CN101872883A - Frequency Doubler Based on Left and Right Handed Composite Nonlinear Transmission Lines - Google Patents

Abstract

The invention discloses a frequency multiplier. The frequency multiplier is composed of at least one left-hand composite nonlinear transmission line unit. The left-hand composite nonlinear transmission line unit is formed by connecting a single-section left-hand nonlinear transmission line and a single-section right-hand nonlinear transmission line in series. By using the invention, the advantages of the left-hand nonlinear transmission line and the right-hand nonlinear transmission line can be combined, and the working frequency and frequency multiplication efficiency of the frequency multiplier can be improved.

Description

Frequency Doubler Based on Left and Right Handed Composite Nonlinear Transmission Lines

technical field

The invention relates to the technical field of frequency multipliers, in particular to a frequency multiplier based on left and right hand composite nonlinear transmission lines.

Background technique

Microwave frequency multipliers are widely used in systems such as communication, radar and measuring instruments. Its main functions can be summarized in the following aspects: 1. Multiply the oscillator with low frequency but stable output frequency to obtain a high-frequency oscillation source with high stability; 2. The highest oscillation frequency of the transistor oscillator cannot reach When required by the system, the ultra-high frequency oscillation source is obtained through the frequency multiplier; 3. Multiple integer multiple frequencies are obtained.

The nonlinear transmission line is a widely used frequency multiplier structure, which has the advantages of simple structure, no additional matching circuit and idle circuit. A typical nonlinear transmission line includes several sections of microstrip transmission lines connected in series at a certain interval, and reverse biased parallel Schottky diodes are placed between each section of microstrip line. The Schottky diode is used as a variable capacitor, and its capacitance changes with the bias voltage, and the nonlinear capacitive reactance causes harmonics to realize the frequency multiplication function.

The simplified circuit model of the above-mentioned traditional nonlinear transmission line is a periodic load of series inductance and parallel capacitance. This structure is called a right-handed transmission line, that is, the electric field strength E, magnetic field strength H and wave vector k satisfy the right-hand spiral rule. There are some inherent defects in the traditional right-hand nonlinear transmission line: the equivalent circuit of the right-hand transmission line is a low-pass circuit, so the highest frequency of the output harmonic is less than the cut-off frequency of the transmission line, which is limited in high-frequency applications; the low-pass circuit itself cannot suppress the input fundamental wave signal, and the amplitude of the fundamental wave signal is often much larger than the harmonic signal. In order to obtain the ideal harmonic wave, high requirements are placed on the filter in the system.

Contents of the invention

(1) Technical problems to be solved

In order to solve the above problems, the present invention provides a frequency multiplier based on left and right hand composite nonlinear transmission lines.

(2) Technical solutions

In order to achieve the above object, the present invention provides a frequency multiplier, which is composed of at least one left-hand composite nonlinear transmission line unit, and the left-hand composite nonlinear transmission line unit is composed of a single-section left-hand nonlinear transmission line and a single-section right-hand nonlinear transmission line The transmission lines are connected in series.

In the above solution, the single-section left-hand nonlinear transmission line includes: a first fixed capacitor and a second fixed capacitor connected in series; a first variable capacitor connected in series between the first fixed capacitor and the second fixed capacitor; a first inductor between the first fixed capacitor and the first variable capacitor; and a second inductor connected in parallel between the first variable capacitor and the second fixed capacitor.

In the above solution, the single-section right-hand nonlinear transmission line includes: a third inductor and a fourth inductor connected in series; and a second variable capacitor connected in parallel between the third inductor and the fourth inductor.

In the above solution, the first variable capacitor or the second variable capacitor is composed of a self-biased PIN diode.

In the above scheme, the first variable capacitor or the second variable capacitor is related to the amplitude of the input signal. When the amplitude of the input signal is greater than the turn-on voltage of the PIN diode as the variable capacitor, the capacitance of the variable capacitor is determined by a A small fixed value translates into a DC path, i.e. a large capacitance value, and the resulting harmonics at frequencies that are integer multiples of the input signal.

In the above solution, the left and right handed composite nonlinear transmission line unit has a band-pass characteristic and is used for transmitting microwave signals of a specific frequency.

In the above scheme, the input end of the left-handed composite nonlinear transmission line unit is a right-handed nonlinear transmission line, and the output end is a left-handed nonlinear transmission line.

In the above solution, by selecting the capacitance value of the variable capacitor and the inductance value of the inductor, the characteristic impedance of the transmission line matched with the input port/output port can be obtained without an independent matching circuit.

In the above solution, when the frequency multiplier is composed of multiple left-handed composite nonlinear transmission line units, the multiple left-handed composite nonlinear transmission line units are connected in series.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

1. By using the present invention, the frequency multiplication efficiency of the frequency multiplier at a higher frequency can be effectively improved. The frequency multiplier based on the left-handed composite nonlinear transmission line provided by the present invention absorbs the advantage that the left-handed nonlinear transmission line can work at a higher frequency; combined with the suppression of high-frequency harmonics by the right-handed nonlinear transmission line unit at the output end. Therefore, the frequency multiplication efficiency of the nonlinear transmission line frequency multiplier at higher frequencies is further improved.

2. By using the present invention, the fundamental wave power in the output signal can be effectively suppressed. Since the frequency multiplier based on the left-handed composite nonlinear transmission line provided by the present invention has a band-pass characteristic, the fundamental wave signal with a lower frequency can be suppressed by rationally selecting device parameters.

3. With the present invention, redundant harmonic signals can be suppressed. Since the frequency multiplier based on the left-handed composite nonlinear transmission line provided by the present invention has a band-pass characteristic, unnecessary high-order harmonic signals can be suppressed through reasonable selection of device parameters.

4. With the present invention, the external bias circuit can be omitted. Since the diode in the present invention adopts a self-bias structure, no bias circuit is needed, the structure of the frequency multiplier is simplified, and the volume is reduced.

5. With the present invention, the additional matching circuit can be omitted, and the microwave characteristics of the frequency doubler can be improved.

Description of drawings

Figure 1 is a schematic diagram of the volt-ampere characteristics of a PIN diode;

Fig. 2 is a structural schematic diagram of a left-hand nonlinear transmission line unit;

Fig. 3 is a structural schematic diagram of a right-hand nonlinear transmission line unit;

Fig. 4 is a structural schematic diagram of a left and right hand composite nonlinear transmission line unit;

Fig. 5 is the result of circuit small-signal S-parameter analysis of the left and right hand composite nonlinear transmission line unit;

Fig. 6 is a simulation diagram of the frequency multiplication effect of the left and right hand composite nonlinear transmission line.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The characteristics of the PIN diode are shown in Figure 1. When the diode is in the cut-off state, its junction capacitance is a fixed value. When the input signal amplitude is greater than the diode’s turn-on voltage, the diode turns from cut-off to conduction, and its capacitance value changes suddenly. The above-mentioned nonlinear process is the basic principle of PIN diodes to generate harmonics. Therefore, PIN diodes are also commonly used devices in frequency doubling circuits.

In recent years, methods for constructing left-handed materials by transmission lines periodically loaded with series capacitance and parallel inductance have been proposed. Different from the right-handed transmission line, E, H and k in the left-handed transmission line satisfy the left-handed spiral rule. Both permittivity and permeability are negative in left-handed materials.

Specific to the circuit structure, the left-hand nonlinear transmission line shown in Figure 2 (which contains a PIN diode, two DC blocking capacitors and two inductors) and the right-hand nonlinear transmission line shown in Figure 3 (which contains a PIN diode and two Inductance), the equivalent circuit capacitor and inductor position reciprocity. The present invention absorbs the advantages of the left-hand nonlinear transmission line and the right-hand nonlinear transmission line through the compounding of the two, and obtains more ideal frequency doubling characteristics.

The left-handed composite nonlinear transmission line shown in Fig. 4 is composed of a left-handed nonlinear transmission line unit and a right-handed nonlinear transmission line unit in series. In this example, Cj represents the junction capacitance of the PIN diode in the cut-off state. For the diode we choose, Cj is 0.5pF, and the diode turn-on voltage is 1.1V. The inductance L is 1.8nH. The input and output ports of the circuit are all 50Ω standard RF ports. For the left-handed composite non-linear transmission line shown in Figure 4, the two ends of the PIN diode are either directly grounded through an inductance or directly grounded, which constitute a self-biased structure.

Through the analysis of the small signal S parameters of the circuit, it can be seen that the left and right hand composite transmission line is a bandpass circuit, as shown in Figure 5.

Figure 6 is the simulation result of frequency multiplication characteristics of the left-handed and left-handed composite nonlinear transmission line in the example. The input fundamental wave signal frequency is 2.5GHz and the power is 20dBm. It can be seen that in the output signal, the fundamental wave signal is well suppressed, down to 11.3dBm; the second harmonic power is 9.2dBm, and the conversion efficiency is relatively high.

The above example consists of only one left and right handed composite nonlinear transmission line element. During the implementation of the present invention, multiple left and right hand composite nonlinear transmission line units can be connected in series to adjust the characteristics of the frequency multiplier. Multi-section left and right hand composite nonlinear transmission lines also belong to the scope of the present invention.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a frequency multiplier is characterized in that, this frequency multiplier is made of at least one composite left/right handed non-linear transmission lines unit, and this composite left/right handed non-linear transmission lines unit is in series by single-unit left-hand nonlinear transmission line and single-unit right-handed nonlinear transmission line.

2. frequency multiplier as claimed in claim 1 is characterized in that, described single-unit left-hand nonlinear transmission line comprises:

First fixed capacity that is connected in series and second fixed capacity;

Be series at first variable capacitance between this first fixed capacity and second fixed capacity;

Be parallel to first inductance between this first fixed capacity and first variable capacitance; And

Be parallel to second inductance between this first variable capacitance and second fixed capacity.

3. frequency multiplier as claimed in claim 1 is characterized in that, described single-unit right-handed nonlinear transmission line comprises:

The 3rd inductance that is connected in series and the 4th inductance; And

Be parallel to second variable capacitance between the 3rd inductance and the 4th inductance.

4. as claim 2 or 3 described frequency multipliers, it is characterized in that described first variable capacitance or second variable capacitance are made of the PIN diode of automatic biasing.

5. frequency multiplier as claimed in claim 4, it is characterized in that, described first variable capacitance or second variable capacitance are relevant with the amplitude of input signal, when the amplitude of input signal greater than cut-in voltage as the PIN diode of variable capacitance, then the appearance value of variable capacitance changes DC channel into by a less fixed value, i.e. big capacitance, and produce the harmonic wave that frequency is the input signal integral multiple thus.

6. frequency multiplier as claimed in claim 1 is characterized in that, described composite left/right handed non-linear transmission lines unit has bandpass characteristics, is used to transmit the microwave signal of characteristic frequency.

7. frequency multiplier as claimed in claim 1 is characterized in that, the input of described composite left/right handed non-linear transmission lines unit is a right-handed nonlinear transmission line, and output is a left-hand nonlinear transmission line.

8. frequency multiplier as claimed in claim 1 is characterized in that, by the capacitance of selection variable capacitance and the inductance value of inductance, can obtain and input port/output port matched transmission line characteristic impedance, need not independently match circuit.

9. frequency multiplier as claimed in claim 1 is characterized in that, when this frequency multiplier was made of a plurality of composite left/right handed non-linear transmission lines unit, these a plurality of composite left/right handed non-linear transmission lines cell string connected.

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