antenna-pnf

A Python utility module for planar near-field (PNF) antenna measurement calculations. It provides helper methods to determine key measurement parameters such as separation distance, sampling spacing, scan length, and angle of view, based on IEEE standards.

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Requirements

• Python 3.8+
• No third-party dependencies (uses the standard library math module only)

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Installation

pip install antenna-pnf

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Usage

import antenna_pnf as pnf

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API Reference

All methods are static and accessible directly on the antenna-pnf class without instantiation.

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seperation_distance(frequency, coeff)

Computes an arbitrary separation distance as a multiple of the wavelength.

Parameter	Type	Unit	Description
frequency	float	Hz	Frequency of interest
coeff	float	—	Wavelength multiplier coefficient

Returns: float — separation distance in meters [m]

Formula:

$$R_{nf} = k \times \lambda = k \times c_0 / f$$

d = pnf.seperation_distance(10e9, 10)  # 10 wavelengths at 10 GHz

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min_seperation_distance(frequency, three_lambda=False)

Returns the minimum recommended separation distance between the antenna under test (AUT) and the probe, per IEEE 1720-2012 Section 5.3.1.4.

Parameter	Type	Unit	Description
frequency	float	Hz	Frequency of interest
three_lambda	bool	—	Use 3λ criterion instead of the default 5λ

Returns: float — minimum separation distance in meters [m]

Formula:

$$R_{nf} = 5 \times \lambda = 5 \times c_0 / f$$

Note: The standard recommends choosing between 3λ and 5λ. The default (5λ) is used to ensure sufficient decoupling between the AUT and the probe. Set three_lambda=True to use the relaxed 3λ criterion.

d_min = pnf.min_seperation_distance(10e9)           # 5λ (default)
d_min = pnf.min_seperation_distance(10e9, three_lambda=True)  # 3λ

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angle_of_view(a, d, L)

Computes the reliable far-field angle-of-view achievable from a planar near-field scan, per IEEE 149-2021 Eq. 99 and IEEE 1720-2012 Eq. 27.

Parameter	Type	Unit	Description
a	float	m	Antenna cross-section length
d	float	m	Separation distance between AUT and probe
L	float	m	Scan region length

Returns: float — angle of view in degrees [deg]

Raises: ValueError — if L <= a (scan length must exceed antenna size)

Formula:

$$\theta = \arctan\left(\frac{L - a}{2d}\right)$$

Note: The scan region is assumed to be centered on the AUT.

theta = pnf.angle_of_view(a=0.3, d=0.15, L=1.2)

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sampling_spacing(frequency)

Returns the maximum allowable sampling interval (grid spacing) for a near-field scan, per IEEE 149-2021 and IEEE 1720-2012 Eq. 25.

Parameter	Type	Unit	Description
frequency	float	Hz	Frequency of interest

Returns: float — maximum sampling spacing in meters [m]

Formula:

$$\Delta = \lambda / 2 = 0.5 \times c_0 / f$$

delta = pnf.sampling_spacing(10e9)

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scan_length(a, d, theta)

Computes the required scan length to achieve a desired angle-of-view, per IEEE 149-2021 Eq. 99 and IEEE 1720-2012 Eq. 27.

Parameter	Type	Unit	Description
a	float	m	Antenna cross-section length
d	float	m	Separation distance between AUT and probe
theta	float	deg	Desired pattern view angle (one side)

Returns: float — required scan length in the same unit as inputs [m]

Formula:

$$L = 2d \cdot \tan\theta + a$$

Note: The scan region is assumed to be centered on the AUT.

L = pnf.scan_length(a=0.3, d=0.15, theta=45.0)

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sampling_parameters_for_length(frequency, L)

Computes the sampling parameters (start position, stop position, count, and spacing) for a planar near-field scan based on the desired minimum scan length.

Parameter	Type	Unit	Description
frequency	float	Hz	Frequency of interest
L	float	m	Desired minimum scan length

Returns: tuple — (Lm, Lp, N, Delta) where Lm is sampling start position in meters [m], Lp is sampling stop position in meters [m], N is sampling count, Delta is spatial sampling length in millimeters [mm]

Note: The scan region is assumed to be centered on the AUT. The sampling spacing is floored to the nearest millimeter, and the scan length is adjusted to ensure proper sampling.

Lm, Lp, N, Delta = pnf.sampling_parameters_for_length(10e9, 1.2)

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sampling_parameters_for_angle(frequency, a, d, theta)

Computes the sampling parameters (start position, stop position, count, and spacing) for a planar near-field scan to achieve a desired angle-of-view.

Parameter	Type	Unit	Description
frequency	float	Hz	Frequency of interest
a	float	m	Antenna cross-section length
d	float	m	Separation distance between AUT and probe
theta	float	deg	Desired pattern view angle (one side)

Returns: tuple — (Lm, Lp, N, Delta) where Lm is sampling start position in meters [m], Lp is sampling stop position in meters [m], N is sampling count, Delta is spatial sampling length in millimeters [mm]

Note: The scan region is assumed to be centered on the AUT. This function first computes the required scan length using scan_length, then determines the sampling parameters.

Lm, Lp, N, Delta = pnf.sampling_parameters_for_angle(10e9, 0.3, 0.15, 45.0)

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Usage Example

from antenna-pnf import antenna-pnf

frequency = 10e9  # 10 GHz

# Minimum separation distance (5 wavelengths)
d = pnf.min_seperation_distance(frequency)
print(f"Min separation distance : {d*100:.2f} cm")

# Maximum sampling spacing
delta = pnf.sampling_spacing(frequency)
print(f"Max sampling spacing    : {delta*1000:.2f} mm")

# Required scan length for ±45° angle-of-view with a 30 cm antenna
antenna_size = 0.30  # m
L = pnf.scan_length(a=antenna_size, d=d, theta=45.0)
print(f"Required scan length    : {L:.4f} m")

# Achieved angle-of-view
theta = pnf.angle_of_view(a=antenna_size, d=d, L=L)
print(f"Angle of view           : {theta:.2f} deg")

# Sampling parameters for a desired scan length
Lm, Lp, N, Delta = pnf.sampling_parameters_for_length(9.5e9, 8.730)
print(f"Sampling start position : {Lm:.3f} m")
print(f"Sampling stop position  : {Lp:.3f} m")
print(f"Sampling count          : {N}")
print(f"Sampling spacing        : {Delta} mm")

# Sampling parameters for a desired angle-of-view
Lm, Lp, N, Delta = pnf.sampling_parameters_for_angle(9.5e9, 0.5, 0.15, 60.0)
print(f"Sampling start position : {Lm:.3f} m")
print(f"Sampling stop position  : {Lp:.3f} m")
print(f"Sampling count          : {N}")
print(f"Sampling spacing        : {Delta} mm")

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Standards References

Standard	Title
IEEE 149-2021	Recommended Practice for Antenna Measurements
IEEE 1720-2012	Recommended Practice for Near-Field Antenna Measurements

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Constants

Symbol	Value	Description
C0	299 792 458 m/s	Speed of light in vacuum