CN107070429B

CN107070429B - Electrically adjustable negative group delay circuit with stable insertion loss

Info

Publication number: CN107070429B
Application number: CN201710235458.9A
Authority: CN
Inventors: 吴林晟; 邱良丰; 毛军发
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2017-04-12
Filing date: 2017-04-12
Publication date: 2020-06-09
Anticipated expiration: 2037-04-12
Also published as: CN107070429A

Abstract

An electrically adjustable negative group delay circuit with stable insertion loss is simple in structure and easy to process, can be realized by a planar microstrip circuit, and solves the problem that the performance of the whole microwave system is deteriorated due to positive group delay introduced by various microwave devices. The negative group delay amount which can be realized by the negative group delay circuit can be set by adjusting the bias voltage, and compared with a non-real-time adjustable negative group delay circuit, the negative group delay circuit has higher flexibility and can be used for realizing the functions of automatic delay compensation, electrically adjustable beam scanning of an antenna array directional diagram and the like in a circuit with negative feedback. Meanwhile, in the process of adjusting the negative time delay, the insertion loss variation is very small, so that the invention can be widely applied to various microwave circuit systems which need adjustable negative group time delay and have higher requirements on the insertion loss stability.

Description

Electrically adjustable negative group delay circuit with stable insertion loss

Technical Field

The invention relates to a technology in the field of signal processing devices, in particular to an electrically adjustable negative group delay circuit with stable insertion loss.

Background

By properly introducing signal attenuation, the negative group delay characteristic of the circuit can be observed within a particular frequency band without violating causality. Negative group delay has been implemented in microwave circuits and applied to various microwave systems, such as feed networks for feed forward amplifiers and antenna arrays. The negative group delay circuit is inserted into the systems to compensate the unexpected delay imbalance among different paths, so that the problem of the performance deterioration of the whole microwave system caused by the positive group delay introduced by various microwave devices is solved, and the working efficiency, the bandwidth and other performances of the system can be improved. The electric tunability can further increase the functional freedom degree of the negative group delay circuit and expand the application range of the negative group delay circuit in communication and radar systems, so that the negative group delay circuit with adjustable power generation has obvious engineering application value.

Disclosure of Invention

The invention provides an electrically adjustable negative group delay circuit with stable insertion loss, aiming at the defects of larger insertion loss, larger range of insertion loss variation and the like in the electrical tuning process of the prior art, and the problems that the delay quantity is very sensitive to bias voltage and is not easy to accurately control and the like.

The invention is realized by the following technical scheme:

the invention comprises the following steps: input port, input matching network, impedance transformer, electrically tunable resonator, output matching network and output port, wherein: the input port is connected with the first port of the input matching network, the second port of the input matching network is connected with the first port of the impedance converter and the first port of the output matching network, the second port of the impedance converter is connected with the electrically tunable resonator, and the second port of the output matching network is connected with the output port.

The electrically tunable resonator includes: one section transmission line, lumped resistance and set up in two varactor of transmission line both sides, wherein: the varactors are connected to the lumped resistors through transmission line resonators, respectively.

And the two variable capacitance diodes are respectively provided with a lumped capacitor and a series resistor for generating voltage bias.

The invention relates to a beam scanning antenna array system, comprising: the input end, the electrically adjustable negative group delay circuit, the power amplifier and the antenna subarray are connected in sequence through the transmission line.

The electrically adjustable negative group delay circuit, the power amplifier and the antenna subarray form an antenna branch, and when a plurality of branches are connected in parallel, a power divider is preferably further arranged between the trunk and the branch.

Technical effects

Compared with the prior art, the group delay is negative and electrically adjustable, the center frequency is 1GHz, and the group delay adjustment range is from-1.9 to-0.2 ns; the invention has smaller insertion loss, and can reach 2.5 to 3.4dB after being optimized; the invention has small variation of insertion loss when adjusting the negative group delay, and the fluctuation after optimization can be less than 0.9 dB.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a block diagram of an embodiment;

in fig. 2: the input matching circuit comprises an input port 1, an input matching transmission line 2, a quarter-wavelength impedance converter 3, a transmission line resonator 4, a lumped capacitor 5, a variable capacitance diode 6, a series resistor 7, a series resistor 8, a variable capacitance diode 9, a lumped capacitor 10, a lumped resistor 11, an output matching transmission line 12 and an output port 13;

fig. 3a is the group delay response under different capacitance values, fig. 3b is the insertion loss corresponding to different negative group delay working states, and fig. 3c is the frequency response corresponding to two group delay working states of-0.2 ns and-1.9 ns;

fig. 4 is a schematic diagram of an embodiment applied to an antenna array system for realizing electrically tunable beam scanning;

in fig. 4: the antenna comprises an input end 2-8, first to seventh transmission lines 2-1 to 2-7, first to third power dividers 2-21, 2-22 and 2-23, electrically adjustable negative group delay circuits 2-9 to 2-12, first to fourth power amplifiers 2-13 to 2-16 and first to fourth antenna sub-arrays 2-17 to 2-20;

figure 5 is a schematic diagram of the antenna array system pattern beam scanning of figure 4.

Detailed Description

As shown in fig. 2, the present embodiment includes: an input port 1, a transmission line 2 as an input matching network, an impedance transformer 3, an electrically tunable resonator, a transmission line 12 as an output matching network, and an output port 13. The substrate used in this example was TaconicRF-35A2, which had a thickness of 40mil, a relative dielectric constant of 3.5, and a loss tangent of 0.0013.

The input port 1 and the output port 13 are microstrip lines with characteristic impedance of 50 Ω, and the line width is 2.29 mm.

The

transmission lines

2 and 12 as the input and output matching networks are microstrip lines with characteristic impedance of 76 Ω, the line width is 1.04mm, and the line length is 47.3mm, which is about 1/4 wavelength at the central frequency of 1 GHz.

The impedance converter 3 is a microstrip line with characteristic impedance of 77 Ω, the line width is 1.02mm, and the line length is 48.9mm, which is about 1/4 wavelengths at the center frequency of 1 GHz.

The electrically tunable resonator includes: a microstrip line 4 with a characteristic impedance of 100 Ω, a lumped resistor 11 with a resistance of 62 Ω and two varactors 6 and 9 of the type BB857-02V from Infineon, wherein: the length of the microstrip line 4 is 66.7mm, and the line width is 0.56 mm; the lumped resistor 11 is loaded at the junction of the microstrip line 4 and the impedance transformer 3 and is grounded; the varactors 6 and 9 are disposed at both ends of the microstrip line 4.

The variable capacitance diode 6(9) is connected with a lumped capacitor 5(10) with the capacitance value of 0.95pF in series and is grounded, so that the value range of the variable capacitance is adjusted; and is connected to the direct current power supply through a series resistor 7(8) with the resistance value of 22k omega so as to apply voltage bias to the variable capacitance diode 6(9), and the resistor 7(8) is used for isolating potential interference of an alternating current signal to the direct current power supply and limiting the magnitude of bias current.

The area of this embodiment is 22X 53mm 2.

The embodiment works at 1GHz, the regulating voltage is between 1 and 25V, the negative group delay amount between-0.2 and-1.9 ns can be provided, the corresponding insertion loss is changed from 3.4 to 2.5dB, and the fluctuation range is less than 0.9 dB. The test group delay frequency response of the insertion loss under various voltage bias combinations is shown in fig. 3a, the insertion loss under various negative group delay working states is shown in fig. 3b, and the frequency response corresponding to two group delay working states of-0.2 ns and-1.9 ns is shown in fig. 3 c.

Compared with the adjustable negative group delay circuit in other documents, the present embodiment has the minimum insertion loss fluctuation of 0.9 dB. For example, the insertion loss ripple of the circuit in the publication "Negativegroupdelaysynthesiser" is about 8 dB; the insertion loss fluctuation of the circuit in the document Design of reliable negative group delay circuits for communication systems is about 20 dB; the insertion loss fluctuation of the circuit in the document "reactive group delay circuit with independent tunable center frequency and group delay" is about 20 dB; in addition, the negative group time delay adjustable circuit is relatively simple in structure, easy to process and low in implementation cost.

The working principle of the device is briefly described as follows: the capacitance values of the two variable capacitance diodes are adjusted by simultaneously changing the two bias voltages, so that the admittance slope parameters and the no-load quality factors of the resonator are changed under the condition of ensuring that the resonance frequency of the resonator is unchanged, and finally the negative group delay provided by the circuit is changed. When the variable capacitance diode is adjusted, the input impedance viewed from the impedance converter 3 to the resonator is basically kept unchanged at the resonance frequency, so that the insertion loss variation at the center frequency of the whole circuit is small. Therefore, the invention can provide the electrically tunable negative group delay amount while having stable insertion loss.

As shown in fig. 4, the present embodiment is applied to electrically tunable beam scanning of a parallel feed antenna array, and the beam scanning antenna array system includes: an input end 2-8, first to seventh transmission lines 2-1 to 2-7, first to third power dividers 2-21, 2-22 and 2-23, the electrically adjustable negative group delay circuits 2-9 to 2-12, first to fourth power amplifiers 2-13 to 2-16, and first to fourth antenna sub-arrays 2-17 to 2-20. Each negative group delay adjustable circuit embodiment provides a specific negative group delay amount by giving different bias voltages; and then compensating the insertion loss introduced by the feed network and the embodiment through the amplifier, and controlling the time delay and the phase of the antenna subarray, thereby realizing the beam electric scanning of the antenna array, and the generated directional diagram is shown in a schematic diagram 5. Since the present embodiment can provide a true delay of-0.2 to-1.9 ns, which is equivalent to a phase advance of 72 ° to 684 ° at a center frequency of 1GHz, the requirements of various beam scanning angles can be completely satisfied. Moreover, since the insertion loss variation of the present embodiment is small in each state, the amplifiers in each sub-array can be set to have the same fixed gain, which facilitates low-cost implementation.

The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An electrically tunable negative group delay circuit with stable insertion loss, comprising: an input port, an input matching network, an impedance transformer, an electrically adjustable resonator, an output matching network, and an output port, wherein: the input port is connected with the first port of the input matching network, the second port of the input matching network is connected with the first port of the impedance transformer and the first end □ of the output matching network, the second port of the impedance transformer is connected with the electrically tunable resonator, and the second port of the output matching network is connected with the output port;

the electrically tunable resonator includes: one section microstrip line, one lumped resistance and set up in two varactor of microstrip line both sides, wherein: the lumped resistor is loaded at the intersection of the microstrip line and the impedance transformer and is grounded, each variable capacitance diode in the two variable capacitance diodes is respectively connected with a lumped capacitor in series, and each variable capacitance diode is respectively connected to a direct current power supply through a series resistor to apply bias voltage to the variable capacitance diode;

the impedance converter and the input-output matching network are quarter-wavelength transmission lines with the central frequency of 1 GHz;

the electrically adjustable negative group delay circuit adjusts the capacitance values of the two variable capacitance diodes by simultaneously changing two bias voltages applied to the two variable capacitance diodes, so that the admittance slope parameters and the no-load quality factors of the resonator are changed under the condition of ensuring that the resonance frequency of the resonator is unchanged, and the adjustment of the negative group delay is realized.

2. A beam scanning antenna array system, comprising: the electrically tunable negative group delay circuit of claim 1, the power amplifier, and the antenna subarray connected in series by a transmission line, wherein: each electrically adjustable negative group delay circuit provides specific negative group delay amount by giving different bias voltages, and the delay and the phase of the antenna subarray are controlled by compensating the feed network and the insertion loss through the amplifier, so that beam electric scanning of the antenna array is realized.

3. The beam scanning antenna array system of claim 2, wherein the electrically tunable negative group delay circuit, the power amplifier and the antenna sub-array form an antenna branch, and when a plurality of branches are connected in parallel, a power divider is further provided at the head end of the branch.