DE2325741C3 - Circuit arrangement for generating channel frequencies - Google Patents

Description

35

State of the art

A circuit arrangement for generating channel frequencies in at least one frequency range each with a voltage-controlled oscillator whose frequency is reduced to a lower frequency is implemented, in which the lower frequency is fed to an adjustable divider acting as a channel selector whose output signal is obtained by dividing the frequency of a crystal oscillator Frequency, which is equal to the channel spacing, compared in a phase discriminator and at the the voltage-controlled oscillator is regulated with the output signal of the phase discriminator known (DT-OS 22 05 389).

In the circuit arrangement according to DT-OS 22 05 389, the frequency conversion takes place Mixture. In addition to the mentioned crystal oscillator, there is a frequency conversion for each frequency range a crystal oscillator or a changeable oscillator is necessary for all frequency ranges. at If quartz oscillators are used, these must be switched over when changing areas. In the interpretation In the circuit, the tolerances of several crystal oscillators must be taken into account. Besides that the one used in the known circuit arrangement for frequency conversion is suitable Mixer not for implementation in integrated circuit technology.

From the DT-OS 21 26 281 a working with scanning circuit arrangement for generating several Frequencies known at which the control voltage directly through the sampling and storage for the voltage controlled oscillator is generated. With the arrangement according to this laid-open specification the width of the sampling pulses must be approximately equal to half the period of the frequency of the voltage controlled Be an oscillator.

It is also known from GB-PS 10 85 522, Scan sinusoidal oscillations with pulses that are very short in relation to the period duration of these Vibrations are.

task

The invention is based on the object of specifying a multi-channel oscillator in which the voltage-controlled Osällator downstream device for frequency conversion no mixer and no is a common divider and in which at least parts of the frequency conversion device can be integrated are.

solution

The object is achieved as specified in claim 1. A development of the invention is in the Disclaimer specified.

benefits

To convert the frequencies of the voltage-controlled oscillators into the intermediate frequency position the already existing crystal oscillator is used, from which the reference frequency for the phase discriminator is derived, so that a total of only a single crystal oscillator is required. Consequently the accuracy of the output frequency of the multi-channel oscillator is only achieved by this one crystal oscillator definitely. When changing the band, only the frequency of the voltage-controlled oscillator has to be switched will.

Compared to a mixer, the sampler allows higher input levels to be processed and has almost no transmission loss. This brings significant simplifications for the intermediate frequency amplifier, which must supply the control level required for the adjustable divider.

description

The invention will now be explained in more detail with reference to the drawings of an exemplary embodiment. It shows

F i g. 1 is a block diagram of a known arrangement for generating channel frequencies,

F i g. 2 a known device for frequency conversion for the arrangement according to FIG. 1,

F i g. 3 a new device for frequency conversion for the arrangement according to FIG. 1,

F i g. 4 is a diagram to explain the scanning,

F i g. 5 the staircase voltage resulting from the scanning.

The prior art and the invention are for example for two frequency ranges, each with several Channel frequencies explained. The extension to more than two frequency ranges at the state of the Technology is known; for the invention it is described below.

It is now on the basis of FIG. 1 and 2 a known multi-channel oscillator is described.

In Fig. 1, 1 and 2 are two voltage-controlled LC oscillators. With a toggle switch 3.1 the oscillator 1 can with the frequency

or the oscillator 2_ with the frequency f

be switched on. The frequency of the oscillator that is switched on in each case reaches a converter 5 via an input stage 4, which is shown in more detail in FIG. In this the output signal of the isolating stage 4 arrives at one input of a mixer stage 15. 13 and 14 denote two quartz oscillators. The quartz oscillator 13 with the frequency Z ₀₁ or the quartz oscillator 14 with the frequency Zy _{2 can be} switched on with a switch 3.2. The two changeover switches 3.1 and 3.2 are coupled to one another so that when the oscillator frequency Z ₀₁ or Z _{02 is switched on} , the crystal oscillator frequency Zoι or Z _{02 is also} switched on. The frequencies Z ₀₁ and Z ₀ , or Z ₀₂ and Z ₀₂ are mixed together in mixer 15. At the output of a downstream low-pass filter 12, the intermediate frequency Z ₂ = Z ₀₁ -Z ₀ 1 or - f ^ -f ₀₂ occurs. An adjustable frequency divider 7 is controlled via an amplifier 6. It divides the intermediate frequency f _z by an integer N and delivers at its output the divided frequency / r = / z / N> which is fed to one input of a phase discriminator 10.

A crystal oscillator 8 supplies the frequency Z ₀₃ , which is divided by an integer M in a fixed frequency divider 9. Its output frequency fv ⁼ foz / ^{M is} fed to the phase discriminator 10 as a comparison frequency.

The phase discriminator 10 generates a control voltage V _R , the size of which depends on the phase difference between the two input signals. The control voltage is fed to the reactance stages in oscillators 1 and 2 via a low-pass filter 11.

The control process lasts until the frequencies Zr "öd } y match without detent errors. The division ratios N and M are selected so that the comparison frequency Zv is equal to the channel spacing.

Below is a numerical example:

There should be 41 channel frequencies, each 25 KH apart, in two frequency ranges

Z ₀₁ = 62 ... 63 MHz
Z ₀₂ = 92 ... 93 MHz The channels can be set by changing the division ratio N in steps of one.

The new circuit arrangement is now shown with reference to FIGS. 1 and 3, the dashed lines in FIG. 1 now applying. FIG. 3 shows a converter with sampling of the signals from the voltage-controlled oscillators 1 or 2. From the isolating stage 4 in FIG. 1, the signals arrive at a device 17, consisting of a scanning part and a memory part. The scanning part is controlled by a pulse stage 16 in such a way that the input signal is switched through to the memory part during the pulse duration. The pulse duration must be very short compared to the period duration of the oscillator frequencies Z ₀₁ or Z ₀₂ . The pulse repetition frequency is determined by the quartz oscillator 8 (FIG. 1). Its frequency is now denoted by J _0. The quartz frequency Zo is also divided in the divider 9 by the number M , which can also be rational. The divided frequency Zv is fed back to the phase discriminator 10.

During the frequency conversion, the sampling and storage circuit 17 acts like a mixer, to which all harmonics of Z ₀ are fed with the same amplitude up to a certain ordinal number. Which harmonics are used in the frequency conversion is determined by the cutoff frequency of the downstream low-pass filter 12 and by the activated range. At the memory part occurs in FIG. 5 shown staircase voltage V _E , from which the low-pass filter 12 makes a continuous oscillation with the frequency f _z. The intermediate frequency Zz is amplified in the amplifier 6 and divided by N in the frequency divider 7. The frequency j _T = f _z / N, which is fed to the phase discriminator 10, is again obtained at the divider output.

As with F i g. 1, the phase discriminator 10 changes its output voltage U _H until it has brought the voltage-controlled oscillator 1 or 2 via the low-pass filter 11 to a frequency that results in an error-free match between f _T and Zv.

The crystal oscillator frequency Zp becomes equal to that Difference between the two lowest oscillator band frequencies selected, d. H.

be generated.

The conversion frequencies Zp ₁ and f ₀₂ are chosen so that the same intermediate frequency f _L is produced for the lowest frequencies of both frequency ranges.

Z ₀ , = 60 MHz

Z ₀₂ = 90MHz
It is

fz = / 01 - / 01 = / o2 - / <? 2 == ² · · · 3 MHz
It is

A> ⁼ hi A) 2

Next is

M is chosen so that f _{v is} equal to the channel spacing.
It is

f _v =

= 25 KHz

fr = ^ -

At the end of the control process:
Zr = fv
So is

/ V 25-103Hz

and in the regulated state

/ τ = Zv
⁶ S so

The channel frequencies, the frequency of the crystal oscillator and the intermediate frequency are related by the following equations.

Here, α and b are the ordinal numbers of the harmonics of / ₀ , i.e. whole numbers.

The new multi-channel oscillator is shown below with the same numerical values as in FIG. 1 calculated.

It is

fo - / ₀₂ min - Z ₀₁ min = 92 MHz - - 62 MHz ■■ 30MHz Out / ν = : * L = 25 KHz M. follows M = ■■ 1200

and the instantaneous value of the applied oscillator voltage U ₀ is stored in the capacitor until the next sampling without a landing loss. The voltage curve across the capacitor is shown in FIG. 5 shown.

In FIG. 5, the oscillator voltage U _{n is shown} as a pointer rotating with the angular velocity cu ₀₁ = 2π · / _01. If the first sampling takes place with the drawn pointer position at time t == 0, ίο then the full voltage U _{0 is} stored in the capacitor, ie it is U _c = U ₀ .

The next sampling takes place after the time T _Q. The pointer now has an angular path of

T 1 J 01

* - U) ₀₁ -I ₀ - 2.T ---

JQ
covered.

For the lowest frequency: the lower range results in:

30-106

30th

Out
h = / Q

follows for the lower area

N M.

/ e

(62 ... 63) MHz

= 2

30MHz 2

30 / and for the upper area

^N _ / «_ (92 ... 93) MHz M ~ / o 30MHz

2 + - ³ -30

ie the pointer makes two full revolutions until the next scan = 2 · 2 π plus 2/30 revolutions = ^ - · 360 ° = 24 °. Starting from this point, the pointer again makes two revolutions plus 24 ° or: r four revolutions plus 48 °, related to r _0, until the next scanning. Because of the very short sampling time for the amplitude value compared to the time for one revolution of the pointer, the sampler only evaluates the instantaneous value of the voltage U ₀ , which is given by the instantaneous angular value, regardless of the full pointer rotations that took place between two sampling times. The voltage values for the query therefore represent a stepped curve with a cosine curve, with the angle value increasing in steps of 24 °.

The fundamental frequency contained in this oscillation / amounts to:

30th

3 + - Δα

At

with Δα. -

= 2, -r · -rad
30th

With a = 2 and b = 3, JV = 80 ... 120 results in both cases

The channels can also be set by changing the division ratio N in steps of one.

The mode of operation of the scanning and storage device 17 will now be described with reference to FIGS using the numerical values mentioned.

The upper sinusoidal oscillation in FIG. 4 represents the oscillation f _{01 of} the voltage-controlled oscillator 1 after the isolation amplifier 4, which reaches the scanning part. The period of the oscillation Z ₀ is T ₀₁ = Hi _n . Below in Fig. 4 shows the output signal of the pulse stage 16. The pulse repetition frequency is equal to the frequency f _{0 of} the crystal oscillator 8. The time interval is therefore T ₀ = 1, 'fj. The pulse width T _P is very small compared to the period T _{01 of} the frequency Z ₀ , · During the time T _P the sampling switch is closed, (o _z = In ·

2/30 1/30

. = T ₀ =: - = - · ΙΟ- « _sec is / β 30

10 + · - ^ - = 2π · 2 · 10 «rad / sec sec

(»Ζ

Zz = - = 2 · 10 «Hz.
2π

A recalculation for the lowest frequency de;

upper range Z ₀₂ = 92 MHz delivers the same

Value for the intermediate frequency f _z . The difference

consists only in the fact that the pointer between two

Sampling times the angle α = Ίπ (3 - -) rad

thus covers 3 full revolutions plus 2/30 revolutions. As already mentioned, however, di full turns between two Abtastzeitpunk th by the scanner does not recognize this it follows dal you can also capture more than two regions with the Abtaste when making the range distances gleici

For this purpose 2 sheets of drawings

Claims (2)

23 741 Patent claims: . ·· - 1. A circuit arrangement for generating lying in at least one frequency domain channel frequencies _etc. each having a voltage controlled oscillator whose frequency is converted to a lower frequency, wherein the lower frequency is supplied to an acting as a channel selector adjustable divider whose output signal having a by dividing the frequency ei & es crystal oscillator, which is equal to the channel spacing, compared in a P-base discriminator and, in the case of 4, the voltage-controlled oscillator is regulated with the output signal of the phase discriminator, characterized in that the signal of the voltage-controlled oscillator (1, 2) is used for frequency conversion Pulses of the frequency of the crystal oscillator (8) are sampled and the sample is stored until the next sample (16, 17) and that the pulse width (Tp) is very small in relation to the period (T ₀₁ or T ₀₂ ) of the frequency of the voltage controlled oscillator. as 2. Circuit arrangement according to claim 1, for at least two frequency ranges, each are apart by a predetermined frequency value, characterized in that the Frequency of the crystal oscillator is equal to this predetermined frequency.