JP3837110B2 - Double balanced mixer carrier leak measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carrier of a double balanced mixer that measures carrier leakage contained in an output signal of a double balanced mixer that multiplies a carrier signal input to a local input terminal and an IF signal input to an IF input terminal. The present invention relates to a leak measurement apparatus.
[0002]
[Prior art]
In a double balanced mixer (hereinafter abbreviated as DBM) 1 (this structure is an example of a double balanced mixer) having the structure shown in FIG. 7B, FIG. As shown, the carrier signal c input to the local input terminal is multiplied by the IF signal b input to the IF input terminal, and the result is output as the output signal d.
[0003]
In this case, in the general DBM1, as shown in the phase vector diagram of FIG. 7C, in addition to the desired vector for the output signal d, the carrier signal c is output via this DBM1. The signal d includes a carrier leak that leaks. Thus, when carrier leak is included in the output signal d of the DBM1, a large spurious is generated in the output signals of various circuits such as a quadrature modulator and a signal processing device in which the DBM1 is incorporated. It becomes a factor.
[0004]
Therefore, it is important in terms of circuit design to measure and grasp the carrier leak magnitude L and phase θ in each DBM 1 incorporated in various circuits and signal processing devices in advance.
[0005]
Conventionally, using the network analyzer (NWA) 2 shown in FIG. 8A, the phase θ indicating the angle from the carrier leak magnitude L and the reference phase (phase of the carrier signal c) in the DBM 1 has been obtained. That is, the IF input terminal of the DBM 1 to be measured is terminated with the characteristic impedance 3 of the DBM 1, and the carrier signal c as a test signal whose phase, frequency, and amplitude are already known is received from the network analyzer (NWA) 2. The output signal d of the DBM 1 at that time was applied to the input terminal, and the magnitude and phase of the output signal d were measured.
[0006]
[Problems to be solved by the invention]
However, even when the network analyzer (NWA) 2 is incorporated in a carrier leak measuring apparatus for measuring carrier leak in the DBM 1, there are still the following problems to be solved.
[0007]
That is, some DBMs 1 have an operation specification that requires a carrier signal c having a signal level of a certain level or more to be input. In general, the signal level of the signal inputted to and outputted from the network analyzer (NWA) 2 is small to drive such a DBM, and the network analyzer (NWA) 2 has a high characteristic of the signal of this small signal level. It has a function to measure with accuracy. Therefore, as shown in FIG. 8B, it is necessary to interpose the amplifier 4 in the signal path of the carrier signal c.
[0008]
However, when the amplifier 4 is interposed in the signal path in this way, the influence of the amplification characteristic and phase characteristic of the amplifier 4 on the measurement result cannot be ignored. Therefore, the measurement and the calculation for obtaining the final carrier leak magnitude L and phase θ are performed. Processing becomes complicated.
[0009]
Furthermore, as shown in FIG. 9, when the DBM 1 to be measured is incorporated into one integrally formed quadrature modulator 7 such as an IC circuit together with the other DBM 5 and the adder 6, measurement is performed. Since the output signal of the target DBM 1 cannot be taken out alone, it was impossible to measure the carrier leak of the DBM 1 alone as a measurement target using the network analyzer (NWA) 2.
[0010]
In addition, the network analyzer (NWA) 2 has a function of measuring characteristics of a signal having a small signal level with high accuracy, and is therefore very expensive.
[0011]
The present invention has been made in view of such circumstances, and the DBM to be measured is incorporated in the quadrature modulator, and the output signal level of the entire quadrature modulator is controlled by a DC voltage applied to the IF input terminal of each DBM. By doing so, it is possible to measure the carrier leak of the DBM alone to be measured even if it is a DBM incorporated in a quadrature modulator without using a network analyzer (NWA). -It aims at providing the carrier leak measuring device of a mixer.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, in the carrier leak measurement device of the double balanced mixer (DBM) of the present invention, a pair of carrier signals whose phases are different from each other by 90 ° are generated and output to a pair of signal terminals, An orthogonal carrier signal generation / switching unit that switches the phase relationship of carrier signals output to a pair of signal terminals in response to a signal switching command, and a pair of DBMs for which at least one DBM (double balanced mixer) is a measurement target And an adder, each of the carrier signals output from the pair of signal terminals of the orthogonal carrier signal generation / switching unit is input to each DBM, and the modulation signal output from the orthogonal modulator A level measuring device for measuring a signal level, a voltage generator for generating a specified DC voltage to be applied to the IF input terminal of each DBM, and a quadrature carrier A signal switching command is sent to the signal generator / switching unit, and the pair of carrier signals input to the quadrature modulator are maintained in the first state, generated from the voltage generator, and each IF input of the pair of DBMs Means for obtaining a first pair of DC voltages that minimize the signal level measured by the level measuring device by inputting to the terminal, and sending a signal switching command to the quadrature carrier signal generating / switching unit for quadrature modulation Generated from the voltage generator and input to each IF input terminal of the pair of DBMs while the phase relationship of the pair of carrier signals input to the generator is switched from the first state and maintained in the second state. Means for obtaining a second pair of DC voltages that minimize the signal level measured by the level measuring device, the first pair of DC voltages, the second pair of DC voltages, and the conversion coefficient of each DBM. To each DBM Means for calculating the magnitude and phase of the carrier leak.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a double balanced mixer (DBM) carrier leak measuring apparatus according to an embodiment of the present invention will be described.
First, FIG. 1, FIG. 2, FIG. 3, FIG. 3, and FIG. 3, FIG. 3, FIG. 3, and FIG. 2, FIG. 2, FIG. 2, and FIG. 4 will be described.
[0014]
For example, as shown in FIG. 1, the signal levels of the I and Q signals applied to the IF input terminals of the respective DBMs 11 and 12 of the quadrature modulator 14 composed of the DBM 11 to be measured, the DBM 12 not to be measured and the adder 13 Is maintained at “0”, and the carrier signals c whose phases are orthogonal to each of the DBMs 11 and 12.₁, C₂Is applied. If each of the DBMs 11 and 12 is in a state where no carrier leak occurs, no signal is output from the adder 13.
[0015]
However, in general, as shown in FIG. 2, a carrier signal c input from the DBM 11 to the DBM 11₁Phase θ relative to the phase (I-phase axis)_ICarrier leak (size L)_I) Occurs, and the carrier signal c input to the DBM 12 from the DBM 12₂Phase θ with respect to the phase (Q phase axis)_QCarrier leak (size L)_Q) Occurs. Carrier leak (size L) of the entire quadrature modulator 14 output from the adder 13₀) Each carrier leak L_I, L_QIs a vector composition.
[0016]
From this quadrature modulator 14, carrier leak L₀Is not output, this carrier leak L₀It is only necessary to generate a voltage V for adjustment with a vector for canceling the signal at the output of the adder 13. In order to generate the voltage V for this adjustment, each carrier signal c is applied to the IF input terminals of the DBMs 11 and 12.₁, C₂DC voltage I projected on the input phase (phase axis) of_DC, Q_DCMay be applied.
[0017]
Here, the carrier leak L output from the quadrature modulator 14₀Since the signal level indicating the magnitude of the signal can be easily measured, the carrier leak L₀DC voltage I indicating the minimum signal level of_DC, Q_DCIs easy to find.
[0018]
As can be seen from FIG. 2, carrier leak L₀DC voltage I applied to cancel_DCEach carrier leak L_I, L_QIs input to the DBM 11 as a carrier signal c₁This value cancels the value obtained by adding the I-phase component projected onto the phase (I-phase axis). Carrier leak L₀DC voltage Q applied to cancel_DCEach carrier leak L_I, L_QIs input to the DBM 12 as a carrier signal c.₂This is a value that cancels the value obtained by adding the Q-phase components projected onto the phase (Q-phase axis).
[0019]
Therefore, the DC voltage I_DC, Q_DCAnd each carrier leak L_I, L_QMagnitude and phase θ_I, Θ_QRelationship is found.
[0020]
Next, the carrier signal c applied to each DBM 11 and 12₁, C₂To obtain each carrier leak L_I, L_QMagnitude and phase θ_I, Θ_QIs obtained.
[0021]
However, in each DBM 11, 12, the voltage input to the IF input terminal does not appear as it is at the output terminal, but a conversion coefficient K corresponding to each DBM 11, 12._I, K_QThe value multiplied by appears. Therefore, the aforementioned DC voltage I_DC, Q_DCMultiplied by the conversion coefficient K and each carrier leak L_I, L_QMagnitude and phase θ_I, Θ_QEach carrier leak L_I, L_QMagnitude and phase θ_I, Θ_QIs obtained.
[0022]
Furthermore, each carrier leak L_I, L_QMagnitude and phase θ_I, Θ_QA specific calculation procedure will be described with reference to FIG. 3 (state A) and FIG. 4 (state B).
[0023]
FIG. 3A shows a carrier signal c at the local input terminal of the DBM 11 in the quadrature modulator 14 in which the DBM 11 to be measured, the DBM 12 and the adder 13 shown in FIG.₁(= E cos (2πf_C)) Is applied, and the carrier signal c is applied to the local input terminal of the other DBM 12.₂(= E sin (2πf_C)) Is applied. Therefore, in this state A, each carrier signal c₁, C₂Are 90 ° out of phase with each other.
[0024]
Further, in this state A, the signal output from the adder 13 (carrier leak L₀) Signal level is minimized, that is, this signal (carrier leak L₀DC voltage I to the IF input terminals of the DBMs 11 and 12 in order to generate a voltage V for vector direction adjustment that cancels_A, Q_AIs applied.
[0025]
This pair of DC voltages I_A, Q_AA specific method for obtaining the combination of the DC voltages I applied to the IF input terminals of the DBMs 11 and 12 is as follows._D, Q_DThe DC voltage I that minimizes the output signal level of the adder 13 is sequentially changed._D, Q_DIt is sufficient to search for a combination of.
[0026]
In this state A, as shown in FIGS. 3B and 3C, the carrier signal c input from the DBM 11 to the DBM 11₁Phase θ relative to the phase (I-phase axis)_ICarrier leak L_IIs generated and the carrier signal c input to the DBM 12 from the DBM 12 is generated.₂Phase θ with respect to the phase (Q phase axis)_QCarrier leak L_QWill occur. Carrier leak L of the entire quadrature modulator 14 output from the adder 13₀Is each carrier leak L_I, L_QIs a vector composition.
[0027]
In FIG. 3B, this vector-synthesized carrier leak L₀Carrier signal c input to the DBM 11₁DC voltage I applied to the IF input terminal of the DBM 11 to cancel the phase axis (I phase axis) direction component of_ARF component RF appearing at the output end of DBM11_IAEach carrier leak L_I, L_QCarrier signal c input to the DBM 11₁Since this is a value that cancels out the sum of the phase (I-phase axis) direction components, it can be expressed by equation (1).
[0028]
RF_IA= [L_Icos (θ_I-L_Q sin (θ_Q]] ・ (−1)… (1)
Similarly, in FIG. 3C, this vector synthesized carrier leak L₀Carrier signal c input to the DBM 12₂DC voltage Q applied to the IF input terminal of the DBM 12 in order to cancel the phase (Q phase axis) direction component of_ARF component RF appearing at the output end of the DBM 12_QAEach carrier leak L_I, L_QCarrier signal c input to the DBM 12₂Since this is a value that cancels out the sum of the phase (Q phase axis) direction components, it can be expressed by equation (2).
[0029]
RF_QA= [L_Isin (θ_I) + L_Q cos (θ_Q]] ・ (−1)… (2)
_However,DC voltage I_A, I_BTwo carrier leaks L_I, L_QTherefore, two carrier leaks L can be calculated from the equations (1) and (2)._I, L_QCannot be obtained individually.
[0030]
Therefore, as shown in FIG. 4A, the carrier signal c input to each DBM 11 and 12 of the quadrature modulator 14.₁, C₂Replace. That is, the carrier signal c is applied to the local input terminal of the DBM 11 in the quadrature modulator 14.₂(= E sin (2πf_C)) Is applied, and the carrier signal c is applied to the RF input terminal of the other DBM 12.₁(= E cos (2πf_C)) Is applied to obtain a state B. Therefore, also in this state B, each carrier signal c₁, C₂Are 90 ° out of phase with each other.
[0031]
In this state B, the phase of the carrier signal input to each of the DBMs 11 and 12 is shifted by 90 ° compared to the state A.
[0032]
Therefore, in FIG. 4B, the vector-synthesized carrier leak L₀Carrier signal c input to the DBM 12₂DC voltage Q applied to the IF input terminal of DBM12 in order to cancel the phase (Q phase axis) direction component of_BRF component RF appearing at the output end of DBM 12 by_QBEach carrier leak L_I, L_QCarrier signal c input to the DBM 12₂Since this is a value that cancels out the sum of the phase (Q phase axis) direction components, it can be expressed by equation (3).
[0033]
RF_QB= [-L_Isin (θ_I) + L_Q cos (θ_Q]] ・ (−1)… (3)
Similarly, in FIG. 4C, this vector synthesized carrier leak L₀Carrier signal c input to the DBM 11₁DC voltage I applied to the IF input terminal of the DBM 11 in order to cancel the phase (I-phase axis) direction component of_BRF component RF appearing at the output end of DBM 11 by_IBEach carrier leak L_I, L_QCarrier signal c input to the DBM 11₁This is a value that cancels out the sum of the phase (I-phase axis) direction components, and can be expressed by equation (4).
[0034]
RF_IB= L_Icos (θ_I) + L_Q sin (θ_Q) …(Four)
As described above, in each DBM 11 and 12, the voltage input to the IF input terminal does not appear as an RF component at the output terminal as it is, but a value obtained by multiplying the conversion coefficient K corresponding to each DBM 11 and 12 is an RF component. Appears as The conversion coefficient of each DBM 11 and 12 is K_I, K_QThen, the relationship between each RF component and each DC voltage can be expressed by equations (5) to (8).
[0035]
RF_IA= K_I・ I_A                                      …(Five)
RF_QA= K_Q・ Q_A                                      … (6)
RF_IB= K_I・ I_B                                      … (7)
RF_QB= K_Q・ Q_B                                      … (8)
The above equations (5) to (8) are substituted into equations (1) to (4) to obtain the following equations (9) to (12).
[0036]
RF_IA= K_I・ I_A= [L_Icos (θ_I-L_Q sin (θ_Q]] ・ (－1)… (9)
RF_QA= K_Q・ Q_A= [L_Isin (θ_I) + L_Q cos (θ_Q]] ・ (−1)… (10)
RF_QB= K_Q・ Q_B= [-L_Isin (θ_I) + L_Q cos (θ_Q]] ・ (−1)… (11)
RF_IB= K_I・ I_B= [L_Icos (θ_I) + L_Q sin (θ_Q]] ・ (−1)… (12)
The equations (9) to (12) are modified to obtain the following equations (13) to (16).
[0037]
K_I・ I_A+ K_I・ I_B= 2L_Icos (θ_I) ・ (−1)… (13)
K_Q・ Q_A+ K_Q・ Q_B= 2L_Q cos (θ_Q) ・ (−1)… (14)
K_I・ I_A―K_I・ I_B= -2L_Q sin (θ_Q) ・ (−1)… (15)
K_Q・ Q_A―K_Q・ Q_B= 2L_Isin (θ_I) ・ (−1)… (16)
From the equations (13) and (16), the carrier leakage magnitude L of the DBM 11_IIs obtained by equation (17).
L_I= (1/2) [K_I ²(I_A+ I_B)²+ K_Q ²(Q_A―Q_B)²]^1/2… (17)
Further, from the equations (14) and (15), the carrier leak magnitude L of the DBM 12_QIs obtained by equation (18).
[0038]
L_Q= (1/2) [K_I ²(I_A―I_B)²+ K_Q ²(Q_A+ Q_B)²]^1/2… (18)
Further, from the equation (13), the carrier leak phase θ of the DBM 11_IIs obtained by equation (19).
[0039]
θ_I= ACOS [-K_I(I_A+ I_B) / (2L_I]] ... (19)
Similarly, from the equation (14), the phase θ of the carrier leak of the DBM 12_QIs obtained by equation (20).
[0040]
θ_Q= ACOS [-K_Q(Q_A+ Q_B) / (2L_Q]] ... (20)
Or the phase θ of the carrier leak of the DBM 11 from the equation (16)_IIs obtained by equation (21).
[0041]
θ_I= ASIN [-K_I(Q_A―Q_B) / (2L_I)] …(twenty one)
Similarly, from the equation (15), the phase θ of the carrier leak of the DBM 12_QIs obtained by equation (22).
[0042]
θ_Q= ASIN [-K_Q(I_A―I_B) / (-2L_Q)] …(twenty two)
As described above, the carrier leak L as the entire orthogonal transformer 14 output from the adder 13 of the orthogonal transformer 14.₀Combination of two DC voltages applied to the IF input terminals of the respective DBMs 11 and 12 (I_A, Q_A), (I_B, Q_B), And conversion coefficient K of each DBM 11 and 12_I, K_QIs obtained, the magnitude L of each carrier leak of each DBM 11 and 12 alone L_I, L_Q, And phase θ_I, Θ_QIs uniquely determined.
[0043]
Next, the conversion coefficient K of each DBM 11 and 12_I, K_QThe measurement method of will be described. This conversion factor K_I, K_QA plurality of measurement methods shown in the following (a), (b) and (c) can be considered.
[0044]
(A) Simple measurement
When accuracy is not required, a DC voltage is applied to the IF input terminal of one DBM 11 whose conversion coefficient K is to be measured, and the IF input terminal of the other DBM 12 is grounded. Then, from the relationship between the change amount of the DC voltage DC applied to the IF input terminal of one DBM 11 and the change amount of the signal level VL of the output signal output from the adder 13 of the orthogonal transformer 14 at this time, conversion is performed. The coefficient K is calculated.
[0045]
In this simple measurement, each carrier leak included in each DBM 11, 12 is included in the output signal output from the adder 13._I, K_QHigh measurement accuracy cannot be expected.
[0046]
(B) Regular measurement (1)
A DC voltage that minimizes the signal level of the output signal of the entire quadrature modulator output from the adder 13 is applied to the IF input terminal of the DBM 12 that is not the object of measurement. In this state, the rate of change in the signal level of the output signal of the quadrature modulator 14 when the DC voltage applied to the IF input terminal of the DBM 11 to be measured is changed is the conversion coefficient K of the DBM 11 to be measured._IAnd
[0047]
Specifically, the first voltage DC applied to the IF input terminal of the DBM 11 to be measured.₁The first output signal level VL of the quadrature modulator 14 with respect to₁And the second voltage DC applied to the IF input terminal of the DBM 11 to be measured₂The second output signal level VL of the quadrature modulator 14 with respect to₂And the conversion coefficient K_IIs obtained by equation (23).
[0048]
K_I= (VL₂―VL₁) / (DC₂―DC₁) …(twenty three)
In this way, since the DC voltage that minimizes the output signal level of the entire quadrature modulator is applied to the IF input terminal of the DBM 12 that is not the measurement target, the conversion coefficient K of the DBM 11 that is the measurement target._IIn the process of measuring, the influence of the carrier leak of the DBM 12 that is not the measurement target can be suppressed to the minimum. As a result, the measurement accuracy of the conversion coefficient K can be improved as compared with the simple measurement described above.
[0049]
(C) Regular measurement (2)
A pair of DC voltages I to be applied to the IF input terminals of the DBMs 11 and 12 at which the signal level of the output signal of the entire quadrature modulator 14 output from the adder 13 of the quadrature modulator 14 is minimized._A, Q_AAnd set each as a reference voltage. Next, the DC voltage I applied to the IF input terminal of the DBM 11 whose conversion coefficient K is to be measured._DIs the reference voltage I_AThe change rate of the output signal level of the quadrature modulator 14 when the value is changed from the conversion factor K of the DBM 11 to be measured._IAnd
[0050]
Since the conversion coefficient K is measured with the output signal level of the entire quadrature modulator 14 being minimized as described above, the carrier leaks of the DBMs 11 and 12 are almost included in the output signal output from the adder 13. Therefore, the measurement accuracy of the conversion coefficient K can be greatly improved.
[0051]
In this way, the conversion coefficient K of each DBM 11 and 12_I, K_QCan be measured with high accuracy, the magnitude of carrier leakage L of each DBM 11, 12 alone_I, L_Q, And phase θ_I, Θ_QCan be measured with high accuracy.
[0052]
Next, using the calculation procedure described above, the carrier leak magnitude L of each DBM 11 and 12 alone._I, L_Q, And phase θ_I, Θ_QA configuration of a carrier leak measuring apparatus of a double balanced mixer (DBM) that measures the above will be described with reference to FIG.
[0053]
In the carrier balance measuring apparatus of the double balanced mixer (DBM) shown in FIG. 5, the carrier signal generator 15 is activated in response to an activation command st from a controller 16 comprising a computer, and has a frequency f._CReference carrier signal c having₀(= E cos (2πf_C)) Is sent to the next orthogonal carrier signal generation / switching unit 17.
[0054]
In the orthogonal carrier signal generation / switching unit 17, a 90 ° phase shifter 18 and a signal switching unit 19 including a pair of switching switches 19a and 19b are provided. Reference carrier signal c input from carrier signal generator 15₀(= E cos (2πf_C)) Is a new carrier signal c as it is.₁(= E cos (2πf_C)) Is input to the common terminal C of one of the changeover switches 19a of the signal switching unit 19 and to the 90 ° phase shifter 18.
[0055]
The 90 ° phase shifter 18 receives the input reference carrier signal c.₀(= E cos (2πf_C)) Phase shifted by 90 ° to obtain a new carrier signal c₂(= E sin (2πf_C)), The signal is sent to the common terminal C of the other changeover switch 19b of the signal changeover unit 19.
[0056]
In the 90 ° phase shifter 18, the input reference carrier signal c₀That the phase of the phase is accurately shifted by 90 °. When the phase shift amount deviates from 90 °, the phase shift amount is determined by the adjustment command ve from the control unit 16. It is precisely adjusted to 90 °.
[0057]
The changeover terminal A of the changeover switch 19a and the changeover terminal B of the changeover switch 19b are connected to the signal terminal 20a. On the other hand, the changeover terminal A of the changeover switch 19b and the changeover terminal B of the changeover switch 19a are connected to the signal terminal 20b. The changeover switches 19a and 19b of the signal switching unit 19 are switched in accordance with a signal switching command se from the control unit 16 to switch the switching terminals A and B to which the common terminal C is connected.
[0058]
The signal terminal 20 a is connected to the local input terminal of one DBM 11 of the next quadrature modulator 14, and the signal terminal 20 b is connected to the local input terminal of the other DBM 12 of the next quadrature modulator 14.
[0059]
Therefore, when the control unit 16 is outputting the signal switching command se to the switching terminal A, the carrier signal c is transmitted from the signal terminal 20a.₁(= E cos (2πf_C)) Is input to one DBM 11 of the quadrature modulator 14, and the carrier signal c is supplied from the signal terminal 20b.₂(= E sin (2πf_C)) Is input to the other DBM 12 of the quadrature modulator 14. This state corresponds to [State A] shown in FIG.
[0060]
On the contrary, in the state where the control unit 16 outputs the signal switching command se to the switching terminal B, the carrier signal c is transmitted from the signal terminal 20a.₂(= E sin (2πf_C)) Is input to one DBM 11 of the quadrature modulator 14, and the carrier signal c is supplied from the signal terminal 20b.₁(= E cos (2πf_C)) Is input to the other DBM 12 of the quadrature modulator 14. This state corresponds to [State B] shown in FIG.
[0061]
In this way, the control unit 16 sends the signal switching command se to the signal switching unit 19 and a pair of carrier signals c whose phases input to the DBMs 11 and 12 of the quadrature modulator 14 are different from each other by 90 °.₁, C₂Can be switched to [State A] or [State B].
[0062]
The IF input terminal of one DBM 11 of the quadrature modulator 14 is connected to the DC voltage I from the voltage generator 21._DIs applied. The IF input terminal of the other DBM 12 is connected to the DC voltage Q from the voltage generator 22._DIs applied. DC voltage I output from each voltage generator 21, 22_D, Q_DIs specified from the control unit 16.
[0063]
The DBM 11 to be measured is a carrier signal c₁(Or c₂) And DC voltage I_DAre combined and sent to the adder 13. DBM12 is carrier signal c₂(Or c₁) And DC voltage Q_DAre combined and sent to the adder 13. The adder 13 adds the output signals of the DBMs 11 and 12 and outputs the result as a modulation signal. The level measuring device 23 measures the signal level VL of the modulation signal output from the quadrature modulator 14 and sends it to the control unit 16.
[0064]
A display 24 and an operation unit 25 are connected to the control unit 16 composed of a computer. In the control unit 16, a first DC voltage pair search unit 26, a second DC voltage pair search unit 27, a conversion coefficient calculation unit 28, and a carrier leak calculation unit 29 formed on the application program are provided. Is provided.
[0065]
Next, the carrier leak magnitude L of each DBM 11, 12 performed by each unit 26-29 of the control unit 16._I, L_Q, And phase θ_I, Θ_QEach processing operation up to the calculation of will be described with reference to the flowchart of FIG.
[0066]
When the measurer inputs a measurement start operation via the operation unit 25, an activation command st is sent to the carrier signal generation unit 15 to activate the carrier signal generation unit 15 (step S1).
[0067]
Next, the first DC voltage pair search unit 26 is activated, sends a signal switching command se to the signal switching unit 19, and switches the signal switching unit 19 to the [state A] side (S2). As a result, each DBM 11 and 12 of the quadrature modulator 14 receives each carrier signal c as shown in FIG.₁, C₂Is entered. Next, the DC voltage I applied to the IF input terminals of the DBMs 11 and 12 is controlled by controlling the voltage generators 21 and 22._D, Q_DIs once set to "0" (S3).
[0068]
The signal level VL of the modulation signal output from the quadrature modulator 14 in this state (carrier leak of the entire quadrature modulator 14) is detected via the level measuring device 23 (S4). The DC voltage I output from the voltage generators 21 and 22 is_D, Q_DDC voltage I that minimizes the signal level VL._A, Q_AIs obtained (S5).
[0069]
Next, the second DC voltage pair search unit 27 is activated, sends a signal switching command se to the signal switching unit 19, and switches the signal switching unit 19 to the [state B] side (S6). As a result, each of the DBMs 11 and 12 of the quadrature modulator 14 receives each carrier signal c as shown in FIG.₂, C₁Is entered. Next, the DC voltage I applied to the IF input terminals of the DBMs 11 and 12 is controlled by controlling the voltage generators 21 and 22._D, Q_DIs once set to "0" (S7).
[0070]
The signal level VL of the modulation signal (carrier leak of the entire quadrature modulator 14) output from the quadrature modulator 14 in this state is detected via the level measuring device 23 (S8). The DC voltage I output from the voltage generators 21 and 22 is_D, Q_DDC voltage I that minimizes the signal level VL._B, Q_BIs obtained (S9).
[0071]
Next, the conversion coefficient calculation unit 28 is activated to execute the conversion coefficient calculation process of (c) normal measurement (part 2) described above. That is, the signal switching unit 19 is switched to the [state A] side (S10). Then, each voltage generator 21, 22 is controlled to apply a DC voltage I applied to the IF input terminal of each DBM 11, 12._D, Q_DOnce, the DC voltage I at which the output signal level VL is minimized_A, Q_A(S11).
[0072]
DC voltage I on the DBM11 side_DThe amount of change in the output signal level VL when the value is changed is obtained (S12). This DC voltage I_DThe conversion coefficient K of the DBM 11 is calculated from the ratio between the change amount of the output signal level VL and the change amount of the output signal level VL._IIs calculated (S13).
[0073]
Next, the DC voltage I_D, Q_DDC voltage I that minimizes the output signal level VL_A, Q_A(Reference voltage) is set again, and the DC voltage Q on the DBM 12 side_DThe amount of change in the output signal level VL when the value is changed is obtained (S14). This DC voltage Q_DThe conversion coefficient K of the DBM 12 from the ratio of the change amount of the output signal level VL and the change amount of the output signal level VL_QIs calculated (S15).
[0074]
Next, the carrier leak calculation unit 29 is activated, and the previously obtained DC voltage I that minimizes the output signal level VL in [state A] is obtained._A, Q_ADC voltage I that minimizes the output signal level VL in [state B]_B, Q_BAnd the conversion coefficient K of each DBM 11 and 12_I, K_QFrom the above formulas (17), (18), (19), and (20), the size L of the carrier leak of each DBM 11 and 12 alone is calculated._I, L_Q, And phase θ_I, Θ_QIs calculated (S16).
[0075]
L_I= (1/2) [K_I ²(I_A+ I_B)²+ K_Q ²(Q_A―Q_B)²]^1/2… (17)
L_Q= (1/2) [K_I ²(I_A―I_B)²+ K_Q ²(Q_A+ Q_B)²]^1/2… (18)
θ_I= ACOS [-K_I(I_A+ I_B) / (2L_I]] ... (19)
θ_Q= ACOS [-K_Q(Q_A+ Q_B) / (2L_Q]] ... (20)
And the calculated magnitude L of each carrier leak_I, L_Q, And phase θ_I, Θ_QIs displayed on the display 24 (S17).
[0076]
In the carrier leak measurement device of the double balanced mixer (DBM) configured as described above, the signal level of the carrier leak of the entire quadrature modulator output from the quadrature modulator 14 can be measured by a simple level meter 23. DC voltage applied to the IF input terminals of the DBMs 11 and 12 (I_A, Q_A), (I_B, Q_B) Can also be realized by simple voltage generators 21 and 22. Therefore, the size L of the carrier leak of each DBM 11 and 12 without incorporating an expensive network analyzer (NWA) 2_I, L_Q, And phase θ_I, Θ_QCan be measured.
[0077]
Even if the DBM 11 to be measured is incorporated in the quadrature modulator 14 as one IC circuit element, the magnitude L of the carrier leak of the DBM 11 alone to be measured_IAnd phase θ_ICan be measured with high accuracy.
[0078]
Of course, both DBMs 11 and 12 incorporated in the quadrature modulator 14 can be designated as the DBM to be measured.
[0079]
【The invention's effect】
As described above, in the carrier leak measuring apparatus of the double balanced mixer (DBM) of the present invention, the DBM to be measured is incorporated in the quadrature modulator, and the output signal level of the entire quadrature modulator becomes the minimum value. In this way, the combination of DC voltages applied to the IF input terminals of each DBM is set, and the magnitude and phase of the carrier leak of each DBM are calculated using the relationship between this combination of DC voltages and the carrier leak of each DBM. Yes.
[0080]
Accordingly, without incorporating a network analyzer (NWA), even if the DBM is incorporated in the quadrature modulator, the carrier leak of the DBM alone to be measured can be measured with high accuracy, even if the DBM is incorporated in the quadrature modulator.
[Brief description of the drawings]
FIG. 1 is a diagram showing a quadrature modulator used in a carrier leak measuring apparatus for a double balanced mixer according to an embodiment of the present invention.
FIG. 2 is a diagram showing a measurement principle of a carrier leak measurement device for a double balanced mixer according to the embodiment;
FIG. 3 is a view for explaining a state A in the carrier leak measurement device for a double balanced mixer according to the embodiment;
FIG. 4 is a view for explaining a state B in the carrier leak measurement apparatus for a double balanced mixer according to the embodiment;
FIG. 5 is a block diagram showing a schematic configuration of a carrier leak measuring apparatus for a double balanced mixer according to the embodiment;
FIG. 6 is a flowchart showing a measurement operation of the carrier leak measurement device of the double balanced mixer according to the embodiment;
FIG. 7 is a diagram for explaining carrier leakage
FIG. 8 is a diagram showing a carrier leak measurement method using a conventional network analyzer.
FIG. 9 is a diagram showing a schematic configuration of a general quadrature modulator.
[Explanation of symbols]
1, 5, 11, 12, ... DBM
2 ... Network analyzer
6, 13 ... Adder
7, 14 ... Quadrature modulator
15 ... Carrier signal generator
16 ... Control unit
17 ... Orthogonal carrier signal generation / switching unit
18 ... 90 ° phase shift
19 ... Signal switching part
20a, 20b ... signal terminals
21, 22 ... Voltage generator
23 ... Level measuring section
24 ... Display
25. Operation unit
26: First DC voltage pair search unit
27: Second DC voltage pair search unit
28: Conversion coefficient calculation unit
29 ... Carrier leak calculation unit

Claims (1)

A pair of carrier signals whose phases are 90 ° different from each other are generated and output to the pair of signal terminals (20a, 20b), and the phase relationship of the carrier signals output to the pair of signal terminals is switched according to a signal switching command. Orthogonal carrier signal generation / switching unit (17),
At least one DBM (double balanced mixer) is composed of a pair of DBMs (11, 12) to be measured and an adder (13), and is output from a pair of signal terminals of the orthogonal carrier signal generation / switching unit. A quadrature modulator (14) in which each carrier signal is input to each DBM;
A level measuring device (23) for measuring the signal level of the modulated signal output from the quadrature modulator;
A voltage generator (21, 22) for generating a specified DC voltage to be applied to the IF input terminal of each DBM;
A signal switching command is sent to the quadrature carrier signal generation / switching unit, and the pair of carrier signals input to the quadrature modulator are maintained in the first state, and are generated from the voltage generator, Means (26) for obtaining a first pair of DC voltages that minimize the signal level measured by the level measuring device by inputting to each IF input terminal of the DBM;
In a state where a signal switching command is sent to the quadrature carrier signal generation / switching unit and the phase relationship between a pair of carrier signals input to the quadrature modulator is switched from the first state and maintained in the second state, Means (27) for determining a second pair of DC voltages that are generated from the voltage generator and input to the IF input terminals of the pair of DBMs, so that the signal level measured by the level measuring device is minimized. When,
Means (29) for calculating the magnitude and phase of the carrier leak of each DBM from the first pair of DC voltages, the second pair of DC voltages, and the conversion coefficient of each DBM. A carrier leak measurement device for a double balanced mixer.

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