An electronic impedance tuner, comprising an adjusting circuit, N cell tuning circuits identical in structure and a switch controller,
- wherein N is an integer greater than or equal to 2, the adjusting circuit has an input terminal, an output terminal and a control terminal, each said cell tuning circuit has an input terminal, an output terminal and a control terminal, the switch controller has N+1 output terminals and is used for controlling on/off of the adjusting circuit and the N cell tuning circuits, the output terminal of the adjusting circuit is connected to the input terminal of the first cell tuning circuit, the output terminal of the jth cell tuning circuit is connected to the input terminal of the (j+1)th cell tuning circuit, j=1, 2, . . . , and N−1, and the N+1 output terminals of the switch controller are connected to the control terminal of the adjusting circuit and the control terminals of the cell tuning circuits in a one-to-one correspondence manner;
- the adjusting circuit comprises a first microstrip line, a second microstrip line, a first capacitor, a second capacitor, a third capacitor, a first inductor, a second inductor and a first PIN diode;
- the first microstrip line has a terminal used as the input terminal of the adjusting circuit and a terminal connected to a terminal of the first capacitor and a terminal of the second capacitor, the first capacitor has a terminal connected to a negative electrode of the first PIN diode and a terminal of the second microstrip line, the second microstrip line has a terminal used as the output terminal of the adjusting circuit, the second capacitor has a terminal connected to a terminal of the first inductor and a positive electrode of the first PIN diode, the first inductor has a terminal connected to a terminal of the third capacitor, a corresponding connecting terminal is the control terminal of the adjusting circuit, another terminal of the third capacitor is grounded, and the second microstrip line is grounded via the second inductor;
- each said cell tuning circuit comprises a third microstrip line, a fourth microstrip line, a fourth capacitor, a fifth capacitor, a second PIN diode and a third inductor, wherein the third microstrip line has a terminal used as the input terminal of the cell tuning circuit and a terminal connected to a terminal of the fourth capacitor and a terminal of the fourth microstrip line, the fourth microstrip line has a terminal used as the output terminal of the cell tuning circuit, the fourth capacitor has a terminal connected to a positive electrode of the second PIN diode and a terminal of the third inductor, a negative electrode of the second PIN diode is grounded, the third inductor has a terminal connected to a terminal of the fifth capacitor, a corresponding connecting terminal is the control terminal of the cell tuning circuit, and another terminal of the fifth capacitor is grounded;
- a capacitance the fourth capacitor is marked as Cd and meets the condition:
- 4
-
-
- Y
- s
- N
-
-
- π
-
-
- f
- 2
-
-
- Γ
- req
-
- 1
- -
-
- Γ
- req
-
- 2
- ≤
- C
- d
- ≤
- Y
- s
- π
-
-
- f
- 1
-
-
- Γ
- req
-
- 1
- -
-
- Γ
- req
-
- 2
- ,
- wherein Ys is a source admittance, f1 is a lower limit of a design operating frequency range, f2 is an upper limit of the design operating frequency, Γreq is a maximum design reflection coefficient, ∥ is an absolute value symbol, and π is a symbol of Pi;
- a length of the third microstrip line is equal to that of the fourth microstrip line, an impedance of the third microstrip line is equal to that of the fourth microstrip line, and the length of the third microstrip line is marked as d and meets the condition:
- λ
- 1
- /
- 4
-
- (
- N
- +
- 1
- )
- <
- d
- <
- c
- 4
-
- ɛ
- reff
-
- [
- (
- C
- d
- ·
- Z
- 0
- )
- 2
- +
- (
- 2
- π
-
-
- f
- Bragg
- )
- 2
- -
- C
- d
- ·
- Z
- 0
- ]
- ,
- wherein c refers to a light speed and has a value of 2.998×108 m/s, fBragg refers to a Bragg cut-off frequency and has a value ranging from 1.2 f2 to 1.7 f2, εreff is an effective dielectric constant of the third microstrip line, Z0 is the impedance of the third microstrip line and has a value ranging from 70Ω to 110Ω, λ1 is a wavelength corresponding to the lower limit f1 of the design operating frequency range, and the first microstrip line and the second microstrip line both have an impedance of 50Ω.