antenna-pnf 0.1.0

Planar Near-Field Antenna Measurement Functions

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 3.6+
• 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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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")

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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