JPH02228849A - Quadruple phase shift keying detection circuit - Google Patents

Abstract

PURPOSE:To obtain an excellent detection characteristic independently of the presence of fading by selecting a preferred detection system corresponding to the presence or absence of fading. CONSTITUTION:A detection section 5 having a delay detection section and a synchronizing detection section, a fading detection section 6 detecting the presence or absence of fading and a selection section 7 are provided to a quadruple phase shift keying detection circuit. The fading detection section 6 counts the number of times per time T in which the envelope of an incoming level of a quadruple phase shift keying wave is below mean power of the incoming level and sends a control signal to select the delay detection section when the count exceeds a predetermined setting value and to select the synchronizing detection section when the count does not exceed the predetermined setting value to the selection section 7. Thus, an excellent detection characteristic is obtained independently of the presence or absence of fading.

Description

Detailed Description of the Invention [Summary] For example, regarding a four-phase phase shift keying detection circuit used in a digital mobile radio device, a four-phase phase shift keying detection circuit that can obtain good detection characteristics regardless of the presence or absence of fading is disclosed. A detection section having a delayed detection section and a synchronous detection section, a selection section that selects either one of the detection sections according to the state of an input control signal, and a four-phase phase shift keying method for the received four-phase phase shift keying. Counts the number of times per T time that the envelope of the incoming signal level is less than the average power of the incoming signal level, and when the count value exceeds a predetermined set value, the delayed detection part is used, and when it does not exceed the synchronous detection part. The fading detection section is configured to include a fading detection section that sends out a control signal for selecting the section.

[Industrial application field]

The present invention can be used for example in digital mobile radio equipment.
The present invention relates to a phase shift keying detection circuit.

For example, in the case of a car telephone system, the mobile station is 800M
H2 band 4-phase phase shift keying wave (below).

After the receiving section receives the 4-phase PSK wave (abbreviated as 4-phase PS wave) and converts it into a 4-phase PSK wave in an intermediate frequency band, the 4-phase PS wave is detected by a detection circuit and audio signals and data are extracted.

At this time, when there is no line of sight between the mobile station and the base station, the received wave is a composite of many reflected waves, diffracted waves, etc., and a standing wave stands in space. When a mobile station travels through this standing wave, the combined electric field strength of the received wave fluctuates, causing fading, deteriorating detection characteristics, and distorting the demodulated wave. However, when there is visibility, standing waves are not supported and fading hardly occurs.

Therefore, it is desired to provide a four-phase PSK detection circuit that can obtain good detection characteristics regardless of the presence or absence of fading.

[Conventional technology]

Generally, two types of detection circuits are known for the 4-phase PS: a delayed detection method and a synchronous detection method. Fig. 5 is a block diagram of a conventional example. Fig. 5(a) shows a 4-phase PSK detection circuit using a delayed detection method, and Fig. 5 0)) shows a 4-phase PSK detection circuit using a synchronous detection method. . The operation of the two 4-phase PS detection circuits will be explained below.

(1) When using delayed detection method (see Figure 5 (a))
First, on the transmitting side (not shown), the pig string Xi・
(a+b+) is subjected to summation conversion (summation with data one bit before is used as a transmission bit).

The data string after conversion is expressed as '14=Yi-, 10Xi. Using this Y as a modulation signal, Ymu・(cidr)O・(00), 1=(01), 2・(11), 3
・Corresponding to (10), change the phase of the carrier wave to π/4.3π/4
, 5π/4, and 7π/4.

Here, X is the latest data, vt is ΣX74+1 , and the numbers in parentheses indicate Gray code binary numbers.

On the receiving side, 800M received by one antenna ■ 4 of 2 bands
The phase PSK wave is mixed with the output of a voltage controlled oscillator (hereinafter abbreviated as VCO) 19 by a mixer 11, and the frequency is converted into a four-phase PSK wave in an intermediate frequency band. Frequency converted 4
The wave in phase PS is delayed by the time T of one symbol of data by the delay element 12, and the phase is further advanced by π/4 by the phase shifter 13 to obtain a reference carrier wave, and this reference carrier wave and the intermediate frequency band The detector 14 performs multiplicative detection between the four-phase PSK wave and the four-phase PSK wave.

Therefore, a detected output (hereinafter referred to as a baseband signal) is obtained from the detector 14, and this baseband signal is applied to the discriminator 32 after high frequency components are removed by a low-pass filter 15. Here, the data timing regeneration circuit 31 reproduces from the 4-phase PSK wave in the intermediate frequency band and locks it, so the baseband signal is identified in synchronization with this clock and the Ich data a
1 is played.

Also, the output of the delay element 12 is (π/4) phase shifter 1
After passing through the detector 17, a baseband signal is obtained by product detection between the four-phase PSK wave in the intermediate frequency band, and the baseband signal is passed through the low-pass filter 18.6. Using the discriminator 33, the Qch data b is reproduced by the same operation as above.

Here, if the oscillation frequency of the VCO 19 shifts, incorrect reproduction data will increase, so a control voltage is used to prevent the oscillation frequency from shifting, but this control voltage is controlled by the carrier wave regeneration circuit enclosed by the dotted line as shown below. It has gained. That is, the output of the low-pass filter 15.18 is subtracted by the subtracter 21 and added by the adder 22, and the result is added to the multiplier 23.
Multiply by Furthermore, a low-pass filter 1 is provided by a multiplier 25.
5. After multiplying the output of 18, this multiplication result and multiplier 2
When the multiplication result of 3 is further multiplied by the multiplier 24 and the multiplication result is passed through the loop filter 26, a phase difference output proportional to the shift in the oscillation frequency of the VCO is obtained.

This becomes the control voltage of vCO.

(2) When using synchronous detection method (see Figure 5(b))
The 4-phase PSK wave received by the antenna is sent to the receiving local oscillator 4.
The output of 7 is mixed with the mixer 41 to produce 4-phase P in the intermediate frequency band.
It is converted into an SK wave and applied to the detector 43.

On the other hand, νC048 whose oscillation frequency is controlled by the control voltage sent out from the above carrier wave regeneration circuit (dotted line part)
The phase of the reproduced reference carrier wave is advanced by π/2 by a (-π/2) phase shifter 42 and is also applied to a detector 43. Therefore, multiplicative detection is performed between the two waves and I
A channel baseband signal is obtained.

This I channel baseband signal passes through a low-pass filter 44 to remove high frequency components, and is applied to the identification circuit 32. Since this identification circuit is supplied with a clock that is recovered from the four-phase PSK wave in the intermediate frequency band by the data timing recovery circuit 31, the I c is synchronized with this clock.
The data town of h is played.

Also, a detector 45 to which the four-phase PSK wave in the intermediate frequency band and the reproduction reference carrier wave from the VCo 4B are directly added. Low-pass filter 46. Using the discriminator 33, the Q channel data b4 is reproduced by the same operation as above.

[Problem to be solved by the invention]

In mobile communications, as mentioned above, fading may or may not occur depending on the presence or absence of line-of-sight between the mobile station and the base station, but let us compare the delayed detection method and the synchronous detection method depending on the presence or absence of fading. .

(1) In the case of no fading In the synchronous detection method, even if the received 4-phase PSK wave contains noise, it does not contain noise because the reference carrier uses the reproduced reference carrier wave reproduced by the VCO.

On the other hand, in the delayed detection method, if the received 4-phase PSK wave contains noise, the 4-phase PSK wave one time slot before, which is the reference carrier wave, also contains noise, so the two 4-phase PSK waves input to the detector Both PSX waves will contain noise,
The former has a better error rate than the latter.

(2) In the case of fading In the case of synchronous detection, fading causes a wave phase shift in the 4-phase PS, but because the time constant of the loop filter 26 in the carrier wave regeneration circuit is large, the wave phase shift is regenerated in the 4-phase PS. The phase change of the reference carrier wave cannot be followed.

Therefore, by reducing the time constant of the loop filter, it becomes possible to follow the above-mentioned phase shift due to fading, but when there is no fading, the error rate deteriorates due to the influence of phase changes due to internal noise.

On the other hand, in the differential detection method, even if a phase shift occurs in the four-phase PSK wave, the four-phase PSK wave one time slot before also causes almost the same phase shift. This is a fading pitch (e.g., 3
0 Hz) is sufficiently slow, 4-phase P in one time slot
This is because the phase change of the SK wave is sufficiently small. For this reason, the latter has a better error rate than the former.

That is, since the preferred detection method differs depending on the presence or absence of fading, there is a problem in that a 4PSK detection circuit that can obtain good detection characteristics regardless of the presence or absence of fading cannot be provided.

- An object of the present invention is to provide a four-phase phase shift keying detection circuit that can obtain good detection characteristics regardless of the presence or absence of fading.

[Means to solve problems]

FIG. 1 shows a block diagram of the principle of the present invention.

5 branches a part of the received 4-phase phase shift keying wave, delays it by one time slot, and uses it as a reference carrier wave, and performs multiplicative detection between the reference carrier wave and the subsequent 4-phase phase shift keying wave. A delay detection part extracts the baseband signal by performing the following steps, and a reference carrier is regenerated using the received four-phase phase shift keying wave. This is a detection section that has a synchronous detection section that extracts band signals.

In addition, 7 counts the number of times per T time that the envelope of the incoming level of the received four-phase phase shift keying wave is less than the average power of the incoming level, and when the count value exceeds a predetermined set value, there is a delay. This is a fading detection section that sends out a control signal that selects the synchronous detection section when the detection section is not exceeded.

[Effect]

The present invention provides a detection section 5 having a delayed detection section and a synchronous detection section.
．． A fading detection part 62 and a selection part 7 are provided to detect the presence or absence of fading, and when the fading detection part detects the presence of fading, the selection part selects the delayed detection part, and when it detects the absence of fading, the selection part selects the synchronous detection part. I configured it.

This allows for fading or no fading.

A four-phase PSK wave detection circuit that can obtain good detection characteristics can be provided.

[Embodiment] Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is an example of a block diagram of a fading detection part in Fig. 2, and Fig. 4 is an example of a block diagram of a quaternary difference conversion part in Fig. 2. An example of a block diagram is shown.

Kokote, mixer 51. VCQ 57.58. Delay element 52° phase shifter 53, 53', 56. Detector 54.5
4', the low-pass filter 55 is a component of the detection section 5;
S-1 to Sk indicate the constituent parts of the selection part 7, hereinafter,
The operations shown in FIGS. 2 to 4 will be explained.

First, the four-phase PSK wave in the intermediate frequency band output from the mixer 51 in FIG. 2 is added to the diode 61 in FIG.
The amplitude modulation component (envelope component) of the SX wave is extracted and applied to low-pass filters 62 and 63. The cut-off frequency of the low-pass filter 62 is 1, for example, 100 Hz, and the cut-off frequency of the low-pass filter 63 is.

For example, 1) the cut-off frequency is lower than that of Iz and the above-mentioned filters.

Therefore, the envelope line component (
corresponding to the envelope of the incoming signal level), level-shifted by a level shift circuit 64 and applied to a comparator 65.

Further, the average level of the envelope component (corresponding to the average power of the incoming call level) is extracted from the latter and similarly applied to the comparator 65 as a threshold value.

Note that the level shift is performed when there is no fading, and noise near the threshold value (for example,
(due to internal noise of the receiver) is input to the comparator 65,
In order to prevent an erroneous output from being sent out from this comparator, the threshold value is shifted to the + side. In addition, when there is no fading, the four-phase PsK wave does not include an amplitude modulation component, but 1
When fading occurs, amplitude modulated wave components are included.

Now, the comparator 65 outputs a pulse and adds it to a 4-bit counter 66, for example, every time the output of the level shift circuit 64 becomes less than the threshold value.

Therefore, the counter 66 counts the input pulses.
The count value is added to the digital magnitude comparator 67. Since the digital magnitude comparator 67 has a set value input in advance through switches S6 to SW, the count value and the set value are compared in magnitude every clock, and the count value is higher than the set value. Comparison output of H when is also large.

When it is small, the comparison output of L is connected to D type flip-flop 6.
Output via B. Note that the counter is reset every clock (corresponding to every time T in the claims).

Next, the operation of FIG. 2 will be explained with reference to FIG. 3. The switch SW+ "" SWt in FIG.
The phase PSK detection circuit operates according to the delayed detection method, whereas the one-dot line indicates the operation according to the synchronous detection method.

(1) In case of delayed detection method, the 4-phase PSK wave received by the antenna is vC057
is mixed with the output of
The frequency is converted into a wave. Frequency converted 4-phase PSK
The wave is delayed by one data symbol time T by the delay element 52, passes through the switch SW, advances the phase by (-π/4) by the phase shifter 53° by π/4, and then transfers to the four phases of the intermediate frequency band. P
A detector 54 performs product detection between the SK wave and the SK wave.

Then, the baseband signal from the wave detector 54 is filtered by a low-pass filter 55 to remove high frequency components, and then passed to the discriminator 3.
Since the clock regenerated by the data timing regeneration circuit 31 is added here, the I channel data a is regenerated using this clock.

Furthermore, the frequency-converted four-phase PSK wave and the delay element 52. switch SWI, (π/4) phase shifter 56. Using the detector 54', the low-pass filter 55', and the discriminator 33, Qch data bi is reproduced by the same operation as above.

Further, as in the conventional example, the output of the carrier wave regeneration circuit surrounded by a dotted line is applied as a control voltage to the VCO 57 via switches SWz and SWt, thereby controlling one oscillation frequency.

(2) In the case of the synchronous detection method, the 4-phase PS wave received by the antenna is mixed with the output of the VCO 57 by the mixer 51, converted into a 4-phase PSK wave in the intermediate frequency band, and is applied to the detector 54.

On the other hand, the regenerated reference carrier wave from the VCo 58, whose oscillation frequency is controlled by the control voltage applied from the carrier regeneration circuit (dotted line part) via the switch S-2, is transmitted through two (-π/4) shifts. Since the phase is advanced by (π/2) by the phase shifters 53 and 53' and applied to the detector 54, these two waves are subjected to product detection to obtain the baseband signal for I channel, which is a low-pass signal. The high frequency components are removed through a filter 55 and applied to the identification circuit 32.

Since the clock reproduced by the data timing reproducing circuit 31 is applied to the identification circuit 32, the [de data Ci for channel] is taken out.

The four-phase PSK wave in the intermediate frequency band is also applied to the detector 54', where the reproduced reference carrier wave from the VCo 58 (-π/4) is applied to the phase shifter 53'. Switch SW, (π/
4) Since the signals are added via the phase shifter 56 with a phase shift difference of O, the Q Ch baseband signal is extracted by first power product detection. From this signal, data for Och is extracted using the low-pass filter 55' discriminator 33 in the same manner as described above.

Then, the I channel data C and the Q channel data i are added to the quaternary difference conversion section 34, but since the summation conversion is performed on the transmitting side as described above, in the synchronous detection method, the difference conversion is performed. It is necessary to do this to return to the state before conversion.

FIG. 4 is an example of a block diagram of the quaternary difference conversion section.

On the transmitting side, as mentioned above, the data is sent in Gray code binary numbers, so it is converted into natural binary numbers in the EX-OR circuit 341, delayed by one symbol time T in the delay element 342, and then sent to the inverters 343 and 344. to invert.

Then, the data Ci Sdi that has become a natural binary number, the outputs of the inverters 343 and 344, and 1 are added to the full adder 345.
, and the addition result is added to the EX-OR circuit 346 to return it to natural binary data before conversion. after that.

Furthermore, it is converted into Gray code binary numbers and the original data a8. b
, take out.

This allows for fading or no fading.

It becomes possible to provide a four-phase PSK detection circuit that provides good detection characteristics.

There is fruit.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram of an embodiment of the present invention, Figure 3 is an example of a block diagram of the fading detection part in Figure 2, and Figure 4 is in Figure 2. An example of a block diagram of the quaternary difference conversion part of FIG. 5 is a block diagram of a conventional example. In the figure, 5 indicates a detection section, 6 indicates a fading detection section, and 7 indicates a selection section. [Effects of the Invention] As explained in detail above, according to the present invention, a four-phase p
It is said that the detection circuit can be provided to S! Reason
口・NG■ 19Ij of the block of the 7th plant in Figure 2
4 in Fig. 2]] Main part of ``1 Outer Change'' Kozoku diagram → 1,57th Traditional example of Frodzuku diagram No. 5V sword

Claims (1)

[Claims] Branching a part of the received four-phase phase shift keying wave, giving it a delay of one time slot and using it as a reference carrier wave,
a delayed detection part that performs multiplicative detection between the reference carrier wave and a subsequent four-phase phase shift keying wave to extract a baseband signal; and regenerating the reference carrier wave using the received four-phase phase shift keying wave; a detection section (5) having a synchronous detection section that performs multiplicative detection of a reproduction reference carrier wave and a four-phase phase shift keying wave to extract a baseband signal; A selection part (7) for selecting a detection part, and counting the number of times per T time that the envelope of the incoming level of the received four-phase phase shift keying wave is equal to or less than the average power of the incoming level, and the count value is set in advance. 4-phase phase shift keying characterized by having a fading detection section (6) that sends out a control signal that selects a delayed detection section when a predetermined set value is exceeded, and a synchronous detection section when it does not exceed a predetermined set value. Detection circuit.