JP5185552B2 - Millimeter-wave transceiver module - Google Patents

Description

  The present invention relates to a millimeter-wave transceiver module used in an in-vehicle millimeter-wave radar, and more particularly to a millimeter-wave transceiver module that enables transmission and reception of a plurality of frequency-modulated high-frequency signals having different modulation widths.

  In-vehicle millimeter-wave radar uses millimeter-wave electromagnetic waves and is applied to safety measures such as cruise control and mitigation of damage to drivers when collisions are unavoidable by detecting the distance to the vehicle ahead and relative speed. .

  This millimeter wave radar radiates FM-CW (Frequency Modulated Continuous Wave) millimeter wave toward the front and beat frequency from the difference between the received wave and the transmitted wave that bounce off the preceding vehicle. And the distance to the target and the relative speed are calculated using the beat frequency.

  A millimeter-wave transceiver module used in such a millimeter-wave radar includes a voltage-controlled oscillation circuit (hereinafter referred to as “VCO”) that generates a frequency-modulated high-frequency signal, but can generate the beat frequency described above. Therefore, a triangular wave voltage signal is applied to the VCO as a modulation voltage, and an FM-CW signal that is a high-frequency signal composed of an ascending modulation signal whose frequency increases with time and a descending modulation signal whose frequency decreases with time is generated. It has become.

  In the millimeter wave radar, the modulation width of the frequency-modulated high-frequency signal needs to be constant, but the VCO has individual differences and is easily affected by the environmental temperature. As a measure to make the modulation width of the FM-CW signal generated by the VCO constant by correcting the influence of the difference and the environmental temperature, a digital-to-analog converter (hereinafter referred to as “DAC”) that outputs a triangular wave voltage signal applied to the VCO. A method is proposed in which an output time designation is added to the digital data of the triangular wave voltage signal given to (2) and the output time interval of the DAC is changed (for example, Patent Document 1).

JP 2004-166076 A

  By the way, in the millimeter wave radar, if a plurality of the above-described frequency modulation widths can be provided, it is possible to improve the target detection performance according to the distance measurement distance. In the development of a millimeter-wave transmission / reception module that can provide a plurality of frequency modulation widths, it is necessary to effectively utilize the resolution of the DAC in all the modulation widths and to minimize the cost increase.

  However, if the digital data of the triangular wave voltage signal applied to the DAC is varied depending on the modulation width, the resolution of the DAC may not be fully utilized, which affects the detection performance of the millimeter wave radar with the modulation width. Things happen. Further, since the DAC is more expensive than other circuit components, it causes an increase in cost.

  This will be specifically described. Initially, a radar device is assumed in which the triangular wave voltage signal applied to the VCO is 0 to 1 V, and the DAC is 8-bit resolution for 1 V. A new modulation width in which the triangular wave voltage signal applied to the VCO is 0 to 3 V is set for such a radar device. If the digital data of the triangular wave voltage signal applied to the DAC is different for 1V with a small modulation width and 3V with a large modulation width, the original DAC has an 8-bit resolution for 1V with a small modulation width. In order to have the same resolution with respect to 3V having a large modulation width, it is necessary to replace it with an 11-bit DAC with 3 bits added. Then, at 1V with a small modulation width, only 8 bits out of the 11-bit resolution are used, and the DAC resolution cannot be fully used. Also, the price of the DAC becomes more expensive as the number of bits increases.

  The present invention has been made in view of the above, and the control for generating a plurality of frequency-modulated high frequency signals having different modulation widths in the VCO can fully utilize the resolution of the DAC in all modulation widths. And it aims at obtaining the millimeter wave transmission / reception module which can be performed in the form which suppresses cost increase to the minimum.

  In order to achieve the above-described object, the present invention includes a control unit that outputs a rising and falling modulated voltage digital signal, a digital / analog converting unit that converts the modulated voltage digital signal into an analog signal, and a digital / analog converting unit. In a millimeter-wave transceiver module including an oscillation circuit that generates a high-frequency signal that is frequency-modulated based on an output modulation voltage, and a reception circuit that receives and processes the high-frequency signal, the control unit has a plurality of modulation widths. Outputs a modulation voltage digital signal that can be converted using almost full scale regardless of the modulation width to be selected, and outputs a modulation voltage digital signal to the digital-analog conversion unit, regardless of the modulation width to be selected. A conversion gain, which is a ratio with respect to the output voltage of the digital-analog conversion means, is included in the plurality of modulation widths In response, a plurality of different values are set, a conversion gain corresponding to the modulation width switching signal is selected, and the output level of the digital-analog conversion means is changed using the selected conversion gain and given to the oscillation circuit. A gain conversion unit is provided.

  According to the present invention, the control unit outputs a modulation width switching signal for selecting and selecting a plurality of modulation widths, and the digital / analog conversion unit can perform conversion using almost full scale regardless of the selected modulation width. The modulation voltage digital signal is output to the digital / analog conversion unit, and the gain conversion unit selects a conversion gain corresponding to the modulation width switching signal from a plurality of different conversion gains, and uses the selected conversion gain to convert the digital / analog conversion unit. Since the output level is changed and given to the oscillation circuit as a frequency modulation signal, the resolution of the digital-analog conversion means can be fully utilized in all of the plurality of modulation widths, and the cost increase is also minimized. There is an effect that it can be performed in a suppressed form.

  Exemplary embodiments of a millimeter-wave transceiver module according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of a millimeter wave transceiver module according to Embodiment 1 of the present invention. In order to facilitate understanding of the present invention, first, the basic configuration and operation of the millimeter wave transmission / reception module will be described, and then the parts related to the first embodiment will be described.

  In FIG. 1, a transmission antenna 1 and a reception antenna 2 are antennas provided in the FM-CW radar. The millimeter wave transmission / reception module basically includes a high frequency circuit 3 connected to the transmission antenna 1 and the reception antenna 2, and a signal processing unit 4 a and a bias control circuit 5 connected to the high frequency circuit 3.

  The high-frequency circuit 3 has, as basic elements, a VCO 10 that generates a frequency-modulated high-frequency signal in response to a VCO modulation voltage (triangular wave voltage signal) that is a transmission command from the signal processing unit 4a, and most of the high-frequency signals that the VCO 10 outputs. Is given to the transmitting antenna 1 and the rest is given to the mixer 12 as a local signal, the mixer 12 that frequency-converts (down-converts) the received signal of the receiving antenna 2 by the local signal, and the converted output of the mixer 12 And a video amplifier 13 that supplies the received signal as a received signal to the signal processing unit 4a. Each element of the high-frequency circuit 3 is configured by an MMIC (Microwave Monolithic IC).

  The signal processing unit 4a receives a main circuit unit (hereinafter referred to as “microcomputer”) 15a that mainly performs transmission processing and measurement processing in FM-CW radar, and a transmission command (digital data of a triangular wave voltage signal) from the microcomputer 15a. A digital-to-analog converter (DAC) 16 for converting the analog signal; a filter 17 for shaping the stepwise triangular wave voltage signal output from the DAC 16 into a smooth triangular wave voltage signal and applying the smoothed triangular wave voltage signal to the VCO 10 of the high-frequency circuit 3; An analog-to-digital converter (ADC) 18 is provided which converts a received signal from the video amplifier 13 into a digital signal and supplies it to the microcomputer 15a.

  The bias control circuit 5 controls various bias voltages supplied to the respective MMICs in the high-frequency circuit 3 in accordance with commands sent from the bias control signal output unit 20 of the microcomputer 15a.

  In the FM-CW radar including the millimeter wave transmission / reception module configured as described above, the VCO 10 receives a VCO modulation voltage that is a triangular wave voltage signal from the signal processing circuit 4a, and a rising modulation signal whose frequency rises for a certain period. An FM-CW signal that is a high-frequency signal composed of a descending modulation signal that descends for a certain period is generated. Most of the FM-CW signal is supplied from the directional coupler 11 to the transmission antenna 1, and millimeter wave radio waves are emitted from the transmission antenna 1 toward the target. The remaining FM-CW signal is supplied to the mixer 12 as a local signal. The reflected wave at the target captured by the receiving antenna 2 is input to the mixer 12 as a received signal. The mixer 12 mixes the received signal from the receiving antenna 2 and the local signal from the directional coupler 11 and outputs a beat signal having a frequency difference between the two. The beat signal is appropriately amplified to a level by the video amplifier 13 and input to the microcomputer 15a via the ADC 18. The microcomputer 15a obtains the distance to the target object and the moving speed of the target object from the frequency in the rising modulation period and the frequency in the falling modulation period in the input beat signal.

  As shown in FIG. 1, the millimeter wave transceiver module according to the first embodiment includes a gain switching signal output unit 21 provided in the microcomputer 15a in the signal processing unit 4a, and gain conversion between the filter 17 and the VCO 10 is performed. A circuit 19a is provided.

  The microcomputer 15a controls the plurality of modulation widths in parallel with the function of managing the plurality of modulation widths of the frequency-modulated high frequency signal generated by the VCO 10 and outputting the digital data of the basic triangular wave voltage signal to the ADC 18. And a function for outputting a modulation width switching signal for selecting one of a plurality of modulation widths from the gain switching signal output unit 21 to the gain conversion circuit 19a.

  In the first embodiment, the plurality of modulation widths are the first modulation width and the second modulation width. Therefore, the switching signal output from the gain switching signal output unit 21 to the gain conversion circuit 19a is 2 Value level signal.

  The gain conversion circuit 19a has predetermined conversion gains (1 / n1, 1 / n2) that are ratios to the output voltage of the DAC 16 corresponding to the first modulation width and the second modulation width, respectively. The basic triangular wave voltage signal that is sent is converted with different conversion gains (1 / n1, 1 / n2) for the first modulation width and the second modulation width indicated by the switching signal sent from the microcomputer 15a. The size is switched and given to the VCO 10.

  The gain conversion circuit 19a performing such an operation determines the value of the feedback resistance element of the negative feedback amplifier circuit using an operational amplifier, for example, according to the conversion gain (1 / n1, 1 / n2), and the resistance value Can be realized by switching between the first modulation width and the second modulation width indicated by the switching signal.

  Hereinafter, an operation of switching the modulation width of the high frequency signal generated by the VCO 10 will be described with reference to FIG. FIG. 2 is a time chart for explaining the operation of switching the magnitude of the triangular wave voltage signal applied to the VCO according to the frequency modulation width.

FIG. 2A: The microcomputer 15a outputs to the DAC 16 digital data of a basic triangular wave voltage signal that can be converted by the DAC 16 using almost full scale, regardless of the modulation width to be switched. Therefore, the DAC 16 always outputs a basic triangular wave voltage signal having a constant amplitude using a full scale (0 to 5 V in the illustrated example) regardless of the modulation width to be switched.
FIG. 2B: The switching signal output from the gain switching signal output unit 21 by the microcomputer 15a includes a high level predetermined period for selecting the modulation width 1 and a low level predetermined period for selecting the modulation width 2.
FIG. 2C: In the gain conversion circuit 19a, the modulation control voltage applied to the VCO 10 is determined to be, for example, 0 to 3V for the modulation width 1 and 0 to 2V for the modulation width 2. On the other hand, the output of the DAC 16 is 0 to 5V. Therefore, the gain conversion circuit 19a converts the conversion gain 1 / n1 = 3 / in the period in which the switching signal designates the modulation width 1 with respect to the 0 to 5 V basic triangular wave voltage signal sent from the filter 17. In the period in which 5 is used and the modulation width 2 is specified, the conversion gain 1 / n2 = 2/5 is used.

  Incidentally, when the microcomputer 15a outputs digital data indicating different levels in the modulation width 1 and the modulation width 2 without performing such gain switching, if the gain is adjusted to the modulation width 1, only the gain of the modulation width 1 is obtained. Therefore, it is necessary to operate with a modulation width of 2. In the above example, since the gain of the modulation width 1 is 3/5 = 0.6, the amplitude at the modulation width 2 is 2 / 0.6 = 3.33V. If the resolution of the DAC 16 is 11 bits, the valid range is 0 to 1023 code. When the gain is adjusted to the modulation width 1, when the amplitude at the modulation width 2 = 3.33 V is converted to the output of the DAC 16, 682 code = 1023 × 2/3, and the resolution is reduced to 2/3. In terms of the number of bits, only a resolution equivalent to 9.4 bits can be obtained.

  As described above, according to the first embodiment, when the VCO 10 generates a plurality of frequency-modulated high-frequency signals having different modulation widths, the DAC 16 can perform conversion using almost full scale regardless of the modulation width. The digital data of the basic triangular wave voltage signal is output to the DAC 16 and a switching signal specifying the modulation width is output. The gain conversion circuit 19a amplifies the output of the DAC 16 with a plurality of different gains according to the switching signal, Since the amplified signal is supplied to the VCO 10 as a modulation control voltage, the resolution of the DAC 16 can be fully utilized in all modulation widths. Further, since the gain conversion circuit to be added can be configured at a low cost, the increase in cost can be minimized.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration of a millimeter wave transceiver module according to Embodiment 2 of the present invention. In FIG. 3, the same reference numerals are given to components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1). Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 3, the millimeter wave transceiver module according to the second embodiment is provided with a signal processing unit 4b in place of the signal processing unit 4a in the configuration shown in FIG. 1 (first embodiment). In the signal processing unit 4b, a gain value calculation output unit 22 is provided in the microcomputer 15b whose sign is changed, a gain value variable circuit 23 is added, and a gain conversion circuit 19b in which some functions are added instead of the gain conversion circuit 19a. Is provided.

  When changing one or more of the plurality of conversion gains set in the gain conversion circuit 19b, the gain value calculation output unit 22 of the microcomputer 15b is, for example, a predetermined value using temperature or distance measurement distance as an input parameter. The gain value that is to be changed by the calculation is calculated, and the calculated gain value is output to the gain value variable circuit 23.

  The gain value variable circuit 23 variably sets the conversion gain set in the gain conversion circuit 19b using the gain value received from the microcomputer 15b. Thereafter, in the gain conversion circuit 19b, the output of the DAC 16 is amplified using the variably set conversion gain.

  As described above, according to the second embodiment, since the conversion gain of the gain conversion circuit 19b can be appropriately changed, an appropriate conversion gain can be obtained in accordance with environmental conditions such as temperature, the ranging distance of the radar, and the like. Will be able to set. Even in this case, the resolution of the DAC can be utilized in all the modulation widths, and the cost increase can be minimized.

  As described above, the millimeter wave transmission / reception module according to the present invention is useful for transmitting / receiving a plurality of frequency-modulated high frequency signals having different modulation widths, and in particular, a target corresponding to a ranging distance in a millimeter wave radar. It is suitable for improving the object detection function.

It is a block diagram which shows the structure of the millimeter wave transmission / reception module by Embodiment 1 of this invention. It is a time chart explaining the operation | movement which switches the magnitude | size of the triangular wave voltage signal given to VCO according to a frequency modulation width. It is a block diagram which shows the structure of the millimeter wave transmission / reception module by Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission antenna 2 Reception antenna 3 High frequency circuit 4a, 4b Signal processing part 5 Control circuit 10 Voltage control oscillator (VCO)
11 Directional coupler 12 Mixer 13 Video amplifier 15 Main circuit (microcomputer)
16 Digital-to-analog converter (DAC)
17 Filter 18 Analog to Digital Converter (ADC)
19a, 19b Gain conversion circuit 20 Bias control signal output unit 21 Gain switching signal output unit 22 Gain value calculation output unit 23 Gain value variable circuit

Claims (2)

A control unit that outputs a modulation voltage digital signal that rises and falls, a digital-analog conversion unit that converts the modulation voltage digital signal into an analog signal, and a high-frequency signal that is frequency-modulated based on the modulation voltage output from the digital-analog conversion unit In a millimeter-wave transmission / reception module comprising an oscillation circuit that generates and a reception circuit that receives and processes the high-frequency signal,
Wherein the control unit are both outputs the modulation width switching signal for alternatively selecting a plurality of modulated width, regardless of the modulation width of selecting the modulation voltage digital signals which can be converted using the digital-analog converter gaff-scale Is output to the digital-analog converter,
A plurality of conversion gains, which are ratios relative to the output voltage of the digital-analog conversion unit, are set as different values corresponding to the plurality of modulation widths, and a conversion gain corresponding to the modulation width switching signal is selected and selected conversion A gain conversion unit that changes the output level of the digital-analog conversion unit using a gain and gives the oscillation circuit;
A millimeter-wave transmission / reception module comprising:   The millimeter wave transmission / reception module according to claim 1, further comprising a gain variable unit that variably sets each gain in the gain conversion unit.

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