JPH0795695B2 - Transmitter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transmitter, and more particularly, to frequency mixing means used in the transmitter.

[Prior Art] FIG. 8 is a block diagram of a conventional high-frequency transmitter in the microwave band as described in NEC Technical Report, Vol. 41, No. 6, page 23, issued on July 1988, for example. Here usually
Input an intermediate frequency signal (frequency f _if ) in the VHF to UHF band and input a high frequency signal in the microwave band or millimeter wave band (frequency
An explanation will be given using a high frequency transmitter that outputs f _rf ) as an example.
In the figure, (1) is a terminal, (2) is an intermediate frequency amplifier for amplifying an intermediate frequency signal (frequency f _if ) input from the terminal (1), (3) is a local oscillator whose output frequency is f _lo ,
(4) is a bandpass filter whose center frequency is f _rf , (5)
Is a high-frequency amplifier that amplifies a high-frequency signal (frequency f _rf ),
(6) is a terminal, (7) is an antenna, and (8) is a mixer for frequency mixing the intermediate frequency signal (frequency f _if ) and the output signal (frequency f _lo ) of the local oscillator (3).

Next, the operation will be described.

If an intermediate frequency signal (frequency f _if ) is applied to terminal (1),
This signal is amplified by the intermediate frequency amplifier (2) and then added to the mixer (8). In this mixer (8), the intermediate frequency signal (frequency f _if ) and the output signal of the local oscillator (3) (hereinafter abbreviated as local oscillation signal, frequency f _lo ) are frequency mixed. By this frequency mixing, a high frequency signal (frequency f _rf ) and an image signal (frequency f _im ) having a frequency given by the following equation are generated in the mixer (8).

f _rf = f _lo + f _if (1) f _im = f _lo −f _if (2) Furthermore, in addition to these signals, the leaked wave (frequency f _lo ) of the local oscillation signal is output from the mixer (8). It The approximate power of the signal thus output from the mixer (8) is shown in FIG. A bandpass filter (4) is provided to extract only a desired high frequency signal from the output signal of the mixer (8). The characteristic of this bandpass filter (4) is that adjacent frequencies f _lo are as shown in FIG.
Designed to damp. Then, the signal of the frequency f _rf output from the band pass filter (4) is amplified by the high frequency amplifier (5) and output to the terminal (6). As described above, the high frequency transmitter has a function of frequency-converting and amplifying the intermediate frequency signal (frequency f _if ) into a high frequency signal (frequency f _rf ) and supplies the output signal to the antenna (7).

When a high-frequency transmitter having a high-frequency signal frequency f _rf in the quasi-millimeter wave band or higher is realized by the conventional configuration as described above, f _if << f _rf in the above formula (1), so the local oscillation frequency f _lo
Since the high frequency signal frequency f _rf and the high frequency signal frequency f _rf are close to each other, a sharp attenuation characteristic is required by the band pass filter (4). Therefore, it becomes difficult to form the bandpass filter (4) with a microwave integrated circuit having a low Q, and a bandpass filter (4) using a waveguide having a higher Q or a dielectric resonator is required. Become. FIG. 11 is a configuration diagram showing a configuration example of a high frequency transmitter in the case of using a band pass filter (4) using a dielectric resonator. In the figure, (9) is a dielectric resonator, (10) is a dielectric substrate on which the dielectric resonator (9) is mounted, and (11) is a movable short-circuit plate for setting the resonance frequency of the dielectric resonator (9). Is. As described above, when the frequency of the high frequency transmitter is increased, it is usually necessary to configure the band pass filter (4) with a three-dimensional circuit.

[Problems to be Solved by the Invention] As described above, in the case of increasing the frequency of the conventional high-frequency transmitter, in order to suppress the leak wave of the local oscillation signal from the mixer (8), A bandpass filter (4) is required. Therefore, there is a problem that the high frequency transmitter becomes large. Further, when the band pass filter (4) for a three-dimensional circuit as described above is used, it becomes difficult to monolithically integrate it on a semiconductor substrate, or adjustment of the three-dimensional circuit is necessary to obtain a steep attenuation characteristic. However, there is a problem that it is not suitable for mass production.

The present invention has been made in order to solve the above-mentioned problems, and it is a small-sized transmitter which is easy to be monolithically integrated and in which the attenuation characteristic required for a filtering means for selecting a signal of a predetermined frequency is greatly relaxed. Aim to get the opportunity.

[Means for Solving the Problems] A transmitter according to the present invention is a frequency mixer that frequency-mixes a local oscillator that generates a local oscillation wave, an input intermediate frequency signal, and the local oscillation wave to generate a transmission signal. Means, filtering means for extracting only the transmission signal from the output of the frequency mixing means, high frequency amplification means for performing high frequency amplification by receiving the output of the filtering means, and transmission for receiving the output of the high frequency amplification means In a transmitter equipped with a transmission antenna that radiates a signal, when the frequency of the local oscillation wave is f _lo , the frequency of the intermediate frequency signal is f _if , and the frequency of the transmission signal is f _rf , these frequencies are f _{When the} frequency mixing means is set to satisfy the relation _if <f _lo <f _rf , and the frequency mixing means is m = 2, 3, ..., A frequency mf that is m times the frequency f _lo of the local oscillation wave. _lo and the above intermediate frequency signal The difference and the frequency of the sum of the frequency f _if of | mf
a harmonic mixer that outputs two signals of _lo ± f _if |, and the filtering means uses either one of the two signals output by the frequency mixing means as a transmission signal of frequency f _rf , When the other is an image signal of frequency f _im , the frequency f _rf
And a first band-stop filter unit configured to block the harmonics contained in the local oscillation wave and supply the frequency mixing unit, while being configured so that the attenuation characteristic changes gently between the frequency mixing unit and the frequency f _im , Second band stop filtering means for blocking higher harmonics contained in the intermediate frequency signal and supplying the same to the frequency mixing means.

[Operation] In the present invention, the frequency mixing means is m = 2,
, 3, the difference between the frequency mf _{lo, which} is m times the frequency f _lo of the local oscillation wave, and the frequency f _if of the intermediate frequency signal, and the sum frequency | mf _lo ± f _if | The filtering means that outputs a signal and has an attenuation characteristic that changes gently between the frequency f _rf and the frequency f _im suppresses the image signal, and the first band-stop filtering means is included in the local oscillation wave. The harmonics are blocked and supplied to the frequency mixing means, and the second band stop filtering means blocks the harmonics contained in the intermediate frequency signal and supplies the frequency mixing means.

[Embodiment] FIG. 1 is a structural explanatory view for explaining one embodiment of a transmitter of the present invention, and FIG. 2 is a structural diagram of the one structural example. In these figures, (1) to (7) are shown in FIG.
It is the same as that shown in FIG. 11, and (12) is a mixer according to the present invention which constitutes a frequency mixing means,
Here, the above integer m, n is an even harmonic mixer whose value satisfies the condition that | m ± n | is an odd number. As the even harmonic mixer (12), an anti-parallel diode pair formed by connecting diodes of opposite polarities in parallel, or a diode ring or the like is used.

Next, the operation will be described.

Here, the VHF to UHF intermediate frequency signal (frequency
The description will be given by taking as an example a high-frequency transmitter similar to the conventional example that inputs f _if ) and outputs a high-frequency signal (frequency f _rf ) in the microwave band or millimeter wave band.

The transmitter according to the invention uses an even harmonic mixer (12) for frequency mixing. This even harmonic mixer (12)
IEEE TRANSACTION ON MICROWAVE, issued in August 1975
As described on pages 667 to 673 of THEORY AND TECHNIQUES, VOL.MTT-23, NO.8, the local signal f ₁
Is a mixer that outputs a frequency f ₃ given by the following equation, when two waves of the input signal f ₂ are input.

_{f 3 = | mf 1 ± nf} 2 | (3) | m ± n | = 2k + 1 (4) where (3), m, n, k is an integer (4).

Normally, as a high frequency signal (frequency f _rf ), m is an even number because a mixer is used under the condition of n = 1 (5),
Equation (3) can be transformed into the following equation.

f ₃ = | 2if ₁ ± f ₂ | (6) However, in the formula (6), i is an integer.

When this even harmonic mixer (12) is used, as is apparent from the equation (6), a high frequency transmitter with a local oscillation frequency of 1 / 2i of the ordinary mixer (8) shown in the conventional example of FIG. 8 is used. Can be operated. In the following explanation, the lowest order operation,
That is, the description will be given by taking the case of i = 1 as an example.

Frequency f as the local oscillation signal f ₁ in the even harmonic mixer (12)
_When a local signal of _lo ′ (frequency f _lo ′ = f _lo / 2) and an intermediate frequency signal (frequency f _if ) are input as the input signal f ₂ , due to frequency mixing, a high frequency signal of the frequency given by the following equation,
And an image signal (frequency f _im ).

f _rf = 2f _lo ′ ＋ f _if (7) f _im ＝ 2f _lo ′ −f _if (8) Furthermore, from the even harmonic mixer (12), in addition to these signals, the leaked wave f _lo ′ of the local oscillator signal is Is output. The frequency relationship and power of these signals are shown in FIG. FIG. 3 shows an example of the experimental results. As shown in the figure, the signal of the frequency f _lo (2f _lo ′) is reduced by 50 dB or more as compared with the normal mixer (8). Note that the signal output power at the frequency f _lo (2f _lo ′) is the value of the diode of the pair of anti-parallel diode pairs that are used in the configuration of the even harmonic mixer (12) and are formed by connecting diodes of opposite polarity in parallel. This is due to characteristic variations, and in principle (2f _lo ′ +
The signal component of frequency f _lo (2f _lo ′) adjacent to f _if ) and (2f _lo ′ −f _if ) is not output at all.

From the above, in the high-frequency transmitter according to the present invention, the attenuation characteristic required for the bandpass filter (4) is greatly relaxed as shown in FIG. Therefore, the band pass filter (4) should be composed of a microwave integrated circuit that has a low Q but is small, such as a parallel combination of open-ended 1/2 wavelength resonators as shown in FIG. You can The bandpass filter (4) may be constructed in an interdigital form using a 1/4 wavelength resonator.

As described above, in the transmitter according to the present invention, by using the so-called even harmonic mixer, the integer m, n is set to a value that satisfies the condition that | m ± n | It has the effect that the attenuation characteristics required for the filter (4) can be significantly eased, and does not require the band pass filter (4) of a three-dimensional circuit like a waveguide or a dielectric resonator, and thus is small and monolithic integrated. It is possible to obtain a transmitter having a configuration that is easy to implement.

In the following, problems in practical use of the transmitter according to the present invention and embodiments solving the problems will be described.

It has been shown above that in the above embodiment, the use of the even harmonic mixer (12) suppresses the generation of the frequency 2f _lo ′ inside the mixer. However, the output signal of the normally used local oscillator (3) contains a harmonic component of the frequency f _lo ′, in particular a 2f _lo ′ component. Therefore, the 2f _lo ′ component of the output signal of the local oscillator (3) leaks to the high frequency signal terminal side of the even harmonic mixer (12), reducing the effect of the above-described embodiment. Therefore, as shown in FIG. 5, it is necessary to provide a filter (13), which is a band elimination filter having a center frequency of 2f _lo ′, between the local oscillator (3) and the even harmonic mixer (12). 2f with this filter (13)
It is only necessary to attenuate the _lo 'component, and the cutoff frequencies are 2f _lo ' and f
A low pass filter in the middle of _lo 'or a band pass filter whose center frequency is f _lo ' may be used. Since the filter (13) is not required to have a steep band characteristic, it can be configured with a small microwave integrated circuit.

Next, in the above embodiment, it was shown that the generation of the frequency 2f _lo ′ inside the high frequency transmitter can be suppressed by using the even harmonic mixer (12). However, the frequency f is added to the output signal of the normally used intermediate frequency amplifier (2).
_It contains a harmonic component of _if , especially a 2f _if component. When this frequency 2f _if signal is input to the even harmonic mixer (12),
Similar to the case of the intermediate frequency signal f _if from the equations (7) and (8), the signals f _rf ′ and f _im ′ represented by the following equations are output to the high frequency signal terminal side of the even harmonic mixer (12). .

f _rf ′ = 2f _lo ′ + 2f _if (9) f _im ′ = 2f _lo ′ −2f _if (10) The frequency relationship and power of these signals are shown in FIG. As shown in the figure, when the output signal of the intermediate frequency amplifier (2) includes a signal component of frequency 2f _if , a frequency f _rf ′ component adjacent to the harmonic signal f _rf is output, and in the above embodiment, Reduce the effect of. Therefore, as shown in FIG. 7, a filter (1 which is a band stop filter having a center frequency of 2f _if between the intermediate frequency amplifier (2) and the even harmonic mixer (12) is used.
It is necessary to provide in 4). 2f _if this filter (14)
It suffices if the components are attenuated, and the cutoff frequency is in the middle between 2f _if and f _if , or the center frequency is
A band pass filter such as f _if may be used. Since the filter (14) is not required to have a steep band characteristic,
It can be composed of a small microwave integrated circuit.

In the above-described embodiment of the transmitter of the present invention, the technical idea of the present invention in the case of using a so-called even harmonic mixer in which the above integers m and n are values satisfying the condition that | m + n | is an odd number However, in the transmitter of the present invention, the same applies to the case where a so-called odd harmonic mixer is used in which the above integers m and n are values satisfying the condition that | m + n | is an even number. It goes without saying that the technical idea can be applied and the same effect as when using the even harmonic mixer is obtained. At present, it is considered difficult to configure an odd harmonic mixer with a single non-linear element similar to an even harmonic mixer. And a circuit is used.

In the transmitter according to the present invention as above [Effect of the invention], the frequency mixing means, m = 2,3, when a., The m times the frequency f _lo of the local oscillator wave frequency mf _lo and the intermediate Frequency signal and frequency f _if
And a sum of the frequencies | mf _lo ± f _if | composed of a harmonic mixer for outputting two signals, and the filtering means is any one of the two signals output by the frequency mixing means. was a transmission signal of a frequency f _rf, when the other as shadow image signal frequency f _im, with attenuation characteristics between the frequency f _rf and the frequency f _im is configured to gently changes, included in the local oscillation wave First band-stop filter means for blocking higher harmonics to be supplied to the frequency mixing means, and second band-stop filter for blocking higher harmonics contained in the intermediate frequency signal to supply to the frequency mixing means. Since there is no unnecessary spectrum of the local oscillation wave in the vicinity of the transmission signal frequency, and there is no harmonic of the local oscillation wave and the intermediate frequency signal, the signal wave can be extracted. Relaxed characteristics required for wave means To be done. As a result, the filtering means becomes small, the transmitter can be downsized, and a monolithic structure can be obtained, which is suitable for mass production.

[Brief description of drawings]

FIG. 1 is a structural explanatory view for explaining an embodiment of a transmitter of the present invention, FIG. 2 is a structural view of an embodiment of a transmitter of the present invention, and FIG. 3 is a frequency relation of signals and power. FIG. 4 is a diagram showing the attenuation characteristics required of a bandpass filter, FIG. 5 is a configuration explanatory diagram for explaining another embodiment of the transmitter of the present invention, and FIG. FIG. 7 is a diagram showing a frequency relationship and power, FIG. 7 is a configuration explanatory diagram for explaining still another embodiment of the transmitter of the present invention, FIG. 8 is a configuration diagram of a conventional high frequency transmitter, and FIG. 9 is FIG. 10 is a diagram showing a signal frequency relationship and power, FIG. 10 is a diagram showing an attenuation characteristic required for a bandpass filter, and FIG. 11 is a configuration diagram of a conventional high frequency transmitter using a dielectric resonator. In the figure, (1) is a terminal, (2) is an intermediate frequency amplifier,
(3) is a local oscillator, (4) is a bandpass filter,
(5) is a high frequency amplifier, (6) is a terminal, (7) is an antenna, (8) is a mixer, (9) is a dielectric resonator, (10) is a dielectric substrate, (11) is a movable short-circuit plate, (12) is a mixer,
(13) and (14) are filters. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Akio Iida, 1-1 1-1 Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Electronic Systems Research Laboratory (72) Inventor Shuji Urasaki 5-1-1, Ofuna, Kamakura-shi, Kanagawa No. Mitsubishi Electric Corporation, Electronic Systems Laboratory (56) References JP-A-61-81008 (JP, A)

Claims (1)

[Claims] 1. A local oscillator for generating a local oscillation wave, a frequency mixing means for frequency-mixing an input intermediate frequency signal and the local oscillation wave to generate a transmission signal, and an output from the frequency mixing means for the above Transmission including filtering means for extracting only the transmission signal, high frequency amplification means for receiving the output of the filtering means and performing high frequency amplification, and a transmission antenna for receiving the output of the high frequency amplification means and radiating the transmission signal In the machine, when the frequency of the local oscillation wave is f _lo , the frequency of the intermediate frequency signal is f _if , and the frequency of the transmission signal is f _rf ,
When these frequencies are set so as to satisfy the relationship of f _if <f _lo <f _rf , and the frequency mixing means is m = 2, 3, ..., m of the frequency f _lo of the local oscillation wave. Frequency of doubled frequency mf _lo and frequency f _if of the intermediate frequency signal and sum frequency | mf
a harmonic mixer that outputs two signals of _lo ± f _if |, and the filtering means uses either one of the two signals output by the frequency mixing means as a transmission signal of frequency f _rf , When the other is an image signal of frequency f _im , the frequency f _rf
And a first band-stop filter unit configured to block the harmonics contained in the local oscillation wave and supply the frequency mixing unit, while being configured so that the attenuation characteristic changes gently between the frequency mixing unit and the frequency f _im , A second band-stop filter unit for blocking harmonics contained in the intermediate frequency signal and supplying the same to the frequency mixing unit.