Delivering useful transmit power at V-band frequencies – the 50 to 75 GHz range – is among the most demanding engineering challenges in commercial and defence millimeter wave hardware. Unlike amplification at X-band or even Ka-band, V-band solid-state power amplification pushes transistor device technology close to its practical limits: the frequencies involved approach the ft and fmax of all but the most advanced compound semiconductor processes, and the wavelengths are short enough that even minute impedance variations cause significant, measurable performance degradation. A 0.1 mm length difference in a matching stub at 60 GHz produces a phase error that can reduce amplifier gain by several dB – tolerances that demand both precision fabrication and careful characterisation at the device and module level.

This article examines how V-band power amplification works at the circuit and system levels, what device technologies make it practical, and what performance parameters engineers must evaluate when selecting a V-band power amplifier for radar, communications, or electronic warfare applications.

Why V-Band Power Amplification Is Different

At 60 GHz, the free-space wavelength is 5 mm. A quarter-wavelength matching stub on a standard microstrip substrate is approximately 1.0 to 1.25 mm long – dimensions where fabrication tolerances of ±10 µm produce meaningful electrical performance variation. Small physical dimensions make every element of the MMIC design sensitive to process variation in a way that lower-frequency circuits are not. The transistor parasitic elements that are negligible at 10 GHz – drain-source capacitance, gate resistance, substrate coupling – have reactances at 60 GHz comparable to the device’s intrinsic impedances, and must be accounted for in full electromagnetic simulation rather than simple equivalent circuit models.

At the same time, the market demand for V-band components has grown substantially over the past decade, driven by 60 GHz unlicensed wireless communications (IEEE 802.11ad/ay), V-band point-to-point backhaul links, and millimeter wave radar development. This demand has accelerated the maturity of V-band GaAs and GaN MMIC processes, making high-performance V-band power amplifiers available as catalog components from specialist millimeter wave manufacturers – where previously they were exclusively custom defence procurements.

How a V Band Power Amplifier Works

Device Technology: GaAs pHEMT and GaN HEMT

A V band power amplifier is built around compound semiconductor transistors – either GaAs pseudomorphic HEMT (pHEMT) or GaN HEMT on SiC substrate – fabricated on gate lengths of 0.07 to 0.1 µm to achieve the transit frequencies needed for meaningful gain at 50 to 75 GHz. GaAs pHEMT processes at these gate lengths deliver ft values above 200 GHz and fmax values above 400 GHz, providing 8 to 14 dB of gain per stage at V-band. GaN on SiC offers lower absolute gain per stage but significantly higher breakdown voltage – exceeding 40 V drain-source – enabling power densities of 3 to 5 W/mm that GaAs cannot approach. For applications requiring output powers above +27 dBm at V-band, GaN is the enabling technology.

Mi-Wave designs V-band power amplifiers using both device technologies, selecting GaAs pHEMT for moderate-power, efficiency-sensitive applications and GaN HEMT for the highest output power requirements. The choice between them involves a trade-off: GaN offers more power per unit die area but historically higher process variability at V-band frequencies, while GaAs offers more mature V-band MMIC foundry processes with tighter electrical performance distributions.

Multi-Stage Architecture and Interstage Matching

A single transistor stage at V-band cannot deliver more than 100 to 200 mW of useful output power on GaAs, or 300 to 500 mW on GaN, before device geometry constraints become limiting. To reach the output powers required for point-to-point communications transmitters, radar front-ends, or EW jamming systems, multiple transistor stages are cascaded, with each stage’s output matched to the next stage’s optimum source impedance. Interstage matching networks at V-band are entirely distributed – implemented as combinations of microstrip lines, series stubs, and shunt stubs fabricated directly on the MMIC die – and must simultaneously satisfy gain, bandwidth, and stability requirements across the full operating frequency range.

The final stage of a V-band power amplifier – the stage that drives the output port – typically consists of multiple transistor cells connected in parallel, with their outputs combined through on-chip Wilkinson divider-combiner networks. Each additional parallel cell adds output power but also adds loss in the combining network; the combining efficiency determines how much of the summed cell power reaches the module output port. At V-band, achieving combining efficiencies above 85% requires careful layout to ensure electrical path length equality between all parallel branches.

Power-Added Efficiency

Power-added efficiency (PAE) measures how effectively the amplifier converts DC supply power into useful RF output power, accounting for the RF power already present at the input. At V-band, achieving high PAE requires operating transistors in Class AB or Class B bias, which reduces quiescent current relative to Class A but introduces some gain compression and harmonic generation. State-of-the-art GaN V-band power amplifiers have demonstrated PAE values of 20 to 35% at peak output power – a significant improvement over GaAs designs at the same frequency, which typically achieve 10 to 18%. Higher PAE directly reduces thermal dissipation, extending device lifetime and reducing the complexity of thermal management at the module and system level.

Key Performance Parameters for System Selection

Output Power and P1dB

For radar and communication transmitters, the output 1 dB compression point (OP1dB) defines the maximum useful transmit power before signal distortion becomes significant. Mi-Wave’s V-band power amplifier products offer OP1dB values across a range from +20 dBm to +33 dBm depending on device technology, die size, and combining architecture. For FMCW radar transmitters requiring spectral purity across the full chirp bandwidth, the operating point is typically set 3 to 5 dB below OP1dB to ensure linear operation with adequate headroom for waveform amplitude variations.

Gain and Gain Flatness

A V-band power amplifier typically provides 20 to 30 dB of small-signal gain across its operating bandwidth. Gain flatness – the peak-to-peak variation in gain across the operating frequency range – directly determines whether the transmitter requires external equalisation to flatten its output power spectrum. Mi-Wave characterises gain flatness for its V-band amplifier products across the full specified bandwidth, providing the measurement data engineers need to assess whether system-level equalisation is required or whether the amplifier’s native flatness is sufficient for the application.

Harmonic and Spurious Output

V-band transmitters generate second harmonics at W-band frequencies (100 to 150 GHz range) that can interfere with co-located W-band receiver systems. Spurious output specifications – requiring all out-of-band products to remain below -40 to -50 dBc – must be verified across the full operating power range, because harmonic levels rise with output power and increase sharply near P1dB. Mi-Wave’s millimeter wave amplifiers are characterised for harmonic and spurious output content to support system-level electromagnetic compatibility analysis, ensuring that co-site interference budgets can be calculated accurately before integration.

V Band Power Amplifier Applications

60 GHz Wireless Communications

The IEEE 802.11ad and 802.11ay standards exploit the V-band’s 9 GHz of unlicensed spectrum around 60 GHz to support multi-gigabit short-range wireless links for data centre interconnect, high-definition wireless video, and point-to-point consumer applications. V-band power amplifiers in these systems must deliver sufficient transmit EIRP to close links across distances of 5 to 20 metres indoors while meeting regulatory spectral emission masks and operating within strict power consumption envelopes for battery-powered and passively cooled implementations.

Point-to-Point Backhaul

V-band fixed point-to-point wireless links operating in the licensed 57 to 71 GHz band deliver multi-gigabit capacity for small cell backhaul and enterprise connectivity. Atmospheric oxygen absorption near 60 GHz – approximately 15 dB/km – limits practical link distances to 100 to 500 metres, but within that range these systems offer fibre-equivalent capacity without the civil engineering cost of cable installation. V-band power amplifiers for backhaul applications must meet stringent regulatory transmit power and spectral mask requirements while delivering sufficient output power to close the link budget with adequate margin for rain and multipath fading.

Radar and Electronic Warfare

V-band radar systems – including imaging radar for security screening, level measurement radar for industrial applications, and emerging automotive radar development platforms – require power amplifiers that maintain linear operation across the full chirp bandwidth. Mi-Wave supports V-band radar development with power amplifier components characterised for output power, gain flatness, and harmonic content at the operating conditions relevant to FMCW and pulsed radar waveforms. V-band EW jamming transmitters represent the most demanding application, requiring flat gain across the full 50 to 75 GHz range combined with high output power and fast frequency switching – performance that drives selection of GaN technology with broadband distributed matching architectures.

Thermal and Mechanical Integration

V-band GaN power amplifiers dissipate significant heat in very small die areas. A GaN stage delivering +30 dBm (1 W) of RF output at 25% PAE dissipates 3 W of waste heat in a die that may measure 2 × 3 mm. Silicon carbide’s high thermal conductivity (approximately 400 W/m·K) conducts heat away from the transistor junction more effectively than GaAs substrates, but the die must still be mounted with controlled solder thickness onto a thermally conductive carrier to achieve the junction-to-case thermal resistance needed to keep transistor junctions within their rated temperature limits.

Mi-Wave packages its V-band power amplifier modules with waveguide output interfaces for high-power configurations, because waveguide connections offer lower insertion loss than coaxial connections at these frequencies and provide reliable power handling for output powers above +25 dBm. Coaxial (2.4 mm or 1.85 mm connector) interfaces are used for moderate-power configurations where the convenience of coaxial connectivity outweighs the modest additional insertion loss.

Conclusion

The V band power amplifier is the transmit chain component that ultimately sets the EIRP, range, and waveform integrity of any V-band system. Its design sits at the intersection of advanced device physics, precision MMIC fabrication, and demanding thermal engineering – making it one of the most technically sophisticated millimeter wave components in current production.

Understanding the gain, P1dB, efficiency, and harmonic performance of a V-band power amplifier – and how those parameters interact with the transmit waveform, system power budget, and thermal envelope of the application – is the foundation for correct component specification and successful system integration.

Mi-Wave continues to develop and supply V-band power amplifier solutions for customers across 60 GHz communications, backhaul, radar, and defence applications, with a product range that spans from catalog components for standard system designs to fully custom amplifier modules optimised for specific frequency allocations, output power levels, and operating environments. Engineers working on V-band system development are encouraged to contact Mi-Wave’s engineering team for product recommendations and application support.