JPS6096933A - Frequency band converting circuit - Google Patents

Abstract

PURPOSE:To convert a frequency band easily by applying an analog input signal to an analog time division transmission element to be stored therein and making the period of a clock pulse applied at read different. CONSTITUTION:An input switch 1 extracts a part required for the band conversion of an analog input signal IN fed to an input terminal 2 and inputs the result to an LPF3. The analog time division transmission element 4 stores an output of an LPF3 by fetching it sequentially as an analog time division signal in response to a drive clock Kf1. Then the analog time division signal stored in the element 4 is outputted sequentially to an LPF7 in response to a drive clock Kf2 having a frequency different from that of the clock Kf1. Furthermore, an output switch 6 outputs an output the LPF7 in synchronizing with the supply of the clock Kf2. Moreover, the pass band of the LPF3, 7 is taken as <=1/2 of the frequency of the clocks Kf1, Kf2 so as to prevent generation of a reflected distortion of the element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a frequency band conversion circuit that compresses or expands the frequency band of an analog input signal and outputs the compressed or expanded frequency band of an analog input signal. This invention relates to a simplified frequency band conversion circuit.

A conventional frequency band conversion circuit compresses or expands the frequency band of an analog input signal and outputs the compressed or expanded frequency band. Conventionally used frequency band conversion circuits use an analog-to-digital conversion circuit to convert an input analog signal into a digital signal, and then sequentially write it into a memory, and sequentially convert the contents of this memory at a speed different from that at the time of writing. The structure is such that it is read out and returned to an analog signal.

However, the frequency band conversion circuit with the above configuration,
The use of an analog-to-digital conversion circuit, memory, and digital conversion circuit makes the circuit complex and requires expensive elements, resulting in an overall increase in cost. Furthermore, when the amount of information to be handled is large, there is a problem in that the memory capacity also needs to be increased accordingly.

DISCLOSURE OF THE INVENTION Accordingly, it is an object of the present invention to provide frequency band conversion for an analog input signal without the use of expensive analog-to-digital converter circuits, memory, digital-to-analog converter circuits, and other components.

In order to achieve such an object, the present invention supplies analog input signals to analog time-division transmission elements such as 00D and BBD and stores them, and also varies the period of the clock pulse ξ applied when reading the signals. It converts the frequency of an analog input signal and outputs the result.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing one embodiment of a frequency band conversion circuit according to the present invention. In the figure, reference numeral 1 denotes an input switch, which extracts a portion of the analog human input signal IN supplied to the input terminal 2 that requires band conversion. 3 is a low-pass filter that receives the output signal of the input switch 1; 4 is a charge coupling device (hereinafter referred to as 00D) as an analog time-division transmission element, which supplies the output signal of the low-pass filter 30 to the clock input terminal 5; The data are sequentially accumulated as time-division analog values by taking in the data using the drive clock Kfl. Therefore, the ON time of the input switch 1 must be within the time that can be stored in the COD. Reference numeral 6 denotes an output switch that selects the output signal of the COD 4 supplied via the ronogus filter and supplies it to the blade 8. This Ij6 is used to remove the aliasing distortion generated in the low-nos filter 3.1 ICOD4, and φ is the frequency of the driving clock Kf1 or Kl at 0OD4. The frequency characteristics are set to such that only components of 1/2 or less are passed.

In the frequency band conversion circuit configured in this way, if the input 42 is lined up with the analog input signal I shown in FIG.
In the state where N is supplied, the input switch 1 is as shown in Fig. 2 (
When it is closed between tL-+2 shown in b), the portion between tl and t1 of the analog input signal IN is multiplied by 6 peaks a as shown in Fig. 2 tc). And this input switch 1
v) The output signal is 0004 in the low pass filter 3.
The generation of aliasing distortion in 0 (JD4) is prevented by passing only the component of 1/2 of the frequency of the drive clock Kfl used when accumulating signals for 0 (JD4).

The output signal of the low-no-miss filter 3 subjected to such processing is supplied to 0OD4. Here electric clock input terminal 5
When 41 is supplied to the drive clock shown in FIG. 2(d) in synchronization with the on-period of the input switch l, 0OD4 divides the output signal of the low-pass filter 3 sequentially in analog time division with the period of the drive clock K (, Then, when the accumulation time between time points tI and 12 ends, the drive clock is set to Kfo (stop) as shown in FIG. 2(d), and the accumulated information is held.

Next, between time points 13 and 14 shown in FIG. 2(d), the drive clock Kl and the drive clock Kf, which has a higher frequency,
, is supplied to the clock input terminal 5, the time-division analog signal stored in 00D4 is converted to the drive clock Kf.
, are output sequentially in synchronization with . Then, this output signal of 0OD4 is applied to the drive clock Kf in a low-pass filter.

When f'dltx ~
It is output as a waveform shown between 14 and 14. In this case, the analog input signal waveform shown between times 11 and 11 in FIG. Since the analog output signal is output from time t3 to t4 as shown in FIG. Then, as shown in Figure 2(f), the output signal of this rotor filter is transmitted over a period of time tl- which is the supply period of one clock Kfl.
It is supplied to the output end 8 via the output switch 6 which is turned on during the period 14.

Here, the compression ratio of the analog output signal with respect to the analog input signal is the driving clock Kfl in the case where 0004 collects and stores the analog input signal in a time-division manner.
When the accumulated time-division analog signals are sequentially output, the frequency ratio with the driving clock Kfl is as follows.
Drive lock Kf! By increasing the frequency of Kf, the compression ratio of the frequency band increases. Furthermore, if the frequency of the driving clock Kf is lowered by the frequency of Kf, the frequency band of the analog output signal to be sent out will be expanded with respect to the analog input signal, and the expansion rate will be the same as that of the driving clock. The frequency ratio is 55KfH.

Here, when changing the compression ratio or expansion ratio of the frequency band, since the drive clock Kt1h or Kf for 0OD4 is fixed, the cutoff frequency of filter 3 or filter 7 is changed accordingly. In addition to using a commonly known switched-capacitor filter as the low-pass filter 3.7 that needs to be changed, the 0OD4 drive clock is changed to a switched-capacitor filter as shown by the dotted line in Figure 1. By supplying the filter to the filter 3.7, the filter characteristics are automatically varied in accordance with the variation of the compression ratio or expansion ratio.

As explained above, in the frequency band conversion circuit according to the present invention, simple and inexpensive elements are used without using expensive elements such as an analog-to-dinotal transformer circuit, a memory, and a digital-to-analog conversion circuit. It has the excellent effect of easily converting frequency bands using a conventional circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the frequency band conversion circuit according to the present invention, and FIG. 2 (, 3 to (f) are operation waveform diagrams of each part of the circuit shown in FIG. Switch, 2... Input end, 3.7...
Ronozos filter, 4... Analog time division transmission element (COD, BBD), 5... Clock input terminal, 6...
・Output switch, 8...output end.

Claims (2)

[Claims] (1) An input switch that inputs a desired period of an analog input signal, and a first switch connected to the output end of this input switch.
and a second drive clock having a frequency different from that of the first drive clock. an analog time division transmission element that sequentially outputs the accumulated information of the analog time division signal via a second filter according to a clock; and an output of the second filter in synchronization with the supply of the second driving clock. the first filter has a passband of 1/2 or less of the drive clock frequency of the first filter,
The second filter has a frequency of 1/ of the second driving clock frequency.
A frequency band conversion circuit characterized in that a pass band is 2 or less. (2) First. The second filter is configured by a switched capacitor filter, and the first filter uses the first drive clock as a clock input, and the second filter uses the @2 drive clock as a clock input. A frequency band conversion circuit according to claim 1.