JPH0760977B2 - Multi-frequency common amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common amplifier used in a repeater for automobile telephones, etc., for simultaneously amplifying multi-frequency signals.

[0002]

2. Description of the Related Art In a car telephone repeater, a multi-frequency signal is amplified at the same time. Therefore, in order to avoid intermodulation of a class A amplifier of the repeater, a normal back-off (used in a linear region with a margin from the saturation region of the amplifier) is used. Take enough). For this reason,
An amplifier with high saturation power is required.

For example, the saturation output P ₀ of a repeater for amplifying 100 mW (20 dBm) / wave signal by 100 waves is 60 dBm (= 1 kW) as shown in the following equation when an intermodulation of 60 dB is to be obtained. It becomes a value.

[0004]

This means that the shape of the device and the power consumption increase. However, since it is not economical to obtain such a high output amplifier, the distortion compensation technique is usually adopted.

The above will be described with reference to FIG. The line of is the input / output characteristic when using a small power type amplifier, the line of is the input / output characteristic when using a high power type amplifier, and the line of is the input / output characteristic when using a small power type amplifier having The characteristic of the third-order distortion (two-wave input) is the characteristic of the third-order distortion when the high power amplifier having the input / output characteristic of is used.

There is a feedforward system as a distortion compensation technique, and a block diagram thereof is shown in FIG. In the figure, 1 is a distributor for distributing an input signal, 2 is a variable phase shifter,
3 is a variable attenuator, 4 is a main amplifier, 5 is a delay line, 6 is a distribution combiner, 7 is a variable phase shifter, 8 is a variable attenuator, 9 is an error amplifier, 10 is a delay line, and 11 is a combiner. . The operation principle will be described with reference to FIG. 3. The input signals are mainly 1a-1c-2-
Take the route X of 3-4-6a-6d-10-11b-11c,
The characteristics shown in FIG. 2 are obtained. The input signal is 1a-1d
The distortion component is extracted through the path Y of -5-6b-6c-7-8-9-11a-11c, amplified, and output to 11c. Since this distortion has the polarity opposite to that of the distortion of the input that has passed through the path X, distortion can be reduced (distortion compensation). That is, the route 1a-1c-2-3-4-6a-6c and the route 1a-1d
-5-6b-6c are timed with the delay line 5, and then the variable phase shifter 2 and the variable attenuator 3 are adjusted to cancel the input signal to extract the distortion component, and the path 6d-10-11b- After adjusting the delay times of 11c and the paths 6c-7-8-9-11a-11c with the delay line 10, the variable phase shifter 7 and the variable attenuator 8 are adjusted to cancel the distortion components.

FIG. 3B shows the main places (6a, 6b, 6c, 6d, 11a,) when a two-frequency signal is input to the input 1a.
It is an explanatory view showing the spectrum of 11c) including polarity. The horizontal axis represents frequency and the vertical axis represents level. For reference, Fig. 4 shows the amount of improvement in distortion compensation due to amplitude deviation and phase deviation (extracted from RCS90-4 ultra-low distortion multi-frequency common amplifier for mobile communication).

In the above conventional circuit, the delay lines 5 and 10 of FIG. 3 (a) normally use HF cables, but the routes 1a-1c- to 6a-6c or the lines 6c to 11a-11 are used.
The delay time of c is about 10 nsec although it depends on the structure. 900M
Calculating the length of the HF cable in the Hz band, delay time = length / (cable shortening rate x speed of light), so length = 0.
65 × 3 × 10 ⁸ × (10 × 10 ^-9 ) = 1.85 m. The loss and volume when using the cables with the above lengths are as shown in the table for three general types of cables. However, the volume is expressed by the following equation, assuming that the bending radius r is 10 times as large as the diameter of the jacket, and that it is wound in a columnar shape.

[0010]

[0011]

[Table 1]

[0012]

As described above, in the conventional structure, when a thin cable is used, the loss becomes large and the effect of distortion compensation becomes small, and the thick cable has a small loss but a small shape. Since it is large, it cannot be mounted on a small device.

The object of the present invention is to solve the above problems,
An object is to provide a compact multi-frequency common amplifier with low loss.

[0014]

A multi-frequency common amplifier according to the present invention includes a distributor for distributing an input signal, a first variable phase shifter cascaded to one output terminal of the distributor, and a first variable phase shifter. A variable attenuator and a main amplifier, a first delay flat filter connected to the other output terminal of the distributor, and a divider for combining the output of the main amplifier and the output of the first delay flat filter. A combiner, a second variable phase shifter, a second variable attenuator, an error amplifier connected in series to one output terminal of the distribution combiner, and a second output connected to the other output terminal of the distribution combiner. And a synthesizer for synthesizing the output of the error amplifier and the output of the second delay flat filter to cancel the distortion component and output a distortion-compensated amplified signal. It is characterized by that.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. Although it is almost the same as the conventional example of FIG.
The delay line 5 and the delay line 10 in (a) are connected to the delay flat filter 15,
It is replaced with 16.

The miniaturization and low loss that are advantages when using the flat delay filters 15 and 16 will be described. As an example, the case where this delay flat filter is manufactured at 900 MHz is shown. Usually, the filter design uses a normalized frequency. 5 and 6 show the characteristics of the attenuation amount and the delay time with respect to the normalized frequency Ω of the flat delay type filter (Handboo
(Extracted from k of Filter Synthesis). That is, the normalized frequency Ω is expressed by Eq. (1) in the case of a bandpass filter. However, f ₀ : center frequency Δf: bandwidth

Distortion components are extracted and canceled by adjusting the variable attenuators 3 and 8 shown in FIG. 3A or FIG. 1. As an example, if the amplitude deviation is 0.4 dB, a distortion compensation amount of 20 dB can be obtained. So
When Ω with an amplitude deviation of 0.4 dB is obtained from Fig. 5, a flatness of 0.4 dB or less is obtained when Ω = 0.37 or less. Therefore, f ₀
= 932.5MHz, f = 920MHz or 945MHz, the bandwidth Δf≈67MHz from equation (1).

The delay time τ is shown by the following equation (2). In equation (2), from FIG. 6, when order n = 4, σ (x)
= 2.1 sec, the delay time τ = 2.1 / (3.14 × 67 ×
10 ⁶ ) ≈10nsec.

Further, from FIG. 6, there is no delay time deviation when Ω = 0.37 or less. The insertion loss L of this filter (particularly the flat delay filter 16 of FIG. 1) is given by the following equation. However, Q _U : No load of the semi-coaxial resonator Q n: Order Therefore, if order n = 4, Q _MIN is given by the following equation (6). Therefore, if you choose a 10 mm square resonator,
Since Q _U = 800 is obtained, the loss is L from Eqs. (3) and (4).
It is <0.38 dB and low loss. The size is 10L × 40W
× 15H (mm ³ ) = 6 (cc), which is very small.

Since the flat delay filter 15 shown in FIG. 1 does not cause a significant loss, the size of the delay flat filter 15 is 5L × 20W × by using a small semi-coaxial resonator and lowering the unloaded Q _U.
It becomes about 15H = 1.5 (cc), which enables downsizing.

[0021]

As described above in detail, by replacing the delay line with the delay flat filter according to the present invention, the delay flat filter 15 of FIG. 1 becomes much smaller than the conventional delay line 5. Also, the flat delay filter 16 has a low loss and a small size as compared with the conventional HF cable, so that the practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram.

FIG. 3 is a block diagram of a conventional circuit and a spectrum of each part.

FIG. 4 is a characteristic diagram showing improvement in distortion compensation.

FIG. 5 is a characteristic diagram.

FIG. 6 is a characteristic diagram.

[Explanation of symbols]

 1 distributor 2 variable phaser 3 variable attenuator 4 main amplifier 5 delay line 6 distribution combiner 7 variable phaser 8 variable attenuator 9 error amplifier 10 delay line 11 combiner 15 delay flat filter 16 delay flat filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Sera 2-3-13 Toranomon, Minato-ku, Tokyo International Electric Co., Ltd. (72) Inventor Mikio Takano 2-3-13 Toranomon, Minato-ku, Tokyo International Electric Co., Ltd. (72) Inventor, Sanami Kanemi, 2-13-13 Toranomon, Minato-ku, Tokyo International Electric Co., Ltd. (72) Inventor, Masaki Sudo, 2-3-13 Toranomon, Minato-ku, Tokyo International Electric Ki Co., Ltd. (72) Inventor Noriyuki Kagaya 2-3-13 Toranomon, Minato-ku, Tokyo Kokusai Denki Co., Ltd. (72) Inventor Hitoshi Odate 1-6, Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Co., Ltd. (72) Inventor Muko Keiso 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A distributor for distributing an input signal, and a first variable phase shifter cascade-connected to one output terminal of the distributor,
A first variable attenuator and a main amplifier, a first delay flat filter connected to the other output terminal of the distributor, an output of the main amplifier and an output of the first delay flat filter. A distributor / combiner for combining, a second variable phase shifter, a second variable attenuator, an error amplifier connected in cascade to one output terminal of the distributor / combiner, and the other output terminal of the distributor / combiner A second delay flat filter, and a combiner for combining the output of the error amplifier and the output of the second flat delay filter to cancel the distortion component and output a distortion-compensated amplified signal. , A feed-forward type distortion-compensated multi-frequency common amplifier which simultaneously amplifies multi-frequency input signals.