JP2781591B2 - Frequency divider - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency divider, and more particularly to a regenerative frequency divider that operates stably in a microwave band.

2. Description of the Related Art FIG. 2 shows the configuration of a conventional regenerative frequency divider.

In FIG. 2, reference numeral 1 denotes a pump input terminal 2a of the mixing circuit 2.
Is a mixing circuit provided with an element having a frequency mixing function and an amplifying function. Reference numeral 3 denotes a frequency divider output terminal. A part of the frequency-divided signal output from the mixing circuit 2 is branched and frequency-multiplied by the frequency multiplier 4, and then fed back to the feedback input terminal 6 through the feedback loop 5. You. FIG. 2 shows an example in which the multiplication number of the frequency multiplier is n. When the multiplication number is n, a frequency division of 1 / (n + 1) can be extracted from the frequency divider output terminal 3.

In the regenerative frequency divider shown in FIG. 2, the output is filtered by a filter such as a band-pass filter as necessary, so that power near a required frequency out of the output is selectively extracted and fed back. FIG. 2 generally illustrates the frequency dividing function, and the filter is not shown.

The basic operating principle of the regenerative frequency divider shown in FIG. 2 has been well known for a long time, and has been described in various documents (for example, Document (1): Radio Engineering Handbook, Japan Radio Association, 1954 Vol.6 "Amplification and Oscillation" Vol.5
Chapter “Special vacuum tube amplifier”, 5.5 “Divider”, P.358).

 The principle of operation in FIG. 2 is as follows.

(I) A pump signal having an angular frequency ωp is supplied from a pump power supply 1 to a pump input terminal 2a of a mixing circuit 2 having an element having a frequency mixing function and an amplification function having nonlinear characteristics. The noise level power by the angular frequency omega ₁ of the frequency mixed wave of the output signal of the feedback input signal of the angular frequency Enuomega ₁ is generated at the output terminal of the mixing circuit 2. In this case, there is a relationship of (n + 1) ω ₁ = ωp. The output signal of the frequency-mixed wave is frequency-multiplied by the frequency multiplier 4,
The output (angular frequency nω ₁ ) is fed back to the feedback input terminal 6 by the feedback loop 5.

(Ii) when the Enuomega ₁ input → omega ₁ Output → Enuomega ₁ loop power gain of the multiplier output by setting the feedback phase φn and feedback amount to an appropriate value can be set to 1 or more, the angular frequency omega
_One frequency mixed wave output signal grows. ω ₁ = ωp /
Since (n + 1), a divided frequency signal having an angular frequency ω ₁ / (n + 1) grows.

That is, the mixing circuit 2, by mixing the pump signal input and a feedback input signal, the pump signal of the angular frequency _{ω 1 1 / (n + 1} ) by dividing the frequency formed by the angular frequency omega ₁ /
The (n + 1) frequency dividing signal is generated and output to the frequency divider output terminal 3.

However, in the conventional frequency divider of the type shown in FIG. 2, the power gain (or multiplied power loss) of the frequency multiplier 4 forming the feedback loop is a function of the input of the frequency multiplier 4. Therefore, it is known that the divided frequency is hard to rise. This point is also described in the above section of the above-mentioned document (1). The reason for this is described in detail in Section (2), "Analysis of m / n frequency divider operation by idler feedback", Masami Akaike, IEICE Technical Report, MW88-32 (September 30, 1988), Section 7.1. Has been stated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a frequency divider in which a divided frequency grows stably and reliably.

Means for Solving the Problems A frequency multiplier according to the present invention comprises: a frequency multiplier for multiplying an input signal by a predetermined first multiplier to output a frequency-multiplied signal; a pump input terminal; An input terminal and an output terminal, wherein the output terminal is connected to the feedback input terminal via the frequency multiplier by a first feedback loop, and has a frequency mixing function having a non-linear characteristic and an amplification function. An active element is provided, and the pump signal is multiplied by a predetermined second multiplier by frequency-mixing a pump signal input to the pump input terminal and two feedback signals input to the feedback input terminal. And a mixing circuit that outputs the divided frequency from the output terminal via the frequency divider output terminal, wherein a part of the signal output from the output terminal of the mixing circuit is directly A second feedback loop for feeding back to the feedback input terminal, and wherein the set to a value greater than 1 loop power gain at the frequency of the frequency sub-harmonic of said second feedback loop.

FIG. 1 shows the configuration of the frequency divider according to the present invention. The frequency divider according to the present invention differs from the conventional frequency divider shown in FIG. 2 in that, as shown in FIG. 1, a frequency divider having an element having a frequency mixing function having nonlinear characteristics and an amplifying function is provided. Part of the signal output from the circuit 2 is further branched,
A feedback loop for feeding the branched signal back to the feedback input terminal of the mixing circuit without passing through the frequency multiplier 4 is also provided.

The reason why the frequency divider grows stably and reliably in the frequency divider shown in FIG. 1 is described in the literature (2), sections 7.1 and 7.2. The summary is transcribed as follows.

In the regenerative frequency divider shown in FIG. 2, the signal of the frequency-mixed wave of angular frequency ωp / (n + 1) generated at the noise level is multiplied by n and mixed with the pump signal of angular frequency ωp by the mixing circuit 2. To grow a signal of a frequency mixed wave having an angular frequency ωp / (n + 1).

When the power gain of the mixing circuit 2 is G _M , the power gain of the frequency multiplier 4 is G _D, and the output power of the frequency-mixed wave signal output from the mixing circuit 2 is P ₀ , the power αP ₀ ( α <
If only the signal of 1) is input to the frequency multiplier 4,
Conditions-harmonic signal of angular frequency ωp / (n + 1) is grown is because the condition that larger than loop power gain 1, a _{αG D G M> 1 (1} ).

When the input level is sufficiently low, the input level and the output level of the mixing circuit 2 having an element having a frequency mixing function and an amplification function having ordinary nonlinear characteristics have a linear relationship, that is, the power gain is constant. That is, when a low input level of the mixer circuit 2 is the G _M is constant regardless of the input level.

However, the power gain of the frequency multiplier 4 is generally not constant. This is because the frequency multiplier 4 causes nonlinear characteristics due to the excitation of the input power, and performs frequency multiplication based on the nonlinear characteristics. Therefore, in an ordinary frequency multiplier, when the input level is infinitely small, the nonlinear characteristic becomes infinitely small, and the power gain is also infinitely small. That is, the power gain G _D in the range the input level is low, the A 0
As a larger number and with G _D0 as a constant value, it is approximately expressed in the form G _D = G _D0 (αP ₀ ) ^A (2). From this equation, it is known that G _D → 0 when P ₀ → 0. Equations (1) and (2)
From the equation, the condition for growing the frequency sub-frequency is αG _D0 (αP ₀ ) ^A G _M > 1 (3). When P ₀ → 0, the left side of Expression (3) gradually becomes zero.
That is, the equation (3) does not hold when P ₀ → 0. Equation (3) indicates that some kind of contrivance is required for the growth of the frequency divider in this type of frequency divider, and the frequency divider will not rise without it.

Embodiment A frequency divider according to the present invention will be described below with reference to FIG. In FIG. 1, the same reference numerals are given to the same portions as the conventional technology. In FIG. 1, a known frequency mixer using, for example, an FET (field effect transistor) can be used as the mixing circuit 2. Numeral 7 denotes a part of the signal of the frequency-mixed wave output from the mixing circuit 2, which is directly fed back to the feedback input terminal 6 of the mixing circuit 2 without passing through the frequency multiplier 4. This is a feedback loop that performs The signal of the angular frequency ω ₁ fed back by the feedback loop 7 is also
The signal of the angular frequency n × ω ₁ fed back by the feedback loop 5 is also
The feedback signal is applied to the input terminal of the mixing circuit 2 via the feedback input terminal 6, such as the gate of a common-source FET, and the pump signal is also supplied from the pump power source 1 to the mixing circuit 2 via the pump input terminal 2 a. Same for example FE with source ground
Applied to input terminals such as the gate of T. Mixing circuit 2
It includes a pump signal input to the pump input terminal 2a, by mixing the feedback input signal that is input to the feedback input terminal 6, the pump signal of the angular frequency omega ₁ and 1 / (n + 1) divider A frequency division signal having an angular frequency ω ₁ / (n + 1) is generated and output to the frequency divider output terminal 3.

The power gain of the mixing circuit 2 at the angular frequency ωp / (n + 1)
And G _MS, of the signal to be branched into the feedback loop 7 at the output of the mixing circuit 2, if the power ratio of β with respect to the output signal power of the mixing circuit 2, standing climb a frequency of sub-harmonic is, alpha] G _D0 (.alpha.P ^{_{0) a G M + βG MS}} > is 1 (4). When P ₀ → 0, it suffices that βG _MS > 1 (5). Here, β G _MS is the loop power gain of the mixing circuit 2 and the feedback loop 7 at the angular frequency ω ₁ = ωp / (n + 1).

As described above, G _M is the power gain of the mixer circuit 2, when the input level sufficiently low is a constant value that does not depend on the input and output levels. Therefore, even when the input level is sufficiently low, the above equation (5) can be satisfied by selecting the power ratio β to an appropriate value.

In order to satisfy the expression (5), when the pump signal is supplied from the pump power supply 1 to the mixing circuit 2, the loop power gains of the feedback loops 5 and 7 are both greater than 1 and self-oscillation occurs. For this reason, when the pump signal is cut off, the loop power gains of the feedback loops 5 and 7 must both be smaller than 1. Therefore, the feedback phase at the feedback input terminals 6 of the feedback loops 5 and 7 must be changed. It goes without saying that an appropriate value must be selected.

In FIG. 1, the mixing circuit 2 may be a tandem connection of a frequency mixer and an amplifier. The frequency mixer is not limited to an FET, but may be an active element such as a diode.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a frequency divider in which a frequency division frequency grows stably and surely.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a frequency divider according to the present invention, and FIG. 2 is a circuit diagram showing a conventional regenerative frequency divider. 1 ... Pump power supply, 2 ... Mixing circuit, 2a ... Pump input terminal, 3 ... Divider output terminal, 4 ... Frequency multiplier, 5,
7 ... feedback loop, 6 ... feedback input terminal.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-5566 (JP, A) JP-A-51-15957 (JP, A) JP-A-58-186609 (JP, U) Michael M. Driscoll, "Phase Noise Perfor- mance of Analog Frequency Dividers", IEEE trans. Ultrasonics. Ferroelact rics and Frequency control, vol. 37, no. 4, July 1990 (58) Fields investigated (Int. Cl. ⁶ , DB name) H03B 19/00-19/14

Claims (2)

(57) [Claims] A frequency multiplier for multiplying an input signal by a predetermined first multiplier to output a frequency-multiplied signal, a pump input terminal, a feedback input terminal, and an output terminal; The output terminal is connected to the feedback input terminal via the frequency multiplier by a first feedback loop, and includes an active element having a frequency mixing function having a non-linear characteristic and an amplifying function. The frequency division between the pump signal and the two feedback signals input to the feedback input terminal is performed by frequency-mixing the pump signal with a predetermined second multiple from the output terminal. A frequency divider comprising: a mixing circuit that outputs a signal through a frequency divider output terminal; a second feedback that directly feeds back a part of a signal output from an output terminal of the mixing circuit to the feedback input terminal. Comprising a-loop, frequency divider, characterized in that set to a value greater than 1 loop power gain at the frequency of the divided frequency sub-harmonic of said second feedback loop. 2. The frequency divider according to claim 1, wherein said active element is a field effect transistor.