JPH0634747A - Frequency converter - Google Patents

Abstract

PURPOSE:To provide a frequency converter in which intermediate frequency is independent of the passing band width of a high frequency band filter and which is suitable for a receiver. CONSTITUTION:In this frequency converter, a receiving signal, which passed a high frequency band filter 1, and a local signal, which was generated by a local signal generator 4, are mixed by a mixer 2 into intermediate frequency. In extracting only a necessary frequency component by using a low frequency band filter 3, when the frequency to be received is lower than a center frequency of the high frequency band filter 1, a local signal, whose frequency is lower than that of the receiving signal is generated in the local signal generator 4, but, when the frequency to be received is higher than the center frequency, a local signal, whose frequency is higher than that of the receiving signal is generated in the local signal generator 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency converter for use in, for example, a receiver of a radar device, which carries out frequency conversion of a received signal using a mixer.

[0002]

2. Description of the Related Art As is well known, a frequency conversion device used in a receiver of a radar device removes unnecessary wave components from a received signal by a high frequency band filter and then mixes with a local signal by a mixer to obtain an intermediate frequency. Then, only the necessary signal components are extracted by the low frequency band filter. At this time, the frequency component is appropriately controlled by the frequency control device so that the signal component to be extracted can be selected.

However, in the conventional frequency converter as described above, when the pass band width of the high frequency band filter is not sufficiently narrower than the frequency of the signal component required after the output of the mixer, the high frequency component to be frequency converted. Signals other than (for example, 1 / the center frequency of the low frequency band filter 3)
By frequency-converting the signals separated by two frequencies), for example, an output by a double wave of this signal is generated in the pass band of the low frequency band filter, which may cause a malfunction in a receiver or the like.

Therefore, for example, when the frequency converter having the above-mentioned structure is used for the receiver of the radar device, it is necessary to make the intermediate frequency sufficiently higher than the bandwidth of the high frequency band filter. It was sometimes difficult to realize.

[0005]

As described above, in the conventional frequency converter, the intermediate frequency after frequency conversion by the mixer must be sufficiently higher than the pass band width of the high frequency band filter.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a frequency converter suitable for use in a receiver, whose intermediate frequency does not depend on the pass band width of the high frequency band filter. To aim.

[0007]

In order to achieve the above-mentioned object, a frequency converter according to the present invention determines a receiving frequency range for an input signal and a local signal generator for generating a local signal of an arbitrary frequency. A high frequency band filter, a mixer that mixes a high frequency signal obtained by this filter with a local signal generated by the local signal generator to convert it to an intermediate frequency, and a necessary frequency component of the output signal of this mixer. And a frequency controller for controlling the local signal frequency of the local signal generator according to whether the frequency to be received is higher or lower than the center frequency of the high frequency band filter. Configured.

[0008]

In the frequency converter having the above structure, the received signal that has passed through the high frequency band filter and the local signal generated by the local signal generator are mixed by the mixer and converted into an intermediate frequency, which is required by the low frequency band filter. If the frequency to be received is lower than the center frequency of the high frequency band filter when extracting only the desired frequency components, the local signal generator generates a local signal with a frequency lower than the received signal, and if it is higher than the center frequency. The local signal generator is designed to generate a local signal having a frequency higher than that of the received signal.

[0009]

Embodiments of the present invention will be described in detail below with reference to FIG.

FIG. 1 shows the configuration of a frequency converter according to the present invention. A high frequency band filter 1 determines a reception frequency range for an input signal. The mixer 2 mixes the high frequency signal obtained by the filter 1 with a local signal and converts the mixed signal into an intermediate frequency. The low frequency band filter 3 is the mixer 2
Only the necessary frequency components are extracted from the output signal of. The local signal generator 4 generates a local signal having a frequency corresponding to the control signal from the frequency controller 5. The frequency controller 5 determines the frequency of the local signal depending on whether the frequency to be received is higher or lower than the center frequency of the high frequency band filter 1. The operation of the above configuration will be described below.

First, when the frequency to be received is determined,
The frequency controller 5 determines the local frequency corresponding to the frequency. At this time, when the high frequency signal on the low frequency side of the high frequency band filter 1 is received, the local signal generator 4 is caused to generate a local signal having a frequency lower than the received signal. When receiving a high frequency signal in the high frequency band, the local signal generator 4 is caused to generate a local signal having a frequency higher than that of the received signal.

The operation will be described by specifically defining the input / output frequency. Now, it is assumed that the pass band of the high frequency band filter 1 is 1.0 to 1.1 GHz and the pass band of the low frequency band filter 3 is 149 to 151 MHz.

In the conventional method, the local signal generator 4 generates a local signal of 1.15 to 1.25 GHz to frequency-convert all input signals and extract them as intermediate frequency outputs. However, if a 1.15 GHz local signal is generated in order to frequency convert a 1 GHz signal, even if a 1.075 GHz signal is input, it will be frequency converted to a 1.15 GHz signal.

Therefore, in the mixer 2, 2 × 1.15-2 ×
Spurious of 1.075 = 0.15 GHz is generated. Since this spurious component passes through the low-frequency band filter 3, the same phenomenon occurs as if a 1 GHz signal was input at a low level, and a malfunction occurs in reception detection.

Therefore, according to the present invention, when it is desired to receive a signal of 1.00 GHz or more and less than 1.05 GHz, the local signal generator 4 receives 0.85 GHz or more and 0.90 GH.
generate a low frequency local signal below z, and
From 5 GHz to 1.10 GHz, signals of 1.2 GHz to 1.35 GHz are generated.

As a result, at the time of receiving 1 GHz, the local signal is set to 0.85 GHz, so 1.07
Even if 5 GHz is input, the mixer 2 outputs only an output that is a natural number multiple of 0.225 GHz. Therefore, spurious can be removed by the low frequency band filter 3,
It is possible to prevent malfunction. By the way, when the bandwidth of the high frequency band is very wide, it is effective to configure the high frequency band filter as shown in FIG.

That is, the high frequency band filter 11 in FIG. 2 has a filter bank configuration, and the first filter system path and the second filter system path can be selected by the switches S1 and S2. A high pass band filter BPF1 is interposed in the first filter system path, and a low pass band filter BPF2 is interposed in the second filter system path. Switching control of the switches S1 and S2 is performed by a switching control signal from the frequency controller 15. In FIG. 2, the mixer 1
2, low frequency band filter 13, local signal generator 1
Since 4 has the same configuration as that of FIG. 1, its description is omitted here. The operation of the above configuration will be described below.

First, when the frequency to be received is determined,
The frequency controller 15 determines the local frequency corresponding to the frequency. At this time, the high frequency band filter 11
When the switches S1 and S2 are controlled to be switched to the side of the second filter system to receive the high frequency signal on the low pass side, the local signal generator 14 is caused to generate a local signal having a frequency lower than the received signal. In addition, the switches S1 and S2 are set to the first
When switching control is performed on the road side of the filter system to receive a high frequency signal on the high pass side, the local signal generator 14 generates a local signal having a frequency higher than the received signal.

As described above, by using the filter bank in which the switches S1 and S2 and the filters BPF1 and BPF2 are combined, the pass band width of each high frequency band filter 11 is narrowed, and then the frequency conversion is performed. For example, the intermediate frequency can be lowered just as in the above embodiment.

In the embodiment shown in FIG. 2, the number of filter paths of the high frequency band filter 11 is two, but it is needless to say that the number of paths may be increased. Further, it is needless to say that the present invention is not limited to each of the above-described embodiments, and that various modifications may be made without departing from the scope of the present invention.

[0021]

As described above, according to the present invention, the intermediate frequency does not depend on the pass band width of the high frequency band filter,
A suitable frequency conversion device can be provided for use in a receiver.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a frequency conversion device according to the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment according to the present invention.

[Explanation of symbols]

1, 11 ... High frequency band filter, 2, 12 ... Mixer,
3, 13 ... Low frequency band filter, 4, 14 ... Local signal generator, 5, 15 ... Frequency controller, S1, S2 ... Switch, BPF1, BPF2 ... High band filter.

Claims (2)

[Claims] 1. A local signal generator for generating a local signal of an arbitrary frequency, a high frequency band filter for determining a reception frequency range for an input signal, and a high frequency signal obtained by this filter for generating the local signal. Mixer that mixes with the local signal generated by the converter to convert it to an intermediate frequency, a low-frequency band filter that extracts only the necessary frequency components from the output signal of this mixer, and the frequency to be received is in the high-frequency range. A frequency controller that controls the local signal frequency of the local signal generator depending on whether the frequency is higher or lower than the center frequency of the bandpass filter. 2. The high frequency band filter comprises a plurality of filter system paths having band filters of different bands, and one of the filter system paths is selectively controlled according to a frequency to be received. The frequency conversion device according to claim 1, wherein: