KR100431184B1 - Quad band composite voltage-controlled oscillator in cellular phone - Google Patents

Abstract

The present invention relates to a quad band combined voltage controlled oscillator, the present invention includes: a low pass oscillation selector 51 for supplying an operating voltage according to a low pass select voltage VLB; A high frequency oscillation selector 52 for supplying an operating voltage according to the high frequency selection voltage VHB; A transmission / reception selection unit 53 for supplying a reception operation voltage V _RX or a transmission operation voltage V _TX according to the transmission / reception selection voltage V _RXTX ; The low frequency oscillation oscillation frequency of the low frequency oscillation selector 51 is operated according to the reception or transmission operation voltages V _RX and V _TX . A low frequency oscillator 54 generating the oscillation frequency respectively and oscillating by adjusting the frequency according to the tuning voltage VT; It operates by receiving the operating voltage B + by the high frequency oscillation selector 52, and transmits or transmits a high frequency oscillation frequency according to the reception or transmission operating voltages V _RX and V _TX by the transmission / reception selector 53 or A high frequency oscillator 55 for generating a reception oscillation frequency and oscillating by adjusting the frequency according to the tuning voltage VT; And reception and transmission buffer circuits 56RX and 56TX connected in parallel to the output of the low frequency oscillator 54, wherein the reception and transmission buffer circuits 56RX and 56TX are received or transmitted by the transmission and reception selection unit 53. A low pass buffer unit 56 operating according to the operating voltages V _RX and V _TX ; And reception and transmission buffer circuits 57RX and 57TX connected in parallel to the output of the high frequency oscillator 55, wherein the reception and transmission buffer circuits 57RX and 57TX are received or received by the transmission and reception selection unit 53. The high frequency buffer unit 57 which operates in accordance with the transmission operating voltages V _RX and V _TX is provided, and this configuration includes one such module.

Description

QUAD BAND COMPOSITE VOLTAGE-CONTROLLED OSCILLATOR IN CELLULAR PHONE}

The present invention relates to a quad band multiplexing voltage controlled oscillator, and in particular, it can be applied to a dual wireless mobile phone of the direct conversion method, such as four bands for transmitting and receiving (two for transmitting and two for receiving). The present invention relates to a quad band hybrid voltage controlled oscillator that integrates a voltage controlled oscillator with a single unit, thereby reducing size and cost, diversifying functions, and securing product competitiveness.

In general, a combination of TX VCO and RX VCO applied to existing GSM / DCS Dual Phones is required according to the trend of light and short size of mobile communication terminals.

1 is a block diagram of a conventional dual phone system, referring to FIG. 1, a conventional dual phone system is a dual low-power voltage controlled oscillator which is a dual RX voltage controlled oscillator and provides a GSM type of 1400 MHz and a DCS type 1500 MHz. In addition, a dual high-power voltage controlled oscillator, which is a dual TX voltage controlled oscillator, provides GSM 900MHz and DCS 1800MHz.

FIG. 2 is a block diagram of a dual high-power voltage controlled oscillator of FIG. 1. Referring to FIG. 2, the dual high-power voltage controlled oscillator (TX-VCO) is shown in FIG. Two oscillators 21, oscillator switch 22, and two buffers 23 are configured to selectively provide one of GSM type 900MHz and DCS type 1800MHz. .

FIG. 3 is a block diagram of a dual low-power voltage controlled oscillator of FIG. 1. Referring to FIG. 3, the dual low-power voltage controlled oscillator (RX-VCO) One oscillator switch (31), one oscillator (One Oscillator) 32 and one buffer (One Buffer) 33, including one of 1400MHz GSM and 1500MHz DCS optional It is configured to provide.

However, since the RX voltage controlled oscillator (RX-VCO) and the TX voltage controlled oscillator (TX-VCO) must be manufactured and purchased separately, the production and purchase price of the voltage controlled oscillator applied to the mobile phone increases. Due to the disadvantage that the size is also increased, there is a problem that the applied mobile phone loses the price competitiveness.

The present invention has been made to solve the above problems, and therefore, the object of the present invention can be applied to a dual wireless mobile phone of the direct conversion (Direct Conversion) method, four bands for transmitting and receiving (quad band) (for transmission By integrating a voltage-controlled oscillator with two and two receivers into one, it is possible to provide a quad-band hybrid voltage controlled oscillator that can reduce size and price, diversify functions, and secure product competitiveness. .

1 is a block diagram of a conventional dual phone system.

FIG. 2 is a block diagram of the dual high-power voltage controlled oscillator of FIG. 1.

3 is a block diagram of the dual low-power voltage controlled oscillator of FIG.

4 is a configuration diagram of a quad band combined voltage controlled oscillator according to the present invention.

FIG. 5 is a detailed circuit diagram of the voltage controlled oscillator of FIG. 4.

6 is an application example of the voltage controlled oscillator of the present invention.

Explanation of symbols on the main parts of the drawings

51: low pass oscillation selection unit 52: high pass oscillation selection unit

53: transmission and reception selector 54: low frequency oscillator

54a: resonator 54b: oscillator

55 high frequency oscillator 55a: resonator

55b: Oscillation section 56: Low pass buffer section

56RX: Receive Buffer Circuit 56TX: Transmit Buffer Circuit

57: high pass buffer 57RX: receive buffer circuit

57TX: Transmit Buffer Circuit

As a technical means for achieving the above object of the present invention, the voltage controlled oscillator of the present invention includes a low-frequency oscillation selection unit for supplying an operating voltage according to the low-frequency selection voltage; A high frequency oscillation selector supplying an operating voltage according to the high frequency selection voltage; A transmission / reception selection unit supplying a reception operation voltage or a transmission operation voltage according to the transmission / reception selection voltage; The low-frequency oscillation selector operates by receiving an operating voltage, and generates a low-frequency transmission oscillation frequency or a reception oscillation frequency according to the reception or transmission operation voltage of the transmission / reception selection unit, and adjusts the frequency according to the tuning voltage. Oscillating low frequency oscillation unit; Operating by receiving an operating voltage supplied by the high frequency oscillation selector, generating a high frequency transmission oscillation frequency or a reception oscillation frequency according to a reception or transmission operation voltage of the high frequency oscillation selector, and adjusting the frequency according to a tuning voltage Oscillating high frequency oscillation unit; A receive and transmit buffer circuit connected in parallel to the output of the low pass oscillator, wherein the receive and transmit buffer circuit comprises: a low pass buffer unit operating according to a receive or transmit operating voltage by the transmit and receive selection unit; And a reception and transmission buffer circuit connected in parallel to the output of the high frequency oscillation section, wherein the reception and transmission buffer circuit has a high frequency buffer section operating according to a reception or transmission operation voltage by the transmission and reception selection section. It is characterized by consisting of one module, including.

Hereinafter, the configuration and operation of the quad band combined voltage controlled oscillator according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

4 is a configuration diagram of a quad band combined voltage controlled oscillator according to the present invention, and FIG. 5 is a detailed circuit diagram of the voltage controlled oscillator of FIG.

4 and 5, the quad-band hybridization voltage controlled oscillator according to the present invention is a low-frequency oscillation selector 51 for supplying an operating voltage according to the low-frequency select voltage VLB and the high-frequency select voltage VHB. A high frequency oscillation selector 52 for supplying an operating voltage, a transmit / receive selector 53 for supplying a reception operation voltage V _RX or a transmission operation voltage V _TX according to the transmission / reception selection voltage V _RXTX , and It operates by receiving the operating voltage B + by the low-frequency oscillation selector 51 and operates according to the reception or transmission operating voltages V _RX and V _TX by the transmit / receive selector 53. The oscillation frequency is generated and operated by receiving a low frequency oscillator 54 for oscillating by adjusting the frequency according to the tuning voltage VT and an operating voltage B + by the high frequency oscillation selector 52, and transmitting and receiving the oscillation frequency. a reception by the selection unit 53 or transmits the operating voltage (V _{RX, TX} V) A high frequency oscillator 55 for generating a high oscillation transmission oscillation frequency or a reception oscillation frequency and adjusting the frequency according to the tuning voltage VT and the reception and transmission connected in parallel to the outputs of the low oscillation portion 54; A low pass buffer including buffer circuits 56RX and 56TX, wherein the receive and transmit buffer circuits 56RX and 56TX operate according to the receive or transmit operating voltages V _RX and V _TX by the transmit and receive selector 53. And a reception and transmission buffer circuit 57RX and 57TX connected in parallel to the output of the high frequency oscillation section 55, wherein the reception and transmission buffer circuits 57RX and 57TX are the transmission and reception selection section 53. It consists of a high-frequency buffer unit 57 that operates in accordance with the reception or transmission operating voltage (V _RX , V _TX ).

In particular, the quad band hybrid voltage controlled oscillator according to the present invention includes the above components and is manufactured in one module.

The transmit / receive selector 53 connects a base terminal to the transmit / receive selection voltage V _RXTX terminal, an operating voltage B + terminal to the emitter terminal, and connects the collector terminal to the low frequency oscillator 54, a high frequency region. A base end connected to the first PNP transistor Q1 connected to the transmission operation voltage terminal of each of the oscillator 55, the low pass buffer 56 and the high pass buffer 57, and a collector end of the first PNP transistor Q1. And an operating voltage (B +) terminal to the emitter terminal, and the collector terminal of each of the low frequency oscillator 54, the high frequency oscillator 55, the low frequency buffer 56 and the high frequency buffer 57, respectively. It consists of the 2nd PNP transistor Q2 connected to the receiving operation voltage terminal.

The low pass oscillator 54 is connected to the tuning voltage VT through filters L11 and C11, and the first varactor diode VD11 for varying capacitance according to the tuning voltage VT, and the transmission / reception selection. A second varactor diode VD12 connected to the collector terminal of the second PNP transistor Q2 of the unit 53 and varying capacitance according to the reception operating voltage VRX through the collector terminal, and a plurality of resonant elements. A resonator 54a including (L12, L13, C12, C13) and a base end are connected to the output end of the low oscillation selector 51 through a resistor R13, and from this base end to ground, C15) and two resistors (R14, R15) are connected in series, the collector end of which is connected to the input of the low-pass buffer section 56, and the oscillator for oscillation connected to ground through a capacitor (C16) Two resistors connected between the transistor Q13 and the base terminal of the oscillation transistor Q13 and ground; (R14, R15) A switching transistor having a collector terminal connected to a connection point, a base terminal thereof connected to a collector terminal of a first PNP transistor Q1 of the transmission / reception selector 53, and an emitter terminal connected to ground. It consists of the oscillation part 54b containing Q12).

The high frequency oscillator 55 is connected to the tuning voltage VT through filters L21 and C21, and a third varactor diode VD21 for varying capacitance according to the tuning voltage VT, and the transmission / reception selection. A fourth varactor diode VD22 connected to the collector terminal of the second PNP transistor Q2 of the unit 53 and varying capacitance according to the reception operating voltage VRX through the collector terminal, and a plurality of resonant elements A resonator 55a including (L22, L23, C22, C23) and a base end are connected to the output end of the high frequency oscillation selector 52 through a resistor R23, and the capacitor C25) and two resistors (R24, R25) are connected in series, the collector terminal is connected to the input terminal of the high-frequency buffer section 57, and the oscillator for oscillation connected to the ground through the capacitor (C26) Two low connected between transistor Q23 and ground at the base end of oscillation transistor Q23. A switching transistor in which a collector terminal is connected to the connection points of the terminals R24 and R25, a base terminal thereof is connected to a collector terminal of the first PNP transistor Q1 of the transmission / reception selection unit 53, and the emitter terminal is connected to ground. It consists of the oscillation part 55b containing Q22.

The low pass buffer 56 connects two resistors R16 and R17 in series to the ground at the collector terminal of the second PNP transistor Q2 of the transmission / reception selection unit 53, and the two resistors R16, A transistor Q14 having a base connected to the connection point of R17, a collector connected to the operating voltage B + through filters L14 and C18, and an emitter connected to the output of the low pass oscillator 54. And a receiving buffer circuit 56RX connecting a collector terminal of the transistor Q14 to an output terminal through a first coupling capacitor CC1 and a first PNP transistor Q1 of the transmission / reception selector 53. Connect two resistors in series from the collector stage to ground, connect the base terminal to the connection point of these two resistors, connect the operating voltage (B +) terminal through the filter to the collector terminal, and A transistor connected to an output terminal of the low oscillation unit 54, the collector of the transistor A and a transmission buffer circuit (56TX) connected to the second coupling capacitor (CC2) to the output terminal.

The high frequency buffer unit 57 connects two resistors R26 and R27 in series to the ground at the collector terminal of the second PNP transistor Q2 of the transmission / reception selection unit 53, and the two resistors R26, A transistor Q24 having a base end connected to the connection point of R27, an operating voltage B + terminal connected to the collector end via filters L24 and C28, and an emitter end thereof connected to the output end of the high frequency oscillator 55. And a receiving buffer circuit 57RX in which a collector terminal of the transistor Q24 is connected to an output terminal of a third coupling capacitor CC3, and a first PNP transistor Q1 of the transmission / reception selection unit 53. Connect two resistors in series from the collector stage to ground, connect the base terminal to the connection point of these two resistors, connect the operating voltage (B +) terminal through the filter to the collector stage, and connect the emitter stage to the high range. A transistor connected to the output terminal of the oscillation unit 55, and the collector terminal of the transistor 4 couples to the ring capacitor comprises a transmission buffer circuit (57TX) connected to (CC4) to an output terminal.

FIG. 6 is an application example of the voltage controlled oscillator of the present invention. Referring to FIG. 6, a low-power VCO (902.5-940 MHz) and a low-power VCO (1850) are provided to a receiver using a quad band hybrid voltage controlled oscillator according to the present invention. It can be seen that one of -1920MHz) can be selectively provided and one of high power VCO (880-915MHz) and high power VCO (1710-1785MHz) can be selectively provided to the transmitter. It can be seen that the oscillator can be applied to a mobile phone to provide four desired oscillation frequencies.

Based on the accompanying drawings, the operation of the preferred embodiment of the present invention configured as described above will be described in detail below.

Referring to FIGS. 4 and 5, the operation of the voltage controlled oscillator according to the present invention will be described. First, in the present invention, the low frequency selection voltage VLB or the high frequency selection voltage VHB is selectively supplied, and the transmission / reception selection is performed. The voltage V _RXTX is supplied at a high level or low level to select transmission or reception.

First, when the low pass selection voltage VLB is supplied, the low pass oscillation selector 51 supplies an operating voltage to the low pass oscillator 54, whereby the low pass oscillator 54 is operated. According to the voltage V _RXTX , the reception buffer 56RX or the transmission buffer 56TX inside the low pass buffer 56 is alternately operated. Accordingly, the reception oscillation frequency or transmission for the low pass oscillator 54 is changed. The credit oscillation frequency is alternately provided through the low pass buffer section 56.

On the other hand, when the high frequency selection voltage VHB is supplied, the high frequency oscillation selecting portion 52 supplies an operating voltage to the high frequency oscillation portion 55, thereby operating the high frequency oscillation portion 55. At this time, the reception buffer unit 57RX or the transmission buffer unit 57TX in the high frequency buffer unit 57 alternately operate according to the transmission / reception selection voltage V _RXTX , and thus the number of the high frequency oscillation units 54 is changed. A reliable oscillation frequency or a transmission oscillation frequency is alternately provided through the high frequency buffer section 57.

Hereinafter, an operation of providing a low oscillation frequency in the voltage controlled oscillator of the present invention will be described.

First, when the low pass selection voltage VLB ("LOW") is supplied, the low pass oscillation selector 51 supplies an operating voltage to the low pass oscillator 54, thereby operating the low pass oscillator 54.

At this time, when the transmission / reception selection voltage V _RXTX is at the low level, the transmission / reception selection unit 53 may convert the reception operation voltage VRX to the reception buffer circuit 56RX of the low pass oscillator 54 and the low pass buffer 56. Provide each.

Subsequently, in the resonator 54a of the low oscillator 54, the capacitance of the second varactor diode VD12 varies according to the reception operating voltage VRX, and the first bar according to the tuning voltage VT. The capacitance of the varactor diode VD11 is also variable, so that the low frequency reception frequency is resonant due to the capacitance of these varactor diodes VD11 and VD12 and the capacitance and inductance of the other resonant elements L12, L13, C12, and C13. do.

At the same time, in the oscillation portion 54b of the low oscillation portion 54, the switching transistor Q12 does not operate because the transmission operation voltage VTX is not supplied, and thus the low-frequency reception oscillation is performed to the oscillation transistor Q13. A bias corresponding to the oscillation of the frequency is formed. At this time, the resonant frequency of the resonator 54a is oscillated by the oscillator 54b of the low oscillator 54 and outputs to the low pass buffer 56.

Thereafter, since the reception buffer unit 56RX of the low pass buffer unit 56 is in an operating state, the low pass oscillation frequency from the low pass oscillator 54 is amplified and output.

On the other hand, when the transmission / reception selection voltage V _RXTX is at a high level, the transmission / reception selection unit 53 sets the transmission operation voltage VTX to the transmission buffer circuit 56TX of the low pass oscillator 54 and the low pass buffer 56. To provide.

Subsequently, in the resonator 54a of the low oscillator 54, the reception operating voltage VRX is not supplied, so that the capacitance of the second varactor diode VD12 does not vary, whereas the tuning voltage VT As a result, the capacitance of the first varactor diode VD11 is varied, so that the capacitance of the first varactor diode VD11 and the capacitance and inductance of the other resonant elements L12, L13, C12, and C13 are transmitted. The frequency is resonated.

At the same time, in the oscillation section 54b of the low oscillation section 54, the switching transistor Q12 is operated by the transmission operation voltage VTX to correspond to the oscillation of the low oscillation transmission frequency in the oscillation transistor Q13. The resonance frequency of the resonator 54a is oscillated by the oscillator 54b of the low oscillator 54 and output to the low pass buffer 56.

Thereafter, since the transmit buffer 56TX of the low pass buffer 56 is in an operating state, the low pass oscillation frequency from the low pass oscillator 54 is amplified and output.

Hereinafter, an operation of providing a high frequency oscillation frequency in the voltage controlled oscillator of the present invention will be described.

First, when the high frequency selection voltage VHB is supplied, the high frequency oscillation selecting portion 52 supplies an operating voltage to the high frequency oscillation portion 55, thereby operating the high frequency oscillation portion 55.

At this time, when the transmission / reception selection voltage V _RXTX is at a low level, the transmission / reception selection unit 53 may convert the reception operation voltage VRX to the reception buffer circuit 57RX of the high frequency oscillation unit 55 and the high frequency buffer unit 57. to provide.

Subsequently, in the resonator 55a of the high frequency oscillator 55, the capacitance of the fourth varactor diode VD22 is varied according to the reception operating voltage VRX, and the third bar is also varied according to the tuning voltage VT. The capacitance of the varactor diodes VD21 is also variable, so that the frequency of the high frequency reception is resonated by the capacitances of these varactor diodes VD21 and VD22 and the capacitance and inductance of the other resonant elements L22, L23, C22, and C23. do.

At the same time, in the oscillation section 55b of the high frequency oscillation section 55, the transmission operation voltage VTX is not supplied, so that the switching transistor Q22 does not operate, and thus the oscillation transistor Q23 receives oscillation for reception. A bias corresponding to the oscillation of the frequency is formed. Accordingly, the resonant frequency of the resonator 55a is oscillated by the oscillator 55b of the high frequency oscillator 55 and output to the high frequency buffer 57.

Thereafter, since the reception buffer unit 57RX of the high frequency buffer unit 57 is in an operating state, the high frequency reception oscillation frequency from the high frequency oscillator 55 is amplified and output.

On the other hand, when the transmission / reception selection voltage V _RXTX is at a high level, the transmission / reception selection unit 53 sets the transmission operation voltage VTX to the transmission buffer circuit 57TX of the high frequency oscillation unit 55 and the high frequency buffer unit 57. To provide.

Subsequently, in the resonator 55a of the high frequency oscillator 55, the reception operating voltage VRX is not supplied, so that the capacitance of the fourth varactor diode VD22 does not vary, whereas the tuning voltage VT is varied. As a result, the capacitance of the third varactor diode VD21 is varied, so that the capacitance of the third varactor diode VD21 and the capacitance and inductance of the other resonant elements L22, L23, C22, and C23 are high. The transmission frequency is resonant.

At the same time, in the oscillation section 55b of the high frequency oscillation section 55, the switching transistor Q22 is operated by the transmission operation voltage VTX, and the bias corresponding to the oscillation of the oscillation frequency for transmission to the oscillation transistor Q23. Therefore, the resonant frequency of the resonator 55a is oscillated by the oscillator 55b of the high frequency oscillator 55 and outputs to the high frequency buffer 57.

Thereafter, since the transmission buffer unit 57TX of the high frequency buffer unit 57 is in an operating state, the high frequency transmission oscillation frequency from the high frequency oscillation unit 55 is amplified and output.

As described above, in the voltage controlled oscillator of the present invention, the low band low power (902.5 to 940 MHz) and the low band high power (880 to 915 MHz), And, high band low power (1850 ~ 1920MHz) and high band high power (1710 ~ 1785MHz) can be provided using the same oscillator, respectively, and different low power and high power frequency It can be seen that the difference is performed by the switching of the inductor implemented by the strip line of the oscillator.

According to the present invention as described above, it can be applied to a dual wireless cell phone of the direct conversion (Direct Conversion) method, voltage control having four band (quad band) for transmission and reception (two transmission, two reception) By integrating the oscillator into one, it has the special effect of reducing size and price, diversifying functions, and securing product competitiveness.

The above description is only a description of specific embodiments of the present invention, and the present invention is not limited to these specific embodiments, and various changes and modifications of the configuration are possible from the above-described specific embodiments of the present invention. It will be apparent to those skilled in the art to which the present invention pertains.

Claims (6)

A low frequency oscillation selector 51 for supplying an operating voltage according to the low frequency selection voltage VLB; A high frequency oscillation selector 52 for supplying an operating voltage according to the high frequency selection voltage VHB; A transmission / reception selection unit 53 for supplying a reception operation voltage V _RX or a transmission operation voltage V _TX according to the transmission / reception selection voltage V _RXTX ; It is connected to the operating voltage (B +) output terminal of the low-frequency oscillation selector 51, and connected to the receiving or transmitting operating voltage (V _RX , V _TX ) terminal of the transmission and reception selection unit 53, the reception or transmission operating voltage A low pass oscillation unit 54 for generating a low transmit oscillation frequency or a receive oscillation frequency according to (V _RX , V _TX ), and adjusting the oscillation frequency according to the tuning voltage VT; It is connected to the operating voltage (B +) output terminal of the high frequency oscillation selector 52, and connected to the receiving or transmitting operating voltage (V _RX , V _TX ) terminal of the transmission and reception selection unit 53, the reception or transmission operating voltage A high frequency oscillator 55 for generating a high frequency transmission oscillation frequency or a reception oscillation frequency according to (V _RX , V _TX ), and adjusting a corresponding oscillation frequency according to a tuning voltage VT; And reception and transmission buffer circuits 56RX and 56TX connected in parallel to the output terminal of the low frequency oscillator 54, wherein the reception and transmission buffer circuits 56RX and 56TX are received or transmitted by the transmission and reception selection unit 53. A low-pass buffer 56 selectively operating according to operating voltages V _RX and V _TX to selectively provide an oscillation frequency generated by the low-pass oscillator 54; And And reception and transmission buffer circuits 57RX and 57TX connected in parallel to the output terminal of the high frequency oscillator 55, wherein the reception and transmission buffer circuits 57RX and 57TX are received or transmitted by the transmission and reception selection unit 53. A high frequency buffer unit 57 which selectively operates according to operating voltages V _RX and V _TX to selectively provide an oscillation frequency generated by the high frequency oscillator 55, Quad band complex voltage controlled oscillator, characterized in that configured as a single module including such a configuration. The method of claim 1, wherein the transmission and reception selection unit 53 A base end is connected to the transmit / receive selection voltage (V _RXTX ) end, and an operating voltage (B +) end is connected to the emitter end thereof, and the collector end is connected to the low frequency oscillator 54, the high frequency oscillator 55, and the low frequency buffer part. A first PNP transistor Q1 connected to the transmission operation voltage terminal of each of the 56 and high-pass buffer sections 57; And The base terminal is connected to the collector terminal of the first PNP transistor Q1, and the operating voltage (B +) terminal is connected to the emitter terminal, and the collector terminal is connected to the low frequency oscillator 54, the high frequency oscillator 55, and the low frequency. And a second PNP transistor (Q2) connected to the reception operation voltage terminal of each of the buffer section (56) and the high pass buffer section (57). 3. The low frequency oscillator (54) according to claim 2, wherein A first varactor diode VD11 connected to the tuning voltage VT through filters L11 and C11 and varying capacitance according to the tuning voltage VT, and a second of the transmission / reception selection unit 53. The second varactor diode VD12 connected to the collector terminal of the PNP transistor Q2 and varying the capacitance according to the reception operating voltage VRX through the collector terminal, and the plurality of resonant elements L12, L13, C12, A resonator 54a including C13; A base terminal is connected to the output terminal of the low oscillation selecting section 51 through a resistor R13, and a capacitor C15 and two resistors R14 and R15 are connected in series from the base terminal to ground, and the collector thereof. A stage is connected to an input terminal of the low pass buffer section 56, and an oscillator transistor Q13 having its emitter terminal connected to ground through a capacitor C16, and between the base terminal of the oscillation transistor Q13 and ground. The collector terminal is connected to two connected resistors R14 and R15, the base terminal is connected to the collector terminal of the first PNP transistor Q1 of the transmission / reception selector 53, and the emitter terminal is connected to ground. Quad-band multiplexed voltage controlled oscillator comprising an oscillator (54b) including a connected switching transistor (Q12). The high frequency oscillator 55 of claim 2, wherein A third varactor diode VD21 connected to the tuning voltage VT through filters L21 and C21 and varying capacitance according to the tuning voltage VT, and a second of the transmission / reception selection unit 53; A fourth varactor diode VD22 connected to the collector terminal of the PNP transistor Q2 to vary the capacitance according to the reception operating voltage VRX through the collector terminal, and a plurality of resonant elements L22, L23, C22, A resonator 55a including C23; A base terminal is connected to the output terminal of the high frequency oscillation selector 52 through a resistor R23, and a capacitor C25 and two resistors R24 and R25 are connected in series from the base terminal to ground, and the collector thereof. A stage is connected to an input terminal of the high frequency buffer section 57, and the oscillation transistor Q23 having its emitter terminal connected to ground through a capacitor C26 is connected between the base terminal of the oscillation transistor Q23 and ground. The collector terminal is connected to two resistors (R24, R25) connecting point connected to the terminal, and the base terminal thereof is connected to the collector terminal of the first PNP transistor Q1 of the transmission / reception selector 53, and the emitter terminal is grounded. Quad-band multiplexed voltage controlled oscillator comprising an oscillator (55b) comprising a switching transistor (Q22) connected to the. The low frequency buffer unit 56 of claim 2, The two resistors R16 and R17 are connected in series from the collector terminal of the second PNP transistor Q2 of the transmission / reception selector 53 to ground, and the base terminal is connected to the connection point of the two resistors R16 and R17. A transistor (Q14) connected to the collector terminal through a filter (L14, C18) and an emitter terminal connected to an output terminal of the low frequency oscillation unit (54), wherein the transistor ( A receiving buffer circuit 56RX which connects the collector terminal of Q14) to the output terminal via the first coupling capacitor CC1; Connect two resistors in series from the collector terminal of the first PNP transistor Q1 of the transmission / reception selector 53 to ground, connect the base terminal to the connection point of the two resistors, and operate the filter through the collector terminal. A transmission buffer connected to a voltage (B +) terminal, the emitter terminal of which is connected to an output terminal of the low oscillation unit 54, and a collector buffer of the transistor connected to a second coupling capacitor CC2 to an output terminal. Quad band combined voltage controlled oscillator, characterized in that it comprises a circuit (56TX). 3. The high frequency buffer unit 57 according to claim 2, The two resistors R26 and R27 are connected in series from the collector terminal of the second PNP transistor Q2 of the transmission / reception selector 53 to ground, and the base terminal is connected to the connection point of the two resistors R26 and R27. And a transistor (Q24) connected to the collector terminal through the filters (L24, C28) and the emitter terminal connected to the output terminal of the high frequency oscillation unit (55). A receiving buffer circuit 57RX in which a collector end of Q24) is connected to an output end of a third coupling capacitor CC3; Connect two resistors in series from the collector terminal of the first PNP transistor Q1 of the transmission / reception selector 53 to ground, connect the base terminal to the connection point of the two resistors, and operate the filter through the collector terminal. A transmission buffer connected to the voltage (B +) terminal, the emitter terminal of which is connected to the output terminal of the high frequency oscillation unit 55, and a collector buffer of the transistor connected to a fourth coupling capacitor CC4 to the output terminal. Quad band combined voltage controlled oscillator, characterized in that it comprises a circuit (57TX).