CN101888218A - Analog reflective I-Q vector modulation circuit based on GaAs HBT device - Google Patents

Abstract

The invention discloses an analog reflection type IQ vector modulation circuit based on a GaAs HBT device, which mainly solves the problems that the existing modulation circuit occupies a large chip area ratio and high cost. It includes: a 3-dB lange coupler (1), two analog reflection attenuators (6, 7), and a 3-dB Wilkinson power combiner (10), the 3-dB lange coupler through The port output is directly output to an input end of the power combiner (7) after phase-shifting through the first attenuator (6); the coupled port output of the 3-dB lange coupler is directly phase-shifted through the second attenuator (6) Output to the other input terminal of the power combiner (10), wherein the gallium arsenide heterojunction bipolar transistor of each analog reflective attenuator, its collector is respectively connected in parallel with resistors R3 and R4, in order to reduce Vb = 0 when the reflection coefficient |Γ|, the emitters are respectively connected in series with inductors L1 and L2 to offset the parasitic effect due to the HBT device. The invention can be used to generate IQ modulated signals or perform frequency conversion.

Description

Analog reflective I-Q vector modulation circuit based on GaAs HBT device

technical field

The invention belongs to the technical field of integrated circuits, in particular to a reflection type I-Q vector modulation circuit, which is used in digital communication to generate I-Q modulation signals or perform frequency conversion.

Background technique

Traditionally, there are two main implementation structures for vector modulators in microwave and millimeter wave applications. The first is composed of two quadrature bi-phase modulators through a 3-dB power combiner; the second is composed of a variable attenuator and a 360° variable phase shifter. Although in the second structure, the insertion loss is very small, it requires the attenuator to have a fixed phase and the phase shifter to have a fixed insertion loss, which makes the circuit design very difficult. Therefore, in microwave and millimeter wave applications, the first structure consisting of two-phase variable analog reflective attenuators is often widely used.

The application of the two-phase variable analog reflective attenuator to the vector modulator was first proposed by Devlin and Minnis. The reflective attenuator is composed of a Lange coupler as an orthogonal hybrid network and two cold-mode devices. The cold-mode devices use high electron mobility transistors HEMT or heterojunction bipolar transistors HBT. The use of cold-mode HEMT devices requires a negative bias voltage to realize the modulation function, while the use of cold-mode HBT only requires a positive bias voltage. Cold-mode HBT devices have relatively large parasitic parameters, and the amplitude and phase errors caused by parasitic effects can be eliminated through a balanced or push-pull circuit structure. This structure can realize a better symmetrical constellation diagram, but occupies a relatively large chip area and costs relatively high.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned vector modulator, and provide an analog reflective I-Q vector modulation circuit based on GaAsHBT devices, so as to reduce the occupied area and power consumption of the chip, and improve the performance of the chip.

Technical scheme of the present invention is realized like this:

1. Technical principle

The insertion loss of the analog reflective I-Q vector modulation circuit based on GaAs HBT devices is mainly determined by the reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT of the attenuator, and the reflection coefficient Γ is required to be in two states of Vb=0 and Vb=Von The amplitudes are equal and the phase difference is 180°. When Vb=0, the impedance of the variable resistance terminal GaAs HBT is much greater than 50Ω, so the reflection coefficient is very large when the signal is transmitted to the variable resistance terminal GaAs HBT; when Vb=Von, due to the parasitic resistance in the GaAs HBT device, The impedance reduction of the variable resistor terminal GaAs HBT is not ideal, so that the reflection coefficient when the signal is transmitted to the variable resistor terminal GaAs HBT is smaller than that when Vb=0. The reflection coefficient |Γ| when Vb=0 can be appropriately reduced by connecting a considerable resistance in parallel with the collector of GaAs HBT, so that the reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT of the reflective attenuator is between Vb=0 and The magnitudes of Vb=Von in both states are equal. Due to the parasitic effect caused by the parasitic capacitance between the base, collector and emitter of the GaAs HBT device, the phase difference of the reflection coefficient Γ is far away from 180° in the two states of Vb=0 and Vb=Von. An inductor is connected in series with the emitter of the HBT to offset this parasitic effect, so that the reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT of the reflective attenuator has a phase difference of 180° in the two states of Vb=0 and Vb=Von

2. Modulation circuit structure

The modulation circuit of the present invention includes: a 3-dB lange coupler, two analog reflection attenuators, and a 3-dB wilkinson power combiner, the output of the through port of the 3-dB lange coupler directly passes through the first An attenuator is phase-shifted and then output to an input of the power combiner; the coupled port of the 3-dB lange coupler is directly output to the other input of the power combiner after being phase-shifted by the second attenuator. The two input signals are synthesized and output from the output terminal.

The analog reflective attenuator includes a 3-dB lange coupler, two gallium arsenide heterojunction bipolar transistors Q1 and Q2, and two resistors R3 and R4, the input of the 3-dB lange coupler The port is used as the input port of the attenuator, and the isolated port is used as the output port of the attenuator; the through port and coupled port of the 3-dB lange coupler are respectively connected to the collectors of Q1 and Q2; the bases of Q1 and Q2 are respectively connected to R3, R4 is connected, and the other ends of resistors R3 and R4 are connected together as the control port Vb of the attenuator; the collectors of Q1 and Q2 are respectively connected in parallel with resistors R1 and R2 to reduce the reflection coefficient |Γ when Vb=0 |; The emitters of Q1 and Q2 are respectively connected in series with inductors L1 and L2 to offset the parasitic effect caused by the parasitic capacitance between the base, collector and emitter of the HBT device.

The present invention has the following advantages:

(1) The modulation circuit of the present invention only adopts two analog reflective attenuators, directly connected to the through port and the coupled port of the 3-dBlange coupler, and directly synthesized by the 3-dB Wilkinson power combiner, compared to the previous The modulation circuit with a balanced or push-pull circuit structure uses four analog reflective attenuators and four additional couplers to realize the function, which saves a lot of chip area without affecting the circuit function, thereby saving the production cost.

(2) In the present invention, a resistor R1 and R2 with equal resistance are connected in parallel to the collector electrodes of GaAs HBT devices Q1 and Q2 respectively, so that the reflection coefficient |Γ| when Vb=0 is reduced, thereby making the reflective attenuator The reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT has the same amplitude in the two states of Vb=0 and Vb=Von, which reduces the insertion loss of the overall circuit.

(3) In the present invention, an inductance L1 and L2 having equal inductance values are respectively connected in series at the emitters of the GaAs HBT devices Q1 and Q2, thereby offsetting the parasitic between the base, the collector and the emitters of the GaAs HBT devices. The parasitic effect caused by the capacitance makes the reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT of the reflective attenuator have a phase difference of 180° in the two states of Vb=0 and Vb=Von, which reduces the overall circuit The insertion loss is improved while improving the accuracy of phase modulation.

Description of drawings

Figure 1 is a circuit diagram of the existing analog reflective I-Q vector modulation based on GaAs HBT devices;

Fig. 2 is a circuit diagram of an existing analog reflective attenuator;

Fig. 3 is the analog reflection type I-Q vector modulation circuit diagram based on GaAs HBT device of the present invention;

Fig. 4 is the analog reflection type attenuator circuit diagram among the present invention;

Fig. 5 shows the ratio of the amplitude of the reflection coefficient and the phase difference of the analog reflection attenuator of the present invention in the two states of Vb=0 and Vb=Von.

Detailed ways

的控制信号高低电平相反，作为调制电路的两个控制端；该第三3-dB lange耦合器3的耦合端口和直通端口分别连接第三模拟反射型衰减器8和第四模拟反射型衰减器9的输入；该第三模拟反射型衰减器8和第四模拟反射型衰减器9的输出分别连接第五3-dB lange耦合器5的耦合端口和直通端口；第一模拟反射型衰减器8控制端口VQ和第二模拟反射型衰减器9控制端口

的控制信号高低电平相反，作为调制电路的另外两个控制端；该3-dB lange耦合器1，2，3，4，5的隔离端口与地之间各连接一个50Ω的电阻；该第四3-dB lange耦合器4的输入端口连接3-dB wilkinson功率合成器10的一个输入端口；该第五3-dB lange耦合器5的输入端口连接3-dB wilkinson功率合成器10的另一个输入端口；该3-dB wilkinson功率合成器10的输出端口作为调制电路的输出。Referring to Figure 1, the existing analog reflective IQ vector modulation circuit diagram based on GaAs HBT devices, including five 3-dB lange couplers 1, 2, 3, 4, 5, and four analog reflective attenuators 6, 7, 8 , 9, and a 3-dB wilkinson power combiner 10, the 3-dB lange coupler has four ports, respectively input port, isolation port, through port and coupling port, the signal is input from the input port, from the through port and The coupled ports output signals that are 0° and 90° out of phase with the input signal, respectively. The input port of the first 3-dB lange coupler 1 is used as the input of the modulation circuit, and the through port and the coupled port are respectively connected to the second 3-dB lange coupler 2 and the input port of the third 3-dB lange coupler 3; The coupled port and the through port of the second 3-dB lange coupler 2 are respectively connected to the input of the first analog reflection attenuator 6 and the second analog reflection attenuator 7; the first analog reflection attenuator 6 and the second The output of the analog reflective attenuator 7 is respectively connected to the coupling port and the through port of the fourth 3-dB lange coupler 4; the first analog reflective attenuator 6 control port VI and the second analog reflective attenuator 7 control port

The high and low levels of the control signal are opposite, as the two control terminals of the modulation circuit; the coupling port and the through port of the third 3-dB lange coupler 3 are respectively connected to the third analog reflection type attenuator 8 and the fourth analog reflection type attenuator The input of device 9; The output of the third analog reflective attenuator 8 and the fourth analog reflective attenuator 9 are respectively connected to the coupling port and the through port of the fifth 3-dB lange coupler 5; the first analog reflective attenuator 8 control ports VQ and 9 control ports for the second analog reflective attenuator

The high and low levels of the control signal are opposite, as the other two control terminals of the modulation circuit; the isolation ports of the 3-dB lange coupler 1, 2, 3, 4, and 5 are each connected to a 50Ω resistor with the ground; the first The input port of four 3-dB lange couplers 4 is connected to an input port of 3-dB wilkinson power combiner 10; Input port; the output port of the 3-dB Wilkinson power combiner 10 is used as the output of the modulation circuit.

Referring to Figure 2, the circuit diagram of an existing analog reflective attenuator includes a 3-dB lange coupler, two gallium arsenide heterojunction bipolar transistors Q1 and Q2, and two resistors R1 and R2, the 3-dB lange The input port of the coupler is used as the input port of the attenuator, and the isolation port is used as the output port of the attenuator; the through port of the 3-dB lange coupler outputs a signal with a phase difference of 0° from the input signal and is connected to the collector of Q1, and the coupled port The output signal with a phase difference of 90° from the input signal is connected to the collector of Q2; the bases of Q1 and Q2 are connected to R1 and R2 respectively, and the other ends of resistors R1 and R2 are connected together as the control port Vb of the attenuator.

Referring to Fig. 3, the analog reflective I-Q vector modulation circuit of the present invention based on GaAs HBT device mainly consists of a 3-dB lange coupler 1, a 3-dB wilkinson power combiner 10, and two analog reflective attenuators 6 Composed with 7. The through port of the 3-dB lange coupler outputs a signal with a phase difference of 0° from the input signal, and directly passes through the phase shift of the first attenuator 6 and outputs it to an input end of the power combiner 10; the 3-dB lange coupler The coupled port outputs a signal with a phase difference of 90° from the input signal, and directly passes through the second attenuator 7 to shift the phase and then output to the other input end of the power combiner 10, and the power combiner 10 synthesizes the two input signals and outputs ; The first analog reflective attenuator 6 control port VI and the second analog reflective attenuator 7 control port VQ as the two control terminals of the modulation circuit.

Referring to Fig. 4, the analog reflection type attenuator among the present invention comprises a 3-dB lange coupler, two gallium arsenide heterojunction bipolar transistors Q1 and Q2, four resistors R1, R2, R3 and R4, and The two inductors L1 and L2, wherein, the resistance values of the resistors R3 and R4 are equal, and are 140±1Ω; the inductance values of the inductors L1 and L2 are equal, and are 43±1pH. The input port of the 3-dB lange coupler is used as the input port of the attenuator, and the isolation port is used as the output port of the attenuator; the through port and the coupled port of the 3-dB lange coupler are connected to the collectors of Q1 and Q2 respectively; Q1 The collectors of Q1 and Q2 are respectively connected in parallel with resistors R3 and R4 to reduce the reflection coefficient |Γ| when Vb=0; the bases of Q1 and Q2 are connected with R1 and R2 respectively, and the other ends of resistors R1 and R2 are connected Together as the control port Vb of the attenuator; the emitters of Q1 and Q2 are connected in series with the inductors L1 and L2 respectively to offset the parasitic caused by the parasitic capacitance between the base, collector and emitter of the HBT device effect. The phase difference between the signal output by the output port when the control port Vb is equal to low level 0 and the signal output by the output port when Vb is equal to high level Von is 180°.

The ratio and the phase difference simulation results of the reflection coefficient magnitude and the phase difference of the simulated reflective attenuator of the present invention in Vb=0 and Vb=Von two states, as shown in Figure 5, wherein Figure 5 (a) is the simulated reflective attenuator The ratio of the amplitude of the reflection coefficient in the two states of Vb=0 and Vb=Von, Figure 5(b) shows the phase difference of the reflection coefficient of the simulated reflective attenuator in the two states of Vb=0 and Vb=Von. As can be seen from Fig. 5, the analog reflection type attenuator of the present invention, when the signal frequency is 30GHz, the ratio of the reflection coefficient Γ of the collector electrode of the variable resistance terminal GaAs HBT in the two states of Vb=0 and Vb=Von is 1, and the phase difference is 180°. It shows that the reflection coefficient Γ of the collector of the variable resistance terminal GaAs HBT of the simulated reflective attenuator of the present invention has reached the requirement of the simulated reflective I-Q vector modulation circuit, and the insertion loss has been reduced while realizing the function.

Claims (4)

1. a kind of analog reflection type I-Q vector modulation circuit based on GaAs HBT device, it is characterized in that comprising: a 3-dB lange coupler (1), two simulation reflection type attenuators (6,7), and 1 3 -dB wilkinson power combiner (10), the straight-through port output of this 3-dB lange coupler is output to an input end of power combiner (7) after the first attenuator (6) phase-shifting directly; The 3-dB The output of the coupled port of the lange coupler is directly shifted through the second attenuator (6) and then output to the other input end of the power combiner (10), and the power combiner (10) combines the two input signals and then outputs it. 2. The analog reflective I-Q vector modulation circuit according to claim 1, characterized in that the analog reflective attenuator includes a 3-dB lange coupler, two gallium arsenide heterojunction bipolar transistors Q1 and Q2 , four resistors R1, R2, R3 and R4, and two inductors L1 and L2, the input port of the 3-dB lange coupler is used as the input port of the attenuator, and the isolated port is used as the output port of the attenuator; the 3-dB The through port and coupled port of the lange coupler are respectively connected to the collectors of Q1 and Q2; the collectors of Q1 and Q2 are respectively connected in parallel with resistors R3 and R4 to reduce the reflection coefficient |Γ| when Vb=0; Q1 The bases of Q1 and Q2 are connected to R1 and R2 respectively, and the other ends of resistors R1 and R2 are connected together as the control port Vb of the attenuator; the emitters of Q1 and Q2 are connected in series with inductors L1 and L2 respectively to offset the HBT The parasitic effect caused by the parasitic capacitance between the base, collector and emitter of the device. 3. The analog reflective attenuator based on GaAs HBT device according to claim 2, characterized in that the resistance values of resistors R3 and R4 are equal and are 140 ± 1Ω. 4. the analog reflective attenuator based on GaAs HBT device according to claim 2, is characterized in that the inductance value of inductance L1 and L2 is equal, and is 43 ± 1pH.

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