WO2006067899A1

WO2006067899A1 - Diversity receiver

Info

Publication number: WO2006067899A1
Application number: PCT/JP2005/017058
Authority: WO
Inventors: Ryohei Nishizaki; Tadashi Sakaguchi; Mitsuhiro Shimozawa
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2004-12-24
Filing date: 2005-09-15
Publication date: 2006-06-29
Also published as: JP2006180419A

Abstract

A diversity receiver (10) is provided with branches (A, B) corresponding to a plurality of antennas (11, 12) arranged spatially separated from each other, and synthesizes and outputs a signal received by each branch. The noise levels of the signals received by each branch are permitted to be equal by controlling RF AGCs (21, 31) and IF AGCs (25, 35) by level detectors (26, 36), and then IF signals between the branches are synthesized.

Description

Specification

Diversity receiver

Technical field

The present invention relates to a diversity receiver, and more particularly to a diversity receiver that can be used in a mobile body such as a vehicle and can improve a signal-to-noise ratio (SZN ratio) after reception signal synthesis.

Background art

[0002] In general, a diversity receiver is provided with a plurality of antennas, and the received signals received by these antennas are combined in the baseband! / Speak. As a combining method in the diversity receiver, for example, an equal gain combining method for combining a plurality of received signals with a constant power in a baseband band and a signal-to-noise ratio (SZN ratio) in a plurality of received signals There is a maximum-ratio combining method that weights (weights) and keeps the combined SZN in good condition.

Conventionally, as a diversity receiver using the maximum ratio combining method, for example, first and second bases receive signals received by first and second receiving antennas by first and second receivers, respectively. The first and second receiver noise components (first and second noise components) are extracted by the first and second band-pass filters as the band signal, and the first and second noise components are extracted. Is synthesized.

[0004] Thereafter, the synthesized noise component is amplified by the common amplifier, and the first and second noise components are gain-controlled by the first and second auxiliary amplifiers using the automatic control gain voltage of the common amplifier, A DC voltage proportional to the logarithm of the output of the first and second auxiliary amplifiers is generated by the first and second control voltage generators and given to the first and second maximum ratio combining control circuits, respectively. There is one in which ratio synthesis is performed (for example, see Patent Document 1).

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 63-1222 (pages 3 to 4, Fig. 1)

[0006] Since the diversity receiver using the conventional maximum ratio combining method is configured as described above, the SZN ratio after combining the received signals can be improved. The problem is that the signal level and noise level must be detected for each antenna, and as a result, the control for synthesizing the received signal with force will become complicated if the circuit configuration becomes complicated. there were.

[0007] On the other hand, in a diversity receiver using the equal gain combining method, although the circuit configuration becomes simple, if the difference in the SZN ratio between antennas increases, the received signal with the poor SZN ratio dominates. As a result, the SZN ratio after synthesis deteriorates and a good reception state cannot be maintained.

[0008] The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a diversity receiving apparatus that has a simple circuit configuration and can maintain a good SZN ratio after synthesis. .

Disclosure of the invention

[0009] A diversity receiving apparatus according to the present invention includes branches corresponding to a plurality of antennas arranged spatially separated from each other, and synthesizes and outputs received signals received for each branch. The diversity receiving apparatus combines the level-adjusted output signal with a level-adjusted output signal by setting the noise level in the received signal received for each branch to the same level between the branches, and the synthesized signal by combining the level-adjusted output signal. And a synthesizing means.

[0010] According to the present invention, before synthesizing the received signal received for each branch, the noise level (noise floor level) of the received signal is set to the same level between the branches to obtain a level-adjusted output signal. Since it is configured to synthesize these level-adjusted output signals, the signal-to-noise ratio (SZN ratio) after synthesis can be improved, and an excellent reception state can be maintained.

Brief Description of Drawings

FIG. 1 is a block diagram showing an example of a diversity receiver according to Embodiment 1 of the present invention.

2 is a flowchart for explaining the operation of the diversity receiver shown in FIG.

[Fig. 3] RF input level of the level detector used in the diversity receiver shown in Fig. 1 FIG. 4 is a diagram showing control voltage characteristics.

4 is a diagram showing the control voltage attenuation (gain) characteristics of the RF AGC used in the diversity receiver shown in FIG.

FIG. 5 is a diagram showing a gain characteristic of a control voltage of IF AGC used in the diversity receiver shown in FIG. 1.

6 is a diagram for explaining the IF AGC output in branch A shown in FIG. 1. (a) is a diagram showing the RF input level, (b) is a diagram showing the RF AGC output level, and (c) is a diagram. It is a figure which shows IF AGC output level.

7 is a diagram for explaining the IFAGC output in branch B shown in FIG. 1. (a) is a diagram showing the RF input level, (b) is a diagram showing the RF AGC output level, and (c) is an IF It is a figure which shows an AGC output level.

FIG. 8 is a diagram showing a combined output level after combining the IF output levels shown in FIGS. 6 (c) and 7 (c).

圆 9] It is a diagram for explaining an example of the SZN ratio when equal gain synthesis is performed. (A) shows the IFAGC output level in branch A, and (b) shows the IFAGC output level in branch B. FIG. 4C is a diagram showing a combined output level after combining.

10 is a diagram for explaining an example of the SZN ratio in the diversity receiver shown in FIG. 1. (a) shows the IFAGC output level in branch A, and (b) shows the IFAGC output level in branch B. FIG. 4C is a diagram showing a combined output level after combining.

圆 11] It is a diagram for explaining another example of the SZN ratio when equal gain synthesis is performed. (A) shows the IFAGC output level in branch A, (b) shows the IF AGC output in branch B FIG. 5C is a diagram showing a combined output level after combining.

12 is a diagram for explaining another example of the SZN ratio in the diversity receiver shown in FIG. 1. (a) is a diagram showing an IFAGC output level in branch A, and (b) is a branch.

Fig. 7 is a diagram showing the IFAGC output level in B, and (c) is a diagram showing the synthesized output level after synthesis.

[13] Block diagram showing an example of a diversity receiver according to the second embodiment of the present invention. It is.

FIG. 14 is a diagram showing control voltage attenuation (gain) characteristics of the RF AGC used in the diversity receiver shown in FIG. 13.

FIG. 15 is a diagram showing a control voltage-gain characteristic of IF AGC used in the diversity receiver shown in FIG. 13.

FIG. 16 is a block diagram showing an example of a diversity receiver according to Embodiment 3 of the present invention.

FIG. 17 is a block diagram showing a configuration of a computing unit (CPU) shown in FIG.

FIG. 18 is a diagram showing RF input level-control voltage characteristics of a level detector used in the diversity receiver shown in FIG. 16.

FIG. 19 is a diagram showing control voltage attenuation (gain) characteristics of the RF AGC used in the diversity receiver shown in FIG. 16.

20 is a diagram showing a control voltage-gain characteristic of IF AGC used in the diversity receiver shown in FIG.

FIG. 21 is a flowchart for explaining the operation of the diversity receiver shown in FIG.

FIG. 22 is a block diagram showing an example of a control system used in a diversity receiver according to Embodiment 4 of the present invention.

FIG. 23 is a diagram showing an example of a data table stored in the information storage unit shown in FIG.

24 is a flowchart for explaining the operation of the control system shown in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in order to explain the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.

First, referring to FIG. 1, the illustrated diversity receiver 10 is described as being mounted on a moving body such as a vehicle and receiving AM radio broadcast waves and FM radio broadcast waves (hereinafter simply referred to as broadcast waves). However, the same applies to receivers that receive digital broadcast waves. Can be applied. The receiving device 10 has a plurality of receiving antennas (two in the illustrated example) 11 and 12, and these receiving antennas 11 and 12 are arranged spatially separated from each other (hereinafter referred to as receiving antenna 11). This system is sometimes called branch A, and the system of receiving antenna 12 is called branch B).

[0013] Corresponding to antenna 11, that is, corresponding to branch A, RF automatic gain control circuit (RF AGC: first gain adjusting means) 21, RF circuit 22 (RF circuit 22 is amplifier 22a and Z up-converter 22b), distributor 23, intermediate frequency (IF) circuit 24 (IF circuit 24 has filter 24a, amplifier 24b, and down / up converter 24c), IF AGC (Second gain adjusting means) 25 and a level detector (level detector) 26 are provided.

[0014] Similarly, RF AGC31, RF circuit 32 (RF circuit 32 includes amplifier 32a and down / up converter 32b), distribution corresponding to antenna 12, that is, corresponding to branch B 33, IF circuit 34 (IF circuit 34 has a filter 34a, an amplifier 34b, and a down-Z up-converter 34c), an IF AGC 35, and a level detector 36.

[0015] IF AGCs 25 and 35 are connected to an IF synthesizer (synthesizing means) 41, and IF AGCs 25 and 35 are connected to a phase difference detector (phase difference detecting means) 42, and the phase difference detector 42 is a phase difference detector 42. Connected to the phase shifter (phase adjusting means) 43, and the phase shifter 43 adjusts the down Z up converter 34c as will be described later (the phase shifter 43 may adjust the down Z up converter 24c). . Distributors 23 and 33 are connected to level detectors 26 and 36, respectively.

[0016] Referring also to Fig. 2, now, paying attention to antenna 11, when a broadcast wave is received as a received signal by antenna 11, that is, when a signal is input to branch A (step ST1). The RF AG C21 adjusts the signal level of the received signal in accordance with the first control voltage given from the level detector 26 (the first gain adjusted signal (step ST2)). The output of RF AG C21 is amplified and down (up) converted in RF circuit 22 (step ST3) and then distributed by distributor 23 (step ST4) to level detector 26 and IF circuit 24, respectively. Given. [0017] The level detector 26 detects the signal level as the first RF input level according to the output of the RF circuit 22 (hereinafter referred to as the first RF output), and according to the first RF input level. A first control voltage (signal level control voltage) is generated (step ST5), and the first control voltage is applied to RF AGC21 and IF AGC25. On the other hand, in the IF circuit 24, the first RF output is filtered and then amplified, further down (up) converted (step ST6), and used as the first IF signal, and this first IF signal is sent to the IF AGC25. give. Then, IF AGC 25 adjusts the signal level of the first IF signal in accordance with the first control voltage (the first gain-adjusted signal (that is, the level-adjusted signal) (step ST7)).

[0018] Similarly, when a broadcast wave (received signal) is received by antenna 12, that is, when a signal is input to branch B (step ST8), RF AGC 31 is supplied from level detector 36. Adjust the signal level of the received signal according to the control voltage of 2 (the first gain adjusted signal (step ST9)). The output of the RF AGC 31 is amplified and down (up) converted in the RF circuit 32 (step ST10), then distributed by the distributor 33 (step ST11), and supplied to the level detector 36 and the IF circuit 34, respectively. .

[0019] The level detector 36 detects the signal level as the second RF input level according to the output of the RF circuit 32 (hereinafter referred to as the second RF output), and according to the second RF input level. A second control voltage (signal level control voltage) is generated (step ST12), and the second control voltage is applied to RF AGC31 and IF AGC35. On the other hand, in the IF circuit 34, the second RF output is filtered and then amplified, further down (up) converted (step ST13), and used as the second IF signal, which is supplied to the IF AGC 35. . Then, IF AGC 35 adjusts the signal level of the second IF signal in accordance with the second control voltage (the second gain-adjusted signal (that is, the level-adjusted signal) (step ST14)).

[0020] The first and second IF signals are supplied to an IF synthesizer 41 and also to a phase difference detector 42. The phase difference detector 42 detects the phase difference between the first and second IF signals, generates a phase control voltage corresponding to the phase difference (step ST15), and applies this phase control voltage to the phase shifter 43. Phase shifter 43 controls the phase of the input signal from the local oscillator input to down-Z upconverter 34c (step ST16), and aligns the phase of the second IF signal to the order of the first IF signal. On the other hand, IF synthesizer 41 synthesizes the first and second IF signals (signal level synthesis: step ST17) and outputs an IF synthesized signal (step ST18). The output from the IF synthesizer 41 is given to a demodulation circuit (not shown) at the subsequent stage, and after being demodulated here, an acoustic signal is outputted as a loudspeaker (not shown).

Next, the operation will be described.

Referring to FIGS. 1 and 3, now, as shown in FIG. 3, the level detectors 26 and 36 each have an RF input level-control voltage characteristic indicating the relationship between the RF input level and the control voltage. Is set, and level detectors 26 and 36 output the first and second control voltages according to the first and second RF input levels, respectively. Here, RF AGC21 and 31 have the control voltage (RF AGC control voltage) attenuation (gain) characteristics shown in Fig. 4, and IF AGC25 and 35 have the control voltage (IF AGC control voltage) attenuation characteristics shown in Fig. 5. It shall have

[0023] Here, referring also to FIG. 6, the input level of RF AGC2 1 is 60dBm (noise level is 80dBm: S / N) as shown in FIG. 6 (a). Ratio = 20 dB) (assuming that the gains of the RF circuits 22 and 32 and IF circuits 24 and 34 are OdB), the level detector 26 from Fig. 3 shows that for the first RF input level = 60 dB The first control voltage = 2.0V is output to RF AGC21 and IF AGC25.

[0024] In RF AGC21, when the first control voltage = 2.0V is applied, the attenuation is 10dB.

(See Fig. 4) AGC of the received signal is performed. In other words, as shown in Fig. 6 (b), the output of RF AGC21 is attenuated by 10 dB, and its output level becomes 70 dB (noise level becomes 90 dB). In IF AGC25, when the first control voltage = 2.0 V is applied, the gain is set to 10 dB (see Fig. 5), and AGC of the first IF signal is performed. In other words, as shown in Fig. 6 (c), the output of IF AGC25 is calculated with a gain gain of 10 dB, and its output level becomes -60 dB (noise level becomes 80 dB).

On the other hand, as shown in FIG. 7 (a), assuming that the input level of the RF AGC 31 in branch B is one 40 dBm (noise level is 80 dBm: S / N ratio = 40 dB), The bell detector 36 outputs the second control voltage = 1.0V for the second RF input level = 40 dB, and applies it to the RF AGC31 and IF AGC35. In RF AGC31, the second control power When pressure = 1. OV is applied, AGC of the received signal is performed with attenuation = 30 dB (see Fig. 4).

That is, as shown in FIG. 7B, the output of the RF AGC 31 is attenuated by 30 dB, and the output level becomes 170 dB (the noise level becomes 1 lOdB). In IF AGC35, when the second control voltage = 1. OV is applied, the gain is set to 30 dB (see Fig. 5), and the AGC of the second IF signal is performed. In other words, as shown in Fig. 7 (c), the output of IF AGC35 is gained by 30 dB, and the output level becomes 140 dB (noise level becomes 80 dB).

[0027] The output of the IF AGC 25 (first IF signal) and the output of the IF AGC 35 (second IF signal) are given to the IF combiner 41 for synthesis. At this time, since the noise floors of the first and second IF signals are the same, even when equal gain synthesis is performed, synthesis can be performed without degrading the SZN ratio. In the examples shown in Fig. 6 and Fig. 7, when the synthesis is performed by the IF synthesizer 41, as shown in Fig. 8, the signal level after synthesis becomes 39.2 dBm (noise level is 1 77 dBm), and the SZN ratio Is 37.8 dBm (note that if the equal gain synthesis is performed at the RF input level shown in Fig. 6 (a) and Fig. 7 (b), the SZN ratio is 26 dB).

[0028] As described above, in branches A and B, the IF AGC is controlled using the first and second control voltages (that is, the RF AGC control voltage) (RF AGC attenuation = IF AGC gain), when the first and second IF signals are synthesized, the SZN ratio after synthesis can be improved as the noise levels are equalized (RF AG C's gain). Attenuation + a (Constant value) = IF Even if the gain of AGC is set, the noise level when combining the first and second IF signals can be made uniform).

[0029] When equal gain combining is performed, as shown in Figs. 9 (a) and 9 (b), the signal levels in branches A and B are aligned before combining (in branch A, the signal level is = 70 dBm, noise level = — 76 dBm, SZN ratio = 6 dB, in branch B, signal level = 70 dBm, noise level = — 80 dBm, SZN ratio = 10 dB), and the combined S ZN ratio is shown in Figure 9 (c) Thus, it becomes 10.5dB.

On the other hand, when the RF AGC 21 and 31 and the IF AGC 25 and 35 are controlled as described above, the noise level (noise floor) in the branches A and B before synthesis is shown in FIGS. 10 (a) and 10 (b). ) Is set to 80 dBm, the S / S after combining by IF combiner 41 The N ratio is improved to 11.2 dB as shown in Fig. 10 (c).

Similarly, in the example shown in FIGS. 11 (a) and 11 (b), when equal gain synthesis is performed, the result of the signal levels in branches A and B being aligned before synthesis (branch A Signal level = —70 dBm, noise level = —80 dBm, SZN ratio = 10 dB, and in branch B, signal level = —70 dBm, noise level = 100 dBm, SZN ratio = 30 dB), SZN after synthesis The ratio is 16. OdB as shown in Fig. 11 (c).

On the other hand, when RF AGC 21 and 31 and IF AGC 25 and 35 are controlled as described above, as shown in FIGS. 12 (a) and 12 (b), the noise levels in branches A and B are reduced before synthesis. As a result of aligning with lOOdBm, the SZN ratio after synthesis by the IF synthesizer 41 is improved to 27.8dB as shown in Fig. 12 (c).

[0033] As described above, according to the first embodiment, since the noise floor is set to the same level for each branch and then the synthesis is performed, the SZN ratio after the synthesis can be improved. There are fruits.

[0034] According to the first embodiment, the first control voltage applied to the RF AGC 21 is applied to the IF AGC 25, and the second control voltage applied to the RF AGC 31 is applied to the IF AGC 35, so that the noise floors between the branches are made uniform. As a result, the S / N ratio after synthesis can be improved with a simple configuration.

Embodiment 2.

Next, a receiving apparatus according to the second embodiment of the present invention will be described with reference to FIG. In FIG. 13, the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The illustrated receiver 10 includes level converters (control voltage level adjusting means) 51 and 52, and level detectors 26 and 36 are connected to IF AGCs 25 and 35 via level shifts 51 and 52, respectively. ing.

Incidentally, in FIGS. 4 and 5 described in the first embodiment, the RF AGC control voltage attenuation characteristic and the IF AGC control voltage-gain characteristic have been described as having the same slope 1S, that is, RF AGC 21 and 31. Although IF AGC25 and 35 have been described as having the same characteristics, RF AGC21 and 31 may be different from IF AGC25 and 35 in practice. For example, as shown in FIGS. 14 and 15, the slope of the straight line indicating the RF AGC control voltage-attenuation characteristic may be different from the slope of the straight line indicating the IF AGC control voltage-gain characteristic (example shown in the figure). Then, the slope of the straight line indicating the RF AGC control voltage-attenuation characteristic is 1Z2 of the slope of the straight line indicating the IF AGC control voltage-gain characteristic.

[0038] When the characteristics are different in this way, the RF detector AGC21 and IF

When the first control voltage is applied to AGC25 and the second control voltage is applied to RF AGC31 and IF AGC35 from level detector 36, respectively, the first and second IF signals output from IF AGC25 and 35 respectively. The noise level cannot be made uniform, and as a result, the SZN ratio after synthesis cannot be improved.

[0039] For this reason, as described above, level change ^^ 51 is inserted, and the control voltage applied to IF AGC25 is level-converted by level converter 51, so that the attenuation in RF AGC21 and the gain in IF AGC25 are To be equal. In other words, when RF A GC21 and IF AGC25 have the characteristics shown in FIGS. 14 and 15, the level change ^ 51 gives the first control voltage 1Z2 to IF AGC25. As a result, the attenuation in RF AGC21 and the gain in IF AGC25 are equal.

[0040] Similarly, the control voltage applied to IF AGC 35 is level-converted by level converter 52, and RF

Attenuation at AGC31 and IF AGC35 gain should be equal. In other words, when RF AGC31 and IF AGC35 have the characteristics shown in FIG. 14 and FIG. 15, level change ^ 52 gives the IF AGC 35 1/2 the second control voltage, As a result, the attenuation at RF AGC31 and the gain at IF AGC35 are equal. Therefore, the noise levels of the first and second IF signals output from IF AGC 25 and 35, respectively, are aligned, and the S / N ratio after synthesis can be improved.

[0041] As described above, according to the second embodiment, the RF AGC 21 and 31 and the IF AGC 25 and 35 have different control voltage-gain (attenuation) characteristics when the first and second control functions are different. Since the voltage is level-converted according to the control voltage-gain characteristic and applied to IF AGC25 and 35, respectively, the noise floors of the first and second IF signals can be aligned before synthesis. This has the effect of improving the SZN ratio.

[0042] Embodiment 3. Next, a receiving apparatus according to the third embodiment of the present invention will be described with reference to FIG. In FIG. 16, the same components as those in FIG. In the examples shown in Fig. 4, Fig. 5, Fig. 14 and Fig. 15, the RF input level control voltage characteristics, RF AGC control voltage attenuation characteristics, and IF AGC control voltage gain characteristics change linearly (linearly). As described above, the RF AGC control voltage—attenuation characteristic and the IF AGC control voltage—gain characteristic may change nonlinearly (curved).

[0043] In such a case, even if the first and second control voltages are level-converted using the level change and 52 in the second embodiment and then applied to the IF AGCs 25 and 35, the RF A GCs 21 and 31 It is difficult to equalize the attenuation at IF and the gain at IF AGC25 and 35. For this reason, the receiving apparatus 10 shown in the figure is provided with a computing unit (CPU) 53, and this CPU 53 is connected to the outputs of the level detectors 26 and 36, and is connected to the RF AGCs 21 and 31 and the IF AGCs 25 and 35. Control RF AGC 21 and 31 and IF AG C25 and 35 as described below.

Referring to FIG. 17, the CPU 53 has a voltage detection unit 53a, an information storage unit (storage unit) 53b, and an output voltage calculation unit 53c. The first output from the level detectors 26 and 36 is the first. The branch A side RF AGC control voltage and IF AGC control voltage are generated based on the second control voltage and the branch B side RF AGC control voltage and IF AGC control voltage are output.

[0045] Now, it is assumed that the level detectors 26 and 36 have the RF input level control voltage characteristics shown in FIG. 18, respectively, and the RF AGC 21 and 31 have the RF AGC control voltage attenuation characteristics shown in FIG. IF AGC25 and 35 each have the IF AGC control voltage-gain characteristics shown in FIG. 17 stores the RF input level control voltage characteristics, RF AGC control voltage attenuation characteristics, and IF AGC control voltage-gain characteristics shown in FIGS. 18 to 20 as a detector data table. Has been.

Referring to FIGS. 16 to 21, CPU 53 obtains the first and second control voltages by voltage detector 53a (step ST19), and detects the first and second control voltage values. The detection result is passed to the output voltage calculation unit 53c. Now, the RF input (level) to level detectors 26 and 36 Assuming that the bell detector input level is -60 dBm and -40 dBm, respectively, the attenuation when the RF input level = --60 dBm is 10 dB, and the attenuation when the RF input level = -40 dBm is 30 dB. As shown in FIG. 18, the level detectors 26 and 36 output the first control voltage = 1.OV and the second control voltage = 0.4V, respectively. That is, the voltage detection unit 53a outputs the detection result indicating the branch A = l.0V and the branch B = 0.4V.

[0047] The output voltage calculation unit 53c refers to the detector data table in the information storage unit 53b based on the detection result (step ST20), and first corresponds to branch A = l. OV and branch B = 0.4 V. Know the RF input level from Figure 18. Subsequently, the attenuation corresponding to the branch A side RF input level and the branch B side RF input level is obtained (here, the branch A side RF input level = —60 dBm, the branch B side RF input level = —40 dBm, The output voltage calculation unit 53c sets the attenuation on the branch A side = 10 dB and the attenuation on the branch B side = 30 dB, and the detector data table contains information indicating the relationship between the RF input and the attenuation. And).

[0048] The output voltage calculator 53c refers to the detector data table (see Figure 19: RF AGC control voltage (step ST21)), and the branch A side RF AGC control voltage corresponding to the branch A side attenuation = 10 dB. = 2. Obtaining IV, branch B side RF AGC control voltage = 1.7V corresponding to branch B side attenuation = 30dB, branch A side RF AGC control voltage = 2. IV and branch B side RF AGC Apply control voltage = 1.7V to RF AGC2 1 and 31 respectively (step ST22).

Similarly, the output voltage calculation unit 53c refers to the detector data table (see FIG. 20: 1 F AGC control voltage (step ST23)), gains the branch A side attenuation = 10 dB and gains this gain. Branch A side IF AGC control voltage = 0.2V corresponding to the branch B side RF AGC control voltage = 0.80V corresponding to this gain with the branch B side attenuation = 30dB as the gain. A side IF AGC control voltage = 0.2V and branch B side RF AGC control voltage = 0.80V are applied to IF AGC25 and 35, respectively (step ST2 4). Then, after performing step ST24, the process returns to step ST19.

[0050] By doing this, RF input level control voltage characteristics, RF AGC control voltage attenuation Even if at least one of the characteristics and the IF AGC control voltage gain characteristic changes in a curve, the attenuation in RF AGC 21 and 31 and the gain in IF AGC 25 and 35 can be made equal, and before synthesis. As a result, the SZN ratio after synthesis can be improved.

Note that the CPU 53 does not include the information storage unit 53b, and an external information storage device (not shown) is stored in the CPU 53 so that the above-described detector data table is stored in the external information storage device. May be. In the third embodiment, the voltage detector 53a and the output voltage calculator 53c function as control voltage level adjusting means.

As described above, according to the third embodiment, the RF input level—control voltage characteristics change in a curve in level detectors 26 and 36, and further, RF AGC 21 and 31 and IF A GC 25 and 35 Even when the control voltage-gain (attenuation) characteristics change in a curve, the noise floor of the first and second IF signals can be aligned before synthesis, resulting in improved SZN ratio after synthesis. If you can, it has a positive effect.

[0053] Embodiment 4.

Next, a receiving apparatus according to the fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, for example, the receiving apparatus 10 shown in FIG. 1 is used, the outputs of the level detectors 26 and 36 are given to the RF AGCs 21 and 31, respectively, and the outputs of the level detectors 26 and 36 are 22 is connected to the CPU 54 shown in FIG. 22, and the output of the CPU 54 is connected to the IF AGCs 25 and 35.

The CPU 54 includes a voltage difference calculation unit (voltage difference calculation unit) 54a, an information storage unit 54b, and a noise floor level difference detection determination unit (noise level difference detection determination unit) 54c. The information storage unit 54b includes As shown in FIG. 23, a data table representing the relationship between the voltage difference and the noise floor level difference is stored. Referring also to FIG. 24, the voltage difference calculation unit 54a acquires the first and second control voltages (step ST25), and obtains the difference between the first and second control voltages as a voltage difference (step ST26). The voltage difference is given to the noise floor level difference detection determination unit 54c.

[0055] The noise floor level difference detection determination unit 54c refers to the data table stored in the information storage unit 54b, and detects the noise floor level difference corresponding to the voltage difference (step S). Subsequently, it is determined whether or not the noise floor level difference is not less than a preset threshold value (for example, 10 dB) (step ST28).

[0056] If the noise floor level difference is equal to or greater than the threshold as a result of this determination, the noise floor level difference detection determination unit 54c compares the branch A side RF input level with the branch B side RF input level. (Step ST29) If the branch A side RF input level is lower than the branch B side input level, the gain of the IF AGC25 corresponding to branch A is minimized, assuming that branch A becomes a degradation factor of the SZN ratio after synthesis. The gain control voltage is supplied to IF AGC25 as the branch A side IF AGC control voltage. In other words, the noise floor level difference detection determination unit 54c changes the IF AGC control voltage on the branch A side to the maximum value (minimum gain control voltage) (step ST30) and minimizes the gain of IF AGC25. Then, the noise floor level difference detection / determination unit 54c gives the second control voltage as the branch B side IF AGC control voltage to the branch A side IF AGC 35.

As a result, when the first and second IF signals are combined by the IF combiner 41 (FIG. 1), the gain (that is, the signal level) of the first IF signal is minimized. As a result, since the first IF signal is not synthesized, branch A, which causes SZN ratio degradation, is ignored, and SZN ratio degradation after synthesis can be prevented.

[0058] When the branch A side RF input level and the branch B side RF input level are compared, the first and second control voltages are used, and the first control voltage> the second control voltage. When the branch A side RF input level is less than the branch B side RF input level, and the first control voltage ≤ second control voltage, the branch A side RF input level ≥ branch B side RF input level. It will be judged as a level.

[0059] On the other hand, in step ST29, if the branch A side RF input level ≥ the branch B side RF input level, the noise floor level difference detection judgment unit 54c determines the SZN ratio of the branch B after the synthesis. As a cause of deterioration, a control voltage that minimizes the gain of IF AGC35 corresponding to branch B is applied to IF AGC35 as the branch A side IF AGC control voltage. That is, the noise floor level difference detection determination unit 54c changes the IF AGC control voltage on the branch B side to the maximum value (step ST31), and minimizes the gain of IF AGC35. Then, the noise floor level difference detection determination unit 54c performs the first control on the IF AGC 25 on the branch A side. The control voltage is given as the branch A side IF AGC control voltage.

As a result, when the first and second IF signals are combined by the IF combiner 41 (FIG. 1), the gain (that is, the signal level) of the second IF signal is minimized. As a result, since the second IF signal is not synthesized, branch B, which is the cause of SZN ratio degradation, is ignored, and SZN ratio degradation after synthesis can be prevented.

[0061] In step ST28, if the noise floor level difference is less than the threshold, the noise floor level difference detection determination unit 54c assigns the first and second control voltages to the branch A side IF AG C control voltage and branch B, respectively. Is applied to IF AGC 25 and 35 as the IF IFGC control voltage (step ST32) and the noise floor level before synthesis is made uniform, and then the IF synthesizer 41 synthesizes the first and second IF signals.

In the example shown in FIG. 22, the CPU 54 has a built-in voltage difference calculation unit 54a. However, the voltage difference calculation unit 54a is made independent as a voltage difference calculation circuit, and the first and second voltage difference calculation circuits are used. The second control voltage may be received and the output of the voltage difference calculation circuit may be given to the CPU 54.

[0063] As described above, according to the fourth embodiment, the difference in control voltage between branches is obtained as a voltage difference, and the difference in noise level between branches is obtained as a noise level difference according to the voltage difference. When the noise level difference is greater than or equal to a predefined threshold, the IF AGC gain is minimized in the branch that causes degradation of the signal-to-noise ratio after synthesis. There is an effect that can be prevented. Industrial applicability

As described above, the diversity receiver according to the present invention is suitable for maintaining a good reception state by simplifying the circuit configuration and maintaining a good SZN ratio after synthesis.

Claims

The scope of the claims

[1] A branch corresponding to each of a plurality of antennas arranged spatially apart from each other is provided.

In the diversity receiver that synthesizes and outputs the received signals received for each branch,

Level adjustment means for setting the noise level in the received signal received for each branch to the same level between the branches and making the level adjusted output signal;

A diversity receiving apparatus comprising: combining means for combining the level-adjusted output signals into a combined signal.

[2] The level adjusting means includes first gain control means for adjusting the gain of the received signal received for each branch to obtain a first gain adjusted signal;

A second gain control means for adjusting a gain of the obtained intermediate frequency signal to obtain a second gain adjusted signal;

Level detecting means for detecting a signal level of the first gain-adjusted signal and generating a control voltage according to the signal level;

When the control voltage one gain characteristic in the first gain control means and the control voltage one gain characteristic in the second gain control means are equal to each other, the control voltage is supplied from the level detection means to the first and second gains. The diversity receiving apparatus according to claim i, wherein the second gain-adjusted signal is supplied to a control means to be a level-adjusted signal.

[3] The level adjusting means includes first gain control means for adjusting the gain of the received signal received for each branch to obtain a first gain adjusted signal;

When the control voltage-one gain characteristic in the first gain control means and the control voltage-gain characteristic in the second gain control means are different from each other, the control voltage from the level detection means is the control voltage in the first gain control means. One gain characteristic and the second gain control means. A control voltage level adjusting unit that converts the level according to a relationship with the control voltage-gain characteristic and gives the second voltage to the second gain control unit,

2. The diversity receiving apparatus according to claim 1, wherein the first gain adjusting means is supplied with a control voltage from the level detecting means.

[4] The level adjustment means adjusts the gain of the received signal received for each branch and sets the first gain adjusted signal as the first gain adjusted signal;

Storage means for storing the control voltage-one gain characteristic in the first gain control means and the control voltage-gain characteristic in the second gain control means as a data table; and detecting the signal level of the first gain-adjusted signal Then, based on the signal level, a control voltage is generated by referring to the data table, and the control voltage is supplied to the first and second gain adjusting means to adjust the level of the second gain adjusted signal. 2. The diversity receiving apparatus according to claim 1, further comprising a control voltage level adjusting unit configured as a completed signal.

[5] The level adjustment means adjusts the gain of the received signal received for each branch and sets the first gain adjusted signal as the first gain adjusted signal;

Voltage difference calculation means for obtaining a difference in control voltage between the branches as a voltage difference, and obtaining a noise level difference between the branches as a noise level difference according to the voltage difference, the noise level difference being equal to or greater than a predetermined threshold value When the noise level difference is equal to or greater than a predetermined threshold, the gain of the second gain control means is minimized in the branch that causes degradation of the signal-to-noise ratio after synthesis. A noise level difference detection determination means for generating a minimum gain control voltage and supplying the minimum gain control voltage to the second gain control means, The first gain adjustment means is supplied with a control voltage from the level detection means, and the second gain control means in a branch other than the branch that causes degradation of the signal-to-noise ratio after the synthesis is supplied to the first gain adjustment means. 2. The diversity receiver according to claim 1, wherein a control voltage is supplied from the level detection means.

[6] The noise level difference detection / determination means determines a branch that causes degradation of the signal-to-noise ratio after synthesis in accordance with a control voltage between the branches detected by the level detection means. The diversity receiver according to claim 5.

[7] Phase difference detection means for detecting a phase difference between level-adjusted signals;

2. The diversity receiver according to claim 1, further comprising phase adjusting means for adjusting the phase of the intermediate frequency signal in accordance with the phase difference.