JP4593503B2 - Even harmonic mixer and its bandpass filter - Google Patents

Description

  The present invention relates to an even harmonic mixer, and more particularly to an even harmonic mixer applicable to a radio communication system, a transmission / reception device of a radar system, and the bandpass filter thereof.

  As documents disclosing a demultiplexing circuit and an even harmonic mixer applicable to a radio communication system and a transmission / reception device of a radar system, there are Patent Documents 1 and 2 shown below.

  For example, in Patent Document 1, an antiparallel diode pair in which two diodes are connected in parallel with opposite polarities, and a lumped constant in which a local oscillation wave frequency is short-circuited and a signal wave frequency is open-circuited. The first demultiplexing circuit configured by a combination of an inductor and a capacitor, and a combination of a lumped constant inductor and a capacitor that are open at the frequency of the local oscillation wave and short-circuited at the frequency of the signal wave Various configuration examples of an even harmonic mixer configured to include a second branching circuit are disclosed. In this even harmonic mixer, since a branching circuit is configured using a lumped constant element without using a stub, an increase in device size is suppressed in a low frequency band.

  In Patent Document 2, a high-pass filter is used for an even harmonic mixer configuration in which one of conventional antiparallel diode pairs is grounded in a DC (low frequency) manner and an IF signal is extracted only from the other. By connecting an RF / LO blocking circuit for preventing the passage of the RF signal and the LO signal while allowing the passage of the IF signal to both ends of the anti-parallel diode pair, respectively, A configuration example of an even harmonic mixer is disclosed in which an IF signal having a negative phase relation is extracted from the RF / LO blocking circuit of the present invention. In this even harmonic mixer, the outputs of the first and second branching circuits can be used as balanced signals, and it is not necessary to provide a special balun for converting IF signals into balanced signals. Suppressing the enlargement of devices and the like.

Japanese Patent Laid-Open No. 08-242123 JP 2000-252753 A

  By the way, as a technology for supporting advanced information communication, a low temperature co-fired ceramic multilayer substrate (Low Temperature Co-fired Ceramics: hereinafter abbreviated as “LTCC”) has been put into practical use. This LTCC is a ceramic substrate material that can be sintered at a low temperature compared to a general ceramic substrate material. By lowering the sintering temperature, it becomes possible to co-sinter with metals used for electrodes and circuit patterns. Various functional units can be configured (built in) inside. That is, if LTCC is used, a three-dimensional circuit can be easily formed, and the circuit module can be reduced in size and manufacturing cost can be reduced. For this reason, LTCC having such a feature is highly expected to be applied to various uses of microwave circuits and millimeter wave circuits, which are recently expanding the market.

  On the other hand, the technology for realizing the above Patent Documents 1 and 2 is based on the MMIC technology in which a semiconductor device, a passive circuit element, a transmission line, etc. are integrated on a substrate such as a semiconductor. It is not intended to have a multilayer substrate such as a (high-temperature fired substrate) or a build-up substrate.

  Actually, the frequency used in the microwave circuit and the millimeter wave circuit has reached about 100 GHz, and each functional component applied to such a high frequency band has a manufacturing accuracy of the order of several μm to several tens of μm. Required. Therefore, various difficulties are involved in applying the multilayer substrate such as the LTCC to the area of microwave circuits and millimeter wave circuits. In addition, thick film printing used for multilayer substrates such as the LTCC has a manufacturing limit, and it is difficult to realize a highly accurate pattern that can operate in the microwave band and the millimeter wave band.

  On the other hand, while we cannot expect rapid progress in manufacturing accuracy of thick film printing, reduction of manufacturing cost is a need from the market, and the application of multilayer laminated substrates to microwave circuits and millimeter wave circuits is This is unavoidable as a trend toward lower costs in the future. Therefore, an idea different from the prior art, that is, a circuit configuration technique for realizing a microwave circuit or a millimeter wave circuit by using a multilayer substrate such as LTCC without greatly depending on manufacturing accuracy has been desired.

  The present invention has been made in view of the above, and an object thereof is to provide an even harmonic mixer configured using a multilayer substrate such as LTCC and a bandpass filter thereof.

In order to solve the above-described problems and achieve the object, an even harmonic mixer according to the present invention includes an anti-parallel diode pair in which two diodes having different polarities are connected in parallel, and the anti-parallel diode pair. Connected to one end of the parallel diode pair to allow the passage of the RF signal while blocking the passage of the LO signal and the IF signal, and the LO signal and the IF at the connection end with the anti-parallel diode pair. A high-pass filter for short-circuiting the signal, connected to the other end of the anti-parallel diode pair, a band-pass filter for inputting an LO signal, and connected in parallel to the other end of the anti-parallel diode pair, A low-pass filter that prevents passage of the LO signal and outputs an IF signal generated based on the LO signal and the RF signal; In the even harmonic mixer provided, the bandpass filter includes a multilayer inter-layer arranged so that one signal conductor and the other signal conductor are opposed to each other between the upper and lower directions in the multilayer substrate lamination direction between predetermined layers constituting the multilayer substrate. A digital coupler; and a ground conductor extraction portion disposed below the stacked inter-digital coupler and electrically coupled to the stacked inter-digital coupler , wherein the anti-parallel diode pair includes: A dielectric resonator that resonates with an RF signal input from the other end via the multilayer inter-digital coupler.

  In the present invention, a laminated inter-digital coupler in which one ground conductor portion and the other ground conductor portion are arranged between the upper and lower sides in the multilayer substrate laminating direction between predetermined layers constituting the multilayer substrate, or an anti-parallel A dielectric resonator that resonates in the frequency band of the RF signal input from one output terminal of the diode pair via the stacked inter-digital coupler is included, but these components include LTCC, etc. The multilayer substrate can be easily configured. Therefore, according to the present invention that enables the use of a multilayer substrate such as LTCC, an expensive GaAs substrate only needs to be configured with a semiconductor portion (partialization and discrete), and the substrate cost can be greatly reduced. The effect that it becomes possible is acquired.

  First, before describing embodiments according to the present invention, characteristics of a circuit configuration realized by the present invention will be described.

  When configuring an even harmonic mixer, in the conventional planar circuit, configure a filter circuit that allows LO (= fo) signal passage and RF (= 2 * fo) signal short circuit in addition to the short stub on the LO port side. However, it was difficult to realize, and an IF signal had to be taken out from the RF port side. On the other hand, the inventors of the present application have conceived that the waveguide converter, which is essential for the RF signal interface in the ultrahigh frequency band, has a cut-off characteristic (short-circuited from the DC to LO signal frequency band). By using it as it is for IF grounding and LO short-circuiting, a complicated filter circuit is not adopted on the RF port side, and an IF blocking circuit is included on the LO port side that is less susceptible to design restrictions in terms of frequency compared to the RF frequency. By adopting a functional filter circuit, a filter circuit that is less wasteful in terms of manufacturing and circuit performance is constituted by a multilayer circuit.

  As described above, the present invention realizes the above difficult functional filter circuit with a dimension that is not subject to manufacturing restrictions by a multilayer circuit, and also features an even harmonic mixer using the functional filter circuit. Embodiments of a bandpass filter and an even harmonic mixer as functional filter circuits according to the present invention will be described in detail below with reference to the drawings. In addition, this invention is not limited by this embodiment.

  FIG. 1 is a block diagram showing the principle configuration of an even harmonic mixer according to an embodiment of the present invention. The even harmonic mixer shown in FIG. 1 includes an anti-parallel diode pair (hereinafter abbreviated as “APDP”) 10 in which diodes 11 and 12 are connected in parallel with opposite polarities. Further, the HPF unit 17 including the RF port 20 is connected to the connection end 15 on one (left end) side of the APDP 10, and the BPF unit 18 including the LO port 21 is connected to the connection end 16 on the other (right end) side of APDP. The LPF unit 19 including the IF port 22 is connected to each other.

  As shown in FIG. 1, the APDP 10 is configured as a chip on a semiconductor substrate, while other components including the HPF unit 17, the BPF unit 18, and the LPF unit 19 are a multilayer substrate using LTCC (hereinafter referred to as “multilayer substrate”). (Referred to as “LTCC substrate”) and formed and disposed on the top and inside.

  Next, the function of each component constituting the even harmonic mixer shown in FIG. 1 will be described. In the APDP 10, both signals are mixed based on a local oscillation wave signal (hereinafter referred to as “LO signal”) input from the connection end 16 and a high-frequency signal (hereinafter referred to as “RF signal”) input from the connection end 15. As a result, a signal (hereinafter referred to as “IF signal”) representing a component of frequency sum or frequency difference between the two is generated.

Now, if the fundamental frequency of the RF signal, the fundamental frequency of the LO signal, and each frequency of the IF signal are represented by f _RF , f _LO, and f _IF , the relationship of the following equation is established among these frequencies.
f _RF = | f _IF ± 2 · f _LO | (1)

  As shown in Expression (1), the even harmonic mixer can be operated with an LO signal having a frequency that is half that of a normal mixer, and thus is suitable for high-frequency operation such as microwaves and millimeter waves. In addition, since even-order harmonics of the LO signal can be suppressed by APDP, it has a feature that it is low spurious when applied to a transmitter, and an effect of lowering the price can be expected. For this reason, in most published documents including reference documents, even harmonic mixers are often applied to transmitters and receivers using microwaves, particularly millimeter waves.

The even harmonic mixer according to the present invention particularly has a frequency difference between the fundamental component of the RF signal and the second harmonic component of the even harmonic components of the LO signal, as shown in the following formula (2). The main purpose is to extract components as IF signals.
f _IF = | f _RF −2 · f _LO | (2)

  Therefore, the following description is based on the operation of extracting the frequency difference component between the fundamental component of the RF signal and the second harmonic component of the LO signal as an IF signal unless otherwise specified.

  The BPF unit 18 supplies the LO signal input from the LO port 21 to the APDP 10. Further, the BPF unit 18 functions so as to be short-circuited in the RF signal frequency band at the connection end 16 so that the RF signal input from the RF port 20 side is excited by the APDP 10. Further, the RF signal component that may be input to the LO port 21 via the APDP 10 is blocked, and the input of the IF signal component generated by the APDP 10 is blocked. Note that the term “prevention” used here (the same applies to the following explanations) does not have to be a precise meaning such as completely blocking the entry of the corresponding component, and affects the operation of the target circuit. It is used for the purpose of suppressing to less than a practical level.

  The LPF unit 19 extracts the output of the APDP 10 from the IF port 22 as an IF signal and blocks an LO signal component that may be input through the connection end 16. Specifically, the LPF unit 19 functions so as to be open in the LO signal frequency band at the branch end 24 with the BPF unit 18 toward the LPF unit 19. In addition, since the functional part which short-circuits an RF signal component is comprised in the BPF part 18, the connection end 16 turns into a short circuit point with respect to RF signal. Therefore, the intrusion of the RF signal into the LPF unit 19 is prevented not by the function of the LPF unit 19 but by the circuit configuration.

  The HPF unit 17 supplies an RF signal input from the RF port 20 to the APDP 10. Further, the HPF unit 17 further generates an IF generated by the APDP 10 so that the LO signal input from the LO port 21 side is short-circuited in the LO signal frequency band at the connection end 15 so that the LO signal is excited by the APDP 10. It functions to be grounded in DC / low frequency as a reference potential so that the signal can be taken out from the opposite side of the APDP 10. Further, the LO signal component that may be input to the RF port 20 via the APDP 10 is blocked, and the input of the IF signal component generated by the APDP 10 is blocked.

  Next, the operation of the even harmonic mixer shown in FIG. 1 will be described with reference to FIGS. 1, 2-1, and 2-2. 2A is a diagram illustrating an equivalent circuit for the RF signal component viewed from the RF port side, and FIG. 2B is a diagram illustrating an equivalent circuit for the LO signal component viewed from the LO port side.

  First, in FIG. 1, the BPF unit 18 is provided with a functional unit (details will be described later) that short-circuit the RF signal component. Therefore, an equivalent circuit for the RF signal component viewed from the connection end 15 toward the APDP 10 is as shown in FIG. 2A in which the connection end 16 is grounded. As a result, the RF signal applied from the RF port 20 is excited by the APDP 10. If the impedance matching between the APDP 10 side and the HPF unit 17 side is ensured at the connection end 15, the input RF signal is excited at the APDP 10 at the maximum.

  On the other hand, contrary to the above, the HPF unit 17 is provided with a functional unit (details will be described later) serving as a short-circuit point for the LO signal component. Therefore, an equivalent circuit for the LO signal component viewed from the connection end 16 toward the APDP 10 is as shown in FIG. 2-2 in which the connection end 15 is grounded. As a result, the LO signal applied from the LO port 21 is voltage-excited by the APDP 10. Similarly to the case of the RF signal, if the impedance matching between the APDP 10 side and the BPF unit 18 side is ensured at the connection end 16, the input LO signal is excited at the APDP 10. Since the LPF unit 19 is provided with a functional unit (details will be described later) for preventing the LO signal component from passing through, the leakage (wraparound) of the LO signal component to the IF port 22 is suppressed.

  Further, when the RF signal and the LO signal are input to the APDP 10, the IF signal represented by the above equation (1) is generated. Further, the HPF unit 17 is provided with a functional unit (details will be described later) serving as a short-circuit point for the IF signal component, so that the equivalent circuit is as shown in FIG. The connection end 16 is excited as an IF signal voltage. Further, since the BPF unit 18 is provided with a functional unit (details will be described later) that prevents the passage of the IF signal component, the IF signal can be extracted from the IF port 22 through the LPF unit 19.

  Next, a preferred embodiment for implementing the functions of the HPF unit 17, the BPF unit 18, and the LPF unit 19 will be described with reference to FIGS. 1 and 3 to 1 to 5 as appropriate. . Here, FIG. 3-1 is a plan view according to an embodiment that embodies the function of the even harmonic mixer shown in FIG. 1, and FIG. 3-2 is a cross-sectional view taken along line XX in FIG. FIG. 3C is a plan view when the APDP 10 is not placed from FIG. 3A, and FIG. 3D is an inner layer line conductor portion 62 disposed in the inner layer of the multilayer substrate 70. FIG. 3-5 is a main part plan view showing the peripheral part of the ground conductor extraction part 67 formed in the inner layer of the multilayer substrate 70.

  In each of these drawings, the multilayer substrate 70 has a laminated structure in which dielectric substrates 71, 72, 73 and 74 are laminated. This multilayer substrate 70 corresponds to the above-described LTCC. Further, the functional parts of the HPF part 17, the BPF part 18 and the LPF part 19 shown in FIG. The functional units of the HPF unit 17, the BPF unit 18, and the LPF unit 19 correspond to an RF signal demultiplexing circuit 42, an LO signal demultiplexing circuit 43, and an IF output circuit 44 described below. Each of these plan views shows an example of a conductor pattern, but the pattern shape is not limited to this.

  First, the APDP 10 is a semiconductor substrate on which only a minimum circuit such as a semiconductor element portion, a connection / mounting signal, a land pattern such as a GND, and the like is formed, and an upper portion of a dielectric substrate 71 constituting the multilayer substrate 70. Placed in. A terminal on one side of the APDP 10 is connected to a microstrip line (hereinafter referred to as “MSL”) 50 formed on the dielectric substrate 71 via a connection part 45 such as a BGA ball or Au bump, for example. The terminal on the side is connected to a via 81 provided between the dielectric substrate 71 and the dielectric substrate 72 via the connection portion 46. The via 81 is connected to the inner layer line conductor portion 62 formed on the dielectric substrate 72. Although not specifically described above, each of the connection portions 45 and 46 may be provided with a connection pad, a land, or the like on the microstrip line 50 or the via 81 according to the connection means.

(Configuration and function of LO signal demultiplexing circuit)
Next, the configuration and function of the LO signal demultiplexing circuit 43 will be described. On the connection portion 46 side of the APDP 10, a line conductor portion 61 constituting a signal conductor pattern is formed on the upper portion of the dielectric substrate 71. Also, an inner layer line conductor portion 62 that forms a signal conductor pattern in an inner layer between the dielectric substrate 71 and the dielectric substrate 72 is formed below the dielectric substrate 71. The line conductor portion 61 is disposed opposite to the inner layer line conductor portion 62 located below the multilayer substrate stacking direction in an inter-digital structure. In addition, between these line conductors, the length of the overlapping part (the overlapping part when viewed in the vertical direction) is set to about 1/4 of the effective LO signal wavelength (λg / 4 @ LO). Both constitute a laminated inter-digital coupler (hereinafter referred to as “laminated ID coupler”) 60. The stacked ID coupler 60 works to increase the degree of coupling in the frequency band by making the surface layer and the inner layer face each other with a length of λg / 4, and selects only signals in the vicinity of the frequency band. Therefore, it is possible to combine them so as to transmit efficiently. An RF signal frequency band that is twice the frequency or an IF signal generated by the APDP 10 (which is a frequency difference component between the fundamental component of the RF signal and the second harmonic component of the even harmonic components of the LO signal). A signal in a frequency band that is far from the LO signal frequency, such as a frequency band, is blocked.

  Further, below the multilayer ID stacking direction of the multilayer ID coupler 60, between the ground conductor portion 64 formed on the dielectric substrate 73 and the ground conductor portion 66 formed on the dielectric substrate 74, and the ground. Vias 82 are connected between the conductor 66 and the ground conductor 65 formed on the dielectric substrate 73. The vias 82 are arranged, for example, in a rectangular shape at intervals (λg / 4 @ RF) of about 1/4 or less of the effective RF signal wavelength so as to surround the periphery of the ground conductor extraction portion 67 of the dielectric substrate 73. Further, the length of each side of the rectangular portion formed by the plurality of vias 82 is set to approximately ½ of the effective RF signal wavelength (λg / 2 @ RF). Note that the shape in which the via 82 is disposed is not limited to a rectangular shape, and may be arranged in a circular shape having a diameter that is approximately ½ of the effective RF signal wavelength.

  As a result of such a configuration, the surrounding via 82, the ground conductor portion 66 connected to the via 82, and the portion surrounded by the ground conductor removal portion 67 constitute a dielectric resonator 68 in the RF band. The extraction size of the ground conductor extraction portion 67 is substantially the same as the length of each side of the rectangular shape portion formed by the plurality of vias 82 (that is, approximately ½ of the RF signal effective wavelength). It operates as an electrical coupling opening in the frequency band of the signal frequency, and couples the inner layer line conductor 62 and the dielectric resonator 68. When an RF signal is input through the inner layer line conductor 62, the dielectric resonator 68 can short-circuit the RF signal by generating resonance in the fundamental mode in the frequency band. In order to obtain an efficient excitation of the RF signal, it is necessary to realize the short-circuiting of the RF signal at the connection portion 46 of the APDP 10, but the dimensions of the ground conductor removal portion 67 and the dielectric resonator 68 are as follows. Needless to say, it is selected so as to satisfy the above-mentioned conditions including the electrical lengths of the inner layer line conductor 62 and the connection via 81.

  The dielectric resonator 68 has a cut-off dimension for the LO signal passing through the multilayer ID coupler 60 (the minimum dimension for resonance to occur at the LO signal frequency is the LO signal effective). The wavelength needs to be approximately 1/2 or more of the wavelength.) Since it acts as a mere spaced GND as described later, the transmission characteristics of the laminated ID coupler 68 in the LO signal frequency band do not have an adverse effect due to resonance or the like. That is, the laminated ID coupler 60 and the dielectric resonator 68 form the LO signal branching circuit 43. In FIG. 3B, the inner layer line conductor 62 is not conductively connected to either the line conductor portion 61 or the ground conductor portion 65 that is conductively connected to the LO port of the LO signal branching circuit 43. (The APDP 10 and the LO port are isolated in terms of DC and low frequency), so the LO signal demultiplexing circuit 43 is also provided with an IF blocking function. An IF signal is obtained as the mixing output shown.

  In addition, by providing the ground conductor extraction portion 67 immediately below the inner layer line conductor portion 62 of the multilayer ID coupler 60, the lower conductor portion that affects the coupling of the inner layer line conductor portion 62 becomes the ground conductor portion 66. As compared with the case where there is no ground conductor removal portion 67 (that is, the case where the ground conductor portions 64 and 65 are directly below), the distance is increased. As a result, the electrical coupling between the line conductor portion 61 and the inner layer line conductor portion 62 constituting the multilayer ID coupler 60 is strengthened. That is, removing the conductor portion at the top of the dielectric resonator 68 has an effect of increasing the coupling of the stacked ID coupler 60.

(Configuration and function of RF signal demultiplexing circuit)
Next, the configuration and function of the RF signal branching circuit 42 will be described. On the connection portion 45 side of the APDP 10, a transformer 52 and a transformer 53 are connected to the tip of the MSL 50 and to the lower part in the substrate stacking direction. Of these configurations, the transformer 52 includes a via (via that connects the ground conductor 51 to which the tip of a microstrip line (hereinafter referred to as “MSL”) 50 is connected to each ground conductor of the multilayer substrates 71 to 73. Group) 84, vias (via group) 85 connecting the ground conductor portion 64 of the MSL 50 and the upper and lower ground conductors of the multilayer substrate 73, and the ground conductor extraction portion on each multilayer substrate in the substrate stacking direction. It is a dielectric waveguide that transmits a signal.

  The transformer 53 is provided on the dielectric substrate 74, and is connected to the ground conductor portions 81 and 82 connected to the vias 84 and 85, and the via 86 is connected to the ground conductor portions 81 and 82, respectively. , 87 is a dielectric waveguide that transmits an RF signal in the substrate stacking direction. These transformers 52 and 53 operate as an impedance converter that connects the standard waveguide 90 and the MSL 50, and as a result, an RF signal input from the standard waveguide 90 is used as the RF signal branching circuit 42. Efficiently transmit to MSL50. Note that the vias 84 to 87 are arranged at intervals (λg / 4 @ RF) of approximately 1/4 or less of the RF signal effective wavelength, like the vias 82 and 83.

  In the RF signal demultiplexing circuit 42, the dimensions of each constituent circuit (dielectric waveguide) are optimized for the RF signal frequency, and for the LO signal that is approximately ½ the frequency band. Shows the cut-off characteristics. Therefore, the LO signal transmitted from the APDP 10 side through the MSL 50 is totally reflected and short-circuited at any position near the ground conductor portion 64 via the via 84. The length from this short-circuit point to the connection part 45 of the APDP 10 is set to approximately ½ of the LO signal effective wavelength (λg / 2 @ LO). Accordingly, the LO signal is similarly short-circuited in the connection portion 45 of the APDP 10 that is separated by λg / 2 @ LO in a standing wave, and the RF signal branching circuit 42 is connected to the connection portion 45 of the APDP 10. Realize LO short circuit. In addition, with the MSL 50, that is, the configuration in which the signal line is conductively connected to the ground conductor pattern 51, DC and low-frequency signals are also grounded, and the IF short-circuit function is ensured simultaneously with the LO short-circuit function. .

(Configuration and function of IF output circuit)
Finally, the configuration and function of the IF output circuit 44 will be described. In FIG. 3A, a transmission line 57 set to a length (λg / 4 @ LO) approximately ¼ of the LO signal effective wavelength is connected to the connection portion 46 of the APDP 10. Has an effective length that causes a short circuit at the connection portion with the transmission line 57 (for example, in the case of the quadrant shown, it has an electrical length of about λg / 8 to λg / 6). A stub 58 is connected. The radial stub 58 is used for widening the short-circuit characteristic of the LO signal frequency band at the connection point between the transmission line 57 and the radial stub 58, and other ones may be used. Of course. Further, the transmission line 57 and the radial stub 58 may be arranged in the inner layer between the dielectric substrate 71 and the dielectric substrate 72, and according to the input / output interface request of the IF signal, the transmission line on the surface layer (through the through hole ( It is good also as a structure connected with an output line.

  Here, as described above, the radial stub 58 causes a short circuit at the connection portion between the transmission line 57 and the radial stub 58, and the length of the transmission line 57 connected to the connection portion 46 is approximately equal to the LO signal effective wavelength. Since it is set to 1/4, the connection unit 46 is open for the LO signal. In other words, the IF output circuit 44 is not visible to the LO signal from the connection unit 46 (= nothing is connected). Therefore, the IF output circuit 44 has the LO blocking function described above. Further, in this configuration, the RF signal is also short-circuited at the connection unit 46 by the LO signal demultiplexing circuit 43 at the same time, so that the RF signal input to the IF output circuit 44 is provided with a special component inside the IF output circuit 44 It is automatically blocked without

  Next, simulation results of the RF signal demultiplexing circuit 42 and the LO signal demultiplexing circuit 43 of the even harmonic mixer configured as shown in FIGS. 3-1 to 3-5 are shown in FIGS. 4-1 to 5-3. This will be described with reference to the drawings. 4A is a diagram illustrating an example of a simulation result of the transmission / reflection characteristics of the RF signal demultiplexing circuit 42 viewed from the APDP 10 side. FIG. 4B is a diagram illustrating the RF signal demultiplexing circuit 42 from the APDP 10 side. FIG. 4C is a diagram illustrating an example of the simulation result of the normalized impedance at the connection unit 45 when viewing the RF signal branching circuit 42 when viewing the RF signal branching circuit 42 from the APDP 10 side. It is a figure which shows an example of a simulation result. Similarly, FIG. 5A is a diagram illustrating an example of a simulation result of the pass / reflection characteristics of the LO signal demultiplexing circuit 43 viewed from the APDP 10 side, and FIG. 5B is a diagram illustrating an LO signal demultiplexing circuit from the APDP 10 side. FIG. 5C is a diagram illustrating an example of the simulation result of the normalized impedance in the connection unit 46 when viewing the signal 43, and FIG. 5-3 illustrates the reflection phase in the connection unit 46 when viewing the LO signal branching circuit 43 from the APDP 10 side. It is a figure which shows an example of the simulation result.

In FIG. 4A, the curve indicated by the symbol “◯” indicates the pass characteristic of the RF signal demultiplexing circuit 42, and the curve indicated by the symbol “X” indicates the reflection characteristic when the RF signal demultiplexing circuit 42 is viewed from the APDP 10 side. Is shown. From the characteristics shown in the figure, good pass characteristics in the vicinity of the RF signal frequency band (f _RF ≈ 2 · f _LO ) and sufficient attenuation characteristics in the vicinity of the LO signal frequency band (f _LO ) (maximum value of the pass characteristics) It can be understood that an attenuation of 40 dB or more is obtained.

In FIG. 4B, the curve indicated by the symbol “◯” indicates the real part (resistance component) of the normalized impedance when the HPF portion 17 is viewed from the APDP 10 side in the connection portion 15, and the curve indicated by the symbol “X” The imaginary part (reactance component) of the normalized impedance is shown. According to the figure, in the vicinity of the LO signal frequency band (f _LO ), the real part of the normalized impedance is sufficiently small (substantially 0), and the imaginary part is inverted from negative to positive. It can be understood that the LO signal is short-circuited in the part 15.

In FIG. 4C, the reflection phase when the HPF unit 17 is viewed from the APDP 10 side in the connection unit 15 is indicated by a symbol “x”. According to the figure, since the reflection phase is inverted from negative to positive in the vicinity of the frequency band (f _LO ) of the LO signal, the LO signal is short-circuited at the connection 15 as in FIG. I can understand that.

In FIG. 5A, the curve indicated by the symbol “◯” indicates the pass characteristic of the BPF unit 18, and the curve indicated by the symbol “X” indicates the reflection characteristic when the BPF unit 18 is viewed from the APDP 10 side. . From the characteristics shown in the figure, good pass characteristics in the vicinity of the LO signal frequency band (f _LO ) and sufficient attenuation characteristics in the vicinity of the RF signal frequency band (f _RF ≈ 2 · f _LO ) (maximum value of pass characteristics) It can be understood that an attenuation of 30 dB or more is obtained.

In FIG. 5B, the curve indicated by the symbol “◯” indicates the real part (resistance line segment) of the normalized impedance when the BPF portion 18 is viewed from the APDP 10 side at the connection portion 16, and the curve indicated by the symbol “X”. Indicates the imaginary part (reactance line segment) of the normalized impedance. According to the figure, in the vicinity of the RF signal frequency band (f _RF ≈ 2 · f _LO ), the real part of the normalized impedance is sufficiently small (approximately 0), and the imaginary part is inverted from negative to positive. Therefore, it can be understood that the RF signal is short-circuited at the connection portion 16.

In FIG. 5C, the reflection phase when the BPF unit 18 is viewed from the APDP 10 side in the connection unit 16 is indicated by a symbol “x”. According to the figure, in the vicinity of the frequency band (f _RF ≈ 2 · f _LO ) of the RF signal, the reflection phase is inverted from negative to positive. It can be understood that is a short circuit.

  In FIG. 3A, the total reflection characteristics of the dielectric waveguide (transformers 52 and 53) directly connected to the signal conductor of the MSL 50 are used in order to realize the LO short in the connection portion 45 of the APDP 10. The length from the LO short-circuit point formed by this MSL-waveguide converter to the connection portion 45 of the APDP 10 is set to approximately ½ of the LO signal effective wavelength (λg / 2 @ LO). Although configured, for example, as shown in FIG. 6, an open stub 92 having a length substantially ¼ of the LO signal effective wavelength may be provided in the connection portion 45. In this case, since the LO short circuit at the connection portion 45 is realized by the open stub 92, the distance from the connection portion 45 to the MSL-waveguide converter can be arbitrarily set. The length of the microstrip line 50 corresponding to λg / 2 @ LO (that is, one wavelength at the RF frequency) at −1 can be reduced to reduce transmission loss.

  In the above description of the operation, the description will focus on the operation as a reception mixer that inputs an RF signal and an LO signal from the RF port 20 and the LO port 21, respectively, and extracts the mixer signal down-converted by the APDP 10 from the IF port 22. However, the IF port 22 is used as an input circuit to input an IF signal, the LO signal is input from the LO port 21, and the mixer signal upconverted by the APDP 10 is output from the RF port 20. It may be operated as a transmission mixer.

  As described above, according to this embodiment, the planar demultiplexing circuit conventionally formed on the GaAs substrate is applied to the LTCC which has been used mainly for the purpose of electromagnetic shielding / airtightness of the semiconductor chip. As a wave circuit (laminated inter-digital coupler, dielectric resonator, waveguide-MSL converter, etc.) is integrated, expensive GaAs substrates and circuit manufacturing costs are drastically reduced. Can be reduced.

  Further, in this embodiment, desired functions such as RF short circuit, LO short circuit, IF short circuit, and IF blocking are effectively formed in the HPF part, BPF part and LPF part. Larger parallel circuits such as open stubs and short stubs, which were required for harmonic mixers, are no longer necessary, and the circuit scale can be reduced.

  Note that in the conventional even harmonic mixer, the IF output circuit that outputs the IF signal needs to be taken out from the port opposite to the port that grounds the APDP as shown in FIG. In general, a configuration in which a short stub that is short-circuited at a low frequency is connected to the RF port side that is not used. In this embodiment, the IF output circuit is connected to the output of the APDP on the side to which the LO signal branching circuit is connected. It is configured to connect to the end. The above configuration uses a waveguide-MSL converter that is short-circuited (grounded) in a DC manner on the RF port side, and a short stub is not formed on the LO port side. This is because the IF signal needs to be extracted from the circuit, but the true reason is to make the circuit configuration less strict with respect to the manufacturing restrictions of the LTCC. In order to extract the IF signal from the RF port side, a circuit that passes the RF signal and blocks the IF signal by means other than grounding is required. In the conventional MMIC technology, there are many examples that use MIM capacitors. Of course, in the present LTCC technology, it is difficult to realize a bypass capacitor in a high frequency band. For example, if it is attempted to use a laminated inter-digital coupler or the like used on the LO port side in this embodiment on the RF port side, it will be affected by the manufacturing accuracy of LTCC. That is, since the manufacturing accuracy required for a high-frequency circuit is generally proportional to the length of the wavelength, the laminated inter-digital coupler is configured on the LO port side (the connection end of the IF output circuit is connected to the LO signal branching circuit). The manufacturing accuracy required to obtain the desired performance can be reduced to half that of the configuration on the RF port side, and the manufacturing cost and time can be shortened. It becomes.

  In addition, the above circuit configuration eliminates the need for a DC / low frequency cut circuit conventionally required on the RF port side, so that it is possible to reduce the RF signal passing loss, which is the most important as mixer performance, regardless of whether it is used for transmission or reception.

  In this embodiment, the case where the multilayer ID coupler, the microstrip-waveguide converter, and the IF output circuit are configured by microstrip lines formed on the surface layer of the multilayer dielectric substrate has been described as an example. However, as shown in FIGS. 3-1 to 3-5, each circuit does not need to be configured by a surface transmission line, and a transmission line formed inside a multilayer substrate may be used. Further, as a multilayer substrate other than LTCC, an HTCC (high temperature fired substrate) or a build-up substrate may be used.

  As described above, the even harmonic mixer and the demultiplexing circuit according to the present invention are useful for a wireless communication system, a transmission / reception device of a radar system, and the like, and are suitable for cost reduction of these devices.

It is a block diagram which shows the principle structure of the even harmonic mixer concerning embodiment of this invention. It is a figure which shows the equivalent circuit with respect to the RF signal component seen from the RF port side. It is a figure which shows the equivalent circuit with respect to LO signal component seen from the LO port side. It is a top view concerning one Embodiment which embodies the function of the even harmonic mixer shown in FIG. It is arrow XX sectional drawing in FIG. It is a top view in case APDP is not mounted from FIGS. It is a principal part top view which shows the peripheral part of the inner-layer ground conductor part arrange | positioned at the inner layer of a multilayer substrate. It is a principal part top view which shows the peripheral part of the ground conductor extraction part formed in the inner layer of a multilayer substrate. It is a figure which shows an example of the simulation result of the passage and reflection characteristic in RF port. It is a figure which shows an example of the simulation result of the normalization impedance in RF port. It is a figure which shows an example of the simulation result of the reflection phase in RF port. It is a figure which shows an example of the simulation result of the passage and reflection characteristic in a LO port. It is a figure which shows an example of the simulation result of the normalized impedance in a LO port. It is a figure which shows an example of the simulation result of the reflection phase in LO port. It is a top view which shows the other embodiment which implement | achieves the function of an even harmonic mixer.

Explanation of symbols

11, 12 Diodes 15 and 16 Connection end 17 HPF section 18 BPF section 19 LPF section 20 RF port 21 LO port 22 IF port 24 Branch end 42 RF signal branching circuit 43 LO signal branching circuit 44 IF output circuits 45 and 46 Connection 50 MSL (microstrip line)
51 Ground conductor (ground conductor pattern)
52, 53 Transformer 57 Transmission line 58 Radial stub 60 Multilayer ID coupler 61, 62 Line conductor (signal conductor)
64 Ground conductor (ground conductor)
65, 66, 81, 82 Ground conductor portion 67 Ground conductor removal portion 68 Dielectric resonator 70 Multilayer substrate 71, 73 Dielectric substrate (multilayer substrate)
72, 74 Dielectric substrate 83, 84, 85, 86, 87 Via 90 Standard waveguide 92 Open stub

Claims (10)

An anti-parallel diode pair in which two diodes of different polarities are connected in parallel;
Connected to one end of the anti-parallel diode pair to allow the passage of RF signals while blocking the passage of LO and IF signals, and at the connection end to the anti-parallel diode pair A high-pass filter in which the signal and the IF signal are short-circuited;
A band-pass filter connected to the other end of the anti-parallel diode pair for inputting the LO signal;
A low-pass filter that is connected in parallel to the other end of the anti-parallel diode pair, blocks the passage of the LO signal, and outputs an IF signal generated based on the LO signal and the RF signal;
In the even harmonic mixer with
The bandpass filter is
A multilayer inter-digital coupler in which one signal conductor and the other signal conductor are arranged so as to face each other in the multilayer substrate stacking direction between predetermined layers constituting the multilayer substrate;
The layered inter-digital coupler is disposed below the multilayer inter-digital coupler, and has a ground conductor extraction portion that is electrically coupled to the multilayer inter-digital coupler , and the stack is formed from the other end of the anti-parallel diode pair. A dielectric resonator that resonates with an RF signal input via an inter-digital coupler;
An even harmonic mixer characterized by comprising. The high-pass filter is
A planar transmission line connected to one end of the anti-parallel diode pair;
A waveguide for inputting and outputting RF signals;
A part of the conductor constituting the waveguide is conductively connected to the signal conductor of the planar transmission line, and the transmission line conversion between the waveguide and the planar transmission line is selectively performed only for an RF signal. A planar transmission line / waveguide converter that performs and blocks the passage of LO and IF signals;
The even harmonic mixer according to claim 1, further comprising: The high-pass filter is
3. The open-ended stub connected in parallel to the connection end of the anti-parallel diode pair and having a length of ¼ of the effective LO signal wavelength . 4. Even harmonic mixer. And wherein the length of the portion overlapping each other in a layered substrate lamination direction of the upper layer signal conductor and the lower signal conductor forming the laminated inter-digital coupler is set to 1/4 of the LO signal effective wavelength The even harmonic mixer according to any one of claims 1 to 3. The resonant length of the dielectric resonator, even harmonic mixer according to any one of claims 1 to 4, characterized in that it is set to 1/2 of the RF signal effective wavelength. The length of the disposed below the stacked inter-digital coupler the ground conductor vent portion, even harmonic of claim 5, characterized in that it is set to 1/2 of the RF signal effective wavelength Mixa. The electrical wall in the multilayer substrate stacking direction forming the dielectric resonator is composed of a plurality of vias, and the plurality of vias are arranged at intervals equal to or less than ¼ of the effective RF signal wavelength. The even harmonic mixer according to claim 5. In a band-pass filter that filters the first signal from each of the first signal having a reference frequency, the second signal having a frequency twice that of the first signal, and the low-frequency signal near DC,
A laminated structure configured such that one signal conductor and the other signal conductor are arranged to face each other between the upper and lower sides in the multilayer board laminating direction between predetermined layers constituting the multilayer board so as to obtain coupling with the first signal. An inter-digital coupler;
The ground inter-digital coupler is disposed below the stacked inter-digital coupler and has a ground conductor extraction portion electrically coupled to the stacked inter-digital coupler, and is input via the stacked inter-digital coupler. A dielectric resonator that resonates with the second signal;
A band-pass filter comprising: The length of the overlapping portion of the upper layer signal conductor and the lower layer signal conductor constituting the multilayer inter-digital coupler in the multilayer substrate stacking direction is set to ¼ of the effective wavelength of the first signal. The band-pass filter according to claim 8. The bandpass filter according to claim 8 or 9, wherein a resonance length of the dielectric resonator is set to ½ of an effective wavelength of the second signal.

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