JP3332108B2 - Frequency conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellular phone, a car phone,
The present invention relates to a frequency conversion circuit constituting a quadrature demodulator of a direct conversion receiver used for a pager or the like.

[0002]

2. Description of the Related Art The direct conversion receiving system is a receiving system in which a received high frequency (RF) signal is mixed with a local oscillator signal having substantially the same frequency as this, and the frequency is directly converted to a baseband for detection. FIG. 11 shows a configuration example of a direct conversion receiver. The received signal received from antenna 901 is RF
After passing through the filter 902, the signal is amplified by the RF amplifier 903 and divided into two channels.
At 05, it is mixed with a carrier from local oscillator 907 having substantially the same frequency as the received signal. This local oscillator is connected to a second frequency conversion circuit 9305 via a first frequency conversion circuit 304 and a 90 ° phase shifter 906, respectively. The received signal is converted into a baseband signal having a phase relationship of 90 ° by the first and second frequency conversion circuits, and the channel selection filters 908 and 90
After passing through 9, the signal is amplified by the baseband amplifier and detected (910).

[0003] The direct conversion receiving method is generally used in a superheterodyne type RF stage because it has no intermediate frequency and has no image response in principle because the received signal is directly frequency-converted to baseband. Due to the fact that a steep filter for removing an image is not required and the filter for selecting a baseband channel can be formed into an LSI, recent LSIs have been used.
With the development of the receiver, it is receiving attention as a receiving system that can realize a downsized receiver.

Next, a frequency conversion circuit used in the direct conversion receiver will be described. A circuit well known in the art as a frequency converter used in such a receiver is a single balance multiplier.
This circuit is shown in FIG. Here, 904 of the two frequency conversion circuits 904 and 905 shown in FIG. 11 will be described, but the operation of 905 is the same.

In FIG. 12, input ports 1001 and 1002 are input ports for radio frequency signals. A signal input from the port 1002 requires a large amplitude to perform a switching operation of the differential pair constituted by the transistors 1005 and 1006, and normally receives the reference carrier signal 912 from the local oscillator 907. On the other hand, the port 1001 has a reception signal 911 having a level weaker than that of the normal reference signal.
Is entered. The received signals are transistors 1004, 10
The signal is sent to a single balance multiplier composed of the elements 05 and 1006, mixed with a reference signal from a local oscillator supplied to a port 1002, converted into a baseband frequency signal, and output from a port 1003.

Here, the relationship between the base AC voltage and the collector AC current of the transistor 1004 alone is as follows: ic = Ic × {exp (vbe / VT) −1} = Ic × {(vbe / VT) + (vbe / VT) ) 2/2 + (v be / VT) 3/6 + ...} (1). Here, vbe is a base AC voltage, VT is a threshold voltage of a transistor, Ic is a collector DC current, and ic is a collector AC current.

As shown in FIG. 13, the received signal input from the received signal input port 1001 includes a desired signal 1101 and an adjacent channel signal 1102 in the system. These adjacent channel signals are supplied to an RF filter 9 installed before the frequency conversion circuit.
02 cannot usually be shut off. Therefore, due to the n-th term (n ≧ 2) in the equation (1), a distortion signal is generated in the collector AC current in addition to the radio frequency signal.

As an example, the generation of a distortion signal by a square term will be described with reference to FIG. 1201 is a desired radio frequency wave, and 1202 is an adjacent channel signal of the desired wave. Of the in-band frequencies of the adjacent channel signal 1202, the component 1203 of the frequency f1 and the component 120 of the f2
4 (f1> f2) is the component 1 of f1 in the transistor 1004 according to the term (vbe / VT) 2/2 in the equation (1).
The result of the product of the component 203 and the component 1202 is output as second-order distortion components 1205 and 1206 at the frequency f1 + f2 and the frequency f1-f2.

The second-order distortion components 1205 and 1206 are:
The signal passes through the differential pair constituted by the transistors 1005 and 1006 and is output from the balanced output port 1003.
Here, the second-order distortion signals 1205 and 1206 are connected to the port 1
In 003, since the signals are in-phase signals, if the operations of the differential pair are perfectly balanced, they are canceled and not output.

However, in practice, a completely balanced state cannot be realized due to variations in the characteristics of transistors and passive elements. For example, if the magnitude of the saturation current of the transistor deviates by ± 5%, a DC offset of about 5 mV occurs between the bases of the two transistors forming the differential pair. The variation of the saturation current value varies depending on the area of the transistor, but typically varies by ± 1% to ± 10%. Therefore, due to the unbalance of the differential pair, the relative phases of the signals output to the two ports at the balanced output port 1003 are shifted from each other and cannot be canceled at the port 1003, and the second-order distortion signals 1205, 1205
6 is output from the port 1003. here,
The second-order distortion signal 1206 of the frequency f1 + f2 is cut off by the baseband filter 908 at the next stage, so that the detection circuit 910 is not affected. However, the frequency f1-f2
Of the second-order distortion signal 1205 of the baseband filter 908
Therefore, the signal passes through the baseband filter 908 and affects the detection circuit 910 because the frequency signal is within the transmission band of.

Also, due to the same cause as the second-order distortion signal 1205, a second-order distortion signal 1207 having a frequency band twice as large as the desired wave 1208 at the baseband frequency is output by all the frequency components in the band of the signal 1202. . In the direct conversion method, since the desired received signal is frequency-converted into baseband, the desired signal 1208 and the distortion signal 1207 overlap at the output port 1003, and as a result, the CIR of the receiver is deteriorated.

[0012]

As described above,
In a conventional frequency conversion circuit, a distortion signal of the same band as the desired output signal is generated from the input stage transistor due to an adjacent channel signal of the received signal and the like, and the desired signal is output from the output port overlapping with the desired signal. In the receiver of the system, the CIR has deteriorated.

[0013]

[0014]

According to the present invention, there is provided a frequency conversion circuit for inputting a local oscillation signal having substantially the same frequency as a received signal received by an antenna and outputting a low frequency signal. A frequency conversion circuit comprising means for blocking one or more low-frequency signals between an input port and an output port of a received signal and transmitting the received signal.

[0015]

According to the present invention, a low-frequency component is provided between an input port and an output port of a received signal by providing a transistor circuit that cuts off a low-frequency component and amplifies and transmits only a received signal component in a radio frequency region. A baseband frequency distortion signal caused by an interference signal that is close to the frequency of a desired wave in the frequency domain and cannot be cut off by a filter provided between the antenna and the frequency conversion circuit can be reduced, and the CI of the receiver can be reduced.
The deterioration of R can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. First, the circuit configuration will be described. 108, 1
09 is a DC current source circuit, 108 is a transistor 103
And 109 supplies a DC bias current to the transistors 104 and 105, respectively. Reference numeral 107 denotes a capacitance element, which is set to a capacitance value through which a signal at a reception frequency can be transmitted and a signal at a DC frequency and a signal at a baseband frequency can be sufficiently attenuated. The current source 108 uses, for example, the current source circuits shown in FIGS. 2A to 2E in order to increase the impedance in an alternating current manner. However, a circuit having another configuration having the same effect may be used. Also,
It may be replaced with a resistance element. Similarly, for the current source 109, for example, the current source circuits shown in FIGS. 3A to 3E are used, but a circuit having another configuration having the same effect may be used. Further, it may be replaced with a resistance element. Load 110,
Although 111 is constituted by a resistance element, the portion of 114 may be replaced with an active load constituted by an active element as shown in FIG. The resistor 112 is inserted between the emitter and the ground plane in order to suppress the fluctuation of the bias current due to the temperature characteristic of the transistor 104. However, in order to improve the high frequency operation of the frequency conversion circuit, a resistor is connected in parallel with the resistor 112. The element 113 may be connected.

Next, the operation of this circuit will be described. A reception signal is input to the port 101, and a signal having a frequency substantially equal to the carrier frequency of the desired reception signal output from the local oscillator 907 is input to the port 102. The received signal and the local oscillation signal are multiplied by a multiplier including transistors 104, 105, and 106, and the received signal is converted into a baseband frequency signal.
03 is output. At this time, since the received signal includes an adjacent channel signal in addition to the desired signal, the transistor 1
At 04, a distortion signal is generated from equation (1). For example, a distortion signal is generated at the baseband frequency and twice the frequency of the received signal due to the square term. Among such distortion signals,
The signal generated in the baseband frequency band is
To shut off. Therefore, the transistors 105, 10
6 is unbalanced,
The baseband frequency distortion signal generated from the transistor 104 is not output from the port 103, and the C
The deterioration of IR can be prevented. Further, as shown in FIG. 15, since the band other than the desired channel 1301 is completely cut off by the channel selection filter at the subsequent stage of the frequency circuit, the capacitance of the capacitor 107 is at least equal to or higher than the cutoff frequency of the channel selection filter. The value may be a value that allows transmission of a signal of a frequency and sufficiently blocks signals of other frequencies. Although the embodiment has been described using a bipolar transistor as the transistor, a field effect transistor may be used.

A second embodiment of the present invention will be described with reference to FIG. The basic operation of the frequency conversion circuit described in the present embodiment is almost the same as that of the frequency conversion circuit described in the first embodiment, and therefore, different points from the first embodiment will be described.
First, the circuit configuration will be described. Current source 508 supplies current to transistor 504. The circuit configuration of the current source 508 may be the same as that of the current source 109 described in the first embodiment. The emitter of the transistor 504 is
7 is connected to the emitter of the differential pair constituted by the transistors 505 and 506. Next, the operation will be described. A reception signal is input to the port 501. At this time, a distortion signal is generated in the transistor 504 because the received signal includes an adjacent channel signal in addition to the desired signal. Among such distortion signals, a signal generated in the baseband frequency band is cut off by the capacitor 507,
The output from the port 503 is prevented, and deterioration of the CIR of the receiver is suppressed. Further, the circuit of this embodiment has an effect that the input impedance of the input port 501 of the received signal can be increased. Although the embodiment has been described using a bipolar transistor as the transistor, a field effect transistor may be used.

A third embodiment of the present invention will be described with reference to FIG. The basic operation of the frequency conversion circuit described in the present embodiment is almost the same as that of the frequency conversion circuit described in the first embodiment, and therefore, different points from the first embodiment will be described.
First, the circuit configuration will be described. The current source 609 supplies a direct current to the transistors 604 and 605. The current source 610 supplies a DC current to a differential pair including the transistors 606 and 607. The current source 609 may have the same configuration as the current source 108 described in the first embodiment.
Similarly, the current source 610 is the same as the current source 10 described in the first embodiment.
9 may have the same configuration. The transistor 604 and the collector are connected to the emitter of the transistor 605, and the current source 609 is connected to the collector of the transistor 605. The capacitor 608 is inserted into the collector of the transistor 605 and the emitter of a differential pair including the transistors 606 and 607. Further, the transistor 605
Is based on the receiving frequency by the capacitive element 613.
Grounded at high frequency.

Next, the operation will be described. Port 60
1 receives a received signal. At this time, since the received signal includes the adjacent channel signal in addition to the desired signal, the transistors 604 and 605 generate a baseband frequency distortion signal. However, such a distortion signal
Since the signal is cut off by the capacitor 608, the signal is not output from the port 603, and the CIR of the receiver can be prevented from deteriorating. Further, as described in Japanese Patent Application No. 3-29862, in the frequency conversion circuit used in the direct conversion receiving method, the reception signal input terminal 60 of the local oscillation signal is used.
However, since the signal transmitted from the collector to the emitter of the transistor 605 whose base is grounded is attenuated, in the circuit of this embodiment, the leakage of the local oscillation signal from the reception signal input terminal 601 is reduced. It also has the effect of suppressing. Although the embodiment has been described using a bipolar transistor as the transistor, a field effect transistor may be used.

A fourth embodiment of the present invention will be described with reference to FIG. The basic operation of the frequency conversion circuit described in the present embodiment is almost the same as that of the frequency conversion circuit described in the first embodiment, and therefore, different points from the first embodiment will be described.
First, the circuit configuration will be described. The current source 709 supplies a DC current to a differential pair including the transistors 704 and 705. Similarly, current source 710 includes transistor 70
A direct current is supplied to the differential pair constituted by 6, 707.
The current sources 709 and 710 are the same as the current sources 1 described in the first embodiment.
09 may be the same configuration. Resistors 711 and 712 are connected to the collectors of the transistors 704 and 705, respectively.
A bias current and a bias voltage are applied to the transistors 704 and 705, respectively. 711 and 712 correspond to FIG.
Alternatively, a configuration using active elements as shown in FIG. The base of the transistor 704 is connected to a reception signal input port 701.
And the base of the transistor 705 is connected to the capacitor 7
15, grounding is performed at a high frequency with respect to the frequency of the received signal. Here, instead of grounding at a high frequency, the base of the transistor 705 may also be used as an input port for a received signal, and the received signal may be balanced. The collector of the transistor 705 and the emitter of the differential pair formed by the transistors 706 and 707 are connected through the capacitor 708, but may be connected to the collector of the transistor 704 instead of the collector of the transistor 705.

Next, the operation of this circuit will be described. A reception signal is input to the port 701, and a signal having a frequency substantially equal to the carrier frequency of the desired reception signal output from the local oscillator 307 is input to the port 702. The received signal and the local oscillation signal are multiplied by a multiplier composed of transistors 704, 705, and 706,
The received signal is converted to a baseband frequency signal and output from port 103. At this time, a distortion signal of a baseband frequency is generated in the transistors 704 and 705 by the adjacent channel signal included in the received signal as in the first embodiment. The distortion signal generated in this way is cut off by the capacitance element 107 to prevent the distortion signal from being output from the port 103 and to suppress the deterioration of the CIR of the receiver. Further, unlike the first embodiment, the magnitude of the DC current flowing through the transistors 704 and 705 is set by the current source circuit 709, so that it is difficult to influence the temperature characteristics of the transistors 704 and 705. Further, since the transistors 704 and 705 perform a differential pair operation, an emitter-connected point can be set to an AC grounding point, and a capacitor required for improving high-frequency operation is not required. Further, the transistor 705 is the third
Since the operation is the same as that of the transistor 605 described in the embodiment, the leakage of the local oscillation signal from the reception signal input 701 is suppressed. Although the embodiment has been described using a bipolar transistor as the transistor, a field effect transistor may be used.

A fifth embodiment of the present invention will be described with reference to FIG. The basic operation of the frequency conversion circuit described in the present embodiment is almost the same as that of the frequency conversion circuit described in the first embodiment, and therefore, different points from the first embodiment will be described.
First, the circuit configuration will be described. The current source 812 supplies a DC current to a differential pair including the transistors 804 and 805. Similarly, a current source 813 is a differential pair constituted by transistors 806 and 807, and
8, 809 are supplied with a direct current. Current sources 812, 81
3 and 814 are the current sources 10 described in the description of the first embodiment.
9 may have the same configuration. The resistors 815 and 816 apply a bias current and a collector bias voltage to the transistors 804 and 805, respectively. However, the resistors 815 and 816 may be constituted by active elements as shown in FIG. 4A described in the description of the third embodiment. Capacitance elements 810 and 811 are set to have a capacitance value through which signals at the reception frequency can be transmitted, and DC signals and signals at the baseband frequency can be sufficiently attenuated.

Next, the operation of this circuit will be described. A reception signal is balanced-input to the port 801, and a signal having a frequency substantially equal to the carrier frequency of the desired reception signal output from the local oscillator 307 is balanced-input to the port 802. The received signal and the local oscillation signal are multiplied by a multiplier composed of three transistor differential pairs, and the received signal is converted into a baseband frequency signal.
Output from At this time, similarly to the first embodiment, a baseband frequency distortion signal is generated in the transistors 804 and 805 by the adjacent channel signal included in the received signal. The distortion signal generated in this way is
Blocking by 0 and 811 prevents output from the port 803, thereby suppressing deterioration of the CIR of the receiver. In the circuit of this embodiment, since the port 801 is also input to the differential pair, the size of the input signal is not limited, and the port 801 may be used for local transmission signal input and the port 802 may be used for reception signal input. Although the embodiment has been described using a bipolar transistor as a transistor, a field effect transistor may be used.

A sixth embodiment of the present invention will be described with reference to FIG. First, the circuit configuration will be described. A current source circuit 1409 supplies a DC bias to the transistor 1404. An AC signal from the first signal source 1401 is supplied to a base electrode of a transistor 1404, and a collector current of the transistor 1404 is set to a differential transistor 1405,
It flows to the emitter electrode 1406. Second signal source 140
2 from the differential transistors 1405, 140
The signal after the frequency conversion is output from the output terminal 1403 by being supplied between the base electrodes 6 and 6 and performing a multiplying operation by the transistor 1404 and the differential transistors 1405 and 1406.

Here, by connecting a capacitor 1410 to the emitter electrode of the transistor 1404 in parallel with the current source circuit 1409, a high-frequency signal near the reception frequency flows to the ground via the capacitor 1410, and a low-frequency signal in the baseband band. Only the frequency signal is cut off. Since the current source circuit in parallel with the capacitor 1410 has high impedance when viewed from the connection point side with the transistor 1404, the transistor 1404 operates in such a manner that the gain of the transistor 1404 is low in a low frequency region and the gain of the transistor 1404 is high in a high frequency region. . Therefore, even when a distortion component exists in the low frequency region, it is possible to amplify only the received signal component in the high frequency region while suppressing the gain of the distortion component in the low frequency region.

Next, a seventh embodiment of the present invention will be described with reference to FIG. 1512 and 1513 are current source circuits for supplying DC bias to the transistors 1504 and 1505, respectively. The first signal source 1501 is a transistor 15
An AC signal is supplied between the base electrodes of the transistors 1504 and 1505, and the collector currents of the transistors 1504 and 1505 are changed by the differential transistors 1506, 1507 and 1508, respectively.
It flows to the emitter electrode 1509. Second signal source 150
2 from the differential transistors 1506, 150
7 and 1508, supplied between the base electrodes of 1509,
A multiplication operation is performed with each of the transistors 1504 and 1505. Differential transistors 1506 and 1508 and 1
Collector electrodes 507 and 1509 are connected to each other, and a signal after frequency conversion is output from an output terminal 1503.

A capacitive element 1514 is connected between the emitter electrodes of the transistors 1504 and 1505 so that the emitter electrodes are short-circuited in a high frequency region and the emitter electrodes are open in a low frequency region. Works. The current source circuit 151
2 and 1513, the gain of the transistors 1504 and 1505 is low in the low frequency region, and the transistors 1504 and 1505 in the high frequency region.
The gain of 1505 increases. Therefore, since only the signal component in the high frequency region is amplified without amplifying the distortion component in the low frequency region, it is possible to provide a frequency conversion circuit in which the occurrence of distortion is suppressed.

In summary, according to the present invention, a radio frequency signal input from an antenna is mixed with an output signal from a local oscillator having a frequency equal to or close to the radio frequency signal, and a desired wave is output to a baseband band. In a frequency conversion circuit, by inserting a capacitor between a transistor receiving a received signal and a transistor receiving a local oscillation signal, a distortion signal generated in a baseband band due to an adjacent channel signal is cut off and output. And it is possible to improve the receiving sensitivity characteristics of the receiver.

[0030]

As described above, in the frequency conversion circuit of the present invention, one of the channel intervals used in the system is used in the circuit.
By intercepting a signal having a frequency equal to or lower than the frequency of / 2 and inserting a capacitive element capable of transmitting signals of other frequencies, the output of a distortion signal generated at the frequency of the desired channel is suppressed, and the CIR of the receiver is degraded. Has the effect of preventing.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first embodiment of a frequency conversion circuit according to the present invention;

FIG. 2 is a diagram showing an example of a current source circuit used in the frequency conversion circuit according to the present invention.

FIG. 3 is a diagram showing an example of a current source circuit used in the frequency conversion circuit according to the present invention.

FIG. 4 is a diagram showing an example of an active load circuit used in the frequency conversion circuit according to the present invention.

FIG. 5 is a diagram for explaining a second embodiment of the frequency conversion circuit according to the present invention.

FIG. 6 is a diagram for explaining a third embodiment of the frequency conversion circuit according to the present invention;

FIG. 7 is a diagram for explaining a frequency conversion circuit according to a fourth embodiment of the present invention;

FIG. 8 is a diagram for explaining a fifth embodiment of the frequency conversion circuit according to the present invention.

FIG. 9 is a diagram illustrating a sixth embodiment of the frequency conversion circuit according to the present invention.

FIG. 10 is a diagram for explaining a seventh embodiment of the frequency conversion circuit according to the present invention;

FIG. 11 is a block diagram of a direct conversion receiver.

FIG. 12 is a diagram illustrating a conventional frequency conversion circuit.

FIG. 13 is a diagram for explaining adjacent channel signals;

FIG. 14 is a diagram for explaining distortion output to a baseband band;

FIG. 15 is a diagram for explaining a cutoff frequency of a low-pass cutoff filter;

[Explanation of symbols]

101, 102: input port, 103: output port 104, 105, 106: transistor, 107, 11
3 ... Capacitance elements 108, 109 ... Current sources, 110, 111, 112 ... Resistance elements 114 ... Parts replaced by the circuit of FIG. 4 201 ... Power supply voltage ports 202, 203 ... Ports 204, 205 for taking out current or inputting a reference current , 206 ... resistance elements 207, 208, 209, 210 ... transistors 301, 302 ... ports for taking out current or inputting a reference current 303, 304, 305 ... resistance elements 306, 307, 308, 309 ... transistors 401, 402 ... resistance elements 4, 403, 404, transistor 405, output port 501, 502, input port, 503, output port 504, 505, 506, transistor, 507, capacitive element 508, 509, current source, 510, 511, resistive element 512, FIG. The part that is replaced by the circuit of 6 01, 602: input port, 603: output port 604, 605, 606, 607: transistor 608, 614, 615: capacitive element, 609, 610 ...
Current sources 611, 612, 613: resistance elements 616: parts replaced by the circuit of FIG. 4 701, 702: input ports, 703: output ports 704, 705, 706, 707: transistors, 70
8, 715: Capacitance element, 709, 710: Current source 711, 712, 713, 714: Resistance element 716, 717: Portion replaced by the circuit of FIG. 4 801, 802: Input port, 803: Output port 804, 805, 806, 807, 808, 809 ... transistors 810, 811 ... capacitance elements, 812, 813, 814 ...
Current sources 815, 816, 817, 818 ... resistance elements, 819,
820: part replaced by the circuit of FIG. 4 901: antenna, 902: RF filter, 903: R
F amplifiers 904, 905: frequency conversion circuit 906: 90 ° phase shift circuit, 907: local oscillator, 908,
909: baseband filter, 910: detector 911: received signal, 912: local oscillation signal 1001, 1002: input port, 1003: output port 1004, 1005, 1006: transistor, 100
7, 1008, 1009: resistance element, 1010: capacitance element 1101, desired signal, 1102, adjacent channel signal,
1103: Out-of-band interference signal, 1104: Characteristics of RF filter 1201: Desired signal, 1202: Adjacent channel signal
1203, 1204... One frequency component of the adjacent channel signal 1205... 1203, a distortion component generated by 1204, 1206.
... desired signal after frequency conversion 1301 ... desired signal, 1302 ... adjacent channel signal 1303 ... baseband distortion signal, 1304 ... characteristic of channel selection filter 1305 ... characteristic of low-pass cutoff filter, 1306 ... channel interval

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-54-100617 (JP, A) JP-A-6-111037 (JP, A) JP-A-6-326520 (JP, A) 88322 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03D 9/00 H03D 7/00 H03D 7/14 H04B 1/26

Claims (7)

(57) [Claims] 1. A enter the local oscillation signal of substantially the same frequency as the received signal and the received signal received by the antenna, the frequency conversion circuit for outputting a low-frequency signal, the transistor and the local oscillation signal input received signal Frequency conversion, characterized in that a capacitance element having a characteristic of blocking a baseband frequency distortion signal generated by the transistor for inputting the reception signal and transmitting the signal at the reception frequency is provided between the input transistor and the input transistor. circuit. 2. A first, comprising a differential pair and a second transistor, the first current source circuit is connected to the emitter of the differential pair, also transistors constituting the differential pair The collector of the third transistor different from the second
Is connected to the emitter of the differential pair and the third
A capacitor is provided between the collectors of the transistors, a local oscillation signal input port is connected to the base of the transistor forming the differential pair, and a reception signal input port is connected to the base of the third transistor. The frequency conversion circuit according to claim 1 , wherein: 3. A differential pair comprising a first transistor and a second transistor, wherein a first current source circuit is connected to an emitter of the differential pair, and a transistor forming the differential pair. The emitter of the third transistor different from the second transistor
Is connected to the emitter of the differential pair and the third
A capacitive element is provided between the emitters of the transistors, and a local oscillation signal input port is connected to a base of the transistor forming the differential pair, and a reception signal input port is connected to a base of the third transistor. The frequency conversion circuit according to claim 1 , wherein: 4. A first, comprising a differential pair and a second transistor, the first current source circuit is connected to the emitter of the differential pair, also transistors constituting the differential pair Unlike the third transistor, a current source is connected to the collector, and a third transistor whose base is grounded at high frequency by a capacitive element and a fourth transistor whose collector is connected to the emitter of the third transistor. A capacitor between the collector of the transistor and the emitter of the differential pair; a local oscillation signal input port connected to the base of the transistor forming the differential pair;
Frequency converter according to claim 1, characterized in that the received signal input port to the transistor is connected. 5. A first, comprises a first differential pair and a second transistor, the first current source circuit is connected to said first differential pair of emitter, also, the difference A second differential pair comprising third and fourth transistors different from the transistors forming the moving pair, wherein a second current source circuit is connected to an emitter of the second differential pair; A capacitor is provided between one of the collectors of the second differential pair and the emitter of the first differential pair, and a local oscillation signal input port is connected to a base of a transistor constituting the first differential pair. is, the third transistor the base or the fourth transistor base or frequency conversion circuit according to claim 1, characterized in that the received signal input port is connected to both constituting the second differential pair. 6. is composed of at least three sets of differential transistor pair, wherein the differential pair of transistors of the emitter is connected to the current source circuit, the first constituting the first differential pair of the differential pairs , A capacitive element is provided between the collector of the first transistor of the second transistor and the emitter of the second differential pair, and between the collector of the second transistor and the emitter of the third differential pair. A capacitor is provided, a base of a transistor forming a first differential pair is connected to an input port of a received signal, and a base of a transistor forming a second and third differential pair is connected to a local oscillation signal input port. 2. The frequency conversion circuit according to claim 1 , wherein the frequency conversion circuit is connected to a frequency conversion circuit. 7. A base of a transistor forming the first differential pair is connected to an input port of a local oscillation signal, and a base of a transistor forming the second and third differential pairs is
7. The frequency conversion circuit according to claim 6 , wherein the frequency conversion circuit is connected to a reception signal input port.