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Nexxim Simulator >
Nexxim Time-Varying Noise Analysis >
Running TV Noise Analyses from the Netlist Editor >
TV Noise Netlist Syntax

TV Noise Netlist Syntax

The syntax of the .TV_NOISE statement in Nexxim is:

.TV_NOISE
+ output_freq_sweep
+ SS_ANALYSIS=HB|OSC
+ SS_TONES=[val [,val]...]
+ SS_MAXK=[val [,val]...]
+ [RELHARMVEC=[val [,val]...]]
+ [IPROBE=device_name]
+ [OPROBE=device_name]
+ [NOISE_OUTPUT=[nets_currents]
+ [INPUT_REFERRED_NOISE=[nets_currents]]]
+ [REFSIDEBAND=[val [,val]...]]
+ [SAVEALLSIDEBANDS=NO|YES]
+ [METHOD=HB|SHOOTING]
+ [AUTO_REFINE_SOLUTION=YES|NO]
+ [TRIM_TOL=val]

In this syntax:

• For clarity, elements are shown one per line using the continuation character (+). Elements can be entered on a single line using spaces as separators.

• Brackets shown in bold ([ ]) are required when more than one item is specified.

• Brackets in plain font ([ ]) denote optional entries or fields.

Output Frequency Sweep

The required entry output_freq_sweep specifies a range of output frequencies to apply in the noise calculation. The sweep specification should be the first field in the TV_NOISE statement (after the .TV_NOISE keyword).

(Refer to the TV Noise Technical Notes topic for information on the use of the swept output frequencies.)

The output_freq_sweep field has several formats.

The sweep can be just a single frequency value.

A second form of output_freq_sweep specifies the starting and ending frequencies, and the incremental step:

[START=]start_val [STOP=]stop_val [STEP=]step_val

If the sweep specification omits the START=, STOP=, and STEP= labels, the start value, stop value and step value must be entered in the order shown. If the labels are used, the values may be entered in any order, but then all three values must have labels.

A third format for output_freq_sweep is:

count_type numpoints startfreq stopfreq

The count_type entry (LIN, DEC, or OCT) specifies a pattern of frequencies to be swept with numpoints, startfreq and stopfreq:

The LIN (linear) count type specifies a linear sweep at numpoints different frequencies from the frequency given by startfreq to the frequency given by stopfreq. The spacing between test frequencies is (stopfreq − startfreq) / numpoints.

The DEC (decade) count type specifies a logarithmic sweep at numpoints different frequencies in each decade (10× multiple of startfreq) from startfreq to stopfreq. The spacing between test frequencies is logarithmic within decades.

The OCT (octave) count type specifies a logarithmic sweep at numpoints different frequencies in each octave (2× multiple of startfreq) from startfreq to stopfreq. The spacing between test frequencies is logarithmic within octaves.

A fourth format for output_freq_sweep is:

POI numpoints freq1 [freq2 ...]

The POI format specifies a space-separated list of individual frequency points. The entry numpoints is the number of frequency points in the list.

SS_ANALYSIS

The SS_ANALYSIS entry selects between harmonic balance (HB) and oscillator analysis (OSC) to compute the steady-state values. HB is the default.

SS_TONES

The SS_TONES entry specifies one or more frequencies to use in the steady-state harmonic balance calculations.

SS_MAXK

The SS_MAXK entry specifies the maximum harmonic numbers to use for the corresponding SS_TONES frequencies in the steady-state harmonic balance calculations. The number of SS_MAXK entries should be the same as the number of SS_TONES frequencies.

RELHARMVEC

The RELHARMVEC entry specifies offset multipliers for the corresponding SS_TONES frequencies. The number of RELHARMVEC entries should be the same as the number of SS_TONES frequencies.

Note

When just one offset is specified, the netlist can use the entry RELHARMNUM instead of RELHARMVEC, and can omit the brackets around the offset value.

Refer to the TV Noise Technical Notes topic for information on the use of the RELHARMVEC offsets.

IPROBE

The IPROBE entry specifies the input RF device to use for the small-signal input to the circuit.

The device can be a port, a current source, or a voltage source.

When a port is specified as the input device, Nexxim computes the noise figure and the conversion gain. Gain for a port is in units of Volts, in the sense of available power.

Note

The definition of the port in the netlist uses the Port Impedance Resistor syntax. If the port definition includes the noise parameters NOISE and NOISETEMP, the analysis will use the temperature value specified. If these parameters are not in the definition, Nexxim will add thermal noise to the specified port for computing the noise factor and conversion gain with the formula 4KT/R, where K is Boltzmann’s constant, R is the port impedance, and T is the noise temperature, using 290° Kelvin for T.

For current and voltage source input devices, only the gain is computed. The input units are Amperes and Volts, respectively.

If IPROBE is not specified, only the Onoise figure is calculated.

OPROBE

The OPROBE entry specifies the device to use for the small-signal output from the circuit.

The device can be a port, a current source, a voltage source, a resistor, or a current probe.

Note

The definition of the port in the netlist uses the Port Impedance Resistor syntax. The port definition can include noise parameters NOISE and NOISETEMP, but the analysis will ignore the noise data for the output port.

When a port, current source, or resistor is specified as the OPROBE device, the output units are in Volts. When a voltage source or current probe is specified, the units are in Amperes.

REFSIDEBAND

The REFSIDEBAND entry specifies coefficients to apply to the SS_TONES frequencies in the calculation of the RF/input frequency. The REFSIDEBAND coefficients are positive or negative integers plus zero. See the TV Noise Technical Notes topic for more information on the use of the REFSIDEBAND coefficients.

Note

When an IPROBE device is specified, the netlist must also have the REFSIDEBAND list of coefficients for the SS_TONES frequencies in order to perform the conversion gain calculation. When no IPROBE device is specified, the REFSIDEBAND entry is optional; the default coefficient value is 1.

NOISE_OUTPUT

The NOISE_OUTPUT entry is a comma-separated list of node voltages and branch currents for which noise output is desired, in addition to the noise data calculated for the IPORT and OPORT devices. (No noise factor or conversion gain is computed for these additional outputs.

Voltage outputs are specified using the format:

V(net1,net2)

Noise output for nets has units V²/Hz.

Branch currents are specified using the format:

I(device)

Noise output for branch currents has units A²/Hz.

See TV Noise Results for details on the outputs from TV Noise analysis.

INPUT_REFERRED_NOISE

The INPUT_REFERRED_NOISE entry specifies a single node voltage or branch or current to be used as the source for an input-referred noise calculation.

A node voltage is specified using the format:

V(net1,net2)

A branch current is specified using the format:

I(device)

The INPUT_REFERRED_NOISE entry can be specified only when the NOISE_OUTPUT entry is also specified.

Harmonic Balance Controls

When SS_ANALYSIS=HB is specified, the additional controls METHOD, AUTO_REFINE_SOLUTION, and TRIM_TOL can be used.

See Handling Strongly Nonlinear Circuits in the Harmonic Balance topic for details on the METHOD entry in the HB statement.

See Increasing Accuracy or Speed for details on the AUTO_REFINE_SOLUTION and TRIM_TOL entries in the HB statement.

TV Noise Netlist Example

.TV_NOISE

+ START=1000000000 STOP=2000000000 STEP=500000000

+ OPROBE=[Z167]

+ SS_MAXK=[7]

+ SS_TONES=[1000000000]

+ SS_ANALYSIS=HB

+ NOISE_OUTPUT=[V(IF),I(LO)]

+ INPUT_REFERRED_NOISE=[RIF]

+ REFSIDEBAND=[1]

+ SAVEALLSIDEBANDS=no

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