs a linear DC voltage. And the limiting amplifier and the rectifier are configured in the form of a log amplifier via a cascade connection. The method of claim 3, wherein A low pass filter of the received signal strength detector; A first low pass filter comprising a first resistor that is variable to determine the magnitude of the output voltage of the received signal strength detector and a first capacitor that removes the ripple current of the signal output from the rectifier together with the first resistor; , And a second low pass filter unit including a second resistor which serves as a resistance to the ripple current of the signal output from the rectifier and a second capacitor connected to an output terminal of the signal from which the ripple is removed by the second resistor. A radio receiver in which gain control is performed by a low pass filter. The method of claim 4, wherein The received signal strength detector; And a current supply means for varying the current supplied to the first resistor to vary the magnitude of the output voltage by the first resistor. The method according to claim 4 or 5, The received signal strength detector; And a NMOS FET connected to both ends of the first resistor to control the resistance value of the first resistor, wherein the gain control is performed by a low pass filter.

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