JPS61154337A - Psk demodulator - Google Patents

Abstract

PURPOSE:To simplify a PSK demodulation circuit by a synchronizing detection system by using two orthogonal vectors generated by a vector representing a signal point of a base band signal before one symbol as a criterion of data identification of the PSK demodulator. CONSTITUTION:A received PSK signal is detected synchronously by an oscillator 51, multipliers 52, 53, and LPFs 54, 55 to extract two base band signals of in-phase and orthogonal components. The signal is sampled by symbol rate sampling circuits 57, 58 according to the timing extracted by a synchronizing clock extraction part 56. The output of the circuits 57, 58 is inputted respectively to delay circuits 59, 60 and a vector product operating circuit 62. The circuits 59, 60 apply one symbol delay operation and the result is outputted to a vector rotation operating circuit 61. The circuit 61 takes an output signal point of the circuits 59, 60 on a plane where the in-phase and orthogonal component of the base band signal as X, Y axes as a position vector relative to the origin, rotates the vecor around the origin by 45 deg. and 135 deg. and outputs the result to the circuit 62. The circuit 62 operates the vector product of the input signals and the result is discriminated by a discriminating circuit 63.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a PSKgA modulator, and more particularly to a PSK demodulator that outputs baseband signals of in-phase and quadrature components.

[Prior art]

Conventionally, when demodulating a PSK (8-phase phase) modulated signal, the received signal is multiplied by a sine wave with the same frequency as the carrier frequency, and the result is passed through a low-pass filter afterward to generate harmonics generated by the multiplication. A synchronous detection method that removes components and extracts a baseband signal is widely used. However, in the case of the synchronous detection method, a phase control circuit is required to correct the phase shift and frequency offset between the received signal and the demodulated sine wave, which inevitably increases the complexity of the device and reduces cost. was difficult to realize.

As shown in FIG. 5, the conventional shunichi is a device that demodulates a PSK modulated signal that has been differentially encoded into four phases, and includes a oscillator 1 that generates a sine wave and a signal that advances the phase of the sine wave by 90 degrees. and rice li and device 2 connected to this oscillator l, respectively.
, 3 and a low-pass filter 4 connected to the multiplier 2.3.
．． 5, a synchronized clock extraction section 6 which extracts symbol rate timing from the received signal and provides data identification timing, and a symbol rate sampling circuit 7 which performs sampling according to the clock generated by the synchronized clock extraction section 6.
．． 8, a signal point rotation unit 9 that rotates a vector by two orthogonal signals, a data identification unit 10 that identifies the absolute phase information 1 of the two orthogonal signal Eli data, and a rotation amount of the signal point rotation unit. It is composed of a phase control section 11 that controls the phase control section 11, and a phase decoding section 12 that changes the absolute phase information tl-travel phase ↑H information obtained by the data identification section.

To explain the operation of this conventional demodulator itt, the received PSK signal is multiplied by the two sine waves generated by the excavator 1 in a multiplier 2.3, respectively.

The results are passed through low-pass filters 4 and 5, respectively, to remove harmonic components generated by multiplication and extract baseband signals of in-phase and quadrature components, respectively. - 10,000, the synchronous clock extraction unit 6 extracts the timing of the symbol rate by squaring the received PSK signal, applying non-linear processing such as Hime style to the received PSK signal, and generates a clock for symbol rate sampling. do.

The 7-volume rate book sampling circuit 7.8 samples the in-phase and quadrature baseband signals respectively in accordance with the clock generated by the synchronous clock extraction section 6.

The output signal of the sampling circuit 7.8 is manually inputted to the signal point rotation section 9.

The signal point rotation section 9 rotates the signal point as shown in FIG. 6 in accordance with the rotation Ikxt instructed by the phase control section 11. The results are input manually to the data identification unit IO. The data identification section 10 performs this by detecting in which region the position of the signal point falls, showing the absolute phase as shown in FIG. That is, the absolute phase is determined by comparing the magnitudes of the in-phase component and the quadrature component of the baseband signal inputted to the data identification unit 10, and by determining the sign of each component. The absolute phase information obtained by the data identification section 1O is input to the decoding section 12 and converted into differential phase information.

On the other hand, the phase control unit 11 detects the phase difference between the estimated signal point indicating the phase state determined by data identification and the signal point based on the in-phase and orthogonal baseband signal actually input to the data identification unit 10. Various methods can be used for zero phase control to perform control and determine the amount of rotation in the one signal point rotation unit 9, but according to the method shown in FIG. If the data is Ai, the baseband signal is Ai in complex number representation.
Therefore, it is a good idea for the signal point rotation section 9 to rotate the signal point of the baseband signal by e-JJ1.The phase control section 11 uses the estimated value e-ji of e-j''
By creating +, the amount of rotation of the signal is determined. That is, by dividing the baseband signal Aie"' by its estimated value Ai to extract v, , J I 1 and selecting its imaginary part, θi is approximately obtained as sin #i˜θi.

By passing through the θit-loop filter, averaging is performed to create 31, and e-16+ is created.

In this way, the conventional PSK demodulator requires a phase control circuit to compensate for the phase shift in synchronous detection, and its configuration is complicated because it includes complex operations, etc. When considering low-rate PSK modulation and demodulation, it has been difficult to implement due to the extremely high cost compared to its transmission capacity.

[Purpose of the invention]

An object of the present invention is to provide a low-cost PSK demodulation device that simplifies PSK demodulation using a synchronous detection method by eliminating the drawbacks of conventional PSK demodulation devices and improving the data identification method in PSK demodulation. There is a particular thing.

[Structure of the invention]

According to the present invention, the baseband signal of the in-phase component obtained by multiplying the PSKJ-tuned 1δ signal by a sine wave and the quadrature component obtained by multiplying the signal obtained by shifting the phase fjL of the sine wave by 90 degrees. First and second delay circuits each delay the in-phase and quadrature components of the baseband signal sampled at the symbol rate by l sampling periods, respectively. The first and second
With the signal point indicated by the output signal of the delay circuit as a position vector with respect to the origin, the outputs of the first and second delay circuits are expressed as (180/2n+"(360/2n)
i (i=0...,n-1) degree rotation to obtain n vectors, and the in-phase and quadrature baseband signals and the There is provided a PSK temporary locating device having a vector product calculation circuit that calculates the vector product of vectors, and a determination circuit that determines data from the output of the vector product calculation circuit.

[Action of the invention]

The present invention sets the standard for tail classification in the data identification section of the PSK demodulator to 1g of the baseband signal one symbol before.
By detecting the positional relationship between the two vectors and the vector indicating the signal point of the baseband signal in the current sampling, the vector of the previous one and the The angle difference relative to the current sampling vector is estimated and used as the data identification result.

〔Example〕

Next, one embodiment of the present invention will be described using the drawings.

FIG. 1 shows an embodiment of the invention. In FIG. 1, this embodiment is a device for demodulating a four-phase differentially encoded PSK modulated signal, and includes an oscillator 51 that generates a sine wave and a signal whose phase is advanced by 90@, and an excavator 51. a multiplier 52.53 connected to the multiplier 52.53, a low-pass filter 54.55 connected to the multiplier 52.53, a synchronous clock extraction unit 56 that extracts symbol rate timing from the received signal and provides data identification timing, and a low-pass symbol rate sampling circuit 57.5 connected to filter 54.55 and supplied with data identification timing;
8, a delay circuit 59.60 that delays the output value g of the symbol rate sampling circuit 57.58 by one symbol, the output signal of the symbol rate sampling circuit 57.58, and the output signal of the delay circuit 59.60 as a vector. , a vector rotation calculation circuit 61 that rotates the output signals of the delay circuits 59 and 60, and a vector & calculation circuit that calculates a vector 8i of the output signals of the symbol rate sampling circuits 57 and 58 and the output signal of the vector rotation calculation circuit 61. 62, and a determination circuit 63 that determines data based on the output of the vector product calculation circuit.

Operation of this embodiment - To explain, the received PSK signal is synchronously detected by the total oscillator 51, multipliers 52, 53, and low-pass filters 54, 55, and two baseband signals of in-phase and quadrature components are extracted. These two baseband signals are sampled by symbol rate sampling circuits 57 and 58 in accordance with the timing determined by the fi'r1M clock extractor 56.

The baseband signals sent in sample jigs by the symbol rate sampling circuits 57 and 58 are sent to the delay circuit 5.
9.60 and the vector product calculation circuit 63. Delay circuits 59 and 60 perform l-symbol delay operations and output the results to vector rotation calculation circuits 61 and 62.

The vector rotation arithmetic circuit 59 sets the signal point indicated by the output signal of the delay circuit 59, 60 on the plane as the origin on the plane in which the in-phase component t'x-axis component and the orthogonal component ty-axis component of the baseband signal are formed. The result of rotating it by 45 degrees around the origin and the result of rotating it by 1356 degrees are output to the vector product calculation circuit 62.

In FIG. 2, vectors based on the outputs of delay circuits 59 and 60,
The vector of the output result of the vector rotation arithmetic circuit 61 and four regions into which the plane is divided using the two vectors are shown. The basic equation for vector rotation calculation is shown in equation (1). The vector product calculation circuit 62 calculates the vector product of the two vectors output from the vector calculation circuit and the vector produced by the output signal of the symbol rate sampling circuit 57.580. y cosθ (1
) x t Y: Vector to be rotated x', y': Vector to be rotated θ: Rotation angle Performed for components among the m*jsk components.

The angle component of the vector product is positive when the angle between the two vectors is counterclockwise and θ~180@, and negative when it is 180~360', so by calculating the l component, the angle table between the vectors is If it is within 180”, it is clockwise.
You can determine which direction is clockwise. Therefore, by using two orthogonal vectors, it is possible to determine where an arbitrary vector falls in each region shown in FIG. 2 with respect to the two vectors. The formula for determining the l component of the vector product is shown in formula (2). Let the two vectors be a = (a,, a,, a,), 6 = (b,, b,
, b, ), FIG. 3 shows a simple realization of vector rotation and vector product operations t-m. The data identification results are shown when the calculation results 5gn1°5gn2 of FIG. 3 are made by human power of the judgment circuit 630. The result is differential phase information.

In this way, in the embodiment of the present invention, the synchronous detection method is used and nine P
Since the phase side # is not required in the SK demodulator, PSK demodulation can be performed with a simple configuration and cost reduction can be achieved.Furthermore, a decoder is not required after data identification in demodulating differentially encoded PSK signals. becomes.

〔Effect of the invention〕

As explained above, the present invention provides a PS using the synchronous transverse wave method.
In order to eliminate the need for a special phase control circuit in the KOL adjustment device, its configuration is simplified and differentially encoded P
In the demodulation of the SK signal, the decoder after data identification serves as an undercoat.

[Brief explanation of drawings]

FIG. 41 is a block diagram showing a PSK demodulator which is an embodiment of the present invention, FIG. 2 is a diagram showing vector relationships and identification areas in data identification according to an embodiment of the present invention, and FIG. FIG. 4 is a diagram showing a calculation method for data identification in one embodiment. FIG. 4 is a diagram showing data identification results obtained by the calculation method of this embodiment. #! Figure 5 is a block diagram showing a conventional demodulator. Figure 6 is a diagram showing the rotation of the signal points of the baseband signal. Figure 7 is a diagram showing the data identification results and the signal points of the baseband signal in the conventional demodulator. FIG. 8 is a block diagram showing a phase control method in a conventional demodulator. 1.51...Oscillator, 2,3,52.53...
...Multiplication IK device, 4, s, 54, s s
・・・・・・Low pass filter, 6.56・・・・・・
Synchronous clock extraction section, 7, 8.57°58...
Symbol Ray) - Sampling circuit, 9... Signal rotation section, 10.61... Data identification section, 11
... Phase control section, 12 ... Phase decoding section, 59.60 ... Delay circuit, 61 ...
. . . Vector rotation calculation circuit, 62 . . . Vector product calculation circuit, 63 . . . Determination circuit. Agent Patent Attorney Susumu Uchihara...) 1 Jyo Y
Guichisuba) b signal diagram

Claims (1)

[Claims] The baseband signal of the in-phase component obtained by multiplying the PSK modulated signal by a sine wave and the phase of the sine wave are 90
In a PSK demodulation method that outputs a baseband signal of orthogonal components obtained by multiplying a phase-shifted signal, a first delay circuit that delays the in-phase baseband signal sampled at the symbol rate by one sampling period. a second delay circuit that delays the sampled orthogonal baseband signal by one sampling period; and a second delay circuit that delays the sampled orthogonal baseband signal by one sampling period; and the second
As a position vector formed by the point indicated by the output signal of the delay circuit and the origin, the position vector is defined as [180/2^
n+(360/2^n)・i(i=0,...,n-1
)] a vector rotation calculation circuit that rotates the n vectors to obtain n vectors, a vector product calculation circuit that calculates vector products of the n vectors with vectors based on the in-phase and quadrature baseband signals, and the vectors. A PSK demodulator comprising: a determination circuit that determines data based on the output of the product calculation circuit.