JP2009118386A - Level adjustment circuit of reception signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a level adjustment circuit of reception signal that obtains a desired intermediate frequency signal for excessive input of a reception signal by a compact, light-weight, inexpensive circuit method by downsizing of a circuit. <P>SOLUTION: The level adjustment circuit of reception signal includes: a waveguide matching circuit 11 which inputs a reception signal of millimeter wave and matches impedance of an input circuit; a mixer diode 12 for converting frequency by a reception signal and a local signal; a mixer diode matching circuit 13 for passing an element with an optional microwave band frequency; an intermediate frequency amplifier 21 which amplifies the output signal at an optional level and outputs an intermediate frequency signal; a reception level adjustment circuit 22 for creating a control voltage to control the signal at an optional gain; a high impedance line 31 connected with an output circuit of a millimeter wave band waveguide diode mixer; and a bias voltage generator 32 which supplies bias voltage for adjusting reception level to the line at the excessive input level of the reception signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to level control of an amplifier and a frequency converter, and more particularly to a received signal level adjustment circuit suitable for use in an output stabilization circuit of an intermediate frequency amplifier of a millimeter wave receiver.

  In a radio communication system to which a level adjustment circuit for a received signal input to a millimeter wave receiver is applied, for example, each mobile unit is equipped with a semi-fixed communication (a fixed line after moving) Is a several tens GHz band wireless transmission apparatus capable of high-speed data transmission.

  This millimeter-wave wireless transmission device includes a wireless device (transceiver), an antenna, and a terminal-side interface, and is installed so that the antennas face each other at a straight line-of-sight distance.

  There are various antenna distances between moving bodies deployed for communication.

  Therefore, if deployed at a short distance, the transmission wave from one mobile body may become a strong electric field reception wave at the receiver of the other mobile body opposite to this, resulting in excessive input. In such a case, securing the linearity of the intermediate frequency amplifier circuit of the millimeter wave receiver becomes a problem.

  A block diagram of a level adjustment circuit for a received signal input to a millimeter wave receiver, which is a prior art, is shown in FIG.

  The received signal level adjusting circuit includes a millimeter wave band waveguide diode mixer 1 in which a waveguide matching unit 11, a mixer diode 12, and a mixer diode matching circuit 13 are sequentially connected in series. It is constituted by a microwave band intermediate frequency amplifier 20 comprising an intermediate frequency amplifier 21 (multiple stages (A) to (G)) connected in series to the millimeter wave band waveguide diode mixer 1 and a reception level adjusting circuit 22. The

  First, the mixer diode 12 converts the input received signal into a microwave band intermediate frequency signal a. Next, the converted signal is converted to a predetermined level by the multi-stage intermediate frequency amplifier 21. Amplified.

  The reception level adjustment circuit 22 generates a control voltage b corresponding to the reception level change. Therefore, the control voltage b is applied to the gain control terminal of the intermediate frequency amplifier 21 to control the gain and output an intermediate frequency signal of a predetermined level.

  When an excessive level signal is input to the input circuit of the received signal, the linearity range of the circuit of the microwave band intermediate frequency amplifier 20 with respect to the linearity range of the circuit of the millimeter waveband waveguide diode mixer 1 is In general, since it is narrow, the microwave band intermediate frequency amplifier 20 side first generates distortion.

  In order to avoid distortion of the output signal of the microwave band intermediate frequency amplifier 20 and obtain a predetermined output level, the amplification degree per amplifier stage is suppressed and the intermediate frequency amplifiers 21 are connected in multiple stages (21 in the illustration of FIG. 9). (A) to (G) (7 stages). For example, in order to correspond to the input level fluctuation range of 70 dB, the amplification degree per amplifier stage may be 10 dB and 7 stages.

  Although not described, it is necessary to insert a filter on the input side of the amplifier in order to obtain a predetermined microwave band intermediate frequency signal.

  In such a circuit configuration, the circuit scale becomes large, and it becomes difficult to realize a small, light, and low-priced device.

In a millimeter wave band FM transmitter / receiver, a DC error voltage of a transmission frequency is extracted from an output signal of a frequency converter of a receiver to stabilize the transmission frequency, so that a transmitter having an inexpensive and small AFC circuit can be used. I have a suggestion. (For example, see Patent Document 1)
JP-A-8-18404 (FIG. 1)

  In the prior art, as a means for obtaining an intermediate frequency signal having desired linearity and output level with respect to an excessive input of a received signal, a microwave band intermediate frequency amplifier has been realized by a multistage configuration.

  This increases the circuit scale, and is problematic in terms of size reduction, weight reduction, and price reduction.

  Furthermore, the repetition of excessive input sometimes shortens the life of the amplifier element at the top of the amplifier, and in the worst case, there is a problem in reliability that leads to internal destruction of the amplifier element.

  The object of the present invention is to solve the above-mentioned problems of the prior art, reduce the circuit scale, and obtain a desired intermediate frequency signal with respect to the excessive input of the received signal by a small, light and low cost circuit system. It is to provide a level adjustment circuit.

  In order to achieve this object, a received signal level adjusting circuit according to the present invention receives a millimeter-wave received signal as an input, passes through the first matching means for impedance matching of the input, and the first matching means. Mixer means for performing frequency conversion between the received signal and the local signal, and matching with the predetermined microwave band frequency component among a plurality of frequency components including the predetermined microwave band frequency component created by the mixer means A millimeter-wave band waveguide diode mixer sequentially connected to the second matching means to be amplified, and amplifying means for amplifying the output signal of the millimeter-wave band waveguide diode mixer to a desired level and outputting it as an intermediate frequency signal And a microwave band intermediate frequency amplifier connected to a reception level adjusting means for creating a control voltage for controlling the amplification means to the desired level. A level adjustment circuit,

  A high-impedance means connected to an output circuit of the millimeter-wave band waveguide diode mixer and a bias voltage generating means, the bias voltage generating means being a bias capable of adjusting a reception level when an over-input level of the received signal The voltage is superimposed on the output circuit and supplied to the mixer means.

  According to the present invention, it is possible to reduce the number of amplification stages of the intermediate amplifier circuit and to prevent operation instability due to the progress of characteristic deterioration inside the amplifier element when the millimeter wave receiver is excessively input.

  For example, when applied to a several tens GHz band wireless transmission system that can perform high-speed data communication as semi-fixed communication between moving bodies, it is small, lightweight, low power consumption that can be installed on each moving body, and Easy to deploy and inexpensive equipment can be provided.

  A block diagram of a level adjustment circuit for a received signal input to a millimeter wave receiver as an embodiment of the present invention is shown in FIG.

  The embodiment of the received signal level adjusting circuit in the millimeter wave receiver of the present invention is constituted by the following blocks.

  The waveguide matching unit 11 (first matching unit) is a three-dimensional circuit that receives a millimeter-wave reception signal and performs impedance matching of the input circuit.

  The mixer diode 12 (mixer means) receives a received signal that has passed through the waveguide matching unit 11 and a local signal that has been input from the outside and passed through the waveguide matching unit 11 as input. It is a circuit element that performs frequency conversion (down conversion) of a received signal.

  The mixer diode matching circuit 13 (second matching means) matches the predetermined microwave band frequency component among a plurality of frequency components including the predetermined microwave band frequency component created by the mixer diode 12. The matching circuit obtains and outputs the microwave band intermediate frequency signal a.

  As described above, the millimeter waveband waveguide diode mixer 1 is a module unit having a block configuration in which the waveguide matching unit 11, the mixer diode 12, and the mixer diode matching circuit 13 are sequentially connected in series.

  Next, the intermediate frequency amplifier 21 (amplifying means) receives the microwave band intermediate frequency signal a, which is the output signal of the millimeter wave band waveguide diode mixer 1, and applies a band limit to this to obtain a desired level. The amplifier circuit amplifies with such a gain and outputs the amplified intermediate frequency signal.

  Note that the number of stages of amplifier elements in the amplifier circuit may be one or a plurality of stages may be connected in series although not described.

  The reception level adjustment circuit 22 (reception level adjustment means) controls the control voltage b to control the gain to a desired output level in response to the input level change of the millimeter wave reception signal for the amplification operation of the intermediate frequency amplifier 21. Is a control circuit for creating

  As described above, the microwave band intermediate frequency amplifier 2 is an amplifier circuit that performs automatic gain control including the intermediate frequency amplifier 21 and the reception level adjustment circuit 22, and has a predetermined output level from the reception signal input to the receiver. This is a module unit having a block configuration for obtaining an intermediate frequency signal.

  Although not described, after the output of the microwave band intermediate frequency amplifier 2, predetermined signal processing is performed on the intermediate frequency signal, and the obtained signal (data) is used as a high-speed data terminal and an image device. And so on.

  Next, in the present invention, the high impedance line 31 (high impedance means) is branched and connected to the output circuit of the millimeter wave band waveguide diode mixer 1, and has a high impedance with respect to the high frequency component which is the microwave band intermediate frequency signal a. Thus, a circuit that blocks high frequency and allows the DC component to pass is obtained.

  The bias voltage generator 32 (bias voltage generating means) has an output connected to the high impedance line 31 and branches an intermediate frequency signal as an input, thereby detecting an excessive input level of the received signal, and the input is DC. The control circuit converts the level into a bias voltage c and supplies the bias voltage c to the output circuit of the millimeter waveband waveguide diode mixer 1 via the high impedance line 31.

  Thus, the bias voltage generation circuit 3 is a circuit composed of the high impedance line 31 and the bias voltage generator 32, and superimposes the bias voltage c on the signal line of the microwave band intermediate frequency signal a to match the mixer diode. This is a module unit having a block configuration that supplies a bias voltage c which is given to the mixer diode 12 via the circuit 13 and adjusts the reception level so as to reduce the input level when the reception signal is excessively input.

  Next, FIG. 2 shows an embodiment of a millimeter-wave band waveguide diode mixer circuit diagram of the present invention, which will be described.

  The circuit of the millimeter waveband waveguide diode mixer 1 of the present invention is inputted by a waveguide coupling to which a millimeter wave reception signal and a local signal are supplied from the outside, and impedance matching of the input circuit by the waveguide is performed. The waveguide matching unit 11 is disposed in the waveguide of the waveguide matching unit 11 that performs frequency conversion (down-converter) to obtain a microwave band frequency component by mixing the received signal and the local signal. A mixer diode 12 and a coaxial output terminal which is connected in series to the anode of the mixer diode 12 and is an output of the mixer diode matching circuit 13 and the mixer diode matching circuit 13 which allows impedance matching with a desired microwave band intermediate frequency signal And a module structure circuit.

  The circuit from the coaxial output terminal to the anode of the mixer diode 12 passes the bias voltage c so as to be used as a bias voltage path in addition to the function as a high frequency circuit and applies it to the anode of the mixer diode 12. A DC voltage path is formed.

  Next, FIG. 3 shows an embodiment of a bias voltage generation circuit diagram of the present invention, which will be described.

  In the bias voltage generating circuit 3 according to the present invention, one terminal 33 is branched and connected to a connection circuit between the millimeter wave band waveguide diode mixer 1 and the microwave band intermediate frequency amplifier 2, and the other terminal 34 is placed in the microwave band middle. The output of the frequency amplifier 2 is branched and connected.

  The one terminal 33 is connected to the high impedance line 31.

  The other terminal 34 is connected to the bias voltage generator 32, and its output is connected to the high impedance line 31.

  The bias voltage generation circuit 3 is a high-impedance line 31 that is realized by an inductor configured by, for example, a strip line that blocks high frequencies and passes DC, and a circuit that is connected to the high-impedance line 31 and outputs a bias voltage c. And the other terminal 34 which is a circuit connected to the output line of the microwave band intermediate frequency amplifier 2 to branch and input a part of the level of the microwave band intermediate frequency signal a, and the input of the received signal The circuit configuration includes a bias voltage generator 32 that does not generate a bias voltage if the level is in a steady range, and generates an arbitrary bias voltage c if the level is excessive.

  In the signal input circuit of the microwave band intermediate frequency amplifier 2, a capacitor 23 is connected in series with the input side of the intermediate frequency amplifier 21 in order to pass the microwave band intermediate frequency signal a and block DC.

  Therefore, the bias voltage c is supplied to the mixer diode 12 through a path in the direction opposite to the microwave band intermediate frequency signal a.

  Further, the bias voltage generator 32 is an arbitrary signal that determines that the input is an excessive input with respect to the DC voltage obtained by branching and inputting the intermediate frequency signal that is the output of the microwave band intermediate frequency amplifier 2. A signal processing circuit is provided that generates a bias voltage c and outputs the bias voltage c if the threshold value is exceeded.

  Next, FIG. 4 illustrates and explains the conversion loss characteristic diagram of the millimeter waveband waveguide diode mixer circuit of the present invention.

  This characteristic diagram is a characteristic diagram of the conversion loss of the bias voltage versus the mixer created corresponding to the input level of the received signal.

  If the input level of the received signal is the “steady input” level, no bias voltage for receiving level adjustment is generated for the mixer diode 12. (Black dot in FIG. 4; bias voltage 0 V, conversion loss: −5 dB). That is, the conversion loss is minimum, and a desired conversion frequency signal component is output from the millimeter waveband waveguide diode mixer 1 with minimum attenuation.

  Next, if the input level of the received signal is an “over-input” level, a bias voltage for adjusting the reception level for the mixer diode 12 is generated. (Arrow direction in FIG. 4; maximum bias voltage +2.5 V, maximum conversion loss: −55 dB). That is, the conversion loss is the maximum value, and the desired conversion frequency is attenuated by 50 dB and output from the millimeter waveband waveguide diode mixer 1.

  Note that the control amount set for the input variation range (70 dB) that is actually assumed takes into account the control amount share (30 dB) of the microwave band intermediate frequency amplifier 2, and the control amount share on the mixer side is , About 40 dB (bias voltage: 0 to 2.4 V, conversion loss: −5 dB to −45 dB).

  As a result, the amount of automatic gain control of the subsequent microwave band intermediate frequency amplifier 2 can be suppressed to 30 dB, so that distortion in the amplification element due to excessive input of the received signal is prevented, and linearity at the intermediate frequency amplification stage is ensured. Is done.

  Next, FIG. 5 illustrates and describes an input / output waveform diagram of the millimeter waveband waveguide diode mixer circuit of the present invention.

  A normal-level input signal waveform (similar to a sine wave) is input to a mixer diode with a bias voltage of 0V, and the output signal waveform appears as a half-wave waveform at the output due to diode characteristics (actually non-linear characteristics). It becomes a distorted wave that contains various frequency components.

  Although not shown, if two signals of normal level are input, the sum, difference (microwave signal component required by the circuit of the present invention), and higher-order frequency due to the mixer diode characteristics of FIG. Ingredients are generated. (Mixer function).

  Next, FIG. 6 illustrates and describes an input / output waveform diagram when a bias voltage is applied to the millimeter waveband waveguide diode mixer circuit of the present invention.

  The input signal waveform of the excessive input level (schematically expressed as a sine wave) is shifted to the positive voltage (+ several V) as the bias voltage (in the direction of the arrow) and input to the mixer diode. The output signal waveform is diode characteristics (actually Because the waveform does not become half-wave due to (non-linear characteristics) and generally appears in the output as a waveform similar to the input waveform, distortion components including harmonics are reduced, and various frequency components obtained by the mixer are reduced. The level is also attenuated.

  Although not shown in the figure, if two signals including an over-input signal are input to the mixer diode of FIG. 6, the sum and difference (microwaves required in the circuit of the present invention) depending on the characteristics of the biased diode. Signal component) and higher-order frequency components are generated, but their levels are suppressed compared to the characteristics of the mixer diode of FIG. (Increase in mixer conversion loss)

  Next, FIG. 7 illustrates and describes an input / output characteristic diagram of the millimeter waveband waveguide diode mixer circuit of the present invention.

  It is an input / output characteristic curve in which the horizontal axis represents the input level (dBm) of the millimeter waveband waveguide diode mixer 1 and the vertical axis represents the output level (dBm) of the millimeter waveband waveguide diode mixer 1. It is an input / output characteristic diagram in which the characteristic of the solid line is bias-set (0 V) as the normal input level, and the black circle point on the solid line is the maximum input point (input: 0 dBm, output: -5 dBm) without distortion. At input levels above this black dot, saturation characteristics due to diode clipping appear and distortion occurs in the output.

  Next, an example of an input / output characteristic diagram in which the characteristic of the broken line is biased (+ V) as an excessive input level and the level is reduced, and the black dot on the wavy line is an output compared with the characteristic of the solid line at the input 0 dBm point. Is a point attenuated by 10 dBm.

  This is a characteristic (i → b) in which the output value is shifted from (solid circle point on solid line; −5 dBm) to (black circle point on broken line; −15 dBm), and the maximum input that does not cause distortion is only 10 dB. Shifted to the excessive input side (input; +10 dBm, output; -5 dBm). That is, a characteristic that does not distort up to +10 dBm as an excessive input level of the input signal can be obtained. This means that, as the mixer input / output characteristics, the frequency conversion is performed on a non-linear curve unique to the diode element while expanding the input / output linearity range.

  In practice, an attenuation amount (shift amount) of 40 dB is obtained.

  Next, FIG. 8 illustrates and describes an input / output characteristic diagram of the microwave band intermediate frequency amplifier 2 of the present invention.

  FIG. 8 is a characteristic curve of the output of the mixer, that is, the output of the same output with respect to the input of the intermediate frequency amplifier. In this characteristic diagram, the left side of the curve (further to the left of the black circle point X) is an area in which linearity is ensured.

  However, when the curve is on the right curve from the black circle point X on the characteristic curve, the output signal will contain distortion, which will cause the signal to noise ratio to deteriorate during signal demodulation and cause errors in the data. End up.

  That is, the output (FIG. 7, solid curve, −5 dBm) at the maximum input point (FIG. 7, input; 0 dBm) in the curve of the normal input level to the mixer is the input point (FIG. 8, FIG. 8). Here, the black circle point Y), where the output signal of the intermediate frequency amplifier that requires linear amplification enters a region that causes nonlinear distortion. In the mixer stage, this is distorted in the amplifier stage even in the linear region.

  Therefore, by shifting the input point of the intermediate frequency amplifier to the minus side by 10 dBm by the attenuation operation to the 10 dBm attenuation point (FIG. 7, b: −15 dBm) in the mixer stage, the black circle point X is obtained. This can be an area that ensures the linearity of the output signal of the intermediate frequency amplifier.

  In order to correspond to the input level fluctuation range of 70 dB, the shift amount for 40 dB is obtained by the millimeter wave band waveguide diode mixer 1 first, so the range of automatic gain control in the microwave band intermediate frequency amplifier 2 is increased. The circuit of the amplifying element of the intermediate frequency amplifier 21 may be a three-stage configuration or less in which the number of stages is reduced. (At least four stages were reduced compared to the conventional configuration.)

  The present invention is applied to a wireless communication system used for mobile communication, and can be used as an example for data communication between temporary mobile bodies.

It is a block diagram of the level adjustment circuit of the received signal of the millimeter wave receiver which is this invention. It is a millimeter wave band waveguide diode mixer circuit diagram of the present invention. It is a bias voltage generation circuit diagram of the present invention. It is a conversion loss characteristic figure of the millimeter wave band waveguide diode mixer circuit of the present invention. It is an input / output waveform diagram of the millimeter waveband waveguide diode mixer circuit of the present invention. It is an input / output waveform diagram of the millimeter waveband waveguide diode mixer circuit of the present invention. It is an input-output characteristic figure of the millimeter wave band waveguide diode mixer circuit of this invention. It is an input-output characteristic figure of the microwave band intermediate frequency amplifier of this invention. It is a block diagram of the level adjustment circuit of the received signal of the millimeter wave receiver which is a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Millimeter wave band waveguide diode mixer 2, 20 Microwave band intermediate frequency amplifier 3 Bias voltage generation circuit 11 Waveguide matching device 12 Mixer diode 13 Mixer diode matching circuit 21 Intermediate frequency amplifier 22 Reception level adjustment circuit 23 DC blocking capacitor 31 High impedance line 32 Bias voltage generator 33, 34 terminal a Microwave band intermediate frequency signal b Control voltage c Bias voltage

Claims (1)

A first matching unit that receives a millimeter-wave reception signal as input and performs impedance matching of the input; mixer unit that performs frequency conversion between the received signal that has passed through the first matching unit and a local signal; and the mixer Millimeter wave waveguide diode in which a plurality of frequency components including a predetermined microwave band frequency component created by the means are sequentially connected to second matching means for matching the predetermined microwave band frequency component A mixer,
Amplifying means for amplifying the output signal of the millimeter-wave band waveguide diode mixer to a desired level and outputting it as an intermediate frequency signal, and reception level adjusting means for creating a control voltage for controlling the amplifying means to the desired level A microwave band intermediate frequency amplifier connected to
A received signal level adjusting circuit comprising:
A high-impedance means connected to an output circuit of the millimeter-wave band waveguide diode mixer and a bias voltage generating means, the bias voltage generating means being a bias capable of adjusting a reception level when an over-input level of the received signal A received signal level adjusting circuit, wherein a voltage is superimposed on the output circuit and supplied to the mixer means.

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