JPH10145106A - Frequency variable filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of circuits and the number of components of a drive circuit for the frequency variable filter. SOLUTION: The drive circuit component of a drive circuit is provided with a forward current switching transistor(TR) T1, a TR T2 that connects its output to ground with a reverse bias, and has two bias outputs to which two resistors R of parallel connection are connected to limit a bias current, where the resistors R are connected between output terminals of the TRs T1, T2 providing a forward bias current and a reverse bias voltage. The frequency variable filter 11 is made up of two stages of resonators 1, 2, and the resonators 1, 2 receive the entirely identical bias to so as to be tuned to a certain frequency. Each circuit component of the drive circuit 12 provides bias outputs to two inputs of the resonators 1, 2 to control a PIN diode for bias control for the variable control of a tuning frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency variable filter used in a transceiver for frequency hopping communication, and more particularly to a PIN for controlling a PIN diode for switching a tuning frequency.
The present invention relates to a variable frequency filter having an improved diode drive circuit.

[0002]

2. Description of the Related Art A variable frequency filter used in a transceiver for frequency hopping communication uses a coaxial cavity resonator in which an inner conductor and an outer conductor are short-circuited at one end by a short-circuit surface.

FIG. 3 shows a series circuit using short-circuit bars. A PIN diode 32 is fixed to one end of a short-circuit bar (copper) 31, and another short-circuit bar (copper) 3 is connected to a feedthrough capacitor 33.
4 and the spring 35 are fixed, and the spring 35 is PI
A series circuit connected to the N diode 32 is formed.

FIGS. 4A and 4B show a configuration of a frequency variable filter using the above-described series circuit, wherein FIG. 4A is a side sectional view and FIG. 4B is a front sectional view. A plurality of series circuits 30 shown in FIG. 3 are provided between the inner conductor 41 and the outer conductor 42 so as to be provided radially around the inner conductor 41. One end of the short-circuit bar 31 is fixed to the inner conductor 41, and the feedthrough capacitor 33 is fixed to the outer conductor 42.

The variable frequency control of the filter controls the PIN diode 32 of each series circuit and turns on / off the short-circuit bar 31.
Turning it off changes the tuning frequency. The tuning frequency can be increased by increasing the number of short-circuit rods 31 that are turned on.

FIG. 5 shows a frequency variable filter 51 provided with the resonator shown in FIG. 4 in two stages, which has a high-frequency input (RF input) and a high-frequency output (RF output). , One drive circuit is required for one bit input, and n drive circuits are required for n bits.

Conventional PIN diode drive circuit 52
Is shown in FIG. In the figure, a drive circuit includes a transistor T1 serving as a switch for a forward current, a resistor R1 for limiting a base current of the transistor T1, a resistor R2 for stabilizing a base voltage of the transistor T1, and a resistor R3 for limiting a forward current. A transistor T2 for grounding the output to reverse bias
And a resistor R4 for limiting the current at the time of reverse bias, a capacitor C1 for limiting the ground state of T2, and a resistor R5 for stabilizing the base voltage of T2.

The operation of this circuit is such that when the TTL input is LO, T1 is driven and a current limited by R3 is output. At this time, T2 is turned off, and most of the current is output as it is by setting R4 to a sufficiently large constant. When the TTL input is HI, T1 is turned off,
At T2, the output is grounded until C1 is saturated, and thereafter, the output is applied with a reverse bias voltage via R4.

[0009]

As described above, conventionally, if the input of the filter is n bits, n drive circuits are required.

However, depending on the configuration of the filter, data of different bits may always be switched simultaneously. For example, in the case shown in FIG. 6, when the two stages of resonators are used and the bias for tuning each of the resonators 1 and 2 to a certain frequency is exactly the same, the respective resonators 1 and 2 The bias required for 2 is always the same. In this case, the drive circuit 1 and the drive circuit (n / 2) +1 have the same data input as shown in FIG. 6, output a bias output 1 and a bias output 2 from each, and connect the bias output 1 to the resonator. 1. A bias output 2 is input to the resonator 2. Another drive circuit 2 ...
(N / 2) and the drive circuit (n / 2) +2... N have the same input and different output, and are simultaneously bias-input to the two resonators. As described above, in the conventional circuit configuration, even when such the same bias is applied, an independent drive circuit is provided for each bit, so that the number of drive circuits increases.

An object of the present invention is to reduce the number of drive circuits and the number of components of a filter by outputting a bias with a single drive circuit for the same bit at the input of the filter. is there.

[0012]

In the above circuit, resonators using PIN diodes for bias control of a tuning frequency are provided in a plurality of stages, and a frequency in which the bias for tuning to a predetermined frequency of each resonator is the same is set. A transistor T is provided in the PIN diode drive circuit for switching the frequency of the variable filter.
A plurality of parallel current limiting resistors are connected to the output terminal of the combination of the forward bias current and the reverse bias voltage between T1 and T2. This is achieved by providing a drive circuit that simultaneously controls the PIN diodes of the heater.

According to the above-described means, even when the on-resistance of each PIN diode varies during the simultaneous control of a plurality of PIN diodes, a constant current is connected to each PIN diode because the current limiting resistors are connected in series. To control the bias. Thus, the data of each bit of the plurality of resonators that are switched to the same state can be simultaneously controlled by one drive circuit, and the number of drive circuits can be reduced accordingly.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of a frequency variable filter according to an embodiment of the present invention.
Is composed of a two-stage resonator 1 and a resonator 2. Each of the resonators 1 and 2 has exactly the same bias for tuning to a certain frequency. That is, the bias required for the input 1 of the resonator 1 and the input n / 2 + 1 of the resonator 2 are always the same, and are supplied from the circuit 1 of the drive circuit group 12. The input 2 of the resonator 1 and the input n / 2 + 2 of the resonator 2 are supplied from the circuit 2, and the input n / 2 of the resonator 1 and the input n of the resonator 2 are supplied from the circuit n / 2.

The drive control of the drive circuit 12 controls the circuits 1 data input D _1, the data input D ₂ the circuit 2, a ... circuit N / 2 by the data input D _{n / 2,} the data D ₁
ＤD _{n / 2} is made to vary the frequency corresponding to the tuning frequency.

FIG. 2 is a detailed circuit diagram of the drive circuit 12.
Each drive circuit has two bias outputs. A transistor T1 of a switch for forward current, resistors R1 for limiting the base current of T1, a resistor R2 for stabilizing the base voltage of T1, a transistor T2 for grounding the output to a reverse bias, and a current at the time of the reverse bias Limiting resistance R
4, a capacitor C1 for limiting the ground state of T2,
A resistor R5 for stabilizing the base voltage of the P.2 and a resistor R31 for limiting the bias current in parallel to the output terminal obtained by combining the forward bias current and the reverse bias voltage between T1 and T2.
, And R32, and the PIN output of the frequency variable filter is controlled by the bias output 1 and the bias output 2 via R31 and R32 in series.

In the operation of the drive circuit, when the TTL input is LO, T1 is driven, and the bias current limited by R31 and R32 is supplied from the output 1 and the output 2 to the PIN diode. At this time, T2 is turned off, and
By setting R4 to a sufficiently large constant, most of the current flows directly to the PIN diode of the frequency variable filter.
When the TTL input is HI, T1 is turned off and T2 is turned off.
The output is grounded until C1 saturates, after which a reverse bias voltage is applied to both outputs through R4.

As described above, the drive circuit includes the resonator 1
In the simultaneous control of the PIN diodes 2 and 3, even if the ON resistance of each PIN diode varies, the current limiting resistors R31 and R32 are connected in series. Can drive. As a result, the number of drive circuits is only one half of the number of bias inputs of the filter, and can be reduced to 1 / n in the case of a filter having a plurality of stages of resonators.

[0020]

According to the present invention described above, control can be performed without being affected by variations in the on-resistance of the PIN diode, and the number of drive circuits and components of the filter can be easily reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a frequency variable filter circuit according to an embodiment of the present invention.

FIG. 2 is a drive circuit diagram according to an embodiment of the present invention.

FIG. 3 is a series circuit of a PIN diode.

FIG. 4 is a configuration diagram of a frequency variable filter.

FIG. 5 is a configuration diagram of a conventional frequency variable filter circuit.

FIG. 6 is a conventional drive circuit diagram.

[Explanation of symbols]

T1, T2: transistors, R1, R2, R4, R5 ...
Resistor, R31, R32: current limiting resistor, 11: variable frequency filter, 12: drive circuit, 30: series circuit, 3
1, 34: short-circuit bar, 32: PIN diode, 41: inner conductor, 42: outer conductor.

Claims (1)

[Claims] 1. A frequency variable filter having a plurality of resonators using PIN diodes for bias control of a tuning frequency and having the same bias for tuning to a predetermined frequency of each resonator. A switching transistor T1 and a transistor T2 for grounding the output to a reverse bias are provided, and a plurality of parallel current limiting resistors are connected to an output terminal combining a forward bias current and a reverse bias voltage between the transistors T1 and T2. A variable frequency filter comprising a drive circuit for simultaneously controlling a PIN diode of each resonator for making the above-mentioned bias the same by a bias output via each current limiting resistor in series.