JP3349112B2 - Offset adjustment method and offset adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an offset adjusting method and an offset adjusting apparatus for adjusting I and Q offsets in a transmitting apparatus using a quadrature modulator.

[0002]

2. Description of the Related Art In a transmitting apparatus using a quadrature modulator,
In general, a baseband signal generator for generating I and Q signals and a radio unit including a quadrature modulator are configured as separate units. Then, in the baseband signal generation unit and the radio unit,
In each case, I and Q offsets occur due to the imbalance of the DC voltage.

[0003] The I and Q offsets degrade the origin offset of a modulated output signal at the time of transmission and increase carrier leakage. Further, the modulation accuracy is deteriorated. The origin offset (origin offset) is a decibel representation of the absolute value of the signal level with respect to the absolute value of the offset from the origin. Deterioration of the origin offset affects the in-band transmission spurious characteristics. Further, when the reception level at the partner receiving side is high, for example, when the transmitting side and the receiving side are close, the error rate is increased.

In order to avoid the above-mentioned problem caused by the deterioration of the origin offset, the value of the origin offset may be reduced. In order to reduce the origin offset, it is conceivable to reduce the offset in each individual device or each unit constituting the transmission apparatus, or to reduce the offset by offset adjustment. However, if an attempt is made to reduce the offset in each individual device or the like, the adjustment man-hour is not required, but the yield at the time of manufacturing each device or the like may be reduced, which is not preferable.

FIG. 8 is a block diagram showing a configuration for reducing the offset by adjusting the offset in the transmitting apparatus. In the example shown in FIG.
It has a digital signal input terminal 1 and an analog signal input terminal 2. The analog signal input to the analog signal input terminal 2 is converted into an ADPCM code by the ADPCM encoder 3.

Digital signal input terminal 1 or ADPC
The digital signal from the M encoder 3 is input to the baseband signal generator 4. In the baseband signal generation unit 4, the time division multiplexing circuit 4a includes, for example, TDMA / TDD (Time Division) defined by RCR (Radio System Development Center) STD-28.
Multiple Access / Time Divi
(Son Duplex) multiplexing. Then, the differential encoder 4b differentially encodes the multiplexed signal to generate I and Q signals. An offset adjustment circuit 4c is connected to the differential encoder 4b.

[0007] The I and Q signals from the differential encoder 4b are input to the radio unit 5. In the radio unit 5, a quadrature modulator 5a
Is, for example, π / 4 shift QPS based on the I and Q signals.
Performs K modulation to generate a modulated output signal. The modulated output signal is frequency-converted to, for example, a 1.9 GHz band by a frequency conversion circuit 5b, power-amplified to a required level by a power amplifier 5c, and then supplied to an antenna (not shown).

[0008] The baseband signal generating unit 4 is provided with a bus 9 to a microcomputer system that executes a radio protocol.
Connected via The microcomputer system includes, for example, a RAM 6, a ROM 71, and a CPU 8. Then, a dip switch 12 having a large number of bits for offset adjustment is connected via an I / O port 11.

At the time of offset adjustment, the CPU 8 independently adjusts the offset of the I signal and the Q signal in accordance with the setting of the dip switch 12. That is, the CPU 8
Changes the setting state of the DIP switch 12 to the I / O port 1
1 and the read value is set in the offset adjustment circuit 4c. The differential encoder 4b gives an offset to each of the I signal and the Q signal according to the set value of the offset adjustment circuit 4c.

When an offset adjustment is performed at the time of shipping inspection of the transmitting apparatus 101, an origin offset measuring means 10 such as a spectrum analyzer or a radio tester is connected to an output terminal of the power amplifier 5c. The person who makes the adjustment measures the origin offset of the transmission output signal with the origin offset measuring means 10. Then, the DIP switch 12 is set so that the measured value is equal to or less than the standard, for example, equal to or less than -35 dB.

[0011]

Since the conventional offset adjustment method is performed as described above, the adjuster changes the I offset and the Q offset by the dip switch 12 while changing the origin offset of the transmission output signal. Is set to a value equal to or less than the standard.

However, the origin offset measuring means 1
The value obtained from the offset value obtained by 0 is only the absolute value of the I and Q offsets. Since the I signal and the Q signal are two-dimensional signals, the respective offset values of the I signal and the Q signal cannot be immediately obtained from the offset values obtained by the origin offset measuring means 10.

Therefore, until the set value of the dip switch 12 that makes the origin offset equal to or less than the standard value is obtained,
A large number of measurements must be made while appropriately changing the setting of the I and Q offsets by the dip switch 12. That is, there is a problem that it takes time and effort until the offset adjustment is completed.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an offset adjusting method and an offset adjusting apparatus which can easily perform an offset adjustment in a short time.

[0015]

An offset adjusting method according to the present invention varies an offset voltage applied to a quadrature modulator a plurality of times, measures an origin offset of a modulation output signal for each offset voltage, and adjusts an offset from a measured value. It is configured to calculate a value.

According to the present invention, the setting of the I and Q offsets is varied a plurality of times, the origin offset value in the modulated output signal is measured by the origin offset measuring means, and the I and Q offsets are geometrically calculated from the plurality of measured values. , Q signal level can be determined. And I,
Since the offset value from each offset measurement point is obtained from the absolute value and the measurement value of the Q signal level, I, I can be calculated by calculating the intersection from each measurement value.
A Q offset adjustment value can be determined.

In the offset adjustment method, the offset voltage applied to the quadrature modulator is arbitrarily varied a plurality of times, the origin offset of the modulated output signal for each offset voltage is measured, and the I and Q offset values obtained from the measured origin offset value The I and Q offset adjustment values may be calculated from the (absolute value) and used as the offset adjustment values.

Further, the absolute values of the I and Q offset values obtained from the measured origin offset values when the offset adjustment value is 0 are respectively used as the I signal offset adjustment value and the Q signal offset adjustment when the Q signal offset adjustment value is set to 0. Value 0
The origin offset of the modulated output signal with respect to each offset voltage is measured by giving the -I signal offset adjustment value and the Q signal offset adjustment value with the I signal offset adjustment value set to 0, and obtains the I offset obtained from the origin offset measurement value. , Q offset value (absolute value), the I and Q offset adjustment values may be calculated and used as offset adjustment values.

The offset adjustment method is configured such that if the measured origin offset value is equal to or less than the standard at the time of each origin offset measurement, the subsequent measurement is stopped and the value set at that time is used as the offset adjustment value. You may.

Further, when the origin offset measured value of the modulated output signal adjusted by the calculated I and Q offset adjustment values exceeds the standard value, it may be configured so as to make a poor adjustment. The offset adjustment value setting process may be performed again based on the adjusted origin offset measurement value.

The offset adjustment method is configured to calculate I and Q signal levels from a plurality of origin offset measurement values, and calculate an offset adjustment value using the origin offset measurement value and the I and Q signal levels. Is also good. At this time, an upper limit and a lower limit of the I and Q signal levels may be provided to limit the calculated values of the I and Q signal levels.

Further, the origin offset good / bad judgment level at the time of adjustment may be made smaller than the adjusted origin offset good / bad judgment level. In this case, each origin offset measurement including the adjusted measurement is performed. The set value when the origin offset value is the smallest among the values may be configured as the I and Q signal offset adjustment values.

An offset adjusting apparatus according to the present invention comprises an origin offset measuring means for measuring an origin offset of a modulation output signal by a quadrature modulator, an offset voltage applied to the quadrature modulator being varied a plurality of times, and a modulation output for each offset voltage. Offset adjustment value determination means for measuring the origin offset of the signal by the origin offset measurement means and using the adjustment value calculated from the measured value as the offset adjustment value, and storage for storing the offset adjustment value determined by the offset adjustment value determination means Means for transmitting the offset adjustment value stored in the storage means to the differential encoder or the quadrature modulator in the transmission device at the time of transmission.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration for reducing an offset by offset adjustment in a transmitting apparatus. In the transmitting apparatus 100 shown in FIG. 1, the configuration other than the connection with the microcomputer system and the origin offset measuring means may be the same as the configuration shown in FIG. In this embodiment, the microcomputer system includes a RAM 6, a PROM 7 such as a flash memory, and a CPU 8. The connection with the origin offset measuring means is performed by an interface such as RS232C.

FIG. 2 is a block diagram showing a configuration example of the offset adjusting circuit 4c. In this configuration example, the offset adjustment circuit 4c is connected to the internal bus 4d of the baseband signal generator 4 and has registers 41 and 42 in which offset adjustment data is set, and a DA conversion for converting the data in the registers into analog data. Circuits 43 and 44. The registers 41 and 42 adjust the offset of the I and Q signals caused by the offset in the differential encoder 4b and the quadrature modulator 5a from the CPU 8 via the bus 9 and the internal bus 4d of the baseband signal generator 4. Is set. The outputs of the DA converters 43 and 44 are I,
It is input to the differential encoder 4b as a Q offset signal adjustment voltage.

Next, the offset adjustment method will be described with reference to the vector diagrams showing the I and Q offsets in FIG. 3 and the flowcharts in FIGS. When offset adjustment is performed at the time of shipping inspection of the transmission device 100 (step S11), an origin offset measuring unit 10 such as a spectrum analyzer or a wireless tester is connected to an output terminal of the power amplifier 5c. Further, the output of the origin offset measuring means 10 is input to the CPU 8.

Then, the CPU 8 sets 0 to each of the registers 41 and 42 of the offset adjustment circuit 4c (step S12). That is, a state where the offset adjustment is not performed (Ir = 0, Qr = 0). In this state, the origin offset measuring means 10 measures the origin offset Ooff1 (step S13). CP
U8 obtains the absolute value A of the I and Q offsets from the measured value by the equation (1) (step S14).

(Absolute value A of I, Q offset) = k × 10 ＾ (Ooff 1/20) (1)

In equation (1), the right side of “＾” indicates an exponent. K indicates a coefficient relating to the I and Q signal levels. Specifically, √ (I ＾ 2 + Q ＾ 2). However, since this value is not obtained at this stage, it is a temporary fixed value. The offset measurement points Ia, Ib, and Qa on the circumference of the dashed line with the distance A as the radius are determined from the (I, Q offset absolute values) obtained by the equation (1). The dotted circle indicates that the I and Q offset adjustment values to be obtained are on the circumference of the dotted line, as described later. The difference between the dashed-dotted circle and the dashed-dotted circle is that the fixed value differs from the actual value due to the variation of the IQ signal level, and the calculated value differs from the set value because the value set in the register is step-like. And so on.

Next, the CPU 8 gives the offset of the point Ia where the circle of the dashed line and the I axis intersect (step S).
15). That is, the CPU 8 determines that Ir = Ia, Qr
= 0 is set in the registers 41 and 42 of the offset adjustment circuit 4c.
Set to. And the origin offset measuring means 10
To measure the origin offset Ooff2 (step S16).

Similarly, the CPU 8 gives an offset of a point Ib at which the dashed-dotted line circle intersects the I axis and a point Qa at which the dashed-dotted line circle intersects the Q axis (step S1).
7, 19). That is, the CPU 8 sets Ir =
Ib, Qr = 0 and Ir = 0, Qr = Qa are set in the registers 41, 42 of the offset adjustment circuit 4c.
Then, the origin offset measuring unit 10 measures the origin offsets Ooff3 and Ooff4 (steps S18 and S20).

The CPU 8 calculates I and Q offset adjustment values from the origin offset value measured by the origin offset measuring means 10 (step S21). FIG.
It is a flowchart which shows the specific process of step S21. Each origin offset measurement value is (2) ~
The offset values B to E can be represented by Expression (5), and the offset value F between (Io-Qa) can be represented by Expression (6).

(O-Xoff) offset value B = S × 10 ＾ (Ooff 1/20) (2) (Ia-Xoff) offset value C = S × 10 ＾ (Ooff2 / 20) (3) Offset value between (Ib-Xoff) D = S × 10 ＾ (Ooff3 / 20) (4) Offset value between (Qa-Xoff) E = S × 10 ＾ (Ooff4 / 20) (5) Offset value between (Io−Qa) F = SQR (A ＾ 2 + B ＾ 2) (6)

Here, S indicates the absolute value of the I and Q signal levels. Equations (7) to (9) hold from each origin offset measurement point, and equations (10) to (12) are obtained from equations (2) to (5) and equations (7) to (9).

Ioff ＾ 2 + Qoff ＾ 2 = B ＾ 2 (7) (A-Ioff) ＾ 2 + Qoff ＾ 2 = C ＾ 2 (8) (A + Ioff) ＾ 2 + Qoff ＾ 2 = D ＾ 2・ (9)

S = SQR [(2 × A ＾ 2) / [｛10 ＾ (Ooff2 / 20)｝ ＾ 2+ ｛10 ＾ (Ooff3 / 20)｝ ＾ 2-2 × ｛10 ＾ (Ooff1 / 20) {2]] (10) Ioff = SQR {(D ＾ 2-C ＾ 2) / (4 × A)} (11) Qoff = SQR (B ＾ 2-Ioff ＾ 2)・ ・ (12) Qoff = −SQR (B ＾ 2−Ioff ＾ 2) (13)

In each equation, Ioff and Qoff indicate the I offset adjustment value and the Q offset adjustment value to be obtained. C
PU8 calculates the I and Q offset adjustment values by
First, I and Q signal levels S are calculated by substituting the respective measured values by the origin offset measuring means 10 into the equation (10) (step S211). When the I and Q signal levels S are obtained, they are substituted into the equations (2) to (6) (O-Xoff),
(Ia-Xoff), (Ib-Xoff), (Qa-X
The offset value (absolute value) between (off) and (Io-Qa) is obtained (S212).

The I and Q offset values obtained by the equation (2) correspond to the distance (0-Xoff) in FIG.
That is, the obtained I and Q offset values are (0−Xof
f) is on the circumference of the dotted line having a radius of f.

The I and Q offsets are (Ia-Xo)
From the value of ff), Xoff on the circumference of the dotted line in FIG.
Points or Xoff 'points. That is, it is limited to any one of two intersections of the circumference of the dotted line and the circle of radius | Ia−Xoff | centered on Ia. Then, the value of | Io-Qa | obtained from equation (6) and | Qa-
It is determined whether the I and Q offsets are at the Xoff point or the Xoff 'point according to the magnitude relationship with the value of Xoff | (step S213).

When the value of | Qa-Xoff | is | Io-Qa |
If it is not larger than the value, it indicates that the I and Q offsets are above the I axis. On the other hand, | Qa-Xoff |
Is larger than the value of | Io−Qa |, I and Q
That the offset is below the I axis, ie, I, Q
The offset indicates that it is at the Xoff 'point. When the I and Q offsets are above the I axis, that is, when the I and Q offsets are at the Xoff point, the I and Q offset adjustment values Iof are calculated by the equations (11) and (12).
f and Qoff are obtained (step S214). Also,
If the I and Q offsets are at Xoff 'points,
Set the I and Q offset set values Ioff and Qoff to (11)
Expression (13) is obtained by subtracting the sign of expression (12) from expression (12) (step S215).

The CPU 8 sets the I and Q offset setting values Ioff and Qoff obtained as described above in the registers 41 and 42 of the offset adjusting circuit 4c (step S22). And the origin offset measuring means 1
A measured value of the origin offset by 0 is input (step S23), and it is confirmed whether or not the measured value is equal to or smaller than a standard value (step S24). If less than the standard value, the CPU 8
Stores Ir = Ioff and Qr = Qoff in the PROM 7 (step S25), and ends the adjustment operation.

In step S24, if the measured value exceeds the standard value, it is determined that the offset adjustment is defective, and the process ends abnormally.

As described above, in this embodiment, I,
By changing the offset value of the Q signal several times (four times in this example), the origin offset of the transmission output signal is measured, I and Q offset values are calculated from the measured values, and the calculated values are used as offset adjustment values. Therefore, as in the conventional adjustment method, I,
It is not necessary to perform an operation of finding a set value such that the origin offset becomes equal to or less than the standard value while adjusting each of the Q offsets. That is, the offset adjustment can be easily completed in a short time.

When the offset adjustment is completed, the output of the power amplifier 5c is set to be supplied to the antenna.
Then, when the transmission operation is performed, the CPU 8 sets the PR
Offset adjustment values Ioff, Q set in OM7
off is read and set in the registers 41 and 42 of the offset adjustment circuit 4c (step S26). And C
The PU 8 performs transmission control (steps S27, S28,
S29).

In the above-described embodiment, only when the calculated I and Q offset setting values Ioff and Qoff are set, whether the measured value of the origin offset inputted from the origin offset measuring means 10 is equal to or less than the standard value is determined. However, as shown in FIG. 6, after each measurement (steps S13, S16, S18, S20), whether the origin offset is equal to or less than the standard value may be checked (steps S30 to S33). .

In this case, in order to improve the adjustment accuracy and secure a margin with respect to the standard, the origin offset good / bad judgment level at the time of adjustment may be made smaller than the adjusted origin offset good / bad judgment level. Furthermore, a set value when the origin offset value is the smallest among the origin offset measured values including the adjusted measurement may be set as the I and Q offset adjusted values.

In the above embodiment, after the calculated I and Q offset adjustment values are set, the origin offset of the transmission output signal is measured, and if the measured value exceeds the specified value, abnormal termination is determined. Instead of immediately terminating abnormally, the I and Q offset adjustment values may be calculated again from the origin offset measurement value, and the deviation from the offset adjustment value may be readjusted. Then, the readjustment may be repeated several times, and if the measured value does not fall below the standard value even after the readjustment is repeated several times, the process may be terminated abnormally.

In the above embodiment, the second, third, and fourth I and Q offset setting values are determined based on the first measurement value, and the origin offset is measured. The third and fourth I and Q offset adjustment values may be set to arbitrary values.

FIG. 7 shows that the second, third, and fourth I and Q offset adjustment values are set to arbitrary values I and Q, respectively.
A vector diagram when a ', Ib' and Qa 'are shown. Ia ′, Ib ′ and Qa ′ are, for example, | Ia ′
| = | Ib ′ | = | Qa ′ |, and the I and Q offset setting values are arbitrary values (in FIG. 7, | Ia ′ compared to | Xoff |
Is smaller), the equations (7) to (9) hold when calculating the I and Q offset adjustment values, and the I and Q offset adjustment values can be obtained in the same manner.

In the above embodiment, the measured I and Q signal levels are obtained, and the I and Q offset adjustment values are obtained using the values. At this time, the I and Q signal levels are affected by the residual offset. An error may occur in the level, and as a result, the origin offset adjustment value may not be optimal.
In order to prevent such a situation, upper and lower limits of the I and Q signal levels are provided, and the I and Q signal levels are limited to within the upper and lower limits to obtain the I and Q offset adjustment values. It may be.

Further, in the above embodiment, the CPU 8 in the transmitting apparatus 100 inputs the measured origin offset value and calculates the I and Q offset adjustment values, but the origin offset measuring means 10 or another external control device or the like is used. And I,
The Q offset adjustment value may be calculated, and the calculated value may be input to the CPU 8.

[0052]

As described above, according to the present invention, the offset adjusting method and the offset adjusting apparatus vary the I and Q offsets a plurality of times, and measure the origin offset of the modulation output signal by the quadrature modulator. Since the adjustment value calculated from the value is configured to be the offset adjustment value, it is not necessary to adjust the I and Q offsets and find an operation value such that the origin offset becomes equal to or less than the standard value. This has the effect that offset adjustment can be easily performed in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration for reducing an origin offset by offset adjustment in a transmission device.

FIG. 2 is a block diagram illustrating a configuration example of an offset adjustment circuit.

FIG. 3 is a vector diagram showing I and Q offsets.

FIG. 4 is a flowchart illustrating an offset adjustment process.

FIG. 5 is a flowchart showing an I and Q offset adjustment value calculation process.

FIG. 6 is a flowchart illustrating another offset adjustment process.

FIG. 7 is a vector diagram showing other I and Q offsets.

FIG. 8 is a block diagram showing a conventional configuration for reducing an origin offset by offset adjustment in a transmission device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 digital signal input terminal 2 analog signal input terminal 3 ADPCM encoder 4 baseband signal generator 5 radio 6 RAM 7 PROM 8 CPU 9 bus 10 origin offset measuring means 4 a time-division multiplexing circuit 4 b differential encoder 4 c offset adjustment circuit 5a Quadrature modulator 5b Frequency conversion circuit 5c Power amplifier 100 Transmitter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-303265 (JP, A) JP-A-10-65570 (JP, A) JP-A-7-147595 (JP, A) JP-A-6-303595 224953 (JP, A) JP-A-9-162939 (JP, A) JP-A-9-130337 (JP, A) JP-A-6-69820 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/00-27/38

Claims (11)

(57) [Claims] 1. An offset adjusting method for a transmitting apparatus including a quadrature modulator and adjusting an offset of an I signal and a Q signal according to an offset adjustment value, wherein an offset voltage applied to the quadrature modulator is varied a plurality of times. And measuring an origin offset of the modulation output signal with respect to the offset voltage of (c), and calculating an offset adjustment value from the measured value. 2. An offset voltage applied to a quadrature modulator is arbitrarily varied a plurality of times, and an origin offset of a modulation output signal with respect to each offset voltage is measured.
The offset adjustment method described. 3. An I-signal offset adjustment value and a Q-signal offset adjustment, wherein the absolute values of the I and Q offset values obtained from the origin offset measurement values when the offset adjustment value is 0 are each set to a Q signal offset adjustment value of 0. 2. An offset according to claim 1, wherein the origin offset of the modulated output signal with respect to each offset voltage is measured by giving a -I signal offset adjustment value with a value of 0 and a Q signal offset adjustment value with an I signal offset adjustment value of 0. Adjustment method. 4. The offset according to claim 2, wherein, when the origin offset measured value is less than the standard at the time of each origin offset measurement, the subsequent measurement is stopped, and the value set at that time is used as the offset adjustment value. Adjustment method. 5. The method according to claim 2, wherein the origin offset of the modulated output signal after the adjustment based on the calculated I and Q offset adjustment values is measured, and if the measured value exceeds a specified value, the adjustment is determined to be defective. Offset adjustment method. 6. An origin offset of the modulated output signal adjusted by the calculated I and Q offset adjustment values is measured, and if the measured value exceeds a standard value, the offset is again adjusted based on the adjusted origin offset measured value. 5. The offset adjustment method according to claim 2, wherein the adjustment value is set. 7. An I, Q signal level is obtained from a plurality of origin offset measurement values, and an offset adjustment value is calculated using the origin offset measurement value and the I, Q signal levels. Offset adjustment method. 8. When calculating the I and Q signal levels from a plurality of origin offset measurement values, an upper limit and a lower limit of the I and Q signal levels are provided, and the calculated I and Q signal level values are limited. Item 8. The offset adjusting method according to Item 7. 9. The offset adjustment method according to claim 2, wherein the origin offset quality determination level at the time of adjustment is smaller than the adjusted origin offset quality level. 10. The offset adjustment method according to claim 9, wherein a set value when the origin offset value is the smallest among the origin offset measurement values including the adjusted measurement is set as the I and Q signal offset adjustment values. 11. An offset adjusting device for use in a transmitting device that includes a quadrature modulator and adjusts the offsets of I and Q signals according to an offset adjustment value, wherein an origin offset of a modulation output signal by the quadrature modulator is adjusted. Origin offset measuring means to be measured, the offset voltage applied to the quadrature modulator is varied a plurality of times, the origin offset of the modulation output signal for each offset voltage is measured by the origin offset measuring means, and the adjustment calculated from the measured value An offset adjustment value determining unit that sets a value as an offset adjustment value; a storage unit that stores the offset adjustment value determined by the offset adjustment value determining unit; and a transmission unit that stores the offset adjustment value stored in the storage unit during transmission. Means for providing a differential encoder or quadrature modulator Offset adjusting apparatus characterized.