JPS5922401B2 - N-way separate power divider - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention is a decoupled power divider, particularly for high frequency, e.g.
It relates to power dividers designed for use with electrical signals at frequencies above Hz.

In various high frequency systems, it is often desired to split a high frequency signal on one transmission line into an equal number of substantially identical signals on multiple transmission lines.

This type of signal splitting is desired to supply a portion of the original signal to a large number of individual antenna units of a power amplifier system, such as where it is desired to drive a large number of solid-state amplifiers with the same signal. or in a cable transmission system where the original signal is fed onto a selected number of cables.

Among the various devices that provide power division are "hybrid junctions," directional couplers, and both separate and active power dividers.

A directional coupler transfers power from an input port to a pair of output ports.
It is commonly used at microwave frequencies to provide a selective power ratio called the coupling ratio.

The coupler has a further port, which is usually terminated and is referred to as a "separate" port.

This is because the signal applied to that input port is not coupled to this isolated port.

All ports of the directional coupler are impedance matched with their corresponding transmission lines.

The outputs of the directional coupler are also separated from each other, i.e. a signal supplied to one output does not appear at the other output, but both its input and the isolated appears in

The directional couplers described above inherently have two disadvantages for use in many power divider applications.

The first is that only two-way power division is provided, so multi-way power division requires many combiners.

Second, the signals at the output of this directional coupler have a quadrature relationship, and phase correction becomes necessary if it is desired to have output signals in phase.

A hybrid junction is similar to a directional coupler in that the two outputs are impedance matched and isolated from each other.

Hybrid junctions are different because their output signals are identical in both amplitude and phase.

Therefore, the hybrid junction is limited to binary power division and is similar to the above directional coupler having only two outputs.

A power divider has one input and two or more outputs.

There are two common types of power dividers, commonly known as "reactive power dividers" and "separate power dividers."

A reactive power divider typically has one input and a set of N outputs.

Each of the output ports is connected to the input port by a quarter-wavelength transmission line selected to have an impedance to match the input port to the total output impedance of the N output ports. ing.

The reactive power divider does not have matched or separate outputs.

When a signal is applied to only one of the output ports, a portion of the signal is reflected and a portion of this signal appears at each of the other output ports and the input port.

The device will match the signal applied to the output port only under conditions such that signals of equal amplitude and phase are simultaneously applied across the length of the output port.

The isolated power divider overcomes the drawbacks of the reactive power divider by providing resistive terminal connections for unequal signals provided to the outputs.

These terminal connections perform the same function as separate outputs in a directional coupler or hybrid junction and allow impedance matching and isolation of the outputs.

In known power dividers, the resistive terminal connections are typically in the form of a "star connected" resistor at the output, as described below.

These resistors are typically unable to dissipate high average power without overheating, and because of the star-connected configuration, these resistors have a high thermal conductivity for use with high average power signals. cannot be conveniently attached to a "heat sink".

Additionally, star connected resistors within this high frequency power divider often must be mounted close together, thereby creating additional overheating problems in high power systems.

DESCRIPTION OF FIGS. 1 and 2 (Prior Art) FIG. 1 shows a separate power divider made in accordance with the prior art.

In one example, the power divider in Figure 1 utilizes microstrip transmission lines, but this type of power divider may also be used to connect other types of transmission lines, including triple-plate stripline or coaxial cable. It is well known that it can be made using

The power divider shown in FIG. 1 above consists of an insulator substrate 10
by attaching a printed circuit to one side of the

The other side of the insulator substrate is coated with a conductive material to form a ground plane.

The power divider of FIG. 1 includes an input port 11 consisting of first and second input terminals.

The first input terminal is a circular metal spot deposited on the substrate as seen in FIG. 1, and the second input terminal is on the opposite side of the substrate 10 not shown in FIG. is a conductive ground plane located at

Connection to this type of terminal is usually facilitated by the use of a coaxial connector mounted on the side of the substrate 10 that has a conductive ground plane.

The outer conductor of the coaxial connector is connected to this ground plane, while the inner conductor is read directly to the input terminal 11 shown in FIG.

The power divider of FIG. 1 also has output ports 13a, 13b and 13c of the same type as the input ports, and
It has first and second output terminals similar to the terminals of.

Output ports 13a, 13b and 13c are transmission line 12a
, 12b and 12e are connected to the input port 11.

Transmission line 12 is a first metal strip deposited on substrate 10 as shown in FIG.
conductor and a second conductor consisting of a conductive ground plane on the opposite side of the substrate 10.

Transmission lines 12a, 12b and 12c are selected to be one quarter wavelength of a selected frequency within the operating band of the power divider of FIG.

The impedance of these transmission lines 12 is 1 between the total impedance of the output ports 13a, 13b and 13c and the impedance of the input port 11.
/4 wavelength transformer.

The transmission line 12 operates as a transformer selected to have a length that is an odd integer multiple of a quarter wavelength; however, it tends to operate over a relatively narrow frequency band. It will be clear to those skilled in the art that it also operates as a transformer.

In addition to acting as an impedance transformer, the odd quarter wavelength transmission line 12 results in
1 for the signal coupled between the output ports 13, the electrical length is an odd number of half wavelengths.

In this way, the signals combined by this path are
It is out of phase with the signal coupled directly between the outputs 13 by the star connected resistor 14, as will be explained below.

This results in separation between the output ports as these signals tend to cancel.

To provide isolation between outputs 13a, 13b and 13c, the power divider of FIG. 1 is provided with "star connected" resistors 14a, 14b and 14c.

Each of these resistors 14 is connected to a corresponding one of the output ports, and they are all connected to a reference terminal 15.

In order for the power divider to operate properly, the reference terminal 15
must be open with respect to the ground plane on the opposite side of the substrate 10.

The opposite side of the substrate 10 also has output ports 13a and 13b.
and 13c, the reference terminal 15 and the output port 13a.

An open circuit impedance is provided between the second terminals of 13b and 13c.

This open circuit condition is necessary for proper operation of the "star connected" resistor 14 and is also necessary to provide isolation between the output ports 13, as discussed above.

FIG. 2 shows another known separate power divider.

In addition to the respective elements of the power divider of FIG. 1, the power divider of FIG.
and 16c.

These transmission lines are terminals 30a. 30b and 30
The length is chosen to be approximately half a wavelength, so that the impedance of the "star connected" resistor 14 at c is presented at its corresponding output 13.

Therefore, although the electrical operation is the same as in the power divider of FIG. 1, this resistor 14 is located remotely from the output port 13.

The power dividers of FIGS. 1 and 2 are shown for illustrative purposes as three-way power divider embodiments; the same type of design techniques can be used to create dividers with any number of outputs. It can also be used for

One problem associated with implementing the power divider of FIGS. 1 and 2 at high frequencies is related to the capacitance of resistor 14 to handle medium or high power signals. .

Since the resistor 14 is "star connected",
When dissipating high power signals, they cannot be cooled conveniently.

DESCRIPTION OF THE INVENTION FIG. 3 shows a separate N-way power divider constructed in accordance with the present invention in which the separate resistive terminal connections are augmented in the form of transmission line terminal connections.

The power divider of FIG. 3 has an input port 11. transmission line 12
and an output port 13, which are substantially identical to the corresponding elements of the known power divider of FIG.

In the power divider of FIG. 3, the "star connected" resistors 14 are connected to a set of three transmission lines 18a, 18b.
and 18c.

This transmission line 1B is an internal conductor.

It is in the form of a coaxial cable having a first conductor 19 and a second conductor which is an outer conductor.

The inner conductor 19 of each coaxial cable 18 is connected to a corresponding one of the first output terminals of the output port 13 of the power divider.

The outer conductors of the transmission line 18 are each electrically connected to a reference terminal 15', which in the embodiment of FIG. 3 terminates the inner conductor 20 of the transmission line 22.

Each of the coaxial cables 18 is connected to a terminal with its characteristic impedance.

As a result, each of these cables is electrically equivalent to a resistor connected between the corresponding first output terminal 13 and reference terminal 15'.

It will be clear to those skilled in the art that the transmission line 18 is coupled to the terminal with its characteristic impedance, resulting in a connection between the first output terminal of the output port 13 and the reference terminal 1.
5', which is the desired effect of creating a resistive impedance.

This result, of course, can be achieved with other than characteristic impedance loads using appropriate transformer or matching techniques in the transmission line 18.

The transmission line 22 is a coaxial line selected to have a length rIJ, which line is a quarter wavelength at a selected frequency within the frequency band and short circuit 24.
is terminated by

The result of this shorted quarter wavelength transmission line 22 is:
The purpose is to provide an open circuit impedance between the reference terminal 15' and the second terminal of the output 13 of this power divider.

In the embodiment of FIG. 3, the second terminal of the output port 13 comprises a conductive ground plane 17 on the substrate 10, which ground plane is electrically connected to the outer conductor 26 of the coaxial output connector 27. .

In this open impedance state, reference terminal 15' becomes a common reference terminal and is electrically equivalent to reference terminal 15 in the known power divider of FIG.

The combination of short circuited transmission line 22 and terminated transmission line 18 is therefore electrically equivalent to star connected resistor 14 of the known power divider of FIG.

The transmission line 18 in the embodiment of FIG.
8a, 28b and 28c, which may be conveniently located apart from each other and away from the output 13 of the power divider.

Since these terminations are of the conventional transmission line type, they can be selected to receive high average power signals, and any conventional cooling methods used for such terminations, e.g., heat sinks. It can be seen that cooling can be achieved by radiation cooling, convection cooling, liquid cooling and conduction cooling.

By having this type of isolated resistive terminal connection, the embodiment of FIG. I was fascinated by my sexuality.

Another embodiment of the invention is shown in FIG.
This corresponds to the known power divider of FIG.

The power divider in Figure 4 includes the output port 13.
and the second set of transmission lines 18.
, 16b and 16c.

This set of transmission lines 16 is half a wavelength long at a selected frequency within the operating frequency band and, as in the known power divider of FIG.
The impedance present at 30b and 30c can be applied to the corresponding output port 13.

The embodiment of FIG. 4 also differs from the embodiment of FIG. 3 in that the second set of transmission lines 18 are in the form of microstrips rather than coaxial lines.

In this configuration, one conductor of each of the second set of transmission lines 18 is connected to one terminal of the output port 13 by a half-wave transmission line 16.

The other conductor of the transmission line 18 comprises an electrically conductive ground plane 32 which is connected to a reference terminal 15'' which in the embodiment of FIG. It has become.

In the embodiment of FIG. 4, the open circuit impedance is established between the reference terminal 15'' and the terminal 30 by a shorted parallel plate transmission line having a length rLJ formed between the conductive ground plane 32 and the conductive ground plane 17. The length rLJ is a quarter wavelength at a selected frequency within the frequency band.

This parallel plate transmission line is terminated by a short circuit 34.

In the embodiment of FIG. 4, the impedance provided to transmission line 16 at terminal 30 is also provided to output port 13. In the embodiment of FIG.

This result is electrically equivalent to a star-connected resistor across the outputs 13 of the known power divider of FIG.

As shown in FIG. 4, the transmission line 18 and the reference terminal 1
The use of a half-wavelength transmission line 16 to separate the 5" It is.

Although all embodiments of the invention so far described consist of three-way power dividers, it is noted that such power dividers can be made with any number N of output terminals to form an N-way divider. is clear to those skilled in the art.

Here, N is any integer larger than ■.

Although the present invention is shown in terms of a "power divider", such devices are inherently reversible and can also be used as power combiners, and devices intended for such applications are It is also clear that it is within the scope of the invention.

Having described what is believed to be a preferred embodiment of this invention, it will be obvious that various changes and modifications may be made thereto without departing from the invention. It will be apparent to those skilled in the art that it is intended to cover all modifications and variations within its scope.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a known separate power divider. FIG. 2 shows a known separate power divider in which a "star connected" resistor is located remotely from the output. 3 and 3A are diagrams of a separate power divider made in accordance with the present invention. Figures 4A and 4B are diagrams of another separate power divider made in accordance with the present invention. 10... Insulator substrate, 11...
...Input port, 12...Transmission line, 13...
... Output port, 14 ... Star connected resistor, 15 ... Reference terminal, 16 ... Transmission line, 17 ... Conductive ground Plane, 18...
...Transmission line (coaxial cable), 19...
Internal conductor, 20... Internal conductor, 22...
・Transmission line, 30 (a, b, c)... terminal of star connected resistor 14, 27... coaxial output connector, 26... external coaxial cable Conductor, 28 (a, b. C)... Termination point of transmission line 18, 30 (a,
b. C)...Terminal facing output port 13, 32...
...Conductive ground plane, 34... Short circuit.

Claims (1)

[Scope of Claims] 1. A power port; a set of N output ports, each consisting of a first and a second output terminal; a first set of N transmission lines, each of which has a connection from said input port; wave energy signals to a corresponding one of said output ports, each said transmission line having an electrical frequency of an odd integer multiple of a quarter wavelength at a selected frequency within a selected frequency band. said first set of transmission lines having a length; a second set of N transmission lines, each connected to a corresponding one of said first output terminals, said first conductor and a reference; said second set of transmission lines comprising a second conductor connected to a terminal, said reference terminal being common to all said second conductors of said second set: said first output terminal; means for terminating each transmission line of said second set of transmission lines to provide a substantially resistive impedance between said second output terminal and said reference terminal; means for providing an open circuit impedance between the separated N-way power divider for operation over the selected frequency band.