JPS6130322Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sweep signal generator, and particularly aims to simplify the marker signal generator thereof.

A sweep signal generator generates a signal that changes in a certain frequency range at a constant cycle, and usually has a built-in marker signal generator that displays a fixed frequency at some point within that frequency range. ing.

A block diagram of a conventional sweep signal generator is shown in FIG. 1, where 1 is a sweep signal oscillator, 2 is its amplifier, and 3 is an output terminal for the sweep signal. On the other hand, 4a, 4
b, 4c are marker signal generators that generate appropriate frequencies _a , _b ,
It generates a marker signal _c , and 5 is an output terminal for the marker signal. The marker signal generators 4a, 4b, 4c are _a , _b ,
It consists of an LC circuit with a resonant frequency of _c , and generates a marker signal by inputting a sweep signal.

In the above conventional configuration, for a sweep signal oscillator 1 with a center frequency of ₁ and a sweep range of ₁ - Δ to ₁ ÷ Δ, _a ,
Marker signal generators 4a, 4b, 4 which are _b , _c
One set of marker c is required, and when the sweep signal oscillator 1 outputs a sweep signal in another frequency band, it is necessary to separately provide another set of marker signal generators with frequencies within that frequency band. It was industrially disadvantageous in terms of maintaining uniform precision and cost.

The present invention attempts to obtain necessary marker signals using a set of marker signal generators for a sweep signal oscillator capable of generating several frequency bands.One embodiment of the invention will be described below with reference to FIG. do.

6 is a sweep signal oscillator, 7 is a sweep signal amplifier,
8 is its output terminal. Marker signal generators 9a, 9b, and 9c receive sweep signals and generate marker signals of frequencies _a , _b , and _c , respectively; 10;
is the marker signal output terminal. 11 is the frequency
₂ is a local oscillator, 12 is a mixer, and the above sweep signal enters this mixer from switch 13 when conducting.
It is now frequency converted. 14 is a frequency divider that further divides the frequency of the frequency-converted sweep signal;
15 is an amplifier, and 16 is a terminal for outputting the sweep signal thus converted into another frequency band.

The principle of operation is that the output of the sweep signal oscillator 6 appears at the terminal 8 as a sweep signal of ₁ ± Δ, and the marker signals appear at the terminals 10 at _a , _b , and _c, respectively. On the other hand, when the switch 13 is made conductive, the output side of the mixer 12 has a center frequency of ₁ + ₂ or
A sweep signal of ₁ - ₂ appears, one of which is passed through a frequency divider 14 with a frequency division ratio n and output from a terminal 16 to ( ₁ ± Δ) + ₂ /n or ( ₁ ± Δ) - _2.
/n sweep signal is obtained.

To explain the above example with more specific numerical values, generally when adjusting an FM or AM receiver, the center frequency is 10.7MHz and 455KHz.
It is desirable to have a device that can simultaneously generate two sweep signals. Assume that the sweep signal oscillator is now performing sweep oscillation centered on 10.7MHz, and the marker signals obtained from the three marker signal generators 9a, 9b, and 9c have frequencies _a = 10.55MHz, _b =
Assume that 10.7MHz and _c = 10.85MHz. On the other hand, the local oscillator is 3.875MHz (= ₂ ), and the mixer 12
If we select only the difference from the sweep signal of ₁ = 10.7MHz above, then at the output side of the mixer 12,
This is a sweep signal centered at 6.825MHz. If the frequency is further divided by n=15 using a frequency divider, a sweep signal with a center frequency of 455 KHz is obtained at the terminal 16. At this time, the above 10.55MHz, 10.7M appearing on terminal 10
Hz, 10.85 MHz marker signal is generated from _{the 1} =10.7 MHz sweep signal, which is synchronized with the sawtooth wave of the sweep signal oscillator 6, as is well known. That is,
Since the center frequency of terminal 16 is also synchronized with the 455MHz sweep signal, for example, ( _10.55 - 3.875) / 15 = 445 (K
An apparent marker signal is obtained at the position (Hz).
In this way, the center frequency is set to 10.7M for the FM receiver, similar to that used during conventional tuning.
Hz sweep signal and marker signal every 0.15MHz are
A sweep signal with a center frequency of 455 KHz and a marker signal every 10 KHz are simultaneously obtained for the AM receiver.

In order to make use of the fact that the marker signal is synchronized with the sawtooth wave as described above, even if the sweep signal is converted into various frequency bands, a set of marker signal generators 9a, 9b, 9c is used as described above. It is possible to obtain an apparent marker signal.

In the above, the local oscillator 11 and the mixer 12 were used when obtaining sweep signals in other frequency bands, but as is clear from the fact that the synchronization of the marker signal is used as described above, these are omitted. It is also easily possible to directly lead the original sweep signal to the frequency divider. In this way, in the above embodiment, the marker signal generator 9
Since only one set of a, 9b, and 9c is required, it is easy to take measures for frequency accuracy such as temperature characteristics, and the device itself can be miniaturized, which is advantageous in terms of cost.

As is clear from the above embodiment, the present invention determines the frequency of the local oscillator and the frequency division of the frequency divider so that the marker of the marker signal generator used for the intermediate frequency for FM radio is used for the intermediate frequency for AM radio. With this configuration, it is possible to provide a stable marker at a low cost without using a special frequency meter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional sweep signal generator, and FIG. 2 is a block diagram showing a sweep signal generator according to the present invention. 6...Sweep signal oscillator, 9a, 9b, 9c...
Marker signal generator, 11...Local oscillator, 12...
...Mixer, 14... Frequency divider.

Claims (1)

[Scope of utility model registration request] A sweep signal oscillator whose center frequency is set to an intermediate frequency for FM radio, a marker signal generator that uses a resonant circuit to extract and output the frequency corresponding to the marker from the sweep signal, and the output of the sweep signal oscillator. , AM radio intermediate frequency setting means for performing frequency conversion using a local oscillator and a frequency divider so that the center frequency becomes an intermediate frequency for AM radio,
A sweep signal generator characterized in that the oscillation frequency of the local oscillator and the frequency division ratio of the frequency divider are set so that the position of the FM radio marker matches the position of the AM radio marker.