JP2007306208A - Transmission device and variable gain frequency converting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise by decreasing the number of circuit stages of an RF front-end section and to perform low-source-voltage operation by adaptively adjusting a bias of a circuit. <P>SOLUTION: A frequency converting circuit equipped with a gain varying function is constituted by providing another cascade stage paired with a cascade stage operating as a switch means of a gilbert circuit. The gain varying function is obtained by applying differential voltages for control to bases of transistors of the cascade stages respectively. A control voltage generating circuit has a middle-point voltage detecting function for the differential voltages for control, an adjustment target voltage generating function, and a differential voltage generating function. A control current is controlled by negative feedback according to the voltage difference between an adjustment target voltage and a middle-point voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission apparatus mainly used for mobile communication, and more particularly to a transmission apparatus that realizes low noise by reducing the number of circuit stages of an RF front end unit.

In recent years, mobile communication technologies such as mobile phones and wireless LANs have become widespread. The RF front end of a mobile communication terminal normally upconverts an analog baseband signal to an RF band using a frequency converter (orthogonal modulator), limits the band using a bandpass filter, and then further amplifies the gain. The general configuration is that the transmission power is amplified by a circuit. In recent wireless communication devices, as a frequency converter for up-converting a baseband signal, a direct conversion method is used in which frequency conversion is directly performed on the baseband signal by multiplication with the local frequency _fLO . According to the direct conversion method, since an IF (Intermediate Frequency) filter is not used, it is easy to increase the bandwidth of the receiver, and the configuration flexibility of the receiver is increased.

  Here, a W-CDMA (Wideband Code Division Multiple Access) system is known as one of the radio interface standards defined by the international standard IMT-2000 for third generation mobile communication. In this type of communication system, a plurality of communicators share the same frequency band, so that a low-power transmission signal received from a mobile station far from the base station becomes a high-power transmission signal received from a nearby mobile station. The perspective problem of being buried occurs. This problem can occur in mobile stations as well as base stations. For this reason, “power control” for adjusting transmission power from the mobile station and the base station is indispensable.

  When closed loop control of transmission power is applied, transmission power control is performed based on TPC (Transfer Power Control) bits included in the received signal in both the base station and the mobile station. For example, the base station side measures the received signal disturbance wave power ratio of the desired signal, and compares the target signal / failure wave output ratio obtained from the block error rate BER with the received signal disturbance wave output ratio to determine the increase or decrease in power. The transmission power that enables the power to be increased and decreased by defining the TPC bit in the transmission frame of the signal from the base station side to the mobile station and to reduce the transmission power from the mobile station in the vicinity of the base station Proposals have been made for control devices (see, for example, Patent Document 1).

  Thus, in a communication system that requires transmission power control, a variable range close to 90 dB is required for the variable gain amplifier circuit. However, in order to avoid the difficulty in high-frequency isolation and the problem of carrier leakage, the variable range of one gain variable amplifier circuit is about 30 dB, so a three-stage configuration as shown in FIG. In general, a configuration in which a variable range close to 90 dB is realized by using an amplifier circuit is used.

  For example, a variable gain amplification means for amplifying a received signal with a gain controlled by a plurality of stages of a variable gain amplification section for coarse adjustment and a variable gain amplification section for fine adjustment connected in series. A proposal has been made on a portable communication terminal device provided with (for example, see Patent Document 2).

  Future mobile terminals are further required to operate with low power supply voltage and to reduce noise. In particular, in order to reduce noise, it is essential to reduce the number of stages in the subsequent circuit of the frequency conversion circuit. In addition, the present inventors consider that it is necessary to adaptively adjust the bias of the circuit in order to realize low power supply voltage operation.

WO97 / 50197 Japanese Patent Laying-Open No. 2005-167519

  An object of the present invention is to provide an excellent transmission device that is mainly used for mobile communication and can realize low noise by reducing the number of circuit stages of an RF front end unit.

  It is a further object of the present invention to provide an excellent transmitter having a circuit configuration suitable for low power supply voltage operation by adaptively adjusting the bias in the RF front end section.

  The present invention has been made in consideration of the above-described problems, and is a transmission device including a frequency conversion circuit with a gain conversion function and one or more gain variable amplification circuits as an RF front end unit. .

  In a communication system that requires transmission power control such as W-CDMA, a variable range close to 90 dB is required. Therefore, a variable gain amplifier is configured in a multi-stage connection configuration in the RF front end of the transmitter. Is common. However, in order to reduce the noise of the mobile terminal, it is necessary to reduce the number of stages in the subsequent circuit of the frequency conversion circuit. In order to realize the low power supply voltage operation, it is necessary to adaptively adjust the bias of the circuit.

  In the present invention, the use of the quadrature modulation circuit having a variable gain function as the frequency conversion circuit for up-converting the baseband signal reduces the number of stages of the variable gain amplification circuit at the subsequent stage, thereby realizing low noise. Can do.

  A Gilbert circuit is known as a frequency conversion circuit. The Gilbert circuit has a voltage conversion gain, and approximately the ratio between the output load Rc1 in the switch stage and the resistor RE1 in the amplification stage is a gain. However, RE1 is a resistor loaded for degeneration, and has a role of eliminating the distortion of the analog baseband signal and having linearity with respect to the amplitude width. Therefore, if RE1 is variably controlled so that the Gilbert circuit has a gain conversion function, the linearity with respect to the analog baseband signal is deteriorated in a region where RE1 is controlled to be small, and a distortion component is generated. .

  Therefore, in the transmission device according to the present invention, the frequency conversion circuit with a gain conversion function includes the first current stage, the amplification stage, the first switch stage, and the output load with respect to the Gilbert circuit connected in series. And a second switch stage connected in parallel to the switch stages. The input signal input to the amplification stage and the local signal input to the first switch stage are mixed and output from between the first switch stage and the output load. At this time, the gain of the mixed output signal with respect to the input signal is adjusted by adjusting the magnitude of the bias current supplied to each switch stage based on the control differential voltage applied to the first and second switch stages. Can be adjusted.

Specifically, the amplification stage includes a pair of transistors Tr1 and Tr2, and is grounded via a constant current source that supplies a bias current I _bias to the emitters of the transistors Tr1 and Tr2.

The first cascode stage that operates as a switch stage comprises two pairs of transistors Tr3 and Tr4 and Tr5 and Tr6, and the emitters of one pair of transistors Tr3 and Tr4 are connected in series to the collector of one transistor Tr1 in the amplification stage. The emitters of the other pair of transistors Tr5 and Tr6 are connected to the collector of the other transistor Tr2 in the amplification stage. A constant voltage power supply _Vcc is connected via output loads Rc1 and Rc2 connected in series to the collectors of the transistor pairs Tr3 and Tr5 and Tr4 and Tr6 in the first cascode stage, respectively.

The second cascode stage connected in parallel with the first cascode stage is composed of two pairs of transistors Tr7, Tr8, Tr9 and Tr10, and each pair of transistors Tr3, Tr4 and Tr5 constituting the first cascode stage. Tr6 and emitter are connected to each other, and the collectors of cascode-connected transistor pairs Tr7 and Tr9 and Tr8 and Tr10 are connected to a constant voltage power supply _Vcc .

Differential inputs to the bases of the transistors Tr1 and Tr2 constituting the amplifier stage input signal V _in is supplied, also, the first and second cascode by AC coupling a differential input of the local signal V _LO Applied to the base of the stage transistor pair. And the output voltage _Vout of the mixed signal of an input signal and a local signal is taken _out via output load Rc1 and Rc2.

When a differential control voltage (V _c −V _cX ) is differentially input to the bases of the transistor pair of the first and second cascode stages, a second DC voltage is applied to V _c as compared with V _cX . The bias current supplied to the first cascode stage is larger than that of the first cascode stage, and the gain is increased. On the other hand, when a DC voltage lower than V _cX is applied to V _c , the bias current supplied to the first cascode stage is smaller than the second cascode stage, and the gain is reduced. Therefore, the gain of the frequency conversion circuit can be made variable by the control differential voltage.

Here, when the gain is adjusted using the differential voltage (V _c −V _cX ) in a low power supply voltage environment, it is necessary to control the midpoint of V _c and V _cX with higher accuracy. Therefore, it is preferable that the transmission device further includes a differential voltage generation unit that supplies a differential voltage in which the midpoint voltage is adjusted with respect to the control differential voltage. The differential voltage generation means includes, for example, a means for detecting the midpoint voltage of the control differential voltage, a means for generating the adjustment target voltage, and a means for generating the differential voltage, and the detected midpoint voltage The control current is variably controlled by negative feedback according to the difference in the adjustment target voltage. The midpoint voltage of the differential voltage (V _c −V _cX ) can be stably generated against process variations and temperature changes of the semiconductor device.

  Further, by controlling the gain of the variable gain amplifier circuit using the differential voltage for control by the differential voltage generating means, it becomes possible to supply a stable bias, so that the linearity at the time of low power supply voltage operation is ensured. be able to.

  According to the present invention, it is mainly used for mobile communication, and can be used for an excellent transmission apparatus and RF front end unit that can realize low noise by reducing the number of circuit stages of the RF front end unit. A gain variable frequency conversion circuit can be provided.

  In addition, according to the present invention, by adjusting the bias in the RF front end section adaptively, an excellent transmission apparatus having a circuit configuration suitable for low power supply voltage operation, variable gain used in the RF front end section A frequency conversion circuit can be provided.

  According to the transmitting apparatus of the present invention, a bias voltage supplied to each cascode stage is controlled by applying a control differential voltage using a frequency conversion circuit in which two cascode stages are connected in parallel. Since the variable gain function is realized, the number of subsequent variable gain amplifier circuits can be reduced.

  Further, the control differential voltage includes means for detecting a midpoint voltage of the control differential voltage, means for generating the adjustment target voltage, and means for generating the differential voltage, and according to a difference between the detected midpoint voltage and the adjustment target voltage. By using a differential voltage generation circuit that variably controls the control current using negative feedback, a control differential voltage with a stable midpoint voltage can be supplied to the variable gain frequency converter circuit even with process variations and temperature changes. Can do. Furthermore, by controlling the gain of the variable gain amplifier circuit using the control operating voltage generated by this differential voltage generation circuit, it becomes possible to supply a stable bias and to improve the linearity even when the device operates at a low power supply voltage. Is done.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows the configuration of the RF front end unit used in the transmission apparatus according to the present invention. As shown in the figure, by using a quadrature modulation circuit with a variable gain function as the frequency conversion circuit that upconverts the baseband signal, the number of stages of the variable gain amplification circuit at the subsequent stage can be reduced, and the noise can be reduced. Can be realized.

  A frequency conversion circuit having a frequency conversion gain is also called an “active mixer”, and a Gilbert cell is known. FIG. 2 shows a configuration example of a frequency conversion circuit using a Gilbert circuit.

  In the illustrated Gilbert circuit, an amplification stage composed of a pair of transistors Tr1 and Tr2 and a switch stage composed of two pairs of transistors Tr3, Tr4, Tr5 and Tr6 (hereinafter also referred to as “cascode stage”) are multiplied. Is a circuit connected in series. In the example shown in the figure, the transistors Tr1 and Tr2, Tr3 and Tr4, and Tr5 and Tr6 forming a differential pair are all bipolar transistors, but may be configured by MOS (Metal Oxide Semiconductor) transistors.

Differential input high-frequency signal V _in is applied to the bases of the transistors Tr1 and Tr2, the differential input of the local signal V _LO is applied to the bases of the base and the transistor Tr4 and Tr5 of the transistor Tr3 and Tr6. The collectors of the transistors Tr3 and Tr5 and the collectors of the transistors Tr4 and Tr6 are connected to a high-level power supply via output loads Rc1 and Rc2, respectively, and serve as a balanced output terminal for frequency-converted signals. The emitters of the transistors Tr1 and Tr2 are each grounded via a constant current source that supplies a bias current I _bias , and a load RE1 is connected between the emitters of the transistors Tr1 and Tr2 in order to improve linearity. . The loads Rc1, Rc2, and RE1 may be actual resistances, and may be impedances using AC loads such as L and C.

The currents when the transistors Tr1 and Tr2 are switched by the local input signal V _LO are I ₃ , I ₄ , I ₅ and I ₆ , and when V _LO is negative, I ₃ = I ₁ , I ₄ = 0, I ₅ = 0, I ₆ = I ₂ , and when V _LO is positive, I ₃ = 0, I ₄ = I ₂ , I ₅ = I ₁ , and I ₆ = 0.

Here, an _RF frequency omega of the RF input signal V _RF, the frequency of the local input signal V _LO is assumed to be omega _LO, the output of the Gilbert circuit, the frequency sum component of V _RF and V _LO (ω _LO Two frequency components of an upper side band (USB: Upper Side Band) that becomes + ω _RF ) and a lower side band (LSB: Lower Side Band) that becomes a frequency difference component (ω _LO −ω _RF ) of V _RF and V _LO Is known to be obtained. Therefore, in the transmission system, it is possible to extract only the USB component or the LSB component using a bandpass filter after the Gilbert circuit and use it as an up-conversion mixer. On the other hand, in the receiving system, the LSB component can be extracted and used as a down-conversion mixer.

  The Gilbert circuit is known to have a voltage conversion gain. Basically, it is known that the ratio between the output load Rc1 and the degeneration resistor RE1 is a gain (for example, Watanabe). Kazuo “Practical analog electronic circuit design method”, Chapter 6, High-frequency circuit design method and design considerations (refer to Hirakawa Kogyo, June 22, 1996, 1st edition).

  Therefore, at first glance, the Gilbert circuit shown in FIG. 2 is applied as the gain variable frequency conversion circuit in the RF front end unit shown in FIG. 1, and RE1 is variably controlled according to the transmission power control bit received from the communication partner, for example. By doing so, it is considered that the number of stages of the variable gain amplifier circuit in the subsequent stage can be reduced.

  However, RE1 is a resistor loaded for degeneration, and has a role of providing linearity with respect to the amplitude of the analog baseband signal. Therefore, it is necessary to set the resistance value as high as possible. In other words, if RE1 is variably controlled, linearity with respect to the analog baseband signal deteriorates in a region where RE1 is controlled to be small, and distortion components are generated. Therefore, when applied to a transmission system, RE1 is made variable. It is not a good idea to use them.

  Therefore, in the transmission apparatus according to the present embodiment, the variable gain frequency conversion circuit includes a first cascode for a Gilbert circuit in which a bias current source, an amplification stage, a first cascode stage, and an output load are connected in series. A second cascode connected in parallel to the stage is further provided, and the first and second cascode stages constitute a switch stage. The input signal input to the amplification stage and the local signal input to the first cascode stage are mixed and output from between the first cascode stage and the output load. The gain of the mixed output signal relative to the input signal can be adjusted by adjusting the magnitude of the bias current supplied to each switch stage based on the control differential voltage applied to the first and second cascode stages. it can. Since the frequency conversion function is the same as that of a general Gilbert circuit, the gain variable function will be mainly described below.

  FIG. 3 shows a specific configuration of this variable gain frequency conversion circuit. The illustrated frequency conversion circuit includes a second current connected in parallel to the first cascode stage with respect to a Gilbert circuit in which a bias current source, an amplification stage, a first cascode stage and an output load are connected in series. A cascode stage is further provided.

  That is, a second switch stage having the same configuration as a pair is provided for each of the cascode-connected transistors Tr3, Tr4, Tr5, and Tr6 constituting the first cascode stage. In this second cascode stage, transistors Tr7, Tr8, Tr9, Tr10 are cascode-connected, and the emitters of the transistors of the first and second cascode stages are connected to each other.

A differential voltage (V _c −V _cX ) is applied to the pair of cascode stages via resistors Rb1 and Rb2 and Rb3 and Rb4, and is biased as a base voltage of the transistor.

The local signal (V _LO -V _LOX ) is AC-coupled via capacitances C1, C2, C3, and C4, and is input to both cascode stages that operate as switch stages of the frequency conversion circuit.

The transistors Tr1 and Tr2 in the amplification stage constitute a grounded emitter pair and operate as a transconductance stage that converts an input differential signal (V _in −V _inX ) into a current. The grounded emitter is biased with a tail current _Ibias .

Here, by controlling the signal level of the differential voltage (V _c −V _cX ), the bias current supplied to each cascode stage can be controlled. As a result, the input differential signal (V _in − The signal level of the mixed output differential signal (V _out -V _outX ) of V _inX ) and the local signal (V _LO -V _LOX ) can be variably controlled.

For example, when a higher DC voltage than V _cX is applied to V _c , it is supplied to the first cascode stage consisting of Tr3, Tr4, Tr5, Tr6 compared to the second cascode stage consisting of Tr7, Tr8, Tr9, Tr10. Since the bias currents I ₁₁ and I _{12 to} be applied increase (see FIG. 4), the gain increases. On the other hand, when a DC voltage lower than V _cX is applied to V _c , it is supplied to the first cascode stage consisting of Tr3, Tr4, Tr5 and Tr6 compared to the second cascode stage consisting of Tr7, Tr8, Tr9 and Tr10. Since the bias currents I ₁₁ and I ₁₂ to be applied are reduced (see FIG. 4), the gain is reduced. That is, the gain of the frequency conversion circuit shown in FIG. 3 can be controlled by the differential voltage (V _c −V _cX ) as shown in FIG.

  In the example shown in FIG. 3, all the transistors are bipolar transistors, but may be composed of MOS transistors. Further, the loads Rc1, Rc2, and RE1 may be impedances using AC loads such as L and C in addition to actual resistances.

Here, when the gain is adjusted using the differential voltage (V _c −V _cX ) in a low power supply voltage environment, it is necessary to control the midpoint of V _c and V _cX with higher accuracy. .

FIG. 6 shows an example of the configuration of a differential voltage generation circuit that can supply a differential voltage (V _c −V _cX ) with a stabilized midpoint voltage to the frequency conversion circuit shown in FIG. Is shown. The illustrated differential voltage generation circuit includes a midpoint voltage detection circuit that detects a midpoint voltage of a control differential voltage, an adjustment target voltage generation circuit that generates an adjustment target voltage, and a differential voltage that generates a differential voltage. A generation circuit and a midpoint voltage adjustment circuit that variably controls the control current by negative feedback according to the difference between the detected midpoint voltage and the adjustment target voltage.

  In the frequency conversion circuit shown in FIG. 3, a voltage difference of about +250 mV or −250 mV is required as a differential voltage in order to completely turn off each cascode stage. Unlike the general Gilbert circuit shown in FIG. 2, since the bias voltage supplied to the cascode stage transistor is changed, a bias design is required so that sufficient linearity can be obtained even under this condition. In particular, it is necessary to be more careful when operating at a low power supply voltage.

In the differential voltage generation circuit shown in FIG. 6, the adjustment target voltage generation circuit uses a resistance ratio that can obtain accuracy relatively easily in the IC chip, and divides a constant reference voltage V _ref to adjust the adjustment target. A voltage V _tgt is generated.

Further, the midpoint voltage detection circuit detects a transient midpoint voltage of the control by utilizing that the midpoint voltage of the control differential voltage is always constant. That is, the potential difference between the differential voltages V _c and V _cX is _divided by two resistors to take out the midpoint voltage, and this is fed back to the midpoint voltage adjustment circuit.

In the midpoint voltage adjustment circuit, the midpoint voltage fed back from the midpoint voltage detection circuit and the adjustment target voltage are compared by a comparator (COMP). When the adjustment target voltage is higher than the detection midpoint voltage, the switch SW1 is turned on and the switch SW2 is turned off. Further, the variable current I _var1 is variably controlled in the negative feedback loop according to the voltage difference between the adjusted target voltage and the detected midpoint voltage, so that the detected midpoint voltage is converged to the adjusted target voltage. On the other hand, when the adjustment target voltage is lower than the detection midpoint voltage, the switch SW1 is turned off and the switch SW2 is turned on. Further, the variable current I _var2 is variably controlled in the negative feedback loop according to the voltage difference between the adjustment target voltage and the detection midpoint voltage, so that the detection midpoint voltage is converged to the adjustment target voltage.

  According to such a configuration of the differential voltage generation circuit, it is possible to adaptively adjust the midpoint voltage of the control differential voltage to the adjustment target voltage with high accuracy even for process variations and temperature changes. is there. Therefore, it is possible to stably supply the bias to the frequency conversion circuit, which is important for ensuring linearity with respect to the input analog baseband signal.

  The configuration of the differential voltage generation circuit can also be applied to a subsequent variable gain amplifier circuit.

FIG. 7 shows an example of a simulation result of the differential voltage generation circuit shown in FIG. However, the adjustment target voltage is designed to change in proportion to the power supply voltage V _DD . Here, in order to confirm that the control is applied appropriately, the transient simulation was performed after changing the power supply voltage V _DD and the band gap reference voltage _{V_BG} with time. As shown in the figure, it can be seen that the detected midpoint voltage is controlled following the adjustment target voltage.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In the present specification, the embodiment applied to a transmission apparatus in a communication system requiring transmission power control has been mainly described, but the gist of the present invention is not limited to this. Regardless of whether transmission power control is required or not, transmitters that require a large variable range in an upconverted RF signal gain amplifying circuit or large variable in a downconverted baseband signal gain amplifying circuit The present invention can be similarly applied to a receiver that requires a range.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram schematically showing a configuration of an RF front end unit used in a transmission apparatus according to the present invention. FIG. 2 is a diagram illustrating a configuration example of a frequency conversion circuit using a Gilbert circuit. FIG. 3 is a diagram showing a configuration example of a variable gain frequency conversion circuit according to an embodiment of the present invention. FIG. 4 is a diagram showing a change in bias current supplied to each cascode stage in accordance with the adjustment of the differential voltage (V _c −V _cX ). FIG. 5 is a diagram illustrating a change in the variable gain of the frequency conversion circuit by adjusting the differential voltage (V _c −V _cX ). FIG. 6 shows a configuration example of a differential voltage generation circuit that can supply a differential voltage (V _c −V _cX ) with a stabilized midpoint voltage to the frequency conversion circuit shown in FIG. It is a figure. FIG. 7 is a diagram illustrating an example of a simulation result of the differential voltage generation circuit illustrated in FIG. FIG. 8 is a diagram illustrating a configuration example (prior art) of the RF front end unit of the transmission apparatus.

Claims (8)

As an RF front end unit, a frequency conversion circuit with a gain conversion function and a gain variable amplification circuit having one or more stages are provided.
A transmission apparatus characterized by the above. The frequency conversion circuit with the gain conversion function is
A bias current source, an amplification stage, a first switch stage and an output load are connected in series, and a second switch stage is connected in parallel to the first switch stage,
The input signal input to the amplification stage and the local signal input to the first switch stage are mixed and output from between the first switch stage and the output load, and a mixed output signal corresponding to the input signal Is adjusted by a control differential voltage applied to the first and second switch stages,
The transmission apparatus according to claim 1, wherein: The frequency conversion circuit with the gain conversion function is
An amplification stage composed of a pair of transistors Tr1 and Tr2,
Grounding means for grounding via a constant current source for supplying a bias current I _bias to each emitter of the transistors Tr1 and Tr2 constituting the amplification stage;
Two pairs of transistors Tr3 and Tr4 and Tr5 and Tr6 connected in cascode are connected, and the emitters of one pair of transistors Tr3 and Tr4 are connected in series to the collector of one transistor Tr1 in the amplification stage and the other pair of transistors. A first cascode stage operating as a switch stage with the emitters of Tr5 and Tr6 connected to the collector of the other transistor Tr2 of the amplification stage;
A power supply for applying a constant voltage _Vcc via output loads Rc1 and Rc2 connected in series to the collectors of the transistor pairs Tr3 and Tr5 and Tr4 and Tr6 that are cascode-connected in the first cascode stage, respectively;
Each transistor pair Tr3, Tr4, Tr5, Tr6 and emitters constituting the first cascode stage are connected to each other, and the cascode connection is made. A second cascode stage in which the collectors of the transistor pairs Tr7 and Tr9 and Tr8 and Tr10 are connected to the power source;
Input signal applying means for providing a differential input of an input signal (V _in −V _inX ) to the bases of the transistors Tr1 and Tr2 constituting the amplification stage;
A local signal applying means for applying a differential input of a local signal (V _LO -V _LOX ) to the base of the transistor pair of the first and second cascode stages by AC coupling;
Mixed output for outputting an output voltage V _out of the amplifier stage and the first inputted to the cascode stage input signal V _in and the signal obtained by mixing a local signal V _LO from between the output load and the first cascode stage Means,
Control differential voltage input means for differentially inputting a control voltage (V _c −V _cX ) to the base of the transistor pair of the first and second cascode stages;
The transmission apparatus according to claim 1, further comprising: A differential voltage generating means for supplying a control differential voltage in which a midpoint voltage is adjusted with respect to the control differential voltage;
The transmission apparatus according to claim 3. The differential voltage generating means includes means for detecting a midpoint voltage of the control differential voltage, means for generating an adjustment target voltage, and means for generating a differential voltage, and the detected midpoint voltage and the adjustment target The control current is variably controlled by negative feedback according to the voltage difference.
The transmission apparatus according to claim 4, wherein: The gain control of the variable gain amplifier circuit is performed using a control operating voltage generated by the differential voltage generating means.
The transmission apparatus according to claim 4, wherein: A bias current source, an amplification stage, a first switch stage and an output load are connected in series, and a second switch stage is connected in parallel to the first switch stage,
The input signal input to the amplification stage and the local signal input to the first switch stage are mixed and output from between the first switch stage and the output load, and a mixed output signal corresponding to the input signal Is adjusted by a control differential voltage applied to the first and second switch stages,
A gain variable frequency conversion circuit characterized by the above. An amplification stage composed of a pair of transistors Tr1 and Tr2,
Grounding means for grounding via a constant current source for supplying a bias current I _bias to each emitter of the transistors Tr1 and Tr2 constituting the amplification stage;
Two pairs of transistors Tr3 and Tr4 and Tr5 and Tr6 connected in cascode are connected, and the emitters of one pair of transistors Tr3 and Tr4 are connected in series to the collector of one transistor Tr1 in the amplification stage and the other pair of transistors. A first cascode stage operating as a switch stage with the emitters of Tr5 and Tr6 connected to the collector of the other transistor Tr2 of the amplification stage;
A power supply for applying a constant voltage _Vcc via output loads Rc1 and Rc2 connected in series to the collectors of the cascode-connected transistor pairs Tr3 and Tr5 and Tr4 and Tr6 respectively in the first cascode stage;
Each transistor pair Tr3, Tr4, Tr5, Tr6 and emitters constituting the first cascode stage are connected to each other, and the cascode connection is made. A second cascode stage in which the collectors of the transistor pairs Tr7 and Tr9 and Tr8 and Tr10 are connected to the power source;
Input signal applying means for providing a differential input of an input signal (V _in −V _inX ) to the bases of the transistors Tr1 and Tr2 constituting the amplification stage;
A local signal applying means for applying a differential input of a local signal (V _LO -V _LOX ) to the base of the transistor pair of the first and second cascode stages by AC coupling;
Mixed output for outputting an output voltage V _out of the amplifier stage and the first inputted to the cascode stage input signal V _in and the signal obtained by mixing a local signal V _LO from between the output load and the first cascode stage Means,
Control differential voltage input means for differentially inputting a control voltage (V _c −V _cX ) to the base of the transistor pair of the first and second cascode stages;
A gain variable frequency conversion circuit comprising:

Images