JP3023862B2 - Oscillator / mixer shared circuit and multiplier / mixer shared circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator / mixer circuit and a multiplier / mixer circuit, and in particular, has both functions of a voltage controlled oscillator and a mixer capable of realizing a small and low-cost Doppler radar and FM-CW radar. The present invention relates to an oscillator / mixer combined circuit and a multiplier / mixer combined circuit having both functions of a multiplier and a mixer.

A Doppler radar used for measuring a relative speed with respect to an object or an FM-CW radar capable of measuring a relative distance in addition to a relative speed is originally intended for its use.
It is mounted on the outside of vehicles such as automobiles and helicopters. Therefore, miniaturization is required for appearance and ease of installation. In addition, since the output frequency is usually assigned to the millimeter wave, if there are too many circuit configuration units, many expensive millimeter wave devices will be used, leading to an increase in cost.

[0003]

2. Description of the Related Art FIG. 7 shows a Doppler radar or FM-C.
FIG. 2 is a diagram illustrating a basic configuration of a W radar. In FIG. 7, by applying a modulation signal to the voltage-controlled oscillator 10, a frequency-modulated wave is generated and transmitted from the transmitting antenna toward the object. In the FM-CW radar, for example, a millimeter wave band of 60 GHz is used, and a triangular wave is used as a modulation signal. The signal reflected by the object and received by the receiving antenna is mixed in the mixer 12 with a part of the transmission signal branched by the directional coupler 14 and has a base having a frequency difference between the transmission wave and the reception wave. A band signal is taken out, and a relative distance and a relative speed to the object are calculated from the frequency of the baseband signal.

FIG. 8 is a circuit diagram showing an example of a conventional voltage controlled oscillator 10 in the millimeter wave band. GaAs FET
Or FET1 composed of HEMT (heterojunction FET)
6, a strip line resonator 17 is connected to the gate terminal, and a variable capacitance diode 18 is connected in parallel to the strip line resonator. A modulation signal is applied to the variable capacitance diode 18 from a modulation terminal via an inductive element 19. A stub 20 is provided on the drain terminal side of the FET 16. The stub 20 is for adjusting the magnitude of the reflected power indicated by the arrow X due to the right side of the one-dot chain line in the figure, and by adjusting the distance between the length of the stub 20 and the drain terminal of the FET, The reflected power at 60 GHz indicated by X is set to a value higher than the loss power in the resonator 17, and stable oscillation at the resonance frequency of the resonator 17 is maintained.

The source terminal of the FET 16 is grounded, and the DC bias of the gate terminal and the drain terminal is supplied from a power supply (-Vcc) via resistors 24 and 26. The stubs 21 and 22 are respectively λg / 60 GHz at 60 GHz from the gate and drain terminals of FET 16.
4 at a position of λg / 4, and BEF
(Band Eliminate Filter; band rejection filter). That is, by providing a stub with this length at this position, the FET1
When viewed from the 6 side, at 60 GHz, the gate terminal and the drain terminal appear to be open, the base of the stub is short, and the tip of the stub appears to be open, shutting off the power supply and the oscillation circuit for the 60 GHz oscillation signal.

In the voltage controlled oscillator having the configuration shown in FIG. 8, by applying a triangular wave from the modulation terminal at the left end of the figure,
A 60 GHz signal frequency modulated with a triangular wave is generated. FIG. 9 is a diagram illustrating an example of a conventional mixer circuit 12 in a millimeter wave band. The local oscillation signal (LO) and the high frequency signal (RF) are synthesized by the hybrid 28,
0 is applied to the gate terminal. The source terminal of the FET 30 is grounded, and an IF (intermediate frequency) signal having a difference frequency between the two is obtained at the drain terminal due to the non-linear characteristics of the FET. Stubs 32 and 34 provided on the input and output sides
Are designed to maximize the efficiency by matching the impedances on the input side and output side, respectively. The DC power supplies 36 and 38 are for applying predetermined negative and positive DC biases to the gate terminal and the drain terminal, respectively, and the stubs 40 and 42 are provided for cutting off the power supply as described above. .

In general, since a device used for a millimeter-wave oscillator is expensive, a frequency-modulated signal having a frequency that is a fraction of the integer is generated, and the frequency-modulated signal is used after being multiplied. FIG. 10 is a diagram showing a basic configuration in that case. In FIG. 10, a frequency modulated signal is generated by a voltage controlled oscillator 44 of 30 GHz and passed through a multiplier 46 to obtain a signal of 60 GHz.

FIG. 11 is a circuit diagram showing an example of a conventional multiplier 46. The 30 GHz signal is applied to the gate terminal of FET 48. The source terminal of the FET 48 is grounded, and the drain terminal is connected to the FET 48 by the nonlinear characteristic of the FET.
Harmonics of an input signal of 30 GHz including a signal of 0 GHz are obtained, and a signal of 60 GHz which is doubled is obtained by passing through a band-pass filter 50 of 60 GHz formed of a strip line. The stub 52 is for matching the impedance on the input side. Negative and positive biases are applied to the gate terminal and the drain terminal of the FET from DC power supplies 54 and 56, respectively. The stub 58 cuts off the power supply at 30 GHz on the input side, and the stub 60 cuts off the power supply at 60 GHz on the output side.

[0009]

As described above, FIG.
Conventionally, in order to realize the FM-CW radar having the basic configuration shown in FIG. 10, an oscillation circuit having the configuration shown in FIG. 8 and a mixer having the configuration shown in FIG. 9 must be used. In order to realize the FM-CW radar having the basic configuration described above, the multiplier shown in FIG. 11 and the mixer shown in FIG. 9 must be used. In each case, a large-scale circuit using an expensive millimeter-wave device is required. Becomes

Accordingly, an object of the present invention is to provide an oscillator / mixer circuit and a multiplier capable of realizing a small and inexpensive Doppler radar or FM-CW radar by providing a millimeter wave device with two or more functions. vessel·
An object of the present invention is to provide a circuit that can be used as a mixer.

[0011]

An oscillator / mixer circuit according to the present invention for achieving the above object outputs an output signal having a predetermined frequency which is frequency-modulated by a modulation signal, and outputs the frequency of an input signal and the output signal. A baseband signal having a frequency different from the frequency of the signal is output. The device includes an element having a non-linear characteristic, and outputs an output signal having the predetermined frequency that changes according to the voltage of the applied modulation signal. A voltage-controlled oscillator, a coupling element inserted into the voltage-controlled oscillator to couple the input signal to the line on which the output signal is present, and an element for blocking the signal of the predetermined frequency. A baseband signal output terminal connected to an oscillator for extracting the baseband signal.

A multiplier / mixer circuit according to the present invention, which achieves the above object, outputs an output signal obtained by multiplying a first input signal, and outputs a signal between a frequency of a second input signal and a frequency of the output signal. A multiplier for outputting a baseband signal having a difference frequency, including an element having a non-linear characteristic, receiving the first input signal, multiplying the first input signal, and outputting the multiplied signal as the output signal; A coupling element coupled to the multiplier to couple the second input signal to an existing line; and the baseband signal coupled to the multiplier via an element that blocks signals at the frequency of the output signal. A baseband signal output terminal for taking out.

[0013]

In the oscillator / mixer circuit according to the present invention,
By coupling the input signal to the voltage controlled oscillator and extracting the baseband signal, the non-linear element also acts as a mixer, with the voltage controlled oscillator 10, mixer 12, and directional coupler 14 shown in FIG. The functions are realized simultaneously, and the number of elements is significantly reduced.

In the multiplier / mixer combination circuit of the present invention, the nonlinear element also serves as a mixer by coupling the second input signal to the multiplier and extracting the baseband signal, as shown in FIG. The functions of the multiplier 46, the mixer 12, and the directional coupler 14 are simultaneously realized, and the number of elements is significantly reduced.

[0015]

FIG. 1 is a circuit diagram showing an oscillator / mixer shared circuit according to an embodiment of the present invention. The FET composed of GaAs FET or HEMT (heterojunction FET), together with the resonator 17, the variable capacitance diode 18, the inductive element 19, the stubs 20, 21, 22, and the resistors 24, 26 constitute the voltage controlled oscillator already described in FIG. . That is, a signal having a frequency equal to the resonance frequency of the resonator 17 is output as a radar transmission signal, and when a modulation signal is applied to one end of the inductive element 19, a frequency-modulated signal is output.

The received signal reflected by the object and received by the receiving antenna is coupled from the directional coupler 62 to the gate terminal of the FET 16. Then, due to the non-linear characteristics of the FET 16, the frequency of the difference between the transmission signal and the reception signal appears at the drain terminal (and the gate terminal), and is extracted as a baseband signal via the stub 22 that blocks the transmission signal and the reception signal. it can. Since the resistor 26 has an inductance capable of blocking a signal of the frequency of the baseband signal, the resistor 26 cuts off the baseband signal from the power supply.

FIG. 2 is a circuit diagram showing another example of an oscillator / mixer circuit according to the present invention. As shown in FIG.
The received signal can be coupled from the drain side of the FET 16 via the directional coupler 64. The extraction of the baseband signal is also possible from the gate terminal side. In this case, the inductance of the resistor 24 blocks the baseband signal from the power supply.

FIG. 3 is a diagram showing another example of an oscillator / mixer circuit according to the present invention. In the example of FIG. 3, the FE that can directly oscillate a signal in the millimeter wave band, for example, 60 GHz, is used.
Since T is expensive, a method of oscillating and multiplying by oscillating at a frequency that is a fraction of the desired frequency and extracting its harmonics through a high-pass filter is used. If the desired frequency is 60 GHz, for example, the resonance frequency of the stripline resonator 66 is half that of 30 GHz, and the FET 68 constitutes a 30 GHz oscillator. The stubs 21 and 22 function as a 60-GHz band rejection filter.
2 functions as a 30 GHz band rejection filter. The bent portions of the stubs 70 and 72 shown in the figure have no particular meaning. The output of the oscillator is guided through a waveguide strip path converter 74 to a waveguide 76 for 60 GHz. That is, the waveguide 76 guides the signal to the transmitting antenna, but at the same time, blocks the signal of 30 GHz and
It also functions as a high-pass filter that extracts only GHz signals.

The directional coupler 62 for coupling the received signal is provided on the gate terminal side of the FET 68 as shown in FIG. 3 similarly to the example of FIGS. May be provided. The baseband signal takeout port may be provided so as to take out from the drain terminal side as shown in FIG. 3 or may be provided so as to take out from the gate terminal side as in FIG.

FIG. 4 is a diagram showing an example in which a Gunn diode is used as a non-linear element for oscillation and mixing. A bias circuit for supplying a bias voltage to the Gunn diode 78 includes a DC power supply 80, an inductive element 82, a resistor 8
4 and a capacitor 86, and a frequency modulation signal is obtained by superimposing a modulation signal on the voltage of the DC power supply 80. The stub 88 is provided to separate the Gunn diode 78 and the bias circuit at the oscillation frequency.

The received signal is combined with the transmitted signal by a directional coupler 90, and a baseband signal is extracted via a stub 88. FIG. 5 is a circuit diagram showing an example of a multiplier / mixer circuit according to the present invention. The FET 48, together with the stubs 52, 58, and 60, the bias power supplies 54 and 56, and the band-pass filter 50 constitute the multiplier described in FIG.

The received signal is 30
G is synthesized with the frequency modulation signal of G,
It is supplied to the gate terminal of T48. The baseband signal appearing on the drain terminal side due to the non-linearity of the FET 48 is extracted via the stub 60. The choke 94 is provided to cut off the baseband signal from the power supply 56.

The received signals may be coupled by a directional coupler provided on the gate terminal side or the drain terminal side of the FET 48 as described with reference to FIGS. Also, as described with reference to FIG. 3, the function may be substituted by a waveguide without providing the band-pass filter 50. FIG. 6 is a circuit diagram showing another example of a multiplier / mixer circuit according to the present invention, which is based on a multiplier utilizing the nonlinearity of a Schottky diode.

A Schottky diode 96, a band-pass filter 98, stubs 100 and 102, and a resistor 104 constitute a multiplier using a Schottky diode. The received signal is synthesized by the hybrid 106 into a frequency modulation signal of 30 GHz and supplied to the anode of the Schottky diode 96. The bias of the Schottky diode is resistor 10
4 is obtained by a self-bias due to a voltage drop of a DC component of a signal appearing at both ends of the signal. The baseband signal is a stub 10
2 and the resistor 104.

[0025]

As described above, according to the present invention, an oscillator and a radar capable of realizing a small and inexpensive radar device are provided.
Provided are a mixer circuit and a multiplier / mixer circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an oscillator / mixer circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of an oscillator / mixer circuit according to the present invention.

FIG. 3 is a circuit diagram showing another embodiment of the combined oscillator / mixer circuit of the present invention.

FIG. 4 is a circuit diagram showing another embodiment of an oscillator / mixer circuit according to the present invention.

FIG. 5 is a circuit diagram showing an embodiment of a multiplier / mixer circuit according to the present invention.

FIG. 6 is a circuit diagram showing another embodiment of a multiplier / mixer circuit according to the present invention.

FIG. 7 is a block diagram illustrating a basic configuration of an FM-CW radar.

FIG. 8 is a circuit diagram illustrating an example of a conventional voltage controlled oscillator.

FIG. 9 is a circuit diagram illustrating an example of a conventional mixer.

FIG. 10 is a block diagram illustrating a basic configuration of an FM-CW radar using a multiplier.

FIG. 11 is a circuit diagram showing a configuration of a conventional multiplier.

[Explanation of symbols]

 Reference Signs List 16 FET 17 Stripline resonator 18 Variable capacitance diode 20, 21, 22 Stub 62 Directional coupler

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Ikuno 1-2-2, Goshodori, Hyogo-ku, Kobe, Hyogo Prefecture Inside Fujitsu Ten Limited (72) Inventor Eiki Shiratori 1st Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture No. 2-25, Fujitsu Tohoku Digital Technology Co., Ltd. (56) References JP-A-3-78679 (JP, A) JP-A-5-27010 (JP, A) JP-A-5-240942 (JP, A) JP-A-5-240946 (JP, A) JP-A-62-179679 (JP, A) JP-A-60-191980 (JP, U) Table 3-3-505636 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01S ^7/ 00-7/42 G01S 13/00-13/95

Claims (12)

(57) [Claims] An oscillator / mixer circuit that outputs an output signal of a predetermined frequency that is frequency-modulated by a modulation signal and that outputs a baseband signal having a frequency that is the difference between the frequency of the input signal and the frequency of the output signal. A voltage-controlled oscillator that includes an element having a non-linear characteristic and outputs an output signal of the predetermined frequency whose frequency changes in accordance with the voltage of the applied modulation signal; and a line on which the output signal exists. A coupling element inserted into the voltage controlled oscillator for coupling the input signal; and a base for extracting the baseband signal connected to the voltage controlled oscillator via an element for blocking a signal of the predetermined frequency. An oscillator / mixer circuit comprising a band signal output terminal. 2. The voltage-controlled oscillator according to claim 1, wherein the voltage-controlled oscillator includes a field-effect transistor as the non-linear element, a resonator connected to a gate terminal of the field-effect transistor, and having a resonance frequency substantially equal to the predetermined frequency. 2. The oscillator / mixer circuit according to claim 1, further comprising a variable capacitance element connected in parallel and having a capacitance value that changes according to an applied voltage. 3. The voltage controlled oscillator includes a field effect transistor as the non-linear element, and a resonance connected to a gate terminal of the field effect transistor and having a resonance frequency substantially equal to an integer fraction of the predetermined frequency. The oscillator / mixer circuit according to claim 1, further comprising: a resonator; and a variable capacitance element connected in parallel to the resonator and having a capacitance value that changes according to an applied voltage. 4. An oscillator / mixer circuit according to claim 2, wherein said coupling element is inserted on a gate terminal side of said field effect transistor. 5. The circuit according to claim 2, wherein said coupling element is inserted on a drain terminal side of said field effect transistor. 6. The oscillator / mixer circuit according to claim 2, wherein said baseband signal output terminal is provided on a drain terminal side of said field effect transistor. 7. The oscillator / mixer circuit according to claim 2, wherein said baseband signal output terminal is provided on a gate terminal side of said field effect transistor. 8. The circuit according to claim 1, wherein said voltage controlled oscillator includes a diode as said nonlinear element. 9. A doubler / mixer for outputting an output signal obtained by multiplying a first input signal and outputting a baseband signal having a frequency difference between the frequency of the second input signal and the frequency of the output signal. A multiplier including an element having a non-linear characteristic, receiving the first input signal, multiplying the first input signal, and outputting the multiplied signal as the output signal; and a second input signal on a line where the output signal exists. And a baseband signal output terminal for extracting the baseband signal connected to the multiplier via an element for blocking a signal having a frequency of the output signal. And a circuit for both a multiplier and a mixer. 10. The multiplier according to claim 9, wherein the multiplier includes a field-effect transistor as the nonlinear element.
Mixer shared circuit. 11. The coupling element includes a hybrid that combines the first input signal and the second input signal and applies the combined signal to the gate terminal of the field effect transistor.
Circuit for doubler / mixer described in 0. 12. The circuit as claimed in claim 9, wherein the multiplier includes a diode as the nonlinear element.