JPH07131251A - Frequency converter - Google Patents

Abstract

PURPOSE:To enable frequency conversion over a wide range through a single VCO. CONSTITUTION:This frequency converter has the VCO 1, a frequency control circuit 2 which varies the oscillation frequency of the VCO 1, a 1st frequency divider 8 which divides the frequency of the oscillation output signal of the VCO 1 to 1/nn which is 1 or an even number, a 2nd frequency divider 9 which divides the frequency of the oscillation output signal of the VCO 1 to mm which is an even number except (n), a switch 11 which selects and outputs the frequency division output signals of the 1st and 2nd frequency dividers 8 and 9, and a multiplying circuit 12 which multiplies the frequency division output signal selected by the switch 11 by a signal to be converted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to frequency conversion for converting an RF signal input of a TV or radio into an IF signal, and R conversion of a VTR.
The present invention relates to a frequency converter used for frequency conversion of an F modulator.

[0002]

2. Description of the Related Art A TV broadcast signal has a wide frequency band from several tens MHz to several hundreds MHz including UHF band and VHF band. Therefore, the frequency conversion signal generated from the local oscillator of the tuner is required to have a very wide frequency band. Since the variable frequency range of the VCO (voltage controlled oscillator) forming the local oscillator is limited, one VCO cannot cover the entire area. Therefore, a plurality of VCOs having different center frequencies are arranged, and the VCO having the optimum frequency is selected and used according to the frequency band.

[0003]

However, having a plurality of VCOs leads to an increase in the number of components and the number of elements because each component such as a resonator is required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and a VCO, a frequency control circuit for changing the oscillation frequency of the VCO, and an oscillation output signal of the VCO of 1 / n ( n is 1 or an even number), a first frequency divider that divides the oscillation output signal of the VCO into 1 / m (m is an even number other than n), and A switch for selectively outputting the frequency-divided output signals of the first and second frequency dividers, and a multiplication circuit for multiplying the frequency-divided output signal selected by the switch and the converted signal are provided.

[0005]

According to the present invention, the oscillation frequency of the VCO is set sufficiently high and the oscillation output signal is divided by a plurality of frequency dividers to obtain a plurality of output signals having different frequencies. Then, one output signal is selected from the plurality of output signals by a switch and applied to the multiplication circuit. Therefore, a VCO equivalently having a wide frequency variable range can be obtained.

[0006]

FIG. 1 is a block diagram showing a frequency converter of the present invention. (1) is a VCO that oscillates at the center frequency of the maximum frequency band of the necessary frequency bands, and (2) is a fixed type. Oscillator (3), frequency divider (4), phase comparator (5),
Frequency control circuit including LPF (6) and programmable frequency divider (7), (8) 1/2 divider, (9) 1 /
4 divider, (10) 1/6 divider, (11) switch that switches according to the required frequency band, (12) is the carrier signal from the switch (11), It is a frequency conversion circuit that performs frequency conversion.

Now, the frequency band of the carrier signal from the switch (11) to the frequency conversion circuit (12) is 500M.
The maximum band is from 1 Hz to 1 GHz, and the minimum is 85 MH
It requires a band between z and 165 MHz. In that case, the variable frequency band of the VCO (1) is set from 500 MHz to 1 GMHz, and an intermediate frequency (for example, 75 MHz) is set.
0 MHz) to the center frequency of VCO (1). V
A frequency control circuit (2) is provided to accurately set the center frequency of CO (1). Frequency control circuit (2)
Then, in order that the oscillation output signal of the oscillator (3) and the oscillation output signal of the VCO (1) which are accurate and have the same oscillation frequency are applied to the phase comparator (5) at the same frequency, the frequency divider (4) and The frequency division number of (7) is set. The error voltage from the phase comparator (5) passes through the LPF (6) to the VCO.
Applied to (1), VCO (1) is exactly 750 MH
It oscillates at z. In this state, the oscillation frequency of the VCO (1) can be changed by changing the frequency division number of the frequency divider (7). In this way, the oscillation frequency of the VCO (1) is set to 50
It can be changed from 0 MHz to 1 GHz.

When the frequency conversion circuit (12) requires a carrier of the maximum frequency band, the switch (11)
To a side. Then 500MHz to 1G
Carriers between Hz are applied to the frequency conversion circuit (12), the converted signal from the input terminal (13) can be converted to a desired frequency and obtained at the output terminal (14). Next, when a band between 85 MHz and 165 MHz is required as a carrier, the switch (11) is switched to the d side. Then, a carrier whose frequency is changed from 85 MHz to 165 MHz by applying a frequency division of 1/6 by the 1/6 frequency divider (10) is applied to the frequency conversion circuit (12). Similarly, in the case of a carrier of 250 MHz to 500 MHz, a 1/2 divider (8) that divides by 1/2 is used, and a carrier of 125 MHz to 250 MHz that divides by 1/4 ( 9) may be used. Similarly, a signal having a frequency lower than 85 MHz can be obtained by dividing the output of the VCO (1) by 1 / 2n with a 1 / 2n (n is a positive integer) frequency divider (not shown). It is possible.

Therefore, according to the block diagram of FIG. 1, it is possible to obtain a substantially expanded frequency variable range with a single VCO. FIG. 2 shows the 1/2 divider (8) and 1 / of FIG.
The concrete circuit diagram of a plurality of frequency dividers that divides the output signal of the VCO (1) such as the 4 frequency divider (9) into even-numbered fractions is shown. The VCO (1) is connected to the terminal (15). The oscillating output signal is applied and the divided output signal is generated at the terminal (16). An "H" level control signal for selecting the frequency division number is applied to the terminals (17) to (22). For example, when the frequency division is not performed, the "H" level is applied only to the terminal (17) and the other terminals are set to the "L" level. Then, the signal from the terminal (15) is obtained as it is at the terminal (16) via the AND gate (23) and the OR gate (24). Next, to perform 1/2 frequency division, the "H" level is applied only to the terminal (18). Then, the signal from the terminal (15) is sent to the AND gate (25) and the OR gate (2).
6), the frequency divider (27), the AND gate (28) and the OAGATE (24) to obtain the terminal (16). After that, by selecting the terminals (19) to (22) similarly, a desired frequency division ratio can be obtained.

[0010]

According to the present invention, it is possible to provide a frequency converter capable of frequency conversion over a wide band by a single VCO.

[Brief description of drawings]

FIG. 1 is a block diagram showing a frequency converter of the present invention.

FIG. 2 is a specific circuit diagram of the frequency divider shown in FIG.

[Explanation of symbols]

 (1) VCO (2) Frequency control circuit (8) 1/2 divider circuit (11) Switch (12) Frequency conversion circuit

Claims (2)

[Claims] 1. A VCO, a frequency control circuit that changes the oscillation frequency of the VCO, and an oscillation output signal of the VCO that is 1 / n (n is 1 or an even number).
A first frequency divider for dividing the VCO oscillation output signal into 1 / m (m is an even number other than n), and the first and second frequency dividers. A frequency converter comprising: a switch that selectively outputs a frequency-divided output signal of a frequency divider; and a multiplication circuit that multiplies the frequency-divided output signal selected by the switch by the converted signal. 2. The frequency converter according to claim 1, wherein the VCO constitutes a PLL circuit including a programmable frequency divider together with the frequency control circuit.