JP3128277B2 - Mixer circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave integrated circuit (M).
IC).

[0002]

2. Description of the Related Art A mixer in a microwave band is, for example, B
An S converter or the like is one of the typical applied products, and a conventional technology of a mixer circuit including a filter will be described below using a BS converter as an example.

A satellite broadcasting (BS) receiver converts a 12 GHz band high frequency (RF) signal received from an antenna to 1 GHz.
A frequency converter (BS converter) for converting to the intermediate frequency (IF) of the band is required.

FIG. 2 is a block diagram showing the internal configuration of the BS converter. 11.7 received from BS antenna (14)
RF reception signal of 1398 to 12.0095 GHz is BS
An intermediate frequency (IF) signal is amplified by an RF amplifier circuit (10) in the converter and mixed with a local (LO) signal from a 10.678 GHz local oscillation circuit (13) by a mixer circuit (11) at the next stage. , And amplified by the IF amplifier circuit (12).

[0005] Usually, the mixer (11) in the converter in such a high-frequency region is constituted by a distributed constant circuit using a microstrip line, and a non-linear element such as a diode is used. In this case, the image frequency is 9.3.
An interfering signal (f _I ) of 465 to 9.64202 GHz;
A filter for suppressing the LO frequency leakage signal is required before the mixer.

Conventionally, the mixer (11) is configured as shown in FIG. Although there are various types of MIC mixers, there is a mixer using a diode element (5). Such a mixer using one diode is called a single-ended mixer.

The single-ended mixer has an advantage that a low-cost and small-sized mixer can be constructed because only one diode is required, which is more expensive than a balanced mixer which requires a plurality of diodes.

However, since there is no function to balance and cancel the LO frequency power, there is a disadvantage that LO frequency leakage is large.

Therefore, in the conventional single-ended mixer, means for reducing the leakage of the LO frequency, for example, the filters (14) and (15) as shown in FIG. ) And R
It is inserted to prevent the F signal from being lost.

[0010] Filters (14) and (15) in front of mixer
Plays a role of passing an RF signal of 11.7 to 12 GHz and suppressing an interference signal at an image frequency and a leakage signal at an LO frequency.

By the way, with the recent spread of BS receivers to general households, BS receivers are becoming smaller, lighter and have higher gain. Accordingly, it is necessary to reduce the size of the BS converter attached to the antenna, and accordingly, it is necessary to reduce the size of the mixer (11) including the filter as much as possible.

However, in the configuration of FIG. 3, the RF signal and the LO
A certain amount of space is required for a filter for separating signals and a directional coupler having a high Q is used as a filter, which further complicates the structure and hinders miniaturization.

Therefore, as shown in FIG. 4, it is conceivable to input the LO signal from the IF side instead of the RF side and omit the filter.

[0014]

With the configuration of the band-pass filter (17) as shown in FIG. 4, further miniaturization is impossible.

[0015]

SUMMARY OF THE INVENTION In a BS converter, R
Since the frequency is converted by the LO signal having a frequency slightly lower than the F signal, the image disturbing frequency becomes lower than the LO signal. Therefore, a high-pass filter (HPF) can be used as an RF signal input filter.

Therefore, the present invention relates to a microwave integrated circuit having a microstrip line as a basic configuration, and converts a high frequency signal (f _RF ) and a local oscillation signal (fLO) having a frequency lower than the high frequency signal into a high frequency signal in the forward direction. The two signals (f _RF ) are mixed by a single balance mixer composed of a diode (5) connected to be on the signal input side.
Intermediate frequency signal (f _IF ) which is a difference frequency component of (f _LO )
In the mixer circuit (11) for outputting a signal, a plurality of tip short-circuit stubs are provided, and the local oscillation signal (f _LO ) and the intermediate frequency signal (f _IF ) as viewed from the diode (5) are provided on the high frequency signal input side. Is short-circuited at the connection point of the diode (5) so that the length of the short-circuit stub near the connection point of the diode (5) is equal to the local oscillation signal (f _LO ).
A high-pass filter (4), which is set sufficiently smaller than 波長 of the wavelength of the frequency and passes a high-frequency signal,
On the opposite side of the diode (5), an open-ended microstrip line (6) having an impedance such that the high-frequency signal (f _RF ) is short-circuited at the connection point of the diode (5) and opened at the end is inserted. It is.

[0017]

According to the present invention, the length of the short-circuit stub near the connection point of the diode (5) is determined by the local oscillation signal (f _LO ).
Is set sufficiently smaller than 波長 of the wavelength of the frequency of the local oscillation signal (f _LO ) and the intermediate frequency signal (f _LO ).
_IF ) can be shorted together at the connection point of the diode (5). Therefore, the length of the short-circuit stub near the connection point of the diode (5) is set to be sufficiently smaller than １ ／ of the wavelength of the frequency of the local oscillation signal (f _LO ), and the short-circuit pattern of the high-pass filter (4) is set. And the local oscillation signal (f
_Since the short-circuit plane of the _LO signal and the intermediate frequency signal (f _IF ) can be shared, the size of the high-pass filter (4) can be reduced, and as a result, the size of the mixer circuit (11) can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiment shown in FIG.
However, the bias circuit is omitted in FIG.

On the RF signal input side, an HPF (4) for passing an RF signal whose LO frequency and IF frequency are short-circuited at the connection point of the diode as viewed from the diode (5) is inserted.

The filter (4) has a fifth-order structure, and is short-circuited at six positions at both ends. That is, each tip is grounded to the ground on the back surface by the through hole.

The short-circuiting pattern near the diode (5) of the HPF (4) has a short-circuit impedance with respect to the two signals LO and IF, and also serves as a conduction circuit for flowing a diode current, thereby efficiently converting the two signals. It is often applied to the diode (5). The length (l) of the short-circuit pattern near the diode (5) is 、 of the wavelength of the LO frequency.
Since it is designed to be much smaller (for example, 1/3), L
Both the O signal and the IF signal are short-circuited. On the other hand, on the opposite side of the diode (5), an open-end stub (6) having an impedance such that the RF signal is short-circuited at the connection point of the diode and the RF signal is open at the end is inserted.

The open-end stub (8) has a length of λ _LO / 4 with respect to the LO signal wavelength λ _LO and has a LO input end (2).
An LO signal is added at a position longer than λ _LO / 4 so that the LO signal is efficiently applied to the diode side.

The RF signal input from the terminal (1) passes through the HPF (4) having characteristics as shown in FIG.

The RF signal is inputted from terminal (2) to L
The signal is mixed with the O signal and the diode (5). The open-end stub (6) is RF-open at the distal end with a length of λ _RF / 4 with respect to the RF signal wavelength λ _RF , and short-circuited at the connection point of the diode (5). However, since the open-end stub (6) affects the impedance of the LO signal, an open-end stub (7) is added to match the LO signal.

As described above, the RF signal is frequency-converted by the diode (5) and output from the terminal (3) as an IF signal.

[0026]

According to the configuration of the HPF (4) using the microstrip line, the short-circuit pattern of the filter and the short-circuit surface of the LO and IF signals can be shared, and the mixer circuit can be downsized. In the present invention, the mixer circuit (11) in the BS converter has been described as an example.
Of course, the present invention is effective in the case of an MIC mixer whose signal frequency is higher than the LO signal frequency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pattern diagram of an embodiment of the present invention.

FIG. 2 is a block diagram showing the internal configuration of a BS converter.

FIG. 3 is a diagram illustrating a configuration example of a conventional MIC mixer.

FIG. 4 is a diagram showing a configuration example of a conventional MIC mixer.

FIG. 5 is a diagram showing an example of characteristics of an HPF filter used in the present invention.

[Explanation of symbols]

 5 diode, 4 high pass filter, 6 stub, 7 stub.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiyoo Hanafusa 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-63-126305 (JP, A) JP-A Sho 62-241408 (JP, A) JP-A-58-141005 (JP, A) JP-A-62-75619 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03D 9/06 H03D 7/00-7/02 H01P 1/203

Claims (1)

(57) [Claims] 1. A microstrip line having a basic configuration
High frequency signal (f_RF) And the height
Local oscillation signal (f_LO) And
Connected so that the forward direction is the high frequency signal input sideDie
By single balance mixer composed of Aether (5)
Mix and mix the two signals (f_RF) (F_LO) Difference frequency
The intermediate frequency signal (f_IF) Output mixer
In the circuit (11),Consists of multiple tip short-circuit stubs, High frequency signal input side
The local oscillation viewed from the diode (5).signal
(F_LO) And intermediate frequencysignal(F_IF) Is the diode
Short-circuit at connection point (5)So the diode
The length of the tip short-circuit stub near the connection point of (5) is the local part.
Oscillation signal (f _LO ) Is sufficiently smaller than 1/4 of the wavelength of the frequency
Is setHigh-pass filter that passes high-frequency signals
(4) Insert this diode on the opposite side of this diode (5)
At the connection point (5), the high-frequency signal (f_RF) Is short-circuited
Tip open with impedance open at the tip
Mixer with microstrip line (6) inserted
Road.