JPH08204460A - Frequency converter - Google Patents

Abstract

PURPOSE: To provide a high-density and small-sized frequency converter capable of sufficiently suppressing the leakage of unrequired signals near a desired output signal frequency. CONSTITUTION: The input signals of a frequency fi are distributed by a 180-degree hybrid 11, the local oscillation signals of the frequency f1 are distributed by a 90-degree hybrid 12 and they are multiplied by unit frequency converters 13 and 14 and frequency converted. The outputs of the unit frequency converters 13 and 14 are synthesized by a same phase power synthesizer 15 and the output of the frequency 2f1 ±fi is obtained.

Description

Detailed Description of the Invention

[0001]

The present invention is used for frequency conversion in the radio frequency band. In particular, the present invention relates to a frequency converter that can be used in a semiconductor integrated circuit such as a communication MMIC (monolithic microwave integrated circuit).

[0002]

2. Description of the Related Art When a local oscillation signal having a frequency f _l and an input signal having a frequency f _i are applied to a non-linear element such as a transistor or a diode, the non-linear element produces mf _l ± nf.
_A multiplication output signal having infinite frequency components of _i (m and n are integers) is obtained. The frequency converter utilizes this characteristic. In a general frequency converter, since the required local oscillation signal is a high power signal and the input signal is a low power signal, the frequency of the multiplication output signal output from the nonlinear element with available power is , Mf _l ± f _i . Usually, among the multiplication output signals, the frequency component for which m = 1 is output most strongly, so that the frequency after which the desired signal after multiplication satisfies m = 1, that is, f _l ± f _i f _l and f _i are selected.

However, in such a frequency converter, in addition to a desired signal, many unnecessary signals such as a local oscillation signal, a leakage of an input signal, and a signal containing other frequency components generated by a non-linear element are simultaneously output. There was a drawback. In particular, the local oscillation signal is generally input with a large amount of power for the input signal because the greater the input signal strength to the frequency converter, the greater the converted output signal strength. Even if it is about the same as that of the unnecessary signal of, the absolute value of the leakage power becomes large. Therefore, it is required that the degree of suppression of leakage of the local oscillation signal is higher than that of other unnecessary signals.

In order to suppress the leaked local oscillation signal, a filter for removing the frequency f _l component is provided at the output of the frequency converter. However, for f _l , f
_{When i} is extremely small, the frequency f _l + f of the desired signal
_{Since i} or f _l −f _i and f _l are close to each other, f _l
Suppression of only the component was very difficult.

Two examples of conventional frequency converters that solve the above problems are shown in FIGS. 3 and 4, respectively.

The conventional example shown in FIG. 3 is provided with an input signal input terminal 1, a local oscillation signal input terminal 2 and a signal output terminal 3, and further, a 180-degree hybrid 31 operating in the input signal frequency band, a local oscillation signal frequency. 180 working in obi
The unit frequency converters 33 and 34 and the in-phase power combiner 35 each of which includes a degree hybrid 32, a non-linear element, a matching circuit thereof, and a DC circuit. Here, since the 180-degree hybrid 31 that operates at the input signal frequency becomes significantly larger than the other components, it is attached externally when this frequency converter is manufactured as an integrated circuit.

The input signal is input to the input signal input terminal 1 and supplied to the unit frequency converters 33 and 34 by the 180-degree hybrid 31 with a phase difference of 180 degrees, that is, π. The local oscillation signal is input to the local oscillation signal input terminal 2 and the 180 degree hybrid 32
The unit frequency converter 33 with a phase difference of
34. The unit frequency converters 33 and 34 multiplies them and frequency-converts them to obtain frequencies f _l + f _i and f
and it outputs a signal of _l -f _i. These signals are combined by the in-phase power combiner 35 and output to the signal output terminal 3.

The output phase of the unit frequency converter 34 with respect to the output phase of the unit frequency converter 33 is the frequency f
For _l + f _i, [phase difference between the local oscillation signal: [pi] +
[Phase difference of input signals: π] = 2π, that is, 0, and they are in phase. For the frequency f _l + f _i , [phase difference of local oscillation signal: π] − [phase difference of input signal: π] = 0, which is also in phase. On the other hand, the phase difference of the leaked local oscillation signals remains π, which is the opposite phase. When these signals are combined by the in-phase power combiner 35, the desired output signals input in the same phase are strengthened and output, while the leaked local oscillation signals are input in the opposite phase, so they cancel each other out. Will not be output.

The conventional example shown in FIG. 4 is provided with an input signal input terminal 1, a local oscillation signal input terminal 2 and a signal output terminal 3, and further, a 180 degree hybrid 41 operating in the input signal frequency band, a local oscillation signal frequency. Unit frequency converters 43, 44 and 90 each composed of a 90-degree hybrid 42 operating in a band, a non-linear element, its matching circuit and a DC circuit.
A hybrid 45 is provided. In this conventional example as well, similar to the one shown in FIG. 3, the 180-degree hybrid 41 operating at the input signal frequency is significantly larger than the other components, so that it is externally attached when manufactured as an integrated circuit. .

The input signal is input to the input signal input terminal 1 and supplied to the unit frequency converters 43 and 44 by the 180-degree hybrid 41 with a phase difference of 180 degrees, that is, π. The local oscillation signal is input to the local oscillation signal input terminal 2, and the 90-degree hybrid 42 causes the unit frequency converter 43 to have a phase difference of 90 degrees, that is, π / 2.
44. The unit frequency converters 43 and 44 frequency-convert them, and the frequencies f _l + f _i and f _l −f _{i are obtained.}
The signal of is output. These signals are combined by the 90-degree hybrid 45 and output to the signal output terminal 3.

The output phase of the unit frequency converter 44 with respect to the output phase of the unit frequency converter 43 is the frequency f _l + f _i
For the above, [the phase difference of the local oscillation signal: π / 2] + [the phase difference of the input signal: π] = 3π / 2, which is equal to the phase difference −π / 2. Regarding the frequency f _l + f _i , [phase difference of local oscillation signal: π / 2] − [phase difference of input signal:
π] = − π / 2, which is the same as the case of the frequency f _l + f _i . On the other hand, the phase difference between the leaked local oscillation signals is π / 2. On the other hand, the 90 degree hybrid 45
For the output of the unit frequency converter 43, the unit frequency converter 4
It is arranged so that the output of 4 is advanced by π / 2 and combined. Therefore, for the desired output signal, the phase of the signal input from the unit frequency converter 44 is [input from the unit frequency converter 44: -π / 2] + [90 degree hybrid 4
Phase advancing amount in 5: π / 2] = 0, and both become in phase and mutually strengthened and output. On the other hand, in the leaked local oscillation signal, the phase of the signal input from the unit frequency converter 44 is [the input from the unit frequency converter 44: π / 2 with respect to the phase of the signal input from the unit frequency converter 43. ]
+ [Advancing phase in 90 degree hybrid 45: π / 2] = π
Since both are in opposite phase, they are not canceled and output.

[0012]

However, in the conventional example shown in FIG. 3, when a high frequency equal to or higher than the microwave is used as the local oscillation signal frequency, it is attempted to form a plane circuit for integrating the 180 degree hybrid. Then, a high-impedance line is required, and there is a problem that the circuit becomes large and miniaturization is difficult.

Further, the conventional example shown in FIG.
The degree hybrid does not require a high impedance line as high as the 180 degree hybrid, but since it uses two 90 degree hybrids, downsizing is also difficult.

Further, in the conventional examples shown in FIGS. 3 and 4, as the required frequency of the local oscillation signal becomes higher, the constituent elements such as the oscillator, the multiplier and the power amplifier which constitute the local oscillator are increased. There is a problem that it is expensive and difficult to realize, and that the loss of the coaxial line, the connector, and other connecting portions required until the local oscillation signal is input to the frequency converter increases.

The present invention solves such a problem, without using a 180-degree hybrid for a local oscillation signal,
An object of the present invention is to provide a high-density and small-sized frequency converter capable of sufficiently suppressing leakage of an unnecessary signal close to a desired output signal frequency.

[0016]

The frequency converter of the present invention comprises first signal distribution means for distributing an input signal of frequency f _i into two signals having phases different from each other by 180 degrees, and local oscillation of frequency f _l . A second signal distribution means for distributing the signals into two signals having mutually different phases; one of the two signals distributed by the first signal distribution means and the two signals distributed by the second signal distribution means. A first frequency conversion means for multiplying one by using a non-linear element, the other of the two signals distributed by the first signal distribution means, and the other of the two signals distributed by the second signal distribution means And a second frequency conversion means for multiplying and by a multiplication characteristic substantially equal to that of the first frequency conversion means, and a combination means for combining the output of the first frequency conversion means and the output of the second frequency conversion means. To a frequency converter equipped with The second signal distribution means includes a 90-degree hybrid that distributes the local oscillation signal with a phase difference of 90 degrees, and the combining means is included in each output of the first frequency conversion means and the second frequency conversion means. Frequency 2
It is characterized in that it includes means for synthesizing in phase so that at least one component of f _l ± f _i reinforces each other.

It is desirable to further include a local oscillation signal suppressing circuit for suppressing the frequency f _l component at the input or output of the synthesizing means.

[0018]

In the frequency converter of the present invention, the local oscillation signals input to the first and second frequency conversion means are
The signal is distorted by the non-linear element that constitutes the frequency conversion means and becomes a signal having a frequency component that is an integral multiple of the local oscillation signal. At this time, the phase difference of the frequency component n times (n is an integer) of the local oscillation signal in the two frequency conversion means is n since the local oscillation signal is input with a phase difference of 90 degrees, that is, π / 2. It is doubled n × (π / 2). On the other hand, the input signal is input with a phase difference of 180 degrees, that is, π. Therefore, as a result of multiplication in the two frequency conversion means,
The phase difference between the output multiplication signals is n × (π / 2) + π. Here, since the desired multiplication output signal is 2f _l ± f _i , the phase difference is 2 × (π / 2) + π = 2π = 0. The multiplication signals output from the two frequency conversion means are in phase with each other, and are strengthened by the means for combining in phase and output.

On the other hand, what has a large influence as an unnecessary signal close to the desired signal frequency is the second harmonic component 2f _l of the local oscillation signal generated by the first and second frequency converting means. However, the phase difference of the second harmonic component 2f _l of the local oscillation signal leaked from the two frequency conversion means is 2 × (π / 2) =
Since the multiplication signals output from the two frequency conversion means have opposite phases, they cancel each other in the in-phase combining means and are not output.

Further, in the frequency converter of the present invention, since the frequency of the required local oscillation signal is 1/2 of the frequency of the local oscillation signal required in the above-mentioned conventional example, the frequency of the local oscillation signal and the desired frequency are desired. It is far from the signal frequency,
It is easy to suppress the leaked local oscillation signal to the output side by the local oscillation signal suppression circuit configured by a matching circuit, a filter, and the like, and the local oscillation signal suppression circuit has a small influence on the output signal. Furthermore, since the frequency of the local oscillation signal is low, the oscillator, multiplier, power amplifier, and other components that make up the local oscillator can be obtained inexpensively and easily, and it is necessary until the local oscillation signal is input to the frequency converter. It is possible to reduce the loss of a coaxial line, a connector, and other connecting portions.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a frequency converter according to the first embodiment of the present invention. This frequency converter has an input signal input terminal 1, a local oscillation signal input terminal 2 and a signal output terminal 3, and further has a 180 degree hybrid 11 operating in the input signal frequency band and a 90 degree operating in the local oscillation signal frequency band. A unit frequency converter 13 including a hybrid 12, a non-linear element, a matching circuit thereof, and a DC circuit,
4, an in-phase power combiner 15 and a local oscillation signal suppression circuit 16 are provided. The 180 degree hybrid 11 operating at the input signal frequency is significantly larger than the other components and is therefore externally mounted when the frequency converter is manufactured as an integrated circuit.

The 180-degree hybrid 11 divides the input signal input from the input signal terminal 1 into two signals having phases different from each other by 180 degrees, that is, π. The 90-degree hybrid 12 divides the local oscillation signal input from the local oscillation signal input terminal 2 into two signals with a phase difference of 90 degrees.
The unit frequency converter 13 performs frequency conversion by multiplying one of the two signals distributed by the 180-degree hybrid 11 and one of the two signals distributed by the 90-degree hybrid 12 by using a non-linear element. The unit frequency converter 14 multiplies the other of the two signals distributed by the 180-degree hybrid 11 and the other of the two signals distributed by the 90-degree hybrid 12 by a multiplication characteristic substantially equal to that of the unit frequency converter 13. Then, frequency conversion is performed. The in-phase power combiner 15 combines in-phase components so that the components of the frequencies 2f _l ± f _i included in the outputs of the unit frequency converters 13 and 14 mutually intensify each other, and outputs them via the local oscillation signal suppression circuit 16. Output to the signal output terminal 3.

Here, the local oscillation signals input to the unit frequency converters 13 and 14 are the unit frequency converters 13 and 14, respectively.
The signal is distorted by the non-linear element forming 14 and has a frequency component that is an integral multiple of the local oscillation signal. The phase difference of the second harmonic of the local oscillation signal in the two unit frequency converters 13 and 14 is 2 × (π / 2) because the local oscillation signal is input with a phase difference of 90 degrees, that is, π / 2. Become. Therefore, the output phase of the unit frequency converter 14 with respect to the output phase of the unit frequency converter 13 has a frequency of 2f ₁ + f _i
2 × [Phase difference of local oscillation signal: π / 2] +
[Phase difference of input signals: π] = 2π, that is, 0, and they are in phase. For frequency 2f _l + f _i , 2 × [phase difference of local oscillation signal: π / 2] − [phase difference of input signal:
π] = 0, which is also in phase. On the other hand, the undesired signal close to the desired signal frequency is greatly affected by the second harmonic component 2f of the local oscillation signal generated by the nonlinear element.
_{l is} a leak. However, two unit frequency converters 1
The phase difference between the local oscillation signals leaked from 3 and 14 is 2 × (π
/ 2) = π, which is the opposite phase. Therefore, when these signals are combined by the in-phase power combiner 15, the desired signals input in the same phase are strengthened and output, and the leaked local oscillation signals are input in the opposite phase, so they cancel each other out. It will not be output. Further, the leakage of the local oscillation signal itself (frequency f _l ) is suppressed by the local oscillation signal suppressing circuit 16.

In this embodiment, the in-phase power combiner 1
In the simplest configuration, 5 is a unit frequency converter 13,
The output of 14 may be simply connected. Further, since the desired output signal frequency at this time is about twice the local oscillation signal frequency, which is far from the local oscillation signal, the local oscillation signal suppressing circuit 16 that hardly affects the desired output signal. Is simple and can be easily realized, for example, by adding a λ / 4 open stub of the local oscillation signal to the signal line in parallel. Further, although the local oscillation signal suppression circuit 16 is connected to the output side of the in-phase power combiner 15 in this embodiment, the present invention can be similarly implemented by connecting it to the input side of the in-phase power combiner 15.

FIG. 2 shows the results of simulating the operating characteristics of the embodiment shown in FIG. 1 by the harmonic balance method. In this simulation, the frequency of the local oscillation signal was 30 GHz, the input power was +10 dBm, the frequency of the input signal was 1 GHz, and the input power was -10 dBm. Here, the isolation between the two output terminals of the 90-degree hybrid 12 is 40 dB, and the in-phase power combiner 15 is the output matching of the two non-linear elements forming the two unit frequency converters 13 and 14. By using a single matching circuit, the circuit of the frequency converter is downsized. From the results of FIG. 2, it can be seen that the conversion loss is about 11 dB, and the second harmonic of the local oscillation signal, which is an unnecessary signal that is close to the conversion loss, is suppressed by 26 dB or more from the desired output signal.

[0027]

As described above, the frequency converter of the present invention, when implemented as an integrated circuit, is 90 degrees for a local oscillation signal except for a 180 degree hybrid for an input signal which is usually externally attached. It can be configured by a hybrid, two unit frequency converters, and one in-phase power combiner, and it is not necessary to use a 180-degree hybrid for a local oscillation signal, and the circuit can be downsized.

Further, since the required frequency of the local oscillation signal is 1/2 of the conventionally required local oscillation frequency signal, the local oscillation signal frequency and the desired signal frequency are widely separated from each other, and the matching circuit and It becomes easy to suppress the leaked local oscillation signal to the output side by the local oscillation signal suppression circuit including a filter and the like. Further, since the required frequency of the local oscillation signal is 1/2, the oscillator, the multiplier, the power amplifier and other components constituting the local oscillator can be obtained inexpensively and easily, and the local oscillation signal can be converted into the frequency converter. It also has the effect of reducing the loss of the coaxial line, connectors, and other connection parts that are required before the input.

[Brief description of drawings]

FIG. 1 is a block diagram showing a frequency converter according to an embodiment of the present invention.

FIG. 2 is a diagram showing a simulation result of an example.

FIG. 3 is a block diagram showing a conventional frequency converter.

FIG. 4 is a block diagram showing another conventional example.

[Explanation of symbols]

1 Input signal input terminal 2 Local oscillation signal input terminal 3 Signal output terminal 11, 31, 32, 41 180 degree hybrid 12, 42, 45 90 degree hybrid 13, 14, 33, 34, 43, 44 Unit frequency converter 15, 35 In-Phase Power Combiner 16 Local Oscillation Signal Suppression Circuit

Claims (2)

[Claims] 1. An input signal of frequency f _i whose phases are 1 relative to each other.
A first signal distribution means for distributing two signals different by 80 degrees, a second signal distribution means for distributing a local oscillation signal of frequency f _l into two signals having mutually different phases, and the first signal distribution means Frequency conversion means for multiplying one of the two signals distributed by the second signal and one of the two signals distributed by the second signal distribution means using a non-linear element, and the first signal distribution A second frequency for multiplying the other of the two signals distributed by the means and the other of the two signals distributed by the second signal distribution means with a multiplication characteristic substantially equal to that of the first frequency conversion means. In a frequency converter comprising a converting means and a combining means for combining the output of the first frequency converting means and the output of the second frequency converting means, the second signal distributing means includes the local oscillation signal. 90 degrees A 90-degree hybrid that distributes with a phase difference; and the synthesizing means is such that at least one component of the frequencies 2f ₁ ± f _i included in the respective outputs of the first frequency converting means and the second frequency converting means is mutually A frequency converter comprising means for synthesizing in phase so as to strengthen each other. 2. The frequency converter according to claim 1, further comprising a local oscillation signal suppressing circuit that suppresses a frequency f _l component at an input or an output of the synthesizing means.