JP2016225969A - Local oscillation signal level adjustment circuit, local oscillation signal level adjustment method, and radio communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a local oscillation signal level adjustment circuit capable of adjusting local oscillation signal level in high accuracy.SOLUTION: A local oscillation signal level adjustment circuit 20 includes: a local oscillation circuit 12 for outputting a local oscillation signal; a variable gain amplifier 13 for amplifying level of the local oscillation signal; a frequency conversion circuit 11 for converting a radio signal into an analog baseband signal using the amplified local oscillation signal; an A/D converter 15 for converting the analog baseband signal into a digital baseband signal; and a control circuit 14 for controlling the gain of the variable gain amplifier 13 based on an output code of the digital baseband signal. The control circuit 14 increases the gain of the variable gain amplifier 13 until the output code of the digital baseband signal is saturated.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a local oscillation signal level adjustment circuit, a local oscillation signal level adjustment method, and a radio communication device used in a radio communication device.

  A wireless communication apparatus that is currently popular performs a demodulated signal process after down-converting a received radio frequency signal to a baseband using a frequency conversion circuit. In the conventional frequency conversion, the output signal (local oscillation signal) of the local oscillation circuit is injected into the frequency conversion circuit. However, when the local oscillation signal level decreases due to, for example, a temperature change, the conversion gain of the frequency conversion circuit may decrease.

  Various methods have been proposed as methods for suppressing fluctuations in conversion gain. For example, a circuit that detects a local oscillation signal level adjusts the local oscillation signal level to be constant when the temperature changes (see, for example, Patent Document 1).

  The local oscillation signal level adjustment circuit disclosed in Patent Document 1 detects the local oscillation signal level injected into the frequency conversion circuit, compares it with the reference DC signal, and makes the local oscillation signal level constant.

Japanese Patent Laid-Open No. 2003-32048

  However, the technique disclosed in Patent Document 1 described above requires the following measures. The circuit that detects the local oscillation signal level is likely to cause characteristic fluctuations due to, for example, manufacturing variations or temperature fluctuations. Therefore, a circuit for detecting the local oscillation signal level requires calibration using an external reference signal in order to increase detection accuracy. It is difficult to accurately calibrate radio frequency signals in the millimeter wave band. Therefore, the adjustment of the local oscillation signal level by the built-in local oscillation signal level detection circuit becomes inaccurate.

  Non-limiting embodiments of the present disclosure provide a local oscillation signal level adjustment circuit, a local oscillation signal level adjustment method, and a wireless communication apparatus that can adjust the local oscillation signal level with high accuracy.

  In a conventional wireless communication apparatus, such as direct conversion, in which the received signal and the local oscillation signal have the same frequency, the local oscillation signal injected into the frequency conversion circuit returns from the input of the frequency conversion circuit via the previous circuit. An operation called mixing occurs. Therefore, in the conventional wireless communication device, a DC offset voltage is generated at the output of the frequency conversion circuit. The DC offset voltage is linked to a conversion gain that changes according to the local oscillation signal level. Similar to the conversion gain, the DC offset voltage increases as the local oscillation signal level increases, and then saturates.

  A local oscillation signal level adjusting circuit according to an aspect of the present disclosure includes a local oscillation circuit that outputs a local oscillation signal, a variable gain amplifier that amplifies the level of the local oscillation signal, and the amplified local oscillation signal. A frequency conversion circuit for converting a radio signal into an analog baseband signal, an A / D converter for converting the analog baseband signal into a digital baseband signal, and the variable based on an output code of the digital baseband signal. A control circuit for controlling the gain of the gain amplifier, wherein the control circuit increases the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated.

  These general and specific aspects may be realized by a system, a method, a computer program, and any combination of the system, method, and computer program.

  The local oscillation signal level adjustment circuit according to an aspect of the present disclosure can omit a circuit that detects a local oscillation signal level that has been necessary in the past, and can adjust the local oscillation signal level with high accuracy.

  Further advantages and effects in one aspect of the present disclosure will become apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and features described in the description and drawings, respectively, but all need to be provided in order to obtain one or more identical features. There is no.

FIG. 3 is a block diagram illustrating a configuration example of the wireless communication device 1 according to the first embodiment of the present disclosure. The figure which shows the procedure which adjusts the local oscillation signal level of FIG. FIG. 3 is a block diagram illustrating a configuration example of a wireless communication device 1A according to Embodiment 2 of the present disclosure.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, in the embodiment, components having the same function are denoted by the same reference numerals, and redundant description is omitted.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration example of the wireless communication device 1 according to the first embodiment of the present disclosure. Hereinafter, the configuration of the wireless communication device 1 will be described with reference to FIG. Although the wireless communication device 1 in FIG. 1 illustrates the configuration of the wireless reception unit, the present disclosure is not limited thereto, and may include a configuration of a wireless transmission unit.

  In FIG. 1, the wireless communication device 1 includes an antenna 2, a low noise amplifier (hereinafter referred to as LNA) 10, a local oscillation signal level adjustment circuit 20, and a baseband signal processing circuit 17.

  The local oscillation signal level adjustment circuit 20 includes a frequency conversion circuit 11, a local oscillation circuit 12, a variable gain amplifier 13, a control circuit 14, an A / D converter (ADC) 15, and a D / A converter (DAC) 16. .

  The LNA 10 amplifies the radio signal received by the antenna 2 and outputs it to the frequency conversion circuit 11. The local oscillation circuit 12 generates a local oscillation signal having a stable constant frequency and outputs it to the variable gain amplifier 13. The variable gain amplifier 13 can change the gain by the control circuit 14. The variable gain amplifier 13 amplifies a local oscillation signal that is an output signal from the local oscillation circuit 12 and outputs the amplified signal to the frequency conversion circuit 11. The frequency conversion circuit 11 includes a mixer (mixer) configured using, for example, a plurality of MOS (Metal Oxide Semiconductor) transistors, and a low-pass filter (LPF). The frequency conversion circuit 11 mixes the radio signal output from the LNA 10 with the local oscillation signal output from the variable gain amplifier 13, for example, down to an analog baseband signal (differential output signal) in a differential signal format. Convert. The frequency conversion circuit 11 outputs an analog baseband signal to the A / D converter 15. The A / D converter 15 converts the analog baseband signal into a digital baseband signal.

  In the frequency conversion circuit 11, a DC offset voltage is generated in the analog baseband signal of the frequency conversion circuit 11 due to manufacturing variations. Here, it is difficult for a wireless communication apparatus using a conventional millimeter-wave band radio frequency signal to use capacitive coupling. For this reason, the wireless communication device 1 compensates for the DC offset voltage in a state of being directly connected to DC. For this purpose, the control circuit 14 outputs a digital baseband signal output code (formed by a plurality of bits) of the A / D converter 15 that changes according to the DC offset voltage of the analog baseband signal input to the A / D converter 15. ) Is detected, and the D / A converter 16 is used to compensate for the DC offset voltage of the analog baseband signal of the frequency conversion circuit 11. Specifically, the control circuit 14 generates a digital control signal (digital voltage) for adjusting the DC offset voltage of the analog baseband signal of the frequency conversion circuit 11. The D / A converter 16 converts the digital control signal into an analog control signal (analog voltage), and outputs the analog control signal to the mixer of the frequency conversion circuit 11.

  The A / D converter 15 outputs the output code of the digital baseband signal to the baseband signal processing circuit 17. The baseband signal processing circuit 17 performs, for example, demodulation processing of an output code (received radio signal) of a digital baseband signal and outputs a demodulated signal.

  The control circuit 14 is a hardware controller, for example, a computer that controls the operation of the wireless communication device 1 using a memory. Based on the output code of the digital baseband signal of the A / D converter 15 that changes according to the DC offset voltage of the analog baseband signal input to the A / D converter 15, the control circuit 14 Control the gain.

  The procedure for adjusting the local oscillation signal level will be described with reference to FIG. 2A, 2B, and 2C are obtained when the local oscillation signal level of the variable gain amplifier 13 (hereinafter referred to as PLO (Power of Local Output)) is changed. 2 shows the DC offset voltage of the analog baseband signal output from the frequency conversion circuit 11, the output code of the digital baseband signal output from the A / D converter 15, and the conversion gain of the frequency conversion circuit 11.

  First, the control circuit 14 sets PLO to PLO_0 (initial value) (state S1). In the state S1, the conversion gain of the frequency conversion circuit 11 is G_0 ((C) in FIG. 2). The control circuit 14 estimates the DC offset voltage of the analog baseband signal output from the frequency conversion circuit 11 using the output code of the digital baseband signal of the A / D converter 15. When the DC offset voltage is ΔV_0, the output code of the digital baseband signal of the A / D converter 15 is C_0 (state S1).

  Next, the control circuit 14 optimizes the PLO until the conversion gain of the frequency conversion circuit 11 reaches the saturation conversion gain G_sat as shown in FIG. Adjustment is made to increase to the vicinity of the value PLO_sat (change from state S1 to state S2). Due to the increase in PLO, the DC offset voltage of the analog baseband signal becomes greater than ΔV_0 in conjunction with the conversion gain of the frequency conversion circuit 11. As shown in FIG. 2B, the output code of the digital baseband signal of the A / D converter 15 is converted into an analog baseband signal that is output when the DC offset voltage of the analog baseband signal is 0V. The deviation from the corresponding half value C_center (initial adjustment value) of the output full scale value becomes large. That is, when changing from the state S1 to the state S2, the output code of the digital baseband signal of the A / D converter 15 becomes large in the same manner as the change of the DC offset voltage. Therefore, the control circuit 14 can estimate the DC offset of the analog baseband signal output from the frequency conversion circuit 11 using the output code of the digital baseband signal of the A / D converter 15.

  When the control circuit 14 increases the PLO until the conversion gain of the frequency conversion circuit 11 reaches the saturation conversion gain G_sat, the DC offset voltage of the analog baseband signal becomes ΔV_sat and becomes saturated, and the A / D conversion is performed. The output code of the digital baseband signal of the device 15 also increases to a constant value bit sequence signal (C_sat). The control circuit 14 increases the gain of the variable gain amplifier 13 until the output code of the digital baseband signal of the A / D converter 15 becomes C_sat and becomes saturated (until the bit sequence signal becomes a constant value (for example, maximum value)). By gradually increasing the PLO, the PLO can be adjusted to the optimum value PLO_sat.

  Further, the control circuit 14 outputs a digital control signal for compensating the output code of the digital baseband signal of the A / D converter 15 to the initial adjustment value C_center to the D / A converter 16, and the D / A converter 16 16 is used to compensate the DC offset voltage so that the DC offset voltage of the analog baseband signal of the frequency conversion circuit 11 becomes 0V (initial adjustment: adjustment from state S2 to state S3). As a result, the wireless communication device 1 enters a state of normal operation (state S3). Hereinafter, the adjustment operation in a state in which the characteristics are changed at a high temperature after the initial adjustment will be described.

  When the wireless communication device 1 is at a higher temperature than in the initial state (after DAC adjustment), the PLO is lower than the PLO value in the state S3 (state S4). In the state S4, the output code of the digital baseband signal of the A / D converter 15 is C_S4. In state S4, the DC offset voltage of the analog baseband signal of the frequency conversion circuit 11 is ΔV_S4.

  Therefore, when the output code of the digital baseband signal changes from the initial adjustment value C_center, the control circuit 14 sets the output code of the digital baseband signal of the A / D converter 15 to C_sat2 as in the initial adjustment. The gain of the variable gain amplifier 13 is gradually increased until it is saturated (change from state S4 to state S5). Further, when the state S4 changes to the state S5, the DC offset voltage of the analog baseband signal again becomes ΔV_sat2 and becomes saturated. By this adjustment, the control circuit 14 can increase the PLO to the vicinity of the optimum value PLO_sat until the conversion gain of the frequency conversion circuit 11 reaches the saturation conversion gain G_sat2 and saturates, thereby bringing the frequency conversion circuit 11 into the optimum operation state. it can.

  As described above, the local oscillation signal level adjustment circuit 20 according to the first embodiment includes the local oscillation circuit 12 that outputs the local oscillation signal, the variable gain amplifier 13 that amplifies the level of the local oscillation signal, and the amplified local portion. A frequency conversion circuit 11 that converts a radio signal into an analog baseband signal using an oscillation signal, an A / D converter 15 that converts an analog baseband signal into a digital baseband signal, and an output code of the digital baseband signal And a control circuit 14 for controlling the gain of the variable gain amplifier 13. The control circuit 14 increases the gain of the variable gain amplifier 13 until the output code of the digital baseband signal is saturated. For this reason, the local oscillation signal level adjustment circuit 20 can omit a circuit for detecting the local oscillation signal level that has been conventionally required, and can adjust the local oscillation signal level with high accuracy. Further, since the DC offset voltage (ΔV_sat2) in the state S5 can be expected to be sufficiently small, compensation of the DC offset voltage by the D / A converter 16 is simpler than the initial adjustment (adjustment from the state S2 to the state S3). can do.

(Embodiment 2)
FIG. 3 is a block diagram illustrating a configuration example of the wireless communication device 1A according to the second embodiment. Radio communication apparatus 1A is configured in consideration of increasing the overall gain of the reception circuit in order to improve the reception sensitivity of radio communication apparatus 1 according to Embodiment 1. Compared with the wireless communication apparatus 1 according to the first embodiment shown in FIG. 1, the wireless communication apparatus 1A includes a local oscillation signal level adjustment circuit 20A between the frequency conversion circuit 11 and the A / D converter 15 in the baseband. An amplifier 18 is provided.

  The baseband amplifier 18 amplifies the analog baseband signal and outputs the amplified analog baseband signal to the A / D converter 15. The control circuit 14 increases the gain of the variable gain amplifier 13 until the output code of the digital baseband signal of the A / D converter 15 is saturated (until the DC offset voltage of the analog baseband signal from the frequency conversion circuit 11 is saturated). increase.

  As described above, the local oscillation signal level adjustment circuit 20A according to the second embodiment includes the local oscillation circuit 12 that outputs the local oscillation signal, the variable gain amplifier 13 that amplifies the level of the local oscillation signal, and the amplified local signal. A frequency conversion circuit 11 that converts a radio signal into an analog baseband signal using an oscillation signal, an A / D converter 15 that converts an analog baseband signal into a digital baseband signal, and an output code of the digital baseband signal And a control circuit 14 for controlling the gain of the variable gain amplifier 13. The control circuit 14 increases the gain of the variable gain amplifier 13 until the output code of the digital baseband signal is saturated. For this reason, the local oscillation signal level adjustment circuit 20A can omit a circuit for detecting the output level of the local oscillation circuit 12 that has been used conventionally, and can accurately adjust the output level (PLO) of the local oscillation circuit 12. Can do. The local oscillation signal level adjustment circuit 20A according to the second embodiment further includes a baseband amplifier 18 that is provided between the frequency conversion circuit 11 and the A / D converter 15 and amplifies the baseband signal. Therefore, reception sensitivity can be improved.

(Summary of embodiment)
A local oscillation signal level adjusting circuit according to a first aspect of the present disclosure includes a local oscillation circuit that outputs a local oscillation signal, a variable gain amplifier that amplifies the level of the local oscillation signal, and the amplified local oscillation signal. Using a frequency conversion circuit that converts a radio signal into an analog baseband signal, an A / D converter that converts the analog baseband signal into a digital baseband signal, and an output code of the digital baseband signal, A control circuit for controlling the gain of the variable gain amplifier, the control circuit increasing the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated.

  A local oscillation signal level adjustment circuit according to a second aspect of the present disclosure is the local oscillation signal level adjustment circuit according to the first aspect, wherein the control circuit sets the output code of the digital baseband signal to an initial adjustment value. It further includes a D / A converter that outputs a digital control signal for compensation, converts the digital control signal into an analog control signal, and outputs the analog control signal to the frequency conversion circuit.

  When the local oscillation signal level adjustment circuit according to the third aspect of the present disclosure is the local oscillation signal level adjustment circuit according to the second aspect, when the output code of the digital baseband signal is changed from the initial adjustment value, Again, the gain of the variable gain amplifier is increased until the output code of the digital baseband signal is saturated.

  A local oscillation signal level adjustment circuit according to a fourth aspect of the present disclosure is the local oscillation signal level adjustment circuit according to any one of the first to third aspects. A baseband amplifier is provided between the A / D converter and amplifies the analog baseband signal.

  A wireless communication device according to a fifth aspect of the present disclosure includes an antenna that receives a wireless signal, a low-noise amplifier that amplifies the wireless signal, a local oscillation circuit that outputs a local oscillation signal, and an output of the local oscillation signal A variable gain amplifier that amplifies the level, a frequency conversion circuit that converts the amplified radio signal into an analog baseband signal using the amplified local oscillation signal, and the analog baseband signal into a digital baseband signal An A / D converter for conversion, a baseband processing circuit for outputting a demodulated signal obtained by demodulating the output code of the digital baseband signal, and a variable gain amplifier based on the output code of the digital baseband signal. A control circuit for controlling a gain, wherein the control circuit saturates the output code of the digital baseband signal. Until the gain of the variable gain amplifier is increased.

  A local oscillation signal level adjustment method according to a sixth aspect of the present disclosure outputs a local oscillation signal, amplifies the output level of the local oscillation signal by a variable gain amplifier, and uses the amplified local oscillation signal, A radio signal is converted into an analog baseband signal, the analog baseband signal is converted into a digital baseband signal, a gain of the variable gain amplifier is controlled based on an output code of the digital baseband signal, and the digital base The gain of the variable gain amplifier is increased until the output code of the band signal is saturated.

  The present disclosure is useful, for example, as a wireless communication apparatus that performs stable reception operations by reducing characteristic fluctuations due to process variations and temperature changes in a wireless communication apparatus using a radio frequency signal in the millimeter wave band.

1, 1A ... wireless communication device,
2 ... antenna,
10 ... Low noise amplifier (LNA),
11 ... frequency conversion circuit,
12 ... Local oscillation circuit,
13: Variable gain amplifier,
14 ... control circuit,
15 ... A / D converter,
16 ... D / A converter,
17 ... Baseband signal processing circuit,
18 ... Baseband amplifier,
20, 20A... Local oscillation signal level adjustment circuit.

Claims (6)

A local oscillation circuit that outputs a local oscillation signal;
A variable gain amplifier for amplifying the level of the local oscillation signal;
A frequency conversion circuit that converts a radio signal into an analog baseband signal using the amplified local oscillation signal;
An A / D converter for converting the analog baseband signal into a digital baseband signal;
A control circuit for controlling the gain of the variable gain amplifier based on an output code of the digital baseband signal,
The control circuit includes:
Increasing the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated;
Local oscillation signal level adjustment circuit. The control circuit outputs a digital control signal for compensating the output code of the digital baseband signal to an initial adjustment value;
A D / A converter that converts the digital control signal into an analog control signal and outputs the analog control signal to the frequency conversion circuit;
The local oscillation signal level adjustment circuit according to claim 1. The control circuit increases the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated again when the output code of the digital baseband signal changes from the initial adjustment value.
The local oscillation signal level adjustment circuit according to claim 2. A baseband amplifier provided between the frequency conversion circuit and the A / D converter and amplifying the analog baseband signal;
The local oscillation signal level adjustment circuit according to any one of claims 1 to 3. An antenna for receiving radio signals;
A low noise amplifier for amplifying the radio signal;
A local oscillation circuit that outputs a local oscillation signal;
A variable gain amplifier for amplifying the output level of the local oscillation signal;
A frequency conversion circuit that converts the amplified radio signal into an analog baseband signal using the amplified local oscillation signal;
An A / D converter for converting the analog baseband signal into a digital baseband signal;
A baseband processing circuit that outputs a demodulated signal obtained by demodulating the output code of the digital baseband signal;
A control circuit for controlling the gain of the variable gain amplifier based on the output code of the digital baseband signal;
With
The control circuit includes:
Increasing the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated;
Wireless communication device. Output the local oscillation signal from the local oscillation circuit,
Amplifying the output level of the local oscillation signal by a variable gain amplifier;
Using the amplified local oscillation signal, a frequency conversion circuit converts a radio signal into an analog baseband signal,
The analog baseband signal is converted into a digital baseband signal by an A / D converter,
Based on the output code of the digital baseband signal, the gain of the variable gain amplifier is controlled,
Increasing the gain of the variable gain amplifier until the output code of the digital baseband signal is saturated;
Local oscillation signal level adjustment method.

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