JPH03187626A - Transmission line length determination method for common use device - Google Patents

Abstract

PURPOSE:To minimize the insertion loss of a common use device by applying repetitive calculation based on a specific equation so as to obtain an optimum transmission line length. CONSTITUTION:Lengths Lt, Lr of the sender and the receiver side of transmission lines 15a, 15b and impedances Zt, Zr of filters 16, 17 at the sender and receiver sides are revised based on equations I, II and the lengths Lt, Lr of the transmission lines are calculated repetitively till they are converged to a prescribed accuracy, then an optimum transmission line length is obtained, which minimizes both the insertion losses Tt, Tr at the sender side and the receiver side simultaneously. In the equations I, II, At-Dt are elements of a combined cascade matrix comprising a receiver side transmission line 15b and a transmission filter 16, Ar-Dr are elements of a combined cascade matrix comprising a sender side transmission line 15a and a transmission filter 17, and Z0 is the characteristic impedance of the measuring system. Thus, the transmission line length at the sender side and the receiver side is decided optimizingly to minimize the insertion loss of a common use device.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for transmitting and receiving transmission signals and reception signals using the same antenna, etc. in a car telephone device, etc. that uses frequencies from the VHF band to the UHF band, etc. The present invention relates to a duplexer, and particularly to a method for determining the transmission path length of a duplexer to obtain good frequency characteristics with a small size.

(Prior Art) Generally, a duplexer is composed of a branching circuit, a transmission filter, and a reception filter, and has a function of transmitting and receiving a transmission signal and a reception signal through a common terminal.

Conventionally, in order to obtain a high-performance duplexer, it has been necessary to improve filter loss, reduce resistance loss in the duplexer circuit, and reduce the duplexer.
Various proposals have been made. In particular, with the miniaturization of communication devices, it has become essential to realize a compact and high-performance duplexer. An example of a conventional common duplexer is shown in FIG.

FIG. 2 is a block diagram of a conventional common duplexer.

This shared device has a substrate 1 made of glass epoxy or the like, and a common terminal 2, an input terminal 3, and an output terminal 4 are provided on the substrate 1. Common terminal 2 has
One end of the branching circuit pattern 5 is connected, and the other end of the branching circuit pattern 5 is connected to the transmission filter 6 and the reception filter 7.
are connected to the input terminal 3 and the output terminal 4 via the respective terminals.

The branching circuit pattern 5 is a transmitting side transmission line 5 with a transmission line length Lt.
a, and a receiving side transmission line 5b having a transmission line length Lr.

The transmission path lengths Lt and Lr on the transmitting side and receiving side from the transmitting filter 6 and receiving filter 7 to the common terminal 2 are such that the impedance of each transmitting filter 6 and receiving filter 7 as seen from the common terminal 2 is the same as that of the other side due to the impedance conversion effect. It is designed to have a maximum at the center frequency of . That is, at the transmission frequency Ft, the impedance of the transmission filter 6 viewed from the common terminal 2 is approximately equal to the characteristic impedance Z○ defined for this type of circuit, but the impedance of the reception filter 7 is maximum.

At the reception frequency Fr, the impedance of the reception filter 7 is approximately equal to the characteristic impedance ZO of the measurement system for impedance measurement connected to the output terminal 4, for example, but the impedance of the transmission filter 6 is maximum. In fact, it is ideal that the impedance of each of the transmission filter 6 and the reception filter 7 becomes infinite at the center frequency Ft or Fr of the other party.

This is because the greater the impedance of each of the transmission filter 6 and the reception filter 7, the smaller the demultiplexing loss becomes, and when it reaches infinity, the demultiplexing loss completely disappears. However, it is impossible to make each impedance infinitely large, so in reality, efforts are made to maximize each impedance.

In this type of duplexer, when a received signal from an antenna or the like is input to the common terminal 2, the received signal passes through the receiving side transmission path 5b, is filtered by the receiving filter 7, and is outputted from the output terminal 4 to the receiving circuit, etc. sent to. Furthermore, when a transmission signal from a transmission circuit or the like is input to the input terminal 3, the transmission signal is filtered by a transmission filter 6, and then filtered by a transmission line 5 on the transmission side.
a, is output from the common terminal 2, and sent to an antenna or the like.

(Problems to be Solved by the Invention) However, the duplexer having the above configuration has the following problems.

In the conventional technology, the transmission path lengths Lt and L on the transmitting side and the receiving side are set so that the respective absolute values of the equivalent impedance on the transmitting side and the equivalent impedance on the receiving side viewed from the common terminal 2 are maximized.
The duplexer is designed by calculating r. This design method will be referred to as the maximum impedance design method. Analyzing the insertion loss on the transmitting side and receiving side of a duplexer designed using such a maximum impedance design method, it is found that due to the characteristics of the maximum impedance design method, the insertion loss on the transmitting side and receiving side can be minimized. It was impossible to do so.

In other words, if the transmission path lengths Lt and Lr on the transmitting and receiving sides are properly selected, the insertion loss of the duplexer can be minimized, but since the maximum impedance design method is used, the optimum transmission path length cannot be determined. It is difficult to determine t and Lr. Minimizing insertion loss is an important issue in shared dense design, but this is not possible using conventional maximum impedance design methods.

The present invention solves the problem of the prior art in that it is difficult to optimally determine the transmission path length on the transmitting side and the receiving side to minimize the insertion loss of the duplexer. This provides a path length determination method.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a transmitting side transmission line with a transmission line length Lt, one end of which is connected to a common terminal, and a transmission line with a transmission line length Lt.
a branching circuit pattern for transmitting and receiving signals having r receiving side transmission lines; a transmitting filter for the transmitting signal filtering phase connected to the other end of the transmitting side transmission line; The reception filter for the reception signal filtering phase connected to the other end is a duplexer provided on the board, and the transmission path lengths on the transmission side and reception side are determined as follows.

That is, based on a certain insertion loss calculation formula, the transmission path lengths Lt and Lr are set so that the absolute values of the transmission filter insertion loss Tt and the reception filter insertion loss Tr are always the minimum.
Impedance Zt on the transmission filter side viewed from the common terminal
and the impedance Zr on the reception filter side are updated by induction, and the optimum transmission path length is determined by performing iterative calculations until the transmission path lengths Lt and Lr converge to a predetermined accuracy.

(Operation) According to the present invention, since the method for determining the transmission path length in the duplexer is configured as described above, the transmission path lengths Lt and Lr on the transmitting side and the receiving side are determined based on a certain insertion loss calculation method. By updating impedances Zt and Zr of the filters on the receiving side and repeating calculations until the transmission path lengths Lt and Lr converge to a predetermined accuracy, the insertion loss T on the transmitting side and the receiving side is
An optimal transmission path length can be obtained in which both t and Tr are simultaneously at their minimum values. Therefore, the above problem can be solved.

(Example) Figures 3 (a>, (b), and (c) are explanatory diagrams of the configuration of a duplexer showing an example of the present invention, where (a) is a circuit diagram, and (b) is a circuit diagram. is an equivalent circuit diagram at the transmission frequency Ft, and (C) is an equivalent circuit diagram at the reception frequency Fr.

As shown in FIG. 3(a), like the conventional device shown in FIG. 2, this duplexer has a board (not shown), and a common terminal 12, an input terminal 13, and an output terminal 14 are provided on the board. It is being One end of the branching circuit pattern 5 is connected to the common terminal 12, and the other end of the branching circuit pattern 5 is connected to the input terminal 1 via the transmission filter 16 and the reception filter 17.
3 and output terminal (4), respectively.

The transmission filter 16 and the reception filter 17 are configured with, for example, surface acoustic wave filters. In particular, when a surface acoustic wave filter is used, this surface acoustic wave filter is small and stable against changes in temperature and aging, and has the characteristics that the amplitude characteristics and phase characteristics can be designed almost independently and arbitrarily. are doing.

The branching circuit pattern #5 has a transmission path length Lt as in the conventional case.
A transmitting side transmission line 15a of , and a receiving side transmission I of transmission line length Lr.
It consists of ¥815b. The input terminal (3 and output terminal 14 each have a terminal impedance of 18.19
is connected. Generally, this terminal impedance 18.19 has the same value as the characteristic impedance ZO of the measurement system for measuring impedance.

The duplexer shown in FIG. 3(a) has the same configuration as the conventional duplexer, and the difference between this embodiment and the conventional duplexer is the method of determining the transmission path lengths Lt and Lr on the transmitting side and the receiving side. .

In the equivalent circuit of FIG. 3(b), Zt is the common terminal 12
The equivalent impedance Zr, 16a on the receiving side viewed from the transmission line 16a is a tandem array [T] that is a combination of the transmission line 15a on the transmitting side and the transmission filter 16.

Similarly, in the equivalent circuit of FIG. 3(c), 20 is the equivalent impedance Zt. on the transmitting side viewed from the common terminal 12. 1
7a is a cascaded row array [R] which is a combination of the receiving side transmission line 15b and the receiving filter 17.

The vertical columns [T] and [R are shown in equations (1) and (2). (
At, Bt, Ct, Dt> and (Ar, Br, Cr, Dr
) are components of [T and [R], respectively, and are complex numbers.

The insertion losses Tt and Tr on the transmitting side and receiving side of the duplexer are calculated from the cascade arrays [T] and [R] as shown in the following equations (3) and (4).

rt=v+”i=0.5(A t 10B t/ZO+CtZO+Dt)
+0.5(At+Bt/ZO)/Zr = (3)T
r=0.5(Ar+Br/ZO+CrZO+Dr)+0
．． 5(Ar+Br/zO)/zt H+ (4)V=
0.5 (At+Bt/ZO+CtZO+Dt)...
...(3-1) 'i=0.5(At+Bt/20)/Zr...
(3-2) However, zO: Characteristic impedance insertion loss Tt of the measurement system
The absolute values of and Tr are the transmission path lengths Lt and L on the sending and receiving sides.
By changing r, both can be minimized at the same time. This length will be called the optimal transmission path length, and the design method based on this will be called the optimal design method.

In the conventional method, the duplexer is designed by calculating the transmission path lengths t and Lr on the transmitting and receiving sides so as to maximize the absolute values of the equivalent impedance Zr on the receiving side and the equivalent impedance Zt on the transmitting side (maximum On the other hand, in this example, the optimal transmission path length is determined using the optimal design method.However, in the case of the optimal transmission path length, the general function equation is Since this has not been established, it is difficult to obtain it analytically, similar to the conventional maximum impedance design method.

Therefore, in this embodiment, the optimal transmission path length is calculated numerically by an electronic computer or the like using the induction method shown in FIGS. 1(a) and 1(b).

Before explaining this induction method, the difference between the maximum impedance design method and the optimal design method will be explained geometrically using insertion loss Tt (or Tr) with reference to FIG.

FIG. 4 is an explanatory diagram of the maximum impedance design method and the optimal design method, with the real part r plotted on the horizontal axis and the imaginary part X plotted on the vertical axis.

At the transmission frequency Ft, the receiving side impedance Zr seen from the common terminal 12 is a complex number, and when the receiving side transmission path length Lr is changed, the radius RO1 center ω0 (rO, xo ) draw a circle (Co). The receiving side impedance Zr can be expressed as follows.

Zr=r+jx ・・・・・・(5〉 Admittance 1 / Z r is also on the circumference of the circle (Co) like impedance Zr, but they are symmetrical to each other around ω0. Point M is impedance Zr The point MO indicates the admittance L/Z r at that time.The value of the radius RO and the coordinates of the center ω0 are as follows.

RO=IO,5(Z○2/r-r)l-(6
) ωO: (rOl xO>・・・・・・(7> ro=0.5(Z02/r+r) ・・・・・・(7-a> xO=0 ・・・・・・(7-b ) From formula (3> and formula (3-2>), the locus of W has radius R1,
It is a circle (C1) with center ωl (rl, xi). point MO
moves to Ml. The value of radius R1 and the coordinates of center ω1 are as follows.

R1= 0.5 (At+Bt/ZO) R.O. ・・・・・・(8) ωl: <rl.

xi> ......(9) rl-real part (0,5(At+Bt/ZO)ro)...
...(9-a) xi-imaginary part (0,5(At+Bt/20)rO)...
(9-b) From equation (3) and the circle (C1), the locus of the insertion loss Tt is a circle (C2) with radius R2=R1 and center ω2 (r2.x2). At that time, point M1 moves to point M2. The coordinates of the center ω2 are as follows.

ω2: (r2゜x2) ・・・・・・(10) r2=rl+real part(0,5(At+Bt/ZO×CtZ
O+Dt)) -(10-a)x2=x1+imaginary part(0
,5(At+Bt/ZO1CtZO+Dt)) ・Song-
(1o-b> As is clear from the above explanation, insertion loss T
The absolute value of t is equal to the line segment connecting the origin 0 (0, O) of the coordinate system of the complex plane shown in FIG. 4 and a point N on the circumference of the circle (C2). When the receiving side transmission path length Lr is changed, the point N moves on the circumference of the circle (C2), and naturally the absolute value of the insertion loss Tt also changes.

The straight line connecting the origin 0 (0, O) and (JJ2 (r2. (C
2), and when it overlaps with point Mb, the insertion loss T
When the absolute value of t becomes maximum and overlaps with point Ma, the absolute value of insertion loss Tt becomes minimum. Obtaining Lr so that point N overlaps with point Ma is a feature of the optimal design method, and the insertion loss T
Make sure that the absolute value of t is always the minimum. On the other hand, when point N overlaps point M2, the absolute value of the transmission side insertion loss Tt of the duplexer designed by the maximum impedance design method is obtained.

Since the point Ma is generally different from the point M2, the insertion loss of the duplexer designed by the optimal design method is clearly smaller than the insertion loss of the duplexer designed by the maximum impedance design method.

Therefore, by using the optimal design method, the insertion loss of the duplexer can be minimized.

Figures 1 (a> and (b) are flowcharts of the induction method for calculating the optimal transmission path length, and with reference to this figure, the method for determining the optimal transmission path length using a computer etc. will be explained. .

In step 20, the transmission path length Lt between the transmitting side and the receiving side
The initial values of and Lr are set to LtO=O and Lr0=O. At this time, the vertical rows are [TO] = [T] and [RO] =
[R], the insertion loss is TtO, and the impedance of the transmission filter 6 and the impedance of the reception filter 17 seen from the common terminal 12 of the TrO1 are ZtO and ZrO.

First, in step Zt, the method using equations (1) to (10-b) as described above at the transmission frequency Ft,
A tentative optimal transmission path length Lrl on the receiving side is determined, and the minimum insertion loss on the transmitting side at that time is set as Ttl. In step 22, [R1] and Zrl are obtained from the optimal transmission path length Lrl and the cascade array [RO], and in step 23, the receiving frequency F
At r, the tentative optimum transmission path length Ltl on the transmitting side and the minimum insertion loss Tri on the receiving side can be determined using the cascade array [R1] and the impedance ZtO. Further step 2
4, the optimal transmission path length Ltl and the tandem array [TO] are [Tt
l and Zt1 are obtained, and in step 25, the transmission frequency Ft
, the cascade array [T 1 ] and the impedance Zrl
A new provisional optimal transmission path length Lr2 on the receiving side and a new minimum insertion loss Tt2 on the transmitting side can be obtained using the following equations.

Similarly, [R2] and Zr2 are obtained from the optimum transmission path length Lr2 and the cascade array [TO] via the connector ① at step 26, and at step 27, the cascade array [R2] and the impedance Ztl are obtained at the reception frequency Fr. The new temporary optimal transmission path length Lt2 on the transmitting side and the new minimum insertion loss T on the receiving side are
r2 can be found.

In step 28, in order to determine whether the optimum transmission path lengths Lr2 and Lr2 can be used as the optimum transmission path lengths on the transmitting side and the receiving side,
Find the difference in r2, and decide whether the value of these differences is smaller than the desired accuracy N (for example, 10-6>). If the condition is met, in step 2, Lr2 and Lr2 are determined to be the optimal transmission path length. If it is determined that there is, and the calculation is terminated, but the condition is not satisfied, in step 30, Ltl=Lt2, L
Set r1=Lr2 and Zr1=Zr2, and return to step 24 via connector (2) to repeat the above-mentioned iterative calculation.

When such calculations are repeated, the transmission path lengths on the transmitting side and the receiving side converge to certain values Ltn and Lrn, which are the optimum transmission path lengths to be found. The insertion loss at this time is also the optimum value Ttn
and becomes Trn.

Optimum transmission path lengths such as Ltn and Lrn may be calculated analytically in the future if general functional formulas are established, but within the current practical scope, this example The calculation accuracy can be said to be the best method.

Next, the effects of this embodiment will be explained with reference to FIGS. 5(a>, (b), and (c)).

FIGS. 5(a) to 5(c) are insertion loss characteristic and reflection loss characteristic diagrams of a conventional duplexer and a duplexer of this embodiment in which the transmitting filter and the receiving filter are configured using surface acoustic wave filters.

Among them, FIG. 5(a) shows the insertion loss characteristics and reflection loss characteristics of a duplexer designed using the conventional maximum impedance design method. TT-1 and TR-↓ are insertion loss characteristics on the transmitting side and receiving side, respectively. TL-1 is common terminal 12
This is the reflection loss characteristic from the perspective of The transmission path lengths on the transmitting side and receiving side are 0.2782Xλr and 0.2028xλ, respectively.
It is t.

FIG. 5(b) shows the insertion loss characteristics of the duplexer designed by the optimal design method of this embodiment. In order to confirm the effects of the conventional design method and the design method of this embodiment, the transmitting filter 16 and the receiving filter 17 were constructed using the same surface acoustic wave filters as the conventional method. In this case as well, TT
-2 and TR-2 are insertion loss characteristics on the transmitting side and receiving side, respectively, and TL-2 is a return loss characteristic viewed from the common terminal 12. The transmission path length on the sending and receiving sides is 0°245 each.
2Xλr and 0.1872Xλt. λt and λr are the transmission wavelength and reception wavelength.

Figure 5(C) is an enlarged version of the insertion loss characteristics in Figures 5(a) and 5(b) drawn on the same coordinates in order to facilitate comparison between the conventional method and this embodiment. It is. TT-1,T
T-2, TR-1, and TR-2 are the same as in Figure 5 (a>, (b). Comparing TT-1 and TT-2 and TR-1 and TR-2, At the center frequencies of each passband, 835, OMHz and 880, OMHz,
It can be seen that the insertion loss of the duplexer of this example is smaller than the insertion loss of the duplexer designed using the conventional method. Therefore, in the method of this embodiment, the insertion loss can be made smaller than in the conventional method, thereby making it possible to reduce the amount of signal attenuation of the duplexer.

(Effects of the Invention) As described above in detail, according to the present invention, the insertion loss Tt of the transmission filter and the reception filter.

The transmission path length Lt from the common terminal to the transmission filter and reception filter is set so that Tr is simultaneously minimized.

Since Lr is calculated using a calculation method using the induction method to find the optimal transmission path length, it is possible to minimize the insertion loss of the transmitting filter and receiving filter, thereby achieving a small size and a good frequency. It is possible to provide a duplexer with special characteristics.

[Brief explanation of drawings]

Figures (a) and (b) show an embodiment of the present invention, and are flowcharts of the induction method for calculating the optimal transmission path length;
Figure 2 shows the constituent countries of the conventional shared device, Figure 3 (a>, (b))
, (c) are configuration explanatory diagrams of a duplexer showing an embodiment of the present invention, (a) is a circuit diagram, and (b) is a diagram showing the transmission frequency F.
The equivalent circuit diagram at t and the same figure (c) are the receiving frequency F
Fig. 4 is an explanatory diagram of the maximum impedance design method and optimal design method, Fig. 5 (a), (b) (c
) is an insertion loss characteristic diagram of a duplexer designed for comparison between the conventional and this embodiment, (a) is an insertion loss characteristic diagram of a duplexer designed by the maximum impedance design method, and (b) is The insertion loss characteristic diagram of the duplexer designed by the optimal design method, and the same figure (C) is a comparison diagram of the insertion loss. 12... Common terminal, 13... Input terminal, 14... Output terminal, 15... Branching circuit pattern, 15a... Transmitting side Transmission line, 15b・
. . . Reception side transmission line, Engineering 6 . . . Transmission filter, 17 . . . Reception filter. (a) Flowchart of the embodiment of the small invention Fig. 1 (6) Fig. 12; Rokutsu Mizuko 13: Input terminal 14'-output terminal 15: Branching circuit pattern Duplexer of the embodiment of the small invention Fig. 3 Transmission frequency ``t'' (115 equivalent circuit <-er) Reception frequency ``equivalent circuit at r (C) Figure 3 Frequency (Hz) Boooo 850.0 Round 5 skin loss (MHz) 9ωO Pushing loss Comparison (C) Figure 5 Procedural Amendment Method for Determining Transmission Path Length for Dual Unit Representative Nobumitsu Kosugi The "Detailed Description of the Invention" column of the specification subject to the amendment and the drawings. (1) Book M, page 13, line 12 to page 14, line 7, “
Figure 4 is as follows. ” is corrected as follows. "Figure 4 is an explanatory diagram of the maximum impedance design method and the optimal design method, with the real part on the horizontal axis and the imaginary part on the vertical axis. At the transmission frequency Ft, the receiving side as seen from the common terminal 12 The impedance Zr is a complex number, and when the receiving side transmission path length Lr is changed, a circle (CO) with a radius RO1 and a center ω0 (rO, xo) is drawn on the complex number plane as shown in Fig. 4.The receiving side impedance Zr can be expressed as the following formula: Zr = Rr + j Point M indicates the position where impedance Zr is maximum, and point MO indicates the admittance 1 at that time.
/Zr is shown. If the coordinates of point M are (r, 0), point M
The coordinates of O are (Z02/r, O). The value of the radius RO and the coordinates of the center ωO are as follows. (2) Figure 4 is corrected as shown in the attached sheet.

Claims (1)

[Scope of Claims] A branching circuit pattern for branching transmitting and receiving signals having a transmitting side transmission line having a transmission line length Lt and a receiving side transmission line having a transmission line length Lr, one end of which is connected to a common terminal; A duplexer including a transmission filter for filtering a transmission signal connected to the other end of the transmission line on the transmission side and a reception filter for filtering the reception signal connected to the other end of the transmission line on the reception side, provided on a substrate. In, based on the following formula, the transmission path lengths Lt and Lr and the transmission path length as seen from the common terminal are set such that the absolute values of the insertion loss Tt of the transmission filter and the insertion loss Tr of the reception filter are always minimum. While updating the impedance Zt on the filter side and the impedance Zr on the receiving filter side by induction, iterative calculation is performed until the transmission path lengths Lt and Lr converge to a predetermined accuracy to obtain the optimal transmission path length. A method for determining the transmission path length of a duplexer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, At, Bt, Ct, Dt: These are components of the tandem sequence [T] that is a combination of the receiving side transmission path and the transmitting filter, and are complex numbers. Ar, Br, Cr, Dr: Components of a cascade sequence [R] that is a combination of the transmitting side transmission path and the receiving filter, and are complex numbers. ZO: Characteristic impedance of the measurement system