JP3519262B2 - High frequency suppression circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a radio frequency band.
Frequency f₀And 3f₀To suppress high-frequency signals
Small and frequency 2f₀Affects high frequency signals
It relates to a high frequency suppression circuit that cannot be obtained. [0002] 2. Description of the Related Art Multipliers or harmonic mixers
In the following, the leakage fundamental wave suppression and conversion efficiency at the output end
For the purpose of improvement, a high frequency suppression circuit for the fundamental wave is used.
It is. Here, the multiplier is a frequency f₀High frequency signal
(Hereinafter, referred to as “fundamental wave”), and double frequency 2f
₀That output a high-frequency signal (hereinafter referred to as a second harmonic)
It is. Further, as a harmonic mixer, the frequency f₀High lap of
Wave signal as a local oscillation signal, and its second harmonic
(Frequency 2f₀) And frequency f_IF(F_IF<< 2f₀:frequency
Number f_IFIs the frequency 2f₀High frequency that is much smaller than)
The signal is input as an intermediate frequency signal, and a mixed wave (frequency
Wave number 2f₀+ F_IFOr 2f₀−f_IF) Outputs
Yes, in this case, a high frequency suppression circuit is used. these
Basically, high-frequency suppression circuits used in harmonic mixers
In addition to suppressing the waves, there is no effect on the second harmonic
Required. Conventionally, a specific frequency f₀High frequency signal with
As shown in FIG. 6, a high frequency suppression circuit for suppressing
Frequency f₀The electrical length at is π / 2 and one end is open
Circuits composed of high-frequency transmission lines
You. 6, reference numeral 1 denotes an input terminal, and reference numeral 2 denotes an output terminal.
And reference numeral 3 denotes a high frequency connecting the input terminal 1 and the output terminal 2
Transmission line, code 8 is frequency f₀Electrical length π / 2 at
A high-frequency transmission line having one end open,
Each is connected as shown in FIG. High frequency transmission line
If the transmission loss of the circuit is ignored, high-frequency transmission with one end open
The input impedance Z of the line is Z = -j · Z₀・ Cotθ (1) It is expressed as Where j is the imaginary unit, Z₀Is high frequency transmission
The characteristic impedance of the line, θ, is the electrical length. Yo
And the frequency f₀The electrical length is π for the high-frequency signal
/ 2 input impedance of high-frequency transmission line 8 with one end open
Dance Z_(f0)Is given by equation (1) Z_(f0)= −j · Z₀・ Cotθ = −j · Z₀・ Cot (π / 2) = 0 This is equivalent to the input terminal being short-circuited. Yo
Therefore, in the circuit shown in FIG.₀Is high frequency
The signal is totally reflected by the high-frequency transmission line 8 and is not output.
No. On the other hand, for the second harmonic, the wavelength of the second harmonic is
(Λ₀/ 2), so that a high-frequency transmission line of the same length
The electrical length is twice the electrical length for the fundamental wave. In addition,
Wavelength λ₀Represents the wavelength of the fundamental wave. Therefore, high frequency transmission
Length λ added to line 3₀High circumference with one end of / 4 open
Impedance Z of the wave transmission line 8_(2f0)Is the expression
The following is obtained from (1). Z_(2f0)= −j · Z₀・ Cotθ = −j · Z₀・ Cot (2 ・ π / 2) = ∞ That is, in the second harmonic, the height as viewed from the high-frequency transmission line 3
Since the frequency transmission line 8 is equivalent to an open circuit, it is shown in FIG.
The high frequency suppression circuit does not affect the second harmonic. What
In Equation (1), the periodicity of the cot function indicates that
The high frequency suppression circuit shown in FIG.₀Odd)
Next harmonic (frequency 3f₀, 5f₀, 7f₀, 9f₀Etc.)
Frequency f₀Total reflection and output as well as behavior for
No, but even-order harmonics (frequency 2f₀, 4f₀, 6
f₀, 8f₀Etc.) for frequency 2f₀Behavior for
Similarly, it can be seen that it has no effect. However, as shown in FIG.
In the high-frequency suppression circuit shown in FIG.
/ 2 to use a long high-frequency transmission line, 1) The circuit becomes large when integrated circuits are used. 2) Poor suppression characteristics due to line loss of long high-frequency transmission line
There was a problem such as becoming. In order to solve such a problem, FIG.
The high frequency suppression circuit shown is proposed. High circumference shown in FIG.
The wave suppression circuit is an electric circuit in the high frequency suppression circuit shown in FIG.
By shortening the high-frequency transmission line 8 having a length of π / 2,
The circuit was downsized (Okazaki, Nakatsugawa: “High
Frequency suppression circuit ", JP-A-9-223905). Figure 7
Reference numeral 1 is an input terminal, reference numeral 2 is an output terminal, and reference numeral 3 is an input terminal.
High-frequency transmission line connecting the input terminal 1 and the output terminal 2, code
9 is the characteristic impedance Z₀, Frequency f₀Electrical length in
θ₀High-frequency transmission line (where 0 <θ₀<Π / 2), sign
10 is the capacitance value C ₁But C₁= 1 / (2π · f₀・ Z₀・ Tan θ₀) , The symbol 11 is a capacitance value C_TwoBut C_Two= C₁・ Cos^Twoθ₀/ (2 cos^Twoθ₀+1) Are connected as shown in FIG.
Has been continued. In the high frequency suppression circuit shown in FIG.
Impedance Z₀, A high-frequency transmission line 9 having an electrical length θ
Grounded capacitor 10 (capacitance value: C₁= 1 / (2π
・ F₀・ Z₀・ Tan θ₀Input impedance of the circuit consisting of
Dance Z_aIs at frequency f (Equation 1)It is. Accordingly, a capacitor grounded in parallel with this circuit
Pasta 11 (Capacity value: C_Two= C₁・ Cos^Twoθ₀/ (2co
s^Twoθ₀+1)) from the perspective of the high-frequency transmission line 3
Input impedance Z_inAt the frequency f (Equation 2) It becomes. Fundamental wave, ie frequency f = f₀Input for
Impedance Z_{in (f0)}Is f = f₀And θ = θ₀The expression
If the value is substituted into (2), it becomes "0" and the input terminal is short-circuited.
Is equivalent to Therefore, the frequency f₀High frequency signal
No signal is output. On the other hand, the second harmonic, that is, the frequency f =
2f₀Input impedance Z at_{in (2f 0)}Is f = 2
f₀And θ = 2θ₀Is substituted into equation (2), the denominator
Is “0”. Therefore, the input in the second harmonic
Peedance Z_{in (2f0)}Becomes infinite and is equivalent to opening.
You. Therefore, the high frequency suppression circuit shown in FIG.
It has no effect. [0007] FIG. 8 is shown in FIG.
Simulation result of pass gain in high frequency suppression circuit
It is a figure showing a result. Basic in simulation
Wave frequency f₀Is 2.5 [GHz], and the high-frequency transmission shown in FIG.
Characteristic impedance Z of transmission line 9₀Is 50 [Ω], electricity
Length θ₀Is 7.94 degrees, and the capacitance value of the capacitor 10 is C₁= 1
/ (2π · f₀・ Z₀ ・ Tan θ₀8.)
12 [pF] and the capacitance value of the capacitor 11 is C_Two= C₁・ C
os^Twoθ₀(2 cos^Twoθ₀+1), which is 3.02 [p
F]. From FIG. 8, the fundamental wave (2.5 [GHz])
Characteristics for the second harmonic (5.0 [GHz])
Although the over characteristic is sufficient, the third harmonic (7.5 [GH
z]), only 8 [dB] is obtained.
Not in. Thus, in the high frequency suppression circuit shown in FIG.
Shows that only the fundamental wave is sufficiently suppressed and is shown in FIG.
The suppression of the third and higher odd harmonics is less
It is enough. In particular, a system in which the desired wave is in the vicinity of the second harmonic
When applied to a harmonic, the harmonic suppression circuit
Third harmonics with similar numbers require a sufficient amount of suppression, similar to the fundamental wave
In this case, the high-frequency suppression shown in FIG.
There is a problem with the pressure circuit. That is, the high frequency suppression shown in FIG.
In a voltage circuit, a high-frequency transmission line with a short electrical length to the fundamental wave
The circuit 9 can be used to reduce the size of the circuit when forming an integrated circuit.
Deterioration of suppression characteristics due to molding and line loss of high-frequency transmission lines
Can be prevented, but sufficient for the third harmonic
There is a problem that suppression cannot be performed. The present invention has been made in view of such circumstances.
Which suppresses the fundamental wave and the third harmonic,
Providing a small high-frequency suppression circuit that does not affect the second harmonic
The purpose is to provide. [0009] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The present invention provides a first high-frequency transmission connecting two terminals of input and output.
One end of the line is connected to one point on the first high-frequency transmission line.
Continued characteristic impedance Z₁, Frequency f₀Smell
Electrical length is θ₁A second high-frequency transmission line,
One end is connected to the other end of the high-frequency transmission line, and the other end is grounded.
And the first high-frequency transmission line
At or near the connection point with the second high-frequency transmission line
Characteristic impedance Z with one end connected_Two, Frequency f₀
Electrical length at θ_Two(However, 0 <θ_Two<Π / 6)
The third high-frequency transmission line and the third high-frequency transmission line
One end is connected to one end and the other end is grounded.
A high-frequency suppressing circuit comprising:
Wave transmission line frequency f₀Electrical length θ at₁But θ₁= Tan^-1(((αβ + ((αβ)^Two+4)^(1/2)) / 2)^(1/3)
+ ((Αβ-((αβ)^Two+4)^(1/2)) / 2)^(1/3)) Where α = Z_Two/ Z₁ β = (3tan^Fiveθ_Two+5 tan θ_Two) / (5tan^Twoθ_Two+1) Within a predetermined error around an ideal value, and
(0 <θ₁<Π / 2).
The capacitance value C of one capacitor₁But the second high-frequency transmission
Line frequency f₀Value of electrical length at₁Against C₁= 1 / (2π · f₀・ Z₁・ Tan θ₁) Within a predetermined error centered on the second
Capacitor capacitance value C_TwoBut, C_Two= 1 / (6π · f₀・ Z_Two・ Tan (3θ_Two)) Within a predetermined error centered on
It is a high frequency suppression circuit. [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, according to one embodiment of the present invention.
The high frequency suppression circuit will be described with reference to the drawings. Figure 1 is a book
FIG. 2 is a diagram illustrating a configuration of a high-frequency suppression circuit according to the invention. FIG.
, Reference numeral 1 denotes an input terminal, reference numeral 2 denotes an output terminal, and reference numeral
3, 4 and 6 are high-frequency transmission lines, and 5 and 7 are keys.
It is Japashita. The high-frequency transmission line 4 has a characteristic impedance.
-Dance Z₁And the frequency f₀Electrical length θ at₁Is
(However, θ₁Has a specific value described later), the capacitor
5 is the capacitance value C₁But, C₁= 1 / (2π · f₀・ Z₁・ Tan θ₁) It is. On the other hand, the high-frequency transmission line 6 has a characteristic impedance
Z₂And the frequency f₀Electrical length θ at₂And (but
0 <θ ₂ <Π / 6), the capacitance value of the capacitor 7 is C₂But, C₂= 1 / (6π · f₀・ Z₂・ Tan (3θ₂)) It is. Also, the frequency f of the high-frequency transmission line 4₀In
Electrical length θ₁Is θ₁= Tan^-1 (((αβ + ((αβ)²+4) ^{( 1 / Two )}) / 2)^{( 1 / Three )} + ((Αβ-((αβ)²+4)^{( 1 / Two )}) / 2)^{( 1 / Three )}) Where α = Z₂/ Z₁ β = (3tan⁵θ₂+5 tan θ₂) / (5tan²θ₂+1)
0 <θ shown₁<Π / 2, Z₁, Z₂And
And θ₂Has a value determined by the value of. And, as shown in FIG.
The path 4 is located on the high-frequency transmission line 3 connecting the input and output terminals.
One end is connected to a point, and the capacitor 5 is connected to the high-frequency transmission line 4.
Is connected to one end and the other end is grounded. one
On the other hand, the high-frequency transmission line 6 is
One end is connected to the connection point with the transmission line 4 and the capacitor 7
Has one end connected to the other end of the high-frequency transmission line 6 and the other end
Grounded. Note that the above electrical length θ₁, Capacitance value C₁, C
_TwoIs the ideal value when there is no transmission loss in the high-frequency transmission line.
In the case of realizing the high frequency suppression circuit of FIG.
Error range determined from the accuracy required for this circuit
Just do it. Similarly, the high-frequency transmission line of the high-frequency transmission line 6
The connection point with 3 is based on the accuracy required for the high-frequency suppression circuit.
Within the determined error range, the high frequency transmission line 3 and the high frequency
It suffices if it is near the connection point with the wave transmission line 4. In such a circuit configuration, in the circuit shown in FIG.
High-frequency transmission line viewed from the high-frequency transmission line 3 of the wave suppression circuit
Input impedance of circuit consisting of path 4 and capacitor 5
Z_aAt the frequency f (Equation 3) It becomes. On the other hand, from the high-frequency transmission line 3 of the high-frequency suppression circuit
In this case, the loop composed of the high-frequency transmission line 6 and the capacitor 7
Road input impedance Z_bAt the frequency f (Equation 4)It becomes. Therefore, the high-frequency transmission line of the high-frequency suppression circuit of FIG.
Input impedance Z seen from road 3_inIs the frequency f
And (Equation 5) It becomes. Here, the fundamental wave, that is, the frequency f = f₀so
Is (Equation 6) And θ_a= Θ₁The high-frequency transmission line 4 and the key
Input impedance at fundamental wave of circuit consisting of capacitor 5
Dance Z_{a (f0)}Becomes "0". At this time,
The fundamental wave of the circuit consisting of the transmission line 6 and the capacitor 7
Input impedance Z_{b (f0)}Is not "0". Yo
Therefore, the input in the fundamental wave of the harmonic suppression circuit
Peedance Z_{in (f0)}Becomes “0” from equation (3),
It is equivalent to the ends being short-circuited. Therefore, the frequency f₀
It can be seen that the high frequency signal is not output. Next, the third harmonic, ie, frequency f = 3f₀
Then (Equation 7) And θ_b= 3θ_TwoThus, the high-frequency transmission line 6 and
The input impedance at the third harmonic of the circuit consisting of the capacitor 7
-Dance Z_{b (3f0)}Becomes "0". On the other hand, high-frequency transmission lines
At the third harmonic of the circuit consisting of the path 4 and the capacitor 5
Input impedance Z_{a (3f0)}Is not "0". Therefore,
Input impedance at third harmonic of harmonic suppression circuit
Z_{in (3f0)}Is “0” from equation (3), and the input end is
It is equivalent to a short circuit. Therefore, frequency 3f₀so
It can be seen that a certain high frequency signal is not output. On the other hand, the second harmonic, ie, frequency f = 2f₀
Then (Equation 8) From the high-frequency transmission line 3 of the high-frequency suppression circuit.
A circuit comprising a high-frequency transmission line 4 and a capacitor 5
Input impedance Z at the second harmonic of_{a (2f0)}Is (Equation 9) It is. Here, as described above, the frequency of the high-frequency transmission line 4
Number f₀Electrical length θ at₁Is θ₁= Tan^-1(((αβ + ((αβ)^Two+4)^(1/2)) / 2)^(1/3)
+ ((Αβ-((αβ)^Two+4)^(1/2)) / 2)^(1/3)) Where α = Z_Two/ Z₁ β = (3tan^Fiveθ_Two+5 tan θ_Two) / (5tan^Twoθ_Two+1) From (Equation 10) It becomes. Note that the electrical length θ₁Is a real value, so tanθ₁
And its cubic value is also a real number, (Equation 11) It becomes. Therefore, the input impedance Z_{a (2f0)}Is (Equation 12) It becomes. On the other hand, the high-frequency transmission line 3 of the high-frequency suppression circuit
From the high-frequency transmission line 6 and the capacitor 7
Impedance Z at the second harmonic of the circuit
_{b (2f0)}Is (Equation 13) It is. Therefore, the input impedance Z_{b (2f0)}Is [Equation 14] It becomes. Therefore, the high frequency transmission line 3 of the high frequency suppression circuit
Input impedance Z at the second harmonic
_{in (2f0)}Is the input impedance determined above
Z_{a (2f0)}, Z_{b (2f0)}From the value of (Equation 15) It becomes. Here, the numerator of the above formula is not “0”, and
The denominator is “0”. Therefore, the input impedance Z
_{in (2f0)}Is infinite, which is equivalent to opening
It is clear that the frequency suppression circuit has no effect on the second harmonic.
Call Therefore, the frequency f₀0 <θ at₀<Π /
6 arbitrary electrical length θ_TwoHigh-frequency transmission line 6 with
Capacitors 5 and 7 having specific capacitance values of
Shortening the length of the wave transmission line 4 to the above specified length
To suppress the fundamental wave and the third harmonic,
A small high-frequency suppression circuit that has no effect
You. FIG. 2 shows a graph corresponding to a fundamental wave of 2.5 [GHz].
Simulation results of the pass characteristics of the high frequency suppression circuit of FIG.
It is a figure showing a result. The high-frequency transmission line 6 in FIG.
Electrical length for frequency 2.5 [GHz] shortened to 5 degrees
And its characteristic impedance Z_TwoIs 50 [Ω]
Was. Further, the characteristic impedance of the high-frequency transmission line 4 in FIG.
Dance Z₁Is set to 50 [Ω], and the frequency is 2.5 [GH].
z] electrical length₁, Capacitance of capacitors 5 and 6
Value C₁And C_TwoAre θ₁= Tan^-1(((αβ + ((αβ)^Two+4)^(1/2)) / 2)^(1/3)
+ ((Αβ-((αβ)^Two+4)^(1/2)) / 2)^(1/3)) (However, α = Z_Two/ Z₁ β = (3tan^Fiveθ_Two+5 tan θ_Two) / (5tan^Twoθ_Two+1)) C₁= 1 / (2π · f₀・ Z₁・ Tanθ₁) C_Two= 1 / (6π · f₀・ Z_Two・ Tan (3θ_Two)) 7.94 degrees and 9.
Simulation as 12 [pF], 1.58 [pF]
Performed. As is clear from FIG.
The voltage circuit has a fundamental wave of 2.5 GHz and a third harmonic.
At 7.5 [GHz], the pass gains are each -60.
[DB] or less, -50 [dB] or less, sufficient suppression effect
At 5.0 [GHz] of the second harmonic obtained,
The overgain is almost 0 [dB], and the effect on the second harmonic is
It turns out that it does not give. FIG. 3 is an enlarged view of the vicinity of the fundamental wave in FIG.
4 is an enlarged view of the vicinity of the second harmonic of FIG. 2, and FIG. 5 is the third harmonic of FIG.
It is an enlarged view of the vicinity. From Fig. 4, the pass loss in the second harmonic band
Is less than or equal to 1 [dB] in the range of 4.75 to 5.25 [G
Hz] and about 500 [MHz]. In addition,
The corresponding transmission losses in the fundamental band and the third harmonic band are shown in Fig. 3.
From FIG. 5 and FIG. 5, 30 [dB] or more and 25 [dB], respectively.
The above shows a sufficient suppression characteristic. That is, high frequency
The suppression circuit sufficiently suppresses the frequencies near the fundamental wave and the third harmonic.
Characteristics that do not affect the frequency near the second harmonic
have. Therefore, the capacitance of the capacitors 5 and 7
Value, or each variable used in the formula to calculate the capacitance value, high
The characteristic impedance of the frequency transmission lines 4 and 6, and
Even if the error with respect to the electrical length is about several percent, the present invention
The fundamental wave and the third harmonic of the high frequency suppression circuit of
There is no effect on the characteristic of not affecting the second harmonic.
No. Similarly, the high-frequency transmission line at the connection point of the high-frequency transmission line 6
The deviation from the connection point between the road 3 and the high-frequency transmission line 4 is also
Small amounts are acceptable. [0020] As described above, the high-frequency suppression of the present invention
According to the voltage circuit, the fundamental wave and the third harmonic are suppressed,
A compact high-frequency suppression circuit that does not affect harmonics
Can appear. Therefore, a multiplier that inputs a fundamental wave and outputs a second harmonic
Doubler and frequency f₀High frequency signal as a local oscillation signal
The second harmonic (frequency 2f₀) And the frequency f_IF
(F_IF<< 2f₀) Is the intermediate frequency signal
And a mixed wave of both (frequency 2f₀+ F_IFAlso
Is 2f₀−f_IF) In the harmonic mixer
Suppresses the leakage fundamental wave and the third harmonic at the force end and
To improve the conversion efficiency, the fundamental wave and the third harmonic
Frequency multiplier can be realized in a compact size,
And a harmonic mixer can be realized in a small size.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a high-frequency suppression circuit according to the present invention. FIG. 2 is a diagram showing a simulation result of a pass characteristic of the high frequency suppression circuit according to the present invention. FIG. 3 is an enlarged view showing the vicinity of a fundamental wave in FIG. 2; FIG. 4 is an enlarged view of the vicinity of the second harmonic of FIG. 2; FIG. 5 is an enlarged view of the vicinity of the third harmonic of FIG. 2; FIG. 6 is a diagram illustrating a configuration diagram of a conventional example of a high-frequency suppression circuit. FIG. 7 is a diagram showing a configuration diagram of a conventional example of a miniaturized high-frequency suppression circuit. FIG. 8 is a diagram showing a simulation result of a pass characteristic of the high frequency suppression circuit of FIG. 7; [Description of Signs] 1 input terminal 2 output terminal 3 high-frequency transmission line 4 high-frequency transmission line 5 capacitor 6 high-frequency transmission line 7 capacitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01P 1/203-1/202 H03D 7/00 H03F 1/00-3/00

Claims (1)

(57) [Claims] 1. A first high-frequency transmission connecting two terminals of input and output
Tracks and One end is connected to one point on the first high-frequency transmission line.
The characteristic impedance Z₁, Frequency f₀Electricity in
Length is θ₁A second high-frequency transmission line, One end is connected to the other end of the second high-frequency transmission line, and the other
A first capacitor having an end grounded; Between the first high-frequency transmission line and the second high-frequency transmission line
Characteristic input with one end connected at or near the connection point
Peedance Z_Two, Frequency f₀Electrical length at θ _Two(However
0 <θ_Two<Π / 6) third high-frequency transmission line; One end is connected to the other end of the third high-frequency transmission line,
RF suppression with a second capacitor grounded at the end
A circuit, The frequency f of the second high-frequency transmission line₀Electrical length in
θ₁But θ₁= Tan^-1(((αβ + ((αβ)^Two+4)^(1/2)) / 2)^(1/3)
+ ((Αβ-((αβ)^Two+4)^(1/2)) / 2)^(1/3)) Where α = Z_Two/ Z₁ β = (3tan^Fiveθ_Two+5 tan θ_Two) / (5tan^Twoθ_Two+1) Within a predetermined error around an ideal value, and
(0 <θ₁<Π / 2). The capacitance value C of the first capacitor₁But the second high circumference
Wave transmission line frequency f₀Ideal value θ of the electrical length at₁
Against C₁= 1 / (2π · f₀・ Z₁・ Tan θ₁) Within a predetermined error centered on The capacitance value C of the second capacitor_TwoBut, C_Two= 1 / (6π · f₀・ Z_Two・ Tan (3θ_Two)) Within a predetermined error centered on
High frequency suppression circuit.