JP2682010B2 - Antenna shared circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an antenna shared circuit of a wireless communication device that performs simultaneous transmission and reception, and more particularly to an antenna shared circuit configured to select and use two antenna shared filters. .

[Conventional technology]

A commonly used antenna common circuit is shown in FIG. Reference numeral 1 is a transmission filter, and 2 is a reception filter, and the transmission band and the reception band are used as pass bands. A transmitter is connected to the terminal 3 and a receiver is connected to the terminal 4, and the antenna connected to the terminal 5 is shared.

The frequency characteristics of the transmission filter 1 and the reception filter 2 at this time are shown by solid lines in FIG.

Now, consider the case where the transmission band and the reception band are expanded as B _TX0 → B _TX3 and B _RX0 → B _RX3 , respectively, as shown in FIG. When the band is expanded in the same system, the transmission / reception interval is usually constant, so the transmission / reception band interval is narrowed as a → b. On the other hand, if the performance required for the system and the wireless device is the same even in the expanded band, the transmission filter pass loss and the reception band attenuation amount, the reception filter pass loss and the transmission band attenuation amount are I _T and I Must be constant, such as _R and L _T , L _R.

In such a case, the frequency characteristics required for the duplexer are as shown by the broken line in FIG. As is clear from the figure, the transmission filter and the reception filter require steeper attenuation characteristics, and as a result, a larger number of stages are required. Since increasing the number of stages increases the pass loss in the band, it is necessary to increase the Q value of the resonant element in order to reduce it, but this generally involves an increase in the volume of the resonant element.

In this way, when one antenna shared filter as shown in FIG. 3 is used to cope with a wide band, firstly, the number of stages of the resonance element is increased, and secondly, the volume of each resonance element is increased. The volume of the shared antenna circuit increases for two reasons. In this case, the volume increase depends on parameters such as the band expansion, transmission / reception interval, and performance required for the system, but it may be an obstacle to implementation in a portable wireless device.

The method adopted in such a case is shown in FIGS. 6 and 7. In either method, as shown in FIG. 5, the expanded band is divided into two separate shared antenna filters, which are then selected and used by a switch. It is shown that, when the band is divided in this way, it is possible to reduce the size of one antenna shared filter by increasing the band.
Now assume that the bandwidth has been doubled. The number of stages of the transmission filter and the reception filter before expansion is assumed to be 5 stages each, and the volume per stage is a. Then, the volume of the antenna shared filter before expansion is 5a + 5a = 10a.

Next, if the bandwidth is widened with one antenna shared filter, it is assumed that the number of stages must be increased by three stages each.
In this case, the transmission filter and the reception filter each have eight stages. If a Q value of about 8/5 times is required to maintain the same passage loss when increasing from 5 steps to 8 steps, Q is almost proportional to the volume of the resonant element, so the volume of the resonant element is Becomes That is, if one antenna shared filter has a wide band, Becomes

On the other hand, the total volume of each antenna shared filter in the method of dividing the band into two equals 2 x (5a + 5a) = 20a- (2). Comparing (1) and (2), it can be seen that the volume of (2) is smaller by 28%. In addition, in consideration of the fact that it becomes more difficult to adjust the filter as the number of stages increases, as a practical problem, as compared with the case of FIG.
Obviously, the method shown is advantageous. Now, FIG. 6 shows a method of switching the shared antenna filter with a mechanical switch such as a high frequency relay, and FIG. 7 shows a case where the shared antenna filter is switched using an electronic switch such as a PIN diode.

However, both methods have the following problems.

[Problems to be solved by the invention]

In the case of the mechanical switch shown in FIG. 6, three switches 8, 9 and 10 such as relays are required, which is large in volume and loses the advantage of dividing the band and downsizing. In addition, the response speed of the relay is relatively slow, which may cause a problem in the system. In the case of a portable wireless device that requires power saving, the direct current flowing through the three relays is large in terms of power supply. It becomes an obstacle.

On the other hand, in the case of FIG. 7, since the diode is used, the volume increase can be relatively small and the response speed can be increased. However, the sum of the forward currents of at least three diodes (diodes 11 to 13 and diodes 14 to 16) must be constantly supplied, and power consumption is still a design problem.

[Means for solving the problem]

In order to solve the problems of the conventional techniques described above, the antenna sharing circuit of the present invention includes a first antenna sharing filter in which a first transmission filter and a first reception filter are connected in series, and a second transmission filter. And a second reception filter connected in series, and a second antenna shared filter connected in parallel to the first antenna shared filter via a diode switching circuit, the first and second antenna shared filters An antenna sharing circuit configured to select either one of the two by the diode switching circuit and connect the transmitter and the receiver to the shared antenna, wherein the diode switching circuit is the first antenna sharing filter. A first diode including a plurality of switching diodes connected to one end and the other end of the Group, a bias circuit connected between the respective switching diodes of the first diode group, and a switching circuit of the first diode group, and a bias circuit connected to the switching diodes of the first diode group. A second diode group composed of a plurality of switching diodes respectively connected to one end and the other end and an intermediate point; a bias circuit connected between the respective switching diodes of the second diode group; A high potential supply terminal connected to one end of the diode group, a ground potential terminal connected to one end of the second diode group, and the other ends of the first and second diode groups And a control terminal for supplying a high potential and a low potential, the switching die on one end side of the first and second diode groups. Between the switching diodes on the other end side of the first and second diode groups, the shared antenna between the switching diodes at the midpoint of the first and second diode groups, The receiver is connected to each of the terminals and the control terminal is supplied with a high potential or a low potential to select the first or second antenna shared filter, and further, the first antenna shared filter is selected. All of the first diode groups that are conducted at times are connected in series in the DC circuit with the same polarity, and the second diode group that is conducted when selecting the second antenna shared filter is used.
All of the diode groups are also configured to be connected in series with the same polarity in a DC circuit.

[Embodiment] FIG. 1 is an embodiment of the present invention, and the same parts as those in FIG. 7 are denoted by the same reference numerals. The diodes that select one of the antenna shared filters 6 and 7 are 66 to 71, and the DC bias circuits to these diodes are the RF choke coils 39 to 46 and 56 to 58, and the RF bypass capacitors 47 to 50 and 5.
It is isolated from the RF circuit by 9 to 61 and connected to terminals 3, 4 and 5 via DC blocking capacitors 51 to 55.

The method of connecting the diodes 66 to 71 and the bias circuit according to the present invention are not necessarily uniquely determined as in the present embodiment, and the bias circuit may use a distributed constant circuit such as a strip line instead of the RF choke coil. .

FIG. 2 shows an example of a DC connection relationship of the switching diode according to the present invention. Here, three or more diode groups 72 (diodes 66, 68, and 70 in FIG. 1) are diodes that conduct when the antenna common filter 6 is selected, and three or more diode groups 73 (diode in FIG. 1). 67, 69, 71) are diodes that conduct when the shared antenna filter 7 is selected. Here, the number of three or more is set so that when two or more diodes are used in series when the resistance value to the high frequency when one diode is in the off state is not sufficiently large, it can be handled similarly.

In FIG. 2, terminal 63 is always connected to a high potential via resistor 74, and terminal 65 is always connected to a low potential via resistor 62, here GND. In the example shown in FIG.
Is conducted, that is, the antenna shared filter 7 is selected. The diode group 72 is made conductive by setting the control terminal 64 to a low potential, that is, the antenna shared filter 6 is selected. Here, the resistors 62 and 74 are used for the purpose of controlling the current flowing through the diode.

〔The invention's effect〕

As described above, according to the present invention, diode groups each including a plurality of diodes are selectively connected to two antenna common circuits in series in a DC circuit with the same polarity. As a result, the current that flows when one of the two antenna common filters is selected is equal to the current for one diode, and power consumption can be greatly saved. In addition, by providing a control terminal that selects two common antenna filters, an inverter or the like is not required, and selection can be easily performed with only one control signal. In addition, since an electronic switch using a diode is used, the volume can be made smaller and the response speed becomes faster.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 shows an example of connection of a switching diode according to the present invention, FIG. 3 shows a configuration of a general transmission / reception common filter, and FIG.
FIG. 5 is a frequency characteristic diagram of an antenna shared circuit according to a conventional example and the present invention, FIG. 6 shows a conventional technique in which two antenna shared filters are used and selected by a mechanical switch, and FIG. A conventional technique in which two antenna common filters are used and selected by a diode switch is shown. In the figure, 6 and 7 are common antenna filters, 6T and 7T are transmitting / receiving filters, and 6R and 7R are receiving filters.

Claims (1)

(57) [Claims] 1. A first antenna shared filter in which a first transmission filter and a first reception filter are connected in series, and a second
A transmission filter and a second reception filter are connected in series, and a second antenna shared filter connected in parallel to the first antenna shared filter via a diode switching circuit is included. An antenna sharing circuit configured to select either one of the antenna sharing filters by the diode switching circuit and connect the transmitter and the receiver to the shared antenna, wherein the diode switching circuit is the first antenna. A first diode group composed of a plurality of switching diodes respectively connected to one end and the other end of the antenna common filter and an intermediate point; and a bias circuit connected between the respective switching diodes of the first diode group. , Connected to each switching diode of the first diode group And a second diode group composed of a plurality of switching diodes respectively connected to one end and the other end of the second antenna common filter and an intermediate point, and each switching diode of the second diode group. A bias circuit connected between the first diode group, a high potential supply terminal connected to one end of the first diode group, a ground potential terminal connected to one end of the second diode group, A control terminal for supplying a high potential and a low potential, which is connected to the other ends of the first and second diode groups, and the transmitter is provided between the switching diodes on one end side of the first and second diode groups. , The shared antenna is provided between the switching diodes at the midpoints of the first and second diode groups, and the switch on the other end side of the first and second diode groups is provided. The receivers are respectively connected between the switching diodes, and the first or second antenna common filter is selected by supplying a high potential or a low potential to the control terminal, and the first antenna is shared. All of the first diode groups that conduct when selecting a filter are connected in series in the DC circuit with the same polarity, and all of the second diode groups that conduct when selecting the second antenna shared filter. In addition, the common antenna circuit is characterized in that the direct current circuit is configured to be connected in series with the same polarity.