Component - Mixer V1.60 Datasheet.pdf

PSoC® Creator™ Component Data Sheet
Mixer
1.60
Features
•
Single-ended mixer
•
Continuous time up mixing:
•
•
Input frequencies up to 500 kHz
•
Sample clock up to 1 MHz
Discrete time, sample & hold down mixing:
•
Input frequencies up to 14 MHz
•
Sample clock up to 4 MHz
•
Adjustable power settings
•
Selectable reference voltage
General Description
The Mixer component provides a single-ended modulator. The Mixer component can be used for
frequency conversion of an input signal using a fixed Local Oscillator (LO) signal as the sampling
clock. The manipulations of signal frequencies performed by a mixer can be used to move
signals between frequency bands or to encode and decode signals. A Mixer can be used to
convert signal power at one frequency into power at another frequency to make signal
processing easier, typically shifting higher frequencies to base-band. The mixer output is best
used by filtering the desired signal harmonics using an off-chip filter or the output can be used to
drive an on-chip ADC through internal routing. The component offers two configurations:
•
Up mixer, continuous time balance mixer, operates as a switching multiplier
•
Down mixer, discrete time, sample and hold mixer
The component accepts as inputs two signals at different frequencies and presents at the output
a mixture of signals at multiple frequencies, including the sum and difference of the input signal
and the local oscillator signal. Typically, the undesired frequency components in the output
signal are removed by filtering. A few examples illustrate the operation of the mixer in different
modes.
Up Mixer:
LO frequency greater than signal frequency
Shown with 100 kHz sine wave input , modulated by a 1.0 MHz Local Oscillator
Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600
Document Number: 001-65738 Rev. **
Revised December 13, 2010
Mixer
PSoC® Creator™ Component Data Sheet
Input Signal
Carrierl
Output
0
10
20
usec 30
40
The Up mixer is a multiplier. For signal frequency at fSIG and clock at fLO it generates a modulated
signal that is the product of the input and the LO. Since the LO is a square wave, with all of its
expected harmonics, the output has the form
f MOD (t ) = sin( 2pf SIG )
f MOD (t ) =
1
sin( 2pf LO t )
n = odd n
å
1
å [cos(2p (nf LO - f SIG )) - cos(2p (nf LO + f SIG ))]
2
In this case the intended output is at fLO+fSIG and fLO-fSIG, as shown in the FFT below.
0
-20
Input
Output
Series3
-40
-60
-80
0
1
2
3
4
5
6
7
8
If a specific sideband, e.g., fLO+fSIG, is required, the unwanted sideband can be filtered out with
active RC filters using the on-board opamps or with the Filter component after digitizing the
Mixer output waveform.
Up Mixer:
LO frequency less than signal frequency
Shown with input frequency of 455 kHz and LO of 430 kHz to yield a nominal output at 25 kHz.
The underlying sine wave at 25 kHz is apparent, but not obvious because the sum of 455 and
430 kHz appears at the same level.
Page 2 of 15
Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Mixer
Input Signal
Carrierl
Output
0
20
40
60
usec
80
100
The FFT for these waveforms clearly shows the input at 455 kHz, the output difference
frequency at the intended 25 kHz and the sum output of the signal and first LO harmonic at 885
kHz. Just below the first harmonic's sum output is a term at 3*fLO-fSIG or 835 kHz. The pattern
repeats with the term at 5* fLO-fSIG just below 3*fLO+fSIG. The miscellaneous "stuff" between these
well known spectral lines is a function of the FFT, the windowing calculation process, and the
sin(x)/x nature of the sampling process. The look of these signals may change depending on the
type of spectrum analyzer used (swept spectrum vs FFT).
0
-10
-20
Input
LO
Output
-30
-40
-50
-60
-70
-80
0
0.2
Down Mixer:
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
LO near fSIGNAL
When the LO frequency is near the signal frequency, a sampling mixer offers advantages over a
multiplying mixer. The time domain plot shows less higher-frequency content for harmonics of
the mixer. The steps at the sampling rate of the LO are readily apparent. The LO can be either
above or below the signal frequency, but the frequency distribution for LO > fSIG will be inverted
compared to the frequency distribution for LO < fSIG.
Document Number: 001-65738 Rev. **
Page 3 of 15
Mixer
PSoC® Creator™ Component Data Sheet
5
4
3
2
1
Input
Carrier
0
Out put
-1
-2
-3
-4
0
20
40
60
80
100
The mixing products are sin(x)/x related, so that when the sampling frequency (LO) is close to
the signal frequency, 'x' is close to p and these terms are quite different from the 1/n harmonic
characteristic of the multiplying mixer. The harmonic content generated is substantially lower,
which means that higher order terms are more easily filtered and eliminated.
The difference frequency between the signal and LO shows clearly in the FFT. Mix products near
the signal frequency are somewhat higher than the multiplying mixer, but all higher order
harmonic terms are substantially.
0
-10
-20
-30
-40
-50
Input
-60
Carrier
Output
-70
-80
0.0
0.5
1.0
1.5
2.0
When the LO frequency is above fSIG/2 or below fSIG*1.5, substantial mix products appear and
the mixer loses its utility, it hardly separates the desired difference frequency from the mix
products.
Page 4 of 15
Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Down Mixer:
Mixer
LO frequency less than fSIGNAL/2
This is referred to as a sub-sampling mixer. When the LO frequency is less than half of the signal
frequency, the primary output is at fSIG-n*fLO where 'n' is the largest integer such that n*fLO is less
than fSIG. The waveforms for fSIG = 455 kHz and fLO = 143.3 kHz (=430 kHz/3) show that the
primary output frequency is 25 kHz. The waveform is "coarser" than one with a higher frequency
LO, but the output frequency is the same as if the signal was sampled at a higher rate.
5
4
3
2
1
Input
Carrier
0
Out put
-1
-2
-3
-4
0
20
40
60
80
100
The advantage of the sub-sampling mixer is in the range of the allowed input signal frequency. It
is common to sub-sample by a factor of 4, so that a 13.57 MHz can be sampled at 3.2 MHz to
yield a primary output frequency of 770 kHz.
0
-10
-20
-30
-40
-50
Input
-60
Carrier
Output
-70
-80
0.0
0.5
1.0
1.5
2.0
Over sampling mixers (e.g., fSIG = 455 kHz and LO = 820 kHz result in mixer products similar to
those of the multiplying mixer. These products may be more difficult to filter out of the desired
waveform.
Document Number: 001-65738 Rev. **
Page 5 of 15
Mixer
PSoC® Creator™ Component Data Sheet
Input/Output Connections
This section describes the input and output connections for the Mixer component. An asterisk (*)
in the list of I/Os indicates that the I/O may be hidden on the symbol under the conditions listed
in the description of that I/O.
Fin – Analog
Fin is the input signal terminal. The Fin signal is mixed with the local oscillator clock signal to
generate the Fout signal. Fin frequency is limited as follows:
•
Multiply (Up) Mixer
Fin < 500 kHz
•
Sample (Down) Mixer
Fin < 14 MHz
LO – Digital
LO is the local oscillator signal terminal. This signal serves as the sampling clock for the mixer.
The LO signal is mixed with the Fin signal to generate the Fout signal. For the Multiply Mixer
mode, the LO clock signal must have a duty cycle of 50%.
LO frequency is limited as follows:
•
Multiply (Up) Mixer
LO < 1 MHz
•
Sample (Down) Mixer
LO < 4 MHz
Vref – Analog
Vref is the input terminal for a reference voltage. The reference voltage may be one of the PSoC
internal reference sources, an internal VDAC value, or an external signal.
Fout – Analog
Fout is the output signal terminal. The Fout signal is the resultant signal of the mixing operation of
the Fin and LO signals.
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Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Mixer
Component Parameters
Drag a Mixer component onto your design and double-click it to open the Configure dialog.
Figure 1: Configure Mixer Dialog
Mixer_Type
This parameter determines the configured mode of the mixer SC/CT block. The component
supports two mixer modes: Multiply (Up) Mixer and Sample (Down) Mixer.
LO_Source
The Mixer may be connected to a clock source external to the component (External) or may
configure its own clock (Internal). If the LO is External, it is the user’s responsibility to supply a
50% duty cycle for UP Mixers (DOWN Mixers do not have this requirement). If the LO is Internal
then the component derives the desired clock frequency with a 50% duty cycle for to UP Mixers.
This impacts the clock divider calculation. When changing a Mixer from Up to Down, or vice
versa, it may be necessary to change the clock parameters to maintain proper operation of the
Mixer in the Up mode.
LO_Frequency
This parameter sets the clock frequency when LO_Source is internal. In the UP mode, the
terminating resistances in the mixer have values that are switched depending on operating
frequency in order to optimize performance. Lower LO_Frequency values allow using higher
internal resistance values resulting in slightly better modulator performance.
Document Number: 001-65738 Rev. **
Page 7 of 15
Mixer
PSoC® Creator™ Component Data Sheet
When LO Source is set to External LO, the users sets the frequency in his external clock
(whether clock resource or digital block source).
Power
This sets the initial drive power of the mixer. The power determines the speed with which the
mixer reacts to changes in the input signal. There are four power settings; Minimum, Low,
Medium (default), and High. A Low Power setting results in the slowest response time and a
High Power setting results in the fastest response time.
Placement
There are no placement specific options.
Resources
API Memory
(Bytes)
Digital Blocks
Analog Blocks
Datapaths
Macro
cells
Status
Registers
Control
Registers
Counter7
Flash
RAM
Pins (per
External I/O)
1 Fixed SC/CT
block
N/A
N/A
N/A
N/A
N/A
297
2
4
The mixer uses one SC/CT block.
Application Programming Interface
Application Programming Interface (API) routines allow you to configure the component using
software. The following table lists each routine and provides a brief functional description. The
subsequent sections cover each function in more detail.
By default, PSoC Creator assigns the instance name "Mixer_1" to the first instance of the
component in a given design. You can rename it to any unique value that follows the syntactic
rules for identifiers. The instance name becomes the prefix of every global function name,
variable, and constant symbol associated with the component. For readability, the instance name
used in the following table is "Mixer".
Function
Description
void Mixer_Start(void)
Power up the Mixer.
void Mixer_Stop(void)
Power down the Mixer.
void Mixer_SetPower(uint8 power)
Set drive power to one of four levels.
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Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Mixer
Function
Description
void Mixer_Sleep(void)
Stops and saves the user configuration.
void Mixer_Wakeup(void)
Restores and enables the user configuration.
void Mixer_Init(void)
Initializes or restores default Mixer configuration.
void Mixer_Enable(void)
Enables the Mixer.
void Mixer_SaveConfig(void)
Empty function. Provided for future usage.
void Mixer_RestoreConfig(void)
Empty function. Provided for future usage.
Global Variables
Variable
Mixer_initVar
Description
Indicates whether the Mixer has been initialized. The variable is initialized to 0 and set to 1 the
first time Mixer_Start() is called. This allows the component to restart without reinitialization after
the first call to the Mixer_Start() routine.
If reinitialization of the component is required, then the Mixer_Init() function can be called before
the Mixer_Start() or Mixer_Enable() function.
void Mixer_Start(void)
Description:
Performs all of the required initialization for the component and enables power to the block.
The first time the routine is executed, the input and feedback resistance values are
configured for the operating mode selected in the design. When called to restart the mixer
following a Mixer_Stop() call, the current component parameter settings are retained.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_Stop(void)
Description:
Turns off the Mixer block.
Parameters:
None
Return Value:
None
Side Effects:
Does not affect mixer type or power settings
Document Number: 001-65738 Rev. **
Page 9 of 15
Mixer
PSoC® Creator™ Component Data Sheet
void Mixer_SetPower(uint8 power)
Description:
Sets the drive power to one of four settings; minimum, low, medium, or high.
Parameters:
(uint8) power: See the following table for valid power settings.
Power Setting
Notes
Mixer_MINPOWER
Lowest active power and slowest reaction time.
Mixer_LOWPOWER
Low power and speed.
Mixer_MEDPOWER
Medium power and speed.
Mixer_HIGHPOWER
Highest active power and fastest reaction time.
Return Value:
None
Side Effects:
None
void Mixer_Sleep(void)
Description:
This is the preferred API to prepare the component for sleep. The Mixer_Sleep() API saves
the current component state. Then it calls the Mixer_Stop() function and calls
Mixer_SaveConfig() to save the hardware configuration.
Call the Mixer_Sleep() function before calling the CyPmSleep() or the CyPmHibernate()
function. Refer to the PSoC Creator System Reference Guide for more information about
power management functions.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_Wakeup(void)
Description:
This is the preferred API to restore the component to the state when Mixer_Sleep() was
called. The Mixer_Wakeup() function calls the Mixer_RestoreConfig() function to restore the
configuration. If the component was enabled before the Mixer_Sleep() function was called,
the Mixer_Wakeup() function will also re-enable the component.
Parameters:
None
Return Value:
None
Side Effects:
Calling the Mixer_Wakeup() function without first calling the Mixer_Sleep() or
Mixer_SaveConfig() function may produce unexpected behavior.
Page 10 of 15
Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Mixer
void Mixer_Init(void)
Description:
Initializes or restores the component according to the customizer Configure dialog settings. It
is not necessary to call Mixer_Init() because the Mixer_Start() API calls this function and is
the preferred method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
All registers will be set to values according to the customizer Configure dialog.
void Mixer_Enable(void)
Description:
Activates the hardware and begins component operation. It is not necessary to call
Mixer_Enable() because the Mixer_Start() API calls this function, which is the preferred
method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_SaveConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_RestoreConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
Sample Firmware Source Code
PSoC Creator provides numerous example projects that include schematics and example code
in the Find Example Project dialog. For component-specific examples, open the dialog from the
Component Catalog or an instance of the component in a schematic. For general examples,
open the dialog from the Start Page or File menu. As needed, use the Filter Options in the
dialog to narrow the list of projects available to select.
Document Number: 001-65738 Rev. **
Page 11 of 15
Mixer
PSoC® Creator™ Component Data Sheet
Refer to the "Find Example Project" topic in the PSoC Creator Help for more information.
Functional Description
Mixer functionality is implemented using the PSoC SC/CT block. The discrete time down mixer is
implemented using the switched capacitor mode. The multiplying (up) mixer uses the continuous
time block mode.
Discrete Time Down Mixer
The schematic for the internal configuration of the discrete time mixer is shown in the following
figure:
Figure 2 Discrete Time Sample & Hold Mixer Schematic
The non-return-to-zero sample and hold is achieved by switching the integrating capacitor
between two capacitors. In Figure 2 above, either C1 or C4 can always be sampling the input
signal while the other is being integrated across the amplifier. The Fin signal is sampled at a rate
less than the Fin signal frequency. The mixer component is configured such that Fout is
integrated with a new value on the rising edge of the input clock.
For LO sample clock frequencies greater than half of the Fin signal frequency, the output is the
difference between the input and LO frequencies plus aliasing components. When the sample
clock frequency is less than half of the Fin signal frequency, the output is the difference between
the input and the largest integer multiple of the LO frequency that is less than the Fin signal
frequency.
For a given input carrier frequency, Fin, a sample LO clock frequency, Fclk, can be chosen to
provide the desired output frequency, Fout, for the system.
Page 12 of 15
Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
Mixer
Provided that Fclk is less than 4MHz, and Fin is less than 14MHz:
If
If
2N - 1
Fclk < Fin < N × Fclk ,
2
2N + 1
N × Fclk < Fin <
Fclk ,
2
then
Fout = N × Fclk - Fin
Equation 1
then
Fout = Fin - N × Fclk
Equation 2
Equation 1 and Equation 2 can be summarized as:
Fout = abs ( N * Fclk - Fin )
Equation 3
Continuous Time Up Mixer
The schematic for the internal configuration of the continuous time mixer is shown below:
Figure 3: Continuous Time Mixer Configuration Schematic
In this mode the op-amp is configured as a PGA that uses the LO input signal to toggle between
an inverting PGA gain of 1 and a non-inverting unity gain buffer. The output signal includes
frequency components at Fclk ± Fin plus terms at odd harmonics of the LO frequency plus and
minus the input signal frequency: 3*Fclk ± Fin, 5*Fclk ± Fin, 7*Fclk ± Fin etc.
Fout = N * Fclk ± Fin
with N holding odd values
Equation 4
Frequency Planning
Note that proper frequency planning is required to achieve the desired Fout. The clocks must be
carefully controlled in the design wide resources.
Document Number: 001-65738 Rev. **
Page 13 of 15
Mixer
PSoC® Creator™ Component Data Sheet
DC and AC Electrical Characteristics
The following values are indicative of expected performance and based on initial characterization
data. Unless otherwise specified in the tables below, all TA = 25°C, Vdd = 5.0 V, Power HIGH,
Opamp bias LOW, output referenced to 1.024 V.
Mixer DC Specifications
Parameter
VOS
Description
Conditions
Min
Typ
Max
Units
Input offset voltage
–
–
10
mV
Quiescent current
–
0.9
2
mA
Mixer AC Specifications
Parameter
Description
Conditions
Min
Typ
Max
Units
fLO
Local oscillator frequency
Down mixer mode
–
–
4
MHz
fin
Input signal frequency
Down mixer mode
–
–
14
MHz
fLO
Local oscillator frequency
Up mixer mode
–
–
1
MHz
fin
Input signal frequency
Up mixer mode
–
–
1
MHz
SR
Slew rate
–
–
–
V/µs
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.60
Description of Changes
Reason for Changes / Impact
Removed VDDA parameter from
component customizer
VDDA setting in the component is redundant and
unnecessary for multiple components. The parameter was
removed and the component queries the global setting for
minimum VDDA in the DWR and automatically enables the
pump when necessary.
Added a GUI Configuration Editor
Previous configuration window did not provide enough
information for ease of use.
LO - local oscillator is enabled correctly
The local oscillator was not being enabled correctly in
previous versions of the component.
Added characterization data to
datasheet
Minor datasheet edits and updates
Page 14 of 15
Document Number: 001-65738 Rev. **
PSoC® Creator™ Component Data Sheet
1.50
Mixer
Added Sleep/Wakeup and Init/Enable
APIs.
To support low power modes, as well as to provide
common interfaces to separate control of initialization and
enabling of most components.
Updated Symbol and Configure dialog.
To comply with corporate standards.
© Cypress Semiconductor Corporation, 2009-2010. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the
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specified above is prohibited without the express written permission of Cypress.
Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein.
Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in lifesupport systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application
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Use may be limited by and subject to the applicable Cypress software license agreement.
Document Number: 001-65738 Rev. **
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